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Introduction

The etiology of sciatic nerve entrapment can be diverse and may occur in one or more locations within the deep gluteal space. The suggested term to describe the clinical manifestation of these various points of nervous compressive pathology is deep gluteal syndrome (DGS) [1]. Of utmost importance to the diagnosis of DGS, is the exclusion of other sources of sciatica, most commonly the lumbar spine. Sources of posterior hip pain can mimic sciatica; however, a comprehensive history and physical examination of the hip will guide the examiner toward a differential diagnosis (covered in Chap. 7, “Physical Examination of the Hip and Pelvis”). The entire extrapelvic course of the sciatic nerve within the deep gluteal space can be assessed via an endoscopic surgical technique, allowing the diagnosis and treatment of the causes of DGS. The experienced surgeon must have a detailed understanding of the anatomy and biomechanics of all four layers of the hip joint and their interrelationships to accurately supply a comprehensive diagnosis and treatment plan (covered in Chap. 7, “Physical Examination of the Hip and Pelvis”). The open transgluteal approach has been described to effectively perform piriformis muscle resection and neurolysis of the sciatic and posterior femoral cutaneous nerves [2, 3]. Open operative treatment has been successful in a number of case studies [2, 4, 5]. Additionally, neurolysis of the sciatic nerve near the hamstrings origin at the level of the ischial tuberosity has been performed with satisfactory results [5]. Table 1 is a summary of open technique results for treatment of sciatic nerve entrapment.

Table 1 Summary of published results of open decompression of the sciatic nerve
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Endoscopic Decompression

Endoscopy is an effective approach for the treatment of deep gluteal syndrome [15]. Advantages of endoscopy include minimally invasive procedure, magnified view of the sciatic nerve, and potential to evaluate the entire deep gluteal space from the sciatic notch to the proximal thigh, including sciatic nerve biomechanics. Dezawa et al. first reported on six cases of endoscopic piriformis muscle release [16]. Martin et al. reported an endoscopic technique for sciatic nerve decompression in 35 patients presenting with deep gluteal syndrome [15], and this technique has been utilized internationally [17].

The supine technique is utilized and modified by positioning the orthopedic table in maximal contralateral patient tilt. The supine position, as opposed to prone, allows for manual manipulation of the lower limb at the knee and hip joints for the full assessment of sciatic nerve kinematics. A relative contraindication for sciatic nerve decompression in this supine technique is knee recurvatum, considering the increased strain on the sciatic nerve. Nerve conduction and EMG are usually monitored intraoperatively and can demonstrate immediate improvement or change post-release. Mild acute changes in nerve conduction during the course of surgery may be observed due to fluid accumulation over time. For deep gluteal space visualization, a 70° high-definition long arthroscope with adjustable and lengthening cannulas is utilized [15]. The cannulas are opened to maintain the fluid flow, when utilizing the radiofrequency probe [18]. Fluid pressure is set to 60 mmHg with intermittent pressure increases up 80 mmHg. Three portals are utilized: anterolateral, posterolateral, and an auxiliary posterolateral portal positioned 3 cm posterior and 3 cm superior to the greater trochanter (Fig. 1) [15, 19]. Frequent use of intraoperative fluoroscopy will confirm the proper location of the endoscopic view.

Fig. 1
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Portal placement. (a) Use of long scopes from the anterolateral (AL) portal and shaver through the posterolateral (PL) portal. APL auxiliary posterolateral portal. (b) The arthroscope can be also positioned in the auxiliary posterolateral portal (APL) during the procedure (Reprint with permission TIO [19])

