Standing balance post total knee arthroplasty: sensitivity to change analysis from four to twelve weeks in 466 patients.

OBJECTIVE: Little is known about how static standing balance changes post total knee arthroplasty (TKA). The primary aim of this study was to examine the sensitivity to change and redundancy of center of pressure (COP) variables post-TKA. The secondary aim was to compare the sensitivity of these measures to standard clinical assessments of one repetition maximum knee extension strength and fast pace gait speed. DESIGN: 466 participants performed instrumented double-limb standing balance tests with eyes open at 4 and 12 weeks post-TKA. Measures of COP standard deviation, amplitude, root mean square (RMS), path length, detrended fluctuation analysis (DFA) and signal frequency content for the medial-lateral (ML) and anterior-posterior (AP) axes were examined. RESULTS: Significant decreases in total path length, ML variables related to sway velocity and AP signal complexity and frequency were observed. Inter-session Cohen's d effect size (ES) revealed the strongest effect was for high velocity ML path length, with a 12% decrease in this rapid sway. This variable, along with AP mean instantaneous frequency and AP DFA, were the only ones significantly different with effect sizes >0.20 and non-redundant (Spearman's rho <0.75). The ES of COP-derived variables (maximum = 0.45) were lower than gait speed (1.40) and knee extensor strength (1.54). CONCLUSION: Increased high velocity ML sway is present at four compared to 12 weeks post-TKA. This augmented rapid sway may provide increased challenges to the postural control system at a time coinciding with reduced strength levels, which could have implications for physical function during activities of daily living.

Association between rehabilitation attendance and physical function following discharge after total knee arthroplasty: prospective cohort study.

BACKGROUND: Rehabilitation is widely advocated and provided as a standard of care for patients with total knee arthroplasty (TKA) but its effects on intermediate- to longer-term physical function is unclear. Also unknown is the relationship between the number of rehabilitation sessions attended and functional outcomes. METHODS: We conducted a prospective cohort study of 1540 patients who had undergone TKA and were referred for rehabilitation. Physical function was indexed by the Short-Form 36 (SF-36) physical function score at 6 months post-TKA. We used multivariable linear regression to assess the association between rehabilitation attendance and Month-6 physical function. Among patients who attended rehabilitation, multivariable linear regression was used to examine the dose-response association between the number of sessions attended and Month-6 physical function. RESULTS: Of the 1540 patients, 68 patients did not attend rehabilitation, 86 patients attended one session, and 1386 patients attended two or more sessions. Adjusted for the propensity to attend rehabilitation, rehabilitation attendance was independently associated with better Month-6 SF-36 physical function (point estimate, 5.0 points; 95% CI, 0.5-9.5; P = 0.028 compared with patients with no rehabilitation). Among patients who attended rehabilitation, attending five sessions was associated with a 3.6-point increase in SF-36 scores (95% CI, 0.8-6.5; P = 0.01) relative to patients who attended one session. CONCLUSIONS: Rehabilitation attendance post-TKA is associated with an increase in self-report physical function. Among patients who attended rehabilitation, a modest dose-response relationship was observed between the number of sessions and functional outcomes.

Predicting discharge outcomes after total knee replacement using the Risk Assessment and Predictor Tool.

OBJECTIVE: To explore the use of the Risk Assessment and Predictor Tool (RAPT) as a pre-operative tool to predict postoperative discharge destination and length of stay for patients undergoing total knee replacement (TKR) in Singapore. PARTICIPANTS AND SETTING: A cohort of 569 patients undergoing primary TKR at the Singapore General Hospital were recruited prospectively from November 2009 to June 2010. INTERVENTION: All patients completed a modified RAPT questionnaire pre-operatively, and underwent standard clinical pathway guidelines for TKR throughout the study. MAIN OUTCOME MEASURES: Actual discharge destination (ADDest) and length of stay (LOS). DESIGN: Total RAPT score and preferred discharge destination (PDD) were recorded pre-operatively, while ADDest and LOS were obtained immediately after discharge. Multivariable logistic regression and multivariable regression analysis were used to determine whether the RAPT items and score could predict the discharge outcomes. RESULTS: Total RAPT score was a significant predictor of LOS for patients following TKR (R=0.24, P<0.001); the higher the RAPT score, the longer the LOS. Total RAPT score was also a significant predictor of actual discharge to home [odds ratio (OR) 2.32, 95% confidence interval (CI) 1.11 to 4.85]. PDD was a significant predictor for LOS (R=0.22, P<0.001) and ADDest (R=0.33, P<0.001). Patients who chose to be discharged home were more likely to be directly discharged home (OR 9.79, 95% CI 5.07 to 18.89, P<0.001). CONCLUSION: Total RAPT score and PDD were significant predictors of ADDest and LOS for patients following TKR in Singapore. The ability to predict discharge outcomes following TKR could assist caregivers, healthcare professionals and administrators in optimising care and resource allocations for patients.

A prediction model for length of stay after total and unicompartmental knee replacement.

Early and accurate prediction of hospital length-of-stay (LOS) in patients undergoing knee replacement is important for economic and operational reasons. Few studies have systematically developed a multivariable model to predict LOS. We performed a retrospective cohort study of 1609 patients aged ≥ 50 years who underwent elective, primary total or unicompartmental knee replacements. Pre-operative candidate predictors included patient demographics, knee function, self-reported measures, surgical factors and discharge plans. In order to develop the model, multivariable regression with bootstrap internal validation was used. The median LOS for the sample was four days (interquartile range 4 to 5). Statistically significant predictors of longer stay included older age, greater number of comorbidities, less knee flexion range of movement, frequent feelings of being down and depressed, greater walking aid support required, total (versus unicompartmental) knee replacement, bilateral surgery, low-volume surgeon, absence of carer at home, and expectation to receive step-down care. For ease of use, these ten variables were used to construct a nomogram-based prediction model which showed adequate predictive accuracy (optimism-corrected R(2) = 0.32) and calibration. If externally validated, a prediction model using easily and routinely obtained pre-operative measures may be used to predict absolute LOS in patients following knee replacement and help to better manage these patients.