Background
Patients who undergo a second THA at least 1 year after the first one may experience different recovery courses after each THA. It is unknown what the clinically relevant improvements and healthcare utilization are after each THA in patients undergoing contralateral THA > 1 year apart.
Questions/purposes
(1) Do patient-reported outcome measures (PROMs) differ at baseline and 1 year after THA for the first and second hip arthroplasty? (2) Does the likelihood of achieving minimum clinically important difference (MCID) and patient acceptable symptom state (PASS) thresholds differ for the first and second hip arthroplasty? (3) Does utilization of healthcare within 90 days of THA, using discharge disposition, length of stay (LOS), and 90-day readmission risk as proxies, differ between the first and second hip arthroplasty?
Methods
Between January 2016 and December 2021, a total of 14,023 primary THAs for hip osteoarthritis were performed at a large tertiary academic center, and data from each were longitudinally maintained in an institutional database. In this retrospective study, we excluded nonelective (n = 265), simultaneous bilateral (n = 89), staged bilateral < 1 year apart (n = 1856), unilateral THAs (n = 7541), and those who were lost prior to the minimum study follow-up of 1 year or had incomplete data sets (n =3618), leaving 654 contralateral THAs > 1 year apart (327 patients) for analysis here. The median (range) patient age was 64 years (26 to 88) at the time of the first THA and 66 years (27 to 88) at the second THA. The mean (IQR) time from first THA to second THA was 696 days (488 to 1008). In all, 62% (204 of 327) of patients were women, and 89% (286 of 321) were White. The median (range) BMI was 29 kg/m2 (first THA 16 to 60, second THA 18 to 56) at both THAs. PROMs were obtained preoperatively and at 1 year after each of the THAs and included Hip Disability and Osteoarthritis Outcome Score pain (HOOS-pain), physical function (HOOS-PS), and joint replacement (HOOS-JR) 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. A distribution-based method was used to calculate the MCID thresholds (HOOS-pain 8.35, HOOS-PS 9.47, and HOOS-JR 7.76), while an anchor-based method was utilized for the PASS thresholds (HOOS-pain 80.6, HOOS-PS 83.6, and HOOS-JR 83.6). Healthcare utilization outcomes included discharge disposition, LOS, and 90-day readmission rates.
Results
Patients had slightly lower baseline PROM scores in all HOOS subdomains before the first THA compared with the second THA (median HOOS-pain 38 versus 42, p < 0.001; HOOS-PS 54 versus 58, p < 0.001; HOOS-JR 43 versus 47, p < 0.001). The difference between baseline and 1-year postoperative scores was slightly larger in all HOOS subdomains after the first THA (median HOOS-pain difference 52 versus 50, p < 0.001; HOOS-PS difference 38 versus 31, p < 0.001; HOOS-JR difference 42 versus 39, p < 0.001). There was no difference in the percentage of patients achieving the MCID in HOOS-pain (97% versus 97%; p = 0.93), HOOS-PS (92% versus 88%; p = 0.17), and HOOS-JR (96% versus 94%; p = 0.18) between the first and second THAs. Although there was also no difference in the percentage of patients achieving PASS thresholds in HOOS-pain (81% versus 77%; p = 0.11), HOOS-PS (82% versus 79%; p = 0.055), and HOOS-JR (71% versus 71%; p = 0.39) between the first and second THAs, considerably fewer patients were reaching the PASS threshold in both THAs. After the second THA, slightly more patients were discharged home (95% versus 91%; p = 0.03) and had a very slightly shorter LOS (1.28 versus 1.35 days; p < 0.001). There was no difference in 90-day readmission rates between the first and second THA (4% versus 5%; p = 0.84).
Conclusion
In patients undergoing contralateral THA > 1 year apart, baseline PROMs were slightly worse before the first THA, and improvements were slightly greater compared with the second THA, although these differences were likely not clinically significant. Clinically meaningful improvements, based on MCID and PASS thresholds, were similar at 1 year for both THAs, yet 20% to 25% of patients reported inadequate pain relief after both surgeries. Healthcare utilization was also comparable between both procedures. Surgeons can use these findings to counsel patients on the likely similar outcomes following both their THAs. Future studies should explore factors contributing to inadequate pain relief and identify strategies to improve patient outcomes after both THAs.
Level of Evidence Level III, therapeutic study.
