Research Review By Dr. Joshua Plener©


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Date Posted:

January 2021

Study Title:

Deep gluteal syndrome is defined as a non-discogenic sciatic nerve disorder with entrapment in the deep gluteal space: a systematic review


Kizaki K, Uchida S, Shanmugaraj A et al.

Author's Affiliations:

Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, Ontario, Canada; Department of Orthopaedic Surgery, Wakamatsu Hospital, Japan; Division of Orthopaedic Surgery, Department of Survey, McMaster University Medical Centre

Publication Information:

Knee Surgery, Sports Traumatology, Arthroscopy 2020; 28: 3354-64.

Background Information:

A number of disorders, such as sciatic nerve entrapment, can result in the common patient presentation of buttock and posterior hip pain (1). The term ‘piriformis syndrome’ has commonly been used by clinicians to diagnostically describe sciatic nerve entrapment by the piriformis muscle (2). Current evidence has demonstrated that other muscles such as obturator internus, levator ani, gemelli muscle, and coccygeus muscle can also result in sciatic nerve entrapment and its resultant symptomatology (3, 4). Therefore, the more general and appropriate term of ‘deep gluteal syndrome’ has been introduced as early as two decades ago (5) and now adopted by many.

Unfortunately, there is ambiguity surrounding deep gluteal syndrome, resulting in clinicians not feeling confident with diagnosing this condition. The purpose of this systematic review was to identify the definition for deep gluteal syndrome and deep gluteal space, as well as propose a general diagnostic pathway for deep gluteal syndrome. This will hopefully allow clinicians to confidently add this condition to their list of possible differential diagnoses in this area, while updating the oft-overused diagnosis of ‘piriformis syndrome’.

Pertinent Results:

The initial search found 359 articles, with 14 studies meeting eligibility criteria, consisting of 853 total patients. In the last 5 years, more than half the papers on deep gluteal syndrome have been published.

The included studies had a consensus average score of 10.7 (+ or – 1.5) on the MINORS scale, indicating fair methodological quality.

Definition of Deep Gluteal Syndrome Disease and Deep Gluteal Space
11 studies explicitly described the definition of deep gluteal syndrome which was comprised of three characteristics:
  1. Non-discogenic
  2. Sciatic nerve pain
  3. Entrapment in the deep gluteal space
The deep gluteal space was defined in seven studies and consisted of:
  • Anterior border: posterior acetabular column
  • Posterior border: gluteus maximums muscle
  • Medial border: sacrotuberous ligament
  • Lateral border: gluteal tuberosity
  • Superior border: sciatic notch
  • Inferior border: ischial tuberosity
The deep gluteal syndrome diagnostic pathway was characterized into five domains:
  1. History taking:
    • The most common symptoms reported are posterior hip pain, radicular pain and worsening symptoms when sitting for more than 20-30 minutes.
  2. Physical examination:
    • Tenderness in the deep gluteal space
    • Positive results with the seated piriformis test, which consists of the examiner extending the seated patient’s knee and passively moving the flexed hip into adduction with internal rotation, recreating posterior hip pain at the level of the piriformis or other external rotators (6). The diagnostic accuracy of seated piriformis test reveals a sensitivity of 0.52 and specificity of 0.90 (7).
    • Positive Pace sign which is a recreation of posterior hip pain with active or resisted abduction and external rotation of the hip (6). The Pace sign has a sensitivity of 0.78 and specificity of 0.80 (7).
  3. Imaging tests:
    • Pelvic radiographs and pelvic MRI were commonly used to find abnormalities in the deep gluteal space such as sciatic nerve entrapment by the piriformis muscle or obturator internus muscle.
    • Spinal MRI was used to rule out discogenic sciatic nerve entrapment.
  4. Response-to-injection:
    • Studies used ultrasound-guided injection with the most common medications including local anesthetic combined with corticosteroids.
  5. Nerve specific tests including electromyography can also be conducted.
In most studies, history taking, physical examination and imaging tests were performed. In eight studies, response-to-injection was performed and in five studies nerve-specific tests were performed.

Clinical Application & Conclusions:

This study defined and outlined the definition of deep gluteal syndrome and the deep gluteal space. The authors also proposed a diagnostic pathway for this condition – summarized below:
Deep gluteal syndrome

Previous reviews demonstrated the most common cause of deep gluteal syndrome was iatrogenic, specifically via previous injection or debris from arthroplasty prosthesis, followed by piriformis syndrome and trauma (8).

Past research has demonstrated that the term deep gluteal syndrome may be broadened from the typical condition of sciatic nerve entrapment. This could include other conditions such as bursitis in the deep gluteal space, proximal hamstring tendinopathy, piriformis muscle pyomyositis, posterior femoral cutaneous nerve entrapment, inferior gluteal nerve entrapment, and superior gluteal nerve entrapment within the deep gluteal space (9-13). However, the current evidence covered in this systematic review only describes deep gluteal syndrome cases resulting from sciatic nerve entrapment. A future framework is required to determine if this syndrome is only specific to sciatic nerve pathologies or could encompass other pathological conditions.

