The Effects of Hook Plates on the Subacromial Space. A Clinical and MRI Study

The disruption of the acromioclavicular joint is a relatively common injury of the shoulder girdle, often occurring in young athletes. The therapy of third degree injuries (Tossy III or Rockwood III-VI) is still controversial, and several operative techniques are practiced. In a retrospective study, 28 (= 72%) of the total number of 39 cases with a Tossy III disruption operated in our hospital between January 1998 until December 2002 with a hook plate according to Dreithaler were followed up. The average reexamination interval was 3.0 years (range 1.2-5.6 years) after surgery. Special emphasis was laid upon the question, if the hook had any effects on the subacromial space. The study included clinical, sonographic and MRI examinations of both shoulders in direct side-to-side comparison. About 86% of the patients were satisfied with the functional outcome, but only 54% with the cosmetic result. This was mostly due to remaining elevation of the lateral clavicula and heterotopic ossifications around the acromioclavicular joint, which were found in 43% of the patients without any functional deficit. The outcome-scores (DASH, Taft, Constant-Murley) yielded on the whole very good and good results. Instability of the AC-joint under load was found in seven patients, in three of these instability was severe, and two patients had a chronic subluxation with functional impairment.The sonographic investigation revealed no specific lesions of the rotator cuff in any patient. Age related degenerative changes were seen in 46%, however, the accentuation of the operated side was only 14%. In MRI there was no case of a complete rotator cuff tear. Corresponding to the sonographic examination increased numbers of exostoses, heterotopic ossifications, and arthrosis of the AC-joint were observed.