Monday, April 4, 2016

Shoulder joint replacement outcomes, how to communicate with prospective patients.

Preoperative patient-reported scores can predict postoperative outcomes after shoulder arthroplasty

These authors collected preoperative and 1-year postoperative 12-Item Short Form Health Survey (SF-12) Physical Component Summary (PCS) and Mental Component Summary (MCS) scores and American Shoulder and Elbow Surgeons (ASES) pain and function scores from 107 patients who underwent total or reverse shoulder arthroplasty.

They defined the minimum clinically important difference (MCID) as half the standard deviation of the change in score from the preoperative to the postoperative time point for each specific measure for their patient population.

For all shoulder arthroplasty patients, the MCIDs were 6.5 for ASES function, 8.0 for ASES pain, 5.4 for SF-12 PCS, and 5.7 for SF-12 MCS. The percentages of patients who attained improvement greater than the MCID were as follows: ASES function, 82%; ASES pain, 76%; SF-12 PCS, 63%;
and SF-12 MCS, 25%.

Threshold values below which patients were more likely to achieve MCID were 12 for ASES function, 25 for ASES pain, 46 for SF-12 PCS, and 42 for SF-12 MCS.

Patients with higher preoperative SF-12 MCS scores had a higher likelihood of achieving MCID for each measure.

The authors suggested that their results can be used to facilitate shared decision-making and to forecast expected benefits after shoulder arthroplasty.

Comment: These authors have conducted a very sophisticated study of 107 of their patients. After reading this paper, we need to step back and ask "What information is useful to patients in shared decision-making? " Many patients would find it difficult to grasp the meaning of an MCID or of 6.5 points on an ASES scale or that if the preoperative ASES function score is below 12, the shoulder is more likely to improve by an MCID of 6.5.

Let's look at some other ways to present the data from this study to a patient. Below we can see the preop and one year post op ASES function scores for five quintiles.

Estimating the values from this graph we come up with the following spreadsheet.

Here are some concepts that may be easier for prospective patients to grasp. For this series of patients (1) on average, patients experienced improved function irrespective of the amount of function they had before surgery (2) the more function patients have before surgery, the more function they are likely to have at one year after surgery (3) the absolute amount of improvement in shoulder function is least for shoulders that start out with the worst function. (4) The percent of the maximum possible improvement ((one year - preop)/(50 - preop)) achieved is greatest for shoulders that start out with a high level of function.
Expressed in this way, the concept of MCID is not necessary for the discussion.

By the way, most commonly,  MCID is used to signify the smallest difference that patients find meaningful. This is accomplished by comparing the metric of interest, for example the change in ASES pain score, to an independent assessment of their perception of change in their overall function, as shown in this example (rather than using half the standard deviation of the change in score from the preoperative to the postoperative time point as was used here). The latter method does not use comparison to an independent assessment and, since half the standard deviation of the change is likely to be patient-sample dependent, is less likely to be generalizable to other groups of patients

In summary, we need to answer the question that patients ask, "how much of the use of my arm am I likely to get back". One way to do that is to share with them the factors that correlate with the amount of improvement expected as a percent of the maximum possible improvement.

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