The Oxford knee score (OKS) is a validated and widely accepted disease-specific patient-reported outcome measure, but there is limited evidence regarding any long-term trends in the score. We reviewed 5600 individual OKS questionnaires (1547 patients) from a prospectively-collected knee replacement database, to determine the trends in OKS over a ten-year period following total knee replacement. The mean OKS pre-operatively was 19.5 (95% confidence interval (CI) 18.8 to 20.2). The maximum post-operative OKS was observed at two years (mean score 34.4 (95% CI 33.7 to 35.2)), following which a gradual but significant decline was observed through to the ten-year assessment (mean score 30.1 (95% CI 29.1 to 31.1)) (p < 0.001). A similar trend was observed for most of the individual OKS components (p < 0.001). Kneeling ability initially improved in the first year but was then followed by rapid deterioration (p < 0.001). Pain severity exhibited the greatest improvement, although residual pain was reported in over two-thirds of patients post-operatively, and peak improvement in the night pain component did not occur until year four. Post-operative OKS was lower for women (p < 0.001), those aged < 60 years (p < 0.003) and those with a body mass index > 35 kg/m. 2. (p < 0.014), although similar changes in scores were observed. This information may assist surgeons in advising patients of their expected outcomes, as well as providing a comparative benchmark for evaluating longer-term outcomes following knee replacement. Cite this article: Bone Joint J 2013;95-B:45–51

Aims. This study aims to determine difference in annual rate of early-onset (≤ 90 days) deep surgical site infection (SSI) following primary total knee arthroplasty (TKA) for osteoarthritis, and to identify risk factors that may be associated with infection. Methods. This is a retrospective population-based cohort study using prospectively collected patient-level data between 1 January 2013 and 1 March 2020. The diagnosis of deep SSI was defined as per the Centers for Disease Control/National Healthcare Safety Network criteria. The Mann-Kendall Trend test was used to detect monotonic trends in annual rates of early-onset deep SSI over time. Multiple logistic regression was used to analyze the effect of different patient, surgical, and healthcare setting factors on the risk of developing a deep SSI within 90 days from surgery for patients with complete data. We also report 90-day mortality. Results. A total of 39,038 patients underwent primary TKA for osteoarthritis during the study period. Of these, 275 patients developed a deep SSI within 90 days of surgery, representing a cumulative incidence of 0.7%. The annual infection rate did not significantly decrease over the seven-year study period (p = 0.162). Overall, 13,885 (35.5%) cases were excluded from the risk analysis due to missing data. Risk factors associated with early-onset deep SSI included male sex, American Society of Anesthesiologists grade ≥ 3, blood transfusion, acute length of stay, and surgeon volume < 30 TKAs/year. Early-onset deep SSI was not associated with increased 90-day mortality. Conclusion. This study establishes a reliable baseline infection rate for early-onset deep SSI after TKA for osteoarthritis using robust Infection Prevention and Control surveillance data, and identifies several potentially modifiable risk factors. Cite this article: Bone Joint J 2023;105-B(9):971–976

Abstract. Introduction. Minimum clinically important differences (MCIDs) are critical to understanding changes in patient-reported outcome measure (PROM) scores after total joint arthroplasty (TJA). The usage and adoption of MCIDs not been well-studied. This study was performed to IDENTIFY trends in PROM and MCID use after TJA over the past decade. Methods. All articles published in the calendar years of 2010 and 2020 in CORR, JBJS, and the Journal of Arthroplasty were reviewed. Articles relating to clinical outcomes in primary total hip arthroplasty (THA) or total knee arthroplasty (TKA) were included. For each article, all reported PROMs and (if present) accompanying MCIDs were recorded. The use of PROMs and MCIDs were compared between articles published in 2010 and 2020. Results. Overall, 263 articles from 2010 and 546 articles from 2020 were included. The total number of articles reporting any PROM after THA and TKA increased from 131 in 2010 to 194 in 2020, but the proportion of articles reporting PROMs decreased from 49.8% (131/263) to 35.5% (194/546). Both the total number and proportion of articles reporting MCIDs increased from 2.3% (3/131) in 2010 to 16.5% (32/194) in 2020. These trends persisted when analyzing THA and TKA articles individually. Conclusions. Both the absolute number and proportion of articles reporting MCIDs in conjunction with PROMs after TJA has increased in the past decade but remains low. We recommend that journal editors and meeting organizers encourage the inclusion of MCID information in all reports on clinical outcomes after joint replacement

