Readmission Within 90 Days After Primary THA Is Associated With Decreased Improvement in 1-Year Patient-reported Outcome Measures and Increased Reoperation Rates

BACKGROUND: Readmissions after THA can negatively impact patients, increase healthcare utilization, and subsequently increase costs. However, there is little to demonstrate whether readmission after THA is associated with poorer results in outcomes that matter to patients, such as pain relief, restoration of function, or activities of daily living. Moreover, the impact of medical-related readmissions compared with orthopaedic-related readmissions on postoperative outcomes is currently unknown. QUESTIONS/PURPOSE: Are patients readmitted within 90 days of an index THA less likely to achieve a minimum clinically important difference (MCID) or patient acceptable symptom state (PASS) threshold in postoperative patient-reported outcome measures (PROMs) compared with those who are not readmitted? (2) Is the cause of readmission within 90 days (medical or orthopaedic) associated with a lower likelihood of achieving either MCID or PASS thresholds 1 year after THA? (3) How does 90-day readmission compare with other patient-specific factors associated with a lower likelihood of attaining either MCID or PASS? (4) Are patients readmitted within 90 days more likely to undergo further surgery? METHODS: Between January 2016 and December 2020, we treated 11,026 patients with primary THA at a large tertiary academic center. Patients undergoing nonelective (n = 551) and bilateral THAs (n = 1582) were excluded, leaving 8893 for final analysis here. Of these, 2476 patients were lost to follow-up and thus not included in the 1-year PROMs analysis, but they remained included in the study overall. Data for each patient were extracted from a validated longitudinally maintained institutional database. The mean ± SD age of patients was 65 ± 11.5 years, 57% were women, and 86% self-reported as White. Readmissions were individually reviewed and grouped into medical-related or orthopaedic-related causes based on the primary cause. Multivariable logistic regression models were used to investigate the association of 90-day readmission with 1-year PROMs. Overall, 6% (502 of 8893) were readmitted within 90 days, with 75% (377 of 502) being medically related and 25% (125 of 502) being orthopaedically related readmissions. PROM scores were obtained preoperatively and at 1 year after each of the THAs and included Hip Disability and Osteoarthritis Outcome Score (HOOS) pain, physical function, and joint replacement scores, as well as the Veterans Rand 12-Item Health Survey mental component summary score. Each was scored from 0 to 100, with higher scores representing better patient-perceived outcomes. Anchor-based MCID (HOOS pain 33, HOOS physical function 34, and HOOS joint replacement 18) and PASS thresholds (HOOS pain 80.6, HOOS physical function 83.6, and HOOS joint replacement 76.8) were utilized. RESULTS: Patients readmitted within 90 days of an index THA were less likely to achieve the MCID in HOOS joint replacement (OR 1.5 95% confidence interval (CI) 1.1 to 2.06; p = 0.01). Similarly, compared with patients who were not readmitted, readmitted patients were less likely to achieve PASS thresholds in HOOS pain (OR 1.37 95% CI 1.07 to 1.77; p = 0.01) and HOOS joint replacement (OR 1.4 95% CI 1.05 to 1.92; p = 0.02). Patients readmitted for orthopaedic causes compared with those not readmitted were less likely to achieve the MCID in HOOS joint replacement (OR 2.59 95% CI 1.56 to 4.31; p < 0.001) and the PASS threshold in HOOS pain (OR 1.79 95% 1.12 to 2.86; p = 0.02) and HOOS joint replacement (1.76 95% CI 1.06 to 2.93; p = 0.03) at 1 year. However, patients readmitted for medical causes, compared with patients who were not readmitted, were not less likely to achieve MCID or PASS thresholds in any of the HOOS subscales. The 90-day readmission (Akaike information criterion AIC increase 14.1) was the sixth most important variable influencing the likelihood of not achieving the MCID in HOOS joint replacement, following PROM phenotype (AIC 265), opioid use (Narx score), smoking, insurance, and race. Similarly, 90-day readmission ranked as the seventh and sixth most important variable for not achieving PASS thresholds in HOOS pain (AIC increase 7.5) and HOOS joint replacement (AIC increase 8.3), respectively. Patients readmitted within 90 days were more likely to undergo further surgery compared with those who were not readmitted (20.3% versus 0.04%; p < 0.001). CONCLUSION: Although medical-related readmissions are more frequent after THA, patients readmitted for orthopaedic causes are less likely to perceive meaningful improvements in pain relief and hip function at 1 year. Surgeons can reassure patients readmitted for medical reasons that their long-term symptom relief and functional recovery remain achievable. These findings highlight the importance of specifically identifying patients at higher risk of orthopaedic-related readmissions and implementing personalized preoperative optimization strategies tailored to their specific risk factors to reduce the chance of complications that may lead to readmission. Future studies should focus on identifying optimal management strategies for readmitted patients to ensure that they continue to perceive substantial benefits in their hip symptoms and function after surgery. LEVEL OF EVIDENCE: Level III, therapeutic study.