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Morphologic and morphometric bilateral analysis and sexual dimorphism in sciatic nerves of adult cadaveric specimens in Uganda

BMC Musculoskeletal Disorders volume 26, Article number: 422 (2025) Cite this article

Abstract

Background

The Sciatic nerve (SN) exhibits distinct sex and side-related differences, which have significant implications for clinical practice. The study investigated the sex and side-related morphologic and morphometric variations of the nerve using cadavers.

Methods

This is a cross-sectional cadaveric study involving 62 Ugandan cadavers. Continuous variables were reported using descriptive statistics and discrete variables were reported as percentages. Ordinary two-way ANOVA was used to compare the dimensions and proportion of the patterns of the SN.

Results

The study identified six categories of exit patterns of the SN, type A (“Below and undivided”) occurred in a majority of cases (62.9%). A penta-furcate branching pattern dominated the whole population. Bifurcate termination pattern was found in most SNs (90.3% and 87.1% for right and left limbs respectively) while the rest have the trifurcate termination pattern, with no side or sex-related variations. The average dimensions of SN were within normal ranges, and showed no side-related differences but with a sex difference (significantly higher in males than females), mean length of the SN in centimetres (length A: Males, right limbs = 30.58 ± 9.00; left limbs = 31.30 ± 6.20; Females, right = 26.07 ± 6.58; left = 26.30 ± 5.56). The difference in the length “A” for the males left limb and females right limb was statistically significant with a p-value of 0.0195.

Conclusions

Most of the examined SNs showed normal anatomical characteristics with rare cases of sex-related dimorphism in the termination level and morphometry (length and diameter) of the nerve. The observed sexual dimorphisms in sciatic nerves are of clinical and surgical interest; hence, suggesting the need for further investigations in different populations, especially using advanced techniques such as ultrasonography anatomic techniques.

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Background

The sciatic nerve originates from the lumbosacral plexus composed of the ventral rami of L4-S3 spinal nerves in the pelvic region; the sciatic nerveis the largest branch of the lumbosacral plexus [1]. As the thickest and longest nerve in the human body, the sciatic nerve originates in the gluteal region, traverses the posterior thigh to the popliteal fossa, and extends all the way to the heel of the foot [2, 3]. At the lumbosacral plexus, it measures about 2 cm in width and originates from the posterior pelvis, passing through the greater sciatic foramen and the lower portion of the piriformis muscle [4,5,6,7]. The sciatic nerve finally travels along the posterior aspect of the thigh, encased in a fatty sheath, until it reaches the popliteal fossa (approximately 7 cm above the transverse popliteal crease). At this point, it splits into its two terminal branches: the tibial and common peroneal nerves, extending as far as the hallux [4, 8].

The tibial nerve gives rise to (1) the muscular branches which innervate thehamstring muscles of the thigh and the muscles of the posterior compartment of the leg and 2) the medial sural cutaneous nerve, a terminal branch of the tibial nerve which in the distal third of the calf joins with the terminal branch of the common fibular nerve (lateral sural cutaneous nerve) to form the sural nerve. The common peroneal nerve gives rise to1) the deep fibular nerve which provides muscular branches to innervate the muscles of the anterior compartment of the leg, (2) the superficial fibular nerve which gives off muscular branches to supply the muscles of the lateral compartment of the leg, and (3) the lateral sural cutaneous nerve, a terminal branch of the common fibular nerve which joins the medial sural cutaneous nerve from the tibial nerve to form the sural nerve [1, 9, 10]. Therefore, this makes the sciatic nerve the dominant nerve of the lower limb [1, 10].

The pelvic region, specifically the gluteal region is of considerable clinical value due to the presence of various structures notably the sciatic nerve [11, 12]. The piriformis muscle is key in the gluteal region due to its association with the sciatic nerve [13, 14]. Variants of the sciatic nerve have been widely documented in terms of its topography and exit pattern from the pelvis [6, 7, 15], divisionsand relations in the thigh [16], and termination pattern that pertains to the popliteal crease [5, 17]. Variations of the Sciatic nerve in the population are important clinically since they are usually linked to nerve compression and entrapment syndromes such as sciatica [18, 19], piriformis syndrome [5, 20,21,22], accidental iatrogenic damage to the nerve during invasive procedures [23, 24], injection-induced and post-injection damage to the sciatic nerve and paralysis following intragluteal intramuscular injection [2, 25,26,27]. Anatomical variations of the sciatic nerve make it challenging to accurately trace and locate its path, leading to high failure rates of certain invasive procedures [28, 29]. A notable example is the high failure rate (21%) of popliteal sciatic nerve blocks in a Ugandan population, primarily due to the difficulty in identifying the main trunk of the nerve before its termination [30]. These variations in the nerve’s termination pattern are crucial during the administration of regional sciatic nerve blocks for surgeries below the knee [30].

