Fascia lata autografts achieve interface healing with the supraspinatus muscle histologically and mechanically in a rat supraspinatus tendon reconstruction model for massive irreparable rotator cuff tears.

PURPOSE: To evaluate the histologic healing process and mechanical characteristics of the interface between a fascia lata autograft and supraspinatus muscle by establishing a supraspinatus tendon reconstruction model for chronic massive, irreparable rotator cuff tears (MIRCTs).

METHODS: A total of 40 rats were studied. Eight rats were sacrificed to establish an intact control group, and the other rats were first established as the chronic MIRCTs model and then developed as the supraspinatus tendon reconstruction model. Histology, fatty infiltration, mechanics and the open field test for the interface between the fascia lata autograft and muscle were assessed at 2, 4, 8 and 16 weeks postoperatively.

RESULTS: Histologically, the interface between the fascia lata autograft and muscle gradually regenerated structural similarities to the normal muscle-tendon interface by 16 weeks postoperatively. The amounts of collagen I and III were both increased significantly during the healing time and stabilized at 8 weeks postoperatively. Fatty infiltration was obvious in the supraspinatus muscle 4 weeks after the MIRCTs model. However, the degree of fatty infiltration in the supraspinatus muscle gradually decreased after supraspinatus tendon reconstruction and stabilized at 8 weeks postoperatively. The ultimate failure force and the ultimate stress gradually increased from 2 to 16 weeks and reached the level of the intact control tendon at 16 weeks postoperatively (P=0.086). The movability of the forepaw returned to normal in the open field test (P=0.907).

CONCLUSIONS: In this rat supraspinatus tendon reconstruction model, fascia lata autografts showed good interface healing with the supraspinatus muscle, and fatty infiltration in the supraspinatus muscle was histologically decreased. The interface between the fascia lata autograft and muscle can sustain mechanical strength similar to the anatomical muscle-tendon interface.

CLINICAL RELEVANCE: The supraspinatus tendon reconstruction technique using fascia lata autografts might be a good histological and biomechanical option for treating MIRCTs.