Pediatric Hip Disorders

Chen, Bochang

doi:10.1007/978-981-15-9331-4_6

Bochang Chen²

632 Accesses

Abstract

Developmental dysplasia of the hip (DDH), one of the common birth defects, is the condition that hip joint abnormalities at birth progress gradually during the growth, which ranges from mild, spontaneously resolving instability in the newborn to complete dislocation with secondary acetabular and proximal femoral deformity.

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Developmental Dysplasia of the Hip

Developmental Hip Dysplasia

The Deformed Hip

6.1 Developmental Dysplasia of the Hip

Developmental dysplasia of the hip (DDH), one of the common birth defects, is the condition that hip joint abnormalities at birth progress gradually during the growth, which ranges from mild, spontaneously resolving instability in the newborn to complete dislocation with secondary acetabular and proximal femoral deformity.

The occurrence of DDH varies by the age of initial consultation, which, for instance, is as high as 3–5% in the newborn or infants because the instability of the hip joint in this age group is also defined as DDH. With the growth and development of the joint, most hips become normal and stable gradually. In China, the diagnosis is made mainly by pelvic radiographic examination. Among infants aged 6 months who are screened with physical examinations and radiographs, the occurrence is 0.1%. The condition is considered to be a multifactorial disease with a female predominance. High incidence was noticed among children who live in an area with a cold climate, which is associated with tight swaddling.

6.1.1 Pathology

The pathological changes of DDH are complicated, which include soft tissue and bony structure abnormalities. Some of the changes are birth defects or primary lesion, and the others are secondary changes that are presented during growth or brought by treatments. Understanding the pathology lays the foundation for treating the condition properly and effectively. In this section, pathological changes of the hip joint in patients aged 2–6 years old are mainly discussed.

6.1.1.1 Soft Tissue Abnormalities

Immature hip joint, which is still growing and developing, has more soft tissue components. Types of tissue and structures are involved in the condition, and the extent of lesions varies greatly for different individuals.

6.1.1.1.1 Acetabulum

Labrum, transverse acetabular ligament, ligamentum teres, and hip capsule are usually involved. Patho-anatomy of labrum of the affected hip joint is closely associated with the position of the femoral head. If the head is in the acetabulum, a circular indentation would be made on the head by labrum; if the joint is dislocated, the labrum is usually inverted and may obstruct concentric reduction. Transverse acetabular ligament is a structure located in the inferior medial portion of the acetabulum that can increase the stability of the joint. It will be hypertrophic and may impede reduction when the hip remains dislocated.

6.1.1.1.2 Ligamentum Teres

This structure can not only prevent dislocation of the femoral head, but also serve as, at an early age, blood supply of the femoral head. Elongation and incrassation of the ligament are the adaptation of dislocation of the joint which can pull the head more tightly. However, at the same time, it will block reduction for the enlarged ligament lie at the bottom of the acetabulum. In some cases, ligamentum teres would rupture, and the stump will be absorbed. The blockage could also be noticed in these cases.

6.1.1.1.3 Hip Joint Capsule

Abnormalities of the joint capsule are also closely related to the extent of dislocation. In cases with complete dislocation, indentation of the capsule may produce the so-called hour-glass capsular deformity. And the constriction is between the true acetabulum and secondary acetabulum. This deformity could also make the reduction difficult.

6.1.1.1.4 Iliopsoas

The insertion of iliopsoas is on the lesser trochanter. The muscles span the hip anteriorly and will experience contracture. It prevents the joint from reduced. Furthermore, tight iliopsoas is responsible for hour-glass capsular deformity.

6.1.1.1.5 Muscles Around the Hip Joint

Around the dislocated hip joint, shortening of the hip abductors, gluteus medius, as well as gluteus minimus, contributes to the maintenance of the displacement.

6.1.1.2 Bony Structure Abnormalities

6.1.1.2.1 Femoral Head

When the hip becomes subluxated or dislocated, eccentric pressure upon the head leads to segmental flattening and uneven growth. The tight fit between femoral head and acetabulum is lost. A secondary acetabulum develops: with subluxation this forms in the anterosuperior part of the roof of the true acetabulum; with dislocation, it develops in the iliac wing above the true acetabulum.

6.1.1.2.2 Acetabulum

The acetabulum becomes shallow. Chondrocytes on the acetabular lunate surface, lacking the normal stimulus of a spherical contained femoral head, fails to develop normally. Bone ridge could appear in the cotyloid fossa. Usually, incongruent joint can also lead to apparent acetabular anteversion.

6.1.1.2.3 Proximal Femur

Femoral anteversion and neck-shaft angle will increase.

6.1.2 Classification

Based on different diagnostic methods, there are various classification systems of the condition. Graf’s classification with the severity of DDH quantified by ultrasonography is mainly used in the neonatal hip [1]. While for patients older than 6 months, the condition is usually evaluated through radiographic examination. Positive results can be divided into dislocation, subluxation, and hip dysplasia according to the relative position of the femoral head center on pelvic AP view. Hilgenreiner line joins the top aspect of the triradiate cartilages, which is used to measure the acetabular angle and as a reference for the Perkin line. Perkin line is perpendicular to the Hilgenreiner line, touching the lateral margin of the acetabulum. This leads to four quadrants and for a dislocated joint, the femoral head is located in the superolateral quadrant; for a subluxated joint, inferolateral; and when the femoral head locates in inferomedial quadrant with acetabular index more than 25 degrees, the situation is called hip dysplasia [2].

Tönnis classification, which is widely used nowadays, was raised by Tönnis D., a German physician, in 1978 and 1982. He analyzed the study of comparing various classification systems conducted by the Commission for the Study of Hip Dysplasia of the German Society for Orthopedics and Traumatology. Based on the principles of simpleness and practicableness, Tönnis described the classification system that has been accepted worldwide. It relies on the location of the femoral head ossification center and the hip joints can be grouped into 4 grades (Fig. 6.1). Grade 1: the center is located medial to Perkin line; grade 2: the center lies laterally to Perkin line but inferiorly to the level of highest point of acetabulum; grade 3: the center is just at the level of highest point of acetabulum; and grade 4: the center is above the level of upper border of acetabulum.

6.1.3 Clinical Manifestations

6.1.3.1 Symptoms

Patients in non-walking age have different symptoms from those in walking age. Children with DDH present a few symptoms before walking independently. On the other hand, multiple symptoms can be noticed when patients are in walking age. Furthermore, the problem can be easily neglected when the condition is not severe and bilateral hip joints are involved for symmetry symptoms could be neglected easily as well. Walking instability and limping are the main symptoms of this condition. Before the age of 8 years, pain could seldom be main complaint because of low body weight.

6.1.3.2 Signs

Main positive clinical signs include limping, lower limb discrepancy, and limited abduction of the hip joint.

1.
Limping is often presented, and the extents vary greatly. Usually, acetabular dysplasia would not lead to limping. Bilateral involvement causes a waddling gait, which is also called Trendelenburg gait, with a bilateral lurch.
2.
Lower limb discrepancy is a common clinical sign with asymmetry thigh or groin crease. Leg shortening of the affected side can be detected by physical examination with hip and knee 90-degree flexed, and one knee appears lower than the other.
3.
The abduction of the affected hip joint is limited. More abduction can be obtained with hip flexed using traction. Furthermore, if the joint is reduced, a clunk or “click” can be palpated, which is defined as positive abduction test.

In older children, in addition to the signs mentioned above, Trendelenburg sign could be positive.

6.1.4 Imaging Examinations

6.1.4.1 X-Ray

6.1.4.1.1 Pelvic Radiograph and Measurements

This is a routine diagnostic examination, which can provide clues to definite diagnosis and help to judge the severity of the condition (Fig. 6.2).

6.1.4.1.2 Perkin Quadrants

Perkin line is perpendicular to Hilgenreiner line, touching the lateral margin of the acetabulum. This leads to four quadrants, and a normal femoral head has to be located in the inferomedial quadrant. For a dislocated joint, the femoral head is located in the superolateral quadrant; for a subluxated joint, it is inferolateral one.

6.1.4.1.3 Acetabular Index

The acetabular index (AI) is formed between Hilgenreiner line and the acetabular roof, which measures the acetabular roof slope and evaluates the acetabular coverage. It is the most useful measure of acetabular dysplasia until 6 years of age. In newborns, values of 26 ° ± 5 ° in males and 30 ° ± 4 ° in females are considered normal. Because of further growth and development, gradually, this angle becomes smaller. If the patient is older than 2 years with AI more than 25 °, the diagnosis can be made.

