Abstract. Background. There is a trend towards minimising length of stay (LOS) after total knee arthroplasty (TKA), as longer LOS is associated with poorer outcomes and higher costs. Patient factors known to influence LOS after TKA include age and ASA grade. Evidence regarding body mass index (BMI) in particular is conflicting. Some studies find that increased BMI predicts greater LOS, while others find no such relationship. Previous studies have generally not examined socioeconomic status, which may be a confounder. They have generally been conducted outside the UK, and prior to the Covid-19 pandemic. Methods. We conducted a retrospective cohort study of 1031 primary TKAs performed 01-04-2021 to 31-12-2021, after resumption of elective surgery in our centre. A multivariate regression analysis was performed using a Poisson model over pre-operative variables (BMI, age, gender, ASA grade, index of multiple deprivation, and living arrangement) and peri-operative variables (AM/PM operation, operation side, duration, and day of the week). Results. Mean LOS was 2.6 days. BMI had no effect on LOS (p > 0.05). Longer LOS was experienced by patients of greater age (p < 0.001), increased ASA grade (p < 0.001), living alone (p < 0.01), PM start time (p < 0.001), and longer operation duration (p < 0.01). Male patients had shorter LOS (p < 0.001). Index of multiple deprivation had no effect (p > 0.05). Conclusion. BMI had no effect on LOS after TKA. Being female and living alone are significant risk factors which should be taken in to account in pre-operative planning

Aims. Patient dissatisfaction following primary total knee arthroplasty (TKA) with manual jig-based instruments has been reported to be as high as 30%. Robotic-assisted total knee arthroplasty (RA-TKA) has been increasingly used in an effort to improve patient outcomes, however there is a paucity of literature examining patient satisfaction after RA-TKA. This study aims to identify the incidence of patients who were not satisfied following RA-TKA and to determine factors associated with higher levels of dissatisfaction. Methods. This was a retrospective review of 674 patients who underwent primary TKA between October 2016 and September 2020 with a minimum two-year follow-up. A five-point Likert satisfaction score was used to place patients into two groups: Group A were those who were very dissatisfied, dissatisfied, or neutral (Likert score 1 to 3) and Group B were those who were satisfied or very satisfied (Likert score 4 to 5). Patient demographic data, as well as preoperative and postoperative patient-reported outcome measures, were compared between groups. Results. Overall, 45 patients (6.7%) were in Group A and 629 (93.3%) were in Group B. Group A (vs Group B) had a higher proportion of male sex (p = 0.008), preoperative chronic opioid use (p < 0.001), preoperative psychotropic medication use (p = 0.01), prior anterior cruciate ligament (ACL) reconstruction (p < 0.001), and preoperative symptomatic lumbar spine disease (p = 0.004). Group A was also younger (p = 0.023). Multivariate analysis revealed preoperative opioid use (p = 0.012), prior ACL reconstruction (p = 0.038), male sex (p = 0.006), and preoperative psychotropic medication use (p = 0.001) as independent predictive factors of patient dissatisfaction. Conclusion. The use of RA-TKA demonstrated a high rate of patient satisfaction (629 of 674, 93.3%). Demographics for patients not satisfied following RA-TKA included: male sex, chronic opioid use, chronic psychotropic medication use, and prior ACL reconstruction. Patients in these groups should be identified preoperatively and educated on realistic expectations given their comorbid conditions. Cite this article: Bone Jt Open 2024;5(9):758–765

