The Shape of the Greater Sciatic Foramen in Adults Based on Computed Tomography Data

The greater sciatic foramen (GSF) is a passageway for important neurovascular bundles of the pelvis and lower limb, making it a potential site for compression of these structures. Investigating the features of morphological variability in this region helps to identify the predisposing factors for neurological disorders, optimizes surgical approaches, and reduces the number of iatrogenic injuries to blood vessels and nerves. The aim of the study is to evaluate the variability in the shape of the bony margins of the greater sciatic foramen, characteristic of mature adult males and females, for subsequent application in clinical practice. Material and methods. The results of multispiral computed tomography scans of 70 patients aged 20–59 years were analyzed; linear and angular parameters of the foramen were determined on three-dimensional pelvic models . Geometric morphometrics was used to analyze the configuration of the GSF based on 20 landmarks placed on its bony margins. Results. Based on the linear and angular dimensions, four main shapes of the GSF were identified: deltoid, parallelogram, trapezoid, and irregular quadrilateral. It was established that the deltoid shape is statistically significantly more common in women, while the parallelogram shape is more common in men. The incidence of the trapezoid and irregular quadrilateral shapes did not differ significantly between the sexes. The geometric morphometric analysis revealed significant sex-related differences in the shape of the GSF. These variations are concentrated along a single canonical axis and are determined by the shape of the greater sciatic notch of the hip bone. Males are characterized by greater depth and concavity in the superior part of the notch, whereas females exhibit greater depth and concavity in its inferior part. Conclusion. Currently, there is no universal reference method for the precise determination of the GSF shape. The most reliable results can only be achieved through an integrated approach that combines traditional linear measurements with modern geometric morphometric methods.

1. Belash VO, Petrova EA. Sindrom grushevidnoj myshcy. Rossijskij osteopaticheskij zhurnal. 2022;(3):131-156. (In Russ.) doi: 10.32885/2220-0975-2022-3-131-156.

2. Yudin AL, Shomakhov MA, Yumatova EA, Abovich YuA. Sindrom grushevidnoj myshcy. Lechenie pod kontrolem KT-skopii. Zhurnal nevrologii i psihiatrii im. S.S. Korsakova. 2020; 120 (10):85–90. (In Russ.). doi: 10.17116/jnevro202012010185.

3. Gomes BA, Ramos MR, Fiorelli RK, Almeida CR, Fiorelli SK. Topographic anatomical study of the sciatic nerve relationship to the posterior portal in hip arthroscopy. Rev Col Bras Cir. 2014 Nov-Dec;41(6):440-4. English, Portuguese. doi: 10.1590/0100-69912014006010.

4. Sermer C, Li ALK, Fernandes GL, Ribeiro AM, Polesello G, Tokechi D, Cancelliere L, Lemos N. Intrapelvic entrapment of sacral nerve roots by abnormal bundles of the piriformis muscle: description of an extra-spinal cause of sciatica and pudendal neuralgia. J Hip Preserv Surg. 2021 May 19;8(1):132-138. doi: 10.1093/jhps/hnab041.

5. Pokorný D, Jahoda D, Veigl D, Pinskerová V, Sosna A. Topographic variations of the relationship of the sciatic nerve and the piriformis muscle and its relevance to palsy after total hip arthroplasty. Surg Radiol Anat. 2006 Mar;28(1):88-91. doi: 10.1007/s00276-005-0056-x.

6. Yürük D, Can E, Genç Perdecioglu GR, Yıldız G, Akkaya ÖT. Prevalence of priformis syndrome in sciatica patients: Predictability of specific tests and radiological findings for diagnosis. Br J Pain. 2024 Oct;18(5):418-424. doi: 10.1177/20494637241254349.

7. Probst D, Stout A, Hunt D. Piriformis Syndrome: A Narrative Review of the Anatomy, Diagnosis, and Treatment. PM R. 2019 Aug;11 Suppl 1:S54-S63. doi: 10.1002/pmrj.12189.

8. Kim DH, Lee SH, Lee SS, Kim YS, Park DK, Han SH, Lee UY. Comprehensive evaluation of the greater sciatic notch for sexual estimation through three-dimensional metric analysis using computed tomography based models. Leg Med (Tokyo). 2018 Nov;35:1-8. doi: 10.1016/j.legalmed.2018.09.006.

9. Gómez-Valdés JA, Quinto-Sánchez M, Menéndez Garmendia A, Veleminska J, Sánchez-Mejorada G, Bruzek J. Comparison of methods to determine sex by evaluating the greater sciatic notch: Visual, angular and geometric morphometrics. Forensic Sci Int. 2012 Sep 10;221(1-3):156.e1-7. doi: 10.1016/j.forsciint.2012.04.027.

10. Kilmer K, Garvin H. Outline analysis of sex and population variation in greater sciatic notch and obturator foramen morphology with implications for sex estimation. Forensic Sci Int. 2020 Sep;314:110346. doi: 10.1016/j.forsciint.2020.110346.

11. Adibatti M, V S. Study on variant anatomy of sciatic nerve. J Clin Diagn Res. 2014 Aug;8(8):AC07-9. doi: 10.7860/JCDR/2014/9116.4725.

12. Mitteröcker Ph, Gunz Ph. Advances in geometric morphometrics. In: Evolutionary Biology. 2009;36(2):235-247. doi: 10.1007/s11692-009-9055-x.

13. Knecht S, Nogueira L, Servant M, Santos F, Alunni V, Bernardi C, Quatrehomme G. Sex estimation from the greater sciatic notch: a comparison of classical statistical models and machine learning algorithms. Int J Legal Med. 2021 Nov;135(6):2603-2613. doi: 10.1007/s00414-021-02700-1.

14. Slice DE. Geometric Morphometrics. Annual Review of Anthropology. 2007 Dec;36:261-281. doi:10.1146/annurev.anthro.34.081804.120613