6.1.4.1.4 Shenton Line

Shenton line is a continuous arc drawn from the inner edge of the femoral neck to the superior margin of the obturator foramen. This should be smooth and undisrupted; otherwise, it may indicate DDH, which is used to evaluate the severity of the condition.

6.1.4.2 Computed Tomography

Due to radiation concerns, it is less commonly used in children. Computed Tomography (CT) is considered, however, prior to surgical intervention, especially osteotomies, which can reveal more details about bone structure abnormalities. CT can also be used to obtain an accurate measurement of the femoral version and torsion, and acquire close observation of the acetabular morphology, which can assist pelvic or proximal femoral osteotomy. Direct demonstration of the morphology of the hip joint could be achieved through three-dimensional model reconstruction.

6.1.4.3 Magnetic Resonance Imaging

Many pathological conditions of DDH are detected early by Magnetic Resonance Imaging (MRI) due to its high soft-tissue resolution and sensitivity. Because an immature hip joint has more soft tissue components, MRI is commonly used to detect soft tissue changes in DDH, such as the morphology and position of the labrum, the relationship between femoral head and acetabulum, and the enlargement of the ligamentum teres. The outcomes of conservative treatment could be also evaluated by MRI.

6.1.5 Treatment

“Early detection and intervention” is the primary goal of DDH management. It has been widely accepted that successful conservative treatment in the early stage is much more meaningful and help to improve the outcomes of the patients than any salvage procedure performed in the late stage of the condition. With hip joint ultrasound neonatal screening being carried out extensively, the diagnosis can be made as early as during the first few days after birth. Pavlik harness, abduction brace, closed reduction with cast fixation are the main method for early-diagnosed DDH, which could be immediately initiated when the condition is ascertained. Because of great growth potential and mild secondary pathological changes, through timely conservative treatment, an improved prognosis can be expected in most of the early-diagnosed cases. Residual deformities and treatment failure could only be seen in a few patients. Avascular necrosis (AVN), which is idiopathic or iatrogenic, could occur during the treatment.

This section focuses on discussing surgical interventions for DDH. According to the habits of the surgeon and the different indications, there are various types of operations primarily for children older than 18 months who present residual deformity and receive treatment proved later to be a failure.

6.1.5.1 Tenotomy of the Adductors

6.1.5.1.1 Clinical Applications

This is the basic operation for DDH, which is commonly used in the treatment of a dislocated hip joint. It can remove the blockage due to the contracture of adductors during the reduction. The intra-articular pressure after reduction can also be lowered by this operation, which can prevent iatrogenic AVN.

6.1.5.1.2 Indications

The operation could be performed in the following circumstances: cases of dislocation or subluxation before receiving closed reduction; cases of hip dysplasia; high tension on the adductors can be palpated by holding the flexed hip in abduction.

6.1.5.1.3 Surgical Techniques

Under general anesthesia, with the patient in a supine position, the surgical area is disinfected and draped. The assistant holds the knee of the affected side and maintains the hip abduction and knee flexion, making the adductor muscle, which is contractural or tense palpable under the skin. A 2-cm straight incision is made along the adductors from the origin. Blunt dissect subcutaneous tissue. Dissect the deep fascia and make a horizontal incision. Cut open the deep fascia to expose the muscles by blunt dissection. The anterior branch of obturator nerve under the adductor longus should be protected. The origin of the adductor longus should be severed, and after that, hemostasis should be performed strictly. Close the wound in layers to the skin.

6.1.5.2 Open Reduction

6.1.5.2.1 Indications

Open reduction is necessary when closed reduction has failed in children younger than 18 months. When there is a defined obstruction, which is considered as the cause of reduction failures, such as an elongated ligamentum teres, an inverted limbus, and joint capsule, or an encroaching transverse acetabular ligament, surgical reduction and joint debridement are mandatory.

6.1.5.2.2 Position

The children are in a supine position with the pelvis on the affected side raised. After general anesthesia, the surgical area is disinfected and draped.

6.1.5.2.3 Surgical Techniques

1.
A Smith-Petersen approach is used to expose the joint. Blunt dissect subcutaneous tissue. The space between sartorius and tensor fasciae latae is developed, and the deep fascia underneath is cut open. The straight and reflected heads of rectus femoris are divided and reflected distally, exposing the superior and anterior hip capsule. The psoas tendon within the iliacus at the pelvic brim is identified, rolled forward, and divided to provide muscle lengthening without loss of continuity.
2.
An arc incision is made on the hip capsule. The capsulotomy should skirt the capsular attachment to the pelvis (usually 1 cm to the attachment). Then, the joint fluid runs out. Hip dislocation is accomplished by externally rotating the leg in order to expose the acetabulum. Use hemostatic forceps to expose and separate the ligamentum teres, which is usually excised as it is hypertrophic, leaving a 0.5-cm stump on the femoral head.
3.
The acetabulum should be palpated to ensure that no other obstacle prevents reduction. Residual ligamentum teres and pulvinar should be excised completely. The transverse ligament, which blocks reduction inferiorly, should be severed or excised.
4.
Reduce the femoral head. Make sure the position of “best fit” is achieved. Capsulorrhaphy is performed by excising the redundant capsule superiorly or by reefing the capsular margins (Fig. 6.3).
5.
Rectus femoris is reattached. Close the space between sartorius and tensor fasciae latae. The wound was closed in layers.
6.
The hip is maintained in a hip spica in sufficient flexion, abduction, and internal rotation for the head to be fully contained by the acetabulum but avoiding extreme positioning.

6.1.5.3 Salter’s Osteotomy

6.1.5.3.1 Clinical Application

Salter’s osteotomy is one of the most commonly used surgical procedures for DDH. By transecting the ilium at the level of the anterior inferior spine, above the ilium acetabulum, the procedure allows the distal pelvic fragment and acetabulum to rotate forward, downward, and laterally. The Axis of rotation passes through symphysis pubis. Better coverage can be achieved by this osteotomy.

6.1.5.3.2 Indications

The indications include patients aged over 18 months, acetabular index over 25 degrees, and femoral head that could be in the acetabulum or not. Contraindication is that the patient is too young with body weight below 10 kg and the iliac wing is too thin to endure the procedure.

6.1.5.3.3 Position

The children are in a supine position with the pelvis on the affected side raised.

6.1.5.3.4 Incision

Smith-Petersen approach (anterolateral approach).

6.1.5.3.5 Surgical Techniques

1.
Smith-Petersen approach was made to expose the joint. Blunt dissect subcutaneous tissue. The space between sartorius and tensor fasciae latae is developed, and the deep fascia underneath is cut open. The straight and reflected heads of rectus femoris are severed and reflected distally, exposing the lateral hip capsule. Then, expose the medial portion along the surface of the capsule.
2.
Pull the tensor fascia latae backward and cut open periosteum of the ilium upward along the lateral margin of the iliac wing and the lateral margin of the obliquus externus abdominis until the anterior 1/3 of the ilium. The periosteum was divided toward the sciatic notch using periosteum elevator. The iliac apophysis is separated bluntly (it is actually an epiphyseal fracture; and it is split, and the split halves are elevated subperiosteally from the iliac wing, in continuity with the gluteal muscles externally and the iliac muscles medially.). Pull sartorius apart to expose the psoas tendon.
3.
The psoas tendon should be severed intramuscularly by rolling it at the level of the pelvic brim as distally as possible. Peel the periosteum of the inner surface of the ilium. A curved introducer passed through the sciatic notch allows the Gigli saw to be introduced subperiosteally through the notch.
4.
Perform the acetabular debridement. An arc incision is made on the hip capsule (5–8 mm to the attachment). A T-shaped incision is added in the lateral hip capsule. Use hemostatic forceps to expose and separate the ligamentum teres. Pulvinar should be excised completely. The transverse ligament, which blocks reduction inferiorly, should be severed or excised. Observe the labrum. If a limbus is present and inverted, it may be made more pliant by making one or two radial cuts, allowing it to be everted over the femoral head. Reduce the femoral head and make sure the femoral head has a tight contact with the acetabulum. Evaluate the femoral anteversion. Capsulorrhaphy is performed by excising the redundant capsule superiorly or by reefing the capsular margins.
5.
As for the dislocated joint, the medial portion of the capsule couldn’t be closed completely with the residual capsule. After other portions being sutured, the medial capsule could remain vacant, which can be repaired by scar formation.
6.
A wedge of bone taken from the anterior superior iliac spine is trimmed and fashioned to fit into the triangular gap so created.
7.
Perform osteotomy. Place a Hohmann retractor under the sciatic notch to protect the structure below and to make enough room for the saw. A transverse pelvic osteotomy is then performed at the level of the anterior inferior iliac spine (Fig. 6.4).
8.
Rotate and fix the pelvic fragment. The distal fragment is rotated by pulling the posterior edge of the lower fragment forward and downward with a special hook that can provide long moment arm. It will increase the anterior and lateral coverage of the acetabulum. Concentric reduction of the joint is the prerequisite of the rotation. Noteworthily, Salter’s osteotomy was designed primarily for patients with acetabular dysplasia and subluxation. Only downward rotation is performed without laterally rotating (for patients with AI between 8 and 15 degrees). The continuity in the sciatic notch is not disturbed. However, with the wide application of this procedure, dislocation or even high dislocation is also included in the appropriate indications. There has also been a slight change in the way the operation is done, mainly with the rotation of the distal fragment.
9.
For cases with AI beyond 15 degrees, the fragment should also be pulled laterally, increasing downward rotation. The continuity in the sciatic notch and medial portion of the fragment will be lost after the rotation.
10.
The distal fragment should be aligned with the anterior superior iliac spine and the iliac wing. Propriate K-wires are inserted to fix the bone graft (Fig. 6.5). The first is driven from the upper part of the ilium to the medial surface of the acetabulum, with the K-wire running through the bone wedge, making sure that it is not inserted into the articular cavity. Otherwise, it will affect joint activity and cause damage to the femoral head. The second K-wire is driven in the direction of the first one. Similarly, the joint cavity should stay undisturbed.
11.
Check joint stability and range of motion. The stability of the hip joint should be examined under direct vision to ensure that the anterior margin of the acetabulum does not limit the femoral flexion, which means there is no impingement presented.
12.
The rectus femoris is reattached and the space between the sartorius and the tensor fascia latae is closed. The epiphyseal cartilage of the iliac wing and the lateral periosteum are reduced and sutured, then the wound is closed in layers.
13.
Fix the joint using hip spica postoperatively, and keep the affected limb straight, slightly extended, and rotated inward.

