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 degrees abduction between the acromion and infraspinatus, at 50-90 degrees elevation between the acromion and supraspinatus and also at 45-70 degrees abduction between the CA ligament and supraspinatus. This study showed that the proposed method is able to provide repeatable kinematic data (ICC > or = 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.