Aims. Higher osteoblastic bone activity is expected in aseptic loosening and painful unicompartmental knee arthroplasty (UKA). However, insights into normal bone activity patterns after medial UKAs are lacking. The aim of this study was to identify the evolution in bone activity pattern in well-functioning medial mobile-bearing UKAs. Methods. In total, 34 patients (13 female, 21 male; mean age 62 years (41 to 79); BMI 29.7 kg/m. 2. (23.6 to 42.1)) with 38 medial Oxford partial UKAs (20 left, 18 right; 19 cementless, 14 cemented, and five hybrid) were prospectively followed with sequential 99mTc-hydroxymethane diphosphonate single photon emission CT (SPECT)/CT preoperatively, and at one and two years postoperatively. Changes in mean osteoblastic activity were investigated using a tracer localization scheme with volumes of interest (VOIs), reported by normalized mean tracer values. A SPECT/CT registration platform additionally explored cortical tracer evolution in zones of interest identified by previous experimental research. Results. Significant reduction of tracer activity from the preoperative situation was found in femoral and anteromedial tibial VOIs adjacent to the UKA components. Temporarily increased osteoblastic bone activity was observed in VOIs comprising the UKA keel structure at one year postoperatively compared to the preoperative activity. Persistent higher tracer uptake was found in the posterior tibial cortex at final follow-up. Multivariate analysis showed no statistical difference in osteoblastic bone activity underneath cemented or cementless components. Conclusion. Well-functioning medial mobile-bearing UKAs showed distinct changes in patterns of normalized bone tracer activity in the different VOIs adjacent to the prosthetic components, regardless of their type of fixation. Compared to the preoperative situation, persistent high bone activity was found underneath the keel and the posterior tibial cortex at final follow-up, with significant reduced activity only being identified in femoral and anteromedial tibial VOIs. Cite this article: Bone Joint J 2022;104-B(1):34–44

Aims. 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. Methods. Aseptic revision TKAs in the National Surgical Quality Improvement Program database were reviewed from 2013 to 2020. TKAs were stratified by length of hospital stay (greater or less than 24 hours). Patient demographic details, medical comorbidities, American Society of Anesthesiologists (ASA) grade, operating time, components revised, 30-day readmissions, and reoperations were compared. Multivariate analysis evaluated predictors of discharge prior to 24 hours, 30-day readmission, and reoperation. Results. Of 21,610 aseptic revision TKAs evaluated, 530 were discharged within 24 hours. Short-stay patients were younger (63.1 years (49 to 78) vs 65.1 years (18 to 94)), with lower BMI (32.3 kg/m. 2. (17 to 47) vs 33.6 kg/m. 2. (19 to 54) and lower ASA grades. Diabetes, chronic obstructive pulmonary disease, hypertension, and cancer were all associated with a hospital stay over 24 hours. Single component revisions (56.8% (n = 301) vs 32.4% (n = 6,823)), and shorter mean operating time (89.7 minutes (25 to 275) vs 130.2 minutes (30 to 517)) were associated with accelerated discharge. Accelerated discharge was not associated with 30-day readmission and reoperation. Conclusion. Accelerated discharge after revision TKA did not increase short-term complications, readmissions, or reoperations. Further efforts to decrease hospital stays in this setting should be evaluated. Cite this article: Bone Joint J 2022;104-B(12):1323–1328

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. Unicompartmental knee arthroplasty (UKA) provides improved early functional outcomes and less postoperative morbidity and pain compared with total knee arthroplasty (TKA). Opioid prescribing has increased in the last two decades, and recently states in the USA have developed online Prescription Drug Monitoring Programs to prevent overprescribing of controlled substances. This study evaluates differences in opioid requirements between patients undergoing TKA and UKA. Patients and Methods. We retrospectively reviewed 676 consecutive TKAs and 241 UKAs. Opioid prescriptions in morphine milligram equivalents (MMEs), sedatives, benzodiazepines, and stimulants were collected from State Controlled Substance Monitoring websites six months before and nine months after the initial procedures. Bivariate and multivariate analysis were performed for patients who had a second prescription and continued use. Results. Patients undergoing UKA had a second opioid prescription filled 50.2% of the time, compared with 60.5% for TKA (p = 0.006). After controlling for potential confounders, patients undergoing UKA were still less likely to require a second prescription than those undergoing TKA (adjusted odds ratio (OR) 0.58, 95% confidence interval (CI) 0.42 to 0.81; p = 0.001). Continued opioid use requiring more than five prescriptions occurred in 13.7% of those undergoing TKA and 5.8% for those undergoing UKA (p = 0.001), and was also reduced in UKA patients compared with TKA patients (adjusted OR 0.33, 95% CI 0.16 to 0.67; p = 0.022) in multivariate analysis. The continued use of opioids after six months was 11.8% in those undergoing TKA and 8.3% in those undergoing UKA (p = 0.149). The multivariate models for second prescriptions, continued use with more than five, and continued use beyond six months yielded concordance scores of 0.70, 0.86, and 0.83, respectively. Conclusion. Compared with TKA, patients undergoing UKA are less likely to require a second opioid prescription and use significantly fewer opioid prescriptions. Thus, orthopaedic surgeons should adjust their patterns of prescription and educate patients about the reduced expected analgesic requirements after UKA compared with TKA. Cite this article: Bone Joint J 2019;101-B(7 Supple C):22–27

