Introduction

Intracapsular femoral neck fractures occur in a bimodal distribution. The most common peak occurs in elderly patients, generally in their eighth decade [1]. Such an injury is typically a fragility fracture [2]. Conversely, femoral neck fractures in the young adult are less common and frequently the result of high-energy mechanisms such as motor vehicle collisions or falls from height [3–6]. A subset of femoral neck fractures in the young are from repetitive activities, such as athletes and military recruits [7].

As such, femoral neck fractures in the young patient are a distinct clinical entity from those in the elderly requiring different evaluation and management considerations. A recent meta-analysis describing complications of femoral neck fractures in young adult patients found a reoperation rate of approximately 18 %, nonunion rate of 9 %, avascular necrosis rate of 14 %, and an implant failure rate of nearly 10 % [8]. These rates are consistent with previously published rates in the literature [5, 9–11]. With that in mind, clinical decision making, judgment, and surgical technique are of utmost importance to reduce those complications. Despite this, timing of surgery, reduction strategies (open versus closed), implants of choice, and fixation configuration remain topics of great debate in the orthopedic trauma literature. The aim of our paper is to present our surgical strategies in the form of tips and tricks so as to strive for anatomic reduction and stable fixation of such a complex injury.

Clinical and radiographic evaluation

The association of femoral neck fractures in the young with high-energy trauma mandates a thorough evaluation for associated injuries and adherence to advanced trauma life support (ATLS) protocols [5, 11]. Femoral neck fractures occur in the setting of femoral shaft fractures two to six percent of the time, but are initially missed in as many as 30 % of those combined injuries [12]. Patients present with an externally rotated and shortened lower extremity [13].

Radiographic workup consists of full-length plain radiographs of the femur in the anteroposterior and lateral planes [14]. A cross-table lateral is preferable in the setting of acute trauma to the hip. An anteroposterior view of the pelvis should be included [13].

The Garden and Pauwels’ classifications are the most commonly utilized systems. In the Garden classification, four types are described by degree of displacement. Type I is valgus-impacted or an incomplete fracture. Type II is complete and non-displaced. Type III is complete and partially displaced. Type IV is completely displaced [15].

Pauwels’ classification describes the angle of the fracture with respect to the horizontal. Type I is <30°; type II 30°–70°; and type III >70° [16]. In practice, the inter- and intraobserver reliabilities of both systems are sufficiently low that fractures are grouped into non-displaced and displaced variety to help guide treatment decisions [17].

Various radiographic findings should be considered. A high Pauwel’s angle (>50°) is associated with posteroinferior comminution in as many as 96 % of cases. They are also associated with major fracture plane obliquity and loss of calcar integrity [18]. These fracture patterns present an increased risk of nonunion, malunion, avascular necrosis, and early failure [16, 19–21].

Treatment options and considerations

Once other life- and limb-threatening injuries have been addressed, expedient management of femoral neck fractures in the young patient should be undertaken. Recent literature has failed to demonstrate that mild delays (>48 h) in operative intervention increase the risk of AVN or nonunion [9, 22–24]. These findings, however, are in the context of previous studies documenting higher rates of avascular necrosis with delays in surgical fixation [6, 25]. Salvage options in the young patient are not tolerated as well as in the elderly population and thus maximizing the probability of maintaining a native hip joint without altered biomechanics is a priority [5, 10].

In the young patient, internal fixation is the primary mode of treatment. An anatomic reduction is mandated by either closed or open means. Multiple previous investigations have demonstrated that a non-anatomic reduction increases the risk of lower functional outcome, healing complication and reoperation [9, 26–29]. Specifically, varus malreduction and inferior offset are risks of failure [28, 29]. Minimal valgus alignment has not been shown to have a deleterious effect on outcome [30].

Surgical approach

There are many possible surgical tactics for fracture visualization and reduction. We believe that an anatomic reduction in the femoral neck and subsequent stable internal fixation is the most important goals of surgical treatment of these injuries. The surgical approach and choice of implant go hand in hand. Some implants cannot be placed through certain open approaches to the hip; therefore, the choice of approach and implant must be part of a thorough and thoughtful preoperative plan. For instance, sliding hip screw (SHS) constructs cannot be placed through a direct anterior (Smith-Petersen) approach, so an additional approach to the lateral femur is necessary for hardware placement if this type of implant is selected. One advantage to the anterolateral (Watson-Jones) approach is that it allows visualization and reduction in most basi-cervical and trans-cervical femoral neck fractures as well as access to the lateral femur through the same incision. Some authors believe that visualization of the subcapital region of the femoral neck through the Watson-Jones approach can be limited, but the benefits of a single incision for fracture reduction and hardware placement make this an attractive option for the surgeon comfortable with this approach [9].

