Morphological Variations in Lumbricals of Hand – A Cadaveric Study

Abstract

The hand is a prehensile organ, it is endowed with grasping and precision movements for skilled work and it acts as a chief tactile apparatus. Thus human hand is a revolution in evolution. Indeed the lumbricals of the hand by producing flexion at the metacarpophalangeal joints and extension at the interphalangeal joints helps in writing, stitching and any other forms of precision work. A study was conducted in the department of Anatomy, Kasturba Medical College, Manipal with 30 cadavers of both sexes. The study was carried out to check for the variations in the origin, insertion, innervations and the extension of lumbrical muscle.93.3% of case showed the normal morphology of lumbricals and remaining showed the variations like bifid first lumbrical, bipennate 2 nd lumbrical, absence of 3 rd lumbrical, hypertrophied 1 st lumbrical. Anomalous and additional lumbrical muscle can cause carpal tunnel syndrome by compressing the median nerve. Hypertrophy of the lumbricals could compress the radial and ulnar arteries of the fingers, causing chronic sub ischemia. Hence present work is under taken to know the variations in the lumbricals.

Revisiting the Morphological Variations in Lumbricals of Hand

“…Similar finding was documented by Hosapatna M et al and Mutalik AM [Table 2]. [3,12] Among the variations of lumbricals studied, split insertion is the commonest variation reported. Split Insertion was commonly encountered in 3rd and 4th lumbricals.…”

“…Split insertion is an atavistic condition presenting as doubling of muscles as in lower animals (Virginian oppsum). [13] Hosapatna M (2013) [3] 30 1 (3.33%) Mutalik AM (2011) [12] 30 2 (6.67%) Present Study (2020) 74 2 (2.70%) [14] 107 -29 (27.1 %) 27 (25.2%) Mutalik AM(2011) [12] 30 8 (26.67%) -1 (3.3%) Hosapatna M (2013) [3] 30 1 (3.3%) --Parminder K (2013) [2] 50 - It was observed in our study that first lumbrical was found to be more bulky than other lumbricals in most of the specimens. However, clear hypertrophy was observed in only one specimen [Figure 9].…”

“…Such hypertrophy of first lumbrical can be attributed to overuse of thenar musculature as associated with fine movements involving thumbs and index finger. [3] Such variations of the lumbrical can present with wide range of clinical presentations like compression of neurovascular structures as in hypertrophy, carpal tunnel syndrome as in proximal origin and accessory belly of lumbrical.…”

“…[1] Variations in the lumbricals are common at the site of origin and insertion, architecture, accessory belly of first lumbrical and very rarely second lumbrical. [2][3][4] The lumbrical muscles are unique in their functions in being only intrinsic muscles which bridges between the palmar and dorsal surface (Link muscle). They act as flexors at MCP joint and extensor at inter-phalangeal (IP) joint.…”

Morphological Variations of Lumbrical Muscles of Hand in Sri Lankan Cadavers

“…This represents 5.1% of the total sample size which is somewhat closer to the percentages (3.3%) of that of the same variation reported by Mutalik [17]. A similar finding of 3.3% bipinate second lumbrical was reported from a couple of studies [18][19]. In contrast to this, another study reported quite a high percentage (45%) of second lumbrical bipinate nature [20].…”