The exit nature of the sciatic nerve from the pelvis and its relation with the piriformis muscle [14, 15, 31, 32], course and muscular branching patterns of the sciatic nerve in the thigh [16], level of terminal division of the nerve into the tibial and common peroneal nerves [17, 29], show numerous anatomical variations that are of crucial clinical importance. The morphometric features and variations of the sciatic nerve that pertain to its dimensions (length, diameter, width) at different levels during its course in the gluteal and thigh regions are also of clinical importance [33, 34]. Finding from the present study could help develop public health program aimed at preventing injury to the sciatic nerve; surgical injuries due to human error could also be prevented by understanding the anatomical variations of the sciatic nerve [16, 20, 33,34,35,36].

There is still a dearth of data regarding the anatomical variations of the sciatic nerve in sub-Saharan populations like Uganda and Africa at large yet the nerve presents significant variations in its divisions and topography [2, 25, 30, 33, 37, 38], therefore it is crucial to investigate the topography, divisions, and related anatomical variations of the nerve that pertains to its exit pattern from the pelvis, branching pattern within the thigh, termination pattern, and morphometric features among such populations. The current study is crucial since topographic and morphometric variations of the sciatic nerve differ among populations [7, 38, 39]. Although sexual dimorphism of the sciatic nerve [33, 40] and bilateral sciatic nerve variations [23] have been reported, the concept of bilaterality and sex differences in anatomical structures are not usually consistent for all structures and populations [37, 41,42,43]. Understanding the typical and variant bilateral anatomical characteristics of the sciatic nerve in both sexes in terms of its exit, branching, termination, and morphometric patterns is important for the prevention of iatrogenic injuries and complications during surgical procedures and the successful conduction of surgical procedures involving the lower limb. Hence, this study was designed to examine the morphology of the sciatic nerve and its variations in terms of its exit pattern from the pelvis, branching pattern within the thigh, termination pattern, and morphometric dimensions in adults of both sexes to establish side and sex-related dimorphic differences in these features.

Methods

Study design

The study was a cross-sectional analytical one, conducted at two Laboratories of the Department of Anatomy of Kampala International University (KIU), Western Campus, Ishaka, Bushenyi in Western Uganda. It was carried out in conformity with the 1975 Helsinki Declaration, amended in 2013 [44], and following approval from the Institutional Review and Ethics Committee (IREC) of KIU. A total of 62 adult formalin-fixed cadavers (31 males and 31 females) in the Anatomy Laboratory of the Department of Anatomy of KIU were used for the study. The sample specimens (31 male and 31 female lower limb cadavers) were randomly picked (random number algorithm in Microsoft Excel 2019). The lower limb of cadavers possessing any gross pathology were excluded from the study.

Embalming of the cadavers was carried out in the Anatomy Department of KIU using a standard method [33]. Following the embalming, the bodies were stored in the laboratory storage tanks with a solution of formalin for four weeks before conducting dissections. To expose, trace and study the sciatic nerve, the gluteal and posterior thigh regions were dissected following established guidelines [45], as described previously [46], with modifications. After cutting and reflecting off the gluteus maximus and biceps femoris muscles, the sciatic nerve was exposed at the lower part of the gluteal region and upper part of the thigh respectively. The connective and fatty tissues were excised for proper appreciation, following, and assessment of the nerve [45, 46], in terms of its morphometry (lengths and diameters at different points) [33, 47,48,49] and morphology in terms of its exit from the greater sciatic foramen and relationship with piriformis (exit pattern), muscular branching pattern of the nerve to the muscles of the posterior compartment of the thigh (branching pattern), and point and the number of terminal divisions of the nerve (termination pattern) [17, 28, 30, 48, 50,51,52,53,54]. The dimensions, exit, branching, and termination patterns of the nerve were recorded. Also, images of the anatomical variations of the exit, branching, and termination patterns of the sciatic nerve were documented using a digital camera.

Analytical procedures

Exit, branching, and termination patterns of the cadaveric sciatic nerves

The exit patterns of the sciatic nerves refer to variations of the sciatic nerves at their point of exit from the pelvis in relationship with the piriformis muscle [7, 15] and these patterns were classified using previous methods with some modifications [50, 51]. In the current study the exit patterns were denoted as types A, B, C, D, E, F, and G, simplified as: “Below and undivided”, “Below and divided”, “Above and undivided”, “Above and divided”, “Within and undivided”, “Within and divided”, and“divided in the pelvis, Below and divided” respectively [13, 50, 51]. These patterns are defined as follows: Type A (Below and undivided)-undivided SN goes inferior to the piriformis; Type B (Below and divided)- the division of SN occurring below the piriformis with one part passing in front of the muscle and the other part below it; Type C (Above and undivided)- undivided SN goes superior to the piriformis; Type D (Above and divided)- the division of SN occurring above the piriformis with one part passing in front of the muscle and the other part above it; Type E (Within and undivided)-course of SN undivided through the piriformis muscle; Type F (Within and divided)-course of SN divided through the piriformis muscle [13, 50, 51].

The muscular branching pattern of the sciatic nerve refers to the way the sciatic nerve divides during its course (and related to the sciatic artery) within the thigh, aiding the innervation of the muscles of the posterior compartment of the thigh [16, 55]. The branching patterns of the sciatic nerves were assessed by observing the course and number of muscular branches of the nerve within the thigh in a similar way to previous studies [48, 52, 53].

