Aims. The purpose of this investigation was to determine the relationship between height, weight, and sex with implant size in total knee arthroplasty (TKA) using a multivariate linear regression model and a Bayesian model. Methods. A retrospective review of an institutional registry was performed of primary TKAs performed between January 2005 and December 2016. Patient demographics including patient age, sex, height, weight, and body mass index (BMI) were obtained from registry and medical record review. In total, 8,100 primary TKAs were included. The mean age was 67.3 years (SD 9.5) with a mean BMI of 30.4 kg/m. 2. (SD 6.3). The TKAs were randomly split into a training cohort (n = 4,022) and a testing cohort (n = 4,078). A multivariate linear regression model was created on the training cohort and then applied to the testing cohort . A Bayesian model was created based on the frequencies of implant sizes in the training cohort. The model was then applied to the testing cohort to determine the accuracy of the model at 1%, 5%, and 10% tolerance of inaccuracy. Results. Height had a relatively strong correlation with implant size (femoral component anteroposterior (AP) Pearson correlation coefficient (ρ) = 0.73, p < 0.001; tibial component mediolateral (ML) ρ = 0.77, p < 0.001). Weight had a moderately strong correlation with implant size, (femoral component AP ρ = 0.46, p < 0.001; tibial ML ρ = 0.48, p < 0.001). There was a significant linear correlation with height, weight, and sex with implant size (femoral component R. 2. = 0.607, p < 0.001; tibial R. 2. = 0.695, p < 0.001). The Bayesian model showed high accuracy in predicting the range of required implant sizes (94.4% for the femur and 96.6% for the tibia) accepting a 5% risk of inaccuracy. Conclusion. Implant size was correlated with basic demographic variables including height, weight, and sex. The linear regression and Bayesian models accurately predicted required implant sizes across multiple manufacturers based on height, weight, and sex alone. These types of predictive models may help improve operating room and implant supply chain efficiency. Level of Evidence: Level IV. Cite this article: Bone Joint J 2020;102-B(6 Supple A):85–90

Aims. Wear of the polyethylene (PE) tibial insert of total knee arthroplasty (TKA) increases the risk of revision surgery with a significant cost burden on the healthcare system. This study quantifies wear performance of tibial inserts in a large and diverse series of retrieved TKAs to evaluate the effect of factors related to the patient, knee design, and bearing material on tibial insert wear performance. Methods. An institutional review board-approved retrieval archive was surveyed for modular PE tibial inserts over a range of in vivo duration (mean 58 months (0 to 290)). Five knee designs, totalling 1,585 devices, were studied. Insert wear was estimated from measured thickness change using a previously published method. Linear regression statistical analyses were used to test association of 12 patient and implant design variables with calculated wear rate. Results. Five patient-specific variables and seven implant-specific variables were evaluated for significant association with lower insert wear rate. Six were significant when controlling for other factors: greater patient age, female sex, shorter duration in vivo, polished tray, highly cross-linked PE (HXLPE), and constrained knee design. Conclusion. This study confirmed that knee wear rate increased with duration in vivo. Older patients and females had significantly lower wear rates. Polished modular tibial tray surfaces, HXLPE, and constrained TKA designs were device design factors associated with significantly reduced wear rate. Cite this article: Bone Joint J 2021;103-B(11):1695–1701

Aims. The purpose of this study was to compare outcomes of combined total joint arthroplasty (TJA) (total hip arthroplasty (THA) and total knee arthroplasty (TKA) performed during the same admission) versus bilateral THA, bilateral TKA, single THA, and single TKA. Combined TJAs performed on the same day were compared with those staged within the same admission episode. Patients and Methods. Data from the National (Nationwide) Inpatient Sample recorded between 2005 and 2014 were used for this retrospective cohort study. Postoperative in-hospital complications, total costs, and discharge destination were reviewed. Logistic and linear regression were used to perform the statistical analyses. p-values less than 0.05 were considered statistically significant. Results. Combined TJA was associated with increased risk of deep vein thrombosis, prosthetic joint infection, irrigation and debridement procedures, revision arthroplasty, length of stay (LOS), and in-hospital costs compared with bilateral THA, bilateral TKA, single THA, and single TKA. Combined TJA performed on separate days of the same admission showed no statistically significant differences when compared with same-day combined TJA, but trended towards decreased total costs and total complications despite increased LOS. Conclusion. Combined TJA is associated with increased in-hospital complications, LOS, and costs. We do not recommend performing combined TJA during the same hospital stay. Cite this article: Bone Joint J 2019;101-B:573–581

