Lesser Trochanter Morphometry: A Novel Morphological Classification System

Every orthopedic procedure requires the restoration of normal limb anatomy, function, and prevention of rotational malalignment. This can be predicted using indices on the lesser trochanter (LT), as it shows geographical and racial variations. No unified morphological classification system for LT exists in literature, and information on LT morphology in Nigerians is scanty. This study aimed to fill this gap and develop a morphological classification system with groups I, II, III, IV, and V representing oval, round, triangular, shield-like like and irregular LT shapes, respectively. Using 100 dry adult femurs, lesser trochanter height (LTH), lesser trochanter width (LTW), LT-Fovea distance (LT-F) and greater to lesser trochanter (GT-LT) distance were measured with digital vernier calipers. The LT shape and presence of retrotrochanteric groove were noted. The mean LTH, LTW, LT-F and GT-LT were 1.42 ± 0.32 cm, 2.15±0.39 cm, 7.2 ± 0.75 cm and 6.03 ± 0.76 cm, respectively. We observed a groove behind the LT in 85 femurs - shallow in 63 and deep in 22. The LT shapes observed were oval (54%), round (19%), triangular (5%), shield-like (21%) and irregular (1%). Following our novel classification system, class Ib was the most frequent (35%), followed by class IVb (16%), while others were absent. The various LT shapes reflect varying patterns, force and direction of pull exerted by ligaments in pre- and post-natal development, which depend on human occupational activities. Introduction of a unified morphological classification system provides a common standard for comparing the LT morphology in different populations.

Key Words: Lesser trochanter, femur, classification, morphometry