DOUBLE COMPRESSION OF THE SCIATIC NERVE IN DEEP GLUTEUS SYNDROME: NERVE RELEASE ASSISTED WITH AUTOLOGOUS PLASMA RICH IN GROWTH FACTORS (PRGF)
Deep gluteal syndrome is an increasingly recognized disease entity, caused by compression of the sciatic or pudendal nerve due to non-discogenic pelvic lesions. It includes the piriformis syndrome, the gemelli-obturator internus syndrome, the ischiofemoral impingement syndrome, and the proximal hamstring syndrome.
Careful history-taking, a physical examination including provocation tests, an electrodiagnostic study, and imaging are necessary for an accurate diagnosis. Ultrasound guided blocks are helpful for diagnoses of sciatic compression.
Open surgical decompression is recommended in patients with persistent or recurrent symptoms after conservative treatment and compression of the sciatic nerve.
We present the cases of a patient with a deep gluteal syndrome with compression of the sciatic nerve at two levels: the problem started with a proximal hamstring syndrome and then developed a piriformis syndrome.
Introduction
In 1999, McCrory and Bell proposed that the term “deep gluteal syndrome” should replace that of the piriformis syndrome. The reason is that posterior hip pain could result from entrapment of the sciatic or other nerves by various structures in this anatomical space. Recently, we can add to the piriformis syndrome, other syndromes that can produce a sciatica-like pain and can be included in the concept of deep gluteal syndrome (DGS): the gemelli-obturator internus syndrome, ischiofemoral impingement syndrome (IFS), and proximal hamstring syndrome (PHS).
Previously, several reviews described the piriformis syndrome as having an estimated prevalence of 5% to 8%. In a recent systematic review including 481 patients with deep gluteal syndrome undergoing surgical treatment, the diagnosis was piriformis syndrome in 124 (26%), sciatic nerve entrapment by non-piriformis muscles in 67 (14%), endometriosis in 27 (6%), and compression by the inferior gluteal vein in eight (2%). Thus, the piriformis syndrome may be much more prevalent than that of other subtypes of the DGS.
The proximal hamstring syndrome mainly develops in patients who undertake competitive sports and has usually been reported in case reports and series. In a retrospective study involving 162 patients, sciatic nerve-related symptoms were noted in 45 patients (28%) with a history of proximal hamstring avulsion. Thus, sciatic nerve entrapment after proximal hamstring injury may be under-recognized.
DGS with compression of the sciatic nerve at two levels are not exceptional, and many times could start with a proximal hamstring syndrome and then developed secondary a piriformis syndrome.
When we treat a piriformis syndrome, there are anatomical variations to think about. A total of 13 anatomical variations in the relationship between the sciatic nerve and piriformis have been described. In 85.2% of individuals, the nerve passes beneath piriformis. Thus, intrinsic pathologies of the piriformis that include an anomalous variation of the relationship between the nerve and piriformis, piriformis hypertrophy, tumours or inflammatory and infectious lesions can affect SN. Sometimes, piriformis syndrome may occur after overuse or repetitive trauma to the gluteal area. In this cases, many patients with post-traumatic entrapment of the sciatic nerve have constricting fibrous or fibrovascular bands from the piriformis over the nerve.
In the other hand, problems in the proximal hamstring insertion, could affect also de SN, because the proximal part of this muscle complex is really close to the sciatic nerve (sciatic nerve lies approximately 1.2 cm lateral to the ischial tuberosity or the outer border of the semi- membranosus tendon). This is the reason why proximal hamstring tendon pathologies can cause irritation or entrapment of the sciatic nerve because of the intimate relationship of the nerve and muscle at the level of the ischial tuberosity. Conditions which predispose to the proximal hamstring syndrome include strains (partial tears), avulsions (complete tears), or hamstring tendinopathy and avulsion fracture or apophysitis of the ischial tuberosity. In some patients with a hamstring injury, tight fibrotic bands compressing the sciatic nerve have been found at surgery.
CLINICAL CASE
A 46-year-old female patient, a regular athlete and trainer, was performing a CrossFit exercise when, following a squat snatch movement, she experienced intense pain in the posterior thigh region. Initially, she rested and took physical measures. After physiotherapy, she was able to train normally, but the pain persisted in the gluteal and posterior regions.
