Reverse Shoulder Arthroplasty with a New Convertible Short Stem: Preliminary 2- to 4-year Follow-up Results

Background The Grammont-style reverse shoulder arthroplasty (RSA) has demonstrated complications intrinsic to its design such as tuberosity fracture and scapular notching. A new short-stem press-fit humeral component with an onlay tray has been devised to avert these issues. We hypothesize that the clinical outcomes and rates of humeral complications of this new stem will be comparable to those of the traditional Grammont design and the lateralization obtained from the stem’s lower neck-shaft angle will decrease the rate of notching without creating instability. Methods We retrospectively evaluated 100 patients who underwent RSA with an onlay short-stem humeral component with a minimum follow-up of 2 years. Clinical outcomes as well as standard radiological examinations were documented pre- and postoperatively. Several correlations were analyzed. Results At mean 32.6-month follow-up, the cohort demonstrated a significant improvement in several outcomes: Constant score increased from 25.5 to 69.7 points, mean anterior elevation increased from 82.1° to 141.9°, external rotation from 5.6° to 25.1°, and internal rotation from sacrum to the L3 vertebral level. There was a 30% rate of stem malalignment and 37% rate of scapular notching, not associated with any adverse clinical outcomes. The overall rate of complications was 15%, of which scapular fractures were most common (5%). Conclusion Our short-term results suggest that the clinical outcomes and rates of humeral complications are similar to those reported for the Grammont RSA, demonstrating less scapular notching, but increased scapular stress fractures and potential subsidence of the prosthesis due to the metaphyseal press-fit require further investigations.