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The Endoscopic Treatment of Sciatic Nerve Entrapment/Deep Gluteal Syndrome

Published:November 12, 2010DOI:https://doi.org/10.1016/j.arthro.2010.07.008

      Purpose

      The purpose of this study was to investigate the historical, clinical, and radiographic presentation of deep gluteal syndrome (DGS) patients, describe the endoscopic anatomy associated with DGS, and assess the effectiveness of endoscopic surgical decompression for DGS.

      Methods

      Sciatic nerve entrapment was diagnosed in 35 patients (28 women and 7 men). Portals for inspection of the posterior peritrochanteric space (subgluteal space) of the hip were used as well as an auxiliary posterolateral portal. Patients were treated with sciatic nerve decompression by resection of fibrovascular scar bands, piriformis tendon release, obturator internus, or quadratus femoris or by hamstring tendon scarring. Postoperative outcomes were evaluated with the modified Harris Hip Score (MHHS), verbal analog scale (VAS) pain score, and a questionnaire related specifically to sciatic hip pain.

      Results

      The mean patient age was 47 years (range, 20 to 66 years). The mean duration of symptoms was 3.7 years (range, 1 to 23 years). The mean preoperative VAS score was 6.9 ± 2.0, and the mean preoperative MHHS was 54.4 ± 13.1 (range, 25.3 to 79.2). Of the patients, 21 reported preoperative use of narcotics for pain; 2 continued to take narcotics postoperatively (unrelated to initial complaint). The mean time of follow-up was 12 months (range, 6 to 24 months). The mean postoperative MHHS increased to 78.0 and VAS score decreased to 2.4. Eighty-three percent of patients had no postoperative sciatic sit pain (inability to sit for >30 minutes).

      Conclusions

      Endoscopic decompression of the sciatic nerve appears useful in improving function and diminishing hip pain in sciatic nerve entrapment/DGS.

      Level of Evidence

      Level IV, therapeutic case series.
      Originating from the ventral rami of L4 to S3, the sciatic nerve roots form a single trunk within the pelvis and exit through the sciatic notch inferior to the piriformis muscle. Covered by the gluteus maximus within the deep gluteal region, the sciatic nerve passes between the ischial tuberosity and the greater trochanter lying close to the posterior capsule of the hip joint.
      • Clemente C.
      Gray's anatomy: Anatomy of the human body.
      The sciatic nerve innervates the hamstring group of muscles.
      • McCrory P.
      • Bell S.
      Nerve entrapment syndromes as a cause of pain in the hip, groin and buttock.
      Proximal to the piriformis are the superior gluteal and inferior gluteal nerves. Distal to the piriformis are the nerve to the quadratus femoris/gemellus inferior and the nerve to the obturator internus/gemellus superior.
      • Clemente C.
      Gray's anatomy: Anatomy of the human body.
      In a cadaveric study by Miller et al.,
      • Miller S.L.
      • Gill J.
      • Webb G.R.
      The proximal origin of the hamstrings and surrounding anatomy encountered during repair A cadaveric study.
      the sciatic nerve was located at a mean of 1.2 ± 0.2 cm from the most lateral aspect of the ischial tuberosity, and the proximal origin of the hamstrings was found to have an intimate relation with the inferior gluteal nerve and artery and sciatic nerve. With hip flexion, the sciatic nerve experiences a proximal excursion of 28.0 mm.
      • Coppieters M.W.
      • Alshami A.M.
      • Babri A.S.
      • Souvlis T.
      • Kippers V.
      • Hodges P.W.
      Strain and excursion of the sciatic, tibial, and plantar nerves during a modified straight leg raising test.
      Under normal conditions, the sciatic nerve is able to stretch and glide to accommodate moderate strain or compression associated with joint movement.
      Patients presenting with sciatic nerve entrapment often have a history of trauma and symptoms of sit pain (inability to sit for >30 minutes), radicular pain of the lower back or hip, and parasthesias of the affected leg.
      • Benson E.R.
      • Schutzer S.F.
      Posttraumatic piriformis syndrome: Diagnosis and results of operative treatment.
      The sciatic nerve can be trapped above (central) or below (peripheral) the gluteal region; therefore, the spine must be excluded as the source of entrapment. Physical examination tests that have been advocated for the clinical diagnosis of sciatic nerve entrapment include passive stretching and active contraction tests. The Lasègue sign is pain with straight–leg raise testing (to 90° hip flexion).
      • Freiberg A.H.
      Sciatic pain and its relief by operations on muscle and fascia.
      • Freiberg A.H.
      • Vinke T.H.
      Sciatica and the sacroiliac joint.
      The Pace sign is pain and weakness with resisted abduction and external rotation of the hip.
      • Pace J.B.
      • Nagle D.
      Piriform syndrome.
      The Freiberg sign is pain with internal rotation of the extended hip.
      • Freiberg A.H.
      Sciatic pain and its relief by operations on muscle and fascia.
      • Freiberg A.H.
      • Vinke T.H.
      Sciatica and the sacroiliac joint.
      A variant of the Freiberg test involves flexion, adduction, and internal rotation of the hip.
      • Benson E.R.
      • Schutzer S.F.
      Posttraumatic piriformis syndrome: Diagnosis and results of operative treatment.
      • Papadopoulos E.C.
      • Khan S.N.
      Piriformis syndrome and low back pain: A new classification and review of the literature.
      Etiologies of sciatic nerve entrapment are fibrous bands containing blood vessels
      • Adams J.A.
      The pyriformis syndrome—Report of four cases and review of the literature.
      • Vandertop W.P.
      • Bosma N.J.
      The piriformis syndrome A case report.
      and gluteal,
      • McCrory P.
      • Bell S.
      Nerve entrapment syndromes as a cause of pain in the hip, groin and buttock.
      piriformis,
      • Benson E.R.
      • Schutzer S.F.
      Posttraumatic piriformis syndrome: Diagnosis and results of operative treatment.
      • Vandertop W.P.
      • Bosma N.J.
      The piriformis syndrome A case report.
      or hamstring muscles.
      • Puranen J.
      • Orava S.
      The hamstring syndrome A new diagnosis of gluteal sciatic pain.
      Given the variation of anatomic entrapment, it has been suggested that the term “deep gluteal syndrome” (DGS) be used because entrapment of the sciatic nerve may occur from any of the gluteal region anatomy
      • McCrory P.
      • Bell S.
      Nerve entrapment syndromes as a cause of pain in the hip, groin and buttock.
      or the non-discogenic sciatica.
      • Kulcu D.G.
      • Naderi S.
      Differential diagnosis of intraspinal and extraspinal non-discogenic sciatica.
      Open techniques to correct these entrapment problems have been used.
      • Benson E.R.
      • Schutzer S.F.
      Posttraumatic piriformis syndrome: Diagnosis and results of operative treatment.
      • Vandertop W.P.
      • Bosma N.J.
      The piriformis syndrome A case report.
      Arthroscopic treatment has been described for treating piriformis syndrome
      • Dezawa A.
      • Kusano S.
      • Miki H.
      Arthroscopic release of the piriformis muscle under local anesthesia for piriformis syndrome.
      ; however, other anatomy can affect the sciatic nerve and cause entrapment. The peritrochanteric space lies adjacent to the sciatic nerve in the deep gluteal region, and the established arthroscopic portals
      • Voos J.E.
      • Rudzki J.R.
      • Shindle M.K.
      • Martin H.
      • Kelly B.T.
      Arthroscopic anatomy and surgical techniques for peritrochanteric space disorders in the hip.
      allow for the assessment of the sciatic nerve.
      The purpose of this study was to (1) investigate the historical, clinical, and radiographic presentation of DGS patients; (2) describe the endoscopic anatomy associated with DGS; and (3) assess the effectiveness of endoscopic surgical decompression for DGS. The hypothesis was that endoscopic surgical decompression is an effective treatment for DGS.

