Mechanical Effects of Immobilization on the Achilles’ Tendon

Matsumoto F, Trudel G, Uhthoff HK, Backman DS. Mechanical effects of immobilization on the Achilles’ tendon. Arch Phys Med Rehabil 2003;84:662-7. To measure the biomechanical effects of immobilization on the Achilles’ tendon. Experimental, controlled study. Physiatry research laboratory. Twenty adult rabbits. One hindlimb immobilized in a cast for 4 weeks (n=10) or 8 weeks (n=10). The contralateral legs (n=20) served as controls. Cross-sectional Achilles’ tendon area, mode of failure, mean failure load, and tendon stiffness. The Achilles’ tendon cross-sectional area did not change. Achilles’ tendon-calcaneus units failed at insertion at 4 weeks and in controls. Calcaneus fracture was the most prevalent mode of failure at 8 weeks. The mean load to failure of both immobilized groups (4wk: 187.5±45.7N; 8wk: 162.6±39.3N) was significantly smaller than that of the control group (549.2±93.7N, both P