Morphological Variation in Lumbricals of Hand

Abstract

Background: The lumbrical muscles of the hand are unique intrinsic muscles responsible for coordinated finger movements and fine motor functions. Variations in their morphology, origin, insertion, and innervation may influence hand biomechanics and surgical outcomes.
Aim: To analyze the morphological variations of lumbrical muscles of the hand in terms of number, origin, insertion, and morphometry.
Materials and Methods: This cross-sectional cadaveric observational study was conducted in the Department of Anatomy, Jawaharlal Nehru Medical College, Bhagalpur, from 2023–2026. Forty hands obtained from 20 formalin-fixed adult cadavers were dissected. Morphological parameters including number of lumbricals, origin, insertion, muscle belly length, tendon length, and variations were documented. Measurements were taken using digital Vernier calipers. Statistical analysis was performed using Microsoft Excel and descriptive statistics.
Results: All four lumbricals were present in 80% of hands, while 12.5% showed only three lumbricals and 7.5% demonstrated supernumerary lumbricals. The first and second lumbricals were predominantly unipennate, whereas the third and fourth lumbricals were mainly bipennate. Accessory insertions and bifid insertions were observed in a few specimens. The mean muscle belly lengths of the first, second, third, and fourth lumbricals were 3.5 ± 0.5 cm, 3.3 ± 0.6 cm, 3.0 ± 0.5 cm, and 2.8 ± 0.5 cm respectively.
Conclusion: Considerable morphological variations exist in the lumbrical muscles of the hand. Awareness of these variations is important for anatomists, hand surgeons, and clinicians during surgical procedures, diagnosis of entrapment neuropathies, and rehabilitation.