      Methods

      In a consecutive series of 650 patients evaluated and treated for intra-articular pathology between March 2006 and June 2009, descriptive data were retrospectively collected on a cohort of 35 patients with unexplained posterior hip pain. Inclusion criteria were patients with a diagnosis of DGS, confirmed with endoscopic evaluation. Exclusion criteria were patients with isolated femoroacetabular impingement or intra-articular pathology. Patients included 28 women (mean age, 48 ± 11 years; range, 20 to 66 years) and 7 men (mean age, 43 ± 11 years; range, 28 to 61 years). The mean height was 163.9 ± 9.1 cm (range, 137 to 180 cm); mean weight, 78.5 ± 19.0 kg (range, 42.3 to 120 kg); and mean body mass index, 29.2 ± 7.3 kg/m2 (range, 20.8 to 47.8 kg/m2). Each patient presented with unilateral symptomatic hip pain (21 right hips and 14 left hips). All cases underwent a history, physical and radiographic examination, magnetic resonance arthrography (MRA), and injection tests. A comprehensive back and hip physical examination ruled out the lumbar spine, sacroiliac joint, or femoroacetabular impingement as the source of the posterior hip pain. In addition, in many cases the spine was excluded as the principal source of pain by neurology consultation and magnetic resonance imaging (MRI).
      A detailed clinical history was obtained for each patient including a description of the present condition, date of onset, mechanism of injury (traumatic or nontraumatic), factors that increase or decrease pain, prior consultations, prior surgical interventions, verbal analog pain level, and narcotic use. A standard measure of hip function was obtained by the modified Harris Hip Score (MHHS).
      • Byrd J.W.
      • Jones K.S.
      Prospective analysis of hip arthroscopy with 2-year follow-up.
      Related symptoms were recorded including sit pain, night pain, back pain, and parasthesias or radicular pain. Each consecutive patient was evaluated by a single examiner using a standardized physical examination protocol.
      • Braly B.A.
      • Beall D.P.
      • Martin H.D.
      Clinical examination of the athletic hip.
      • Martin H.D.
      Clinical examination of the hip.
      • Martin H.D.
      • Kelly B.T.
      • Leunig M.
      • et al.
      The pattern and technique in the clinical evaluation of the adult hip: The common physical examination tests of hip specialists.
      Patients presenting with posterior hip pain underwent additional testing when the pain could not be explained. Additional tests included the Lasègue test, Pace test, and Seated Piriformis Stretch Test. The Seated Piriformis Stretch Test is a flexion/adduction with internal rotation test performed with the patient in the seated position (Fig 1).
      • Byrd J.W.
      • Guanche C.A.
      Clinical examination and imaging of the hip.
      The examiner extends the knee and passively moves the flexed hip into adduction with internal rotation while palpating 1 cm lateral to the ischium (middle finger) and proximally at the sciatic notch (index finger). A positive test is the re-creation of the posterior pain. All patients were evaluated by MRA,
      • Beall D.P.
      • Martin H.D.
      • Mintz D.N.
      • et al.
      Anatomic and structural evaluation of the hip: A cross-sectional imaging technique combining anatomic and biomechanical evaluations.
      • Beall D.P.
      • Sweet C.F.
      • Martin H.D.
      • et al.
      Imaging findings of femoroacetabular impingement syndrome.
      injection tests, standing anteroposterior pelvis radiographs,
      • Tannast M.
      • Siebenrock K.A.
      • Anderson S.E.
      Femoroacetabular impingement: Radiographic diagnosis—What the radiologist should know.
      and lateral radiographs.
      • Clohisy J.C.
      • Nunley R.M.
      • Otto R.J.
      • Schoenecker P.L.
      The frog-leg lateral radiograph accurately visualized hip cam impingement abnormalities.
      Measurements included neck shaft angle, center-edge angle, joint space, femoral version, and acetabular version. The clinical diagnosis of DGS considered the history, presentation, and re-creation of posterior hip pain inconsistent with intra-articular or impingement pathology.
      Figure thumbnail gr1
