Background: To facilitate the interpretation of numerical patient-reported outcome measure (PROM) scales, concepts such as the patient acceptable symptom state (PASS) have been introduced. Currently, no PASS thresholds have been established for the Knee injury and Osteoarthritis Outcome Score (KOOS) after total knee arthroplasty. The aims of the current study were to define PASS thresholds for the KOOS subscales and several other generic and knee-specific PROMs at 1 and 3 years after total knee arthroplasty using data from an international, multicenter clinical outcome study of a modern, well-performing implant system. Methods: The study cohort consisted of 499 patients undergoing total knee arthroplasty from an international, multicenter study. At 1 and 3 years after a total knee arthroplasty, patients completed the KOOS, EuroQoL 5-dimension 3-level (EQ-5D-3L), EuroQol visual analog scale (EQ-VAS), and numerical rating scales (NRS) for knee-related pain and satisfaction. PASS thresholds were calculated at each follow-up interval using 3 anchor-based approaches, using patient-reported satisfaction as the anchor. Results: According to our satisfaction anchor, 302 (78.9%) of 383 responding patients were satisfied at 1 year, and 242 (80.4%) of 301 responding patients were satisfied at 3 years. PASS thresholds were 84.5 points at 1 year and 87.5 points at 3 years for KOOS pain, 80.5 points at 1 year and 84.0 points at 3 years for KOOS symptoms, 83.0 points at 1 year and 87.5 points at 3 years for KOOS activities of daily living, 66.0 points at 1 year and 66.0 points at 3 years for KOOS quality of life, 83.0 points at 1 year and 90.5 points at 3 years for EQ-VAS, 0.80 point at 1 year and 0.80 point at 3 years for EQ-5D, and 1.8 points at 1 year and 1.8 points at 3 years for NRS pain. Conclusions: The current study is the first, to our knowledge, to propose PASS thresholds for the KOOS subscales at 1 and 3 years after total knee arthroplasty and contributes to PASS literature on other common PROMs. These findings will provide a useful reference for future total knee arthroplasty outcome studies and will help to determine what patients consider to be satisfactory operations. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

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Aims The primary aim of this study was to compare the wear properties of vitamin E-diffused, highly crosslinked polyethylene (VEPE) and one formulation of moderately crosslinked and mechanically annealed ultra-high molecular weight polyethylene (ModXLPE) in patients five years after primary total hip arthroplasty (THA). The secondary aim was to assess the clinical results of patients treated with VEPE by evaluating patient-reported outcome measures (PROMs), radiological evidence of fixation, and the incidence of mechanical failure. Patients and Methods A total of 208 patients (221 THAs) from four international centres were recruited into a prospective study involving radiostereometric analysis (RSA) and the assessment of clinical outcomes. A total of 193 hips (87%) were reviewed at the five-year follow-up. Of these, 136 (70%) received VEPE (vs ModXLPE) liners and 68 (35%) received ceramic (vs metal) femoral heads. PROMs and radiographs were collected preoperatively and at one, two, and five years postoperatively. In addition, RSA images were collected to measure PE wear postoperatively and at one, two, and five years after surgery. Results We observed similar bedding in one year postoperatively and wear two years postoperatively between the two types of liner. However, there was significantly more penetration of the femoral head in the ModXLPE cohort compared with the VEPE cohort five years postoperatively (p < 0.001). The only variables independently predictive of increased wear were ModXLPE (vs VEPE) liner type (β = 0.22, p = 0.010) and metal (vs ceramic) femoral head (β = 0.21, p = 0.013). There was no association between increased wear and the development of radiolucency (p = 0.866) or PROMs. No patient had evidence of osteolysis. Conclusion Five years postoperatively, patients with VEPE (vs ModXLPE) and ceramic (vs metal) femoral heads had decreased wear. The rates of wear for both liners were very low and have not led to any osteolysis or implant failure due to aseptic loosening.

Background 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. Questions/purposes (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? Methods 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. Results At 1 year after TKA, 32% of the patients (145 of 449) did not reach the PASS in KOOS Pain, 31% (139 of 449) did not reach the PASS in KOOS ADL, and 25% (110 of 449) 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. Conclusions 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. Level of Evidence Level III, therapeutic study.