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A “10-step technique” allows for a complete sciatic nerve assessment and safe nerve decompression in the deep gluteal space. The starting position [20] is shown in Fig. 2, and once orientation has been established, the arthroscope is rotated to allow proximal viewing. Step 1: Inspect the peritrochanteric space and perform a greater trochanteric bursectomy [21], utilizing the anterolateral and posterolateral portals with the hip in neutral position (Fig. 3). Utilize the arthroscopic shaver for the bursectomy, releasing fibrous bands until the quadratus femoris is identified. Replace the shaver with the blunt probe and release any fibrous bands at the level of the quadratus femoris. Step 2: Identify the quadratus femoris muscle and the sciatic nerve with the hip in internal rotation (Fig. 4). Step 3: Evaluate the sciatic nerve color, epineural blood flow, epineural fat, and nerve motion. Normal sciatic nerve appearance (Fig. 5a) will have noticeable epineural blood flow and epineural fat and normal motion with internal/external rotation gliding along the border of the external rotator muscles. An abnormal sciatic nerve (Fig. 5b) will appear white resembling a shoestring and will not move with rotation and feel tight with probing. With deep hip flexion and external rotation, check for greater trochanteric impingement (Fig. 5c). In cases of sciatic nerve entrapment by the greater trochanter or ischium, greater trochanteric osteoplasty or osteotomy may be a consideration. Step 4: Identify the vascular branches penetrating the sciatic nerve anteriorly just proximal to the quadratus femoris muscle (Fig. 6a). These branches originate from inferior gluteal artery, medial circumflex, and first perforating femoral artery and may sometimes reach the sciatic nerve on its posterior surface (Fig. 6b). Step 5: Endoscopic neurolysis of the sciatic nerve. This step requires gentle dissection of the fibrous bands in the area of the nerve along its course in the deep gluteal space. Utilize a blunt probe for dissection while probing the sciatic nerve to protect the perineural sheath. Some fibrous bands may extend down from the greater trochanteric bursa to the sciatic nerve [15]. Fibrovascular scar bands are often present, which will require cauterization prior to release, utilizing arthroscopic scissors. In cases when the fibrovascular bands are thick and clustered, resembling a bird’s nest, combinations of cauterization and ligature may be necessary [15]. Step 6: Rotate the arthroscope for distal viewing and inspect the sciatic nerve at the ischial tunnel, hamstring origin, and sacrotuberous ligament (Fig. 7), releasing any fibers from the sciatic nerve. Step 7: Rotate the arthroscope for proximal viewing and identify the obturator internus muscle and tendon (Fig. 8). Release fibrous bands and probe and check for the relation between the sciatic nerve and obturator internus tendon, which may penetrate the sciatic nerve. Step 8: Move the long scope to the auxiliary or posterolateral portal when required (usually in larger patients). Identify the branch of the inferior gluteal artery, which crosses posterior to sciatic nerve distal to the border of the piriformis muscle. This branch must be cauterized or ligated (when larger than 2 mm using 4/0 PDS) and released before the inspection of the piriformis muscle and tendon (Fig. 9a, b). A recent study reported a mean distance of 8 mm (4–14 mm) between the sciatic nerve and the crossing branch of the inferior gluteal vessel [18]. The same study evaluated the fluid temperature during activation of a monopolar radiofrequency device around the sciatic nerve [18]. The temperature profile was safe to the sciatic nerve during the tested activation times of 3, 5, and 10 s (Tables 2 and 3). The standard approach to vessel cauterization is a? three-second interval of radiofrequency activation, maintaining continuous irrigation. Ten seconds is three times longer than standard activation time. For vessels larger than 2 mm, a ligature (Fig. 10) is utilized rather than longer activation time. Step 9: Identify and resect the piriformis muscle and tendon. The tendon is often hidden under the belly of the muscle which will require probing under the piriformis or shaving the distal border if necessary. The utilization of arthroscopic scissors for tendon release pulling the scissors toward you adds safety and ensures that only the tendon is released (Fig. 11). Any time the shaver or scissors are utilized in the vicinity of the sciatic nerve, a curved probe can be used for sciatic nerve retraction and safety. Following tendon resection, shave the tendinous stump back 1–2 cm. Step 10: Probe the sciatic nerve for tension and look for hidden muscle or tendon branches traversing the nerve. Perform the dynamic testing of sciatic nerve kinematics probing the nerve during hip internal and external rotation with flexion and extension. Cautiously probe the sciatic nerve up to the sciatic notch and confirm the location with fluoroscopy. Carefully note that the superior gluteal neurovascular structures exit the sciatic notch superior to the piriformis muscle. Using the curved probe, thoroughly explore the retrosciatic region to identify and release any ancillary musculotendinous branches that may be binding the nerve (Fig. 12). Internal and external rotation of the hip is helpful to identify these branches. Any restriction of nerve motion should suggest a penetrating branch, intrapelvic entrapment, or osseous abnormality.