Aims. The mobile bearing Oxford unicompartmental knee arthroplasty (OUKA) is recommended to be performed with the leg in the hanging leg (HL) position, and the thigh placed in a stirrup. This comparative cadaveric study assesses implant positioning and intraoperative kinematics of OUKA implanted either in the HL position or in the supine leg (SL) position. Methods. A total of 16 fresh-frozen knees in eight human cadavers, without macroscopic anatomical defects, were selected. The knees from each cadaver were randomized to have the OUKA implanted in the HL or SL position. Results. Tibial base plate rotation was significantly more variable in the SL group with 75% of tibiae mal-rotated. Multivariate analysis of navigation data found no difference based on all kinematic parameters across the range of motion (ROM). However, area under the curve analysis showed that knees placed in the HL position had much smaller differences between the pre- and post-surgery conditions for kinematics mean values across the entire ROM. Conclusion. The sagittal tibia cut, not dependent on standard instrumentation, determines the tibial component rotation. The HL position improves accuracy of this step compared to the SL position, probably due to better visuospatial orientation of the hip and knee to the surgeon. The HL position is better for replicating native kinematics of the knee as shown by the area under the curve analysis. In the supine knee position, care must be taken during the sagittal tibia cut, while checking flexion balance and when sizing the tibial component

Introduction. The prescription of opioids has increased in the last two decades. Recently, several states have developed online Prescription Drug Monitoring Programs aimed at preventing overprescribing of controlled substances. Unicompartmental knee arthroplasty (UKA) has been shown to provide improved early functional outcomes, faster recovery, and less postoperative morbidity and pain than total knee arthroplasty (TKA). The aim of this study is to evaluate differences in opioid prescription requirements between patients undergoing TKA and UKA. Methods. We retrospectively reviewed consecutive series of primary TKA from January 2017 to July 2017 and primary UKA from January 2016 to July 2017 using standardized perioperative pain protocols. All patients that underwent any other procedure 6 months prior to and after index surgery were excluded, resulting in 740 TKA and 241 UKA. Demographic and comorbidity information was collected for all patients. Opioid prescriptions, morphine milligram equivalents (MME), sedatives, benzodiazepines, and stimulants were collected from State Controlled Substance Monitoring website 6 months prior and after index procedures. Univariate and multivariate analysis were performed for patients that had a second prescription and continued use (defined as more than 6 months postoperatively). Results. Patients undergoing UKA had a second opioid prescription filled 50.2% of the time compared to 60.5% for TKA (p=0.006). In addition, continued opioid use after 6 months was 8.3% in UKAs compared to 11.8% in TKAs (p=0.149). When controlling for potential confounders, patients undergoing UKA were less likely to require a second prescription than TKA patients (adjusted odds ratio: 0.603 (95% Confidence Interval (CI): 0.425–0.855). In addition, continued use of opioids after 6 months was also reduced compared to patients undergoing TKA (adjusted OR: 0.51, 95% CI: 0.27–0.97) in the multivariate analysis. Other independent predictors of continued opioid use include obesity (OR 1.79, 95% CI 1.07–3.00) and preoperative opioid use (OR 1.66 per script, 95% CI: 1.49–1.86). Our models for second script and continued use reported AUC scores of 0.65 and 0.85, respectively. Conclusion. Patients with UKA are less likely to require a second opioid prescription and have continued opioid use even when controlling for a variety of potential confounders. Given the reduced opioid requirements associated with UKA, this study supports that orthopaedic surgeons should adjust their prescription patterns and educate patients regarding expected analgesic needs. Due to the retrospective nature of this study we were unable to precisely quantify the amount of opioids consumed in these patient groups. An ongoing prospective study will more accurately determine the duration and quantity of opioid use after UKA compared to TKA

