Tibial Slope Is Not Associated With Implant Migration Following Cemented Total Knee Arthroplasty With a Single Implant Design.

BACKGROUND: The influence of tibial slope on tibial component migration following total knee arthroplasty has not been widely studied, although excessive posterior slope has been implicated in some failures. As implant micromotion measured with radiostereometric analysis can indicate successful fixation, the purpose of this study was to determine the associations between tibial slope, tibial component migration, and inducible displacement. METHODS: Radiostereometric analyses at 6 visits over 2 years quantified implant migration for 200 cemented total knee arthroplasties. Longitudinal data analysis examined the influence of postoperative tibial slope on implant migration (overall maximum total point motion (MTPM) migration and anterior-posterior tilt migration), accounting for age, sex, and body mass index. The correlations of tibial slope with 1-year migration, continuous migration, and inducible displacements were also examined. Additionally, the amount of change in slope was compared to migration. RESULTS: The mean posterior tibial slope was 8.0° (standard deviation [SD] 3.8°) preoperatively and 3.8° (SD 3.1°) postoperatively, with a mean reduction in slope of 4.2° (SD 4.7°). Postoperative tibial slope (range 14.0° posterior slope to 3.4° anterior slope) was not associated with longitudinal overall migration (P = .671) or anterior-posterior tilt migration (P = .704). There was no association between postoperative tibial slope and migration at 1 year postoperatively (P = .441 for MTPM migration, P = .570 for tilt migration), change in migration from 1 to 2 years (P = .951), or inducible displacement (P = .970 MTPM, P = .730 tilt). The amount of change in tibial slope was also not associated with migration or inducible displacement. CONCLUSIONS: Residual and change in postoperative tibial slope were not associated with implant migration into tilt or overall migration, or inducible displacement for a single implant design. These findings support positioning tibial implants in a range of slopes, which may support patient-specific approaches to implant alignment.

6-month migration sufficient for evaluation of total knee replacements: a systematic review and meta-analysis.

BACKGROUND AND PURPOSE: This updated meta-analysis evaluates the migration pattern of the tibial component of primary total knee replacements measured with radiostereometric analysis (RSA). We aimed to evaluate whether 6-month maximum total point motion (MTPM) values could be used instead of 1-year MTPM for RSA threshold testing and to present the pooled migration patterns for different implant designs that can be used as a benchmark. PATIENTS AND METHODS: The search included all published RSA studies on migration patterns of tibial components until 2023. Study groups were classified according to their prosthesis brand, fixation, and insert (PFI). Sub-analyses were performed to compare the mean tibial component migration patterns of different implant variables, stratified according to fixation. RESULTS: 96 studies (43 new studies), including 197 study groups and 4,706 knees, were included. Most migration occurred within the first 6 postoperative months (126 study groups: mean 0.58 mm, 95% confidence interval [CI] 0.50-0.65), followed by minimal migration between 6 and 12 months (197 study groups: mean 0.04 mm, CI 0.03-0.06), irrespective of the fixation method used. Distinct migration patterns were observed among the different fixation methods. No differences were found in migration patterns among cemented components in any of the sub-group analyses conducted. For uncemented implants, trabecular metal surfaced components seemed to migrate less than porous-coated or uncoated components Conclusion: Based on the small difference between MTPM values at 6 months and 1 year, MTPM at 6 months could be used instead of MTPM at 1 year for RSA threshold testing. The pooled migration patterns can be used as benchmark for evaluation of new implants by defining fixation-specific RSA thresholds when combined with implant survival.

A low-dose biplanar X-ray imager has RSA level precision in total knee arthroplasty.

