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Arch Phys Med Rehabil. 2003 May;84(5):662-7.

Mechanical effects of immobilization on the Achilles' tendon.

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1
Bone and Joint Laboratory, University of Ottawa, Ottawa, ON, Canada.

Abstract

OBJECTIVE:

To measure the biomechanical effects of immobilization on the Achilles' tendon.

DESIGN:

Experimental, controlled study.

SETTING:

Physiatry research laboratory.

ANIMALS:

Twenty adult rabbits.

INTERVENTION:

One hindlimb immobilized in a cast for 4 weeks (n=10) or 8 weeks (n=10). The contralateral legs (n=20) served as controls.

MAIN OUTCOME MEASURES:

Cross-sectional Achilles' tendon area, mode of failure, mean failure load, and tendon stiffness.

RESULTS:

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<.005). The mean tendon stiffness of both immobilized groups (4wk: 64.6+/-24.8N/mm; 8wk: 53.9+/-19.9N/mm) was significantly lower than that of the control group (125.1+/-26.5N/mm, both P<.005).

CONCLUSIONS:

Immobility for up to 8 weeks caused decreased stiffness but no atrophy or rupture of the Achilles' tendon, suggesting that immobility does not constitute a risk factor for Achilles' tendon midsubstance rupture. Clinically, graded reloading is required after immobilization to restore the tendon insertion and to reverse calcaneal disuse osteoporosis.

PMID:
12736878
DOI:
10.1016/s0003-9993(02)04834-7
[Indexed for MEDLINE]

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