Narayana Medical Journal Vol 1: Issue 2. Anatomical note of supratrochlear foramen of humerus in south costal population

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1 Narayana Medical Journal Vol 1: Issue 2 Original Article: Anatomical note of supratrochlear foramen of humerus in south costal population of Andhra Pradesh P. Sharmila Bhanu, K. Devi Sankar Published online: Oct 2012 Abstract Background: Supratrochlear foramen (STF) in adult humerus is formed by perforation of thin bony septum present between olecranon fossa and coronoid fossa, which is found proximal to trochlea of humerus. Presence of this foramen is clinically important during preoperative planning for intramedullary nailing in the treatment of supracondylar fractures of distal humerus. Methods: The study was conducted on 121 dry Results: STF was seen in 13 right sided humeri (26.53%) and in 24 left sided humeri (33.33%). The mean vertical and transverse diameter of right side was 5.75±1.5 and 6.68±0.8 mm and on the left side the mean vertical and transverse diameter was 4.86±1.2 and 6.92±2.0 mm. Both right and left sided humerus showed predominantly oval shaped STF (70.27%). Translucent of septum was found in 69 (82.14%) humeri and it was chiefly seen on the left side. adult humeri (49 right and 72 left) irrespective of sex were used to find the STF. The bones Discussion and conclusion: The results of the containing the foramen were measured and the shapes have been noted. P. Sharmila Bhanu, K. Devi Sankar Assistant Professors of Anatomy, Narayana Medical College, Chinthareddy Palem, Nellore, Andhra Pradesh, India E mail: sharmilabp78@gmail.com present study showed that STF is more common on left side, with the oval shape being more common. The sides did not exhibit any statistical significance. The anatomical knowledge of STF may be beneficial for anthropologists, orthopedic surgeons and

2 radiologists in day-to-day clinical practice. Key Words: Humerus, supratrochlear foramen, coronoidolecranon septum Introduction: In the distal end of humerus, the coronoid fossa in front and the olecranon fossa behind is separated by a thin lamina of bone, the coronoidolecranon septum (COS). This thin plate of bone sometimes become transparent or perforated in some cases and give rise to a foramen called septal aperture or commonly known as supratrochlear foramen (STF). Early findings of Morton in 1945 [1] revealed that this thin plate is always present until the age of seven years after which it becomes absorbed to form STF. According to the literature, the first finding of STF was reported by Meckel in 1825 [2], since then it was described in various animals like dogs, hyenas, cattle, and other primates [3,4]. for stable configuration [7] because of the chances of formation of STF [8]. In addition, for any radiological investigation of humerus a sound anatomical knowledge is essential to evade any faulty interpretations of X-rays. Hence prior knowledge of STF is necessary which may be beneficial for anthropologists, orthopedic surgeons and radiologist. The objective of this study was to examine the incidence and morphological features of STF in south costal population of Andhra Pradesh. Material and Methods: A total of 121 (49 right sided and 72 left sided) adult human dried humerus of unknown sex were obtained from the bone bank of the department of Anatomy, Narayana medical college, Nellore, Andhra Pradesh, India. The bones were selected free of pathological changes. The incidence of STF was found on the right and left side. The apertures which were having the regular margins Because of this STF, the person may be able to were considered. The Vernier caliper with overextend the elbow joint [5]. Nowadays the intramedullary fixation of distal humerus has been increased following traumatic injuries and pathological fractures [6]. As the supracondylar fractures are common in pediatric minimum scale of 0.01millimeter (mm) was used to measure the maximum transverse and vertical diameters of STF (Fig. 1). In addition to the presence of foramen, shape and translucency of coronoid-olecranon septum (COS) also noted age group, it requires proper pinning technique

