John Charnley Award: Preoperative Patient-reported Outcome Measures Predict Clinically Meaningful Improvement in Function After THA

Abstract

Background: Despite the overall effectiveness of total hip arthroplasty (THA), a subset of patients remain dissatisfied with their results because of persistent pain or functional limitations. It is therefore important to develop predictive tools capable of identifying patients at risk for poor outcomes before surgery.

Questions/purposes: The purpose of this study was to use preoperative patient-reported outcome measure (PROM) scores to predict which patients undergoing THA are most likely to experience a clinically meaningful change in functional outcome 1 year after surgery.

Methods: A retrospective cohort study design was used to evaluate preoperative and 1-year postoperative SF-12 version 2 (SF12v2) and Hip Disability and Osteoarthritis Outcome Score (HOOS) scores from 537 selected patients who underwent primary unilateral THA. Minimum clinically important differences (MCIDs) were calculated using a distribution-based method. A receiver operating characteristic analysis was used to calculate threshold values, defined as the levels at which substantial changes occurred, and their predictive ability. MCID values for HOOS and SF12v2 physical component summary (PCS) scores were calculated to be 9.1 and 4.6, respectively. We analyzed the effect of SF12v2 mental component summary (MCS) scores, which measure mental and emotional health, on SF12v2 PCS and HOOS threshold values.

Results: Threshold values for preoperative HOOS and PCS scores were a maximum of 51.0 (area under the curve [AUC], 0.74; p < 0.001) and 32.5 (AUC, 0.62; p < 0.001), respectively. As preoperative mental and emotional health improved, which was reflected by a higher MCS score, HOOS and PCS threshold values also increased. When preoperative mental and emotional health were taken into account, both HOOS and PCS threshold values' predictive ability improved (AUCs increased to 0.77 and 0.69, respectively).

Conclusions: We identified PROM threshold values that predict clinically meaningful improvements in functional outcome after THA. Patients with a higher level of preoperative function, as suggested by HOOS or PCS scores above the defined threshold values, are less likely to obtain meaningful improvement after THA. Lower preoperative mental and emotional health decreases the likelihood of achieving a clinically meaningful improvement in function after THA. The results of this study may be used to facilitate discussion between physicians and patients regarding the expected benefit after THA and to support the development of patient-based informed decision-making tools. For example, despite significant disease, patients with high preoperative function, as measured by PROM scores, may choose to delay surgery given the low likelihood of experiencing a meaningful improvement postoperatively. Similarly, patients with notably low MCS scores might best be counseled to address mental health issues before embarking on surgery.

Level of evidence: Level III, prognostic study.

Fig. 1A–B

The calculated threshold values, indicated by the dotted vertical lines, do not represent true cutoffs but instead serve to represent points after which a patient’s likelihood of experiencing a clinically meaningful improvement in function begins to more rapidly diminish. (A) The SF12v2 PCS threshold value of 32.5 was not acceptably predictive of a patient’s likelihood of experiencing a clinically meaningful improvement in outcome as measured by the 1-year postoperative SF12v2 PCS score (AUC 0.62). (B) The HOOS threshold value of 51 was acceptably predictive of a patient’s likelihood of experiencing a clinically meaningful improvement in outcome as measured by the 1-year postoperative HOOS score (AUC 0.74).

Fig. 2A–B

SF12v2 PCS and HOOS threshold values (represented by dashed lines) are dependent on preoperative MCS score and demonstrate a linear relationship. Postoperative data are plotted in a binned fashion, which demonstrates the likelihood of attaining a MCID across different preoperative PROM score combinations. Hexagonal cells are labeled and shaded according to the proportion of patients within that cell who obtained the MCID (absolute number of patients in parentheses). By situating patients within a specific bin, one is able to visualize an approximate likelihood of obtaining a MCID based on preoperative PROM scores in the context of calculated threshold values. (A) After adjusting for preoperative mental and emotional health, SF12v2 PCS threshold values demonstrated an improved predictive ability (AUC 0.69), yet remained below the acceptably predictive value of 0.70. (B) The predictive ability of HOOS threshold values improved from 0.74 to 0.77 after adjusting for preoperative mental and emotional health.