Aims. Many patients undergoing total knee arthroplasty (TKA) have severe osteoarthritis (OA) in both knees and may consider either simultaneous or staged bilateral TKA. The implications of simultaneous versus staged bilateral TKA for return to work are not well understood. We hypothesized that employed patients who underwent simultaneous bilateral TKA would have significantly fewer days missed from work compared with the sum of days missed from each operation for patients who underwent staged bilateral TKA. Methods. The prospective arthroplasty registry at the Hospital for Special Surgery was used. Baseline characteristics and patient-reported outcome scores were evaluated. We used a linear regression model, adjusting for potential confounding variables including age, sex, preoperative BMI, and type of work (sedentary, moderate, high activity, or strenuous), to analyze time lost from work after simultaneous compared with staged bilateral TKA. Results. We identified 152 employed patients who had undergone simultaneous bilateral TKA and 61 who had undergone staged bilateral TKA, and had completed the registry’s return to work questionnaire. The simultaneous group missed a mean of 46.2 days (SD 29.1) compared with the staged group who missed a mean total of 68.0 days of work (SD 46.1) when combining both operations. This difference was statistically significant (p < 0.001). In multivariate mixed regression analysis adjusted for age, sex, BMI, American Society of Anesthesiologists status, and type of work, the simultaneous group missed a mean of 16.9 (SD 5.7) fewer days of work compared with the staged group (95% confidence interval 5.8 to 28.1; p = 0.003). Conclusion. Employed patients undergoing simultaneous bilateral TKA missed a mean of 17 fewer days of work as a result of their surgical treatment and rehabilitation compared with those undergoing staged bilateral TKA. This information may be useful to surgeons counselling employed patients with bilateral OA of the knee who are considering surgical treatment. Cite this article: Bone Joint J 2021;103-B(6 Supple A):108–112

Aims. The aim of this study was to assess the influence of obesity on the clinical outcomes and survivorship ten years postoperatively in patients who underwent a fixed-bearing unicompartmental knee arthroplasty (UKA). Patients and Methods. We prospectively followed 184 patients who underwent UKA between 2003 and 2007 for a minimum of ten years. A total of 142 patients with preoperative body mass index (BMI) of < 30 kg/m. 2. were in the control group (32 male, 110 female) and 42 patients with BMI of ≥ 30 kg/m. 2. were in the obese group (five male, 37 female). Pre- and postoperative range of movement (ROM), Knee Society Score (KSS), Oxford Knee Score (OKS), 36-Item Short-Form Health Survey (SF-36), and survivorship were analyzed. Results. Patients in the obese group underwent UKA at a significantly younger mean age (56.5 years (. sd. 6.4)) than those in the control group (62.4 years (. sd. 7.8); p < 0.001). There was no significant difference in preoperative functional scores. However, those in the obese group had a significantly lower ROM (116° (. sd. 15°) vs 123° (. sd. 17°); p = 0.003). Both groups achieved significant improvement in outcome scores regardless of BMI, ten years postoperatively. All patients achieved the minimal clinically important difference (MCID) for OKS and KSS. Both groups also had high rates of satisfaction (96.3% in the control group and 97.5% in the obese group) and the fulfilment of expectations (94.9% in the control group and 95.0% in the obese group). Multiple linear regression showed a clear association between obesity and a lower OKS two years postoperatively and Knee Society Function Score (KSFS) ten years postoperatively. After applying propensity matching, obese patients had a significantly lower KSFS, OKS, and physical component score (PCS) ten years postoperatively. Seven patients underwent revision to total knee arthroplasty (TKA), two in the control group and five in the obese group, resulting in a mean rate of survival at ten years of 98.6% and 88.1%, respectively (p = 0.012). Conclusion. Both groups had significant improvements in functional and quality-of-life scores postoperatively. However, obesity was a significant predictor of poorer improvement in clinical outcome and an increased rate of revision ten years postoperatively

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The aim of this study was to estimate the incremental use of resources, costs, and quality of life outcomes associated with surgical reconstruction compared to rehabilitation for long-standing anterior cruciate ligament (ACL) injury in the NHS, and to estimate its cost-effectiveness.