3 with the help of transmitted light from posterior to anterior. Results: Out of 121 adult dry humerus of unknown sex, overall STF was found in 37 humeri (30.58%) with the incidence of 13 (26.53%) on right side and 24 (33.33%) on left side. The vertical and transverse diameter of STF on right side was 5.75±1.5 and 6.68±0.8 mm respectively with the P less than Similarly the vertical and transverse diameter of STF on left side was The values of vertical and transverse diameter was expressed in mean±sd; mm-millimeters Table 2. Incidence of translucent and opaque septum in remaining 84 adult dry humeri 4.86±1.2 and 6.92±2.0 mm respectively with P less than (Table 1). The shape of STF was predominantly oval with the incidence of 26 (70.27%) than the round with the incidence of 11 (29.73%) and the oval shape was common on left side (Table 1). Total of remaining 84 humeri irrespective of side showed translucency of COS was found in 69 (82.14%) humerus and the remaining 15 (17.86%) was opaque in nature. The translucency of COS was seen more on left than the right side humerus (Table 2). Only one of the right humeri showed the presence of both STF and translucency (Fig. 2). Table 1. Incidence of parameters of STF in 37 adult dry humeri Discussion The incidence of STF has been considered as an atavistic character as it is more commonly found in the primates. The frequency of its presence or absence in human populations varies and is racial dependent and it was found to be from 6% to 60% [9]. Studies on STF in worldwide populations showed an incidence of 4.2% in White Americans [10], 18.1 in Japanese [11], 6.9% in Americans [12], 7.9% in Egyptians [9], 8.6% in Turkish populations [13] and 32.5% in

4 South Africans [14]. Incidence in Indian populations showed 27.4% in Eastern Indians [15], 32% in central Indians [16], 27.5% in North Indians [17], 28% in South Indians [4] and 34.4% in overall Indians [18]. Figure 1. Photograph showing the measurements of STF and translucent of COS (asterisk). VD vertical diameter; TD transverse diameter occurrence was 26.53% and left was 33.33% and most of the foramina were oval in shape. Transverse diameters of both right and left sides were found to be more than the vertical diameter which is in more accordance with the similar study by Nayak et al [18]. Translucency of the COS was noted to be more on the left side with 82.35% which is similar to the previous findings. Our study reveals the predominance of left side STF and translucency of the COS. A number of studies have been suggested that STF may be a hereditary phylogenetic trait associated with evolutionary significance [19]. According to Lamb [20, 21], the STF may be due Figure 2. Photograph showing the oval type of STF. Dotted circle indicating the partial translucent of COS. L left; R right. impact pressure in cases of hyper-flexion or hyper-extension at elbow joint leading to resorption of the COS at a point where the coronoid process or olecranon process of the ulna would potentially make contact. This explains why the foramen is common in dogs, hyena and other primates because of the postures used by animals while tearing morsels of food. But the presence of foramen in humans who do In the present study the overall incidence of STF was found to be 30.58% which can be considered as slightly higher prevalence. The right side not assume such posture is debatable. If mechanical stress is the causative agent, then it should be more on right side. In contrast it is

5 more common on left side. It can be explained that it is a phylogenetic characteristic feature frequently found in primates and is suppressed by the stronger limb and exhibited in the weaker limb (12). Another cause of occurrence of STF may be osteoporosis or degenerative joint diseases like osteoarthritis or rheumatoid arthritis. But a more solid hypothesis suggests that septal apertures are purely mechanically induced and it is acquired. Supracondylar fractures account for 75% of all injuries in the pediatric age group. Lot of controversies prevails about the route of pin entry while treating these fractures. The presence of STF in cases of these fractures makes it more difficult to plan out the preoperative procedures because of the narrow medullary canal. The foramen represents an area of relatively radiolucent commonly encountered as a type of pseudolesion in the radiology of upper limb. Conclusion The present study showed 30.58% of STF incidence in the south Andhra population with the left side predominance. Precise anatomical knowledge of STF may be beneficial for anthropologists, orthopedic surgeons and radiologists during their clinical diagnosis and surgical procedures. References 1. Morton SH, Crysler WE (1945) Osteochondritis dissecans of the supratrochlear septum. J Bone Joint Surg, 27: Meckel JH (1825) cited in, Kate, BR, Dubey, PN (1970) A note on the septal apertures in the humerus of Central Indians. Eastern Anthropologist, 33: Haziroglu RM, Ozer M (1990) A supratrochlear foramen in the humerus of cattle. Anat Histol Embryol, 19: Singhal S, Rao V (2007) Supratrochlear foramen of the humerus. Anat Sci Int, 82: De Wilde V, De Maeseneer M, Lenchik L, et al (2004) Normal osseous variants presenting as cystic or lucent areas on radiography and CT imaging: a pictorial overview. Eur J Radiol, 51: Akpinar F, Aydinlioglu A, Tosun N, et al (2003) A morphometric study on the

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