Aims. The aim of this study was to investigate the incidence, risk factors, and outcome of venous thromboembolism (VTE) following anterior cruciate ligament (ACL) reconstruction in a nationwide cohort. Patients and Methods. All ACL reconstructions, primary and revision, that were recorded in the Swedish Knee Ligament Register (SKLR) between 2006 and 2013 were linked with data from the Swedish National Board of Health and Welfare. The incidence of VTE was determined by entries between the day of surgery until 90 days postoperatively based on diagnosis codes and the prescription of anticoagulants. Risk factors, outcome, and the use of thromboprophylaxis were analyzed. Descriptive statistics with multivariate analysis were used to describe the findings. Results. The cohort consisted of 26 014 primary and revision ACL reconstructions. There were 89 deep venous thromboses (DVTs) and 12 pulmonary emboli (PEs) with a total of 95 VTEs (0.4 %). Six patients with a PE had a simultaneous DVT. The only independent risk factor for VTE was age greater than or equal to 40 years (odds ratio 2.31, 95% confidence interval 1.45 to 3.70; p < 0.001). Thromboprophylaxis was prescribed to 9461 patients (36%) and was equally distributed between those with and those without a VTE (37.9% vs 36.4%). All patient-reported outcome measures (PROMs) one and two years postoperatively were significantly lower in those with VTE. Conclusion. The incidence of VTE following ACL reconstruction is 0.4%, and the only significant risk factor is age. Patients with VTE had worse postoperative clinical outcome than patients without VTE. We recommend against the routine use of thromboprophylaxis, but it should be considered in older patients

Aims. There is little information regarding the risk of a patient developing prosthetic joint infection (PJI) after primary total knee arthroplasty (TKA) when the patient has previously experienced PJI of a TKA or total hip arthroplasty (THA) in another joint. The goal of this study was to compare the risk of PJI of primary TKA in this patient population against matched controls. Patients and Methods. We retrospectively reviewed 95 patients (102 primary TKAs) treated between 2000 and 2014 with a history of PJI in another TKA or THA. A total of 50 patients (53%) were female. Mean age was 69 years (45 to 88) with a mean body mass index (BMI) of 36 kg/m. 2. (22 to 59). In total, 27% of patients were on chronic antibiotic suppression. Mean follow-up was six years (2 to 16). We 1:3 matched these (for age, sex, BMI, and surgical year) to 306 primary TKAs performed in 306 patients with a THA or TKA of another joint without a subsequent PJI. Competing risk with death was used for statistical analysis. Multivariate analysis was followed to evaluate risk factors for PJI in the study cohort. Results. The cumulative incidence of PJI in the study cohort (6.1%) was significantly higher than the matched cohort (2.6%) at ten years (hazard ratio (HR) 3.3; 95% confidence interval 1.18 to 8.97; p = 0.02). Host grade in the study group was not a significant risk factor for PJI. Patients on chronic suppression had a higher rate of PJI (HR 15; p = 0.002), with six of the seven patients developing PJI in the study group being on chronic suppression. The new infecting microorganism was the same as the previous in only two of seven patients. Conclusion. In this matched cohort study, patients undergoing a clean primary TKA with a history of TKA or THA PJI in another joint had a three-fold higher risk of PJI compared with matched controls with ten-year cumulative incidence of 6.1%. The risk of PJI was 15-fold higher in patients on chronic antibiotic suppression; further investigation into reasons for this and mitigation strategies are recommended. Cite this article: Bone Joint J 2019;101-B(7 Supple C):91–97

