Top 10 Technical Tips and Tricks for Safe Sciatic Nerve Management During Posterior Hip Endoscopy

Abstract

Background:

A thorough understanding of posterior hip anatomy is essential for safe and effective posterior hip endoscopy. The sciatic nerve runs laterally to the ischium and hamstring origin. While sciatic nerve injury during proximal hamstring repair is uncommon, the increasing use of endoscopic techniques has led to a rise in iatrogenic injuries. This highlights the need for a structured approach to identifying and protecting the sciatic nerve.

Indications:

Surgical intervention is indicated for complete proximal avulsions involving all 3 hamstring tendons, partial avulsions involving ≥2 tendons and >2 cm of retraction, and partial avulsions that fail to improve after 6 months of conservative management.

Technique Description:

There are various safeguards to safely manage the sciatic nerve during posterior hip endoscopy. Proper patient positioning and portal creation are essential steps to minimize sciatic nerve risk. Utilization of prone positioning with strategic padding allows slight hip extension, knee flexion, and hip abduction. In turn, this will relax the nerve and increase the ischiofemoral space. Creation of the subgluteal space is critical, with meticulous resection of the subgluteal bursa to expose the proximal hamstring tendon and surrounding anatomy. A fascial veil consistently separates the tendon from the sciatic nerve and can be partially resected for nerve visualization. Tear exposure is achieved through a longitudinal split between the semimembranosus and conjoint tendon, which also serves as access for ischioplasty. The remaining tendon provides natural protection, while fluoroscopy guides safe bony resection and helps assess ischial width.

Results:

Endoscopic proximal hamstring repair is an effective approach leading to significant improvement in pain and function. Among endoscopic hamstring repairs, complications—such as persistent peri-incisional numbness and postoperative neuropathy—have each been reported in approximately 8% of cases. This highlights the importance of proper sciatic protection.

Discussion/Conclusion:

Endoscopic proximal hamstring repair and ischioplasty serve as effective, minimally invasive options for proximal hamstring pathology with careful attention to sciatic nerve safety. A thorough understanding of posterior hip anatomy, strategic patient positioning, precise portal placement, and deliberate dissection techniques is critical for minimizing iatrogenic nerve injury.

Patient Consent Disclosure Statement:

The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

In this video, we will review the top 10 technical tips and tricks for safe sciatic nerve management during posterior hip endoscopy—including proximal hamstring repairs and ischioplasty.

Background

The first component is understanding the posterior hip anatomy. The proximal hamstring originates from the lateral ischium, with the semimembranosus being the most lateral, and the biceps femoris and semitendinosus forming the conjoint tendon medially. Hamstring tears are a common cause of injury in athletes and can range from tendinopathy to complete rupture. Here, we highlight the indications for proximal hamstring repair—including 3 tendon tears, partial avulsions of ≥2 tendons with ≥2 cm of retraction, and partial avulsions recalcitrant to 6 months of conservative measures.^1-3

Ischioplasty is considered in cases with ischiofemoral space narrowing, which has ranged between a threshold of 15 to 22 mm in the literature, and failure of conservative measures.^8-10 Ischioplasty is particularly considered in cases where ischiofemoral narrowing is observed alongside a concomitant proximal hamstring tear. This would be favored over lesser trochanter osteoplasty.

The sciatic nerve exits the greater sciatic notch, coursing deep to the piriformis and superficial to the remaining short external rotators, running lateral to the ischium and proximal hamstring tendons.^1-3,6 Sciatic nerve injury during proximal hamstring repair is rare, reported between 1% to 2%. However, anecdotally, with the rise in endoscopic proximal hamstring repairs, we have seen an increase in resultant iatrogenic sciatic nerve injuries.^1-3,6 Causes of iatrogenic nerve injury are variable, and may include inappropriate portal placement, overaggressive blunt handling of the nerve, poor visualization leading to injuries during bursectomy, suture passage or knot tying, or inadvertent local anesthetic infiltration. Thus, we would like to propose a framework for nerve identification and protection.