Abstract. Aims. Whilst short and mid-term activity levels after a Total Knee Replacement (TKR) have been reported in the literature; there is an over simplification of the reporting and longer-term activity levels are unknown. The aim of this study was to map the long-term trajectories of patients’ physical activity levels postoperatively to identify meaningful subgroups and explore associations with preoperative variables. Methods. This was a secondary analysis of a single centre longitudinal cohortstudy using group-based trajectory modelling (GBTM) of the University of California, Los Angeles (UCLA) physical activity score over ten years. Multinomial logistic regression models (both adjusted and unadjusted) were used to test associations between preoperative variables and trajectory group membership. Results. 266 of the 904 eligible patients were recruited (29%). Data from 260 patients was available for analysis. Four trajectory groups were identified with good fit of the model (average posterior probability 0.79 to 0.93). Of the four groups, the two more active groups had a peak activity level between two-three years postoperatively; the less active groups had a peak activity level at between three months and one year. Preoperative UCLA, participation in sports in the three years prior to surgery and male gender showed trends towards association with a higher activity group. Conclusions. Four trajectory groups were identified giving a more detailed understanding of temporal trends in physical activity levels post TKR. There was weak evidence to show an association between patient expectation, preoperative UCLA score and participation in sports in the prior three years and group membership

Abstract. Introduction. Our aim was to investigate trends in the incidence rate and main indication for revision knee replacement (rKR) over the past 15 years in the UK. Methodology. Cross-sectional study from 2006 - 2020 using data from the National Joint Registry (NJR). Crude incidence rates were calculated using population statistics from the Office for National Statistics. Results. Annual total counts of rKR increased from 2743 procedures in 2006 to 6819 procedures in 2019 (149% increase). The incidence rate of rKR increased from 6.3 per 100,000 adults in 2006 (95% CI 6.1 to 6.5) to 14 per 100,000 adults in 2019 (95% CI 14 to 14). Annual increases in the incidence rate of rKR became smaller over the study period. The incidence of rKR was highest in patients aged 70–79 years (50 per 100,000 adults [95% CI 48 to 52]). Aseptic loosening was the most frequent indication for rKR overall (20.5% procedures). However, rKR for aseptic loosening peaked in 2012 and subsequently decreased. rKR for infection increased incrementally over the study period to become the most frequent indication for rKR in 2019 (2.7 per 100,000 adults [95% CI 2.6 to 2.9]). Infection accounted for 17.2% first linked rKR, 36.7% second linked rKR and 50.7% third or more linked rKR. Conclusion. Recent trends suggest slowing of the rate of increase in the incidence of rKR. Infection is now the most common indication for rKR, following recent decreases in rKR for aseptic loosening. Infection was prevalent in re-revision KR procedures

