The course of the repair of the rotator cuff rupture has not been fully clarified in comparison with that of other tendons. The purpose of this study is to deliniate the repair of the canine rotator cuff rupture histologically in two instances; 1) only resection of the rotator cuff tendon, 2) tendon to bone repair after cuff resection.
Twenty-four adult mongrel dogs (12-17kg) were used. The study was divided into two groups: group I. Only resection of the rotator cuff; rotator cuff was resected 15mm in width and 1mm in length. Group II. Tendon to bone repair after cuff resection; the stump of the cuff was anchored into the trough cut at the greater tuberosity. After operation, a plaster cast was applied for three weeks. Dogs were killed at regular intervals and specimens including the cuff and the greater tuberosity were obtained. These were fixed, decalcified, embedded in paraffin, sectioned and stained with hematoxylin and eosin and with Malloryazan.
The gross and microscopic changes were investigated. Group I. After 1 week, scar tissue formation was present, but not completely, at the gap between the proximal stump and the greater tuberosity. After 2 weeks, the gap was completely filled with scar tissue. After 6 weeks, orientation of fibers was at randon with many proliferating vessels. Group II. After 2 weeks, orientation of the fibers were at random with proliferation of blood vessels. At the tendo-osseous junction, proliferation of cartilage tissue was noted. After 24 weeks, orientation of collagen fibers and appearance of tendo-osseous junction were similar to those seen in normal rotator cuff.