After a short introduction to the topics of this thesis, in chapter 2 we described the functional and radiological results of a retrospective study in patients with an ipsilateral scapular neck and clavicular shaft fracture (floating shoulder). Forty-six patients were treated between 1991 and 1996. Thirty-five patients remained available for analysis (follow-up: 35 months). Thirty-one patients had been initially treated non-operatively and four operatively. Three patients underwent secondary surgery. Both operatively as non-operatively treated patients had a fair to good functional outcome (Constant score 71 versus 76). A correlation was found between radiological result (angular malunion of the neck) and functional result. Our study results suggest that conservative treatment is preferred in patients with an ipsilateral clavicular and scapular neck fracture, in absence of angular malunion. Fair to poor functional results are reported in literature on patients with a displaced scapular neck fracture. In chapter 3 occurrence of malunion was analysed in conservatively treated patients with a scapular neck fracture in relation with the clinical outcome. In the period 1991 and 2001, 24 patients with a locally isolated scapular neck fracture were treated. Thirteen patients were available (follow-up: 5.5 years). In four patients a translational displacement > 1 cm was found, but no significant angular displacement. The mean Constant score of all 13 patients was 90. This study suggests that there is no correlation between occurrence of translational displacement of the scapular neck and a poor functional result. In chapter 4 a biomechanical study was described .The aim was to identify a mechanical cause for loss of shoulder function in case of a malunited scapular neck. A 3D computer model was used to analyse shoulder biomechanics. Abduction of the humerus and loading of a 90º abducted humerus were simulated with presence and absence of caudal displacement of the glenoid. The patterns of muscle activation were studied, with attention to the rotator cuff muscles. A difference in muscle activation was found between the control and malunion cases. The rotator cuff muscles were significantly shortened in the fracture cases and their generated forces were strongly reduced when the humerus was loaded at 90º abduction. From the current study it appears that loss of the rotator cuff function can be compensated by other muscles with larger moment arms. In chapter 5, the current status of the anatomical, biomechanical and clinical aspects of a floating shoulder is reviewed. It is suggested in literature that in patients with a floating shoulder, O.R.I.F. of the clavicular shaft fracture will reduce the displaced scapular neck fracture and prevent malunion. In chapter 6 is explained-by presentation of three case reports- that this generally accepted theory is not correct. In chapter 7 an anatomical study is presented in which the best position of the arm for achieving an adequate exposure to the scapular neck and the safest distance of both axillary and suprascapular nerve to the glenoid is determined. Thirteen fresh-frozen shoulders were dissected through a posterior surgical approach.. The distance of neurovascular structures to the glenoid was measured with the arm in different positions. A significant increase in axillary nerve-glenoid distance by abducting the arm was observed in all cases. It was concluded that abduction of the arm facilitates the exposure to the scapular neck. Abduction up to 90º particularly in combination with external rotation of the arm increases the "safe zone" between the branch of the axillary nerve innervating the teres minor muscle and the glenoid. The posterior surgical approach according to Brodsky is elucidated in chapter 8 by presentation of a patient who was treated by O.R.I.F. of a displaced glenoid fracture.