Aims. The surgical target for optimal implant positioning in robotic-assisted total knee arthroplasty remains the subject of ongoing discussion. One of the proposed targets is to recreate the knee’s functional behaviour as per its pre-diseased state. The aim of this study was to optimize implant positioning, starting from mechanical alignment (MA), toward restoring the pre-diseased status, including ligament strain and kinematic patterns, in a patient population. Methods. We used an active appearance model-based approach to segment the preoperative CT of 21 osteoarthritic patients, which identified the osteophyte-free surfaces and estimated cartilage from the segmented bones; these geometries were used to construct patient-specific musculoskeletal models of the pre-diseased knee. Subsequently, implantations were simulated using the MA method, and a previously developed optimization technique was employed to find the optimal implant position that minimized the root mean square deviation between pre-diseased and postoperative ligament strains and kinematics. Results. There were evident biomechanical differences between the simulated patient models, but also trends that appeared reproducible at the population level. Optimizing the implant position significantly reduced the maximum observed strain root mean square deviations within the cohort from 36.5% to below 5.3% for all but the anterolateral ligament; and concomitantly reduced the kinematic deviations from 3.8 mm (SD 1.7) and 4.7° (SD 1.9°) with MA to 2.7 mm (SD 1.4) and 3.7° (SD 1.9°) relative to the pre-diseased state. To achieve this, the femoral component consistently required translational adjustments in the anterior, lateral, and proximal directions, while the tibial component required a more posterior slope and varus rotation in most cases. Conclusion. These findings confirm that MA-induced biomechanical alterations relative to the pre-diseased state can be reduced by optimizing the implant position, and may have implications to further advance pre-planning in robotic-assisted surgery in order to restore pre-diseased knee function. Cite this article: Bone Joint J 2024;106-B(11):1231–1239

Aims. As has been shown in larger animal models, knee immobilization can lead to arthrofibrotic phenotypes. Our study included 168 C57BL/6J female mice, with 24 serving as controls, and 144 undergoing a knee procedure to induce a contracture without osteoarthritis (OA). Methods. Experimental knees were immobilized for either four weeks (72 mice) or eight weeks (72 mice), followed by a remobilization period of zero weeks (24 mice), two weeks (24 mice), or four weeks (24 mice) after suture removal. Half of the experimental knees also received an intra-articular injury. Biomechanical data were collected to measure passive extension angle (PEA). Histological data measuring area and thickness of posterior and anterior knee capsules were collected from knee sections. Results. Experimental knees immobilized for four weeks demonstrated mean PEAs of 141°, 72°, and 79° after zero, two, and four weeks of remobilization (n = 6 per group), respectively. Experimental knees demonstrated reduced PEAs after two weeks (p < 0.001) and four weeks (p < 0.0001) of remobilization compared to controls. Following eight weeks of immobilization, experimental knees exhibited mean PEAs of 82°, 73°, and 72° after zero, two, and four weeks of remobilization, respectively. Histological analysis demonstrated no cartilage degeneration. Similar trends in biomechanical and histological properties were observed when intra-articular violation was introduced. Conclusion. This study established a novel mouse model of robust knee contracture without evidence of OA. This was appreciated consistently after eight weeks of immobilization and was irrespective of length of remobilization. As such, this arthrofibrotic model provides opportunities to investigate molecular pathways and therapeutic strategies. Cite this article: Bone Joint Res 2023;12(1):58–71

Aims. There is concern that aggressive target pricing in the new Bundled Payment for Care Improvement Advanced (BPCI-A) penalizes high-performing groups that had achieved low costs through prior experience in bundled payments. We hypothesize that this methodology incorporates unsustainable downward trends on Target Prices and will lead to groups opting out of BPCI Advanced in favour of a traditional fee for service. Methods. Using the Centers for Medicare and Medicaid Services (CMS) data, we compared the Target Price factors for hospitals and physician groups that participated in both BPCI Classic and BPCI Advanced (legacy groups), with groups that only participated in BPCI Advanced (non-legacy). With rebasing of Target Prices in 2020 and opportunity for participants to drop out, we compared retention rates of hospitals and physician groups enrolled at the onset of BPCI Advanced with current enrolment in 2020. Results. At its peak in July 2015, 342 acute care hospitals and physician groups participated in Lower Extremity Joint Replacement (LEJR) in BPCI Classic. At its peak in March 2019, 534 acute care hospitals and physician groups participated in LEJR in BPCI Advanced. In January 2020, only 14.5% of legacy hospitals and physician groups opted to stay in BPCI Advanced for LEJR. Analysis of Target Price factors by legacy hospitals during both programmes demonstrates that participants in BPCI Classic received larger negative adjustments on the Target Price than non-legacy hospitals. Conclusion. BPCI Advanced provides little opportunity for a reduction in cost to offset a reduced Target Price for efficient providers, as made evident by the 85.5% withdrawal rate for BPCI Advanced. Efficient providers in BPCI Advanced are challenged by the programme’s application of trend and efficiency factors that presumes their cost reduction can continue to decline at the same rate as non-efficient providers. It remains to be seen if reverting back to Medicare fee for service will support the same level of care and quality achieved in historical bundled payment programmes. Cite this article: Bone Joint J 2021;103-B(6 Supple A):119–125

