Russel has observed that third lumbrical is inserted to tendon of third dorsal interosseus
This median to ulnar nerve shunt can be assumed in an ulnar palsy when there is paralysis of the hypothenar muscles in the presence of variable activity of the intrinsic muscles on the radial side of the hand, notably flexor pollicis brevis and the first dorsal interosseus.
Adductor pollicis, flexor pollicis brevis, and first dorsal interosseus are all, or for the most part, ulnar innervated.
Anterior tibialis, medial gastrocnemius, first dorsal interosseus
, biceps, and lumbar paraspinal muscles disclosed 1+ to 2+ fibrillations at rest.
The two basic impairments seen in the thumb in ulnar nerve palsy are a marked decrease in strength of the key pinch and in the pulp-to-pulp pinch (due to paralysis of adductor pollicis, first dorsal interosseus and flexor pollicis brevis).
They used the APL to substitute for the loss of the first dorsal interosseus.