In this study, the investigators intend to demonstrate that the hook plate may have adverse effects on subacromial structures even with a short period of hardware retention. The investigators also sought to determine if musculoskeletal sonography could be used as a tool to demonstrate shoulder pathology such as subacromial impingement or rotator cuff tear in patients receiving hook plate fixation. The clinical results of patients receiving hook plate fixation, specifically bony union, pain relief, shoulder function and range of motion (ROM), were also evaluated.

Inclusion Criteria:

• The patient received surgical treatment for AC joint dislocation of unstable distal clavicle fracture in our hospital from December 2007 to January 2009.

Exclusion Criteria:

• The patient who was expired or the injured limb has preexisting injury or neurological deficit.

The patient received surgical treatment for AC joint dislocation of unstable distal clavicle fracture