6.1.5.3.6 Postoperative Management

Use hip spica cast postoperatively for 2 months. The healing of the osteotomy is evaluated by pelvic X-ray examination. After clinical healing, joint function exercise should be performed with the patients in bed. Weight bearing is not allowed until 3 months after the procedure.

6.1.5.4 Pemberton Acetabuloplasty

It is also one of the major procedures for the treatments of DDH, sharing almost the same indications with Salter’s osteotomy. Some scholars argued that this procedure would lower the volume of the acetabulum, which, therefore, is suitable for those cases with larger acetabulum. In clinical practice, however, it not feasible to determine indication by measuring the volume of the acetabulum. It is reported the same outcome could be achieved by Pemberton acetabuloplasty compared to other procedures. The pelvic ring is preserved in this procedure, avoiding lateral displacement of the acetabulum.

So, Pemberton acetabuloplasty has gained popularity among more and more surgeons.

6.1.5.4.1 Indications

The procedure shares the same surgical indications of the initial age of surgery with Salter’s osteotomy. Pemberton acetabuloplasty can also be performed on older children whose triradiate cartilage has not yet closed because unossified triradiate cartilage is the hinge of the acetabular fragment rotation.

6.1.5.4.2 Surgical Techniques

The incision, subcutaneous separation, exposure of the joint capsule, joint debridement, and the reduction of the femoral head into the acetabulum was basically consistent with the steps in Salter’s osteotomy. Ilium remains intact in this procedure, so the separation of the periosteum on either side of the ilium should be toward sciatic notch without leading the Gigli saw through the notch.

6.1.5.4.3 Acetabular Osteotomy

This is the key step in the procedure. Before the osteotomy, all the muscles in the surgical field should be pulled apart. A special Hohmann retractor is placed under the sciatic notch to protect the sciatic nerve. The osteotomy path goes from about 1-cm above the upper margin of the acetabulum and passing along the acetabulum to triradiate cartilage from the lateral and medial sides. The line of osteotomy could be drawn on the ilium before the osteotomy with a marker to help the surgeon perform the procedure (Fig. 6.6).

Use special thin curved osteotome to perform the medial osteotomy first, because medial osteotomy is easier to look at than lateral one. The lateral curve of the osteotomy is toward to the triradiate cartilage after the osteotome has fully crossed the acetabulum. After the imprinting of the two osteotomy lines, gradually deepen the line and pay attention to the transfixion between the lateral and median osteotomy lines until triradiate cartilage. Use the osteotome to turn the fragment downward, and the acetabular fragment can rotate completely downward when the osteotomy reaches the triradiate cartilage.

6.1.5.4.4 Fixation of the Bone Graft

A wedge bone graft is harvested from anterosuperior iliac spine and trimmed to support the osteotomy after being inserted in. Using a spreader, make room for the graft. The elastic force between the osteotomy fragments compresses the grafts tightly. A metal bar can be used to tap the wedge bone inward to get the larger acetabular bone downward rotation. When the bone graft is tapped into place, the position is usually stable so that internal fixation is unnecessary (Fig. 6.7).

6.1.5.4.5 Checking the Stability of the Joint

Check the range of motion. Make sure that there is no impingement presented. After all the goals being achieved, suture the wound in layers.

6.1.5.4.6 Postoperative Management

Use hip spica cast postoperatively for immobilization. Other strategies are the same as those for Salter’s osteotomy.

6.1.5.5 Proximal Femoral Osteotomy

Proximal femoral osteotomy (PFO) is the most common complementary procedure in DDH treatment, which can increase the reliability of DDH surgical treatment. DDH is usually accompanied by secondary deformities of the proximal femur, mainly manifested in increased femoral anteversion and neck-shaft angle. In the case of dislocation, especially in the case of high dislocation, if the reduction is not accompanied by femoral shortening, the femoral head after reduction can undermine the recovery of hip joint activity due to the increased tension of periarticular muscle. PFO usually includes varus osteotomy (to correct neck-shaft angle), shortening, and derotation (to correct anteversion). Alternatively, one or two of these procedures are performed in some cases.

In order to maintain a normal limb mechanical alignment, PFO is usually performed on the plane between the greater and lesser trochanter, also known as intertrochanteric osteotomy.

It should be remembered that PFO is complementary to DDH treatment and cannot be administered alone.

6.1.5.5.1 Indications

It includes high dislocation, excessive anteversion of femoral head, increased intra-articular pressure after the reduction of femoral head and limited joint motion. The proximal femur deformations, such as coxa vara and coxa valga, can also be corrected with PFO.

6.1.5.5.2 Implants Options

There are many internal fixation options that can be used for the treatment of proximal femoral osteotomy, from straight plate, angled blade plate, goose head nail, 90-degree blade plates, to the special locking plate for pediatric proximal femur (pediatric hip plate, PHP). PHP has been now widely used in the treatment for DDH due to its prominent performance in the control of osteotomy angle and fixation reliability. This section introduces the insertion process of PHP as internal fixation material.

6.1.5.5.3 Position

The patient is placed on a lateral position, and the affected limb was disinfected and draped below the level of the navel. The affected limb should be moved freely during the operation.

6.1.5.5.4 Incision and Exposure

A straight incision, whose length is similar to that of the plate, is made downward from the apex of the greater trochanter of the femur. The subcutaneous tissue is bluntly separated, and the deep fascia is cut open longitudinally. Expose the vastus lateralis muscle and the apex of the greater trochanter of the femur. The vastus lateralis muscle is dissected along the posterior margin and is severed at the level of the lower margin of the greater trochanter. Then, circumferential dissection of the posterior periosteum of the femur is performed. Hemorrhage at vascular canals should be stanched strictly. When dissecting the posterior periosteum, the assistant should keep the lower extremity as internal rotated as possible, in order to achieve better exposure. The length of the stripping should be enough to place the plate, and after stripping, the wide retractor is used to protect the posterior muscles. The anterior circumferential dissection of the periosteum is performed, and the assistant externally rotates the lower extremity until the anterior and posterior periosteum dissection is connected under the lesser trochanter, and a wide retractor is inserted to protect the anterior muscles.