Our preferred approach is the direct anterior (Smith-Petersen), an internervous approach between the femoral nerve and superior gluteal nerve territories. This approach provides excellent visualization of the entire femoral neck for fracture reduction. The patient is positioned supine on a radiolucent flat-top table after adequate anesthesia has been achieved. A small bump is placed under the affected flank to elevate the operative hip to allow easier visualization with fluoroscopy, which comes in from the opposite side of the table. The ipsilateral upper extremity may be secured across the patient’s chest or positioned on an arm board. In this “bumped” position, the femoral anteversion is compensated for by the interna, rotation of the patient’s hemipelvis. That is, a true AP image of the femoral neck is obtained when the C-arm is in a vertical position, and a true lateral of the proximal femur can be obtained by rolling the C-arm under the table 90°. If the patient were positioned flat on the operating table without a bump, the C-arm must “roll over” approximately 15° to account for femoral anteversion in order to get a true AP view of the femoral neck, and a lateral view of the proximal femur can be obstructed by the contralateral thigh.

A 12- to 15-cm skin incision begins approximately 2 cm lateral and 1 cm distal to the ASIS and is carried distally toward the lateral aspect of the knee (Figs. 1, 2). The skin and subcutaneous tissues are incised sharply, taking care to identify and protect the fascia. A lap sponge is used to clear the fascia of any remaining subcutaneous fat (Fig. 3). The lateral femoral cutaneous nerve is not routinely identified, but it exits beneath the inguinal ligament and would be found in the tissues medial to the Smith-Petersen approach. The “blue line” is identified in the fascia, which is the border between tensor fascia lata (TFL) and sartorius. A new knife is used to lightly incise through this fascia just lateral to the blue line (Fig. 4). An Allis clamp is used to secure and elevate the medial edge of the fascial incision, and blunt digital dissection is performed to deepen the interval between sartorius and TFL. The next step is identification and protection of the ascending branch of the lateral femoral circumflex artery. In arthroplasty cases utilizing the direct anterior approach, this artery is typically controlled with electrocautery or ligation, but in cases where viability of the femoral head is of utmost importance, every attempt should be made to preserve this contribution to the blood supply of the femoral head. It is typically found in the midportion of the incision (3–4 branches crossing perpendicular to the incision), and blunt dissection will aid in its identification and preservation.

Fig. 1
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Schematic drawing of the direct anterior (Smith-Petersen) approach to the hip; ASIS denoted by dashed circle

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Fig. 2
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Skin incision begins ~2 cm lateral and 1 cm distal to the ASIS and extends distally for 12–15 cm toward the lateral aspect of the knee

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Fig. 3
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Fascia is identified and cleared of subcutaneous fat

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Fig. 4
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Fascia is identified and incised just lateral to the interval between sartorius and TFL

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The internervous plane is then deepened between gluteus medius (superior gluteal nerve) and rectus femoris (femoral nerve) (Fig. 5). Two cobra retractors are placed, one above and one below the femoral neck (extra capsular). A Cobb and lap sponge can be used to clear any remaining tissue off the anterior surface of the joint capsule, which will be between the two cobra retractors. The reflected head of the rectus femoris will occasionally obstruct the surgeon’s view of the capsule, and it can be sharply taken down from its origin on the AIIS to improve visualization. There is typically a substantial intra-articular hematoma which can distend the capsule giving it a “tense” feeling. A “T”- or “L”-shaped capsulotomy is made sharply through the anterior capsule, with the long limb of the capsulotomy in line with the femoral neck and the other limb along the capsule–labral junction. The hematoma is evacuated. The capsule can be tagged with heavy suture to aid with elevation and retraction of the capsule as it is dissected free from the femoral neck. The 2 cobra retractors are then re-positioned inside the capsule, one above and one below the femoral neck, giving an excellent view of the entire femoral neck and fracture (Fig. 6). External rotation of the leg can assist with elevation of the capsule along the infero-medial neck toward the lesser trochanter, which is essential for placement of a medial buttress plate, if used.