Fig. 2
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Starting position and orientation. Establish orientation within the peritrochanteric space based upon anatomical landmarks. The 70° arthroscope is initially looking distal, oriented like a flag with the light cord proximal along with the lens focus distal (Reprint with permission from Slack Inc. [20])

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Fig. 3
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The first step of the deep gluteal space endoscopy includes the greater trochanteric bursectomy. The bursa and fibrous bands are resected utilizing a shaver before identifying the quadratus femoris muscle. GT greater trochanter

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Fig. 4
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Identification of the quadratus femoris muscle and sciatic nerve. (a) Internal rotation of the hip allows the visualization of the quadratus femoris muscle (QF) and sciatic nerve (SN). (b) Focused view of the sciatic nerve and quadratus femoris muscle

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Fig. 5
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Sciatic nerve inspection. (a) Normal sciatic nerve appearance with presence of blood flow and epineural fat. (b) Abnormal sciatic nerve with white shoestring appearance and no epineural fat. (c) Assessment of sciatic nerve (SN) compression between the greater trochanter (GT) and ischium

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Fig. 6
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Inspection of the vascular supply to the sciatic nerve. (a) Vascular supply (open arrow) reaching the sciatic nerve (SN) on its anterior surface. (b) Vessel accessing the sciatic nerve posteriorly (arrow)

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Fig. 7
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Distal view of the deep gluteal space

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Fig. 8
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Proximal view of the deep gluteal space. (a) The inspection of the sciatic nerve (SN) includes a gentle probing of the nerve. OI/Gem: obturator internus/gemellus. (b) Identification of the obturator internus tendon (OI). Sciatic nerve (SN) with normal appearance. (c) Abnormal sciatic nerve appearance at the level of the obturator Internus/gemellus (OI/Gem). FB fibrous scar band

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Fig. 9
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(a) Proximal view with identification of a branch of the inferior gluteal artery (BIGA), which crosses posteriorly the sciatic nerve (SN). (b) Cauterization of the crossing branch (arrow) of the inferior gluteal artery utilizing a radiofrequency device

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Table 2 Temperature assessed at the sciatic nerve after different times of continuous probe activation
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Table 3 Fluid temperature assessed at the sciatic nerve at different intervals of distance and duration
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Fig. 10
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Ligature of a vessel in a fibrovascular scar band. For vessels larger than 2 mm, a ligature is utilized rather than of long periods of radiofrequency activation

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Fig. 11
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Piriformis tendonotomy. PI piriformis muscle and tendon, SN sciatic nerve

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Fig. 12
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(a) Cautious palpation of the sciatic nerve (SN) at the sciatic notch (open arrows) utilizing fluoroscopic guidance to confirm location. (b) Ancillary musculotendinous branch through the sciatic nerve identified after the resection of the posterior head of the piriformis muscle

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A standardized technique and surgical experience for diagnosis and sciatic nerve decompression are mandatory in order to identify the sciatic nerve anatomy, to avoid iatrogenic injury, and to not overlook potential sources of sciatic nerve entrapment.

Physical Therapy

Critical to the outcomes of endoscopic sciatic nerve decompression is the physical therapy rehabilitation and patient compliance. The goal of rehabilitation is to gain mobility and maintain movement of the hip joint. Patients feel much better after surgery and may want to take an aggressive approach regarding stretching and rehabilitation. However, stretch injury can cause neuropraxia and neuralgia. Six to twelve percentage increased in nerve stretch can cause decreased nerve conduction [22, 23]. To avoid overstretch injury, the Ilizarov osteogenesis principles of limb lengthening can be applied to rehabilitation by a slow progression of increased stretching. Kinematic motion of the sciatic nerve with knee flexion is different than with knee extension. This factor is important to understand in physical therapy principles. The following is an outline for postoperative sciatic nerve decompression rehabilitation.