      Figure 1Seated Piriformis Stretch Test. The patient is in the seated position with knee extension. The examiner passively moves the flexed hip into adduction with internal rotation while palpating 1 cm lateral to the ischium (middle finger) and proximally at the sciatic notch (index finger).
      (Reprinted with permission.
      • Byrd J.W.
      • Guanche C.A.
      Clinical examination and imaging of the hip.
      )
      The peritrochanteric space was entered through the anterolateral and posterolateral portals,
      • Voos J.E.
      • Rudzki J.R.
      • Shindle M.K.
      • Martin H.
      • Kelly B.T.
      Arthroscopic anatomy and surgical techniques for peritrochanteric space disorders in the hip.
      and systematic inspection of the peritrochanteric space
      • Voos J.E.
      • Rudzki J.R.
      • Shindle M.K.
      • Martin H.
      • Kelly B.T.
      Arthroscopic anatomy and surgical techniques for peritrochanteric space disorders in the hip.
      was performed with 70° standard and long arthroscopes (Video 1, available at www.arthroscopyjournal.org). Before the peritrochanteric space, other sources of hip pathology were addressed. In 20 patients exploration of the sciatic nerve was carried out by use of the anterolateral and posterolateral portals. In a subset of 15 patients an auxiliary posterolateral portal was made 3 cm posterior and 3 cm superior to the greater trochanter (Fig 2), which allowed for better visualization of the sciatic nerve up to the sciatic notch. The kinematic excursion of the sciatic nerve (described by Coppieters et al.
      • Coppieters M.W.
      • Alshami A.M.
      • Babri A.S.
      • Souvlis T.
      • Kippers V.
      • Hodges P.W.
      Strain and excursion of the sciatic, tibial, and plantar nerves during a modified straight leg raising test.
      ) was then assessed with the leg in flexion and internal/external rotation and full extension with internal/external rotation. Inspection of the sciatic nerve began distal to the quadratus femoris and beneath the proximal end of the linea aspera insertion of the gluteus maximus to the sciatic notch. By use of a blunt probe, the sciatic nerve and vascular scar bands were inspected proximally assessing the entrapment by (1) the quadratus femoris, (2) the inferior gemellus, (3), fibrovascular scar bands, and (4) the piriformis. The impinging structures on the sciatic nerve were released by delicate dissection, and the hip range of motion was repeated to ensure adequate mobility.
      Figure thumbnail gr2
      Figure 2Auxiliary posterolateral portal placement. The anterolateral portal placement is 1 cm anterior and 1 cm superior to the greater trochanter (GT). The posterolateral portal placement is 3 cm posterior to the greater trochanter and in line with the anterolateral portal. The auxiliary portal is positioned 3 cm posterior and 3 cm superior to the greater trochanter. The course of the sciatic nerve (S) and piriformis (P) is depicted in relation to the greater trochanter and ischium.
      Postoperatively, the physical examination and MHHS were repeated. Postoperative variables of interest were the Lasègue test, Pace test, Seated Piriformis Stretch Test, MHHS (mean length of follow-up, 12 months), verbal analog pain, narcotic use, and ability to sit for more than 30 minutes. The Benson outcomes questionnaire,
      • Benson E.R.
      • Schutzer S.F.
      Posttraumatic piriformis syndrome: Diagnosis and results of operative treatment.
      a surgical outcomes rating specific to pain in the buttock or sciatic region (Table 1), was obtained in a subset of 23 patients (mean length of follow-up, 12 months). Some patients were not contacted because of an inactive phone number or their failure to respond.
      Table 1Benson Surgical Outcomes Rating
      OutcomeSymptoms
      ExcellentNo pain with prolonged periods of sitting (>30 min), strenuous activity, bending, twisting, stairs, rapid walking, jogging
      GoodNo pain with short periods of sitting (≤30 min) or daily activities or mild pain with prolonged periods of sitting or strenuous activity
      FairOccasional mild pain with short periods of sitting or normal daily activities or moderate pain with prolonged sitting or strenuous activity
      PoorSevere pain with short periods of sitting or normal daily activities, little change from preoperative level of pain associated with sciatic nerve

