Hypotrophy of the soleus muscle in man after achilles tendon rupture. Discussion of findings obtained by computed tomography and morphologic studies.

Seven athletes (age range, 35 to 43 years), who sustained total subcutaneous ruptures of the Achilles tendon 2 to 5 cm above its distal insertion, were treated surgically with suturing of the tendon, immobilization of the leg and foot for 6 weeks, and cast changes so as to increase the dorsiflexion of the foot. Needle biopsies were obtained several times from the soleus muscles of both the injured and uninjured legs at a depth of about 5 cm. The cross-sectional area was measured by computed tomography at the same level the tissue was obtained by biopsy. Results of morphologic studies revealed a selective Type I fiber atrophy of the soleus muscle. Computed tomography revealed a 23% decrease in the area of the calf muscles and a 11% total reduction in the cross-sectional area of the calf (about the middle, where the gastrocnemius muscle is transformed into a tendon and where the soleus lies superficially). Mere measurement of the circumference of the calf is judged to be a poor criterion of muscle atrophy when compared with these other means of evaluation of atrophy. The evidence compiled during this study suggests that prompt surgical treatment of Achilles tendon ruptures, with cast changes several times during the period of immobilization and with tension maintained on the muscle, is the most effective treatment regimen we have found for this injury.