Study Methods:

A literature search with the key term deep gluteal syndrome was performed in four electronic databases: MEDLINE, EMBASE, Google Scholar, and Pubmed.

A 3-step screening process was carried out which included title screening, abstract screening, and full-text screening to determine eligible studies. Two reviewers independently screened the articles and if discrepancies arose during the full-text screening, discussion and consensus occurred with the senior authors.

Eligible studies had to have cases diagnosed with deep gluteal syndrome. If the diagnostic pathway was not explicitly shown in the study, it was excluded. In addition, review articles and commentary papers were excluded.

Data was independently extracted by two authors, consisting of demographics, deep gluteal syndrome disease definition, deep gluteal space definition, and deep gluteal syndrome diagnostic pathway. The extracted data was qualitatively synthesized.

The methodological index for non-randomized studies (MINORS) appraisal tool was used to assess the study quality (14). A score of 0-2 was provided to each of the eight items on the checklist for a maximum score of 16 for non-comparative studies. The quality was categorized a priori as 0-8 for poor quality, 9-12 for fair quality, and 13-16 for excellent quality.

Study Strengths / Weaknesses:

  • Identifying a potential deep gluteal syndrome diagnostic pathway that clinicians can utilize should be helpful.
  • There is a risk of publication bias, as cases clearly diagnosed with deep gluteal syndrome were included in this systematic review, but less clear cases were likely not included due to not being diagnosed in the medical literature. This can result in a potential oversimplification of the disease definition and diagnostic pathway (15).
  • The diagnostic pathway proposed is not validated and further research needs to occur to confirm the accuracy of the three components of the pathway (16).

Additional References:

  1. Frank RM, Slabaugh MA, Grumet RC, et al. Posterior hip pain in an athletic population: differential diagnosis and treatment options. Sports Health 2010; 2(3): 237–246.
  2. Cass SP. Piriformis syndrome: a cause of nondiscogenic sciatica. Curr Sports Med Rep 2015; 14(1): 41–44.
  3. Diop M, Parratte B, Tatu L, et al. Anatomical bases of superior gluteal nerve entrapment syndrome in the suprapiriformis foramen. Surg Radiol Anat 2002; 24(3–4): 155–159.
  4. Meknas K, Christensen A, Johansen O. The internal obturator muscle may cause sciatic pain. Pain 2003; 104(1–2): 375–380.
  5. McCrory P, Bell S. Nerve entrapment syndromes as a cause of pain in the hip, groin and buttock. Sports Med 1999; 27(4): 261–274.
  6. Vassalou EE, Katonis P, Karantanas AH. Piriformis muscle syndrome: a cross-sectional imaging study in 116 patients and evaluation of therapeutic outcome. Eur Radiol 2018; 28(2): 447–458.
  7. Martin HD, Kivlan BR, Palmer IJ, et al. Diagnostic accuracy of clinical tests for sciatic nerve entrapment in the gluteal region. Knee Surg Sports Traumatol Arthrosc 2014; 22(4): 882–888.
  8. Kay J, Morrison L, Fejtek E, et al. Surgical management of deep gluteal syndrome causing sciatic nerve entrapment: a systematic review. Arthroscopy 2017; 33(12): 2263–2278.
  9. Lempainen L, Sarimo J, Mattila K, et al. Proximal hamstring tendinopathy: results of surgical management and histopathologic findings. Am J Sports Med 2009; 37(4): 727–734.
  10. Toda T, Koda M, Rokkaku T, et al. Sciatica caused by pyomyositis of the piriformis muscle in a pediatric patient. Orthopedics 2013; 36(2): e257–e259.
  11. Murinova N, Krashin D, Trescot AM. Posterior femoral cutaneous nerve entrapment: pelvic. Peripheral nerve entrapments. Springer, 2016, Cham, pp 683–690.
  12. Trescot AM. Inferior gluteal nerve entrapment. Peripheral nerve entrapments. Springer, 2016, Berlin, pp 581–587
  13. Trescot AM. Superior gluteal nerve entrapment. Peripheral nerve entrapments. Springer, 2016, Berlin, pp 571–579.
  14. Slim K, Nini E, Forestier D, et al. Methodological index for non-randomized studies (MINORS): development and validation of a new instrument. ANZ J Surg 2003; 73(9): 712–716.
  15. Andrews NA, Latrémolière A, Basbaum et al. Ensuring transparency and minimization of methodologic bias in preclinical pain research: PPRECISE considerations. Pain 2016; 157(4): 901.
  16. Bolarinwa OA. Principles and methods of validity and reliability testing of questionnaires used in social and health science research. Niger Postgrad Med J 2015; 22(4): 195