Fig. 5
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Interval between gluteus medius and rectus femoris is developed, exposing the anterior joint capsule. Hibbs retractors can be used for soft tissue retraction

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Fig. 6
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Once the capsulotomy has been made, the cobra retractors can be placed within the capsule, providing a view of the femoral neck fracture

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The role of capsulotomy continues to be controversial. Multiple studies have demonstrated increases in intracapsular pressures with femoral neck fractures with improvement after aspiration or capsulotomy and resultant increases in osseous perfusion pressure [31–33]. However, in a large series Haidukewych et al. [9] failed to demonstrate any outcome differences in patients who did or did not undergo capsulotomy at the time of fixation. Ly and Swiontkowski [13] reviewed the management of young femoral neck fractures in 2008 and highlighted that clinical studies did not readily demonstrate an association between capsulotomy and rates of AVN. We do not routinely perform percutaneous capsulotomies in this injury pattern; however, in the setting of displaced femoral neck fracture rarely do we feel comfortable obtaining an anatomic reduction without an open approach, and thus, a capsulotomy is generally performed as part of the approach.

Reduction technique

Once the fracture has been exposed, the fracture edges are cleared of fracture hematoma. Often, high-energy femoral neck fractures in young adults will have a high Pauwels angle, making them particularly unstable to shear forces (Fig. 7). Depending on the level and obliquity of the fracture, a Schanz pin or large K-wire may be placed just lateral to the articular cartilage (Fig. 8). A combination of internal rotation of this K-wire in conjunction with external rotation of the leg will book open the fracture sufficiently to allow all debris to be cleared from the fracture site. This maneuver can be reversed (external rotation of the K-wire and internal rotation of the leg) to affect a provisional reduction. Fractures with minimal comminution will have good cortical read of the reduction along the inferior margin of the femoral neck. If additional reduction maneuvers need to be employed, a small incision over the lateral aspect of the greater trochanter will allow a ball-spiked pusher to be introduced in a percutaneous fashion against the lateral cortex of the proximal femur (Fig. 8). This tool can hold the reduction, while additional K-wires are placed for provisional stabilization. Additionally, a bone hook or similar instrument may be placed over the anterior portion of the femoral neck to provide a laterally directed counter force against the ball-spiked pusher. A more direct reduction technique may be utilized which involves the use of two 3.5-mm cortex screws and the Farabeuf reduction clamp. The two screws are placed bi-cortically on either side of the fracture and measured long to allow ~5 mm of the screw head to sit prominently such that it can be grasped by the Farabeuf clamp (Fig. 9). Securing the clamp to both screw heads allows varying degrees of compression as well as rotation to be applied across the fracture. Once an anatomic reduction has been achieved and confirmed under direct vision and fluoroscopically, the fracture can be provisionally held in the reduced position with multiple K-wires.

Fig. 7
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Determination of the Pauwels angle. The long axis of the femur is marked, and a perpendicular line to this is drawn. The angle formed by the fracture and this perpendicular line is the Pauwels angle

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Fig. 8
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Intraoperative fluoroscopic view demonstrating a Schanz pin in the proximal fragment and a ball-spiked pusher placed in a percutaneous fashion to affect a reduction in the femoral neck. A K-wire can be placed for provisional stabilization

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Fig. 9
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Lateral view showing a Farabeuf reduction clamp placed over two 3.5-mm screws for a direct reduction in the femoral neck fracture. AP view demonstrates final fixation with partially threaded lag screws

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Fixation strategies

The choice of internal fixation will determine the next steps in the case. If cannulated lag screw fixation is chosen, the guide wires can be placed through a small incision over the lateral aspect of the proximal femur without a formal approach. To minimize stress riser formation, care should be taken to avoid placing the starting point of these screws below the level of the lesser trochanter [34]. Partially threaded 6.5- or 7.3-mm cannulated screws are typically placed in an inverted triangle configuration, with the screws abutting the endosteal cortex to provide the most stable fixation possible [35–37]. A divergent or parallel pattern has been shown to be biomechanically superior to a convergent pattern [37]. Inverted triangle pattern may also reduce the risk of subtrochanteric fracture after fixation [38]. Other biomechanical studies have suggested that the addition of a fourth screw may improve fixation strength in cases with posterior comminution [39]. Similarly, in high-risk patterns (i.e., Pauwels type III), utilizing a trochanteric lag screw (Fig. 10) has been shown to be biomechanically superior when compared to an inverted triangle pattern [40]. The use of washers in the setting of cancellous screws improves compression forces [41].

