Evaluation of the role of unconjugated hyaluronic acid repetitive injection during the primary repair of flexor tendons in no man’s land: a randomized control trial

Background Zone 2 flexor tendon injuries are prone to poor results following repair due to adhesions. Different repair methods and physiotherapy protocols have been devised to improve outcomes, with variable results. Hyaluronic acid (HA) is a polysaccharide produced by the innermost layer of the tendon sheath that facilitates gliding in zones where the sheath is continuous. Methods Sixty-two flexor tendons that were repaired using a double-stranded core suture were divided between groups A ( n = 32 ) and B ( n = 30 ). In the former, non-cross-linked HA was repeatedly instilled at the repair site, with a total of three injections per digit. The repair outcomes were assessed using the Strickland criteria, the ratio of total active motion to total passive motion (TAM/TPM), and active range of motion (AROM) for individual joints. Results A total of 31.1% of group A patients had excellent to good outcomes in contrast to 13.3% in group B. The mean difference in TAM was 105° in group A and 71° in group B ( p value ˂ 0.05). The mean TAM/TPM was 0.65 in group A and 0.56 in group B ( p value = 0.06). Conclusions HA significantly improves the results of flexor tendon repair in zone 2. Level of Evidence: I.