Does an increase in modularity improve the outcomes of total shoulder replacement? Comparison across design generations.

BACKGROUND/PURPOSE: Modularity in total shoulder arthroplasty (TSA) has increased over the past 30 years. Our institution previously showed shoulders treated with modular humeral head/stem arthroplasties had similar outcomes to monoblock designs. Presently, we aim to update clinical follow-up of 2nd generation TSAs and assess how increased modularity affects early outcomes and survivorship across three generations of implants.

MATERIALS AND METHODS

Between 1997 and 2001, 75 second generation modular TSA's were performed for primary osteoarthritis. Shoulders were followed for a minimum of 2 years or until reoperation, mean 7.4 years. Results were compared with first generation monoblock TSAs and third generation TSAs which offered multiple humeral head shape options to more precisely replicate patient anatomy.

RESULTS

Second generation TSAs continue to show significant improvements in pain, elevation and external rotation: 90 % of shoulders were subjectively better at follow-up. Survivorship was estimated to be 89.0 % at 10 years. All generations showed similar pain relief, and improved range of motion and Neer ratings. Survivorship among the 3 groups was similar at 5 years but was estimated to be higher in the 1st generation group at 7 years. More glenoids were radiographically at risk in the 2nd and 3rd generation groups than in the 1st; however, this did not reach significance.

INTERPRETATION

With extended mid-term follow-up, second generation anatomic TSA continues to provide improvements in pain and range of motion for primary OA. Implant modularity can facilitate surgery, but similar clinical outcomes can be expected regardless of modularity.

LEVEL OF EVIDENCE

Level IV, Treatment study.