The termination pattern of the sciatic nerve refers to the level of terminal division and the number of terminal branches of the sciatic nerve, also related to the sciatic artery [55,56,57]. The number of terminal branches of the nerve was investigated by observing the number of terminal divisions (bifurcation or trifurcation) given off by the sciatic nerve at its point of termination using methods from previous studies [17, 30, 54]. The level at which the nerve terminates into its terminal branches(common peroneal and tibial nerves) was precisely investigated by measuring the perpendicular length from the point of terminal division of the sciatic nerve to the transverse popliteal crease (length B) which corresponds to the point at which the sciatic nerve is divided into its terminal divisions [28]. Representative photographs of the different exit, branching, and termination patterns of the sciatic nerve were captured with an Olympus Stylus 600 6MP digital camera. The findings on the numerous categories of the exit, branching, and termination patterns of the nerve for the right and left limbs among the 31 male and 31 female cadavers were presented in terms of percentages and numbers, and data from the right and left limbs, as well as male and female cadavers, were compared.

Morphometric dimensions of the cadaveric sciatic nerves

The measurements presented in the study were made using established guidelines [15, 33] with modifications, and the topographical dimensions of sciatic nerves were determined following previous methods [33, 47,48,49] by measuring two categories of dimensions for each sciatic nerve (sciatic nerve length and diameter). Sciatic nerve length: the major longitudinal axis of the nerve and this was measured in two ways: (i) length of the sciatic nerve from the lower border of piriformis muscle to the point of terminal division of the nerve (length A); (ii) length of the terminal division of the sciatic nerve from the point of the terminal division of the sciatic nerve to the transverse popliteal crease (length B). Sciatic nerve diameter: the major transverse axis of the sciatic nerve was measured at three points: (i) at the exit point (exit diameter of the sciatic nerve)- diameter of the sciatic nerve at the level of the lower border of the piriformis muscle; (ii) at mid-thigh point (mid-thigh diameter of the sciatic nerve)- diameter of the sciatic nerve at the level of the mid-thigh; (iii) at the level of terminal division of the nerve (terminal end diameter of the sciatic nerve)- diameter of the sciatic nerve measured at its point of terminal division [33, 47,48,49]. All the measurements were performed three times, and the diameters were measured with a digital vernier caliper(Mitutoyo 500–153Absolute Caliper 0-300 mm Range-SPC) and presented in millimetress, while the lengths were measured using a meter rule(Mitutoyo 182 − 125, Steel Rule, 12”/300 mm), reported in centimeters.

Statistical analysis

Statistical analyses were done using GraphPad Prism Version 6.0 (Graph Pad Software Inc.), and the data was presented in the form of graphs and tables. Categorical/discrete variables (types of exits, branching, and termination patterns of the cadaveric sciatic nerves of male and female cadavers) were reported as percentages; continuous variables (dimensions of each sciatic nerve in both limbs and sexes) were reported in the form of descriptive statistics (range, median, mean, and standard deviation). Ordinary two-way ANOVA (Tukey’s multiple comparisons test) was used to compare the dimensions of different sciatic nerves and to compare the different prevalences/percentages of the various patterns (exit, branching, and termination) of the sciatic nerves for both limbs and sexes. p values < 0.05 were considered statistically significant.

Results

Exit, branching, and termination patterns of the cadaveric sciatic nerves

Exit patterns of the sciatic nerves

The study identified six categories of exit patterns in the sciatic nerves of the population (Fig. 1A-F). “Below and undivided” type of exit was the most prevalent (62.9%) in both right and left limbs, while the least prevalent were the “Above and divided” and “Within and divided” types accounting for 1.6% and 4% respectively in both limbs (right and left). Among the male population, the most prevalent was the “Below and undivided” type (64.5% for right limbs; 61.2% for left limbs); similarly, the most prevalent exit pattern in the female population is the “Below and undivided” type (61.2% for right limbs; 64.5% for left limbs) with no significant (P > 0.05) variation in the prevalence of “Below and undivided” exit pattern of right compared to the left limbs for both sexes. Also, there was no significant (P > 0.05) difference in the prevalence of the exit pattern (Below and undivided) of males compared to females. But there was a significant (P < 0.05) difference in the prevalence of the “Below and undivided” exit pattern compared to the prevalence for the rest of the five exit patterns (details in Table 1 and Fig. 1A-F).

Fig. 1
figure 1

Photographs of the gluteal and posterior aspects of the thigh representing: the exit patterns (A-F); branching patterns (G); and terminations patterns (a&b) of the cadaveric sciatic nerves in the general Ugandan population. N = 62. A. Type A (Below and undivided); undivided SN goes inferior to the piriformis.B. Type B (Below and divided); division of SN occurring below the piriformis with one part passing in front of the muscle and the other part below it. C. Type C (Above and undivided); undivided SN goes superior to the piriformis.D. Type D (Above and divided); division of SN occurring above the piriformis with one part passing in front of the muscle and the other part above itE. Type E (Within and undivided); course of SN undivided through the piriformis muscle. F. Type F (Within and divided); course of SN divided through the piriformis muscle. G.The “Pentafurcate branching pattern”; SNshowedfive divisions during its course in the posterior compartment of the thigh.a. Birfucate termination pattern; SN divides into two terminal branches.b. Trifurcate termination pattern; SN divides into three terminal branches. Abbreviations. CPN = common peroneal nerve; SN = sciatic nerve; TN = tibial nerve. N = the total number of the sample