Aims. Little is known about employment following total knee arthroplasty (TKA). This study aims to identify factors which predict return to work following TKA in patients of working age in the United Kingdom. Patients & Methods. We prospectively assessed 289 patients (289 TKAs) aged ≤ 65 years who underwent TKA between 2010 and 2013. There were 148 women. The following were recorded pre-operatively: age, gender, body mass index, social deprivation, comorbidities, indication for surgery, work status and nature of employment, activity level as assessed by the University of California, Los Angeles (UCLA) activity score and Oxford Knee Score (OKS). The intention of patients to return to work or to retire was not assessed pre-operatively. At a mean of 3.4 years (2 to 4) post-operatively, the return to work status, OKS, the EuroQol-5 dimensions (EQ-5D) score, UCLA activity score and Work, Osteoarthritis and joint-Replacement (WORQ) score were obtained. Univariate and multivariate analyses were performed. Results. Of 261 patients (90%) who were working before TKA, 105 (40%) returned to any job, including 89 (34%) who returned to the same job at a mean of 13.5 weeks (2 to 104) post-operatively. A total of 108 (41%) retired following TKA and 18 remained on welfare. Patients not working before the operation did not return to work. Median UCLA scores improved in 125 patients (58%) from 4 (mild activity) to 6 (moderate activity) (p < 0.001). Significant (p < 0.05) factors which were predictive of return to any work included age, heavy or moderate manual work, better post-operative UCLA, OKS and EQ-5D general health scores. Significant predictive factors of return to the same work included age, heavy or moderate manual work and post-operative OKS. Multivariate analysis confirmed heavy or moderate manual work and age to independently predict a return to either any or the same work. All patients aged < 50 years who were working pre-operatively returned to any work as did 60% of those aged between 50 and 54 years, 50% of those aged between 55 and 59 years and 24% those aged between 60 and 65 years. . Conclusion. If working pre-operatively, patients aged < 50 years invariably returned to work following TKA, but only half of those aged between 50 to 60 years returned. High post-operative activity levels and patient reported outcome measures do not predict return to work following TKA. Cite this article: Bone Joint J 2017;99-B:1037–46

Aims. Risk of revision following total knee arthroplasty (TKA) is higher in patients under 55 years, but little data are reported regarding non-revision outcomes. This study aims to identify predictors of dissatisfaction in these patients. Patients and Methods. We prospectively assessed 177 TKAs (157 consecutive patients, 99 women, mean age 50 years; 17 to 54) from 2008 to 2013. Age, gender, implant, indication, body mass index (BMI), social deprivation, range of movement, Kellgren-Lawrence (KL) grade of osteoarthritis (OA) and prior knee surgery were recorded. Pre- and post-operative Oxford Knee Score (OKS) as well as Short Form-12 physical (PCS) and mental component scores were obtained. Post-operative range of movement, complications and satisfaction were measured at one year. Results . Overall, 44 patients with 44 TKAs (24.9%) under 55 years of age were unsure or dissatisfied with their knee. Significant predictors of dissatisfaction on univariate analysis included: KL grade 1/2 OA (59% dissatisfied), poor pre-operative OKS, complications, poor improvements in PCS and OKS and indication (primary OA 19% dissatisfied, previous meniscectomy 41%, multiply operated 42%, other surgery 29%, BMI > 40 kg/m. 2. 31%, post-traumatic OA 45%, and inflammatory arthropathy 5%). Poor pre-operative OKS, poor improvement in OKS and post-operative stiffness independently predicted dissatisfaction on multivariate analysis. Conclusion. Patients receiving TKA younger than 55 years old should be informed about the increased risks of dissatisfaction. Offering TKA in KL 1/2 is questionable, with a dissatisfaction rate of 59%. Cite this article: Bone Joint J 2016;98-B:1625–34

Aims. Debate continues regarding the optimum management of periprosthetic distal femoral fractures (PDFFs). This study aims to determine which operative treatment is associated with the lowest perioperative morbidity and mortality when treating low (Su type II and III) PDFFs comparing lateral locking plate fixation (LLP-ORIF) or distal femoral arthroplasty (DFA). Methods. This was a retrospective cohort study of 60 consecutive unilateral (PDFFs) of Su types II (40/60) and III (20/60) in patients aged ≥ 60 years: 33 underwent LLP-ORIF (mean age 81.3 years (SD 10.5), BMI 26.7 (SD 5.5); 29/33 female); and 27 underwent DFA (mean age 78.8 years (SD 8.3); BMI 26.7 (SD 6.6); 19/27 female). The primary outcome measure was reoperation. Secondary outcomes included perioperative complications, calculated blood loss, transfusion requirements, functional mobility status, length of acute hospital stay, discharge destination and mortality. Kaplan-Meier survival analysis was performed. Cox multivariate regression analysis was performed to identify risk factors for reoperation after LLP-ORIF. Results. Follow-up was at mean 3.8 years (1.0 to 10.4). One-year mortality was 13% (8/60). Reoperation was more common following LLP-ORIF: 7/33 versus 0/27 (p = 0.008). Five-year survival for reoperation was significantly better following DFA; 100% compared to 70.8% (95% confidence interval (CI) 51.8% to 89.8%, p = 0.006). There was no difference for the endpoint mechanical failure (including radiological loosening); ORIF 74.5% (56.3 to 92.7), and DFA 78.2% (52.3 to 100, p = 0.182). Reoperation following LLP-ORIF was independently associated with medial comminution; hazard ratio (HR) 10.7 (1.45 to 79.5, p = 0.020). Anatomical reduction was protective against reoperation; HR 0.11 (0.013 to 0.96, p = 0.046). When inadequately fixed fractures were excluded, there was no difference in five-year survival for either reoperation (p = 0.156) or mechanical failure (p = 0.453). Conclusion. Absolute reoperation rates are higher following LLP fixation of low PDFFs compared to DFA. Where LLP-ORIF was well performed with augmentation of medial comminution, there was no difference in survival compared to DFA. Though necessary in very low fractures, DFA should be used with caution in patients with greater life expectancies due to the risk of longer term aseptic loosening. Cite this article: Bone Joint J 2021;103-B(4):635–643