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Total knee arthroplasty (TKA) with a highly congruent condylar-stabilized (CS) articulation may be advantageous due to increased stability versus cruciate-retaining (CR) designs, while mitigating the limitations of a posterior-stabilized construct. The aim was to assess ten-year implant survival and functional outcomes of a cemented single-radius TKA with a CS insert, performed without posterior cruciate ligament sacrifice.

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The aim of this study was to evaluate the association between chondral injury and interval from anterior cruciate ligament (ACL) tear to surgical reconstruction (ACLr).

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Platelet-rich plasma (PRP) intra-articular injections may provide a simple and minimally invasive treatment for early-stage knee osteoarthritis (OA). This has led to an increase in its adoption as a treatment for knee OA, although there is uncertainty about its efficacy and benefit. We hypothesized that patients with early-stage symptomatic knee OA who receive multiple PRP injections will have better clinical outcomes than those receiving single PRP or placebo injections.

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Meniscal allograft transplantation (MAT) for patients with symptomatic meniscal loss has demonstrated good clinical results and survivorship. Factors that affect both functional outcome and survivorship have been reported in the literature. These are typically single-centre case series with relatively small numbers and conflicting results. Our aim was to describe an international, two-centre case series, and identify factors that affect both functional outcome and survival.

In Scotland, the number of primary total knee replacements performed annually has been increasing steadily. The price of the implant is fixed but the length of hospital stay is variable. We prospectively investigated all patients who underwent primary unilateral total knee replacement in the Scottish region of Fife, between December 1994 and February 2007 and assessed their recorded pre-operative details. The data were analysed using univariate and multiple linear regression statistical analysis. Data on the length of stay were available from a total of 2106 unilateral total knee replacements. The median length of hospital stay was eight days. The significant pre-operative risk factors for an increased length of stay were the year of admission, details of the consultant looking after the patient, the stair score, the walking-aid score and age. Awareness of the pre-operative factors which increase the length of hospital stay may provide the opportunity to influence them favourably and to reduce the time in hospital and the associated costs of unilateral total knee replacement

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Intraoperative pressure sensors allow surgeons to quantify soft-tissue balance during total knee arthroplasty (TKA). The aim of this study was to determine whether using sensors to achieve soft-tissue balance was more effective than manual balancing in improving outcomes in TKA.

Our aim was to compare the degree of patellar descent and alteration in angle of the inclination of the tibial plateau in lateral closing-wedge and medial opening-wedge high tibial osteotomy (HTO) in 51 consecutive patients with osteoarthritis of the medial compartment and varus malalignment. Patellar height was measured by the Insall-Salvati (IS) and the Blackburne-Peel (BP) ratios. The tibial inclination was determined by the Moore-Harvey (MH) method. Multivariate linear regression analysis was used to determine the influence of the type of HTO (closing vs opening wedge) on the post-operative patellar height or tibial inclination. The intra- and interobserver variability of these methods was determined before operation and at follow-up at one year. After an opening-wedge HTO the patellar height was significantly more decreased (mean post-operative difference: IS = 0.15; 95% confidence interval (CI) 0.06 to 0.23; BP = 0.11; 95% CI 0.05 to 0.18) compared with a closing-wedge HTO. The angle of tibial inclination differed significantly (mean post-operative difference MH = −6.40°; 95% CI −8.74 to −4.02) between the two HTO techniques, increasing after opening-wedge HTO and decreasing after closing-wedge HTO. There was no clinically-relevant difference in the intra- and interobserver variability of measurements of patellar height either before or after HTO

Components from 73 failed knee replacements (TKRs) consisting of rotating-platform, mobile-bearing and fixed-bearing implants were examined to assess the patterns of wear. The patterns were divided into low-grade (burnishing, abrasion and cold flow) and high-grade (scratching, pitting/metal embedding and delamination) to assess the severity of the wear of polyethylene. The rotating-platform group had a higher incidence of low-grade wear on the upper surface compared with the fixed-bearing group. By contrast, high-grade wear comprising scratching, pitting and third-body embedding was seen on the lower surface. Linear regression analysis showed a significant correlation of the wear scores between the upper and lower surfaces of the tibial insert (R. 2. = 0.29, p = 0.04) for the rotating-platform group, but no significant correlation was found for the fixed-bearing counterpart. This suggests that high-grade wear patterns on the upper surface are reduced with the rotating-platform design. However, the incidence of burnishing, pitting/third-body embedding and scratching wear patterns on the lower surface was higher compared with that in the fixed-bearing knee

