Are Age and Patient Gender Associated With Different Rates and Magnitudes of Clinical Improvement After Reverse Shoulder Arthroplasty?

Abstract

Background: An improved understanding of how gender differences and the natural aging process are associated with differences in clinical improvement in outcome metric scores and ROM measurements after reverse total shoulder arthroplasty (rTSA) may help physicians establish more accurate patient expectations for reducing postoperative pain and improving function.

Questions/purposes: (1) Is gender associated with differences in rTSA outcome scores like the Simple Shoulder Test (SST), the UCLA Shoulder score, the American Shoulder and Elbow Surgeons (ASES) Shoulder score, the Constant Shoulder score, and the Shoulder Pain and Disability Index (SPADI) and ROM? (2) Is age associated with differences in rTSA outcome scores and ROM? (3) What factors are associated with the combined interaction effect between age and gender? (4) At what time point during recovery does most clinical improvement occur, and when is full improvement reached?

Methods: We quantified and analyzed the outcomes of 660 patients (424 women and 236 men; average age, 72 ± 8 years; range, 43-95 years) with cuff tear arthropathy or osteoarthritis and rotator cuff tear who were treated with rTSA by 13 shoulder surgeons from a longitudinally maintained international database using a linear mixed effects statistical model to evaluate the relationship between clinical improvements and gender and patient age. We used five outcome scoring metrics and four ROM assessments to evaluate clinical outcome differences.

Results: When controlling for age, men had better SST scores (mean difference [MD] = 1.41 points [95% confidence interval {CI}, 1.07-1.75], p < 0.001), UCLA scores (MD = 1.76 [95% CI, 1.05-2.47], p < 0.001), Constant scores (MD = 6.70 [95% CI, 4.80-8.59], p < 0.001), ASES scores (MD = 7.58 [95% CI, 5.27-9.89], p < 0.001), SPADI scores (MD = -12.78 [95% CI, -16.28 to -9.28], p < 0.001), abduction (MD = 5.79° [95% CI, 2.74-8.84], p < 0.001), forward flexion (MD = 7.68° [95% CI, 4.15-11.20], p < 0.001), and passive external rotation (MD = 2.81° [95% CI, 0.81-4.8], p = 0.006). When controlling for gender, each 1-year increase in age was associated with an improved ASES score by 0.19 points (95% CI, 0.04-0.34, p = 0.011) and an improved SPADI score by -0.29 points (95% CI, -0.46 to 0.07, p = 0.020). However, each 1-year increase in age was associated with a mean decrease in active abduction by 0.26° (95% CI, -0.46 to 0.07, p = 0.007) and a mean decrease of forward flexion by 0.39° (95% CI, -0.61 to 0.16, p = 0.001). A combined interaction effect between age and gender was found only with active external rotation: in men, younger age was associated with less active external rotation and older age was associated with more active external rotation (β0 [intercept] = 11.029, β1 [slope for age variable] = 0.281, p = 0.009). Conversely, women achieved no difference in active external rotation after rTSA, regardless of age at the time of surgery (β0 [intercept] = 34.135, β1 [slope for age variable] = -0.069, p = 0.009). Finally, 80% of patients achieved full clinical improvement as defined by a plateau in their outcome metric score and 70% of patients achieved full clinical improvement as defined by a plateau in their ROM measurements by 12 months followup regardless of gender or patient age at the time of surgery with most improvement occurring in the first 6 months after rTSA.

Conclusions: Gender and patient age at the time of surgery were associated with some differences in rTSA outcomes. Men had better outcome scores than did women, and older patients had better outcome scores but smaller improvements in function than did younger patients. These results demonstrate rTSA outcomes differ for men and women and for different patient ages at the time of surgery, knowledge of these differences, and also the timing of improvement plateaus in outcome metric scores and ROM measurements can both improve the effectiveness of patient counseling and better establish accurate patient expectations after rTSA.

Level of evidence: Level III, therapeutic study.

Fig. 1

Average clinical improvement in active external rotation changes with patient age differently between male and female patients undergoing rTSA.

Fig. 2

Percentage of patients undergoing rTSA experiencing clinical improvement, as quantified by five outcome scoring metrics, varies with followup time, where the majority of improvement occurs in the first 12 months after surgery.

Fig. 3

Percentage of patients undergoing rTSA experiencing clinical improvement, as quantified by four ROM measurements, varies with followup time, where the majority of improvement occurs in the first 12 months after surgery. Abd = abduction; FE = forward flexion; ER = external rotation.