The Importance of the Supratrochlear Foramen of the Humerus in Humans: An Anatomical Study

Background

The supratrochlear foramen (STF) is an important and relatively common anatomic variation in the lower end of the humerus in humans. The supratrochlear foramen (STF) of the humerus has been neglected in standard anatomy and orthopedics books. In recent years it has become clear that STF should be emphasized because anatomical knowledge of STF is useful for anatomists, anthropologists, orthopedic surgeons, and radiologists.

A thin plate of compact bone known as supratrochlear septum, which is lined by a synovial membrane, usually separates the olecranon fossa and coronoid fossa in the supratrochlear area of the distal part of the humerus [1–5]. This bony septum is opaque or translucent and septum in some cases may become perforated to form a foramen called as supratrochlear aperture, septal aperture, intercondylar foramen, or epitrochlear foramen, but is most commonly referred to as supratrochlear foramen (STF) [6–8]. The perforation lies between the lateral and the medial epicondyle [9]. The supratrochlear foramen was first described by Meckel in 1825 [3,10,11]. Although it may have different shapes, STF are mainly oval, round, triangular, sieve-like, and irregular [1,2]. Studies have shown that the humerus is not perforated in the embryonal stage [12]. The septum is present until 7 years of age, after which it is occasionally absorbed to form STF [13,14]. The supratrochlear foramen has, apart from its evolutionary significance, much clinical importance. The significance of the presence of coronoid-olecranon septal perforation was not clinically an atypical fracture pattern of distal humerus in teenaged boys [12,15]. It is of some clinical significance that it may predispose to low-energy fractures of the distal humerus [12]. The septal aperture is located along the narrow medullary humeral canal and extreme anterior angulation at the distal part of the humerus [3,16]. Studies have shown that the distal portion of the medullary canal in humeri with septal aperture was narrower and shorter at the entry point of a retrograde nail than in humeri without a septal aperture. Features of the intramedullary canal are important in the treatment of supracondylar fractures, especially following traumatic injuries and pathologic fractures and also in intramedullary nailing procedures [11,13,17–19]. Nayak et al. observed in plain radiographs that the SA was located closer to the medial epicondyle, resulting in difficult intramedullary nailing [14]. In the literature, the supratrochlear foramen of the humerus has been defined as coexistent with the supracondylar process in the same humerus [20]. Additionally, the SA is a relatively radiolucent area, commonly described as a “pseudo lesion” in an x-ray of the upper limb and can be mistaken as an osteolytic or cystic lesion [14,21,22]. The osteochondritis dissecans of the septum supratrochlear is the result of an incomplete resolution of the septum in the development of the elbow joint [23]. Various theories regarding the formation of this variation have been suggested. It remains unclear as to what degree the various factors contribute to the formation of the aperture.

Material and Methods

The goal of this study was to describe supratrochlear foramen of the humerus in the Turkish population. There are few studies about it in the Turkish population. A total of 166 dried humeri (83 right side and 83 left side), of which 78 belong to males and 88 to females, were examined to determine the presence of supratrochlear foramen in the Turkish population. The study protocol was approved by the ethics committee of our institution. All measurements were only made on adult bones. These bones were obtained from the Department of Anatomy, Faculty of Medicine and Department of Antrophology, University of Mustafa Kemal, Hatay, Turkey. They were free from any patholgical changes and fractures. STF were morphologically and morphometrically analysed. An osteometric board was used to measure the epicondylar breadth (EB) for the sex determination of the humerus. Digital vernier calipers were used to measure the transverse (width) diameter (TD) and vertical (height) diameter (VD) of the STF, the distance of the medial epicondyle to the medial aspect of the STF (MB), and that of the lateral epicondyle to the lateral border of the STF (LB). The shape of the STF was also imaged. In bones where the foramen was not present, opacity and translucency of the supratrochlear septum were noted with the help of transmitted light from posterior to anterior. All measurements are expressed in millimeters. By using these measurements, we calculated minimum, maximum, mean, and standard deviation. SPSS 20.0 version was used for statistical analysis.