Abstract. Introduction. There is little published literature to support the claim that a successful total knee replacement (TKR) is predictive of future good outcomes on the contralateral side. The objective was to identify whether outcome from the first of staged TKRs could be used to predict the outcome of the contralateral TKR. Methodology. This was a retrospective cohort study of 1687 patients over a 25-year period undergoing staged bilateral TKRs in a UK arthroplasty centre. A control group of 1687 patients undergoing unilateral TKR with matched characteristics was identified. Primary outcomes: satisfaction and Knee Society Score (KSS) at one year. Results. Preoperative status was comparable for pain, ROM and KSS (mean 41, 45, 43±14). At one year, dissatisfaction was similar for all groups (4% first of staged TKR, 4% second of staged TKR, 5% controls). If the first TKR had a good outcome, the relative risk of a contralateral bad outcome was 20% less than controls (95% CI 0.6–1.2). If the first TKR had a poor outcome, the risk of a second poor outcome was 4 times higher (95% CI 2.8–6.1), increasing from 6% to 28% (absolute risk). Conclusion. Patients undergoing the second of staged TKRs with a previous good outcome are likely to do well in their second procedure (94 in 100 will go on to have a second good outcome). Of those with a previous poor outcome, 28 in 100 will have a second poor outcome. The trend was persistent despite correcting for gender, age, BMI, and diagnosis

Introduction. Bundled Payments (BP) were a revolutionary new experiment for CMS that tested whether risk sharing for an episode of care would improve quality and reduce costs. The initial success of BP accelerated their growth as evidence by the launch of both mandatory and commercial bundles. Success in BP is dependent on the target price and the opportunity to reduce avoidable costs during the episode of care. There is concern that the aggressive target pricing methodology in the new model (BPCI-Advanced) penalizes high performing groups that already achieved low episode costs through prior experience and investment in BP. We hypothesize that this methodology incorporates unsustainable downward trends on target prices to a point beyond reasonableness for efficient groups to reduce additional costs and will lead to a large percentage of groups opting out of BPCI-A in favor of a return to fee for service (FFS) reimbursement. Methods. Using CMS data, we compared the target price factors for hospitals that participated in both BPCI classic (2013 –2018) and BPCI Advanced (beginning 10/2018), referred to as “legacy hospitals”, with hospitals that only participated in BPCI Advanced (beginning 10/2018). With the rebasing of BPCI-A target prices in Jan 2020 and the opportunity for participants to drop out of individual episode types or the program all together, we compared the retention of episode types that hospitals initially enrolled at the onset of BPCI-A with the current enrollment in 2020. Locally, we analyzed the BPCI-A target price factors across hospitals for a large orthopaedic practice that participated in BPCI Classic and the impact it had on the financial incentive/disincentive to remain in the lower extremity joint replacement episode type in 2020. Results. At its peak in July 2015, 423 acute care hospitals participated in one or more episode type in BPCI Classic. At its peak in March 2019, 715 acute care hospitals participated in one or more episode types in BPCI-Advanced. 130 (18%) of the hospitals in BPCI Advanced were also legacy participants in BPCI Classic, enrolling in 414 of the same episode types during both programs. In 2020, 251 (61%) of the episode types that hospitals were in enrolled in for both BPCI Classic and BPCI Advanced were dropped, suggesting prior experience in BPCI influences a participant's opportunity for success in BPCI Advanced. Furthermore, an analysis of the target price factors for episode types enrolled in by legacy hospitals during both programs suggests that prior participation in BPCI Classic is correlated with more aggressive target prices. A comparison of target price factors of similar hospitals reveals that legacy BPCI Classic hospitals that participated in lower extremity joint replacement (LEJR) BPCI Advanced received a larger negative adjustment on the target price (0.11 lower on average as a product of the Peer Adjusted Trend factor and ACH Efficiency factor) than non-legacy hospitals that participated in BPCI Advanced. Furthermore, analysis of the hospital targets for a large, high-performing legacy Physician Group Practice in BPCI Classic for LEJR revealed even greater negative adjustment on the target price than non-legacy participants. Comparing participants of similar peer groups on the Peer Adjusted Trend and ACH Efficiency factors suggests that CMS expects costs to decline more for legacy hospitals that have achieved efficiency than hospitals with no prior BP experience and higher baseline spend. Conclusions. BPCI Advanced provides little to no opportunity for a reduction in cost for already efficient TJA providers, as evident by the 55% dropout rate for BPCI-A participants in LEJR between model years 1 and 3. Efficient TJA providers in BPCI Advanced are challenged by the program's utilization of a peer adjusted trend factor and efficiency factor that presumes their costs will decline at the same aggressive rate or more than nonefficient TJA providers. It remains to be seen if reverting to Medicare fee for service will support the same level of care coordination, cost and quality achieved in historical TJA bundled payment programs