6.1.5.5.5 Osteotomy and PHP Insertion

The implant that is about to use is determined according to the age of the child and the size of the bone. According to the predesigned angle of varus osteotomy, the guide pin is adjusted to the designed angle by placing the guide plate. The guide pin is inserted right at the anterior edge of the femoral neck during surgery. Place the guide plate on the lateral side of the femur and insert the guide pin 3 ~ 5 mm under the great trochanter, parallel to the longitudinal axis of the femoral neck. The depth should be controlled without touching the physis (Fig. 6.8a). Check the position, direction, and depth of the guide pin using C-arm fluoroscopy. To ensure that the guide pin is located inside the femoral neck and the direction is consistent with the axial fixation of the femoral neck. The position of the insertion is 3–5 mm below the epiphysis of the greater trochanter, and the angle is consistent with the preoperative design. The length of the screw is determined by the length of the insertion and the distance to the physis. The key step of PHP insertion is the accurate placement of the plate through the guide plate and pin. The placement of the guide pin is the crux, which must be strictly conducted according to the operation goals and preoperative design.

Insert two more threaded guide pins through the guide plate placed on the first pin. The osteotomy line under the two guide pins is marked with an osteotomy caliper, and the femur was truncated perpendicular to the femur shaft with an oscillating saw. The osteotomy is performed at the level of the lesser trochanter or slightly superior plane. If the femur needs to be shortened, the distal femur can be marked by shortening length, and then the femur can be cut transversely oscillating saw.

Use the reposition forceps to hold the proximal segment from both sides of the great trochanter and insert the PHP plate with sleeve along the guide pins to ensure that the distal end of the bone remains in contact with the plate. After pulling out the guide pins, insert the locking screws according to the calculated length after corresponding reaming. The sleeve is screwed into the holes of the plate, and the long drill penetrates through two layers of the cortex. The screws are inserted after measuring the length.

The distal femur and plate were clamped with bone holding forceps, and there is point contact between the distal and proximal segments, keeping the plate parallel and centered with the femoral shaft. Through external rotation or internal rotation of distal limb, adjust the anteversion, drill holes, measure depth, insert screws successively and fix the plate.

Keep the plate at the lateral position, and examine the correction, the position of the plate and the length of the screw by C-arm fluoroscopy during surgery (Fig. 6.8b).

After all the requirements were achieved, the vastus lateralis muscle was reduced, and the periosteum and muscles were sutured at the top and the posterior incision, and the deep fascia was closed in layers until the skin was sutured.

If PFO is performed alone, hip spica should be applied postoperatively as external fixation; if it is combined with Salter’s osteotomy or Pemberton acetabuloplasty, the procedure can be performed before or during the pelvic osteotomy.

6.1.5.6 Bernese Osteotomy

Bernese triple osteotomy can achieve greater rotation of acetabular fragment and is suitable for DDH with severe secondary lesions. In recent years, Bernese triple osteotomy has been developed and gained popularity in pediatric orthopedics due to the increasing demand for the treatment for elder DDH as well as complex cases.

Although the Salter’s osteotomy and Pemberton acetabuloplasty have been the classic operation for the treatment of DDH which are suitable for cases in early stages of DDH and patients aged between 3 and 6 years, the two procedures to correct acetabular dysplasia (increasing the lateral acetabular coverage) are greatly affected by the original abnormal acetabular index (AI). It is accepted that Salter’s osteotomy is effective in cases with AI less than 40 degrees. In addition, the presence of AVN of femoral head during the early treatment, coxa magna, and the need for bigger acetabulum, combined with the difficulties in the treatment of patients undergoing revision, promoted the application of Bernese triple osteotomy.

Bernese triple osteotomy consists of osteotomies of the ischium, superior ramus of the pubis, and the ilium, completely releasing the bony limitation surrounding the acetabulum, theoretically providing more space for the rotation of the acetabular fragment. At the same time, Bernese’s triple osteotomy is different from the previous two osteotomy procedures. The rotating axis is the center of the acetabulum, which is more consistent with the biomechanical properties of the hip joint. Bernese osteotomy is relatively difficult and requires a lot of knowledge and experience in hip anatomy and surgical techniques, and its learning curve is far flatter than the ones of the previous two osteotomies.

6.1.5.6.1 Indications

It is suitable for children aged 6–14 years with simple acetabular dysplasia and congruency hip joint; cases with mild hip joint lateral dislocation without secondary acetabulum formed; cases with AVN of the femoral head and inadequate acetabular coverage; cases with complicated joint abnormalities and Bernese osteotomy could be an option for the condition.

6.1.5.6.2 Techniques of Osteotomy

The patient is placed in the supine position, and the affected limb was disinfected and draped. Since the medial femoral incision is required for the sciatic osteotomy, the perineum will be strictly sterilized and covered with a surgical adhesive membrane to prevent the perineum from being exposed during the operation.

1.
Ischium osteotomy: The Lodloff incision is made on the medial side of the femur with the hip joint flexed and abducted. Separate the subcutaneous tissue and expose adductor longus. Separate the interspace between the adductor longus and the pectineus. Protect femoral artery and vein. Probe the ramus of the ischium. Bluntly dissect both sides of the ischium, and the long-handle Hohmann retractor is inserted. Use C-arm fluoroscopy to confirm that the retractor encircles the ramus of the ischium, and the periosteum is dissected on the surface. Probe the sulcus structure of the lower margin of the acetabulum. Protect the peripheral structures with a deep, straight retractor, cut off the ischium transversely with a straight bone chisel. Protect structures around the ischium with Hohmann retractor. The sciatic nerve is located behind the ramus of the ischium and should be protected cautiously.
2.
Osteotomies of superior ramus of the pubis and ilium: The anterior superior iliac spine is taken as the apex, and the incision extends outward and downward along the curve of the iliac wing through the anterior superior iliac spine, forming a semicircular lateral skin incision. Separating the subcutaneous tissue. The space between the sartorius and the tensor fascia latae was cut open, exposing the rectus femoris and the lateral joint capsule. Cut open the lateral periosteum of the iliac wing and expose the lateral ilium plate until sciatic notch. Pull the sartorius medially, divide the sartorius muscle and the iliopsoas muscle below, cut off about 2 cm of bone of the anterior superior iliac spine, and separate the sartorius together medially. From the lateral fossa of the iliac wing, obliquus externus abdominis is separated. The iliac insertion of obliquus internus abdominis is also bluntly divided, along with sartorius, being pulled medially. The iliac insertion of iliopsoas is cut off and separated until sciatic notch.

Make the joint slightly flexed and adducted, pulling the sartorius and the iliopsoas medially, exposing the superior ramus of the pubis near the acetabulum. Then, dissect the muscles attached to it. A Hohmann retractor is inserted below the superior ramus of the pubis. After confirmed by C-arm fluoroscopy, the periosteum is cut open, and the pubis is transversely transected near the acetabulum, and the periosteum is cut off carefully.

About 1-cm above the anterior inferior iliac spine, toward the greater sciatic notch, cut the ilium until 1 ~ 1.5 cm above the greater notch with the chisel or oscillating saw.
3.
Rotation and fixation of acetabular fragment: Insert a K-wire into the acetabulum as a handle, rotate it downward and laterally. Adjust the acetabulum direction in the sagittal plane. A 2.5-mm or 3-mm K-wire is used to insert from the iliac wing to temporarily fix acetabulum bone. The acetabular coverage and acetabular direction are confirmed by C-arm fluoroscopy. When the rotation is satisfied, the long cortical screws are inserted from the ilium to the bottom of the acetabulum, the top of the acetabulum, and above the acetabulum to the sacroiliac joint. In children, bone grafting is not necessary for the space between the acetabular fragments.
4.
The sharp lateral projection on the acetabular fragments is trimmed. The sartorius insertion is reduced to its original position and is fixed with two 30-mm long cortical bone screws. The tensor fascia latae, obliquus externus abdominis, and obliquus internus abdominis are sutured on both sides of the iliac wing respectively, and other soft tissues are sutured in layers until the skin (Fig. 6.9).

6.1.5.6.3 Postoperative Managements

Use hip spica cast or rigid brace postoperatively for immobilization.

6.2 Legg-Calvé-Perthes Disease

Legg-Calvé-Perthes disease (LCPD), also known as Perthes disease, caused by infarction of the upper femoral epiphysis, is an idiopathic disorder affecting children. It is complicated by trabecular fracture and associated with a process of repair, which can, at worst, end up with growth disorder of the epiphysis and deformed proximal femur.

The term is named after the four clinicians, Arthur Legg, Jacques Calvé, Georg Perthes, and Henning Waldenström, who independently recognized and reported the condition from 1909 to 1910. Completely different from osteonecrosis of the femoral head in adults, Perthes disease is self-limited, self-healing, and non-systematic. The course of the disease consists of an initial stage, fragmentation stage, healing period, growing period, and definite period. The femoral head could end up with normal morphology or deformity due to abnormal healing. Despite some progress made during the past century, the underlying etiology, as well as pathological features, remain unknown, the course of the disease difficult to predict, and the best method of treatment not determined.

