Strength of a new method of achilles tendon repair in the rat - biomed 2011.

The rat Achilles tendon is frequently used as the model for tendon healing research. Several methods commonly employed in these studies may confound results. The Kessler method of suture repair requires immobilization of the operative extremity, which can be detrimental to healing. Determination of cross-sectional area of tendons by caliper measurement may lead to significant errors in normalization of biomechanical data for stress and elastic modulus. New methods of suture repair of rat Achilles tendons and micro-CT scanning of tendons are presented as preferable techniques for tendon healing studies in rats. Operations involved transection of the right Achilles tendon at the mid-portion and suture repair using a 4-strand, looped locking technique. Groups were: positive control (no injury or treatment); negative control (injury, suture repair, no healing); 2 week repair; and 4 week repair. The cross-sectional area of the tendons was significantly higher (p<0.05) in the repair groups compared to controls. Peak stress and elastic modulus of repair groups were significantly lower than positive control. Strain of repair groups was not significantly different from control. Four weeks after repair, tendons bore significantly higher peak loads than positive control tendons. Based on these results, further studies of adjunct therapy for tendon healing may be placed in the context of normal (repair groups), ideal (positive control), and worst case (negative control) healing. The methods presented for new a new surgical technique and cross-sectional area calculation are reliable for animal studies and increase the validity and applicability of biomechanical results.