Results

The supratrochlear foramen was studied in 166 unpaired Turkish humeri with sex and side known. Measurements were only made on adult bones. The supratrochlear foramen was seen in a total of 18 bones (10.8%). STF was observed in 4 (4.8%) cases on the right side and 14 (16.9%) on the left side. In males, it was seen in 16.7% of cases on the left side and 2.1% of cases on the right side. In females, STF was present on the left side in 17.0% of humeri and 8.6% on the right side (Table 1, Figure 1). In this study, we found most STF were on the left side of both sexes.

In the current study, the vertical diameter for supratrochlear foramen was 4.12±0.98 mm (range 2.7–4.9 mm) on the right side and 4.04±0.9 mm (range 2.1–5.1 mm) on the left side. Transverse diameter was 5.63±0.97 mm (range 4.3–6.5 mm) on the right side and 6.01±1.86 mm (range 2.7–8.9 mm) on the left side.

In males, the vertical diameter (VD) was 2.72±0.0 mm (range 2.7–2.7 mm) on the right side and 4.26±0.0 mm (range 2.9–5.1 mm) on the left side. Transverse diameter (TD) was 6.52±0.0 mm (range 6.7–6.7 mm) on the right side and 6.7±2.2 mm (range 4.1–8.9 mm) on the left side. In females, the vertical diameter was 4.59±0.36 mm (range 4.2–4.9 mm) on the right side and 3.92±0.93 mm (range 2.1–5 mm) on the left side. The transverse diameter (TD) was 5.34±0.95 mm (range 4.3–6.2 mm) on the right side and 5.64±1.66 mm (range 2.7–7.9 mm) on the left side (Table 2).

The mean distance from medial epicondyle to medial edge of the STF (MB) was 26.1±3.33 mm (range 22.6–30.5 mm) on the right and 25.73±3.37 mm (range 18.9–30.7 mm) on the left side. The mean distance from lateral epicondyle to lateral border of the STF (LB) was 27.3±1.54 mm (range 25.8–29.5 mm) on the right and 27.5±1.5 mm (range 24.9–30.1 mm) on the left side. We observed the position of the STF to be located nearer to the medial epicondyle (Table 2).

The epicondylar breadth (EB) was 60±4.36 mm (range 50.7–69.1 mm) on the right and 58.1±4.07 mm (range 49.7–68 mm) on the left side. The epicondylar breadth was significantly larger in males (62.7±2.46 mm) than in females (55.8 mm±2.75) (Table 2)].

The STF was oval, round, triangular, and sieve-like in shape in 13 (7.8%), 2 (1.2%), 2 (1.2%), and 1 (0.6%), respectively, and the oval shape was common on the left side and in females (Table 3).

Translucent septum was found in 34 (20.5%) humeri and opaque septum was seen in 114 (68.7%) humeri. Translucent septum was found in 17 (20.5%) on both sides of the humeri and was very similar in both sexes (Table 1, Figure 2.)

Discussion

The SA is a foramen of the bony septum that separates the olecranon from the coronoid fossae at the distal end of the humerus [24–26]. The supratrochlear foramen (septal aperture) was first described by Meckel in 1825 [27]. The supratrochlear foramen is of great interest to anthropologists, who claim it as important in establishing relationships between humans and lower animals [24], including cattle, rats, dogs, hyenas, and other primates [18,27,28]. According to Hrdlicka, the perforation is very frequent in primates other than man [29]. Lamb observed that the formation of the STF was more common in ancient peoples and occurs more frequently on the left side and in adolescents, as well as in mature individuals [30]. The supratrochlear foramen has, apart from its evolutionary significance, much clinical and surgical importance [18].

