Good clinical results but persisting side-to-side differences in calf muscle strength after surgical treatment of chronic Achilles tendinosis: a 5-year follow-up.

We have prospectively studied calf muscle strength (isokinetic concentric and eccentric muscle strength at 90 degrees/s and 225 degrees/s of angular velocity in 24 patients (17 males and 7 females, mean age 43.0 years) surgically treated for chronic Achilles tendinosis (at the 2-6 cm level in the tendon). The mean follow-up time was 5 years (range 31-82 months). Surgery was followed by immobilization in a weight-bearing below the knee plaster cast for 2-6 weeks, followed by a stepwise increasing strength training programme. Strength measurements (peak torque) were done preoperatively, and 1 and 5 (mean) years postoperatively. Preoperatively, concentric plantar flexion peak torque at 90 degrees/s and 225 degrees/s and eccentric plantar flexion torque at 90 degrees/s were significantly lower (12.3%, 19.7% and 8.5% respectively) on the injured side compared to the non-injured side. Postoperatively, at the 5-year follow-up, 22 out of 24 patients (92%) were satisfied with the operation and active at their desired level (running, tennis, badminton, walking). There was no significant increase in concentric and eccentric calf muscle strength postoperatively. Concentric plantar flexion peak torque at 90 degrees/s and 225 degrees/s and eccentric plantar flexion peak torque at 90 degrees/s were still significantly lower (7.2%, 8.6% and 8.8% respectively) on the injured side compared to the non-injured side. In conclusion it seems that the calf muscle strength deficit seen on the injured side preoperatively in this group of patients remains despite 92% of the patients being pain-free and active in sports or at recreational level after the operation. However, the percentage side-to-side difference is relatively low, and might not have any clinical relevance.