Introduction. Emergency department (ED) visits following primary total knee arthroplasty (TKA) can lead to poor patient satisfaction, potentially unnecessary readmissions, and greater overall healthcare costs. Reasons for post-operative ED visits are often entirely medical in nature and can be independent of the recent operation. Several strategies have been developed to help reduce ED visits. However, one major factor that can play a critical role in addressing potentially avoidable visits is provider and patient education. A major factor that can play a crucial role in addressing potentially avoidable visits is provider and patient education. It follows that a thorough understanding of which patients are visiting the ED and why can help in avoiding the visits. Therefore, the purpose of this study was to investigate: 1) causes and 2) patient-related factors (demographics and comorbidities) associated with ED visits following primary TKA. Methods. A national private payer database was queried for primary TKAs performed between 2007 and 2016 using the International Classification of Disease, ninth revision (ICD-9) procedural code 81.54. ED visits were identified using Current Procedural Terminology (CPT) codes 99281 to 99285. Patients with 90-day ED visits were in the study group (n=28,044) whereas those without 90-day ED visits served as controls (n=82,289). Causes for ED visits were divided into cardiopulmonary, gastrointestinal, renal, thromboembolic, leg pain, or wound-related. Patient demographics and risk factors assessed included age, gender, and body mass index (BMI) as well as several comorbidities (Table 1). Pearson's chi-square tests were performed to compare patient demographics and comorbidities between the cohorts. In order to adjust for potential confounders, multivariate binomial logistic regression analysis was performed to further evaluate the associations between patient factors and 90-day ED visits. A p-value less than 0.01 was considered statistically significant. Results. The most common reasons for ED visits were cardiopulmonary (51.30%), leg/back pain (46.20%), and gastrointestinal (31.60%) reasons. There was a greater proportion of women in the ED visit cohort compared to controls (p<0.0001; Table 1) and comorbidities (p<0.0001). Multivariate analysis revealed that patients with a history of COPD (odds ratio [OR] 1.48, p<0.001), depression (OR 1.42, p<0.0001), arrhythmias (OR: 1.38, p<0.0001), AIDS (O: 1.32, p<0.0001), and iron deficiency anemia (OR 1.28, p<0.0001), were at an increased risk of visting the ED within 90 days following primary TKA (Table 2). Conclusion. This analysis of over 100,000 patients identified that the most common reasons for ED visits are primarily medical in nature, and are not necessarily directly related to the recent operation. These findings should help guide pre-operative education and manage post-operative expectations to help limit potentially avoidable ED visits. Additionally, the data from this study can lend to policy changes targeting ED visits, particularly given the shift towards certain reimbursement models in arthroplasty. For figures, tables, or references, please contact authors directly

