Bilateral congenital absence of flexor pollicis longus with thumb hypoplasia and thenar atrophy

Abstract

Congenital absence of flexor pollicis longus with or without associated anomalies of thenar muscles and thumb is of rare occurrence. Inability to flex the interphalangeal joint of the thumb and absent dorsal wrinkles and flexion creases of the thumb are important clues to the diagnosis. Routine radiography and cross-sectional imaging help to confirm and document the condition. This article presents an extremely rare case of bilateral congenital absence of flexor pollicis longus tendon with thumb hypoplasia and thenar atrophy.

Congenital Bilateral Anomaly of the Flexor Pollicis Longus Tendon Without Thenar Atrophy: A Case Report

“…It is bilateral absence of the FPL tendon without any anomaly or atrophy that is even more unique. 1,9,11 During embryological development, there are identical developmental stages for both the upper and lower limbs. As our bones form and the limbs elongate, myoblasts aggregate and form a large muscle mass in each limb.…”

“…Thumb hypoplasia can be classified into 5 categories: isolated minor hypoplasia (type 1), associated with thenar hypoplasia and metacarpophalangeal (MCP) joint instability (type 2), musculotendinous/osseous deficiency with absent active motion at MCP or the interphalangeal joint (type 3), floating thumb (type 4), and complete absence of the thumb (type 5). 9 Other possible characteristic appearances, also in case of bilateral absence of the FPL tendon, include the absence of the dorsal wrinkles on the thumb and the flexion crease, and the inability to palpate the FPL tendon in the flexor crease of the thumb. Finally, and most importantly, there is a loss of active flexion at the distal interphalangeal joint.…”

“…However, some connections and anomalies are difficult to visualize at imaging and should be proven by surgical exploration. 1,4,9,11 The treatment with a tendon transfer by using the tendon of the FDS muscle of the ring finger is an option. In this case, postoperative planned physiotherapy is strongly advised.…”

“…Only a few cases have been reported, 1 of them with a familial appearance, other associated with more anomalies or thenar atrophy. [6][7][8][9] Here, we present the rare case of a 23-year-old woman with congenital absence of both FPL tendons without any associated anomalies or thenar atrophy.…”

Flexor pollicis longus (FPL) tendon hypoplasia: A case report and literature review

“…The flexor pollicus longus (FPL) muscle acts to flex the thumb at the interphalangeal joint and is innervated by the anterior interosseous nerve. Impaired function of the FPL can be caused by FPL tendon rupture, anterior interosseous nerve palsy, and congenital anomalies of the FPL [1], [3].…”