She was diagnosed with piriformis syndrome and received two injections without clinical improvement. Later, she started experiencing numbness in the entire leg while sitting at the office, and even in the car during short trips. She was evaluated by rheumatology, diagnosed with sacroiliitis, and treated with sulfasalazine. The pain did not improve and continued to worsen, even after treatment and multiple injections, impairing her ability to walk and sit properly.
The patient consulted again, reporting increasing difficulty in walking correctly and sitting properly. She presented with paresthesia and significant pain in the gluteal region and posterior thigh of the left leg. The patient stated that she had been unable to sit on the left gluteal region for the past two years, adopting an antalgic position in which she tilts her pelvis and only supports the right side (she cannot place the ischial tuberosity on a flat surface continuously). This was very evident when attempting to sit during the consultation. She also reported pain while walking, especially when starting to walk and placing the heel on the ground. The hip was slightly flexed during the step, and the knee was extended with activation of the hamstrings. The pain was burning and radiated from the gluteal region to the posterior leg.
When observing the patient’s walking posture, an external rotation of the left lower limb was noted. Upon examination, with the patient in supine position, external rotation of the left leg persisted.
The patient had tenderness at the ischial tuberosity and just lateral to it, raising suspicion of a proximal hamstring syndrome. She also reported pain between the ischial tuberosity and femoral head in the piriformis area. Therefore, external rotation of the leg with pain in the deep gluteal area suggested the need to exclude piriformis syndrome.
The scratch test was positive at two levels: one at the lateral region of the ischial tuberosity and the other at the piriformis tendon in the gluteal region. The test was negative after applying ethyl chloride to both areas, confirming the diagnosis suspicion of sciatic nerve compression at both the piriformis tendon and lateral to the ischial tuberosity.
Given the suspected double-level sciatic nerve compression, a local anesthetic suppression test with lidocaine was performed. After identifying the sciatic nerve just lateral to the ischial tuberosity under ultrasound guidance, 2 cc of anesthetic were injected in this location. After 10 minutes and re-evaluating the patient, the pain in this region disappeared, allowing the patient to sit properly, something she had been unable to do for over two years. However, pain persisted proximally at the piriformis tendon, with continued sciatic nerve irritation and pain when flexing the hip to 90° and performing internal rotation. Another 2 cc of lidocaine were injected in this region under ultrasound guidance, leading to complete resolution of the pain.
Radiological studies of the pelvis and lumbar spine were normal. The lumbar spine MRI did not show any discopathy or herniated discs. The pelvic MRI revealed a chronic lesion at the semimembranosus tendon near its insertion site.
With the diagnosis of deep gluteal syndrome with double sciatic nerve compression, one at the piriformis tendon and another lateral to the ischial tuberosity secondary to a chronic proximal hamstring injury, and given the lack of response to conservative treatments (oral analgesics, physiotherapy, injections, and percutaneous electrolysis at the piriformis tendon), surgical treatment was decided.
After general anesthesia, the patient was positioned prone. The distal gluteal fold and ischial tuberosity were palpated. A 6 cm longitudinal incision was made immediately lateral to the ischial tuberosity, starting from the gluteal fold and extending distally.
The first step was to identify the sciatic nerve, using the ischial tuberosity as a reference and locating the nerve just lateral to it. An exoneurolysis of the sciatic nerve was performed, as the nerve was adherent and encased by fibrosis. A partial lesion of the semimembranosus tendon was identified but had healed without discontinuity at its insertion point at the ischial tuberosity. A small fibrotic band lateral to the ischial tuberosity was found to be compressing the sciatic nerve in this area, without evident ischiofemoral involvement.
PRGF (Platelet-Rich Growth Factor) was introduced at the tendon insertion area at the ischial tuberosity and at the epineural region of the sciatic nerve. The incision was closed in layers.
The patient was then repositioned in the lateral decubitus position, on her right side. A posterior-lateral hip approach was made with a mini-incision. After separating the gluteus medius muscle, the piriformis tendon was identified, showing significant tension and causing compression of the sciatic nerve beneath it. Internal rotation of the left hip was notably difficult. A tenotomy of the piriformis tendon was performed, and upon sectioning, the tendon quickly retracted medially, indicating it was very tense and shortened. Other areas of sciatic nerve compression distal to this region were ruled out.
