Effects of immobilization on achilles tendon healing in a rat model

Abstract

The aim of this study was to evaluate the effects of immobilization and mobilization on the functional and biomechanical recovery of injured Achilles tendons. Male Sprague-Dawley rats were allocated randomly into four groups: (a) sham operation, (b) division only (surgical transection of the Achilles tendon without immobilization), (c) "dummy" external fixation (division of the Achilles tendon and application of Kirschner wires), and (d) rigid external fixation (division of the Achilles tendon and immobilization with Kirschner wires connected by two triangular frames). All procedures were performed on the right lower limb; the left, uninjured, lower limb served as an internal control. Kirschner wires and external fixators were removed on day 12. Functional performance was determined from measurements of hind pawprints of rats walking preoperatively and on postoperative days 1, 3, 5, 7, 9, 11, 13, and 15. On day 15, the animals were killed and biomechanical evaluations were performed on both the injured and the uninjured Achilles tendon constructs. No functional or mechanical deficits were observed in the sham-operation group. Animals subjected to division of the Achilles tendon had an initial functional deficit that returned to near normal by day 15. The application of Kirschner wires was associated with an impairment of the functional performance of the rat as well as of the mechanical properties of the tendon-bone constructs. Immobilization by connection of the Kirschner wires to an external frame had an additional, highly significant (p < 0.001) detrimental effect on the functional and mechanical recovery of Achilles tendon-calcaneal complexes.

How can one platelet injection after tendon injury lead to a stronger tendon after 4 weeks?: Interplay between early regeneration and mechanical stimulation

“…As long as the muscle is relaxed and pliable, traction forces in the tendon callus should be low. Earlier models have used immobilization (Murrell et al 1994, Ishida et al 1996, Iwuagwu and McGrouther 1998, Yamamoto et al 1999, Palmes et al 2002, Matsumoto et al 2003. In animals, it is unclear to what extent immobilization really leads to unloading.…”

Unfavorable effect of knee immobilization on Achilles tendon healing in rabbits

“…Appropriate tendon mobilization accelerates the healing of an injured tendon, and immobilization prevents healing (Woo et al 1981, Gelberman et al 1982, Murrell et al 1994. The reasons for these effects may be as follows.…”

BMP treatment for improving tendon repair Studies on rat and rabbit Achilles tendons

“…The effect was signifi cant for the fi rst weeks, but after 3 weeks the control group had caught up, which suggests that Achilles tendon ruptures should be carefully loaded during the early, rather than later, stages of healing. Murrell (Murrell et al 1994) showed that immobilization by external fi xation in a model of Achilles tendon ruptures in rats had a strong negative effect on the functional and mechanical recovery of the tendon. Immobilization of the leg after tendon transsection in rats was also studied by Rantanen (Rantanen et al 1999).…”

“…The rat tendon model was adopted and further developed from the rat Achilles tendon model described by Murrell et al (1994). The Achilles tendon complex was dissected free from other tissues ( Figure 5).…”

“…In the unloaded version, the ankle of the leg with a transsected tendon was immobilized by external fi xation, which we found traumatic and diffi cult. The insertion of pins for the external fi xation, infl uenced tendon healing dramatically, even when not fi xated (Murrell et al 1994). Instead we tried to unload the healing tendon by denervation of the calf muscle by tibia nerve transsection.…”