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Table 1 The percentages of the different exit, branching, and termination patterns of the bilateral cadaveric sciatic nerves in the male and female Ugandan populations. n = 31; N = 62
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Branching patterns of the sciatic nerves

Only one category of branching pattern was identified in the sciatic nerves of the population, i.e., Penta furcate branching type (Fig. 1G). In assessing the frequencies and percentages of branching patterns of sciatic nerve among the whole population, the whole population (100%) was found to have a Penta furcate type of branching pattern (details in Table 1,,and Fig. 1G, and Table 2).

Table 2 Descriptive analysis of the bilateral morphometric dimensions of the cadaveric sciatic nerves in the male and female Ugandan populations. n = 31; N = 62
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Termination patterns of the sciatic nerves

In assessing the occurrence of termination patterns, we identified two categories of termination patterns of the sciatic nerves (bifurcate and trifurcate) (Fig. 1a and b). The most prevalent terminal pattern was of the bifurcate termination pattern (90.3% and 87.1% of cases for right and left limbs respectively). The trifurcate termination pattern was the least prevalent (occurs in 9.7% and 12.9% of cases of right and left limbs respectively). Among the male population, the most prevalent was the bifurcate termination pattern (93.5% for right limbs; 83.9% for left limbs); similarly, the most prevalent termination pattern in the female population is the bifurcate termination pattern (87.1% for right limbs; 90.3% for left limbs) with no significant (P > 0.05) variation in the prevalence of bifurcate termination pattern of right limbs compared to the left limbs for both sexes. There was no significant (P > 0.05) difference in the prevalence of the trifurcate termination pattern in males compared to females. However, there was a significant (P < 0.05) difference in the prevalence of the bifurcate termination pattern compared to that of the trifurcate termination pattern for both limbs and sexes (details in Table 1, and Fig. 1a-b).

Bilateral morphometric dimensions of the cadaveric sciatic nerves

Lengths of the sciatic nerves

The mean length of the sciatic nerves from the lower border of the piriformis muscle to the point of terminal division of the nerves (length A) was evaluated among the subjects. Among the male cadavers, the average length A was 30.58 ± 9.00 cm (right limbs) and 31.30 ± 6.20 cm (left limbs), with no significant(P > 0.05) difference between length A of right limbs compared to length A of left limbs. Among the females, the average length A was 26.07 ± 6.58 cm (right limbs) and 26.30 ± 5.56 cm (left limbs), with no significant(P > 0.05) difference between length A of right limbs compared to length A of left limbs. There was a significant (P < 0.05) variation in sciatic nerve length A of males compared to that of females on both limb (Tables 2 and 3).

Table 3 Multiple comparisons on bilateral morphometric dimensions of the cadaveric sciatic nerves in the male and female Ugandan populations. n = 31; N = 62
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We also evaluated the mean perpendicular length from the point of the terminal division of the sciatic nerves to the transverse popliteal crease (length B). Among the male population, the mean length B was 8.5 ± 4.1 cm and 8.2 ± 3.9 cm for right and left limbs respectively; among the female population, the mean length B was 7.76 ± 3.8 cm and 7.82 ± 3.5 cm for the right and left limbs respectively. There was no significant(P > 0.05) variation in the average length B of right and left limbs in both sexes, and this length did not differ significantly (P > 0.05) in males compared to females (details in Tables 2 and 3).

Diameters of the sciatic nerves

The mean diameter of the sciatic nerves at the level of the lower border of the piriformis muscle (mean exit diameter of the sciatic nerves) was found to be 11.69 ± 1.92 mm (right limbs), 11.67 ± 2.16 mm (left limbs) among the male population; with no significant(P > 0.05) difference in the mean exit diameter of the right limbs compared to the left limbs among the male population. Among the female population, the average exit diameter was 8.41 ± 2.24 mm (right limbs) and 9.28 ± 1.99 mm (left limbs), with no significant (P > 0.05) variation in the average exit diameter of the right limbs compared to left limbs among females. However, the mean exit diameter of the sciatic nerve in male individuals was significantly(P < 0.05) higher than the mean exit diameter of the female population in both the right and left limbs.

The mean diameter of the sciatic nerves at the level of the mid-thigh (mid-thigh diameter) was assessed and the mean mid-thigh diameter was 8.86 ± 1.56 mm and 9.64 ± 1.88 mm for right and left limbs among the male individuals, with no significant(P > 0.05) disparity in the mean diameter of right and left limbs. The mean mid-thigh diameter was 7.12 ± 1.46 mm and 8.28 ± 1.89 mm (right and left limbs respectively) among females, with no statistical difference (P > 0.05) in average mid-thigh diameter of the nerves of the right limbs compared to the left limbs. The mean mid-thigh diameter of the nerves was statistically(P < 0.05) higher in males than in females for both sides of the limbs.

