Abstract. Introduction. The Oxford Unicompartmental Knee Replacement's (OUKR's) fully-congruent design minimises polyethylene wear. Consequently, wear is a rare failure mechanism. Phase-3 OUKR linear wear at 5 years was higher than previous OUKR phases, but very low compared to fixed-bearing UKRs. This study aimed to measure OUKR bearing wear at 10 years and investigate factors that may affect wear. Methodology. Bearing thickness for 39 OUKRs from a randomised study was calculated using radiostereometric analysis at regular intervals up to 10 years. Data for 39 and 29 OUKRs was available at 5 and 10 years, respectively. As creep occurs early, wear rate was calculated using linear regression between 6 months and 10 years. Relationships between wear and patient factors, fixation method, Oxford Knee Score (OKS), bearing position, and component position were analysed. Results. The mean wear rate was 0.06mm/year. Fixation method, age, OKS, component size, and bearing size had no correlation with wear. A higher BMI was associated with lower wear (p=0.01). Bearings more than 4mm from the wall had significantly more wear (p=0.04) than those less than 4mm from the wall. There was a linear correlation between the femoral component contact area on the bearing and wear (p=0.04). Conclusions. Phase-3 bearing wear rate is constant, significantly higher than previous OUKR phases at 10 years, and may increase the risk of long-term bearing failure. To minimise complications associated with wear, size 4 bearings should be used in young patients and manufacturing bearings from more durable, highly crosslinked polyethylene should be studied

Abstract. Introduction. Cementless total knee arthroplasty (TKA) offers a number of conceptual benefits including osteointegration, bone preservation and reduced aseptic loosening from third body wear. Evidence of equivalence to cemented fixation exists, but the cam-post interaction of posterior-stabilised (PS)-TKA on implant osteointegration remains uncertain. This study aims to assess the survivorship of a single prosthesis PS-TKA. Methodology. All patients undergoing a PS-TKA using the Triathlon Total Knee System (Stryker Orthopaedics, USA) between 01/01/2010 and 08/04/2019, with exposure to at least 2 years’ risk of revision were identified from the hospital database. Results. 1001 TKAs were identified; 734 cementless and 267 cemented. The cementless group more frequently were male, younger, of higher BMI; and had larger components used (p<0.01). Mean exposure to risk of revision was longer in the cementless group (69.5 vs 57 months, p<0.05). Return to theatre rates were similar (4.6% vs 4.8% p = 0.88), a greater proportion in the cementless group underwent revision (2.9% vs 1.1% p=0.11). Multivariate analysis was only possible for reoperations, increased with cemented fixation (OR 2.34 CI 1.01-5.43) and decreased with age (OR 0.96 CI 0.92-1.00). Conclusion. Both cementless and cemented Triathlon PS-TKA demonstrate excellent survivorship, with revision rates of 2.9% and 1.1% at a mean of 5.25 years. This difference was not statistically significant, and variations in baseline characteristics may have influenced it. Further study is planned to assess radiographs of these patients for evidence of osteointegration, and we advocate further study with greater patient numbers

Aims. Access to total knee arthroplasty (TKA) is sometimes restricted for patients with severe obesity (BMI ≥ 40 kg/m. 2. ). This study compares the cost per quality-adjusted life year (QALY) associated with TKA in patients with a BMI above and below 40 kg/m. 2. to examine whether this is supported. Methods. This single-centre study compared 169 consecutive patients with severe obesity (BMI ≥ 40 kg/m. 2. ) (mean age 65.2 years (40 to 87); mean BMI 44.2 kg/m. 2. (40 to 66); 129/169 female) undergoing unilateral TKA to a propensity score matched (age, sex, preoperative Oxford Knee Score (OKS)) cohort with a BMI < 40 kg/m. 2. in a 1:1 ratio. Demographic data, comorbidities, and complications to one year were recorded. Preoperative and one-year patient-reported outcome measures (PROMs) were completed: EuroQol five-dimension three-level questionnaire (EQ-5D-3L), OKS, pain, and satisfaction. Using national life expectancy data with obesity correction and the 2020 NHS National Tariff, QALYs (discounted at 3.5%), and direct medical costs accrued over a patient’s lifetime, were calculated. Probabilistic sensitivity analysis (PSA) was used to model variation in cost/QALY for each cohort across 1,000 simulations. Results. All PROMs improved significantly (p < 0.05) in both groups without differences between groups. Early complications were higher in BMI ≥ 40 kg/m. 2. : 34/169 versus 52/169 (p = 0.050). A total of 16 (9.5%) patients with a BMI ≥ 40 kg/m. 2. were readmitted within one year with six reoperations (3.6%) including three (1.2%) revisions for infection. Assuming reduced life expectancy in severe obesity and revision costs, TKA in patients with a BMI ≥ 40 kg/m. 2. costs a mean of £1,013/QALY (95% confidence interval £678 to 1,409) more over a lifetime than TKA in patients with BMI < 40 kg/m. 2. In PSA replicates, the maximum cost/QALY was £3,921 in patients with a BMI < 40 kg/m. 2. and £5,275 in patients with a BMI ≥ 40 kg/m. 2. . Conclusion. Higher complication rates following TKA in severely obese patients result in a lifetime cost/QALY that is £1,013 greater than that for patients with BMI < 40 kg/m. 2. , suggesting that TKA remains a cost-effective use of healthcare resources in severely obese patients where the surgeon considers it appropriate. Cite this article: Bone Joint J 2022;104-B(4):452–463

