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Piriformis Release Surgery: Beware!
Abstract & Commentary
By Michael Rubin, MD, Professor of Clinical Neurology, Weill Cornell Medical College. Dr. Rubin reports no financial relationships relevant to this field of study.
Synopsis: Piriformis syndrome remains an elusive diagnosis and neurologists should avoid recommendations for surgery interventions.
Source: Justice PE, et al. Piriformis syndrome surgery causing severe sciatic nerve injury. J Clin Neuromuscul Dis 2012;14:45-47.
Most descriptions of Pirformis Syndome, a controversial entity whereby the piriformis muscle or tendon is hypothesized to compress the sciatic nerve resulting in symptoms that mimic L5 or S1 nerve root compression, antedate modern diagnostic techniques and may actually have represented cases of radiculopathy, plexopathy, or proximal sciatic neuropathy from other causes. In the modern imaging area, when other entities are excluded in patients with otherwise typical sciatica, piriformis syndrome rears its provocative head and when conservative efforts, including injection of the piriformis with anesthetic, corticosteroid, or botulinum toxin, are unsuccessful, transection or release of the piriformis muscle or tendon has been advocated as a relatively safe intervention. This appears to no longer be the case.
Two patients, a 37-year-old man and a 71-year-old woman, underwent piriformis release surgery and, within hours postoperatively, developed severe sciatic neuropathy affecting the peroneal more than tibial innervated muscles in the former, and both branches equally in the latter, with profound weakness and foot numbness which, over several months to a year, demonstrated electrical improvement in the form of reinnervation potentials on needle electromyography, without significant clinical improvement in strength. Intraoperative transection of the nerve was excluded by the presence of the reinnervation potentials, and stretch injury to the sciatic nerve due to blade retraction was suspected. Similar adverse outcomes previously have been reported following surgical intervention for other controversial entrapment neuropathies, including radial tunnel release for radial tunnel syndrome and brachial plexopathy following thoracic outlet surgery, but never following piriformis surgery. Surgeons be forewarned!
As initially described, one of the cardinal features of piriformis syndrome that is felt to be almost pathognomonic is the presence of a palpable, sausage-shaped mass over the piriformis during an acute exacerbation of pain, which is markedly tender to pressure. One wonders if it is at all possible to palpate a spindle-shaped or sausage-shaped mass in the piriformis, lying as it does beneath the gluteus maximus, gluteus medius, subcutaneous tissue, and skin? Textbooks describe trigger points, particularly in the lateral third of the muscle near its insertion. Yet, with the tendon having an average diameter of 6.3 mm at the level of the musculotendinous junction, it stretches the imagination to accept that such as small tendon may be palpated when it lies so deeply. In one autopsy study, 42% of piriformis tendons fused with the obturator internus (and 3% with the gluteus medius). Perhaps piriformis syndrome ought to be alternatively termed obturator internus syndrome. True anatomic piriformis syndrome, if it occurs, is rare. Severe sciatic neuropathy following piriformis section should give one even more pause, before making, and acting on, this illusory diagnosis.