These authors sought to determine the time-dependent achievement of the minimal clinically important difference (MCID), substantial clinical benefit (SCB), and patient acceptable symptomatic state (PASS) in patients undergoing either anatomic total shoulder (TSA, n=157) or reverse total shoulder arthroplasty (RTSA, n=81) and compare the results of the two populations. They also sought to identify variables associated with earlier or delayed achievement of each CSO.
The RTSA cohort was older (70.2±7.5 vs 61.0±8.4,P<0.001), had a lower BMI (28.8±5.9 vs 31.5±6.5, P=0.006), and a greater proportion 25 of females (53.1% vs 32.9%, P=0.017) relative to TSA.
For SCB, there was a significant difference in the cumulative percentage of TSA and RTSA patients reaching this threshold at both the 6-month (77.3% vs 59.0%, P=0.024) and 2-year (92.0% vs 79.5%, P=0.048) time periods, with similar findings demonstrated for PASS.
There was a significant difference in the average time required to achieve the PASS (TSA: 6.1 months vs rTSA: 11.6 months, P=0.009), but not the MCID (P=0.407) or SCB (P=0.153).
In the TSA group, the presence of diabetes, higher preoperative outcome scores, longer duration of symptoms, as well as prior non-arthroplasty surgery were associated with delayed achievement of CSOs, while higher preoperative activity level was associated with accelerated achievement.
In the RTSA group, a delay in achieving CSOs was similarly associated with the presence of diabetes, higher preoperative outcome scores and additionally with a diagnosis of rotator cuff arthropathy. Male sex, older age at time of surgery and the clinical indication of a rotator cuff tear without arthritis were associated with earlier achievement of CSOs.
Comment: The question is whether this study compares two different types of arthroplasty or different patients. As shown in the tables above, the two arthroplasty groups differed with respect to age, sex, BMI, preoperative symptom duration, prior shoulder surgery, diagnosis, preoperative exercise, and preoperative ASES scores.
An informative approach would be to include these factors as well as the type of arthroplasty in a multivariate analysis with time to achieve CSO as the primary outcome variable.
