Rate of Improvement in Clinical Outcomes with Anatomic and Reverse Total Shoulder Arthroplasty
Authors: Simovitch Ryan W. , Friedman Richard J. , Cheung Emilie V. , Flurin Pierre-Henri , Wright Thomas , Zuckerman Joseph D. , Roche Christopher 
Published: November 2019

Background:
This study quantifies the rate of improvement after anatomic and reverse total shoulder arthroplasty; a better understanding of the rate of improvement associated with each prosthesis type may better establish patient expectations for recovery.

Methods:
Prospectively collected data on 1,183 patients who underwent either anatomic total shoulder arthroplasty (n = 505) or reverse total shoulder arthroplasty (n = 678) were collected. The Simple Shoulder Test (SST), University of California at Los Angeles (UCLA) Shoulder, American Shoulder and Elbow Surgeons (ASES), Constant, and Shoulder Pain and Disability Index (SPADI) scores, along with range of motion, were recorded preoperatively and at routine postoperative time points. All included patients had a minimum follow-up of 2 years. The rate of improvement of these outcome measures was quantified for patients who underwent anatomic total shoulder arthroplasty and those who underwent reverse total shoulder arthroplasty to compare recovery over time.

Results:
In this study, 3,587 visits by 1,183 patients were analyzed and several differences between prosthesis types were noted. Patients who underwent reverse total shoulder arthroplasty experienced larger improvements in the Constant score and active forward flexion, and patients who underwent anatomic total shoulder arthroplasty demonstrated better improvement in external rotation compared with patients who underwent reverse total shoulder arthroplasty at nearly all time points. By 72 months, improvement in flexion and abduction decreased for each prosthesis type, but in particular for reverse total shoulder arthroplasty. Full improvement was achieved by 24 months, although the majority of improvement was achieved in the first 6 months, with all 5 scoring metrics following a similar rate of improvement. The ASES, SPADI, and UCLA Shoulder scores closely mirrored each other in the magnitude of improvement, and the SST score demonstrated the largest improvement and the Constant score demonstrated the smallest improvement for both anatomic total shoulder arthroplasty and reverse total shoulder arthroplasty.

Conclusions:
Both anatomic total shoulder arthroplasty and reverse total shoulder arthroplasty reliably result in improved patient outcomes. However, anatomic total shoulder arthroplasty more reliably improves range of motion, particularly external rotation. Most improvement occurs by 6 months, with some additional improvement up to 2 years for both anatomic total shoulder arthroplasty and reverse total shoulder arthroplasty. Although the indications for anatomic total shoulder arthroplasty and reverse total shoulder arthroplasty are substantially different, in addition to the biomechanical differences, the improvement in outcome scores over time can be expected to be very similar. This study is helpful to patients and health-care providers to establish expectations regarding the rate of recovery after total shoulder arthroplasty.

Level of Evidence:
Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.