There is a variation of incidence between population groups worldwide, ranging from 0.2/100000 to 29.4/100000. The incidence is 3.8/100000 in Asia. The condition affects boys more often than girls with a 3:1 ratio. Bilateral Perthes disease affects 15% of patients concurrently or consecutively. The clinical onset is usually between 4 and 8 years old.

The cause of the disease is unknown. Trauma, thrombophilia, endocrine, fatigue injuries, and inheritance are several widely accepted theories about its etiology. In recent years, the results of animal experiments showed tissue damage caused by focal hypoperfusion is the pathogenesis of the condition. However, it is still controversial whether the hypoperfusion happens in a single or multiple blood vessel(s).

6.2.1 Classification

There are several classification systems that have been accepted and adopted widely. Waldenström classification described the chronological stages of the disease; Catterall classification is based on increasing proportions of femoral head involvement; Herring classification depends upon the extent of involvement of the “lateral pillar” of the femoral head, which is now considered closely related to the prediction of the prognosis. Furthermore, Stulberg’s classification, assessing the sphericity and congruency of the hip at maturity, is used as a surrogate for therapeutic effect evaluation [1].

6.2.1.1 Waldenström’s Chronological Stages

There are four stages based on the radiological appearances: initial stage, fragmentation stage, reossification stage, and healed stage (Fig. 6.10).

6.2.1.1.1 Initial Stage

It is the early appearance of the disease. The epiphysis is dense due to growth arrest caused by ischemia, and is smaller compared to the contralateral side with widened joint space on account of synovitis. The physis grows irregularly with “decalcinated” spots in metaphysis area.

6.2.1.1.2 Fragmentation Stage

The epiphysis is extremely flattened and divided; the small granules appear like sequestrum, which are dense on the X-ray film. Signs of subchondral bone fractures can be seen.

6.2.1.1.3 Reossification Stage

New bone, which can be detected among the fragmented epiphysis, gradually replaces the necrotic bone. The epiphysis stops flattening with a clear margin.

6.2.1.1.4 Healed Stage

The morphology of the femoral head restores gradually. Trabecular alignment becomes regular. The permanent residual features can be seen in this stage.

6.2.1.2 Catterall Classification

This classification system, described by Catterall in 1971, had been widely used around the world, which is a milestone event along with the history of studying this condition. The four groups are based on increasing proportions of femoral head involvement on the anteroposterior and lateral view of hip X-ray films (Fig. 6.11).

6.2.1.2.1 Group 1

Only the anterior part of the epiphysis is involved. No collapse of the femoral head is seen.

6.2.1.2.2 Group 2

More of the epiphysis, less than 50%, is involved after absorption of the involved segments in Group 1.

6.2.1.2.3 Group 3

Approximately 75% of the epiphysis is involved.

6.2.1.2.4 Group 4

The whole epiphysis is sequestrated and collapsed. The femoral head is flattened and it can “mushroom” anteriorly and posteriorly. Moreover, after conducting intensive researches, Catterall described several “head at risk” signs that contribute to the prediction of the outcomes and prognosis of Perthes disease, improving the accuracy of Catterall classification.

Femoral head lateral subluxation.
Calcification lateral to the epiphysis.
Diffuse metaphyseal reaction (cystic change).
A horizontal growth plate.
Gage sign: V-shaped lytic appearance in lateral epiphysis and metaphysis.

The signs can appear alone or in combination. “Head at risk” signs at early stages usually indicate poor prognosis (Fig. 6.12).

6.2.1.3 Herring Classification

In 1992, Herring et al. described a classification system based on the extent of involvement of the “lateral pillar” of the femoral head, which can guide clinical management because it is closely related to the prognosis of the condition. Therefore, Herring classification has become the most commonly used classification system worldwide. On the AP film of the hip joint, the lateral pillar is described as the area in the lateral 15–30% of the epiphysis, central pillar 50%, and medial pillar 20–35%. Lateral pillar height is compared with the unaffected hip. There are four types in this classification system (Fig. 6.13).

6.2.1.3.1 Type A

No involvement of the lateral pillar.

6.2.1.3.2 Type B

<50% of the lateral pillar height lost.

6.2.1.3.3 Type B/C

The extent of the lateral pillar involvement is between Types B and C. There are three subtypes: the lateral pillar is narrow (2–3 mm) with less than 50% involvement; only some fragments remain with less than 50% height lost; 50% of the lateral pillar is involved compared with central pillar.

6.2.1.3.4 Type C

More than 50% of the lateral pillar height lost.

6.2.1.4 Stulberg Classification

Stulberg classification, first published in 1981, assesses the sphericity and congruency of the hip at maturity. The prognosis of Perthes disease is closely related to the morphology and congruency of the hip joint. Five classes of deformity are described.

6.2.1.4.1 Class I

Completely normal hip joint.

6.2.1.4.2 Class II

Spherical femoral head with concentric congruency on AP or lateral film. The femoral head is larger than normal, or the femoral neck is shorter, or the acetabulum is abnormally steep.

6.2.1.4.3 Class III

Non-spherical (ovoid or mushroom-shaped or umbrella-shaped), but not flat, femoral head. Joint space is widened, usually more than 2 mm.

6.2.1.4.4 Class IV

Flat femoral head (1-mm collapse at the weight-bearing area) and abnormalities of the femoral head, neck, or acetabulum.

6.2.1.4.5 Class V

Flat femoral head and a normal femoral neck and acetabulum. The rotation of the hip joint is restricted, but the range of flexion and extension is normal. The affected limb is often fixed in extreme external rotation in order to adapt to the incongruent joint.

6.2.2 Treatment

There are various treatment options with an enormous controversy, consisting of conservative and surgical treatment. Furthermore, according to the principles of treatment, these options can be divided into etiological and palliative treatments. The former includes intra-articular vascular decompression, restoring, and increasing the blood supply to the affected femoral head, and so on. The latter aims to maintain the congruency of the joint, depending on the capacity of bone molding to restore the morphology of the epiphysis. However, these treatments have not been supported by enough evidence of evidence-based medicine except containment treatment, one of the palliative treatments. Age and severity of the condition are usually taken into consideration when physicians are making decisions about the treatment options [2].

Waldenström’s chronological stages, Catterall classification, and Herring classification are three most commonly used classification systems in clinical practice to evaluate the severity and predict the prognosis. With concurrent “head at risk” signs, groups 3 and 4 in Catterall classification, or Type B/C and C are defined as severe Perthes disease.

After long-term follow-ups, it is found that before the age of 55–60 years, patients’ joint function is well enough to support daily life. However, after that age, most of the patients need arthroplasty to maintain the joint function and quality of life. Pain in the joint during walking and decreased ROM of the joint occur particularly in patients with flat femoral head or shortened femoral neck accompanying overgrowth of the great trochanter caused by damaged physis. Therefore, the aim of the management is to maintain the joint ROM and to prevent and alleviate secondary femoral head deformity.

Herring et al. once conducted the largest multicenter prospective research about the classification system proposed by Herring himself, which lay the foundation for widespread support and application nowadays. With the cooperation of pediatric orthopedic physicians from various centers in North America, Herring and his colleagues had observed 438 children (451 hips) with Perthes disease between 6 and 12 years old. After long-term follow-ups, they evaluated the outcomes of various treatments, including weight-bearing abduction braces, physiotherapy, femoral osteotomy, and acetabular osteotomy (some of the patients did not receive any intervention). At last, 337 patients were followed until maturity. Researchers found that Herring classification and initial onset age were closely related to the prognosis of Perthes disease: after 8 years old, group B and group B/C border hips have a significantly better outcome if treated with surgery compared to group C hips; before 8 years old, regardless of age or treatment options, group B hips have a good prognosis while group C hips have unfavorable prognosis. The result of this study confirmed that both Herring classification and initial onset age are reliable predictors of the outcomes. Although some scholars proposed that after 6 years old the prognosis of the condition is poor, most researchers regard the age of 8 years as the threshold of receiving surgical intervention. Once the patients are older than 11–12 years old, even with Catterall group 2 hips, surgeries cannot alter the poor prognosis of these patients. Furthermore, the age of entering reossification stage is an important predictor. The more mature the bone is when the condition enters reossification stage, the poorer the result.