      Results

      The history and physical examination data are presented in Table 2, Table 3. All patients had limitations of daily living. The majority of limitations involved walking, climbing stairs, getting into or out of a car or tub, and household activities. The mean duration of symptoms was 3.7 years (range, 1 to 23 years). Twenty-one patients were taking narcotics for pain control. Women comprised 80% of the patients, and the right side was involved in 60% of the cases. Twenty patients reported the mechanism of injury to be traumatic, which involved falling and landing on hip/buttocks and lifting heavy objects. Seven patients had previous hip surgeries. Of these patients, 6 returned a mean of 1.4 years (range, 9 to 26 months) from hip arthroscopy (addressing intra-articular pathology or femoroacetabular impingement with cam and pincer surgery) and 1 required revision of an open posterior hip pain inconsistent with intra-articular pathology. Five patients had previous spine surgeries (lumbar spine fusion with discectomy), and one had a previous hip arthroscopy (6 months) and spine fusion surgery. The number of patients with related symptoms was 34 with sit pain (19 unable to sit for >30 minutes), 31 with night pain or pain awakening at night, 25 with back pain, and 26 with parasthesias or radicular pain. The mean preoperative pain level was 6.9 ± 2.0 out of a maximum pain of 10 points. The mean preoperative MHHS was 54.4 ± 13.1 (range, 25.3 to 79.2). Sixteen patients were highly active individuals who participated in sports such as running, cycling, working out at a gym, volleyball, and softball.
      Table 2Clinical Presentation of DGS in 35 Patients
      Data
      History
       Limitations of daily living (no. of patients)35
       DOS (yr)3.7
       Trauma (no. of patients)20
       Sit pain (no. of patients)34
       Unable to sit for 30 min (no. of patients)19
       Night pain (no. of patients)31
       Parasthesias/radicular pain (no. of patients)26
       Back pain (no. of patients)25
       MHHS (score out of 100)54.4
       VAS pain (scale of 1-10)6.9
      Physical examination (no. of patients)
       Tinel sign (sciatic nerve)11
       Lasègue test4
       Pace sign18
       Seated Piriformis Stretch Test12
       Hypersensitive deep tendon reflexes4
       Hyposensitive deep tendon reflexes5
       Hypoesthesia (S1, L5, L4)9
      Abbreviations: DOS, duration of symptoms; VAS, verbal analog scale.
      Table 3Physical Examination Findings
      Data
      Palpation (no. of patients)
       Tender ITB/GT17
       Tender SIJ16
       Tender ischium15
       Tender L-spine5
       Tender piriformis5
      Gait abnormalities (no. of patients)24
      Single–leg stance phase test (no. of patients)25
      Range of motion
       Hip IR (seated)17.4°
       Hip ER (seated)33.1°
       Hip flexion105.1°
       Hip abduction42.4°
       Hip adduction17.6°
      Abbreviations: ITB, iliotibial band; GT, greater trochanter; SIJ, sacroiliac joint; L-spine, lumbar spine; IR, internal rotation; ER, external rotation.
      Upon physical examination, the Pace sign was positive in 18 patients and the Seated Piriformis Stretch Test was positive in 12 patients. The Tinel sign over the sciatic nerve was positive in 11 patients, and the Lasègue test was positive in 4 patients. Parasthesias/radicular pain was present in 26 patients. Additional physical examination tests are shown in Table 2.
      The mean neck shaft angle was 135.3° with 5 patients having coxa valgus (>140° measured in center axis of rotation above greater trochanter) and 1 patient having coxa varus (<125°). The mean center-edge angle was 37.6°. The center-edge angle was less than 26° in 2 patients and greater than 42° in 8 patients. Mean femoral version was 10.4°, and mean acetabular version was 19.8°. Decreased femoral version (<10°) was present in 12 patients and increased femoral anteversion (>20°) in 6 patients. Sciatic nerve pathology was detected by MRI in 1 patient.

