Interpretation threshold values for the Oxford Knee Score in patients undergoing unicompartmental knee arthroplasty

Previous arthroscopy does not decrease survivorship or functional outcomes for unicompartmental knee arthroplasty patients

INTRODUCTION

Arthroscopic procedures for osteoarthritis (OA), in particular arthroscopic meniscectomy, have poorer long-term clinical outcomes compared to those managed non-operatively. In addition, previous arthroscopy is associated with worse outcomes following subsequent total knee arthroplasty (TKA), however there is limited data on the impact on subsequent unicompartmental knee arthroplasty (UKA) outcomes. The aim of the study is to investigate whether patients who had arthroscopy prior to UKA have differences in survivorship or functional outcomes compared to those with no prior arthroscopy.

METHODS

All patients who received either a primary medial or lateral UKA at four large tertiary hospitals were included (n = 2,272). Patient data (age, sex, ethnicity, body mass index (BMI), American Society of Anesthesiologists (ASA) status and surgical data) was recorded following systematic review of all clinical notes and radiographs. Differences between survival curves were analysed using log-rank curves. Differences between categorical data was compared using Fisher's exact or Chi-squared tests, and differences between continuous variables were compared using t-tests.

RESULTS

There was no difference between the survival curves for UKA patients with previous arthroscopy compared to those with no previous arthroscopy (10 years: 91% UKA with previous arthroscopy vs. 92% no previous arthroscopy; 15 years: 78% previous arthroscopy vs. 86% no previous arthroscopy; p = 0.50). Oxford Knee Score (OKS) was comparable between patients who had previous arthroscopy and those who had no previous arthroscopy at 6 months (38.8 vs. 39.3, p = 0.45), 5 years (42.0 vs. 40.4, p = 0.11) and 10 years (40.8 vs. 40.2, p = 0.71).

DISCUSSION

In this large patient cohort with comprehensive review of clinical data and outcomes, we found that prior arthroscopy did not affect survivorship or functional outcomes of UKA patients.

Starting Up a Lateral Unicompartmental Knee Arthroplasty Practice - Is Outcome Affected?

INTRODUCTION

In the past, the utilization of lateral unicompartmental knee arthroplasty (UKA) has been limited at national levels, despite the fact that an estimated 10% of patients who have an indication for arthroplasty, present with isolated lateral compartment osteoarthritis (OA). Units dedicated to UKA have reported good outcomes. Identifying patients for the procedure has been less clear, and the procedure has been perceived to be technically more demanding than medial UKA. This may result in a reluctance to start a lateral UKA practice and challenge the early phase. Therefore, this paper aimed to present the outcomes and learning curve when starting up a lateral UKA practice, as this theme remains unelucidated.

METHODS

There were 85 primary fixed-bearing lateral UKAs, with a minimum of 1-year follow-up, performed between 2016 and 2022 by two arthroplasty surgeons with existing UKA practices. The indications were primary (n = 79) or post-traumatic (n = 6) osteoarthritis. Patient-reported outcome measures (PROMs) were assessed at 3, 12, and 24 months. A cumulative sum (CUSUM) analysis was used to evaluate surgical duration and the 12-month Oxford Knee Score (OKS).

RESULTS

Median (Interquartile range (IQR)) 12-month OKS, Activity and Participation Questionnaire (APQ), and Forgotten Joint Score (FJS) were 43 (37.5 to 46), 78 (42.5 to 98.5), and 72 (55 to 90), respectively. The OKS outcomes did not reveal adverse effects from the learning curve. A performance shift in surgical duration was observed around case 33. Kaplan-Meier implant survival reached 95.4% at 7 years for the endpoint "implant revision," and 93.5% for "implant revision/implant addition."

CONCLUSION

Starting up a lateral UKA practice is safe and efficient for surgeons who have prior medial UKA experience, provided strict adherence to indications. While surgical duration indicated a learning curve over approximately 33 cases, PROMs remained stable, suggesting proficient outcomes irrespective of the learning curve.

