Although TKA is a common and proven reliable procedure for treating end-stage knee osteoarthritis, a minority of patients still do not achieve satisfactory levels of pain relief and functional improvement. Even though several studies have attempted to identify patients at risk of having poor clinical outcomes, few have approached this issue by considering the outcome of the patient-acceptable symptom state (PASS), defined as the value on a patient-reported outcome measure scale above which the patient deems their current symptom state acceptable.
(1) What is the proportion of patients who do not attain the PASS in pain and function at 1 year after TKA? (2) Which preoperative patient factors are associated with not achieving the PASS in pain at 1 year after TKA? (3) Which preoperative patient factors are associated with not achieving the PASS in function at 1 year after TKA?
This retrospective study is a secondary analysis of the 1-year follow-up data from a prospective, international, multicenter study of a single TKA system. Inclusion criteria for that study were patients diagnosed with primary osteoarthritis or post-traumatic arthritis and who were able to return for follow-up for 10 years; exclusion criteria were infection, osteomyelitis, and failure of a previous joint replacement. Between 2011 and 2014, 449 patients underwent TKA at 10 centers in five countries. At 1 year, 13% (58 of 449) were lost to follow-up, 2% could not be analyzed (eight of 449; missing 1-year KOOS), leaving 85% (383 of 449) for analysis here. The primary outcomes were not surpassing evidence-derived PASS thresholds in the Knee Injury and Osteoarthritis Outcome Score (KOOS) Pain and Activities in Daily Living (ADL) sub-scores. Multivariate binary logistic regressions considering preoperative demographic, radiographic, and patient-reported outcome measure data were constructed using a forward stepwise elimination algorithm to reach the simplest best-fit regression models.
At 1 year after TKA, 38% of the patients (145 of 383) did not reach the PASS in KOOS Pain, 36% (139 of 383) did not reach the PASS in KOOS ADL, and 29% (110 of 383) did not achieve the PASS in either KOOS Pain or ADL. After controlling for potentially confounding variables such as gender, age, BMI, and comorbidity scores, we found that men (odds ratio 2.09; p = 0.01), and patients with less-than-advanced radiographic osteoarthritis (OR 2.09; p = 0.01) were strongly associated with not achieving the PASS in pain. After controlling for the same potentially confounding variables, we found that patients with less-than-advanced radiographic osteoarthritis (OR 2.09; p = 0.01) were also strongly associated with not achieving the PASS in function.
Level III, therapeutic study.
We found that patients with less severe osteoarthritis were much less likely to attain the PASS in pain and function at 1 year after TKA, and that men were much less likely to achieve the PASS in pain at 1 year after TKA. Based on these findings, surgeons should strongly consider delaying surgery in patients who present with less-than-severe osteoarthritis, with increased caution in men. Surgeons should counsel their patients on their expectations and their chances of achieving meaningful levels of pain and functional improvement. Future regional and national registry studies should assess the true proportion of patients attaining PASS in pain and function after TKA and confirm if the preoperative factors identified in this study remain significant in larger, more diverse patient populations.