Patient PW was a 48-year-old male triathlete who had bilateral os acromiale, but only the left side was locally symptomatic. The acromion was sensitive on palpitation and after swimming. All impingement signs were negative and the ultrasound and magnetic resonance imaging (MRI) showed marked oedema at the os acromiale but did not reveal any rotator cuff tendinopathy. The patient was first treated with local conservative therapy. This included physical therapy with ice and an infiltration of the os acromial joint with Kenacort and Xylocaine 2%. This gave immediate pain relief for a few hours. Conservative treatment was unsuccessful, meaning that an operation was necessary. In this case, nine screws (2.7- and 3.5-mm) were used. Six anterior angle-stable screws were necessary. Posteriorly two cortical screws (one of which was used for compression) and two angle-stable locking screws were used. Because of the congenital or primary pseudarthrosis, an osteotomy of 1 mm was performed on each side of the osseous non-union including the cranial osteophytes. These bone remnants were pulverized and replaced between or lateral to the plate and the osteotomy site. The control radiography showed correct positioning.
Patient TR was a 67-year-old woman who had a left-side os acromiale together with a rotator cuff tear, a type of partial articular supraspinatus tendon avulsion and a biceps hourglass impingement. The first operation (2009) was an arthroscopic decompression, biceps tenotomy and rotator cuff repair. Because of recurrent pain with documented impingement syndrome, an osteosynthesis with an osteosynthesis plate was performed. An osteotomy of 1 mm was performed either side of the non-union. Fixation was achieved using cortical and angle-stable screws (14 or 16 mm) and one compression screw was used. Her acromion was so small that the usual procedure of inserting 3.5-mm hollow screws was not possible. The bone remnants were pulverized and used as a bone graft.