The terminal end diameter of the sciatic nerves was considered as the diameter of the sciatic nerves measured at its point of terminal division. The mean terminal end diameter among males was 9.47 ± 2.07 mm (right limbs) and 9.86 ± 2.32 9 mm (left limbs), with no significant (P > 0.05) variability in the mean terminal end diameter of the nerve in right limbs compared to the mean diameter of the nerve in the left limbs in males. Regarding the female population, the mean terminal end diameter of the nerve was 7.5 ± 1.62 mm (right limbs) and 8.4 ± 2.24 mm (left limbs), with no significant difference in the mean terminal end diameter of the nerve in right limbs compared to the left limbs (P > 0.05) in females. However, the average terminal end diameter of the nerve was significantly (P < 0.05) higher in males compared to females for both sides of the limbs (Tables 2 and 3).

Discussion

Anatomical variations of the sciatic nerves are clinical roles [35, 52, 58], such as the causation and treatment of pathophysiologies like sciatica due to sciatic nerve compression [6, 18], piriformis syndrome [6, 20], injection-induced and post-injection damage to the sciatic nerve and paralysis [26, 27], and is also essential for clinicians and surgeons carrying out procedures involving the hip and sacroiliac joints such asthe location of the main trunk of the sciatic nerve before its termination and successful popliteal sciatic nerve block [6, 7, 28]. These conditions and procedures are highly dependent on the anatomical variations in the course and morphometric characteristics of the sciatic nerve knowledge of which is crucial [29, 59, 60].

The exit patterns of the sciatic nerves at the point of its exit from the pelvis in relationship with the piriformis muscle vary widely and these variations are of clinical significance not forgetting variations in the artery to sciatic nerve too [15, 55]. The course and muscular branching patterns of the sciatic nerves in the thigh vary greatly in terms of the furcation patterns and it is vital to evaluate these branching patterns [16]. The level of terminal division of the sciatic nerve into the tibial and common peroneal nerves occurs in the popliteal fossa in most people, but this division is observed higher in the thigh or gluteal area in a minority of the population [17]. Also, the morphometric variations of the nerve in terms of its diameter and length at various levels within the thigh is another anatomical variation associated with vital clinical significance [33, 34].

In recent times, studies have indicated beneficial health and the ability to curb surgical complications and better performance of surgical procedures being linked to a proper understanding of the anatomical variations of the sciatic nerve [7, 16, 20, 27, 29, 33,34,35,36]. However, there is little Africa-specific data on the pattern, morphometry, and anatomical variations of the sciatic nerve [33, 37, 38], and the current study is one of the few that have been done to examine the variations of the morphometric features, pattern, and bilateral and sex-related variability of the nerve in males and females [33, 56], especially in the Ugandan context [30]. Although most sciatic nerves in the population showed the normal types of exit, branching, and termination patterns (type A, pentafurcate, and bifurcate respectively), with no side or sex-related variability, a minority of the population showed variants in the exit and termination patterns, as well as in morphometry of the sciatic nerves. Again, the study has found sex-related dimorphism in the level of termination and morphometry of the sciatic nerve in both limbs of the same specimen.

The exit patterns of the sciatic nerves refer to the anatomical variations of the sciatic nerves at the point of their exit from the pelvis in relationship with the piriformis muscle [15]. The six categories of the exit patterns of the sciatic nerve (Below and undivided, Below and divided, Above and undivided, Above and divided, Within and undivided, Within and divided) identified in our study correspond with types A, B, C, D, E, and F found in previous reports [13, 50], but differs from another analytical study [51] where an additional exit pattern (type G) with the nerve dividing in the pelvis, and the common peroneal and tibial nerves coursing separately below the piriformis muscle was found [51]. Again, the current study is inconsistent with a previous report in Kenya where around 20% of the 82 cadavers showed the nerve to be dividing high within the pelvis, with 5% of them having the common peroneal and tibial nerves reuniting [39], also another exit pattern where the sciatic nerve divided higher in the thigh or gluteal area was indicated using MRI on American population [17]. The most common type of exit pattern (which occurs in 62.9% of the population) found currently in both limbs is the normal type A (Below and undivided), where the sciatic nerve exits the pelvis as a single entity below the piriformis muscle, followed by type F (Above and undivided), where the undivided nerve passes superior to the piriformis (23.3%), and the least common is of the “Above and divided”, “Within and divided” types accounting for 1.6% and 4% respectively in both limbs. The current findings where types A and B have been found as the most predominant types in the whole population, without significant differences among males and females, and with no significant differences between the right and left sides (bilaterally) correspond to most studies [17, 39, 50, 51].

The muscular branching pattern of the sciatic nerve refers to the way the sciatic nerve divides during its course within the thigh, aiding the innervation (motor supply) to the muscles of the posterior compartment of the thigh. There is a dearth of data on the muscular branching pattern of the sciatic nerve concerning the hamstring muscles, more anatomical information is necessary to improve understanding and improve surgical procedures associated with the nerve [16]. Our data demonstrated that the whole population (males and females) of cadavers had a “pentafurcate” type of muscular branching pattern in both limbs, where the sciatic nerve divided into five muscular branches within the thigh and the muscular branch divisions penetrated the corresponding muscles of the posterior compartment of the thigh (semimembranosus, short and long head of biceps femoris, hamstring portion of the adductor magnus, and semitendinosus muscles), this is consistent with a previous study [16], but data regarding the sex-related variability in the branching pattern was not provided by Bretonnier et al. [16] unlike currently.

