Rat Model of Gluteus Medius Tendon Tear: Biomechanical and Histological Effects of Autologous Fascia Lata Augmentation

Abstract

Background:

Primary repair of full-thickness gluteus medius tears is challenging, particularly in retracted tears with poor tissue quality. Augmentation with autologous fascia lata may enhance repair strength and biologic healing.

Purpose:

To establish a gluteus medius tear detachment model in rats and to evaluate whether acute repair augmented with autologous fascia lata results in higher failure load and improved tendon-bone interface organization as compared with primary repair.

Study Design:

Controlled laboratory study.

Methods:

Forty adult female Sprague-Dawley rats were randomly assigned to 4 groups: intact control (group C), unrepaired tear (group 1), primary repair (group 2), and augmented repair with autologous fascia lata (group 3) (n = 6 for biomechanical testing, n = 4 for histological analysis per group). In groups 1 to 3, the gluteus medius tendon was detached from the greater trochanter. Group 1 underwent no repair. In groups 2 and 3, repair was performed acutely during the index procedure immediately after tendon detachment, using intraosseous tunnels and 5-0 Prolene sutures; in group 3, an autologous fascia lata graft was incorporated as an onlay augmentation. At 4 weeks, animals were euthanized for biomechanical and histological evaluation.

Results:

All tendons failed at the tendon-bone interface. Failure load was lower in group 1 (mean ± SD, 15 ± 6 N; P = .01) and group 2 (20 ± 4 N; P = .03) than in group C (29 ± 7 N), while group 3 (30 ± 7 N) did not differ from group C (P = .60). Group 3 had higher strength than groups 2 (P = .01) and 1 (P = .004). Histological scores were lowest in group 1 (3 ± 0.5) as compared with group C (8 ± 1; P = .01), group 2 (12 ± 2; P < .001), and group 3 (11 ± 1; P = .001), with no difference among groups C, 2, and 3 (P > .05).

Conclusion:

In a rat gluteus medius tendon detachment model, unrepaired detachment resulted in inferior biomechanical strength and histological healing at 4 weeks. Augmentation with autologous fascia lata improved biomechanical strength as compared with primary repair.

Clinical Relevance:

This rat model may be useful for preclinical evaluation of repair strategies for gluteus medius tears. Autologous fascia lata augmentation may offer biomechanical advantages over primary repair alone.