Chemoprotection of flexor tendon repairs using botulinum toxin

After flexor tendon repair, tendon gapping or rupture may be replaced by joint stiffness and poor function. After surgical repair of injured flexor tendons, botulinum toxin type A was injected into the forearm flexor muscles. This selectively decreased the force of muscle contraction. During this period of partial muscle denervation, patients could generate enough force to allow for early active mobilization (with its attendant benefits) but insufficient force to induce gapping or rupture of the repaired tendon.

Eighteen adult patients with zone 2 flexor tendon injuries (34 digits) were studied prospectively for up to 3 years. Tendons were repaired using the modified Kessler technique and marked with stainless steel wire. Botulinum toxin was injected into the appropriate proximal flexor muscle belly under localizing electromyographic control. A matched cohort consisted of 53 patients (104 digits).

Results were assessed according to range of joint motion (Kleinert and Verdan criteria) and electromyographic and radiologic studies. Ninety-four percent had excellent results and 6 percent of digits had good results. There were no patients with fair or poor results. Average active range of motion was 244 degrees at 18 months. No gapping or ruptures occurred and no tenolyses were required. The control group of matched controls (modified Kessler repair; no botulinum injection) showed that 81 percent of digits had excellent results, 6 percent had good results, 8 percent had fair results, and 6 percent had poor results.

Botulinum toxin injection statistically significantly improves the results of flexor tendon repair. The authors have termed this technique "chemoprotection" of flexor tendon repairs.