BACKGROUND AND PURPOSE: The low radiation biplanar X-ray imager (EOS imaging, Paris, France) scans patients in a weight-bearing position, provides calibrated images, and limits radiation, an asset for serial radiostereometric analysis (RSA) studies. RSA in vivo precision values have not been published for this type of imaging system, thus the goal of this study was to assess the precision of RSA in vivo utilizing a low radiation biplanar imager. PATIENTS AND METHODS: At a mean of 5 years post-surgery (range 1.4-7.5 years), 15 total knee arthroplasty (TKA) participants (mean age 67 years at the time of imaging, 12 female, 3 male) with RSA markers implanted during index surgery were scanned twice at the same visit in the EOS imager. Precision of marker-based analysis was calculated by comparing the position of the implant relative to the underlying bone between the 2 examinations. RESULTS: The 95% limit of precision was 0.11, 0.04, and 0.15 mm along the x, y, and z axes, respectively and 0.15°, 0.20°, and 0.14° around the same axes. CONCLUSION: This precision study has shown an in vivo RSA precision of ≤ 0.15 mm and ≤ 0.20°, well within published uniplanar values for conventional arthroplasty RSA, with the added benefit of weight-bearing imaging, a lower radiation dose, and without the need for a reference object during the scan.

Continuity of primary care and emergency department visits following knee and hip replacement surgery: a retrospective cohort study.

BACKGROUND: Continuity of primary care (CPC) improves patient well-being, but the association between CPC and surgical outcomes has not been well studied. The numbers of joint replacement procedures are expected to rise considerably in the coming years, so it is crucial to identify factors related to successful outcomes. The purpose of this study was to examine the association between CPC and emergency department (ED) visits after knee and hip replacement surgery. METHODS: Physician claims and hospital data from 2005 to 2020 in Nova Scotia were used in this retrospective study. To measure CPC, we used the Modified Modified Continuity Index (MMCI), which is the number of primary care providers adjusted for the total number of visits. The outcome was ED visits within 90 days of discharge. Logistic regression was used to test for associations between MMCI and the probability of an ED visit. RESULTS: There were 28 574 knee and 16 767 hip procedures in the data set; 13.9% (95% confidence interval [CI] 13.5%-14.3%) and 13.5% (95% CI 13.0%-14.0%) of the patients, respectively, had an ED visit within 90 days. For patients who underwent knee procedures, the mean MMCI was 0.868 (95% CI 0.867-0.870); 10.7% (95% CI 10.4 %-11.1 %) had perfect continuity of care. For patients who underwent hip procedures, the corresponding measures were 0.864 (95% CI 0.862-0.866) and 13.5% (95% CI 13.0%-14.0%). There was a statistically significant negative association between greater continuity of care and the probability of an ED visit after controlling for confounders. CONCLUSION: Having multiple primary care providers before surgery increased the likelihood of negative outcomes following knee or hip replacement surgery compared with having a single provider. Presurgical conversations should include primary care history to improve postsurgical outcomes.

Patient appropriateness for total knee arthroplasty and predicted probability of a good outcome.

OBJECTIVES: One-fifth of total knee arthroplasty (TKA) recipients experience a suboptimal outcome. Incorporation of patients' preferences in TKA assessment may improve outcomes. We determined the discriminant ability of preoperative measures of TKA need, readiness/willingness and expectations for a good TKA outcome. METHODS: In patients with knee osteoarthritis (OA) undergoing primary TKA, we preoperatively assessed TKA need (Western Ontario-McMaster Universities OA Index (WOMAC) Pain Score and Knee injury and Osteoarthritis Outcome Score (KOOS) function, arthritis coping), health status, readiness (Patient Acceptable Symptom State, depressive symptoms), willingness (definitely yes-yes/no) and expectations (outcomes deemed 'very important'). A good outcome was defined as symptom improvement (met Outcome Measures in Rheumatology and Osteoarthritis Research Society International (OMERACT-OARSI) responder criteria) and satisfaction with results 1 year post TKA. Using logistic regression, we assessed independent outcome predictors, model discrimination (area under the receiver operating characteristic curve, AUC) and the predicted probability of a good outcome for different need, readiness/willingness and expectations scenarios. RESULTS: Of 1,053 TKA recipients (mean age 66.9 years (SD 8.8); 58.6% women), 78.1% achieved a good outcome. With TKA need alone (WOMAC pain subscale, KOOS physical function short-form), model discrimination was good (AUC 0.67, 95% CI 0.63 to 0.71). Inclusion of readiness/willingness, depressive symptoms and expectations regarding kneeling, stair climbing, well-being and performing recreational activities improved discrimination (p=0.01; optimism corrected AUC 0.70, 0.66-0.74). The predicted probability of a good outcome ranged from 44.4% (33.9-55.5) to 92.4% (88.4-95.1) depending on level of TKA need, readiness/willingness, depressive symptoms and surgical expectations. CONCLUSIONS: Although external validation is required, our findings suggest that incorporation of patients' TKA readiness, willingness and expectations in TKA decision-making may improve the proportion of recipients that experience a good outcome.

