Biomechanical Comparison of Open Transosseous Versus Arthroscopic Suture Anchor Repair of the Subscapularis Tendon

There has been interest in improving arthroscopic subscapularis repairs due to their popularity and efficacy when compared to open subscapularis repairs. However, previous biomechanical analyses of rotator cuff repairs have typically focused on the supraspinatus tendon [1–5]. Testing repair techniques in the subscapularis tendon requires the modification of previously established biomechanical testing methods. Most rotator cuff tendon tests have utilized axial loading on supraspinatus and infraspinatus tendons [1–4]. Most subscapularis tendons are torn with forced external rotation of the shoulder. Axial loading of the subscapularis tendon would not be representative of the injury mechanism. Additionally, past rotator cuff studies have employed a variety of techniques for clamping tendons, including freezing clamps and soft tissue grips. Such methods offer insufficient fixation for tendons that have high muscle content, such as the subscapularis. Several studies have focused on the repair’s ability to restore the appropriate healing environment at insertion footprint. These investigations have used either digitizers or pressure-sensitive film to measure contact area [5–7]. However, there are questions concerning the repeatability and accuracy of the results provided by these techniques. The objective of this study was to compare the biomechanical performance of open, transosseous fixation with that of the arthroscopic, suture anchor technique for subscapularis repair, while making three specific improvements to current testing methods. It sought to: 1) apply physiologically accurate loads to the subscapularis using cyclic, external rotation, 2) identify an effective method of clamping tendons with high muscle content, such as the subscapularis, and 3) introduce a novel, tactile pressure measurement system that measures contact pressure and area in real-time.