Introduction. Implementing operative eligibility thresholds based on body mass index (BMI) alone risks restricting access to improved pain, function, and quality-of-life. The purpose of this study was to: 1) investigate the relationship between BMI and improvements in 1-year patient reported outcome measures (PROMs), and 2) determine how many patients would have been denied 1-year improvements with specific BMI cut-offs. Methods. Data were collected on a prospective cohort of 3,214 TKA patients from 2015–2018. Clinically meaningful 1-year improvements were defined as 15 points for Knee Injury and Osteoarthritis Outcome Scores (KOOS) pain and Physical Function Shortform (PS), and 14 points for Knee-Related Quality-of-Life (KRQOL). For specific BMI cut-offs, the positive predictive value for predicting a failure to improve and number of patients denied surgery to avoid one failed improvement was calculated. Results. PROMs improvements were greater with increasing BMI. Patients with BMI ≥40 kg/m. 2. had median (Q1, Q3) KOOS pain improvements of 47.2 points (33.3, 58.3) and those with BMI 18.5–24.9 kg/m. 2. had median improvements of 41.7 (27.8, 55.6). Similar findings were observed for KOOS PS (28.4 vs. 26.3) and KRQOL (50.0 vs. 43.8). With a BMI cut-off of 30 kg/m. 2. , 9 patients would have been denied improvements from surgery for each failed improvement avoided whereas with a BMI cut-off of 50 kg/m. 2. , 15 patients would have been denied improvements from surgery. Implementing BMI thresholds alone did not influence the rate of improvements in KOOS-PS or KRQOL. Conclusion. Patients with higher BMI were observed to have greater improvements in PROMs after primary TKA. Enforcing arbitrary BMI cut-offs would deprive pain and functional improvements from patients who would benefit the most. Moreover, there appears to be no increase in the rate of PROMs improvements by enforcing BMI thresholds. This study demonstrates that determining TKA eligibility should involve a holistic approach rather than limiting to BMI measurements alone

Introduction. At a time when many surgeons are reluctant to perform a unilateral TKA in the obese patient, little is written on the safety and efficacy of bilateral simultaneous TKA in this same patient population. While these potential benefits are attractive to patients, surgeons may be hesitant to perform bilateral TKA due to the greater physical demand placed on the patient, and a potential increase in postoperative complication. The primary aim of this study was to analyze the impact of obesity on clinical outcomes and complication rates of patients undergoing bilateral TKA under one anesthetic. Materials and Methods. The clinical outcomes of 133 patients (266 knees) who underwent bilateral TKA between 2013 and 2016 were reviewed. The procedures were performed by three separate surgeons across three major academic institutions. ASA scores, tourniquet time, operative time, blood loss, length of stay, readmission, and postoperative complications were compared between different BMI categories of less than 30 kg/ m2, 30–34.99 kg/ m2, 35–39.99 kg/ m2and above 40 kg/ m2. Results. There were 83 females and 50 males who underwent bilateral TKA identified, with an average age of 60.17 years. The average LOS was 5 days and there was no significant impact of BMI on the length of stay or blood loss. 31 out of 133 patients experienced either a minor or major complication postoperatively (Table 1). Obese patients experienced more complications than non-obese patients. Specifically, patients identified as morbidly obese experienced a complication rate of 44.4%. This was significantly higher than the complication rate in the non-obese (less than 30 kg/ m2) patient cohort, 20.8% (p=.034). Of the 31 complications, 10 patients required a return to the operating room for a manipulation under anesthesia. There was no significant difference in the manipulation rate for the obese and non-obese patient. As BMI increased; postoperative ROM displayed a trend in the negative direction (Table 2). On average, obese patients had significantly higher ASA scores, with only 13.8% of patients with a BMI below 30 assigned an ASA score of 3 in comparison to 50% of patients with a BMI of 40 and above (p= .013) (Table 3). Higher BMI was significantly correlated with longer operative times (p=.002). Conclusion. Similar to numerous unilateral TKA studies in the obese patient, greater complication rates in the obese patient population were noted. The majority of complications that occurred within the time of this study were minor and did not affect the outcome of the procedure. Surgeons should carefully analyze the comorbidities of patients with a BMI above 40 kg/m2 such as cardiac history, diabetes mellitus, and smoking status when considering operating on morbidly obese patients and take steps to address these comorbidities and maximize the patient prior to surgery. For any figures or tables, please contact authors directly

Aims

The purpose of this study is to determine an individual’s age-specific prevalence of total knee arthroplasty (TKA) after cruciate ligament surgery, and to identify clinical and genetic risk factors associated with undergoing TKA.

