Conversions from anatomic shoulder replacements to reverse total shoulder arthroplasty: do the indications for initial surgery influence the clinical outcome after revision surgery?

The most frequent indications for anatomic shoulder replacement are glenohumeral osteoarthritis and fractures of the humeral head. If anatomic shoulder prostheses fail, reverse total shoulder arthroplasty is often the only remaining treatment option. This study evaluates the influence of indications for primary shoulder arthroplasty on the clinical outcome after conversion to reverse total shoulder arthroplasty. From 2010 to 2012, 44 failed shoulder arthroplasties were converted to reverse total shoulder arthroplasty. Forty-four patients were available for follow-up after a mean of 24 months (14-36 months). Twenty-three of them had received an initial shoulder replacement because of osteoarthritis, while the remaining 21 patients had been treated for a fracture of the humeral head. At follow-up, patients were assessed with X-rays, constant-, and ASES scores. The total number of observed complications was higher in patients revised because of failed fracture arthroplasty (24 vs. 9%). Patients initially treated for osteoarthritis achieved a higher ASES score (71 vs. 59 points; p = 0.048). The normalized constant score was not different between the two observed groups (osteoarthritis 73% vs. fracture 67%: p = 0.45). Complications occurred more often in patients who had initially suffered from a fracture of the humeral head (fracture 23.8% vs. osteoarthritis 8.7%). Scapular notching was more frequent after initial fracture arthroplasty (33 vs. 14%). Indications for initial shoulder replacement have an influence on the clinical outcome after conversion to reverse total shoulder arthroplasty. Patients initially treated for a fracture of the humeral head have a lower subjective outcome and a higher complication rate in comparison with patients initially treated for osteoarthritis. IV (Retrospective study).