B. Joseph put forward a unique viewpoint that the earliest pathological change is lateral “extrusion” of the lateral part of the epiphysis, which means this part of the femoral head is extended and bulged laterally. Once the extrusion is presented, the prognosis would become poorer. The treatment will lead to a satisfying outcome before the presentation of the “extrusion,” otherwise, the effect of the interventions is always fruitless and frustrating. Most of the physicians would not perform the surgery until the patients are 8 years old. B. Joseph opposed this viewpoint, and he believed that age is not the only indication of the surgical intervention. Perthes disease in some patients younger than 8 years progressed rapidly. It is easy to delay the treatment for these children, which would also lead to an unsatisfied result.

Various methods of interventional treatment are based on the concept of “containment,” which assumes that the acetabulum will contain and mold the softened femoral head and result in a spherical and congruous joint gradually through bone remodeling. Containment treatment includes conservative and surgical treatment. Devices such as brace and plaster are designed for containment treatments. The main drawback of conservative treatment is that the patient must put up with a prolonged non-weight-bearing lifestyle until the femoral head had reossified, which often takes 2–3 years. The goal of the surgery is to cover the deformed femoral head with ossified acetabulum in order to achieve adequate coverage. Common surgical methods are Salter innominate osteotomy, proximal femoral varus osteotomy, and a combination of Salter’s and femoral osteotomies. Detailed operation methods are described in Sect. 6.1.5.

6.2.2.1 Proximal Femoral Varus Osteotomy (PFO)

This is the most commonly used surgery in the treatment of Perthes disease. The varus osteotomy is performed between the level of lesser and greater trochanters, so that the coverage of the head can be increased. Less than 20 degrees varus is acceptable. An extreme varus neck-shaft angle will lead to coxa vara and great trochanter impingement, which alters the biomechanical features of the hip joint significantly.

6.2.2.2 Salter Innominate Osteotomy

Salter’s osteotomy, which rotates the whole acetabulum forward and laterally to increase the head coverage, is also an option to treat the condition. Excessive and forceful rotation of the acetabulum will produce massive pressure upon the femoral head. Subsequently, femoral head ischemia deteriorates.

6.2.2.3 Combined Surgery

In order to increase the coverage and avoid massively altering the structure of the hip joint at the same time, many physicians prefer combined surgery to achieve the goal of containment treatment. PFO, with 10–15 degrees varus, combined with Salter’s osteotomy or triple pelvic osteotomy is the most commonly used method.

It is reported that containment surgery can shorten the disease course which, however, has not yet been confirmed by evidence-based medicine research. This kind of surgery, according to other studies, can also decrease the duration of non-weight bearing rest. The patients were allowed to start walking 6 months postoperatively or after the osteotomy is healed, without further collapse and deformation of the epiphysis.

6.3 Slipped Capital Femoral Epiphysis

Slipped capital femoral epiphysis is a condition which affects femur with open physis. Posterior slipping of the upper (capital) femoral epiphysis, which remains in the acetabulum, is one of the most common causes of pain in the hip region and limping. The disorder can damage the normal structure of the joint. These patients are more likely to suffer from hip disability and osteoarthritis in early adulthood. Chondrolysis and avascular necrosis, two common complications of the condition, would cause pain and dysfunction of the hip joint. Early recognition and proper management can prevent exacerbations and preserve the normal functions of the hip joint without further arthroplasty.

Slipped capital femoral epiphysis is a common disorder affecting adolescence worldwide. According to the results of American research, the incidence is 2–3 per 100,000 children and adolescents with male predominance. The average initial onset age is 12.1 years whereas girls are afflicted 1.5 years younger than boys; the left hip is affected in most cases; the incidence will increase in June. There is no reasonable explanation for these phenomena. Obesity may be the main cause of the condition. In 60% of the cases, body mass index-for-age is over 90 percentiles. It was found that more obese children were prone to suffer the disorder at a younger age.

There is no accurate data about the incidence of SCFE. Before the implementation of the reform and opening-up policy, the condition is rare in China. However, with economic development, SCFE has become more and more common, in accordance with the increased incidence of obesity.

6.3.1 Etiology

The etiology of SCFE has not been elucidated. However, biomechanical, endocrine, hereditary factors, and so on are considered as pathogenic contributors. Adolescents, featured by the growth spurt, are more susceptible to SCFE, which suggests hormonal changes may play a role in the process. Obesity will generate excessive shear stress across the growth plate, which may be one of the causes of the condition. Other etiological factors include joint structural abnormalities, immunological disorders, and environmental changes.

The slipping always develops gradually with no defined trauma. In early adolescence, the direction of the proximal femoral physis changes from horizontal to approximately vertical, which generates more and more shear stress across the physis; moreover, weight increases significantly in adolescence. Coincidentally, the physeal plate widens and weakens during the growth spurt. All of the factors are responsible for the pathogenesis of the condition in this group of children.

Ossification of the epiphysis needs the involvement of thyroid hormone, vitamin D, and sufficient calcium. Therefore, children with hypothyroidism or renal osteodystrophy suffer from SCFE more easily due to decreased stability in physis. Approximately 7% of the patients, usually with short stature and delayed closure of the physis, are afflicted by endocrine disorders, among which hypothyroidism is the most common one. It was believed that subclinical vitamin D deficiency is one of the etiological factors. However, endocrine diseases of most patients with SCFE cannot be diagnosed without direct evidence. Bilateral involvement indicates the children might suffer from osteodystrophy or endocrine disorders.

Growth hormone (GH) also contributes to the weakness of proximal femoral physis because GH treatment, reported by some researchers, enhanced the risk of SCFE; however, the results of serous GH level tests are always normal. The level of serous GH in healthy children varies greatly while the levels of GH transmitter, IGF-1, and associated protein are stable. The interplay of these factors has not been confirmed by cogent evidence. The hypothesis that SCFE is associated with the level of GH, therefore, has not been yet established.

Decreased femoral anteversion is associated with chronic SCFE, especially in African children, while the direction of the acetabulum and tibial torsion are not. It was found that there is a positive correlation between the depth of the acetabulum, measured by a center-edge angle (CE angle), and the risk of slippage, which was confirmed both in Africans and Caucasians. Calculations showed shear stress across the physis will increase, as the depth of acetabulum increases. Excessive shear stress leads to a greater risk of SCFE. In general, acetabular CE angle is greater in African children, which probably a reason for higher incidence among them.

Previous irradiation therapy for a malignant tumor near the physis may also increase the risk of SCFE in a dose-related manner. Furthermore, radiotherapy will damage the endocrine glands, and the dysfunction of these glands makes the physis weaker and more susceptible to SCFE. Chemotherapy can intensify the influence of radiotherapy on physis, probably resulting in severe joint dysfunction. Children with radiotherapy-induced SCFE usually have normal body weight and unilateral involvement. Chronic and mild slippage is common in these children, while with younger initial onset age. It often takes a long time for physis to close after the clinical intervention. Therefore, repeated slippage would occur in these children when the tip of the screws is not in the epiphysis anymore due to overgrowth of the femoral neck.

6.3.2 Clinical Manifestations

Obesity is common among children with SCFE. Main complaint is pain in the groin and limping. Left hip involvements are more common. Patients complain of knee pain in some cases. The condition presents in adolescence and preadolescence. The average onset age is 12 years in girls, and 13.5 years in boys. Weight-bearing walking is tolerable. The involved limb lies in external rotation and abduction. Moderate or severe trauma has been reported in some cases in which the pain would be probably considered as the result of injuries.

6.3.3 Clinical Classification

In clinical practice, the condition is graded into the stable and unstable slip by the disability regarding weight bearing. Children with stable slip can walk independently.

Eighty-five percent of the cases are a stable slip, most of which are chronic onsets. The history is more than 3 weeks’ duration. Some patients presented the symptoms for 5 months and even longer. These groups of patients always have no problem with walking. Moderate pain in the hip region is generally marked.

A sudden severe pain suggests unstable slip, which prevents the patients from weight bearing, even when crutches are being used. The pain often presents in the hip region of the groin, which is intolerable compared to the pain in stable slip cases.

Unstable symptoms presentation can be seen in patients with stable slip after mild to moderate injuries. It always indicates a rapid further displacement of the epiphysis under the circumstances of trauma or weight bearing, which is called acute-on-chronic slip.

