Morphological Variations of the Lumbricals in Adult Cadaveric Hand: A Cross-sectional Study

ntroduction: The development of the human hand is unprecedented. Despite being tiny in size, the lumbricals play a far more significant role in the dynamic actions of the fingers. At the Metacarpophalangeal (MCP) and interphalangeal joints, they do flexion and extension. Lumbricals also exhibit some variations of developmental anomalies in attachments and morphology.

Aim: To classify morphological patterns of the lumbrical muscles and their anatomical variations in the hands and to discuss their clinical implications.

Materials and Methods: This cross-sectional study was conducted in the Department of Anatomy of Aarupadai Veedu Medical College and Hospital, Puducherry, India, from July 2020 to July 2021 on 50 disarticulated upper limbs during routine dissection of cadavers. In the present study, the limbs were labelled R or L for right or left, M or F for male or female. The variation in origin (including architecture), insertion (including split insertions, misplaced insertions, or absence of muscles, and the lengths of the muscle belly and tendon of all lumbricals were studied and noted. The dissection was carried out based on the steps as per Cunningham’s manual. Analysis of the data was done using Microsoft excel software 2016.

Results: In this study, 86% of the lumbricals were found normal in origin, innervation and insertion. Split insertion in the 3rd lumbrical was seen in 6% of the lumbricals, and a unipennate in the fourth lumbrical was seen in 2% of the total specimens. In 2% of the specimens, the 4th lumbrical was absent, the 1st lumbrical was hypertrophied in 2%, and the accessory belly in the 2nd lumbrical was also observed in 2%.

Conclusion: The findings of this research may provide light on the role of the lumbrical muscles in diagnostic and surgical procedures involving the hands.