Long-term impact of scapular notching after reverse shoulder arthroplasty.

Background: Because it medializes the centre of rotation, one of the drawbacks of reverse shoulder arthroplasty (RSA) is the risk of impingement between the humerus and lateral border of the scapula resulting in scapular notching. The long-term impact of this notching is not well known, either on function or the risk of glenoid loosening. The aim of this longitudinal study was to analyze the drawbacks of this notching.

Methods: Between 1993 and 2006, 81 patients (91 shoulders) underwent RSA for primary glenohumeral osteoarthritis or massive cuff tear with or without osteoarthritis. This cohort was followed longitudinally with post-operative assessments done at one to two  years (T1), three to eight  years (T2), and nine+ years (T3). Before T3, 25 patients had died, nine were lost to follow-up, five  had the implants changed, and seven  had incomplete records. Thus, 45 shoulders were available for follow-up beyond nine years (mean follow-up of 12 years) and were used to determine the long-term impact of notching. Survival curves were generated using the occurrence of Sirveaux grade 3 or 4 notching and the presence of aseptic glenoid loosening as endpoints.

Results: The survivorship before grade 3 or 4 notching developed was 83% at five years, 60% at 10 years, and 43% at 15 years. In the end, aseptic glenoid loosening occurred in four shoulders, all of which had developed grade 4 notching. No glenoid loosening occurred in the population with grade 0, 1, 2, or 3 notching (p = 0.02). The Constant score significantly decreased between T2 and T3, although it was not different between shoulders with and without advanced notching.

Conclusions: Beyond the second year post-RSA, the number of shoulders with grade 3 or 4 notching increases steadily up to the longest follow-up. Grade 4 notching always preceded the occurrence of late glenoid loosening. The functional outcomes become significantly worse after the 9th year post-RSA, although they were not correlated to the presence of high-grade scapular notching.