Shoulder Instability in Handball Players

Abstract

Overhead throwing athletes in general and handball players in particular are at risk for shoulder injuries as a result of the high forces sustained by the shoulder during the throwing motion. The glenohumeral joint is formed by an articulation between the humeral head and a relatively small glenoid fossa, allowing a wide range of shoulder movement, however also making it the most commonly dislocated joint of the body. Dynamic stabilizers of the glenohumeral joint include the rotator cuff, the scapulothoracic muscles, and the long head of the biceps tendon. Static stabilizers include the osseous anatomy, the fibrocartilaginous labrum, and the glenohumeral joint capsule. In overhead throwing athletes, while a single traumatic event may result in instability, more commonly it is repetitive overload that leads to failure of one or more of these structures and as a result—to laxity. The throwing action requires a coordinated motion that involves the entire body and has been previously defined as the “kinetic chain” [1]. A well-timed sequential muscle activity is required to produce an effective kinetic chain and transfer energy generated in the lower body to the upper body through the shoulder, arm, hand, and fingers and finally to the ball [2]. Body position, trunk rotation, and positioning of the scapula are key elements in the kinetic chain, and therefore any physical condition that alters the components of the kinetic chain may result in the development of a dysfunctional shoulder [1]. There is a delicate balance between shoulder mobility and stability in elite-level overhead throwing athletes. In fact, the term “the thrower’s paradox” was coined as a result of the need for the shoulder to maintain sufficient mobility to reach extreme positions of rotation to generate ball velocity while maintaining joint stability at the same time [3]. The demands and repetition of high-velocity overhead throwing can alter this stability-mobility relationship and ultimately lead to injury. Stability of the shoulder is maintained by the abovementioned passive and active stabilizers. In the absence of other forces, the torques on the glenohumeral joint are balanced. With each throw, the soft-tissue envelope surrounding the shoulder is loaded at levels that approach its ultimate failure loads, thus making it vulnerable to injury. While the majority of data on injury patterns and mechanisms in the shoulders of high-level overhead throwers are from studies focusing on baseball pitchers [4–8], handball players are different as the handball throwing motion has additional complex features that may impact potential pathologies in the shoulder [9]. Handball is not only an overhead throwing sport but also a contact sport where players commonly encounter upper extremity and/or body contact during and/or at the end of the throwing action. This contact is unpredictable and may expose the shoulder to additional loads in different directions. Handball players perform up to 48,000 throws per year [10], and considering that the throwing arm is frequently and unexpectedly opposed or blocked by an opponent, causing repetitive microtrauma to the capsulolabral structures of the shoulder, it is not surprising to see that most of the acute shoulder injuries occur to players who throw most (backcourt and wing players) [11]. The forces encountered by a player’s shoulder affect the joint, especially during the cocking phase of the throw. In addition, the defense often strains the shoulder by charging the arm (Fig. 15.1). Further understanding of the biomechanics and kinematics of throwing in handball, both normal and pathologic, may assist clinicians to develop effective prevention, treatment, and rehabilitation strategies for this population. The purpose of this chapter is to explore the issue of instability in handball players and provide an information basis to assist with evaluation and treatment of shoulder instability in handball players.