Introduction. As total knee arthroplasty incidence in the United States continues to increase, health care entities are looking to reform policy to decrease costs while improving efficiency and quality of care. The allocation of hospital and surgeon charges and payments is an important aspect of health care economics, but the trends and relationship between surgeon and hospital charges and payments for knee arthroplasty have not been well examined. The goal of this study is to report trends and variation in hospital charges and payments compared to surgeon charges and payments for total knee arthroplasty in a Medicare population. Methods. The 5% Medicare sample was used to capture hospital and surgeon charges and payments for total knee arthroplasty from 2005–2014. Two important values were calculated: (1) the charge multiplier (CM) which is the ratio of hospital to surgeon charges, and (2) the payment multiplier (PM), which is the ratio of hospital to surgeon payments. The year to year variation and regional trends in patient demographics, Charlson Comorbidity Index (CCI), length of stay (LOS), CM and PM were evaluated for all patients. Statistical significance of trends was evaluated using student's t-tests. Correlations between the financial multipliers and LOS were evaluated using a Pearson correlation coefficient (r). Results. 117,698 patients were included. Hospital charges were significantly higher than surgeon charges throughout the study period and increased substantially (CM increased from 7.9 to 11.4, p <0.0001) [Fig 1,2]. Hospital payments relative to surgeon payments ratio (PM) followed a similar trend, increasing from 10.0 to 14.6 (p < 0.0001). [Fig 1,2]. Similar trends were noted in all four regions of the US. LOS decreased significantly throughout the study from 3.8 to 2.8 days (p < 0.0001). CCI remained stable over the study period. Both the CM (r2 = −0.90) and PM (r2 = −0.84) were strongly negatively associated with LOS, meaning that as LOS decreased, the ratio of hospital to surgeon charges and payments (CM and PM) paradoxically significantly increased [Fig 3]. Conclusions. Hospital charges and payments relative to surgeon charges and payments have significantly increased for total knee arthroplasty despite stable patient complexity as measured by CCI and decreasing LOS. These results encourage the need for future studies with detailed cost analysis to identify the causes of hospital and surgeon financial malalignment. As healthcare shifts toward value-based care with shared responsibility for outcomes and cost, more closely aligned incentives between hospitals and providers is needed. For figures, tables, or references, please contact authors directly