Full circumduction of the hip with knee flexion can begin on day one. A knee brace is used to avoid knee extension and maintain a relaxed sciatic nerve when necessary. The utilization of the knee brace is dependent upon the strain of the sciatic nerve, which is influenced by degree of femoral anteversion and the number of sites of entrapment. If increased tension is noticed postoperatively, the knee is locked at 45° for 3 weeks applying only nerve glides and circumduction. After week four, increase up to 10° of knee extension every two weeks as tolerated. Maintain circumduction, gentle nerve glides, and include stretching maneuvers aimed at the external rotators (Fig. 13). The piriformis stretch involves placing the hip in flexion, adduction, and internal rotation. In a seated position, the patient brings the knee into the chest and across midline and pulls the knee to the opposite shoulder for 20 seconds. Gradually progress the stretching by increasing duration and intensity until a maximal stretch is obtained. Standard physical therapy protocol can begin as early as 4 weeks. Again, a word of caution in cases of previous abdominal surgery and femoral retroversion as strain parameters will be a dependent factor and the nerve may be impinged in more than one location. The therapist should be diligent in recognizing these potential outcome factors.

Fig. 13
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Rehabilitation stretching exercises. (a) The piriformis stretch is performed in the seated position. The patient brings the knee toward the opposite shoulder. (b) Sciatic nerve glides: the patient first performs cervical extension and plantar flexion of the ankle followed by cervical flexion with ankle dorsiflexion. (c) Hip circumduction: performed in supine position with gentle passive circular movements, with knee and ankle parallel to the body longitudinal axis (avoiding hip rotation)

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The use of steroidal and nonsteroidal anti-inflammatories has been found useful after day two. Additional physical therapy techniques may be helpful including ultrasound and electrical stimulation. With a proper rehabilitation protocol, good to excellent outcomes can be achieved. The advancement in rehabilitation may prove beneficial to improve the outcomes of endoscopic sciatic nerve decompression in some patients.

Results

Martin et al. reported on a case series of 35 patients presenting with deep gluteal syndrome [15]. Average duration of symptoms was 3.7 years with an average preoperative verbal analog score of 7, which decreased to 2.4 postoperatively. Preoperative modified Harris Hip Score was 54.4 and increased to 78 postoperatively. Twenty-one patients reported preoperative use of narcotics for pain; 2 remained on narcotics postoperatively (unrelated to initial complaint). Eighty-three percent of patients had no postoperative sciatic sit pain (inability to sit for >30 min) [15]. Five patients experienced low mHHS scores and modest pain relief postoperatively. This poor outcome group is shown in Table 4 and may be related to femoral retroversion and previous abdominal surgery.

Table 4 Characteristics of five low-improvement cases
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Now, among 200 national and international cases, complications continue to be extremely low. It is very important to assess acetabular and femoral version which has an effect on sciatic nerve biomechanics. To help avoid postsurgical stretch injury, it is recommended that intra-articular work be performed separately from extra-articular work. Due to the length of time from diagnosis to treatment and recovery, the psychological toll of the pain cycle can be frustrating. Psychological testing can be helpful pre and post-operatively. Participation in a pain reinforcing group is not recommended and may be a negative outcome predictor. Complications have involved hematoma brought on by early postoperative use of NSAIDs with excessive postoperative activity. Concomitant pudendal nerve and sciatic nerve complaints are often resolved; however, in two cases the pudendal complaints worsened.

Summary

The “10-step technique” for the deep gluteal space provides a standardized approach to sciatic nerve assessment and decompression. This endoscopic approach appears useful in detecting sciatic nerve pathology and treatment, and further studies are underway. By understanding the anatomy and biomechanics and applying clinical tests and diagnostic strategies, adequate treatment of all four layers can be obtained as a part of a comprehensive plan of treatment and rehabilitation.