The results of this study demonstrated that transosseous and single-row suture anchor repairs for subscapularis tendon repair are comparable in terms of ultimate strength and contact area, but significantly different in terms of conditioning elongation. The results also confirmed the efficacy of a set of modifications to current techniques in biomechanical testing of rotator cuff repairs. Whereas most rotator cuff tendon tests have utilized axial loading, our study applied physiologically accurate, rotational loads to simulate the mechanism of injury of the subscapularis. By gripping the nylon strap instead of the tendon itself, we were able to fully preserve the physiologic structure of the subscapularis and eliminate tissue slippage from the clamp. Stitching and nylon have been used before, but it is important to identify the technique as a significant improvement from freezing clamps and soft tissue grips. Freezing clamps introduce the unnecessary risk of altering the physiology of the repair site. Soft tissue grips are often unable to grip the subscapularis without slippage. Past studies have used digitizers to measure contact area a technique that Park et al. suggest may determine repair site area coverage rather than contact. Other investigators have found the contact area between tendon and tuberosity footprint using pressure-sensitive film, which can be influenced by changes in initial force on the tendon. The findings are indicative of initial pressure measurement during suture tying and initial load, rather than the actual contact pressure during loading. The advantage of our tactile-pressure measurement system is that the contact area and pressure can be measured in real-time. As improvements in rotator cuff repair techniques continue to develop, tactile-pressure measurements, taken in real-time, will be a valuable tool in attempts to understand the contact characteristics required for optimal biological healing.
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