The termination pattern of the sciatic nerve refers to the level of terminal division and the number of terminal branches of the sciatic nerve [56, 57]. The perpendicular length from the point of the terminal division of the sciatic nerve to the transverse popliteal crease (length B) of the current study corresponds to the point at which the sciatic nerve is divided into its terminal divisions [28]. The variation in this level is important in the proper identification of the course and terminal branches of the nerve to perform a successful regional nerve block of the posterior thigh region [57, 61]. The current data showed that the average level at which the sciatic nerve divides into its terminal branches within the population was similar in both sexes and limbs, and this was about 8.1 ± 3.8 cm above the popliteal crease in both sexes and bilaterally. The identified current point of terminal division of the nerve corresponds to the normal (5–7 cm above the transverse popliteal crease) [35] but differs from a report in Uganda where the termination of the nerve was found to occur 12 cm above the transverse popliteal crease [30]. The current data suggest that the sciatic nerve divides into its terminal branches in the popliteal fossa (8.1 ± 3.8 cm above the popliteal crease) in the majority of the cases in both sexes and bilaterally, although the division of the nerve also occurs higher in the thigh/gluteal regions since the termination of the nerve was also found to occur 9–19.6 cm above the transverse popliteal crease in some cases. The current findings are in tandem with a previous report where in most cases, the sciatic nerve divided into the common peroneal and tibial nerves in the popliteal fossa, but in a few individuals (27.5%), the division of the nerve was higher in the thigh or gluteal areas [17].

In examining the number of terminal branches of the sciatic nerve, it was found that the “bifurcate” termination pattern, where the nerve divides into two terminal branches was significantly more common in both sexes and bilaterally (average of 90.3% and 87.1% of cases for right and left limbs respectively), and corresponds with the majority of reports where the sciatic nerve normally gives two terminal branches(common peroneal and tibial nerves which course separately) [17, 30, 46, 51, 61], however, the remainder of cases had a “trifurcate” termination pattern (sciatic nerve with three terminal branches; 9.7% and 12.9% cases in right and left limbs respectively). The occurrence of both the bifurcation and trifurcation termination patterns of the sciatic nerve observed currently concurs with an Ethiopian study [56, 61].

The average length of the sciatic nerve from the lower border of the piriformis muscle to the point of terminal division of the nerve (length A) among the male population (30.58 ± 9.00 cm for right limbs; 31.30 ± 6.20 cm for left limbs) was similar bilaterally (in both limbs) and markedly higher compared to that of females (26.07 ± 6.58 cm-right limbs; 26.30 ± 5.56 cm-left limbs), the current length of the sciatic nerve shows consistency with a Nigerian population study where the mean length of the sciatic nerve from the lower edge of the piriformis to the point of its terminal division was significantly higher in males (37.58 ± 5.26 cm) compared to females (31.5 ± 3.37 cm) [33]. The disparity in sciatic nerve length between male and female populations is attributed to the topographic anatomical variations in both sexes that are associated with landmark structures around the pelvis and lower limb [7, 33, 35]. Therefore, further studies are required to examine the exact relationship between pelvic and lower limb morphology, morphometric features of the lower limb and pelvis, and sciatic nerve morphometry. Such landmark features around the pelvis and lower limb that may be related to sciatic nerve morphometry include but are not limited to the distance between the greater trochanter and apex of the ischial tuberosity, the distance between the greater trochanter and posterior superior iliac spine, length of the lower limb, tip of the greater trochanter to the vertical distance between the lateral edge of sciatic nerve intersection with piriformis, ischial tuberosity to the vertical distance between medial edge of sciatic nerve intersection with piriformis, posterior superior iliac spine to the vertical distance between the lateral edge of sciatic nerve intersection with piriformis, the distance between the ischial tuberosity and posterior superior iliac spine, length of the lower extremity [5, 15, 33, 59, 62].