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

Introduction. The American Joint Replacement Registry (AJRR) is the largest registry of total hip and knee arthroplasty (THA and TKA) procedures performed in the U.S. The National (Nationwide) Inpatient Sample (NIS) is a public database containing demographic estimates based on more than seven million hospitalizations annually. The purpose of this study was to analyze whether AJRR data is representative of the national experience with TJA as represented in NIS. Methods. Cohen's d effect sizes were computed to ascertain the magnitude of differences in demographics, hospital volume (in 50 patient increments), and geographic characteristics between the AJRR and NIS databases. Results. The study included [NIS: 2,316,345 vs. AAOS-AJRR: 557,684] primary THA [NIS: 3,417,700 vs. AAOS-AJRR: 809,494] TKA procedures. The magnitude of distribution, as determined by the Cohen's d effect size, showed the proportions of AJRR and NIS patients were similar based on overall sex [THAs (d=0.03) and TKAs (d=0.02)] and age [THAs (d=0.17) and TKAs (d=0.12)]. Similarly, only small differences (d=0.34 or less) were identified between databases considering hospital volume and geography. AJRR was underrepresented in Southern regions and hospitals with low procedure volume and overrepresented in Northern hospitals and those with larger volume. Both NIS and AJRR followed a similar overall trend with a majority of procedures performed at hospitals with <50 cases per year. Conclusion. Distributions across hospital volume, age, and geography were proportionally similar between the AJRR and NIS databases, which suggests that AJRR data is representative of national trends and may be generalized to the larger U.S. population

Aims. This study aims to investigate the effects of posterior tibial slope (PTS) on knee kinematics involved in the post-cam mechanism in bi-cruciate stabilized (BCS) total knee arthroplasty (TKA) using computer simulation. Methods. In total, 11 different PTS (0° to 10°) values were simulated to evaluate the effect of PTS on anterior post-cam contact conditions and knee kinematics in BCS TKA during weight-bearing stair climbing (from 86° to 6° of knee flexion). Knee kinematics were expressed as the lowest points of the medial and lateral femoral condyles on the surface of the tibial insert, and the anteroposterior translation of the femoral component relative to the tibial insert. Results. Anterior post-cam contact in BCS TKA was observed with the knee near full extension if PTS was 6° or more. BCS TKA showed a bicondylar roll forward movement from 86° to mid-flexion, and two different patterns from mid-flexion to knee extension: screw home movement without anterior post-cam contact and bicondylar roll forward movement after anterior post-cam contact. Knee kinematics in the simulation showed similar trends to the clinical in vivo data and were almost within the range of inter-specimen variability. Conclusion. Postoperative knee kinematics in BCS TKA differed according to PTS and anterior post-cam contact; in particular, anterior post-cam contact changed knee kinematics, which may affect the patient’s perception of the knee during activities. Cite this article: Bone Joint Res 2020;9(11):761–767

Aims. The anterior cruciate ligament (ACL) is known to have a poor wound healing capacity, whereas other ligaments outside of the knee joint capsule such as the medial collateral ligament (MCL) apparently heal more easily. Plasmin has been identified as a major component in the synovial fluid that varies among patients. The aim of this study was to test whether plasmin, a component of synovial fluid, could be a main factor responsible for the poor wound healing capacity of the ACL. Methods. The effects of increasing concentrations of plasmin (0, 0.1, 1, 10, and 50 µg/ml) onto the wound closing speed (WCS) of primary ACL-derived ligamentocytes (ACL-LCs) were tested using wound scratch assay and time-lapse phase-contrast microscopy. Additionally, relative expression changes (quantitative PCR (qPCR)) of major LC-relevant genes and catabolic genes were investigated. The positive controls were 10% fetal calf serum (FCS) and platelet-derived growth factor (PDGF). Results. WCS did not differ significantly among no plasmin versus each of the tested concentrations (six donors). The positive controls with PDGF and with FCS differed significantly from the negative controls. However, we found a trend demonstrating that higher plasmin concentrations up-regulate the expression of matrix metalloproteinase 13 (MMP13), 3 (MMP3), and tenomodulin (TNMD). Conclusion. The clinical relevance of this study is the possibility that it is not solely the plasmin, but also additional factors in the synovial fluid of the knee, that may be responsible for the poor healing capacity of the ACL. Cite this article: Bone Joint Res 2020;9(9):543–553