      Operative Findings

      Gross appearance of the sciatic nerve before decompression was observed as follows: adhesed over ischium posteriorly and inferiorly, branched with multiple branches encased in scar tissue, adhesed lateral to ischium with no excursion, hypovascular in appearance, or significantly entrapped by scar tissue. In 27 patients the greater trochanteric bursa was found to be excessively thickened with fibrous scar bands appearing to extend to near the sciatic nerve (Fig 3). The sciatic nerve was entrapped by the piriformis tendon on the nerve (Fig 4) in 18 patients. Characteristics of the piriformis muscle included split, bulging split with the sciatic nerve passing through the body, split tendon with an anterior and posterior component in which the anterior portion was released, and split into 2 distinct components with 1 dorsally and 1 inferiorly going between a bifurcated sciatic nerve. The bursal hypertrophy and scar bands were carefully and delicately excised by use of a rotary shaver, arthroscopic dissection scissors, and blunt probe. Fibrovascular scars were delicately cauterized by use of a radiofrequency probe with attention to the branches of the inferior gluteal artery lying in proximity to the piriformis muscle. The tendon can hide behind a very thin layer of muscle overlying the nerve, which was observed in the later cases. Large scar bands were present in 29 patients and extended all the way from the greater trochanter to the gluteus maximus onto the sciatic nerve and extended up to the greater sciatic notch. These scar bands were released so that the sciatic nerve had adequate excursion with internal (Fig 5A) and external (Fig 5B) rotation of the hip in flexion and extension. Pathologic characteristics of the gluteus maximus muscle included one of ropelike character and one of a subluxated gluteus maximus into a solitary scar band. In 3 patients the obturator internus muscle could be observed to be binding the sciatic nerve. In 2 patients the hamstring tendon insertion was thickened over the ischium and onto the sciatic nerve. There were no recognized complications associated with the endoscopic procedure at the time of this report.
      Figure thumbnail gr3
      Figure 3Sciatic nerve entrapment by fibrous bands. Endoscopic view of sciatic nerve (SN) entrapment by fibrous scar bands (FB).
      Figure thumbnail gr4
      Figure 4Entrapment of sciatic nerve by piriformis muscle tendon. Endoscopic view of sciatic nerve (SN) entrapment by piriformis tendon (PIR T).
      Figure thumbnail gr5
      Figure 5Sciatic nerve (SN) with internal and external rotation of hip after decompression. Endoscopic view of SN after decompression. The kinematic excursion of SN was checked with (A) internal and (B) external rotation of the hip to ensure adequate glide of the nerve.
      The mean length of postsurgical follow-up was 12 months (range, 6 to 24 months). The mean postoperative MHHS increased from 54.4 ± 13.1 to 78.0 ± 14.1 (range, 44 to 100). Patient verbal analog pain (scale of 1 to 10) decreased from 6.9 ± 2 to 2.4 ± 2.6. Postoperative narcotic use for pain control was present in 2 patients (prescribed by an outside physician for pain unrelated to the initial complaint) compared with 21 preoperatively. The physical examination tests of Lasègue and Pace and the Seated Piriformis Stretch Test were negative in all patients after endoscopic sciatic nerve decompression. All patients verbally answered that they could return to work and would have the surgery again. In addition, 83% of the patients had no postoperative sit pain and were able to sit in a chair for more than 30 minutes (1 patient reported conflicting data between the MHHS and Benson outcome). One patient had night pain. On average, women had a higher postoperative MHHS than men (81.1 v 65.4). Body mass index and activity level had no effect on outcomes. Of the 35 patients, 23 were successfully contacted by phone and interviewed with the Benson outcomes questionnaire. We did not contact the remaining patients because of an inactive phone number or the patient's failure to respond. The Benson Outcome ratings were 11 excellent, 5 good, 2 fair, and 5 poor.
      Low postoperative MHHS in conjunction with modest pain relief was present in 5 patients. Table 4 presents characteristics of these 5 low-improvement cases in an attempt to understand why these did not improve. The mean postoperative MHHS for the low-improvement cases was 53.5, compared with 83.6 for those whose condition improved. The score for postoperative verbal analog pain among the low-improvement patients was 5.5, compared with 1.8 for those that improved. All 5 had radicular complaints, with 4 of 5 showing positive radicular testing. Benson outcomes were poor in 3 patients and fair in 1 patient (1 patient could not be contacted). Three patients within this group had surgery before the utilization of the posterolateral auxiliary portal, which may have limited the ability to release the entire entrapment of the sciatic nerve. The radiographic parameters were reviewed, with 2 patients having decreased femoral version. Additional factors related to the 5 low-improvement cases included history of traumatic injury, previous surgery proximal to the hip, and multiple medical problems that could effect healing, especially in the presence of trauma to the sciatic nerve.
      Table 4Characteristics of 5 Low-Improvement Cases
      Case No.GenderTraumaDOS (mo)Surgical HistoryMHHSBORVASNSAFVPL-A PortalSN Entrapment
      PreoperativelyPostoperativelyPreoperativelyPostoperatively
      1FNo16Laparoscopy, breast53.961.6Poor681301NoSN was completely bound down in scar tissue beneath gluteus maximus and laid on top of piriformis muscle, hypovascular in appearance
      7FYes51Hysterectomy, spinal fusion, appendectomy53.944.0Poor75.513918NoThick scar tissue on anterior and posterior aspect of ischium, piriformis was involved, significant adhesions proximally and distally, fibrinous lesion over top of SN, adhesed on surface of ischium
      19FNo6Hip arthroscopy, gall bladder54.064.9N/A6513322NoLarge fibrinous bands, piriformis tendon was involved
      23MYes10None35.246.2Fair105134−1YesGT bursal hypertrophy, gluteus medius tear, SN had significant scarring and a posteriorly occurring inferior gluteal branch that tethered SN
      28MYes10Jaw, knee, tonsillectomy35.057.2Poor1041429YesMassive amount of scar tissue proximal to the quadratus femoris extending up proximal to mid hip, thickened piriformis tendon, adhesion of entire proximal aspect of SN, hypovascular, SN tethered along proximal border of quadratus up into piriformis
      NOTE. Case numbers are presented in chronologic order.
      Abbreviations: DOS, duration of symptoms; BOR, Benson outcome rating; VAS, verbal analog scale; NSA, neck shaft angle; FV, femoral version; PL-A portal, posterolateral auxiliary; SN, sciatic nerve; GT, greater trochanter.

