Aberrant deep flexor muscles of the forearm associated with the accessory origin of first lumbrical muscle

To find out variations in the deep forearm flexors that are associated with anomalous origin of the first lumbrical muscle. Muscular anomalies of the upper extremity could cause peripheral nerve disorders. Although variations in the attachments of lumbrical muscles have been commonly studied, muscle with an additional origin in the proximal aspect of the forearm from the deep flexors is not much discussed. Fifty-three formalin-fixed upper limbs were dissected to assess the aberrant origin of the first lumbrical from the deep forearm flexors. The measurement, shape, origin, insertion and innervation of aberrant deep forearm flexors were noted and photographed. In two (3.77%) out of 53 upper limbs unilateral aberrant deep forearm flexors were found giving accessory anomalous origin to the first lumbrical muscle. In 11 cases (20.75%) the presence of accessory head of flexor pollicis longus was seen, and found co-existing with the aberrant deep forearm flexor in one (1.89%) limb. The clinical implication of these muscular anomalies, such as aberrant origins and hypertrophy of the first lumbrical, in nerve entrapments, especially in the aetiology of carpal tunnel syndrome, is considered. The awareness and identification of the muscular variations of the antebrachial and carpal regions will facilitate safe surgery of cases of median nerve entrapment syndromes.