The mean diameter of the sciatic nerve at the level of the lower border of the piriformis muscle (mean exit diameter of the sciatic nerve) among the male population was similar bilaterally, about 11.68 ± 2.04mmand markedly more compared to that of both sides in females (8.84 ± 2.12 mm), the data are closely related to a recent report among Nigerians; width of the sciatic nerve at the lower margin of the piriformis of males = 15.20 ± 2.93; and 14.05 ± 1.60 for females, and the values did not markedly vary in both limbs of the same specimen [33]. Our findings are inconsistent with previous findings where the diameter of the sciatic nerve on the inferior border of the piriformis muscle was18.85 mm on the right side and 22.32 mm on the left side [47]. The average diameter of the sciatic nerve at the level of the mid-thigh (mid-thigh diameter) did not vary in both limbs of the same cadaver, approximately 9.25 ± 1.72 mm among males, markedly lower in females (7.8 ± 1.67 mm), the data are consistent with a report that determined the diameter of the sciatic nerve within the thigh measured at 10 cm from the popliteal crease and found it to be 14.3 mm [63]. The mean terminal end diameter of the sciatic nerve, considered currently as the diameter of the sciatic nerve measured at its point of terminal divisions, did not vary for both sides of the same specimen but there was marked sex-related variability; in the male population, the mean terminal end diameter was 9.67 ± 2.19 mm vs. 7.95 ± 1.93 mm of females, and is closely similar to the mid-thigh diameter, consistent with previous reports [9, 63]. Although, the current study found no significant differences in the exit, mid-thigh, and terminal end diameter sizes of the sciatic nerve between both lower limbs of the same specimen, even, a Brazilian population study established a marked variation in the width value of sciatic nerve between both limbs of the same specimen [64].

The sexual dimorphism observed currently in the lengths (A and B) and diameters (exit, mid-thigh, and terminal end) of the sciatic nerve could be due to the sexual dimorphism of the topographic anatomical features in male and female individuals that determine the morphology of structures around the lower limb and pelvis, as well as the morphology of the lower limb and pelvis which might cause considerable deviations of sciatic nerve morphometry of females and males [33, 35, 55, 65]. This sex-related deviation of the nerve is of clinical significance in increasing the risk of damage to the sciatic nerve during injections and surgical procedures [15, 33, 34, 65]. The sexual dimorphic morphometric features of the sciatic nerve found currently are similar to those reported in a clinical radiological study associated with the morphometric relationship of the sciatic nerves in the knee region [40]. Future studies should consider the assessment of sciatic nerve morphometry in relationship to the topographic anatomic nature of males and females by measuring dimensions of the body and body structures around the pelvis, lower limb, etc. The current study found no bilateral variants in the exit, branching, and termination patterns, as well as morphometric dimensions of the sciatic nerves during its course from the pelvis to the gluteal region corresponding to most reports that suggest that bilateral variants in the gluteal region are rarely found in several anatomical studies [5, 13, 52, 66]. Nevertheless, bilateral variants in the course of the nerve have been reported previouslyin adult cadavers [23, 31], and knowledge of bilateral variations in the course of the sciatic nerve is vital in improving the prevention, diagnosis, treatment, and assessment of diseases in this area of the body [6, 7, 23, 31, 62].

The study had some limitations such as a lack of demographic details like age, occupation, ethnicity, and address, among others and medical anthropological histories such as family and medical histories of the cadaveric specimen was also unavailable which would have provided more interpretation in the topography, and variations of the pattern and morphometry of the sciatic nerves, and in prospective studies, such information could be considered to ensure more relevancy in the interpretation of the anatomical variations of the sciatic nerves. The data were got from embalmed cadavers, and it is possible that embalming might cause anatomical alterations, however, cadaveric anatomical findings are reliable sources of clinical data [35, 52]. Nevertheless, it looks proper for prospective studies to verify the findings and conduct similar investigations with more advanced techniques like ultrasonographic anatomy techniquesto compare the sciatic nerves in living individuals and to enable the comparison of cadaveric and living human data.

Conclusions

This study found out that the level of termination and morphometry (lengths and diameters) of the sciatic nerves have a sex effect (the level of termination, and morphometric dimensions of the sciatic nerves are markedly higher in males than females bilaterally). Although most sciatic nerves have depicted normal anatomical characteristics in terms of their topography, divisions, and morphometry, nevertheless, some specimens show a rare variation from these normal anatomical features. It is important to know the variations in the patterns (exit, branching, and termination) and morphometry (length and diameter) of the sciatic nerves for a proper understanding of the course and extent of the nerve and successful performance of clinical and surgical procedures such as regional nerve block of the posterior thigh and gluteal regions, as well as to avoid neuropathologies of the nerve during the procedures. The present study offers awareness of the range of morphological and morphometric variations in the sciatic nerves and provides the variations between limb sides and sexes. The observed sexual dimorphic morphometric/morphologic deviations are of great clinical and surgical interest, need to be considered during clinical and surgical procedures of the lower limb and pelvis/gluteal regions.

Data availability

Data associated with this study can be accessed at FigShare:https://figshare.com/s/afd5691507e67cc93fa4.

Abbreviations

ANOVA:

Analysis of variance

ASIS:

Anterior superior iliac spine

CPN:

Common peroneal nerve

IREC:

Institutional Review and Ethics Committee

KIU:

Kampala International University

L4:

Fourth lumbar vertebra

L5:

Fifth lumbar vertebra

MRI:

Magnetic resonance imaging

PSIS:

Posterior superior iliac spine

S1:

First sacral vertebra

S2:

Second sacral vertebra

S3:

Third sacral vertebra

SN:

Sciatic nerve

TN:

Tibial nerve

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Acknowledgements

Permission to use the cadavers was obtained from the Department of Anatomy, Kampala International University, western campus. The Laboratory Attendants and Technicians offered help in the Anatomy laboratories during the study.

Funding

Not applicable.