There is a wide variation in the rate of the STF occurrence in various human populations. Its incidence varies from close to 0% to almost 60% among different human populations globally [3]. Studies on STF in different populations showed an incidence of 58% in Arkansas Indians [29], 21.7% of African Negroes, 32.5% of South Africans [8], 47% in Tellem [31], 4.3% in White Americans [32], 18.4% in American Negroes [32], 18.1% in Japanese [16], 17.5% in Chinese [33], 6.9% in Americans [6], and 43.6% in Egyptians [1]. Incidence in European populations was 0.304% in Greeks [22], 6.1% in Netherlands [32], 9.4% in Italians [35]. Incidence in Indian populations showed 27.4% in Eastern Indians [13], 32% in Central Indians [24], 27.56% in North Indians [5], 28% in South Indians [1] and 34.4% in overall Indians [24] (Table 4).

The few previous studies in Turkey reported incidence at 7.9% [26], 8.6% [17], and 12% [17]. We found this ratio was 10.8%, which is similar to the previous Turkish reports (Table 4). Prevalence of septal aperture has been reported to be higher in Indians and Africans than in Europeans and Turks (Table 4).

The frequency of supratrochlear foramen in our study was higher in females and more common on the left side (Table 1). This finding was similar to previous reports [3,5,6,8,17,31,32]. In contrast, Blakely et al. reported that incidence of STF was higher on the left side and in males [10].

In the present study, the prevalence of STF was higher on the left side than the right side (Table 1). Our results also support earlier reports [2,11,14,15,26,27,34,35]. Conversely, Nayak et al. found the presence of STF in 44.5% of cases on the right side [14]. Singhal and Rao found the incidence on both sides was very similar: 27.9% of the right and 27.8% of the left humeri [27].

A number of studies have reported that humeral septal aperture was associated with supracondylar process and there are reports of a greater incidence in males [20,31]. In our study, we did not find septal aperture associated with supracondylar process.

The shape of STF was predominantly oval and it was more common on the left side, similar to previous reports [2,3,9,15,25] (Table 3).

Translucent septum was found in 17 (20.5%) on both sides of the humeri in the Turkish population (Table 1). Bhanu et al. found the translucency in 69 (82.14%) humeri and chiefly on the left side [2]. Krishnamurthy et al. reported an incidence of 66.6%, mostly on the left side [15]. Vasantbhai observed the translucency of septum in 126 (55.8%) on the right side [36] and Veerappan et al. reported 50% [11]. Conversely, according to many authors, incidence of translucency of the septum and STF was higher on the right side [1].

In the present study, the vertical diameter of the supratrochlear foramen was 4.12±0.98 mm on the right side and 4.04±0.9 mm on the left side, and the transverse diameter was 5.63±0.97 mm on the right side and 6.01±1.86 mm on the left side (Table 2). Table 5 contains comparative statistical data of supratrochlear foramen of humerus in various studies.

In our study we observed that the mean transverse diameter of the STF on the left side is larger than on the right side. This finding was similar to previous reports of Ozturk et al. [26].

In our study, the epicondylar breadth was significantly larger in males (62.7±2.46 mm) than in females (55.8±2.75 mm). Ndou et al. reported a mean 56.1±5.5 mm, significantly larger in males (60.5 mm) than in females (53.4 mm) [8]. The mean distance from medial epicondyle to medial edge of the STF (MB) was 26.1±3.33 mm on the right side and 25.73±3.37 mm on the left side, thus the position of STF is located near to the medial epicondyle, especially on the left side. Nayak et al. found 28 mm on the right and 26.1mm on the left side [14], which agrees with Veereppan et al. [11]. The mean distance from lateral epicondyle to lateral border of the STF (LB) was 27.3±1.54 mm on the right and 27.5±1.5 mm on the left side. Ndou et al. found 26.3±2.9 mm between the STF and the tip of the lateral epicondyle [8].

Some of the mechanisms explaining the cause of STF in the humerus are:

Clinical importance:

Conclusions

The present study showed 10.8% STF incidence in the Turkish population, with the left side predominant. Prevalence of septal aperture has been reported to be higher in India and in Africa than in Europeans and Turks (Table 5). We believe that this study will contribute to the literature; anatomical knowledge of STF is beneficial for anatomists, anthropologists, forensic practice, orthopedic surgeons, and radiologists.