Gait biomechanics phenotypes among total knee arthroplasty candidates by machine learning cluster analysis.

Knee osteoarthritis patient phenotyping is relevant to developing targeted treatments and assessing the treatment efficacy of total knee arthroplasty (TKA). This study aimed to identify clusters among TKA candidates based on demographic and knee mechanic features during gait, and compare gait changes between clusters postoperatively. TKA patients underwent 3D gait analysis 1-week pre (n = 134) and 1-year post-TKA (n = 105). Principal component analysis was applied to frontal and sagittal knee angle and moment waveforms, extracting major patterns of variability. Age, sex, body mass index, gait speed, and frontal and sagittal pre-TKA angle and moment PC scores previously identified as relevant to TKA outcomes were standardized (mean = 0, SD = 1, [134 × 15]). Multidimensional scaling and machine learning-based hierarchical clustering were applied. Final clusters were validated by examining intercluster differences pre-TKA and gait feature changes (PostPCscore - PrePCscore ) by k-way Χ2 and ANOVA tests. Four TKA candidate phenotypes yielded optimum clustering metrics, interpreted as higher and lower functioning clusters that were predominantly male and female. Higher functioning clusters pre-TKA (clusters 1 and 4) had more dynamic sagittal flexion moment (p < 0.001) and frontal plane adduction moment (p < 0.001) loading/un-loading patterns during stance. Post-TKA, higher functioning clusters demonstrated less knee mechanic improvements during gait (flexion angle p < 0.001; flexion moment p < 0.001). TKA candidates can be characterized by four clusters, predominately separated by sex and knee joint biomechanics. Post-TKA knee kinematics and kinetics improvements were cluster-specific; lower functioning clusters experienced more improvement. Cluster-based patient profiling may aid in triaging and developing OA management and surgical strategies meeting group-level function needs.

Mid-Term Performance of the First Mass-Produced Three-Dimensional Printed Cementless Tibia in the United States as Reported in the American Joint Replacement Registry.

BACKGROUND: Cementless tibial components have shown improvements in clinical performance compared to predicate designs, though evidence supporting mid-term performance and fixation is scarce. The purpose of this study is to determine the mid-term survivorships, revision rates, and reasons why 3-dimensional printed cementless tibial baseplates (3DTKAs) failed compared to other cementless as well as cemented tibial baseplates reported from the American Joint Replacement Registry (AJRR) data. METHODS: All primary total knee arthroplasty (TKA) cases performed in patients 65 years of age or older within the AJRR from January 2, 2012 through June 30, 2020 were queried. A total of 28,631 3DTKAs were identified from 428 institutions. These were compared to all other "aggregated cementless tibia" (n = 7,577) and "aggregated cemented tibia" (n = 550,133) cases. Centers for Medicare & Medicaid Services data over the same time period were merged with AJRR data to determine survivorship and patient-timed incident revision rates per 1,000 years. Failure reasons were tracked during this study period. RESULTS: At 60 months, Kaplan-Meier implant survivorship was 98.9% (CI 98.7-99.0), 98.3% (CI 97.9-98.6), and 98.4% (CI 98.4-98.5) in the 3DTKA, aggregate cementless, and cemented knee cohorts, respectively (P < .0001). Patient-timed incident revision rates were 3.11 (CI 2.75-3.53), 3.99 (CI 3.34-4.76), and 3.35 (CI 3.28-3.42) for those cohorts, which corresponds to a revision rate of 0.31%, 0.40%, and 0.34% per year. CONCLUSION: In this analysis, 3DTKA had favorable survivorship and lower revision rates compared to aggregate cementless and cemented TKAs implanted from the same national database during the same time period.