Author information

Authors and Affiliations

  1. Department of Anatomy, Faculty of Biomedical Sciences, Kampala International University, Western Campus, P.O Box 71, Ishaka, Bushenyi, Uganda

    Eric Simidi Kegoye, Abdulfatai Olakunle Ojewale, Ibe Michael Usman, Adesanya Olamide Adewale, Edgar Mario Fernandez & Okeniran Olatayo Segun

  2. Department of Human Anatomy, School of Medicine and Health Sciences, Kenya Methodist University, Main Campus, P.O Box 267, Meru, 60200, Kenya

    Eric Simidi Kegoye

  3. Department of Internal Medicine, Faculty ofMedicine, Kampala International University Teaching Hospital, P.O Box 71, Ishaka, Bushenyi, Uganda

    Winnie Ezekiel

  4. Department of Internal Medicine, Cardinal Rugambwa Hospital, P.O Box 40960, Dar es Salaam, Tanzania

    Winnie Ezekiel

  5. Department of Human Anatomy, Enugu State University of Science and Technology , PMB 01660, Enugu, Nigeria

    Eric Osamudiamwen Aigbogun

  6. Department of Physiology, School of Medicine, Kabale University, P.O Box 317, Kabale, Uganda

    Keneth Iceland Kasozi

  7. Department of Anatomy, Histology and Embryology, Faculty of Medicine, Mbarara University of Science and Technology, P.O Box 1410, Mbarara, Uganda

    Halima Nalugo

  8. Department of Anatomy, School of Medicine, Kabale University, P.O Box 317, Kabale, Uganda

    Isaac Echoru

  9. Department of Anatomy and Cell Biology, Faculty of Health Sciences, Busitema University, P.O. Box 236, Tororo, Uganda

    Adam Moyosore Afodun

  10. ParaMed Home Health Care, 250 Sidney Street, Belleville, ON, K8P 3Z3, Canada

    Ritah Kenganzi

  11. Infection Medicine, Edinburgh Medical School, Deanery of Biomedical Sciences, College of Medicine and Veterinary Medicine, The University of Edinburgh, EH8 9JZ, Edinburgh, Scotland, UK

    Fred Ssempijja

  12. School of Allied Health, St. Lawrence College, Kingston Campus, 100 Portsmouth Avenue, Kingston, ON, K7L 5A6, Canada

    Fred Ssempijja

Authors
  1. Eric Simidi Kegoye
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  2. Abdulfatai Olakunle Ojewale
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  3. Winnie Ezekiel
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  4. Ibe Michael Usman
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  5. Eric Osamudiamwen Aigbogun
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  6. Adesanya Olamide Adewale
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  7. Edgar Mario Fernandez
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  8. Keneth Iceland Kasozi
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  9. Halima Nalugo
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  10. Isaac Echoru
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  11. Adam Moyosore Afodun
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  12. Ritah Kenganzi
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  13. Okeniran Olatayo Segun
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  14. Fred Ssempijja
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Contributions

Eric Simidi Kegoye: conceptualization, Principal Investigator, methodology, data collection, validation, data analysis, and interpretation, writing—original draft preparation, and writing—review and editing. Abdulfatai Olakunle Ojewale: data collection, validation, writing—review and editing, and supervision of this study. Ibe Michael Usman and Edgar Mario Fernandez: methodology, validation, writing—review, and editing. Keneth Iceland Kasozi, Halima Nalugo, and Ritah Kenganzi: methodology, validation, data analysis and interpretation, and writing—review, and editing. Eric Osamudiamwen Aigbogun Jr: conceptualization, methodology, and writing—review and editing. Winnie Ezekiel, Adesanya Olamide Adewale, Isaac Echoru, Adam Moyosore Afodun, and Okeniran Olatayo Segun: data collection, validation, writing—review and editing. Fred Ssempijja: conceptualization, methodology, data collection, validation, data analysis, and interpretation, writing—original draft preparation, and writing—review and editing, and supervision of this study. All authors have read and agreed to publish the version of the manuscript.

Corresponding authors

Correspondence to Eric Simidi Kegoye or Fred Ssempijja.

Ethics declarations

Ethical approval and consent to participate

The study protocol was approved by the Research Ethics Committee of Kampala International University, Western Campus, Bushenyi, Uganda (study code: KIU-2021-28). The cadavers used in the study were from the institution (Kampala International University, Western Campus) and therefore did not necessitate documented consent for their donation. Permission to use the cadavers of our study was obtained from the Department of Anatomy, Kampala International University, Western Campus, Uganda. Consent to participate did not apply to this study since it involved cadaveric specimens.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

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Kegoye, E.S., Ojewale, A.O., Ezekiel, W. et al. Morphologic and morphometric bilateral analysis and sexual dimorphism in sciatic nerves of adult cadaveric specimens in Uganda. BMC Musculoskelet Disord 26, 422 (2025). https://doiorg.publicaciones.saludcastillayleon.es/10.1186/s12891-025-08641-9

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  • DOI: https://doiorg.publicaciones.saludcastillayleon.es/10.1186/s12891-025-08641-9

Keywords

BMC Musculoskeletal Disorders

ISSN: 1471-2474

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