The patient was kept in the hospital for 24 hours, with no complications during the postoperative period.
After 48 hours, the patient began walking without pain and without the need for walking aids. Pain with sitting and walking disappeared immediately.
After 9 months, following a period of physiotherapy and muscle strengthening, the patient was pain-free and able to resume high-level physical activity. She returned to her work as a personal trainer, teaching at least four classes daily in addition to individual training sessions. She was fully satisfied and asymptomatic.
DISCUSION
The anatomic and biomechanical relationship of the Sciatic nerve (SN) to the proximal hamstrings insertion in the deep gluteal space is critical to diagnosis the causes of DGS. After exiting the pelvis anterior to the piriformis muscle, the SN runs posteriorly to the obturator/gemelli and quadratus femoris muscle, located at the most lateral aspect of the ischial tuberosity. The SN also maintains an intimate relationship with the hamstrings origin. Within the ischiofemoral space, the SN shares the same spatial location with the lesser trochanter, which is separated from the SN by the quadratus femoris muscle. The proximal insertion of the semimembranosus muscle at the lateral aspect of the ischium is another structure that shares the same anatomic spatial location within the ischiofemoral space. Distal to the ischium (7 cm from the ischial tuberosity), the first branch of the SN emerges adjacent to the long head of the biceps femoris, which can also contribute to SN entrapment as it courses to the lower extremity.
Isolated lesions in the proximal insertion of the hamstrings tendons can reproduce symptoms associated with DGS. Chronic and repetitive tears or a single acute lesion as in the case of our patient can contribute to the development of hamstrings syndrome and SN compression.
Subjects with proximal hamstrings injuries may experience functional incapacity and pain at the ischium or lateral to the ischium with sitting, stretching, and during exercises. This pain is caused by SN traction, compression, or irritation. If the patient is driving with the hip in 30º flexion, the hamstrings (semimembranosus) show a different force vector angle in comparison when there is 90º activation of the hamstrings. Therefore, when patients practice activities holding the hip in 30º hip flexion and they activate the hamstrings, they reproduce SN Complain as in the case of the patient described above. Our patient has also impossibility to walk properly and climb stairs.
Patients with SN entrapment, develop symptoms of sit pain (inability to sit for >30 minutes), radicular pain and paresthesias of the affected leg appears. This was the clinic, that the patient of our case developed. Always we have to do a proper exploration of the hip and the spine.
It is important to think about compression syndromes at the ischiofemoral space, in cases of chronic hamstrings tears. In a study performed by Gómez-Hoyos, lesser trochanteric version alone does not influence the ischiofemoral space (IFS), but the lesser trochanteric version may have an influence in subjects with chronic hamstrings tears. Further studies need to confirm these anatomic variations. In our case, the patient didn´t have an ischiofemoral syndrome.
The differential diagnosis of posterior hip pain can be localized to proximal or distal regions, and clinic is important for diagnoses.
After proximal chronic hamstrings tears with SN compression, during the initial heel strike, the hamstrings muscles act eccentrically, decelerating the leg during heel strike. Subjects referring pain lateral to the ischium during this specific motion may present a positive sign.
Conversely, patients with IFI are more comfortable sitting, but the pain is bigger when they are walking during terminal hip extension (the space between ischium and the lesser trochanter is diminished). Long stride–walking test is 1 of 2 tests used to diagnose IFI and it is a critical diagnosis tool. The long stride–walking test is positive when the patient refers pain lateral to the ischium during terminal extension that is relieved with short steps. Our patient didn’t have a IFI syndrome.
Also, palpation of the gluteal structures in the seated position using the ischial tuberosity as a reference point, can also guide and distinguish sources of posterior hip pain.
Exploration tests are important for the diagnosis of SN compressions:
- Active hamstring test: This test is useful in patients with a Hamstring syndrome and SN compression. With the patient in sitting position, the patient is asked to actively flex the knee (positioned at 30º and 90º of flexion against resistance). Pain and paresthesia are typical in this syndrome.