Patient acceptable symptom state (PASS): thresholds for the EQ-5D-5L and Oxford hip and knee scores for patients with total hip and knee replacement.

PURPOSE: To define patient acceptable symptom state (PASS) cut-off values for the EQ-5D-5L and Oxford hip (OHS) and knee (OKS) scores 6 and 12 months after total hip (THR) or knee (TKR) replacement. To compare PASS cut-off values for the EQ-5D-5L scored using: (1) the Canadian value set, (2) the crosswalk value set, and (3) the equal weighted Level Sum Score (LSS). METHODS: We mailed questionnaires to consecutive patients following surgeon referral for primary THR or TKR and at 6 and 12 months post-surgery. Patient reported outcome measures (PROMs) were the EQ-5D-5L, the OHS, and OKS. We assessed PASS cut-off values for PROMs using percentile and ROC methods, with the Youden Index. RESULTS: Five hundred forty-two surgical patients (mean age, 64 years, 57% female, 49% THR) completed baseline and 12-month questionnaires. 89% of THR and 81% of TKR patients rated PASS as acceptable at 12 months. PASS cut-off values for THR for the EQ-5D-5L (Canadian) were 0.85 (percentile) and 0.84 (Youden) at 12 months. Cut-off values were similar for the LSS (0.85 and 0.85) and lower for the crosswalk value set (0.74 and 0.73), respectively. EQ-5D-5L cut-off values for TKR were Canadian, 0.77 (Percentile) and 0.78 (Youden), LSS, 0.75 and 0.80, and crosswalk, 0.67 and 0.74, respectively. Cut-off values 6 and 12 months post-surgery ranged from 38 to 39 for the OHS, and 28 to 36 for the OKS (range 0 worst to 48 best). CONCLUSION: PASS cut-off values for the EQ-5D-5L and Oxford scores varied, not only between methods and timing of assessment, but also by different EQ-5D-5L value sets, which vary between countries. Because of this variation, PASS cut-off values are not necessarily generalizable to other populations of TJR patients. We advise caution in interpreting PROMs when using EQ-5D-5L PASS cut-off values developed in different countries. A standardization of methods is needed before published cut-off values can be used with confidence in other populations.

The associations of implant and patient factors with migration of the tibial component differ by sex : a radiostereometric study on more than 400 total knee arthroplasties.

AIMS: Thresholds of acceptable early migration of the components in total knee arthroplasty (TKA) have traditionally ignored the effects of patient and implant factors that may influence migration. The aim of this study was to determine which of these factors are associated with overall longitudinal migration of well-fixed tibial components following TKA. METHODS: Radiostereometric analysis (RSA) data over a two-year period were available for 419 successful primary TKAs (267 cemented and 152 uncemented in 257 female and 162 male patients). Longitudinal analysis of data using marginal models was performed to examine the associations of patient factors (age, sex, BMI, smoking status) and implant factors (cemented or uncemented, the size of the implant) with maximum total point motion (MTPM) migration. Analyses were also performed on subgroups based on sex and fixation. RESULTS: In the overall group, only fixation was significantly associated with migration (p < 0.001). For uncemented tibial components in males, smoking was significantly associated with lower migration (p = 0.030) and BMI approached significance (p = 0.061). For females with uncemented components, smoking (p = 0.081) and age (p = 0.063) approached significance and were both associated with increased migration. The small number of self-reported smokers in this study warrants cautious interpretation and further investigation. For cemented components in females, larger sizes of tibial component were significantly associated with increased migration (p = 0.004). No factors were significant for cemented components in males. CONCLUSION: The migration of uncemented tibial components was more sensitive to patient factors than cemented implants. These differences were not consistent by sex, suggesting that it may be of value to evaluate female and male patients separately following TKA. Cite this article: Bone Joint J 2022;104-B(4):444-451.