Indications

A quick illustrative case involves a 50-year-old female with 10 years of right buttock pain that has failed conservative management. On radiographs, the preserved joint space is seen with a decreased ischiofemoral space, and magnetic resonance imaging (MRI) demonstrates a partial proximal hamstring tear, which is our indication for endoscopic proximal hamstring repairs and ischioplasty over open procedures. Axial T1 MRI sequences with the leg in neutral rotation are used to confirm narrowing of the ischiofemoral space, with cutoffs in the literature ranging from 15 to 22 mm.^8-10 Intraoperatively, although imperfect, we use an anteroposterior fluoroscopy view, with the leg in neutral rotation, to estimate the ischiofemoral space, which was found to be 17 mm in this case. Arthroscopic instruments, such as the 5 mm bur, can be used to quickly estimate the resection level arthroscopically as well.

Technique Description

Patient positioning is the second critical step for protecting the sciatic nerve. In prone positioning, well-padded bumps under the patient's chest, iliac crest, knee, and ankle allow for slight hip extension and knee flexion to relax the sciatic nerve. Slight hip abduction on a padded Mayo is preferred to increase the ischiofemoral space.

With portal placement, the initial medial portal creation can be performed with or without fluoroscopy. A blunt trochar is used to palpate the medial ischial tuberosity and insert the arthroscope, and the lateral portal is created under direct visualization with a spinal needle. As long as the lateral portal is created in line with the lateral border of the ischium or medial to that, and only the skin is incised, and the portal is created with blunt instruments, the sciatic nerve is protected. When creating the lateral portal, attention must be paid to a horizontal trajectory to the ischium to prevent injury to the sciatic nerve and the posterior femoral cutaneous nerve (PFCN). In addition, the lateral portal should be made in the gluteal crease in line with the medial portal, so that if conversion to an open procedure is necessary, the incisions can be connected in the transverse gluteal crease.

Perhaps the most critical step is adequate subgluteal space creation. Analogous to the subacromial space, the subgluteal bursa must be resected to expose anatomic landmarks. A shaver (CrossBlade Smooth Bite, 3.5 mm; Stryker Corp) without teeth should be used during this step. The first landmark is the white tissue of the proximal hamstring tendon, which in partial tears should be confluent proximally with the ischium, which can be palpated with the instrument. Distally, the myotendinous junction should be exposed for later suture passage, and when working laterally, the instrument should always be facing medial, with an increase in blunt dissection techniques.

Following exposure of the proximal hamstring tendon, a raphe lateral to the entire tendon can be found. This should be bluntly developed until a constant fascial band, separating the proximal hamstring and sciatic nerve, can be identified. Viewing posteriorly, the sciatic nerve is always behind this fascial veil, and a portion of this fascia can be resected for added visualization of the sciatic nerve. Palpation with the blunt instrument should be performed to confirm the mobility and “looseness” of the sciatic nerve in contrast to the taut feel of the hamstring tendons.

The sciatic nerve can then be traced proximally to identify the branching PFCN. The PFCN will be accompanied by fat and venae concomitates, and blunt neurolysis of both the sciatic nerve and PFCN can be performed at this stage with a switching stick or backside of the shaver or RF (radiofrequency) device (SERFAS 90-S 4.0mm; Stryker Corp), with care taken not to traumatically rupture the vessels that may lead to bleeding and poor visualization.

Results

Next, proximal hamstring tear identification and exposure for a safe working interval should be performed. A raphe between the lateral semimembranosus and medial conjoint tendon can often be palpated, and a longitudinal split through this should be performed in cases of partial, ischial-sided tears. This also acts as the exposure to the ischium for the later ischioplasty.

For safe ischioplasty completion, resection should be completed through the longitudinal split of the proximal hamstring. The intact proximal hamstring tendon remaining laterally acts as a natural retractor against iatrogenic sciatic nerve injury. Fluoroscopy can be utilized at this stage to (1) measure the preoperative ischial tuberosity width, and (2) to identify a safe location of the bur (CrossBlade XL Diamond Bur 5.5 mm; Stryker Corp). Frequent visualizations of the sciatic nerve and PFCN should take place during the ischioplasty, and fluoroscopy can again be used to measure the resection amount. Of note, the width of the ischium is a more reliable marker of ischioplasty as the ischiofemoral distance is affected by leg position.

The amount of ischial resection is typically dependent on the degree of ischiofemoral narrowing and is patient specific. Keeping the ischial width in mind, the amount of ischial resection should aim to result in an ischiofemoral space greater than the threshold range of 15 to 22 mm. In this case, the ischiofemoral space was measured to be 17 mm on MRI, and 5 mm was ultimately resected using fluoroscopy to confirm the distance from the leg in neutral rotation.