- The piriformis stretch test (sensitivity 0.52, specificity 0.90). The test is performed with a flexion, adduction with internal rotation of the hip. The examiner extends the knee (engaging the SN) and passively moves the flexed hip into adduction with internal rotation while palpating the piriformis muscle lateral to the ischium or proximally at the sciatic notch. A positive test is the recreation of the posterior pain at the level of the piriformis muscle lateral to the ischium or external rotators.
- The active piriformis test: moving the patient to lateral decubitus, the patient is instructed to drive the heel into the examination table, initiating active hip abduction and external rotation against resistance from the examiner. A positive test is the presence of pain at the level of the piriformis or external rotators.
The standard imaging studies include the standing anterior-posterior pelvis, false profile, and lateral images. No alterations were found in our case.
The assessment of the semimembranosus and its orientation to the lateral ischium is best visualized on T2 axial or T2 coronal imaging. This view allows for the detection of a partial tear or undersurface tears of the semimembranosus. Scarring in this region can be assessed by T1 and T2 MRI in the axial and coronal planes.
EMG has not been found to be useful (in our case was normal). If EMG is used, the testing should be performed in a dynamic modality with the knee in extension and the hip in flexion and abduction and the symptomatic side is compared with the non-symptomatic side looking at neural latency.
Injection tests have been advocated for supporting the diagnosis of posterior extra-articular and intra-articular hip disorders. Anesthetic injection to the piriformis muscle can provide relief and an injection just lateral to ischiatic tuberosity. Relief of pain after this blocked test, help us for the diagnosis and for the prognosis of treatment.
In these cases, we always start with conservative treatment: physical therapy treatment for individuals with hamstrings syndrome and piriform syndrome (rebalance the muscle articular functioning of the hip/pelvis and spine through soft tissue mobilization, stretching and strengthening exercises).
Also, posterior hip pain can affect quality of life and mental health and a neuropsychiatric evaluation many times is required.
When conservative treatment fails, surgical treatment is required. Open and endoscopic approaches can be used for Chronic hamstring avulsions. Recently, full endoscopic approaches to hamstring repair have increased in popularity due to complications associated with open techniques, including extensive tissue exposure, and proximity of incision to perianal zone; however, the procedure becomes very difficult with retractions greater than 5 cm.
In this case we performed an open approach for SN release close to ischiatic tuberosity and hamstring tendons and a posterolateral approach for the piriformis release. First, the patient is placed in the prone position with the knees in a flexed position. An incision may be either longitudinal or transverse to the gluteal fold.
We preferred a longitudinal incision for an easier access for the sciatic nerve. Fascia overlaying the hamstring compartment is exposed through blunt dissection of the subcutaneous tissue, and retraction of the gluteus maximus is performed. After, an exoneurolisis of SN is done. Sometimes after an injured hamstring tendon, we can find a fibrotic band just lateral to ischiatic tuberosity that can contribute to SN compression like in the case described above.
Finally, we infiltrated growth factors into the semimembranosus tendon, as well as its insertional area at the ischial tuberosity. Additionally, to reduce postoperative pain caused by manipulation of the sciatic nerve, we introduced intraneural PRGF (Plasma Rich in Growth Factors) at the epineural level and prepared a PRGF membrane to reduce adhesions around the sciatic nerve.
Following distal compression, it is common for proximal compression to occur due to secondary edema in the nerve. For this reason, it is important to explore potential proximal or distal compression zones to ensure optimal treatment. In this case, based on clinical presentation, the scratch test, and the suppression test, the patient had proximal compression at the level of the piriformis tendon. Releasing the piriformis tendon in such cases is a simple and effective treatment for sciatic nerve decompression. In this case, unlike other cases, we did not find any compressive band associated with a hypertonic piriformis tendon at this level.
Conclusions
Double-level compressions in the context of deep gluteal syndrome are not uncommon. Medical history, the mechanism of injury, physical examination, and suppression tests are crucial for diagnosis. It is important to rule out secondary compression zones that could obscure the outcome. Sciatic nerve external neurolysis surgery yields good results. The use of PRGF improves postoperative pain and reduces potential adhesions secondary to surgical intervention.
