A Biomechanical Comparison of Repair Techniques for Complete Gluteus Medius Tears

Lateral hip pain has been associated with tears of the gluteus medius muscle. When conservative management fails, repair is necessary. However, biomechanical properties of repair constructs for gluteus medius tendon tears have not previously been described. In the present study, sixteen fresh-frozen human cadaveric hemi-pelves were tested. Bone mineral density and anatomical measurements were evaluated. Six specimens received Double Row with Massive Cuff Stitch (DR-MCS) repair, six received Double Row with Knotless Lateral Anchors (DR-KLA), and four remained intact. Markers were placed on the tissue for video tracking. Intact specimens were preloaded to 10N and loaded to failure at 1 mm/sec to establish a cyclic testing protocol for the repair groups. Repaired specimens were preloaded to 10N, loaded from 10N to 125 N at 90 N/s for 150 cycles, and then loaded to failure at 1 mm/sec. The superoposterior footprint length was found to be significantly greater than the lateral footprint length. Cyclic segment elongation was significantly higher for the DR-MCS than the DR-KLA. The DR-KLA showed a significantly higher (p<0.05) normalized yield load than the DR-MCS. Linear stiffness and post yield extension for the DR-MCS were significantly higher than the DR-KLA. At yield load, the optically measured soft tissue elongation of the DR-KLA was significantly greater than the DR-MCS. Mechanical properties of the selected repair constructs were inferior to those of the intact unit. The DR-KLA repair exhibited its first signs of detachment closer to the point of complete failure by anchor pullout, while the DR-MCS repair showed initial failure earlier by suture rupture. Bone mineral density was strongly correlated to maximum load for the DR-KLA repair. Anatomical data from patients are vital to the selection of an appropriate repair method, in which BMD must be taken into account. Results indicate that both repair constructs have adequate mechanical integrity to withstand early rehabilitation post-operatively.