The Effect of Patient Age and Surgical Appropriateness and Their Influence on Surgeon Recommendations for Primary TKA: A Cross-Sectional Study of 2,037 Patients.

BACKGROUND: Rising total knee arthroplasty (TKA) rates in younger patients raises concern about appropriateness. We asked: are younger individuals who seek consultation for TKA less likely to be appropriate for and, controlling for appropriateness, more likely to be recommended for surgery? METHODS: This cross-sectional study was nested within a prospective cohort study of knee osteoarthritis (OA) patients referred for TKA from 2014 to 2016 to centralized arthroplasty centers in Alberta, Canada. Pre-consultation, questionnaires assessed patients' TKA appropriateness (need, based on knee symptoms and prior treatment; readiness/willingness to undergo TKA; health status; and expectations) and contextual factors (for example, employment). Post-consultation, surgeons confirmed study eligibility and reported their TKA recommendation. Using generalized estimating equations to control for clustering by surgeon, we assessed relationships between patient age (<50, 50 to 59, ≥60 years) and TKA appropriateness and receipt of a surgeon TKA recommendation. RESULTS: Of 2,037 participants, 3.3% and 22.7% were <50 and 50 to 59 years of age, respectively, 58.7% were female, and 35.5% were employed. Compared with older participants, younger participants reported significantly worse knee symptoms, higher use of OA therapies, higher TKA readiness, and similar willingness, but had higher body mass index and were more likely to smoke and to consider the ability to participate in vigorous activities, for example, sports, as very important TKA outcomes. TKA was offered to 1,500 individuals (73.6% overall; 52.2%, 71.0%, and 75.4% of those <50, 50 to 59, and ≥60 years, respectively). In multivariate analyses, the odds of receiving a TKA recommendation were higher with greater TKA need and willingness, in nonsmokers, and in those who indicated that improved ability to go upstairs and to straighten the leg were very important TKA outcomes. Controlling for TKA appropriateness, patient age was not associated with surgeons' TKA recommendations. CONCLUSIONS: Younger individuals with knee OA referred for TKA had similar or greater TKA need, readiness, and willingness than older individuals. Incorporation of TKA appropriateness criteria into TKA decision-making may facilitate consideration of TKA benefits and risks in a growing population of young, obese individuals with knee OA. CLINICAL RELEVANCE: Younger people seeking TKA for knee OA had significant OA pain and disability despite recommended OA therapies, suggesting appropriateness for surgical consideration. However, they were significantly more likely to have morbid obesity, to smoke, and to consider return to vigorous activities, like sport, as important TKA outcomes. Whether the short- and longer-term risks of TKA are outweighed by the benefits is unclear and warrants additional research.

Relationship Between Patient-Reported Readiness for Total Knee Arthroplasty and Likelihood of a Good Outcome at One-Year Follow-Up.

OBJECTIVE: To determine the relationship between patients' preoperative readiness for total knee arthroplasty (TKA) and surgical outcome at 1 year post-TKA. METHODS: This prospective cohort study recruited patients with knee osteoarthritis (OA) who were ≥30 years and were referred for TKA at 2 hip/knee surgery centers in Alberta, Canada. Those who underwent primary unilateral TKA completed questionnaires prior to TKA to assess pain using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), physical disability using the Knee Injury and Osteoarthritis Outcome Score physical function short form, perceived arthritis coping efficacy, general self-efficacy, depressed mood using the Patient Health Questionnaire 8, body mass index, comorbidities, and TKA readiness (patient acceptable symptom state; willingness to undergo TKA); these same individuals also completed the above questionnaires 1 year post-TKA to assess surgical outcomes. A good TKA outcome was defined as an individual having improved knee symptoms, measured using the Osteoarthritis Research Society International-Outcome Measures in Rheumatology responder criteria, and overall satisfaction with results of the TKA. Poisson regression with robust error estimation was used to estimate the relative risk (RR) of a good outcome for exposures, before and after controlling for covariates. RESULTS: Of 1,272 TKA recipients assessed at 1 year post-TKA, 1,053 with data for the outcome assessed in the study were included (mean ± SD age 66.9 ± 8.8 years; 58.6% female). Most patients (87.8%) were definitely willing to undergo TKA and had "unacceptable" knee symptoms (79.7%). Among patients who underwent TKA, 78.1% achieved a good outcome. Controlling for pre-TKA OA-related disability, arthritis coping efficacy, comorbid hip symptoms, and depressed mood, definite willingness to undergo TKA and unacceptable knee symptoms were associated with a greater likelihood of a good TKA outcome, with adjusted RRs of 1.18 (95% confidence interval [95% CI] 1.04-1.35) and 1.14 (95% CI 1.02-1.27), respectively. CONCLUSION: Among patients who underwent TKA for knee OA, patients' psychological readiness for TKA and willingness to undergo TKA were associated with a greater likelihood of a good outcome. Incorporation of these factors in TKA decision-making may enhance patient outcomes and appropriate the use of TKA.

