Gliding resistance versus work of flexion--two methods to assess flexor tendon repair

Two methods for measuring the ability of the flexor tendon to glide following repair are commonly cited in the literature; gliding resistance (GR) at the tendon-pulley interface and work of flexion. The GR measures the friction force at the tendon-pulley interface, while the work of flexion characterizes whole finger function during flexion. Since a portion of the total work of flexion (TWOF), termed the internal work of flexion (IWOF), is expended due to the tendon-pulley interaction, a relationship between the work of flexion and GR should be present. The purpose of this study was to quantify this correlation. Forty-eight flexor digitorum profundus tendons in 48 mongrel dogs were transected and repaired with a modified Kessler technique and an epitenon running suture. Post-operatively, the operated paw was immobilized in a cast. Dogs were sacrificed at 1, 3, 5 or 7 days after surgery. In each repaired digit work of flexion and GR were measured. While the GR was not significantly different over the time points, the TWOF decreased at 5 days after surgery and then increased at 7 days (p<0.05). There was little correlation between TWOF and GR (r=0.25, p=0.07). However, there was a strong correlation between IWOF and GR (r=0.76, p<0.05) suggesting that measurement of GR could be used as a predictor of IWOF within the short term after tendon repair.