Practice Essentials
Mannerfelt syndrome refers to rupture of the flexor pollicis longus (FPL) tendon from attrition caused by a bony spur in the carpal tunnel. Such ruptures were described by multiple authors from 1891 on. [1, 2, 3, 4, 5, 6] In 1969, Mannerfelt published his series of attrition flexor tendon ruptures in rheumatoid arthritis (RA) caused by bony spurs in the carpal tunnel. [7] The FPL tendon was the flexor tendon most commonly ruptured in this setting; consequently, this specific lesion was named after Mannerfelt.
Functional loss in Mannerfelt syndrome is variable. Even if the tendon has ruptured, continuity may exist through the peritendinous sheath or a pseudotendon. The patient presents with weak or no flexion of the distal phalanx. Flexor tendon ruptures occur consecutively, starting with the FPL tendon and thereafter affecting other flexor tendons in a more ulnar direction. [8] Bilateral ruptures have been reported. [9]
In his series of patients with affected flexor tendons in the carpal tunnel, Mannerfelt reported that 20 of 25 patients had involvement of the FPL tendon and that nearly all flexor tendon attritions occurred in women. [7]
Once a Mannerfelt lesion is identified, surgical treatment is always recommended.
Anatomy
The FPL originates from the middle of the anterior surface of the radial shaft, the adjoining part of the interosseous membrane, and the coronoid process. It is the most radial tendon in the carpal tunnel. The tendon passes under the transverse carpal ligament and around the hook of the distal scaphoid, and it inserts into the base of the distal phalanx of the thumb, flexing the distal phalanx.
The anterior interosseous branch of the median nerve supplies the FPL. The muscle receives its blood supply from radial artery muscle perforators. Within the tendon sheath of the thumb are two distinct vincula. Feeding vessels to the trapezium and scaphoid are present on the volar radial aspect of the trapezioscaphoid joint. These vessels course along the trapezioscaphoid ligaments to reach the scaphoid tuberosity.
Pathophysiology and Etiology
In RA, according to Mannerfelt, the intercarpal ligaments lose strength, and the carpal flexors exert a continuous pull, causing volar subluxation of the carpal bones. Destructive rheumatoid inflammatory tissue follows the feeding vessels, causing erosions at the distal volar scaphoid and the proximal volar trapezium. [10] Bony tissue between the erosions forms sharp spurs that cut through the weakened carpal tunnel floor and can lead to attrition of flexor tendons (see the image below).
Mannerfelt syndrome. Edges of ruptured flexor pollicis longus tendon can be seen. Bony spur is present at floor of carpal tunnel.
The FPL tendon is usually ruptured by a scaphoid spur. [11] The site of the rupture is usually the scaphoid, followed, in descending order of frequency, by the trapezium, distal ulna, hamate, lunate, distal radius, and ulnar sesamoid. [12, 13, 14, 15, 16, 17, 18, 19]
Prognosis
Schneider and Wiltshire treated 14 patients who underwent ring-finger flexor digitorum sublimis (FDS) transfer for the treatment of irreparable lesions of the FPL. Results, as measured by return of interphalangeal (IP) joint motion, were good in 12 patients and fair in one; failure occurred in one patient. [20]
Complications are minimal, though rupture of the tendon reconstruction or nonunion of an IP fusion can occur. Tenolysis may also be required. [21]
-
Mannerfelt syndrome. Patient is unable to flex interphalangeal joint of thumb after spontaneous rupture of flexor pollicis longus tendon.
-
Mannerfelt syndrome. Edges of ruptured flexor pollicis longus tendon can be seen. Bony spur is present at floor of carpal tunnel.
