Introduction Displaced fractures of the midshaft clavicle often results in malunion with angulation and foreshortening. The purpose of this study is to determine the secondary effects of clavicular shortening on the sternoclavicular joint and scapulo-thoracic relationship, and to evaluate the symptomatic and biomechanical outcome in these patients.

Methods A series of 10 patients each with a malunited fractured clavicle defined by relative shortening of more than 15 mm were examined. A self-administered questionnaire for assessment of symptoms and function of the ipsilateral shoulder was completed for each patient. Computer tomography and three dimensional reconstructions of both shoulders were undertaken for static anatomical measurements. Biomechanical testing comparing both shoulders in each patient measured strength and velocity of movement. All subjects were symptomatic in the injured shoulder.

Results There were statistically significant differences between injured and uninjured shoulders for both mean shoulder scores and visual analog global assessments of shoulder function. Clavicular shortening produced statistically significant increased upward angulation of the clavicle at the sternoclavicular joint (p< 0.005), increased lateral displacement of the scapula on the posterior wall, and anterior scapular version (p< 0.05). Biomechanical differences were also recorded including a reduction in muscular strength for adduction, extension, and internal rotation of the humerus and also a reduced peak abduction velocity in the injured shoulder (p< 0.05).

Conclusions Changes in static sternoclavicular and scapulothoracic relationships occur following short malunion of the clavicle and are possible mechanisms limiting shoulder function after this injury. This study provides evidence that consideration should be given to prevention of clavicle malunion by open reduction and internal fixation, especially in the young and active age group.