Significant unstable femoral capital epiphysis can be recognized under fluoroscopic examination. Usually, SCFE should be differentiated from the epiphyseal fracture. And AVN may complicate the condition in up to 50% of the cases. The only symptom in stable SCFE cases is mild pain in the groin or knee, and weight-bearing walking is tolerable. However, limping and walking with assistance can occur in these patients. Children with stable slipping suffer from chronic symptoms without significant radiological change. Sometimes these cases were diagnosed by the presentation of callus and remodeling of the proximal femur on the plain film, while they have a low risk of AVN. This classification system does not depend on age and body weight.

Adolescents with knee pain should be examined closely because approximately 15% of the patients complaint about knee pain at the very beginning, which can last for a long period. If the knee pain is presented as the only symptom, the accurate diagnosis can be easily delayed. Therefore, children’s knee pain without any recognized causes should be examined carefully including the entire lower limb and hip joint.

When the physical examination was performed, the pain was evident when the hip was passively internal rotated. The epiphysis comes to lie posterior to the femoral neck, which results in external rotation and posterior extension of the hip joint. Meanwhile, limited flexion, increased external rotation when the hip flexes, and out-toeing gait are the main manifestations of the condition. Pain is evident when patients are afflicted with unstable hip joint and synovitis. Patients with mild slipping only suffer from sight pain, and the motion of joint usually remains normal. The deformity of the stable slipping cases should be focused on rather than the pain as the condition progresses, especially for those cases with evident external rotated hips.

Left side predominance has been observed. Sixty percent of the cases involve the left side. And bilateral slipping cases account for 60% of all patients successively. It is reported the second slipping usually happens 18–24 months after the contralateral epiphysis slipped. After long-term follow-ups, it was found that up to 80% of the cases are bilateral SCFE including those with asymptomatic contralateral slipping. Degenerative osteoarthritis can occur in approximately 30% of the asymptomatic contralateral slipping cases.

6.3.4 Imaging Examinations

Anteroposterior radiographs of the pelvis and lateral radiographs of the femoral neck are needed for diagnosing the condition. Frog lateral view is the most commonly used projection for examining the proximal femur, which, however, can cause pain and further slipping of the epiphysis in patients with acute onset. Therefore, it should not be applied in these cases. In the early stage of SCFE, widened physis and irregular changes of the structures around the physis can be detected on pelvic AP film. However, in some severe cases, the growth plate seems, on the contrary, to be narrow because the epiphysis lies posterior to the femoral neck. The narrowed physis is different from the closing of the physis, for the former will present a dense area in proximal femur due to the overlap of epiphysis and metaphysis. The line of Klein describes a line along the superior edge of the femoral neck. It is useful in detecting early SCFE in adolescents [2]. The line should normally intersect the lateral part of the superior femoral epiphysis. The line of Klein would fail to intersect the epiphysis during the acute phase (Fig. 6.14). The dislocation and the posterolateral portion of the epiphysis are more evident in lateral view than AP view. In chronic cases, suspicious bone healing signs can be seen on X-ray examination. New bone formation appears in the median portion of the metaphysis with stippled changes, or the callus appears on the margin of the anterior portion.

The acute diagnosis of SCFE cannot be made with AP or lateral pelvic film before the epiphysis slips. In the early stage, up to 80% of the cases can be detected by AP and lateral pelvic film, whereas the diagnostic rate will drop to 60% only by AP view. The sensitivity of ultrasound scanning is 95%, which can show abnormalities of the hip joint and periarticular soft-tissue. Proximal femur can be observed, and the slip can be measured accurately by CT scanning which also can detect subtle dislocation of the epiphysis (Fig. 6.15). MRI scanning, which can reveal the early changes in the epiphysis, may be appropriate in the “pre-slipping” phase. Bone scans are more commonly used to assess the presence of vascular lesions, which had been recommended to be routine practice. Unstable slip leads to reduced epiphysis isotope uptake which, however, does not mean unstable SCFE has the complications of AVN. The proliferation of periarticular blood vessels can be seen in the cases of synovitis. It should be differentiated from SCFE. Preoperative and postoperative changes in bone scan remain unclear.

6.3.5 Measuring the Slip

SCFE can not only be classified by clinical manifestations but also be measured by the results of radiographic examinations. Clinically, the condition is graded by the length of history (acute, chronic, and acute-on-chronic slip) and the disability regarding weight bearing (stable and unstable SCFE). SCFE is grouped radiographically according to the measurement of the slip angle and the displacement of the epiphysis, which was quantified on the lateral view using the ratio of slip distance to the diameter of the femoral neck proximally [1]. A mild slip is less than 33%; a moderate is 33–50%, and severe is more than 50% displacement (Fig. 6.16).

The slipping angle (Southwick angle) is formed by two lines: the midline of the femoral neck; and a line perpendicular to the line connecting the lowest two points of the epiphysis. The degree of slip is defined as follows [1]:

Mild—The angle is less than 30 °.
Moderate—The angle is 30–50 °.
Severe—The angle is more than 50 °.

The measurement can also be performed on the images of CT scanning.

6.3.6 Treatment

SCFE is not a traumatic condition, so the objective of the treatment is a stable fixation of the slipped epiphysis to stop further progression. To induce premature physeal closure is an effective way to achieve the treatment goal. It is very important to keep in mind: when treating the condition, do not try any forced manipulation. Early diagnosis and definition of the slip are the key points at the very beginning and then in situ pinning should be performed to stabilize the epiphysis. Closed reduction can cause iatrogenic injuries to the physis and increase the risk of AVN of the femoral head. Traction reduction would be a feasible option only when dealing with cases with an early stage of acute or acute-on-chronic SCFE usually for 3–5 days. Epiphysiodesis should be performed in time regardless of the results of traction. Internal fixators must be placed across the physis, which can induce premature physeal closure.

Early diagnosis can improve the prognosis that the epiphysis would be fixed timely and lower the risk of early-onset osteoarthritis caused by the incongruent hip joint. Even for stable SCFE, slight trauma and tripping could result in severe displacement of the epiphysis. This made it far harder to treat the condition, so once the diagnosis was established, the patient would need emergency management. Before the treatment starts, weight bearing is forbidden, and the most widely used method is single screw fixation which is across the physis. Other options include hip spica cast fixation, multiple K-wires or screws fixation, and Bone-peg epiphysiodesis. Various proximal femoral osteotomies, if necessary, can be used to solve the problem of the incongruent hip joint.

6.3.6.1 In Situ Fixation

Percutaneous fixation is widely accepted, using a single cannulated (≧6.5 mm), full-threaded screw placed as centrally in the epiphysis as possible. Multiple K-wires fixation is rarely used because the operation dramatically increases the risk of screw penetrating the joint surface, which would severely damage the joint functions. The entry point lies in the femoral metaphysis. A small incision can be made to expose the anterolateral portion of the femur. For greater degrees of slip, the guide wire and subsequent screw need to be placed through a more anterior site in the femoral neck. The insertion should be performed under the guidance of anteroposterior and lateral projections on the image intensifier with the lines of the insertion being marked out on the skin of the proximal thigh. The intersection point of these two lines on the skin is where the incision is to be made (Fig. 6.17). Use the image intensifier to confirm the screw does not penetrate the joint.

There are several key points of this procedure:

1.
The screw should be placed in the epiphysis as centrally as possible. And the direction should be perpendicular to the bottom line of the epiphysis. It will ensure stable fixation with low risk of penetrating the joint. For a more posterior slip of the epiphysis slip the screw need to be placed through a more anterior site in the femoral neck.
2.
The screw is inserted in the epiphysis across the physis under the guidance of the image intensifier in the direction of lines marked out on the skin. The position of the guide wire can be adjusted if it is not satisfying on the images. The first one should be left in the epiphysis as the reference of the second insertion.
3.
Do not penetrate the joint with the guide wire, the drill, the tapping screw, and screws.
4.
For the fixation of unstable SCFE, a second guide wire should be inserted parallel to the first one in median inferior quadrant, which can provide anti-rotational stability.
5.
The single cannulated full-threaded screw must be placed across the physis. Long screw tail outside the cortex will irritate the soft tissue. Before the incision was closed, make sure that the tip of the screw does not penetrate the joint (Fig. 6.18).

Postoperative management: it is recommended that hip spica cast be applied for 6–8 weeks. After the cast being removed, traction should be used, and active joint activity without weight bearing is encouraged. Walking is not allowed until the closure of the physis is confirmed on the radiographs taken 3 months after the surgery. Some physicians allow the patient ambulating with walking aids 48 hours after the surgery. It is difficult to carry out in China for some reasons. Patients can try independent walking after there is no pain in the hip. Except for some vigorous activities such as jumping and leaping, physical activities are acceptable. A follow-up duration of 3–6 months is recommended to monitor complications and contralateral slip through physical examinations and radiographs until the closure of the physis.

