A Study of the Supratrochlear Foramen of the Humerus: Anatomical and Clinical Perspective.

Introduction: The Supratrochlear Foramen (STF) is a variably shaped perforation present in the bony septum that separates the olecranon and coronoid fossae at the distal end of the humerus, between the two epicondyles. Its incidence varies widely from 0.3% to 58% in different races.

Aim: This study aims to describe its prevalence and morphometry in relation to its shape and size and distance from the epicondyles.

Materials And Methods: A prospective study of 244 unpaired humerii, 130 of the left side and 114 of the right side of unknown age and sex were examined for the presence of STF and prevalence stated. The STF was classified according to shape and their metric assessment was carried out, along with measures of its distance from the epicodyles and trochlear margin.

Results: Of the 244 humeri studied 60 showed presence of the foramen, 45 were opaque and 139 showed translucent septum. The sidewise prevalence of opacity, translucent septum and foraminae were tabulated. The commonest shape noted was oval. Other shapes such as round, triangular, rectangular, sieve and reniform were visualised. In the oval STF, transverse and vertical diameters were measured. The transverse and vertical diameters on the left were 4.9 and 3.27 mm and on the right it was 5.12 and 3.48mm respectively. The distance from the medial epicondyle, lateral epicondyle and trochlea to the STF margins was measured and the mean values were calculated separately for right and left sides. The mean diameter of the round foramen was 3.23 and 4.89mm for left and right sides respectively. In the triangular type the maximum vertical and transverse diameters were recorded. There was only one sample of the rectangular type. Its length was 4.1mm and the breadth was 2.27mm and it belonged to the right side. The reniform type totalled 7 of which 6 were of the left side. The average vertical length at the hilum was 4.52 mm and the transverse measurement was 7.44 mm. The foraminae of the right side were found to be larger, regardless of shape.

Conclusion: Its existence is important to the orthopaedician in the preoperative planning of nailing fractures of the distal humerus and to the radiologist for differentiating it from an osteolytic or cystic lesion.