Patient acceptable symptom state and treatment failure threshold values for work productivity and activity Impairment and EQ-5D-5L in osteoarthritis

OBJECTIVE

To estimate patient acceptable symptom state (PASS) and treatment failure (TF) threshold values for Work Productivity and Activity Impairment (WPAI) measure and EQ-5D-5L among people with hip or knee osteoarthritis (OA) 3 and 12 months following participation in a digital self-management intervention (Joint Academy®).

METHODS

Among the participants, we computed work and activity impairments scores (both 0-100, with a higher value reflecting higher impairment) and the Swedish hypothetical- (range: - 0.314 to 1) and experience-based (range: 0.243-0.976) EQ-5D-5L index scores (a higher score indicates better health status) at 3- (n = 14,607) and 12-month (n = 2707) follow-ups. Threshold values for PASS and TF were calculated using anchor-based adjusted predictive modeling. We also explored the baseline dependency of threshold values according to pain severity at baseline.

RESULTS

Around 42.0% and 48.3% of the participants rated their current state as acceptable, while 4.2% and 2.8% considered the treatment had failed at 3 and 12 months, respectively. The 3-month PASS/TF thresholds were 16/29 (work impairment), 26/50 (activity impairment), 0.92/0.77 (hypothetical EQ-5D-5L), and 0.87/0.77 (the experience-based EQ-5D-5L). The thresholds at 12 months were generally comparable to those estimated at 3 months. There were baseline dependencies in PASS/TF thresholds with participants with more severe baseline pain considering poorer (more severe) level of WPAI/EQ-5D-5L as satisfactory.

CONCLUSION

PASS and TF threshold values for WPAI and EQ-5D-5L might be useful for meaningful interpretation of these measures among people with OA. The observed baseline dependency of estimated thresholds limits their generalizability and values should be applied with great caution in other settings/populations.

Minimal important change thresholds change over time after knee and hip arthroplasty

OBJECTIVES

The minimal important change (MIC) reflects what patients, on average, consider the smallest improvement in a score that is important to them. MIC thresholds may vary across patient populations, interventions used, posttreatment time points and derivation methods. We determine and compare MIC thresholds for the Oxford Knee Score and Oxford Hip Score (OKS/OHS) at 3 months postoperatively to 12- and 24-month thresholds in patients undergoing knee or hip arthroplasty.

STUDY DESIGN AND SETTING

This cohort study used data from patients undergoing total knee arthroplasty (TKA), unicompartmental knee arthroplasty (UKA), or total hip arthroplasty (THA) at a public hospital between February 2016 and February 2023. At 3, 12, and 24 months postoperatively, patients responded to the OKS/OHS and a 7-point anchor question determining experienced changes in knee or hip pain and functional limitations. We used the adjusted predictive modeling method that accounts for the proportion improved and the reliability of the anchor question to determine MIC thresholds and their mean differences between time points.

RESULTS

Complete data were obtained from 695/957 (73%), 1179/1703 (69%), and 1080/1607 (67%) patients undergoing TKA, 474/610 (78%), 438/603 (73%), and 355/507 (70%) patients undergoing UKA, and 965/1315 (73%), 978/1409 (69%), and 1059/1536 (69%) patients undergoing THA at 3, 12, and 24 months, respectively. The median age ranged from 68 to 70 years and 55% to 60% were females. The proportions improved ranged between 83% and 95%. The OKS/OHS MIC thresholds were 0.1, 4.2, and 5.1 for TKA, 1.8, 5.6, and 3.4 for UKA, and 1.3, 6.1, and 6.0 for THA at 3, 12, and 24 months postoperatively, respectively. The reliability ranged between 0.64 and 0.82, and the MIC values increased between three and 12 months but not between 12 and 24 months.