Introduction. There is no literature regarding the risk of a patient developing PJI after primary TKA if the patient has previously experienced PJI of a TKA or THA in another joint. The goal of this study was to compare the risk of PJI of primary TKA in this patient population compared to matched controls. Methods. We retrospectively reviewed 95 patients (102 primary TKAs) from 2000–2014 with a history of a TKA or THA PJI in another joint. Mean age was 69 years; mean BMI was 36 kg/m2. 27% high-risk patients were on chronic antibiotic suppression. Mean follow-up was 6 years. We 1:3 matched (to age, sex, BMI, and surgical year) these to 306 primary TKAs performed in patients with a THA or TKA of another joint without a subsequent PJI. Competing risk with death was used for statistical analysis. Multivariate analysis was utilized to evaluate risk factors for PJI in the study cohort. Results. The cumulative incidence of PJI in the study cohort (6.1%) was significantly higher than the matched cohort (2.6%) at 10 years (HR=3.3, p=0.02). Host grade in the study group was not a significant risk factor for PJI. Patients on chronic suppression had a higher rate of PJI (HR=15, p=0.002), with 6 of 7 patients developing a PJI being on chronic suppression. The new infecting microorganism was the same as the previous in only 2 of 7 patients. Conclusion. In this matched cohort study, patients undergoing a clean primary TKA with a history of a TKA or THA PJI in another joint had a 3-fold higher risk of PJI compared to matched controls with a 10-year cumulative incidence of 6.1%. The risk of PJI was 15-fold higher in patients on chronic suppression; further investigation into reasons for this and mitigation strategies is recommended

Introduction. Treatment of prosthetic joint infection (PJI) following total knee arthroplasty (TKA) may guided by PJI classification, taking into account infection duration and potential for biofilm formation. Debridement, antibiotics and implant retention (DAIR) is recommended for ‘post-operative’ and ‘acute’ haematogenous PJI. However, the time cut-off for ‘post-operative’ PJI varies across classification systems. Furthermore, poor DAIR success rates have been reported in acute haematogenous PJIs. This study aimed to determine the success of DAIR in a large cohort of PJIs, and assess the utility of current classification systems for predicting DAIR outcomes. Method. In this multicentre retrospective, cohort study, we identified 230 patients undergoing DAIR for first episode PJI following primary TKA. Patient demographics, disease and surgical factors were identified, and PJI subtype, post-operative antibiotic regime and treatment outcomes were recorded. Statistical analysis was performed to identify factors associated with failed DAIR, and success rates were analysed by multiple classification systems using receiver operating characteristic (ROC) curves. Results. At average follow-up of 6.9 years, DAIR failed in 46% of cases. ROC analysis found 3 month and 1 year cut-offs for ‘post-operative’ PJIs were equally predictive of outcomes (AUC=0.63). On multivariate survival analysis, DAIR failed in 63% of late haematogenous PJIs (implant age>1 year) compared to 36% of early (<1year) PJIs (OR=1.78, p=0.01). Staphylococcus aureus (OR=4.70, p<0.001) and gram negative infections (OR=2.56, p=0.031) were risk factors for DAIR failure in late PJIs. Conclusions. We found a high failure rate in late infections following TKA, irrespective of their classification as ‘acute haematogenous’ or ‘chronic’. Higher DAIR success rates were seen with implant age <1year. These findings call into question the utility of current classification systems based on duration of bacterial presence. For late infections (>1year), PJI caused by S. aureus or gram negative bacteria have a higher failure rate when treated with DAIR

Background. Unicompartmental knee arthroplasty (UKA) patients with knee partial thickness cartilage loss have inferior functional performance compared to those with full thickness loss. Therefore, the aim of the present study was to investigate on the association between postoperative patients' joint awareness and satisfaction and preoperative radiographic osteoarthritis (OA) Ahlbäck grade in subjects undergoing robotic arm-assisted UKA. Methods. This retrospective observational study includes 675 patients (681 knees) undergoing robotic arm-assisted UKA at two centres between January 2014 and May 2019. Pre-operatively, knee radiographs were performed, and Ahlbäck OA grade was measured by two independent observers. Post-operatively, patients were administered the Forgotten-Joint-Score-12 (FJS-12) and 5-Level-Likert-Scale to assess joint awareness and satisfaction. Postoperative complications and revisions were recorded. Correlations were described between FJS-12, satisfaction and OA grade by means of an adjusted multivariate statistical analysis. Results. A total of 574 patients (580 UKAs) were assessed at a mean follow-up of 3.6 years post-operatively (85.2% follow-up rate; min. 12, max. 75 months). Nine UKAs were revised. Primary or secondary medial knee OA was the preoperative diagnosis in 538 cases, osteonecrosis was present in 42 cases. Cases were divided based on their preoperative Ahlbäck grade in Group A (joint space narrowing, Ahlbäck 1, 279 cases), Group B (joint space obliteration or minor bone attrition, Ahlbäck 2 and 3, 197 cases) and Group C (moderate or severe bone attrition, Ahlbäck 4 and 5, 104 cases). Moderate to severe OA grades (Group B and C) were associated with higher probability of higher postoperative FJS-12 compared to joint space narrowing group (Odds Ratio 1.6 and 1.7, respectively, p<0.05). No associations were described between OA grade and patients' satisfaction. Conclusions. Patients with preoperative joint space obliteration and minor to severe bone attrition have higher probability of a having a forgotten joint after robotic arm-assisted UKA, compared to those without full cartilage thickness loss

