ACL reconstruction using hamstring tendons has gained general acceptance. However, it has been recommended to seek a tight fit of the tendon in the bone canal in order to provide circumferential contact and healing of the graft, and to prevent secondary tunnel widening. Recent findings show, that the graft dynamically adapts to pressure in the canal resulting in a potentially loose graft-bone contact. It was the goal of this study to understand the viscoelastic behaviour of hamstring grafts under pressure and to develop a new method for tendon pre-conditioning to reduce the graft volume before implantation, in order to reduce the necessary bone canal diameter to accommodate the same graft. Flexor digitorum tendons of calf and extensor digitorum tendons of adult sheep were identified to be suitable as ACL grafts substitutes for human hamstring tendons in vitro. The effect of different compression forces on dimensions and weight of the grafts were determined. Further, different strain rates (1mm/min vs 10mm/min), compression methods (steady compression vs. creep) and different compression durations(1, 5, 10min) were tested to identify the most effective combination to reduce graft size by preserving its macroscopic structure.Introduction
Material and Methods
Following tear of its tendon, the muscle undergoes retraction, atrophy and fatty infiltration. These changes are inevitable and considered irreversible and limit the potential of successful repair of musculotendinous units. It was the purpose of this study to test the hypothesis that administration of anabolic steroids can prevent these muscular changes following experimental supraspinatus tendon release in the rabbit. The supraspinatus tendon was experimentally released in 20 New Zealand rabbits. Musculotendinous retraction was monitored over a period of 6 weeks. The seven animals in group I had no additional intervention, six animals in group II had local and seven animals in group III had systemic administration of nandrolone deconate during six weeks of retraction. At the time of sacrifice, in-vivo muscle performance as well as radiologic and histologic muscle changes were investigated.Introduction
Methods
