Does arm lengthening affect the functional outcome in onlay reverse shoulder arthroplasty?

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Reconstructive surgery

Background:

• Onlay design reverse shoulder arthroplasty offers an alternative to traditional Grammont-type prostheses to mitigate complications.
• This study investigates the impact of arm lengthening on short-term outcomes in onlay reverse shoulder arthroplasty.

Purpose of the Study:

• To determine the influence of arm lengthening on clinical outcomes in onlay reverse shoulder arthroplasty.
• To assess the effect of humeral tray offset on arm lengthening and range of motion.

Main Methods:

• Retrospective analysis of 56 patients undergoing onlay reverse shoulder arthroplasty with a minimum 2-year follow-up.
• Bilateral scaled radiographs used to measure arm lengthening; Constant score and active range of motion documented pre- and postoperatively.
• Analysis of relationships between arm lengthening, humeral tray offset, and functional outcomes.

Main Results:

• Significant improvement in Constant scores (25.5 to 71.5) and range of motion (anterior elevation 145.2°, external rotation 30.7°).
• Arm lengthening >2.5 cm correlated with reduced anterior elevation; lengthening of 1-2.5 cm associated with improved Constant scores.
• Humeral tray positioning did not significantly impact functional outcomes; lateral offset showed a trend towards increased lengthening.

Conclusions:

• Onlay reverse shoulder arthroplasty demonstrates favorable short-term clinical results.
• Optimal arm lengthening for onlay reverse shoulder arthroplasty appears to be between 1-2.5 cm, balancing range of motion and functional improvement.