CONCLUSION

Any absence of deterioration in pain and function is considered important at 3 months after knee or hip arthroplasty. Increasing thresholds over time suggest patients raise their standards for what constitutes a minimal important improvement over the first postoperative year. Besides improving our understanding of patients' views on postoperative outcomes, these clinical thresholds may aid in interpreting registry-based treatment outcome evaluations.

Establishing patient-centered metrics for the knee injury and osteoarthritis outcome score following medial unicompartmental knee arthropalsty

BACKGROUND

This study aimed to determine the minimal clinically important difference (MCID) and the patient acceptable symptoms state (PASS) threshold for the knee injury and osteoarthritis outcome score (KOOS) pain subscore, KOOS physical short form (PS), and KOOS joint replacement (JR) following medial unicompartmental knee arthroplasty (mUKA).

METHODS

Prospectively collected data from 743 patients undergoing mUKA from a single academic institution from April 2015 through March 2020 were analyzed. Patient-reported outcome measures (PROMs) were collected both pre-operatively and 1-year post-operatively. Distribution-based and anchored-based approaches were used to estimate MCIDs and PASS, respectively. The optimal cut-off point and the percentage of patients who achieved PASS were also calculated.

RESULTS

MCID for KOOS-pain, KOOS-PS, and KOOS-JR following mUKA were calculated to be 7.6, 7.3, and 6.2, respectively. The PASS threshold for KOOS pain, PS, and JR were 77.8, 70.3, and 70.7, with 68%, 66%, and 64% of patients achieving satisfactory outcomes, respectively. Cut-off values for delta KOOS pain, PS, and JR were found to be 25.7, 14.3, and 20.7 with 73%, 69%, and 68% of patients achieving satisfactory outcomes, respectively.

CONCLUSION

The current study identified useful values for the MCID and PASS thresholds at 1 year following medial UKA of KOOS pain, KOOS PS, and KOOS JR scores. These values may be used as targets for surgeons when evaluating PROMS using KOOS to determine whether patients have achieved successful outcomes after their surgical intervention. Potential uses include the integration of these values into predictive models to enhance shared decision-making and guide more informed decisions to optimize patient outcomes.

LEVEL OF EVIDENCE

III.

Verification of the minimal clinically important difference of the Capabilities of Upper Extremity Test in patients with subacute spinal cord injury

CONTEXT

The number of patients with cervical spinal cord injury (CSCI) is increasing, and the Capabilities of Upper Extremity Test (CUE-T) is recommended for introduction in clinical trials. We calculated the minimal clinically important difference (MCID) of the CUE-T using an adjustment model with an interval of 1 month.

DESIGN

This was a prospective study.

SETTING

This study was conducted with participants from the Chiba Rehabilitation Center in Japan.

PARTICIPANTS

The participants were patients with subacute CSCI.

INTERVENTIONS

The CUE-T and spinal cord independence measure (SCIM) III were performed twice within an interval of 1 month.

OUTCOME MEASURES

The MCID was calculated using an adjustment model based on logistic regression analysis. The participants were classified into an improvement group and a non-improvement group based on the amount of change in the two evaluations using the 10-point SCIM III MCID as an anchor.

RESULTS

There were 52 participants (56.8 ± 13.5 years old, 45 men/7 women) with complete or incomplete CSCI: 18 in the improvement group and 34 in the non-improvement group. A significant regression equation was obtained when calculating the MCID, and the total, hand, and side scores were 7.7, 2.0, and 3.7 points, respectively.

CONCLUSION

The calculated MCID of the CUE-T in this study was 7.7 points. The results of this study provide useful criteria for implementation in clinical trials. Future studies should use patient-reported outcomes, a more recommended anchor, and calculate the MCID using methods such as the patient's condition.

A decreased tibial tuberosity-trochlear groove distance is associated with lateral patellofemoral joint degeneration after implantation of medial fixed-bearing unicompartmental knee arthroplasty - a minimum five year follow-up

PURPOSE

The influence of lateral patellofemoral osteoarthritis (PFOA) in medial unicompartmental knee arthroplasty (UKA) is controversial. Our aim was to identify radiographic factors that may lead to progressive PFOA after implantation of a fixed-bearing medial UKA and their impact on patient-reported outcomes (PROMs).

