For a lesion that appears to be so simple, complete acromioclavicular dislocation can be one of the least satisfactory of traumatic injuries to treat. It is rarely difficult to reduce the dislocation but to hold the reduction is another matter.Structure and FunctionThis problem is best approached by a brief consideration of the structure and function of the parts involved. In man, the upper extremity is not normally used for weight bearing but largely for prehension and tactile information — uses that require an extreme degree of freedom and as full a range of motion as possible. Such mobility . . .