Aims. The aim of this prospective multicentre study was to describe trends in length of stay and early complications and readmissions following unicompartmental knee arthroplasty (UKA) performed at eight different centres in Denmark using a fast-track protocol and to compare the length of stay between centres with high and low utilization of UKA. Methods. We included data from eight dedicated fast-track centres, all reporting UKAs to the same database, between 2010 and 2018. Complete ( > 99%) data on length of stay, 90-day readmission, and mortality were obtained during the study period. Specific reasons for a length of stay of > two days, length of stay > four days, and 30- and 90-day readmission were recorded. The use of UKA in the different centres was dichotomized into ≥ 20% versus < 20% of arthroplasties which were undertaken being UKAs, and ≥ 52 UKAs versus < 52 UKAs being undertaken annually. Results. A total of 3,927 procedures were included. Length of stay (mean 1.1 days (SD 1.1), median 1 (IQR 0 to 1)) was unchanged during the study period. The proportion of procedures with a length of stay > two days was also largely unchanged during this time. The percentage of patients discharged on the day of surgery varied greatly between centres (0% to 50% (0 to 481)), with centres with high UKA utilization (both usage and volume) having a larger proportion of same-day discharges. The 30- and 90-day readmissions were 166 (4.2%) and 272 (6.9%), respectively; the 90-day mortality was 0.08% (n = 3). Conclusion. Our findings suggest general underutilization of the potential for quicker recovery following UKA in a fast-track setup. Cite this article: Bone Joint J 2020;102-B(9):1167–1175

Background. The purpose of this multi-center, randomized clinical trial was to compare static and articulating spacers in the treatment of PJI complicating total knee arthroplasty TKA. Methods. 68 Patients treated with two-stage exchange arthroplasty were randomized to either a static (32 patients) or an articulating (36 patients) spacer. A power analysis determined that 28 patients per group were necessary to detect a 13º difference in range of motion between groups. Six patients were excluded after randomization, six died, and seven were lost to follow-up prior to two years. Results. Patients in the static group had a hospital length of stay that was one day greater than the articulating group (6.1 vs. 5.1 days; p=0.032); no other differences were noted perioperatively. At a mean 3.5 years (range, 2.0 to 6.4 years), 49 patients were available for evaluation. Mean motion arc in the articulating group was 113.0º compared to 100.2º in the static group (p=0.001). The mean Knee Society Score was significantly higher in the articulating cohort (79.4 vs. 69.8 points; p=0.043). Although not significantly different with the sample size studied, static spacers were associated with a greater need for an extensile exposure at the time of reimplantation (16.7% vs. 3.8%) and a higher rate of reoperation (33.3% vs. 12.0%). Conclusions. Articulating spacers provided significantly greater range of motion and better clinical outcomes scores. Static spacers also appeared to affect early postoperative rehabilitation, as evidenced by a longer hospital stay following removal of the infected implant and were associated with a trend towards a greater need for extensile exposures at the time of reimplantation. Further, while it has been commonly believed that static spacers would improve infection control, there was no difference in the failure rate secondary to reinfection and there was a trend towards higher risk of reoperation in patients who received a static spacer. When the soft tissue envelope allows and if there is adequate bony support, an articulating spacer is associated with improved outcomes. For figures, tables, or references, please contact authors directly