Aims

Despite new technologies for total knee arthroplasty (TKA), approximately 20% of patients are dissatisfied. A major reason for dissatisfaction and revision surgery after TKA is persistent pain. The radiological grade of osteoarthritis (OA) preoperatively has been investigated as a predictor of the outcome after TKA, with conflicting results. The aim of this study was to determine if there is a difference in the intensity of pain 12 months after TKA in relation to the preoperative radiological grade of OA alone, and the combination of the intensity of preoperative pain and radiological grade of OA.

Aims. The primary aim of this study was to assess whether pain in the contralateral knee had a clinically significant influence on the outcome of total knee arthroplasty (TKA) according to the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score. Secondary aims were to: describe the prevalence of contralateral knee pain; identify if it clinically improves after TKA; and assess whether contralateral knee pain independently influences patient satisfaction with their TKA. Methods. A retrospective cohort of 3,178 primary TKA patients were identified from an arthroplasty database. Patient characteristics, comorbidities, and WOMAC scores were collected preoperatively and one year postoperatively for the index knee. In addition, WOMAC pain scores were also collected for the contralateral knee. Overall patient satisfaction was assessed at one year. Preoperative contralateral knee pain was defined according to the WOMAC score: minimal (> 78 points), mild (59 to 78), moderate (44 to 58), and severe (< 44). Multivariate regression analysis was used to adjust for confounding. Results. According to severity there were 1,425 patients (44.8%) with minimal, 710 (22.3%) with mild, 518 (16.3%) with moderate, and 525 (16.5%) with severe pain in the contralateral knee. Patients in the severe group had a greater clinically significant improvement in their functional WOMAC score (9.8 points; p < 0.001). Only patients in the moderate (22.9 points) and severe (37.8 points) groups had a clinically significant improvement in their contralateral knee pain (p < 0.001), but they were significantly less likely to be satisfied with their TKA (moderate: odds ratio (OR) 0.64, 95% confidence interval (CI) 0.4 to 0.92, p = 0.022; severe: OR 0.57, 95% CI 0.39 to 0.82, p = 0.002). Conclusion. Contralateral knee pain did not impair improvement in the WOMAC score after TKA, and patients with the most severe contralateral knee pain had a clinically significantly greater improvement in their functional outcome. More than half the patients presenting for TKA had mild-to-severe contralateral knee pain, most of whom had a clinically meaningful improvement but were significantly less likely to be satisfied with their TKA. Cite this article: Bone Joint J. 2020;102-B(1):125–131

PURPOSE OF STUDY. We investigated the effect of weekend knee arthroplasty surgery on length of inpatient stay. METHODS. 341 consecutive patients undergoing primary total knee replacement were retrospectively identified. Of these 62 underwent surgery during the weekend. Length of inpatient stay, age, sex, pre-operative haemoglobin, ASA rating, and day of surgery were recorded. Multiple regression analysis was used to determine the effect of these preoperative factors on length of post-operative inpatient stay. RESULTS. The mean length of stay following primary knee replacement was 5.9 days, with a median 4 days (2-31). Multivariate analysis confirmed that age at operation, sex, pre-operative haemoglobin and ASA were predictive of length of stay following knee arthroplasty. The day of the operation was not predictive of length of post operative stay. DISCUSSION. The results from this study suggest age, sex, ASA and preoperative haemoglobin are predictive of inpatient hospital stay. This is consistent with previous published data. Day of surgery was not predictive of length of stay. Our results suggest that weekend knee arthroplasty surgery does not result in an increased length of inpatient stay