      Discussion

      Clinical Diagnosis

      DGS
      • McCrory P.
      • Bell S.
      Nerve entrapment syndromes as a cause of pain in the hip, groin and buttock.
      involves pain in the buttock caused from entrapment of the sciatic nerve by the piriformis muscle, hamstring, obturator internus/gemellus complex, or scar tissue.
      • Benson E.R.
      • Schutzer S.F.
      Posttraumatic piriformis syndrome: Diagnosis and results of operative treatment.
      • Vandertop W.P.
      • Bosma N.J.
      The piriformis syndrome A case report.
      • Puranen J.
      • Orava S.
      The hamstring syndrome A new diagnosis of gluteal sciatic pain.
      • Cox J.M.
      • Bakkum B.W.
      Possible generators of retrotrochanteric gluteal and thigh pain: The gemelli-obturator internus complex.
      • Meknas K.
      • Christensen A.
      • Johansen O.
      The internal obturator muscle may cause sciatic pain.
      In these patients movement of the hips may cause radicular-like pain that is associated with rotation of the hip in flexion and knee extension, much like nerve root pain associated with lumbar disc disease. True piriformis syndrome is associated with buttock pain that is exacerbated by hip flexion movements combined with internal or external rotation of the affected leg. Piriformis syndrome often occurs after blunt trauma to the buttock with resultant hematoma formation and subsequent scarring between the sciatic nerve and external rotators.
      • Benson E.R.
      • Schutzer S.F.
      Posttraumatic piriformis syndrome: Diagnosis and results of operative treatment.
      The proximal origin of the hamstrings has an intimate relation with the sciatic nerve, which may be scarred into the hamstring tendons by trauma or avulsion of the hamstring.
      • Miller S.L.
      • Gill J.
      • Webb G.R.
      The proximal origin of the hamstrings and surrounding anatomy encountered during repair A cadaveric study.
      Irritation of the structures of the obturator internus/gemellus complex are commonly overlooked in association with back pain and may cause sciatica-like pain.
      • Cox J.M.
      • Bakkum B.W.
      Possible generators of retrotrochanteric gluteal and thigh pain: The gemelli-obturator internus complex.
      • Meknas K.
      • Christensen A.
      • Johansen O.
      The internal obturator muscle may cause sciatic pain.
      Our cohort of DGS patients was severely impaired for a mean of 3.7 years, with 21 taking long-term narcotics for pain. Common presenting complaints were sit pain (Fig 6), radicular pain, unable to sit for more than 30 minutes, and night pain. Patients presenting with posterior hip pain with or without radicular complaints should be evaluated for DGS when the history and physical examination suggest doing so. Women accounted for 80% of the patients, and the right side was involved in 60% of the cases. This female gender dominance and right side preference are similar to a recent case series review of sciatica without nerve root compression.
      • Yoshimoto M.
      • Kawaguchi S.
      • Takebayashi T.
      • et al.
      Diagnostic features of sciatica without lumbar nerve root compression.
      To aid in the differential diagnosis of DGS, the spine, sacroiliac joint, and femoral/acetabular pathology must be ruled out as the principal source of pain. We recommend in each case of posterior hip pain the use of a formalized physical examination of the hip that includes the Lasègue test, Pace test, and Seated Piriformis Stretch Test. The Lasègue test will alert the examiner of radicular pain; however, this test is not always positive with DGS.
      • Papadopoulos E.C.
      • Khan S.N.
      Piriformis syndrome and low back pain: A new classification and review of the literature.
      • Vandertop W.P.
      • Bosma N.J.
      The piriformis syndrome A case report.
      The Pace test is the active contraction evaluation of the piriformis muscle.
      • Pace J.B.
      • Nagle D.
      Piriform syndrome.
      A variation of the Freiberg test involves flexion, adduction, and internal rotation of the hip,
      • Papadopoulos E.C.
      • Khan S.N.
      Piriformis syndrome and low back pain: A new classification and review of the literature.
      and in all cases of post-traumatic piriformis syndrome studied by Benson and Schutzer,
      • Benson E.R.
      • Schutzer S.F.
      Posttraumatic piriformis syndrome: Diagnosis and results of operative treatment.
      maximum flexion, adduction, and internal rotation of the hip reproduced the pain. However, the exact description did not indicate the position of the knee. The Seated Piriformis Stretch Test involves adduction with internal rotation of the flexed hip with knee extension.
      • Byrd J.W.
      • Guanche C.A.
      Clinical examination and imaging of the hip.
      The familiarity with the test improved over the course of the study, because the 12 positive findings were obtained in the last 17 cases. Re-creation of the posterior pain with 1 or a combination of these tests will help in the differentiation of posterior hip pain. These tests need further sensitivity and validity testing.
      Figure thumbnail gr6
      Figure 6Typical sitting position of DGS patients. Patients presenting with DGS sit pain often adopt a single ischium load in the seated position to alleviate the hip pain.
      Evaluation of the radiographic criteria showed no correlation with DGS. With the exception of 1 case, MRA did not detect sciatic nerve pathology despite the utilization of several techniques to image the posterior peritrochanteric space. Recent interest may provide better techniques for visualization of the posterior peritrochanteric space.
      • Filler A.G.
      • Haynes J.
      • Jordan S.E.
      • et al.
      Sciatica of nondisc origin and piriformis syndrome: Diagnosis by magnetic resonance neurography and interventional magnetic resonance imaging with outcome study of resulting treatment.
      • Lewis A.M.
      • Layzer R.
      • Engstrom J.W.
      • Barbaro N.M.
      • Chin C.T.
      Magnetic resonance neurography in extraspinal sciatica.
      • Pecina H.I.
      • Boric I.
      • Smoljanovic T.
      • Duvancic D.
      • Pecina M.
      Surgical evaluation of magnetic resonance imaging findings in piriformis muscle syndrome.
      • Zhang Z.
      • Song L.
      • Meng Q.
      • et al.
      Morphological analysis in patients with sciatica: A magnetic resonance imaging study using three-dimensional high-resolution diffusion-weighted magnetic resonance neurography techniques.
      Changes in rotational osseous alignment may affect normal sciatic nerve excursion as shown in 2 of the 5 low-improvement cases with diminished femoral version. The excursion of the sciatic nerve with straight-leg hip flexion performed by Coppieters et al.
      • Coppieters M.W.
      • Alshami A.M.
      • Babri A.S.
      • Souvlis T.
      • Kippers V.
      • Hodges P.W.
      Strain and excursion of the sciatic, tibial, and plantar nerves during a modified straight leg raising test.
      did not indicate the osseous parameters of the hip, which raises the question of sciatic nerve excursion with normal versus abnormal rotational alignment.
