[Operative treatment of claw deformity by lassoplasty]

The aim is correction of claw deformity of the fingers by intrinsic paralysis.

Indications are claw deformity of fingers caused by palsy or functional loss of the interosseus or lumbrical muscles as far as the function of the superficial and deep flexors of the finger is intact.

Contraindications are loss or paralysis of finger flexors supplied by the median nerve, fixed extension or flexion contracture of the finger joints, osteoarthritis and other malfunctions of the finger joints, no active flexion and extension of the interphalangeal joints due to compromised tendon gliding. Relative: Upper ulnar nerve palsy with functional loss of the deep flexor of the small and ring finger and possibly of the middle finger.

The operation technique involves detachment of the flexor digitorum superficialis IV tendon (FDS IV) distal to Camper's chiasm, division of the tendon into separate strips, interweaving of each tendon strip into the proximal part of the A2 pulley of the affected fingers. In cases of claw deformity of all fingers it may be advantageous to apply the superficial flexor tendon of the long finger in addition to the FDS IV tendon as otherwise the FDS IV tendon has to be divided into four strips resulting in relatively thin tendon strips. If the FDS III and IV tendons are applied, the two strips of the FDS IV tendon are used for lassoplasty of the small and ring fingers and the FDS III tendon for lassoplasty of the middle and index fingers.

Postoperative management includes immobilization of the operated fingers by a dorsoulnar forearm plaster cast including the metacarpophalangeal joints which are flexed to 70°. After 2 weeks replacement of the cast by a thermoplastic splint for another 4 weeks. During the whole period exercises for the finger and thumb should be carried out.

From April 2003 to June 2012 a total of 17 patients, 8 female and 9 male were surgically treated for claw deformity. The dominant hand was affected in seven patients. The average age was 46 ± 15 (22-80) years, the average interval from onset of ulnar palsy to lassoplasty was 61 ± 91 (3-288) months. The final follow-up was performed after an average of 42 ± 32 (2-112) months. Claw deformity was resolved in 14 out of the 17 patients. The grip strength was on average 58 ± 28 % (11-96 %) of the unaffected hand, the mean disabilities of the arm, shoulder and hand (DASH) score was 32 ± 18 (5-68) points and the degree of patient satisfaction 7 ± 2 (0-10). According to own results and those in the literature lassoplasty can be recommended for the treatment of claw deformity.