Morphometric analysis of Lumbricals in the Hand with Proximal origin of First and Second Lumbricals

Background: Lumbrical muscles, though small, play a significant role in precise digit movements. Variations in attachment and size are common, and proximal origin has been implicated in carpal tunnel syndrome. The aim and objective is to measure muscle belly length, width, thickness, and tendon length of the four lumbricals in cadaveric hands, and assess differences between right and left hands, and between male and female cadavers. Settings and Design is Cross-sectional study. Material and Methods: This descriptive cadaveric study examined 80 hand specimens (40 right, 40 left, paired by cadaver) from 40 embalmed cadavers (33 male, 7 female). Lumbrical morphometry was measured using a Vernier calliper. Statistical Analysis is right-left comparison used a paired-samples t-test matched by cadaver; sex comparison used an independent-samples t-test at cadaver level. Hands with absent or rudimentary third or fourth lumbricals were excluded from that analysis. Results: Tendon length of the first lumbrical was significantly longer in the right hand (2.62±0.98 cm) than the left (2.40±0.88 cm; P=0.009). No other dimension differed significantly between sides or sexes, though the sex comparison was limited by the small female sample (n=7). Proximal origin of the first lumbrical with hypertrophy was found in one hand (1.25%); proximal origin of a bipennate second lumbrical was found in another (1.25%). Conclusion: Tendon length of the first lumbrical differs significantly between right and left hands of the same individual. Proximal origin of the first and second lumbricals, with hypertrophy, was also noted, with potential to compress the median nerve and predispose to carpal tunnel syndrome.

Keywords: Lumbricals, flexor digitorum profundus, proximal origin, morphometry.