Several technical pearls can avoid iatrogenic sciatic nerve injury during proximal hamstring repair, even utilizing an arthroscopic whipstitch technique. An accessory portal is helpful for improved trajectory to the ischium for suture anchor placement, as well as suture management. Two triple-loaded polyether ether ketone (PEEK) anchors (Stryker Alphavent 4.75 mm; Stryker) are utilized with suture rather than tapes to allow for ease of suture passage during whipstitching.

Suture passage through the proximal hamstring tendon can be performed in a variety of methods. A self-penetrating, self-retrieving instrument (Arthrex Penetrator Suture Retriever; Arthrex Inc), either reusable or disposable, can be used to pierce the tendon and retrieve sutures. This is perhaps safer on the lateral edge near the nerve, especially for the first pass. An antegrade self-retrieving suture passer (Arthrex FastPass Scorpion SL Suture Passer; Arthrex Inc) can also be used, as long as visualization of the nerve is adequate, and there is ample room for the lower jaw of the instrument to pass under the tendon.

A penetrating suture retriever can be used laterally near the nerve to directly visualize suture passage and ensure no entrapment of the sciatic nerve. A self-retrieving suture passing device can be used medially to run the other limbs of the suture in a nonlocking fashion proximally and distally along the proximal hamstring tendon. The same device can even be used laterally, without fear of the needle passage injuring the sciatic nerve, as long as adequate dissection and visualization of the sciatic nerve have occurred, and each passage of suture should be directly visualized. Knot tying should always be preceded by grabbing both limbs of the suture with a loop grasper to ensure no soft-tissue bridge—including neurovascular structures—and tying can occur within the cannula to act as soft tissue protectors. Final visualization of the entire sciatic nerve and PFCN should be performed to ensure no iatrogenic injury or incarceration with suture. Another technique utilized involves the same accessory portal for suture anchor placement. Following that, a switching stick is placed in this accessory portal and is held by an assistant as a blunt sciatic nerve retractor. It can be parked along the lateral border of the ischium, providing excellent protection for the sciatic nerve. The switching stick and sciatic nerve can be kept in the background of the visual field during all resultant steps of the proximal hamstring repair—including suture anchor placement, suture passage, and knot tying.

The final step of sciatic nerve protection involves perioperative and postoperative care. No local anesthetic is used at the conclusion of the case; a hinged knee brace locked in flexion is used to both prevent stress on the hamstring repair and also reduce stretch on the sciatic nerve, and a mandatory neurovascular check is performed in the post-anesthesia care unit immediately upon waking from anesthesia in case a prompt return to the operating room is required.

Discussion/Conclusion

To review, these are our top 10 technical pearls to avoid iatrogenic sciatic nerve injury during posterior hip endoscopy—including proximal hamstring repairs and ischioplasty.

A standard postoperative protocol is employed, similar to that used in open proximal hamstring repairs. During phase 1, patients use crutches to remain toe-touch weightbearing and begin physical therapy at 4 weeks postoperatively. During phase 2, concentric strengthening with progression to eccentric strengthening is emphasized, and patients gradually progress off crutches. During phase 3, patients return to light jogging, closed-chain plyometric exercises, and sport-specific movements, if applicable. At 6 months, patients are cleared to gradually return to sports.

Both short- and mid-term outcome studies have demonstrated significant improvements in patient-reported outcomes and return to sports in endoscopic proximal hamstring repairs, with overall low incidences of significant neurologic complications.^2,5

By initiating the endoscopy with a medial portal, the risk for sciatic nerve or PFCN injury is essentially zero. A cadaveric study performed by Su et al, ⁷ including the senior author (S.J.N.), demonstrated that the medial portal had a mean distance of 6.7 cm from the sciatic nerve and 5.9 cm from the PFCN, with the shortest range >4 cm. Clinically, the senior author performs all posterior hip endoscopy with a blind medial portal, palpating the ischium with a blunt trochar following incision through skin only with an 11 blade, and has never had an iatrogenic injury from the medial portal.

Endoscopic lesser trochanter osteoplasty is another surgical intervention to address recalcitrant ischiofemoral impingement syndrome ⁴ . Partial resection is emphasized to prevent weakening of hip flexion due to complete iliopsoas tendon release. ⁴ However, in cases with concomitant proximal hamstring tears, ischioplasty is preferred given the exposure provided during the proximal hamstring repair itself and the ability to address both pathologies in 1 surgical area.