Fig. 10
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Intraoperative fluoroscopic views demonstrating placement of a trochanteric lag screw placed perpendicular to the fracture plane. An infero-medial buttress plate was placed as supplementary fixation

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If a sliding hip screw construct is chosen, a direct lateral approach to the proximal femur is performed for hardware placement. A separate screw placed above the sliding hip screw can serve as an anti-rotation device and confer additional fracture stability from improved biomechanical strength [20]. Increased torsional stress may contribute to higher rates of avascular necrosis after SHS fixation in some studies, highlighting the importance of de-rotation pin and/or screw use [42]. From a technical standpoint, the surgeon should strive for a tip–apex distance of less than 25 mm to prevent screw cutout and placement of the lag screw in the inferior portion of the neck to abut the cortex [43].

When considering the implant selection, the specific fracture pattern must be considered. Biomechanical studies have suggested that for highly unstable fracture patterns (Pauwels type III, basi-cervical and highly comminuted fractures), a SHS construct may confer greater stability to resist shear forces than cancellous screws [19, 44–46]. However, recently Stockton et al. [47] noted an increase in femoral neck shortening after fixation with SHS when compared to cancellous screw fixation. The functional impact in that study was unclear, though shortening has been shown in older patients to decrease functional outcomes and alter biomechanics [48]. Supplementary fixation such as an infero-medial buttress plate may be placed after primary fixation. External rotation of the hip will allow dissection along the inferior femoral neck toward the lesser trochanter. A 1/3 tubular plate is then contoured to fit and secured with 3.5-mm cortical screws (Figs. 10, 11). The addition of an infero-medial plate has been shown to result in a biomechanically stiffer and stronger construct than either cannulated screws or a SHS alone [49, 50].

Fig. 11
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Once the fracture has been reduced and stabilized, external rotation of the hip can be performed for placement of an infero-medial buttress plate

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Discussion

Femoral neck fractures in the young adult represent a high-risk injury with the potential for significant complications. There remains a paucity of high-level prospective literature guiding the management of these injuries. Specifically, prospective comparative literature is lacking regarding (1) open versus closed reduction, (2) SHS versus cannulated screws, (3) the timing of operative intervention, and (4) the role of capsulotomy. The Fixation using Alternative Implants for the Treatment of Hip Fractures (FAITH) trial is currently ongoing as a multicenter prospective, randomized study comparing cancellous screw fixation to SHS fixation, adding to the body of literature on this topic.

Despite these limitations, several patterns emerge from the available literature. To reduce the risk of both nonunion and avascular necrosis while maximizing functional outcome, an anatomic reduction must be obtained with stable fixation [9, 26–29]. High-risk fractures (i.e., vertical shear or comminuted) carry a higher risk of complication, and supplemental fixation should be considered in these patterns [16, 18, 20, 21, 40, 49].

Patients should be counseled on the nature of these injuries. Meta-analyses and multiple studies have demonstrated consistent complication rates: an avascular necrosis rate of ~15–25 %, nonunion rate just under 10 %, and a re-operation rate approaching 20 % [5, 8–11, 22]. From the available literature, the key to a successful clinical outcome is the maintenance of the native femoral head free of avascular necrosis. Haidukewych et al., Krischak et al. and Broos et al. demonstrate that the majority of patients who meet these criteria maintain good to excellent functional outcomes.

Summary

  • Expedient ORIF is the treatment of choice for the young adult patients with a displaced femoral neck fracture.

  • Anatomic reduction and stable fixation reduce the risk of AVN, nonunion, and other complications.

  • Surgical approach dictated by surgeon preference and implant selection.

  • Fixation strategy dictated by fracture pattern and degree of instability.

  • Supplemental fixation has biomechanical benefit.

  • Outcome is driven by union without avascular necrosis.

  • Further prospective studies needed.