Association between surgical wait time and hospital length of stay in primary total knee and hip arthroplasty.

AIMS: In countries with social healthcare systems, such as Canada, patients may experience long wait times and a decline in their health status prior to their operation. The aim of this study is to explore the association between long preoperative wait times (WT) and acute hospital length of stay (LoS) for primary arthroplasty of the knee and hip. METHODS: The study population was obtained from the provincial Patient Access Registry Nova Scotia (PARNS) and the Canadian national hospital Discharge Access Database (DAD). We included primary total knee and hip arthroplasties (TKA, THA) between 2011 and 2017. Patients waiting longer than the recommended 180 days Canadian national standard were compared to patients waiting equal or less than the standard WT. The primary outcome measure was acute LoS postoperatively. Secondarily, patient demographics, comorbidities, and perioperative parameters were correlated with LoS with multivariate regression. RESULTS: A total of 11,833 TKAs and 6,627 THAs were included in the study. Mean WT for TKA was 348 days (1 to 3,605) with mean LoS of 3.6 days (1 to 98). Mean WT for THA was 267 days (1 to 2,015) with mean LoS of 4.0 days (1 to 143). There was a significant increase in mean LoS for TKA waiting longer than 180 days (2.5% (SE 1.1); p = 0.028). There was no significant association for THA. Age, sex, surgical year, admittance from home, rural residence, household income, hospital facility, the need for blood transfusion, and comorbidities were all found to influence LoS. CONCLUSION: Surgical WT longer than 180 days resulted in increased acute LoS for primary TKA. Meeting a shorter WT target may be cost-saving in a social healthcare system by having shorter LoS. Cite this article: Bone Jt Open 2021;2(8):679-684.

Early Identification of Patient Satisfaction Two Years After Total Knee Arthroplasty.

BACKGROUND: There are numerous reports of poor satisfaction after total knee arthroplasty (TKA), yet there is little known about when to use evidence-based models of care to improve patient outcomes. OBJECTIVE: This study aimed to characterize longitudinal changes in patient-reported satisfaction after TKA and to identify factors for early identification of poor satisfaction. METHODS: For a cohort of primary TKA surgeries (n = 86), patient-reported outcomes were captured one week before TKA and 6 weeks, 12 weeks, 6 months, and 1 and 2 years after TKA. "Satisfied" versus "not fully satisfied" patients were defined using a binary response (≥90 vs <90) from a 100-point scale. Wilcoxon signed-rank tests identified changes in satisfaction between follow-up times, and longitudinal analyses examined demographic and questionnaire factors associated with satisfaction. RESULTS: Improvements in satisfaction occurred within the first 6 months after TKA (P ≤ 0.01). Preoperative patient-reported outcome measures alone were not predictive of satisfaction. Key factors that improved longitudinal satisfaction included higher Oxford Knee Scores (odds ratio (OR) = 2.1, P < .001), general health (EQ-VAS, OR = 1.3, P = .03), and less visual analog scale pain (VAS; OR = 1.7, P < .001). Differences in these factors between satisfied and not fully satisfied patients were identified as early as 6 weeks after surgery. CONCLUSION: Visibly different satisfaction profiles were captured among satisfied and not fully satisfied patient responses, with differences in patient-perceived joint function, general health, and pain severity occurring as early as 6 weeks after surgery. This study provides metrics to support early identification of patients at risk of poor TKA satisfaction, enabling clinicians to apply timely targeted treatment and support interventions, with the aim of improving patient outcomes.

