The Minimal Clinically Important Differences of the Simple Shoulder Test Are Different for Different Arthroplasty Types
These authors point out that the benefit to the patient of an arthroplasty is determined from preoperative and postoperative patient self-reported measures of comfort and function.
The minimal clinically important difference (MCID) for patient reported outcomes, such as the Simple Shoulder Test (SST), is often used to document the amount of improvement that is of importance to the patient; however, the MCID may differ for different types of shoulder arthroplasty.
There are two ways the preoperative and postoperative measures of comfort and function can be used to evaluate the outcome of a procedure:
(1) the final value for comfort and function
(2) the amount change: postoperative value minus preoperative value
(3) the percent of maximum possible improvement (%MPI): the maximum possible improvement (MPI) is the difference between a perfect value and the preoperative value. the percent of maximum possible improvement (%MPI) is the amount of improvement (postoperative value minus preoperative value) divided by the the maximum possible improvement (MPI).
While it is most common to compare the amount of change to a value for the minimal clinically important difference, the issue is that it possible for a patient to improve by the MCID but still have a shoulder with severely limited comfort and function (for example, an improvement from a Simple Shoulder Test (SST) value of 1 to 4).
On the other hand, %MPI reflects how much of the possible improvement was realized. For the SST the perfect score is 11. An improvement in SST value from 1 to 4 would give a %MPI of only 28%: the improvement was only 3 whereas the possible improvement was 11: (4-1)/(12-1).
The objective of this study was to report the MCID of the Simple Shoulder Test (SST) and the MCID of the percentage of maximal possible improvement (%MPI) for five different arthroplasty types: 368 patients undergoing anatomic total shoulder arthroplasty (aTSA), 330 patients undergoing ream-and-run arthroplasty (R&R), 80 patients undergoing reverse total shoulder arthroplasty (rTSA), 53 patients undergoing cuff tear arthropathy arthroplasty (CTAA), and 56 patients undergoing hemiarthroplasty (HA).
Significant improvements in SST values were seen for all arthroplasty types.
The MCID for SST change was 2.3 overall but ranged from 1.6 for aTSA to 3.7 for rTSA.
The MCID for %MPI was 32% overall but ranged from 22% for aTSA to 42% for hemiarthroplasty.
The pre and postoperative scores for the different procedures are shown below.
The proportion of patients meeting the MCIDs are shown below
Comment: This study indicates that the threshold for clinically significant improvement after arthroplasty are not the same for different arthroplasty types. Surgeons should apply the appropriate threshold to the type of arthroplasty being evaluated.
See this related article:
Substantial Inconsistency and Variability Exists Among Minimum Clinically Important Differences for Shoulder Arthroplasty Outcomes: A Systematic Review
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Here are some videos that are of shoulder interest
Shoulder arthritis - what you need to know (see this link). How to x-ray the shoulder (see this link). The ream and run procedure (see this link). The total shoulder arthroplasty (see this link). The cuff tear arthropathy arthroplasty (see this link). The reverse total shoulder arthroplasty (see this link). The smooth and move procedure for irreparable rotator cuff tears (see this link). Shoulder rehabilitation exercises (see this link).