      Open surgical techniques for the treatment of DGS have been used in reducing pain associated with entrapment of the sciatic nerve by fibrous scar bands, vascular structures, or muscular anatomy.
      • Benson E.R.
      • Schutzer S.F.
      Posttraumatic piriformis syndrome: Diagnosis and results of operative treatment.
      • Vandertop W.P.
      • Bosma N.J.
      The piriformis syndrome A case report.
      The open technique involves a skin incision starting at the posterolateral tip of the greater trochanter and carried posteriorly and proximally in a parallel direction to the gluteus maximus fibers with blunt dissection. The arthroscopic treatment using local anesthesia for piriformis syndrome has also been effective at reducing pain; however, difficulties with pain control during surgery were reported.
      • Dezawa A.
      • Kusano S.
      • Miki H.
      Arthroscopic release of the piriformis muscle under local anesthesia for piriformis syndrome.
      The portals established for the peritrochanteric space
      • Voos J.E.
      • Rudzki J.R.
      • Shindle M.K.
      • Martin H.
      • Kelly B.T.
      Arthroscopic anatomy and surgical techniques for peritrochanteric space disorders in the hip.
      provided access to the deep gluteal region. Sciatic nerve assessment was carried out through the anterolateral and posterolateral portals in the first 20 cases. In some of the earlier cases, the sciatic nerve was freed from impinging structures to restore sciatic nerve mobility; however, if the nerve was tethered proximally or distally, it could not be released. These factors should be considered for further study. Following this observation, a posterolateral auxiliary portal (3 cm posterior and 3 cm superior to the greater trochanter) was used in 15 cases, which allowed for a more thorough inspection of the sciatic nerve to the level of the sciatic notch. In our patients anatomic variations of sciatic nerve entrapment were similar to previously published reports for involvement of the piriformis muscle tendon,
      • Benson E.R.
      • Schutzer S.F.
      Posttraumatic piriformis syndrome: Diagnosis and results of operative treatment.
      • Dezawa A.
      • Kusano S.
      • Miki H.
      Arthroscopic release of the piriformis muscle under local anesthesia for piriformis syndrome.
      • Sayson S.C.
      • Ducey J.P.
      • Maybrey J.B.
      • Wesley R.L.
      • Vermilion D.
      Sciatic entrapment neuropathy associated with an anomalous piriformis muscle.
      atypical fibrous bands,
      • Vandertop W.P.
      • Bosma N.J.
      The piriformis syndrome A case report.
      and hamstring tendons.
      • Puranen J.
      • Orava S.
      The hamstring syndrome A new diagnosis of gluteal sciatic pain.
      Many patients had a thickened greater trochanteric bursa with fibrous scar bands extending to the sciatic nerve. Three of the patients returning after hip arthroscopy had bursal (3) and piriformis (2) injections that did not completely resolve the pain, thus suggesting the pain is not an inflammatory issue but, rather, a structural impingement of the nerve due to the fibrous bands or piriformis tendon. The superior and inferior gluteal nerves, quadratus femoris/gemellus inferior nerve, and obturator internus/gemellus superior nerve may be involved with the scar tissue. The technique of endoscopic decompression of the sciatic nerve requires significant hip arthroscopy experience with familiarity with the arthroscopic anatomy and visualization of the length of the sciatic nerve track so that all impinging structures are thoroughly addressed.
      • Byrd J.W.
      Operative hip arthroscopy.
      Table 5 lists related pearls and pitfalls.
      Table 5Pearls and Pitfalls of Sciatic Nerve Decompression
      Pearls
      • 1
        Perform a standardized physical examination of the hip including the piriformis stretch test, Lasègue test, and Pace test for posterior hip pain
      • 2
        Rule out the lumbar spine and posterior rim impingement through physical examination and additional testing (radiographic, injection tests, EMG NCS, and MR neurography)
      • 3
        Use of the auxiliary posterolateral portal 3 cm lateral to the posterolateral portal and long arthroscopes with an adjustable cannula, as well as a high-definition camera, allows better visualization of the sciatic track
      • 4
        Use dynamic flexion/extension with internal/external rotation to assess sciatic nerve motion
      • 5
        A branch of the inferior gluteal artery should be cauterized before the dissection of the piriformis
      Pitfalls
      • 1
        Check 3-planar osseous anatomy, including femoral and acetabular version, with MRI or computed tomography
      • 2
        Failure to assess for previous intra-abdominal surgery could potentially diminish neural excursion affecting outcome
      • 3
        Inexperience with proximal neural anatomy can negatively affect the outcome
      Abbreviation: NCS, nerve conduction study.
      After endoscopic decompression of the sciatic nerve, functional outcome MHHSs of all cases increased from a mean of 54.4 to 78.0, and postoperative pain was markedly reduced from a mean of 6.9 to 2.4. Only 2 patients required continued narcotic use after surgery, prescribed by an outside physician for pain unrelated to DGS. All patients were able to return to work, and 83% did not have sit pain and were able to sit in a chair for more than 30 minutes. Only 1 patient still had pain at night. The physical examination tests of Lasègue and Pace and the Seated Piriformis Stretch Test were negative in all patients postoperatively. The endoscopic decompression of the sciatic nerve was able to free the nerve from entrapment within the deep gluteal region. However, in some cases the normal glide of the sciatic nerve could not be restored if the nerve was tethered proximal to the sciatic notch principally because of possible scarring proximal to the sciatic notch or diminished femoral version. The Benson outcome rating, a surgical outcomes rating specific to buttock or sciatic pain, was applied to a subset of 23 patients. Of 23 patients, 16 reported good to excellent outcomes per the Benson criteria. The low-improvement group showed lower-activity sports, history of trauma, and radicular complaints with radicular positive tests. Possible negative effects on the outcome occurred from the lack of the auxiliary posterolateral portal, long arthroscopes, and early arthroscopic familiarity of the pathology.
      A thorough history and physical examination with appropriate diagnostic testing are important assessments in the diagnosis of DGS. Our current protocol now includes preoperative bilateral dynamic EMG testing, MRI myelogram of the lumbar spine, a piriformis injection test, and intraoperative nerve monitoring. By eliminating other sources of posterior hip pain, the diagnosis of sciatic nerve entrapment outside of the sciatic notch can be implicated as the etiology. The endoscopic treatment of DGS has been effective in diminishing extra-articular posterior hip pain and return to normal function.