Besides, after the closure of the physis, the screw can be removed. However, screw removal is not recommended for patients younger than 10 years. If the screw retreats below the physis due to the growth of the physis, and the physis is not completely closed, the femoral head epiphysis may slip off again. At this time, a longer screw should be inserted to replace the former one.

6.3.6.2 Bone-Peg Epiphysiodesis

Bone-peg epiphysiodesis is also a classic method to treat the condition. With the development of the orthopedic implants, however, it has been abandoned by most surgeons. A bone peg, which is nail- or wedge-like, is inserted across the physis to retard the growth by inducing the closure of the physis. It is reported the complication rate was very low. However, it has been replaced gradually by in situ pinning, due to massive exposure and demanding surgical techniques.

6.3.6.3 Cast Immobilization

It is not a routine practice to apply hip spica cast for the treatment of SCFE because the method cannot prevent further slipping of the epiphysis. The physis will not close immediately after the joint being fixed with cast, and the slipping may even progress during cast fixation. Once the cast is removed, Slipping may occur again with an open physis. There is one exception in which cast immobilization is indicated. In situ pinning cannot provide reliable stabilization in cases with metabolic bone disease. The postoperative application of hip spica cast can assist in stabilizing the epiphysis.

6.3.6.4 Contralateral Prophylactic Fixation

It is still controversial about prophylactic fixation of the “asymptomatic” contralateral epiphysis after the onset of the other side. Bilateral epiphyseal slips occur in at least 22% of the cases, according to the results of previous studies. The rate of a later, contralateral slip is up to 80%. Therefore, the prophylactic in situ fixation should be performed in patients with radiographic signs of contralateral slip even if the contralateral hip is asymptomatic. It is still not recommended to pin the contralateral hip if the radiographic examination is negative and the hip is asymptomatic. However, for patients with endocrine disorders and osteodystrophy, the condition is always bilateral. So, it is necessary to perform the prophylactic fixation of contralateral epiphysis in these cases.

6.3.6.5 Corrective Femoral Osteotomy

Despite all of the advantages of in situ fixation, it cannot correct the deformities deriving from the original slip. The dislocation of the femoral head epiphysis can result in an incongruent hip joint, which predisposes patients to degenerative osteoarthritis and may also cause more serious femoral head necrosis. Proper corrective proximal femoral osteotomy can delay or prevent these complications. Proximal femoral intertrochanteric or subtrochanteric osteotomy can achieve the treatment goals with a low complication rate. Other commonly used methods include subcapital wedge osteotomy, femoral neck fundus osteotomy, and transtrochanteric osteotomy.

6.3.7 Complications

The most common complications of SCFE are chondrolysis and avascular necrosis of femoral head, which might be protopathic or iatrogenic.

6.3.7.1 Chondrolysis

Chondrolysis occurs in approximately 1.5% of patients who receive in situ fixation, and 50% in cases with hip spica cast immobilization. Female predominance is evident. This complication can be spontaneous and not caused by treatment, which can occur at the first visit to a doctor for SCFE, or it can be iatrogenic, especially related to intra articular pin penetration.

6.3.7.1.1 Clinical Manifestations

Anchylosis with continuous pain in the thigh or the hip region.

6.3.7.1.2 Physical Examinations

Flexion, abduction, and external rotation of the hip joint are limited. And the pain is evident during the joint movement. Walking and other lower limb activities can be restricted due to anchylosis.

6.3.7.1.3 Radiographic Features

Joint space usually disappears in the end. To meet the diagnostic criteria, joint space should be at least 50% or 3 mm more narrow than the contralateral side on pelvic AP films. The diagnosis can be made if the joint pain, anchylosis, and narrowed joint space. The result of bone scan would show increased isotope uptake, which, however, cannot be reliable evidence to support the diagnosis.

6.3.7.1.4 Pathogenesis

The exact cause of chondrolysis remains unclear. It is presumed that articular chondrodystrophy, which is caused by reduced or even depleted synovial fluid, leads to chondrolysis. The laboratory tests show significantly elevated serum immune globulin as well as complement C3. In some cases, IgM fragmentation increases. According to these findings, some kinds of antigens are generated as the slip happens, which induces immune reactions leading to chondrolysis. Some researchers proved that the immune system is activated in some SCFE cases. However, the clear-cut relationship between an active immune system and SCFE or chondrolysis has not been established.

Some scholars proposed that hip joint penetration during the surgery using metal implants can cause chondrolysis. Even temporary penetration can cause the condition. It is, therefore, considered to be an autoimmune response induced by cartilaginous fragments. On the other hand, those who oppose this viewpoint argue that it is very likely to penetrate the joint during the surgery treating SCFE. Not everyone who receives the operation is afflicted with chondrolysis. Direct evidence has not been found to support the causative connection between joint penetration and chondrolysis.

6.3.7.1.5 Treatment

There is no specific and effective treatment for this complication. During the operation, the surgeon should be careful to avoid infection and joint penetration. Joint irrigation is necessary for patients with articular infection. Computed tomography scanning is helpful to find out whether joint penetration is presented. If it does happen, the implants have to be removed or replaced before closure of the physis. Supportive treatment includes activity restriction, walking aids, mild exercise to maintain joint ROM, and anti-inflammatory treatment. As for iatrogenic chondrolysis, constant traction and surgical intervention such as muscle release and capsuloplasty are recommended to be applied. However, the efficacy of these methods is unknown. When persistent severe pain and restricted range of motion are presented, arthrodesis and THA are considered.

6.3.7.2 Avascular Necrosis of Femoral Head

The most serious complication of SCFE, which is usually presented in unstable slip cases after the patients receiving treatments especially closed reduction or surgical intervention, is avascular necrosis of femoral head (ANFH). While in those with stable slips who received physis fusion and in situ pinning, this complication is rare because the blood supplies had not been disturbed.

The complication is characterized by ischemic necrosis of partial or entire epiphysis because the regional blood vessels are impaired, frequently accompanied by absorption of the necrotic bone. Different from Perthes disease, the necrosis is rarely restored spontaneously after the blood vessels are disturbed. Ascending branch of medial femoral circumflex artery running posterolaterally, ligamentum teres and metaphyseal blood vessels traveling through physis in later puberty are three main blood supplies of the femoral head in this age group. The lateral epiphyseal artery is easily damaged due to the rapture of periosteum when the acute dislocation of the epiphysis happens. Forced manipulation can also make the posterior periosteum injured. During the intraarticular operation, vital retinacular vessels could be damaged because of massive stripped periosteum and reduction of the epiphysis, which will lead to the ischemia of femoral head. Theoretically, epiphysis was deprived of blood supply due to tamponade caused by acute infusion after slipping. However, it has not been proved by any study. Blood vessels in the superior-posterior quadrant are most easily injured. Segmental necrosis could be presented once these vessels are disturbed.

On X-ray film, the affected epiphysis appears to be denser as the bone resorption is deterred as the result of ischemia. It could be presented as early as several weeks after the initial slips, usually after 1 year in most cases, and rarely after 18 months. Then the epiphysis collapse. ANFH can be total or segmental, which share different radiographic changes. Doppler ultrasonography and isotope bone scanning confirm AVN at an early stage postoperatively. MRI can also detect the changes with high sensitivity. These examinations can only confirm the condition, which cannot provide any clue about further developments and prognosis. There have not been effective methods to treat the condition.

Clinical manifestations and radiographic changes vary greatly. Some patients present increasing pain, deformities, and loss of hip joint function. Surgical intervention to restore the joint function can be applied in these patients while conservative treatment is suitable for those with limited pain. Some patients’ condition does not have any symptoms only with radiographic changes such as the collapse of the femoral head epiphysis. These cases need close follow-ups to monitor any sign of degenerative osteoarthritis. There are usually three management outcomes of ANFH after SCFE: surgical intervention at an early stage, later surgical procedures, and treatment without any operation.

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Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China
Bochang Chen

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Bochang Chen
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Department of Orthopaedic Surgery, Shanghai Jiao Tong University, Shanghai, China
Changqing Zhang

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Chen, B. (2021). Pediatric Hip Disorders. In: Zhang, C. (eds) Hip Surgery. Springer, Singapore. https://doi.org/10.1007/978-981-15-9331-4_6

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DOI: https://doi.org/10.1007/978-981-15-9331-4_6
Published: 18 December 2020
Publisher Name: Springer, Singapore
Print ISBN: 978-981-15-9330-7
Online ISBN: 978-981-15-9331-4
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