Relationship between coracoacromial arch and rotator cuff analysed by a computer-assisted method

Background In this paper we describe and assess the feasibility of a computer-assisted method which could be useful to investigate the mechanism of subacromial impingment of the shoulder. Methods The relationship between the infraspinatus and supraspinatus and the coracoacromial (CA) arch during passive elevation and abduction are described. The methodology is based on the use of a tracker for recording surfaces and passive movements and data elaboration using dedicated software. Results In four cadavers, we observed that the minimal distances between the rotator cuff insertions and CA arch were realized at 45° abduction between the acromion and infraspinatus, at 50-90° elevation between the acromion and supraspinatus and also at 45-70° abduction between the CA ligament and supraspinatus. This study showed that the proposed method is able to provide repeatable kinematic data (ICC ≥ 0.90), numerical anatomical data comparable with the literature and, moreover, individual measurements on the shoulder joint. Conclusions This preliminary results support the extension of the methodology to an in vivo protocol to be used during computer-assisted arthroscopic surgery.