Effect of hyaluronic acid on rabbit profundus flexor tendon healing in vitro.

We performed an in-depth biomechanical evaluation of the effect of hyaluronic acid (HA) on the healing of rabbit profundus tendons cultured in vitro. Seventy-eight flexor tendons from 13 rabbits were transected and reapproximated at their Zone II midpoints. Tendons were divided into left and right forepaw groups. Each tendon from the left forepaw group was incubated in one of four possible culture media: control (no HA), low (0.1 mg/ml), medium (0.5 mg/ml), or high (1.0 mg/ml) HA media. HA was added on the first day of incubation. Each tendon from the right forepaw group was cultured in low, medium, or high concentrations of HA, but HA was added after 1 week of incubation in control media. All tendons were cultured for 8 weeks, after which time tenorrhaphies were disrupted and the following biomechanical parameters were determined: apparent maximum stress, apparent strain at apparent maximum stress, normalized energy absorption, and tangent modulus before failure. Comparisons using these parameters showed no statistically significant differences among the various tendon groups. We believe this is the first study of its kind to show no effect of hyaluronic acid on the functional strength of tendon after healing in vitro.