METHODS

A retrospective consecutive cohort of patients undergoing medial UKA with a minimum follow-up of 60 months between September 2011 and January 2017 was identified. All UKAs had a fixed-bearing design with cemented femoral and tibial components. PROMs included documentation of the Oxford Knee Score (OKS). The following radiographic parameters were evaluated on conventional radiographs and computer tomography (CT) scans: patella tilt angle, patella congruence angle, Caton-Deschamps index, medial and lateral patellofemoral degeneration (Kellgren-Lawrence Classification (KL)), mechanical anteroposterior axis, femoral torsion, tibial tuberosity to trochlear groove distance (TTTG), anteroposterior translation of the femoral component. A hierarchical multiple regression analysis and partial Pearson correlation analysis (SPSS) were used to evaluate for predictors of progression of lateral PFOA.

RESULTS

Forty-nine knees allowed PFOA assessment and had an average follow-up of 62 months (range 60-108). Twenty-three patients did not exhibit any progression of lateral PFOA. Twenty-two progressed with 1 stage, whereas four had progressed 2 stages according to the KL classification. TTTG negatively correlated with progressive lateral PFOA (r =  - 0.436, p = 0.01). Progression of lateral PFOA did not correlate with OKS at last follow-up (p = 0.613).

CONCLUSION

A decreased TTGT correlated with radiographic progression of lateral PFOA after medial fixed-bearing cemented UKA. PFOA however did not influence PROMs at a minimum of five years postoperatively.

Interpretation Threshold Values for the Oxford Hip Score in Patients Undergoing Total Hip Arthroplasty: Advancing Their Clinical Use

BACKGROUND

Patient-reported outcome measures such as the Oxford Hip Score (OHS) can capture patient-centered perspectives on outcomes after total hip arthroplasty (THA). The OHS assesses hip pain and functional limitations, but defining interpretation threshold values for the OHS is warranted so that numerical OHS values can be translated into whether patients have experienced clinically meaningful changes. Therefore, we determined the minimal important change (MIC), patient acceptable symptom state (PASS), and treatment failure (TF) threshold values for the OHS at 12 and 24-month follow-up in patients undergoing THA.

METHODS

This cohort study used data from patients undergoing THA at 1 public hospital between July 2016 and April 2021. At 12 and 24 months postoperatively, patients provided responses for the OHS and for 3 anchor questions about whether they had experienced changes in hip pain and function, whether they considered their symptom state to be satisfactory, and if it was not satisfactory, whether they considered the treatment to have failed. The anchor-based adjusted predictive modeling method was used to determine interpretation threshold values. Baseline dependency was evaluated using a new item-split method. Nonparametric bootstrapping was used to determine 95% confidence intervals (CIs).

RESULTS

Complete data were obtained for 706 (69%) of 1,027 and 728 (66%) of 1,101 patients at 12 and 24 months postoperatively, respectively. These patients had a median age of 70 years, and 55% to 56% were female. Adjusted OHS MIC values were 6.3 (CI, 4.6 to 8.1) and 5.2 (CI, 3.6 to 6.7), adjusted OHS PASS values were 30.6 (CI, 29.0 to 32.2) and 30.5 (CI, 29.3 to 31.8), and adjusted OHS TF values were 25.5 (CI, 22.9 to 27.7) and 27.0 (CI, 25.2 to 28.8) at 12 and 24 months postoperatively, respectively. MIC values were 5.4 (CI, 2.1 to 9.1) and 5.0 (CI, 1.9 to 8.7) higher at 12 and 24 months, respectively, in patients with a more severe preoperative state.

CONCLUSIONS

The established interpretation threshold values advance the interpretation and clinical use of the OHS, and may prove especially beneficial for registry-based evaluations of treatment quality.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.