Repair of Partial-Thickness Rotator Cuff Tears: A Biomechanical Analysis of Footprint Contact Pressure and Strength in an Ovine Model

Purpose: The purpose of this study was to determine whether transtendon repair by use of a novel small-diameter knotless anchor showed enhanced mechanical properties compared with tear completion and repair. Methods: Articular-sided partial-thickness tears were created ex vivo in the infraspinatus of 24 ovine shoulders. The specimens were randomized into 4 groups of 6 each: (1) no repair, (2) transtendon repair, (3) completion of tear with tension-band single-row repair, and (4) completion of tear with double-row repair. Footprint contact pressure and ultimate load to failure were measured in each specimen. Results: Technical failure of the transtendon anchors occurred in 3 of 15 shoulders. Transtendon repair (mean +/- SEM, 0.8 +/- 0.1 MPa) and double-row repair (1 +/- 0.09 MPa) showed 3-fold (P < .001) greater footprint contact pressures than tension-band single-row repair (0.3 +/- 0.03 MPa) and no repair (0.3 +/- 0.02 MPa). The ultimate load to failure for transtendon repair (544 +/- 22 N) was more than 3 times greater than that for the double-row repair (157 +/- 23 N) (P < .001) and the single-row repair (116 +/- 11 N) (P < .001). Conclusions: Transtendon repair of partial-thickness tears by use of specifically designed anchors biomechanically outperformed tear completion and repair in an ovine model. Transtendon repair showed the best combination of high footprint contact pressure and high ultimate failure load. However, the high insertion failure rate of these transtendon anchors is of concern. Clinical Relevance: On the basis of the biomechanical data, transtendon repair of partial-thickness rotator cuff tears may be used as an alternative to tear completion and repair, but the specific transtendon anchors used in this study need further evaluation before their clinical use can be recommended.