Background. As the number of total knee arthroplasties (TKA) being performed continues to increase, the number of potential failures requiring revision surgery would also be expected to increase. This study analyzed the trends in revision TKA (rTKA) from 2009 to 2016. Methods. The Nationwide Inpatient Sample (NIS) database was used to identify all rTKA by International Classification of Diseases, Ninth Revision (ICD-9) and Tenth Revision (ICD-10) codes. The diagnoses leading to revision, revision costs, patient and hospital characteristics, and major inpatient complications were compared between 2009 and 2016. Multivariate logistic regression analyses were used to calculate odds ratios (OR) for complications. Results. A total of 453,770 rTKA were performed between 2009 and 2016 (Table 1). The incidence of rTKA between 2009 and 2016 decreased by 4.3% among all age groups and decreased 5.9% in those over 65 years of age. The mean age at revision remained unchanged at 65 years, the mean Length of Stay (LOS) decreased 19.5% from 4.1 to 3.3 days (p<0.001), and the mean hospital costs increased 18.7% from $23,103 to $27,427 (p<0.001). Male to Female ratio remained unchanged with Females making up 58% of rTKA. The rTKA patients in 2016 versus 2009 had significantly lower odds of requiring a blood transfusion (OR 0.26, p<0.001). The rate of myocardial infarction remained unchanged in 2016 versus 2009 (4.1% vs. 4.0%, p=0.52), as did mortality (0.1% vs. 0.2%, p=0.089). Patients in 2016 were significantly less likely to be discharged to a skilled nursing facility (SNF) (26.5% in 2016 vs. 31.6% in 2009, p<0.001). A significantly larger share of rTKA were performed in urban teaching hospitals in 2016 (66.6% in 2016 vs. 41.5% in 2009, p<0.001). Mechanical loosening remained the most common reason for rTKA and increased from 19.7% in 2009 to 28.4% in 2016. Infection remained the second most common reason for rTKA (14.7% in 2009 vs. 12.2% in 2016). Instability was the third most common reason for revision in 2016 (10.7%) but direct comparison with 2009 could not be made since ICD-9 did not include this diagnosis. When comparing 2009 to 2014, an increase in revision rates was noted. Upon inclusion of 2015 and 2016 data, a decrease is noted. The primary limitation of this study is the challenge faced when comparing results from before and after the October 2015 transition of ICD-9 to ICD-10 codes. Conclusions. The incidence of rTKA had decreased slightly between 2009 and 2016 even while the volume of primary TKA continued to rise. Implant loosening became increasingly prevalent as a reason for revision and infection continued to plague patients after TKA. Positive trends were noted, such as decreased rates of blood transfusion, LOS and rates of discharge to SNF. Still, the revision burden remains large, costing approximately $1.4 billion annually and we must continue to attempt to improve outcomes in this patient population. For figures, tables, or references, please contact authors directly

Introduction. The ideal type of total knee arthroplasty (TKA) prosthesis remains a debatable topic with many different options available. Uncemented TKA has been a viable option due to its decreased operating room (OR) time but also because of its proposed improved long term fixation. Unfortunately, in the past uncemented TKA was associated with increased blood loss. Surgical technique and perioperative treatments have changed since these original studies and tranexamic acid (TXA) has become the gold standard for TKA blood loss management. The objective of this study was to evaluate if there was a difference in hemoglobin and hematocrit change, along with blood loss volume during surgery between cemented and cementless TKA when modern blood loss techniques are utilized. Methods. We retrospectively reviewed data from TKAs performed by three high volume surgeons between 2016 and 2019. We excluded bilateral TKA, revisions, hardware removal intraoperatively and other indications for TKA than primary OA. Power analysis determined 85 patients in both the cementless and cemented TKA groups. Patients were matched 1:1 for age, sex, BMI and surgeon. Use of TXA, intraoperative blood loss, differences in hemoglobin and hematocrit pre- and postoperatively days one, two, and three were recorded. Continuous variables were analyzed using T-tests and categorical variables were evaluated using Chi-squared tests. Results. No significant difference was observed between the cementless and cemented groups for hemoglobin (p=0.214), hematocrit (p=0.164), or intraoperative blood loss volume (p=0.343). A trend towards significantly shorter OR time was seen in the cementless group (p = 0.058). Conclusion. With modern TKA surgery, including the use of TXA, there is no difference in perioperative blood loss between cemented and cementless TKA. Unlike previous studies, the use of modern blood loss salvage techniques in conjunction with cementless TKA fixation, does not result in more blood loss during the perioperative period

Aims

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).