A 10-Year Comparative Analysis of the Two Most Common Reverse Total Shoulder Arthroplasty Implants (Delta Xtend and SMR) in the New Zealand Joint Registry

Hypothesis and background: As the incidence of reverse total shoulder arthroplasty (RTSA) continues to rise, better understanding of the long-term risks and complications is necessary to determine the best choice of implant. The majority (75%) of RTSA performed in New Zealand use either SMR (Systema Multiplana Randelli, Lima-LTO, Italy) or Delta Xtend (DePuy Synthes, USA). The aim of this registry-based study was to compare implant survival, risk of revision and reasons for revision between the two most frequently used RTSA prostheses: SMR and Delta Xtend.

Methods: Using data from the New Zealand Joint Registry between 1999 and 2022, we identified 5,891 patients who underwent RTSA using either SMR cementless (62.8%) or Delta Xtend prostheses (37.2%). Delta Xtend was sub-divided into cementless (31.4% of total) and cemented humeral stem (5.8% of total) sub-groups for analysis. Revision-free implant survival and functional outcomes (Oxford Shoulder Score [OSS] at 6-months, 5-years, and 10-years were adjusted by age, American Society of Anesthesiologists (ASA) grade, indication, sex, and surgeon volum for between-group comparisons.

Results: Ten-year revision-free implant survival was 93.0%, 92.5%, and 95.8% for Delta Xtend cemented, Delta Xtend cementless and SMR, respectively. The Delta Xtend cemented implant had a two-fold higher adjusted revision risk compared to both the Delta Xtend cementless and the SMR cementless implants (Hazard Ratio [HR]=2.04, p=0.011; and HR=2.59, p<0.001, respectively). There was no significant difference between the Delta Xtend cementless and SMR cementless groups (HR=1.28, p=0.129). The Delta Xtend cemented group was significantly (p≤0.01) older, more co-morbid (ASA 3-4), female and indicated for fracture compared to other groups. The most common reason(s) for revision was aseptic loosening and infection for Delta Xtend cementless; aseptic loosening, instability/dislocation and infection for Delta Xtend cemented; and aseptic loosening alone for SMR cementless. Average OSS was significantly lower in Delta Xtend cemented compared to Delta Xtend cementless and SMR cementless at 6 months (30.8, 35.9 vs. 35.6, respectively, p<0.01) and 5 years (37.4, 40.7 vs. 39.5, respectively, p<0.01).

Conclusions: Overall, we found Delta Xtend cemented group had over two-fold the risk of revision compared to Delta Xtend cementless and SMR cementless groups, while there was no difference in revision risk between the Delta Xtend and SMR cementless prostheses. As the incidence of reverse total shoulder arthroplasty (RTSA) continues to rise, better understanding of the long-term risks and complications is necessary to determine the best choice of implant.