Transacromial approach to obtain fusion of unstable os acromiale.

The purpose of this study was to identify possible causes for the low union rate for surgically stabilized os acromiale. Between February 1990 and November 1995, fusion of an os acromiale was attempted in 15 shoulders in 12 patients at our institution. All patients were men. The mean age was 54 years (range 37 to 63 years). All shoulders had an os mesoacromiale considered too large for simple resection. An associated lesion of the rotator cuff ranging from partial-to full-thickness tear was present in all patients. Eleven had an unfused acromial epiphysis in both shoulders. Two different surgical approaches were used. Seven shoulders were approached through an anterior deltoid-off approach, thus potentially devascularizing the os acromiale. Eight shoulders were approached transacromially, preserving the deltoid origin and hence the terminal branches of the thoracoacromial artery. The technique of internal fixation (tension band wiring) was the same for both groups. The mean follow-up was 44 months (range 13 to 72 months). Union, as demonstrated by axial radiographic views, occurred in 3 out of 7 cases with a devascularized os acromiale and in 7 out of 8 shoulders with a perfused os acromiale (P = .017), respectively. Patients with a united os acromiale had a significantly better functional outcome as measured by the Constant score (P = .0169). In conclusion, aiming at a stable fusion of a sizable and hypermobile os acromiale is probably desirable because it enhances the overall functional result. Obtaining consolidation was possible when the vascularity of the acromial epiphysis was respected.