Background/Purpose: Piriformis Muscle Syndrome (PMS) is caused by sciatic nerve compression in the infrapiriformis canal. However, its pathophysiology is poorly understood and this syndrome is difficult to diagnose.  This study aimed to propose a clinical assessment score for facilitating PMS diagnosis and to develop a treatment strategy.

Methods: 250 patients versus 30 control patients with disco-radicular conflict, plus 30 healthy control subjects were enrolled in this study.  A range of tests (Freiberg, FAIR [Flexion-Adduction-Internal Rotation], heel-contralateral knee manoeuvre and Beatty test)   were used to produce a diagnostic score for PMS and an optimum treatment strategy was proposed (muscle relaxant medication, intense self-rehabilitation program, Onabotulinumtoxin A injection in the cases of non-response to rehabilitation and then surgery for the refractory cases).

Results: A 12-point clinical scoring system (Table) was devised and a diagnosis of PMS was considered ‘probable’ when it was ≥ 8.  Sensitivity and specificity of the score were 96.4% and 100%, respectively, while the positive predictive value was 100% and negative predictive value was 86.9%.  Combined medication and rehabilitation treatments had a cure rate of 51.2%. 122 patients (48.8%) were unresponsive to treatment and received Onabotulinumtoxin A. Visual Analogue Scale results were ‘Very good/Good’ in 77%, ‘Average’ in 7.4% and ‘Poor’ in 15.6%.  15 of 19 patients unresponsive to treatment underwent surgery with ‘Very good/Good’ results in 12 cases

Conclusion: the proposed evaluation score may facilitate PMS diagnosis and treatment standardisation. Rehabilitation has a major role associated in half of the cases with botulinum toxin injections.

Table: Proposal for a clinical scoring system for the diagnosis of Piriformis Muscle Syndrome. FAIR: Flexion-Adduction-Internal Rotation; HCLK: heel contralateral knee. Piriformis muscle syndrome: Probable if score greater than or equal to 8; Unlikely if score less than 8 and greater or equal to 6; Not considered if score less than 6.

criteria	point
Unilateral or bilateral buttock pain with fluctuating periods without pain throughout the course of the day	1
No lower back pain	1
Axial spinal palpation painless (L2 to S1)	1
Negative Lasegue’s manoeuvre	1
Seated position (often for a prolonged period) triggering buttock pain and/or sciatic pain	1
Sciatic pain with fluctuating periods without pain throughout the course of the day	1
Buttock pain next to the projection of the piriformis muscle reproduced by Stretching manoeuvres (FAIR, Freiberg, HCLK) Contraction resisted manoeuvres (Beatty) Palpation	1 1 1
Sciatic pain (L5, S1 or truncal sciatic area) reproduced by the extension of clinical manoeuvres (several tens of seconds) Stretching Resisted contraction	1 1
Absence of perineal irradiation	1
Total	12

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/piriformis-muscle-syndrome-diagnostic-criteria-and-treatment-of-a-monocentric-series-of-250-cases/