The relationship between post-operative bone density and subsequent failure of total knee replacement (TKR) is not known. This retrospective study aimed to determine the relationship between bone density and failure, both overall and according to failure mechanism. All 54 aseptic failures occurring in 50 patients from 7760 consecutive primary cemented TKRs between 1983 and 2004 were matched with non-failing TKRs, and 47 failures in 44 patients involved tibial failures with the matching characteristics of age (65.1 for failed and 69.8 for non-failed), gender (70.2% female), diagnosis (93.6% OA), date of operation, bilaterality, pre-operative alignment (0.4 and 0.3 respectively), and body mass index (30.2 and 30.0 respectively). In each case, the density of bone beneath the tibial component was assessed at each follow-up interval using standardised, calibrated radiographs. Failing knees were compared with controls both overall and, as a subgroup analysis, by failure mechanism. Knees were compared with controls using univariable linear regression. Significant and continuous elevation in tibial density was found in knees that eventually failed by medial collapse (p < 0.001) and progressive radiolucency (p < 0.001) compared with controls, particularly in the medial region of the tibia. Knees failing due to ligamentous instability demonstrated an initial decline in density (p = 0.0152) followed by a non-decreasing density over time (p = 0.034 for equivalence). Non-failing knees reported a decline in density similar to that reported previously using dual-energy x-ray absorptiometry (DEXA). Differences between failing and non-failing knees were observable as early as two months following surgery. This tool may be used to identify patients at risk of failure following TKR, but more validation work is needed. Cite this article: Bone Joint J 2014;96-B:1503–9

We analysed whether a high body mass index (BMI) had a deleterious effect on outcome following autologous chondrocyte implantation (ACI) or matrix-carried autologous chondrocyte implantation (MACI) for the treatment of full-thickness chondral defects of the knee from a subset of patients enrolled in the ACI vs MACI trial at The Royal National Orthopaedic Hospital. The mean Modified Cincinnati scores (MCS) were significantly higher (p < 0.001) post-operatively in patients who had an ideal body weight (n = 53; 20 to 24.9 kg/m. 2. ) than in overweight (n = 63; 25 to 30 kg/m. 2. ) and obese patients (n = 22; > 30 kg/m. 2. ). At a follow-up of two years, obese patients demonstrated no sustained improvement in the MCS. Patients with an ideal weight experienced significant improvements as early as six months after surgery (p = 0.007). In total, 82% of patients (31 of 38) in the ideal group had a good or excellent result, compared with 49% (22 of 45) of the overweight and 5.5% (one of 18) in the obese group (p < 0.001). There was a significant negative relationship between BMI and the MCS 24 months after surgery (r = -0.4, p = 0.001). This study demonstrates that obese patients have worse knee function before surgery and experience no sustained benefit from ACI or MACI at two years after surgery. There was a correlation between increasing BMI and a lower MCS according to a linear regression analysis. On the basis of our findings patient selection can be more appropriately targeted.

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The primary aim of this study was to assess whether non-fatal postoperative venous thromboembolism (VTE) within six months of surgery influences the knee-specific functional outcome (Oxford Knee Score (OKS)) one year after total knee arthroplasty (TKA). Secondary aims were to assess whether non-fatal postoperative VTE influences generic health and patient satisfaction at this time.

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Social determinants of health (SDOHs) may contribute to the total cost of care (TCOC) for patients undergoing total knee arthroplasty (TKA). The aim of this study was to investigate the association between demographic data, health status, and SDOHs on 30-day length of stay (LOS) and TCOC after this procedure.

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Many surgeons choose to perform total knee arthroplasty (TKA) surgery with the aid of a tourniquet. A tourniquet is a device that fits around the leg and restricts blood flow to the limb. There is a need to understand whether tourniquets are safe, and if they benefit, or harm, patients. The aim of this study was to determine the benefits and harms of tourniquet use in TKA surgery.

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Unicompartmental knee arthroplasty (UKA) is a bone-preserving treatment option for osteoarthritis localized to a single compartment in the knee. The success of the procedure is sensitive to patient selection and alignment errors. Robotic arm-assisted UKA provides technological assistance to intraoperative bony resection accuracy, which is thought to improve ligament balancing. This paper presents the five-year outcomes of a comparison between manual and robotically assisted UKAs.