      Limitations

      Experience was a factor in preoperative evaluation and treatment. The physical examination technique improved and the introduction of the auxiliary posterolateral portal and the use of long arthroscopes enhanced the endoscopic visualization along the sciatic nerve. The MHHS is an outcome measure for hip arthroscopy but does not address sciatic nerve complaints. However, the MHHS is the most used measure for reporting clinical results in the United States. The outcomes questionnaire devised by Benson and Schutzer
      • Benson E.R.
      • Schutzer S.F.
      Posttraumatic piriformis syndrome: Diagnosis and results of operative treatment.
      was specific for the symptoms and limitations of the patients in their study. Therefore the validity of these criteria must be determined in other populations. The Benson criteria data were only obtained postoperatively in a subset of patients and are therefore incomplete and not reasonable on which to base outcomes for the entire population. Future protocols should utilize EMG nerve conduction studies, MRI myelogram, and injection tests with operative considerations of long scopes, lengthening canulas, the auxiliary posterolateral portal and intraoperative nerve monitoring. The use of dynamic EMG testing may be useful. Further considerations should analyze the biomechanical effect of increased or decreased femoral version and neck shaft angle related to sciatic nerve kinematics. Inclusion of the Benson criteria along with MHHS will provide a basis for outcome criteria.

      Conclusions

      Endoscopic decompression of the sciatic nerve appears useful in improving function and diminishing hip pain in sciatic nerve entrapment/DGS.

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