PainSci summary of Natsis 2014: ?This page is one of thousands in the PainScience.com bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided at the bottom of the page, as often as possible.
This dissection study of 275 dead buttocks found that 6.4% of them had variations of sciatic nerve and piriformis muscle anatomy, with considerable variety in the variation. They found several different arrangements, and concluded: “Some rare, unclassified variations of the sciatic nerve should be expected during surgical intervention of the region.” Prepare to be surprised, surgeons!
All of these differences are potentially clinically significant, probably especially in the cases where the nerve (or part of it) passes right through the muscle. For a couple case studies, see Arooj 2014 and Kraus 2015.
original abstract †Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.
PURPOSE: To detect the variable relationship between sciatic nerve and piriformis muscle and make surgeons aware of certain anatomical features of each variation that may be useful for the surgical treatment of the piriformis syndrome.
METHODS: The gluteal region of 147 Caucasian cadavers (294 limbs) was dissected. The anatomical relationship between the sciatic nerve and the piriformis muscle was recorded and classified according to the Beaton and Anson classification. The literature was reviewed to summarize the incidence of each variation.
RESULTS: The sciatic nerve and piriformis muscle relationship followed the typical anatomical pattern in 275 limbs (93.6 %). In 12 limbs (4.1 %) the common peroneal nerve passed through and the tibial nerve below a double piriformis. In one limb (0.3 %) the common peroneal nerve coursed superior and the tibial nerve below the piriformis. In one limb (0.3 %) both nerves penetrated the piriformis. In one limb (0.3 %) both nerves passed above the piriformis. Four limbs (1.4 %) presented non-classified anatomical variations. When a double piriformis muscle was present, two different arrangements of the two heads were observed.
CONCLUSIONS: Anatomical variations of the sciatic nerve around the piriformis muscle were present in 6.4 % of the limbs examined. When dissection of the entire piriformis is necessary for adequate sciatic nerve decompression, the surgeon should explore for the possible existence of a second tendon, which may be found either inferior or deep to the first one. Some rare, unclassified variations of the sciatic nerve should be expected during surgical intervention of the region.
- “Piriformis Syndrome with Variant Sciatic Nerve Anatomy: A Case Report,” Emily Kraus, Adam S Tenforde, Christopher F Beaulieu, John Ratliff, and Michael Fredericson, PM & R: The Journal of Injury, Function, and Rehabilitation, 2015.
- “Piriformis syndrome--a rare cause of extraspinal sciatica,” Shumaila Arooj and Muhammad Azeemuddin, J Pak Med Assoc, 2014.
- “Piriformis syndrome: a real pain in the buttock?,” Ryan J Halpin and Aruna Ganju, Neurosurgery, 2009.
This page is part of the PainScience BIBLIOGRAPHY, which contains plain language summaries of thousands of scientific papers & others sources. It’s like a highly specialized blog. A few highlights:
- Relationships Between Sleep Quality and Pain-Related Factors for People with Chronic Low Back Pain: Tests of Reciprocal and Time of Day Effects. Gerhart 2017 Ann Behav Med.
- Modulation in the elastic properties of gastrocnemius muscle heads in individuals with plantar fasciitis and its relationship with pain. Zhou 2020 Sci Rep.
- Association Between Plantar Fasciitis and Isolated Gastrocnemius Tightness. Nakale 2018 Foot Ankle Int.
- No Added Benefit of Combining Dry Needling With Guideline-Based Physical Therapy When Managing Chronic Neck Pain: A Randomized Controlled Trial. Stieven 2020 J Orthop Sports Phys Ther.
- Effectiveness of customised foot orthoses for Achilles tendinopathy: a randomised controlled trial. Munteanu 2015 Br J Sports Med.