Tibial Component Migration After Total Knee Arthroplasty With High-Viscosity Bone Cement.

BACKGROUND: High-viscosity (HV) bone cements have been formulated to offer potentially advantageous handling characteristics. However, alteration in the handling characteristics could influence implant fixation and survival. The primary objective of this study was to use radiostereometric analysis after total knee arthroplasty to assess the migration of the Triathlon tibial component fixed with HV cement (Simplex HV). METHODS: Twenty-three patients were followed for two years with radiostereometric analysis examinations at 6 visits. Migration was compared with published thresholds and with a control group from a previously published study from the same center using the same implants fixed with a medium viscosity cement. Inducible displacement was assessed, and Oxford 12 Knee Scores and satisfaction were recorded. RESULTS: Mean maximum total point motion migration reaching 0.40 mm (SD 0.16) at one year, and 0.41mm (SD 0.17) at two years, demonstrating a pattern of stable fixation, below published thresholds of acceptable migration, and not significantly different from the control group. One implant had continuous migration between 1 and 2 years but was clinically asymptomatic. Mean maximum total point motion inducible displacement measured at least one year postoperatively was 0.3 mm (SD 0.12). Mean Oxford 12 Knee Scores improved from 19 (SD 7) preoperatively to 42 (SD 8) 2 years postoperatively. CONCLUSIONS: The use of HV cement demonstrated an acceptable pattern of migration at 2 years, indicating low risk for aseptic loosening.

Quantifying Achievable Levels of Improvement in Knee Joint Biomechanics During Gait After Total Knee Arthroplasty Relative to Osteoarthritis Severity.

Total knee arthroplasty (TKA) surgery improves knee joint kinematics and kinetics during gait for most patients, but a lack of evidence exists for the level and incidence of improvement that is achieved. The objective of this study was to quantify patient-specific improvements in knee biomechanics relative to osteoarthritis (OA) severity levels. Seventy-two patients underwent 3-dimensional (3D) gait analysis before and 1 year after TKA surgery, as well as 72 asymptomatic adults and 72 with moderate knee OA. A combination of principal component analysis and discriminant analyses were used to categorize knee joint biomechanics for patients before and after surgery relative to asymptomatic, moderate, and severe OA. Post-TKA, 63% were categorized with knee biomechanics consistent with moderate OA, 29% with severe OA, and 8% asymptomatic. The magnitude and pattern of the knee adduction moment and angle (frontal plane features) were the most significant contributors in discriminating between pre-TKA and post-TKA knee biomechanics. Standard of care TKA improves knee biomechanics during gait to levels most consistent with moderate knee OA and predominately targets frontal plane features. These results provide evidence for the level of improvement in knee biomechanics that can be expected following surgery and highlight the biomechanics most targeted by surgery.

Prospective clinical study using radiostereometric analysis (RSA) to evaluate fixation of a modular cemented polished femoral stem.

BACKGROUND: The long-term clinical success of cemented polished tapered femoral components has been demonstrated in prospective as well as registry studies. This stem design type has also been well studied with radiostereometric analysis (RSA) and provides a standard to evaluate alternative designs of polished tapered cemented femoral components. This prospective study evaluates the subsidence of a polished cemented stem with a modular neck design utilising RSA. METHODS: 26 patients were prospectively enrolled in the study and 23 were available for RSA analysis at 2 years. RESULTS: The average subsidence of the femoral implant was 1.1 mm (SD 0.4 mm) at 2 years post operation. There were no revisions in this group, specifically no failures of the modular stem-neck design as has been seen with other implants. CONCLUSIONS: The RSA subsidence pattern at 2 years of this cemented femoral stem is similar to other successful designs with long-term follow-up. The implications over time of stem neck modularity for cemented polished tapered femoral components requires further evaluation.