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In the last decade, perioperative advancements have expanded the use of outpatient primary total knee arthroplasty (TKA). Despite this, there remains limited data on expedited discharge after revision TKA. This study compared 30-day readmissions and reoperations in patients undergoing revision TKA with a hospital stay greater or less than 24 hours. The authors hypothesized that expedited discharge in select patients would not be associated with increased 30-day readmissions and reoperations.

Introduction. This study explores whether subjects with bicruciate retaining TKRs (BiCR) have more normal knee biomechanics during level walking and stair ascent than subjects with posterior cruciate retaining TKRs (PCR). Due to anterior cruciate ligament (ACL) preservation, we expect BiCR subjects will not show the reduced flexion and altered muscle activation patterns characteristic of persons with TKRs. Methods. Motion and electromyography (EMG) data were collected during level walking and stair climbing for 16 BiCR subjects (4/12 m/f, 65±3 years, 30.7±7.0 BMI, 8/8 R/L), 17 PCR subjects (2/15 m/f, 65±7 years, 30.4±5.1 BMI, 7/10 R/L), and 17 elderly healthy control subjects (8/9 m/f, 55±10 years, 25.8±4.0 BMI, 10/7 R/L), using the point cluster marker set. Surface EMG electrodes were placed on the vastus medialis obliquus (VMO), rectus femoris (RF), biceps femoris (BF), and semitendinosus (ST) muscles. EMG data are reported as percent relative voluntary contraction (%RVC), normalized to the average peak EMG signals during level walking. Statistical nonparametric mapping was used for waveform analysis. Results. Both TKR groups were older, and PCR subjects had higher BMI than control subjects (p≤0.020). The BiCR group walked slower and with shorter stride lengths than controls (p≤0.012). During level walking, BiCR subjects had less knee extension and posterior tibial displacement than controls (95–98%, 96–100% gait cycle, p=0.003, 0.001). PCR subjects showed higher flexion mid-stance than controls (36–44% gait cycle, p=0.001) and more external rotation (66–69% gait cycle, p=0.003). Both TKR groups had smaller extension moment peaks (PCR 5, 59–75, 96%, BiCR 61–78, 95–97% stance, p≤0.007, 0.003) than the control group. The BiCR group had smaller adduction and external rotation moment peaks (20–24%, 10–18% stance, p=0.003, 0.001) compared with controls. During stair climbing, BiCR subjects displayed more external tibial rotation (4–16% stance), more knee abduction (36–52% stance), and a lower adduction moment peak (24–34% stance) compared to healthy controls (p≤0.005). TKR subjects from both groups showed lower flexion moment peaks than controls (PCR 24–35%, BiCR 24–28% stance, p≤0.001, 0.004). For EMG, PCR subjects had more BF activity during stair ascent versus level walking than healthy subjects (56–74% stance, p≤0.001). Discussion. BiCR and PCR showed more similarities than expected. Both had altered kinematics and kinetics compared to controls, suggesting some intrinsic extensor mechanism weakness, possibly an aftereffect of osteoarthritis. The EMG results agreed accordingly, as both TKR groups showed (non-significant) decreased quadriceps activity during stair climbing. Interestingly, PCR subjects also had more BF activity during stair than healthy controls, a trend that is common for both TKR subjects and people with ACL deficiency. On the other hand, although BiCR subjects were significantly more externally rotated in early stance phase for stair climbing, their rotation patterns began to align more closely to those of the healthy control subjects at lower flexion angles where the ACL should come into play. In conclusion, ACL retention in TKRs does not correct the extensor mechanism deficits commonly found in TKR patients, although it has some effect on secondary knee kinematics and hamstring muscle activity

Aims

This study compared patient-reported outcomes of three total knee arthroplasty (TKA) designs from one manufacturer: one cruciate-retaining (CR) design, and two cruciate-sacrificing designs, anterior-stabilized (AS) and posterior-stabilized (PS).

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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.

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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.

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Single-stage revision total knee arthroplasty (rTKA) is gaining popularity in treating chronic periprosthetic joint infections (PJIs). We have introduced this approach to our clinical practice and sought to evaluate rates of reinfection and re-revision, along with predictors of failure of both single- and two-stage rTKA for chronic PJI.

Unicompartmental knee replacement (UKR) is an established treatment for single compartment end-stage arthrosis with good recorded survivorship. UKRs are often implanted into more active younger patients, but patient selection remains controversial. A recent study, led by the Royal College of Surgeons Clinical Effectiveness Unit, demonstrated that prosthesis revision rates decrease strongly with age (Van Der Meulen et al 2008). It has therefore been suggested that UKR should only be considered in elderly patients. This contrasts our observed experience of early revision cases leading us to compare these patients with a control group. Between September 2002 and 2008, 812 Oxford Mobile Bearing Medial UKRs were implanted. We compared all patients who underwent UKR revision to Total Knee Replacement (TKR) against a control group of 50 consecutive UKR patients. 20 implants have required revision to TKR in 19 patients since 2002. Median age at index surgery was 68 (range 48-81), median BMI was 31 (range 25-41.5), 17 patients were female (85%), and median implant survival was 25 months (range 6-57). Control group median age at index surgery was 66 (range 46-81), median BMI was 30 (range 22-51), and 27 patients were female (54%). Median Oxford Knee Score recorded in September 2009 was 36 (range 14-54) for revision patients and 21 (range 14-39) for the control group (p=0.021). Our UKR patients with early failure requiring revision are far more likely to be female (p=0.015), as well as older and with a higher BMI than the control group. We feel this is a subset of patients at high risk of failure, despite meeting all criteria for UKR. The underlying causes are likely to be multifactorial, but a key factor may be that this group has varus tricompartment osteoarthritis rather than classical anteromedial osteoarthritis. Our data counters recent advice based on National Joint Registry data

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This study used an artificial neural network (ANN) model to determine the most important pre- and perioperative variables to predict same-day discharge in patients undergoing total knee arthroplasty (TKA).

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It has been shown that the preoperative modification of risk factors associated with obesity may reduce complications after total knee arthroplasty (TKA). However, the optimal method of doing so remains unclear. The aim of this study was to investigate whether a preoperative Risk Stratification Tool (RST) devised in our institution could reduce unexpected intensive care unit (ICU) transfers and 90-day emergency department (ED) visits, readmissions, and reoperations after TKA in obese patients.

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Recent total knee arthroplasty (TKA) designs have featured more anatomical morphologies and shorter tibial keels. However, several reports have raised concerns about the impact of these modifications on implant longevity. The aim of this study was to report the early performance of a modern, cemented TKA design.

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Meeting preoperative expectations is known to be of major influence on postoperative satisfaction after total knee arthroplasty (TKA). Improved management of expectation, resulting in more realistic expectations can potentially lead to higher postoperative satisfaction. The objective of this study was to assess the effect of an additional preoperative education module, addressing realistic expectations for long-term functional recovery, on postoperative satisfaction and expectation fulfilment.

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The purpose of this study was to compare the radiological outcomes of manual versus robotic-assisted medial unicompartmental knee arthroplasty (UKA).

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It remains difficult to diagnose early postoperative periprosthetic joint infection (PJI) following total knee arthroplasty (TKA). We aimed to validate the optimal cutoff values of ESR, CRP, and synovial fluid analysis for detecting early postoperative PJI in a large series of primary TKAs.

Bariatric surgery has been advocated as a means of reducing body mass index (BMI) and the risks associated with total knee arthroplasty (TKA). However, this has not been proved clinically. In order to determine the impact of bariatric surgery on the outcome of TKA, we identified a cohort of 91 TKAs that were performed in patients who had undergone bariatric surgery (bariatric cohort). These were matched with two separate cohorts of patients who had not undergone bariatric surgery. One was matched 1:1 with those with a higher pre-bariatric BMI (high BMI group), and the other was matched 1:2 based on those with a lower pre-TKA BMI (low BMI group). In the bariatric group, the mean BMI before bariatric surgery was 51.1 kg/m. 2 . (37 to 72), which improved to 37.3 kg/m. 2. (24 to 59) at the time of TKA. Patients in the bariatric group had a higher risk of, and worse survival free of, re-operation (hazard ratio (HR) 2.6; 95% confidence interval (CI) 1.2 to 6.2; p = 0.02) compared with the high BMI group. Furthermore, the bariatric group had a higher risk of, and worse survival free of re-operation (HR 2.4; 95% CI 1.2 to 3.3; p = 0.2) and revision (HR 2.2; 95% CI 1.1 to 6.5; p = 0.04) compared with the low BMI group. . While bariatric surgery reduced the BMI in our patients, more analysis is needed before recommending bariatric surgery before TKA in obese patients. Cite this article: Bone Joint J 2015;97-B:1501–5