Aim. Antimicrobial peptides occur naturally in our intrinsic immune system. PLG0206 is a novel, engineered, 24-amino acid peptide which has broad-spectrum antimicrobial activity, including in biofilm and against multi-drug resistant pathogens (1,2). This is the first clinical study to evaluate the safety and tolerability of PLG0206 when administered via an irrigation solution in patients with periprosthetic joint infections (PJI) following total knee arthroplasty (TKA) during debridement, antibiotics, and implant retention (DAIR). Secondary objectives were to evaluate pharmacokinetics (PK), biomarkers and initial clinical efficacy at one year post-DAIR procedure. Method. This prospective, multicenter, open-label, interventional study assessed two dose levels of PLG0206. Fourteen patients underwent revision for PJI after TKA. At the end of debridement, they received a single intra-articular irrigation of PLG0206 into the wound cavity lasting 15 minutes at concentrations of 3 mg/mL (n=7) or 10 mg/mL (n=7). Patients received post-operative care and intravenous/oral antimicrobial therapy as per their institutional guidelines. Patients were monitored for safety and signs of relapse or persistent infection for 12 months post study drug administration and PK and blood biomarkers were assessed. Results. All patients completed their final study assessment at Day 365. Over the 1-year follow-up, only one recurrence (7%) was noted at Day 169 in the low-dose cohort. Following dosing, nine patients (64.3%) had limited systemic exposure; maximum plasma concentration occurred 1-hour post-administration and declined rapidly to undetectable levels by 24 hours following treatment in all patients. The incidence of drug related treatment-emergent adverse events (TEAEs) was low. Two patients, both in the higher dose cohort, experienced a transient drug related TEAE; one of hypertransaminasaemia and one of neuralgia. Both events were moderate in severity and resolved within two weeks of onset. Conclusions. A single 15-minute irrigation of PLG0206 into the wound cavity of patients undergoing a DAIR procedure for PJI following TKA, is safe and well tolerated by patients. This new antimicrobial peptide offers a promising therapeutic option in musculoskeletal infection. The initial clinical efficacy is encouraging but now needs to be investigated in a much larger clinical trial

Aim. Periprosthetic joint infection (PJI) is one of the main reasons for revision surgery after primary unicompartmental knee arthroplasty (UKA), total knee arthroplasty (TKA) or total hip arthroplasty (THA). Currently the MSIS and EBJIS criteria sets are considered to be the gold standards in determining PJI. These criteria sets are complex and contain tests that are time-consuming and many are rather costly. Therefore, further research is indicated to find a simpler but equally reliable diagnostic test. In this study we evaluated the additional value of calprotectine measurement in synovial fluid in patients undergoing hip and knee (revision) arthroplasty following routine work-up. Method. In a retrospective cohort study, we analyzed 182 synovial fluid samples from 143 patients with suspected PJI after UKA, TKA, THA or revision arthroplasty. Twenty-six of those cases were classified as PJI according to the MSIS and EBJIS criteria. Subsequently, synovial calprotectin was determined, using a lateral flow assay and two cut-off thresholds of ≥14 mg/L and ≥50 mg/L. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of synovial calprotectin was determined. Results. When applying the MSIS and EBJIS criteria and a calprotectin level ≥14 mg/L, synovial calprotectin revealed an area under the curve of 0.96 (95% CI 0.90-1.00), with 92.3% sensitivity and 100% specificity. The PPV and NPV were 100% and 92.9% respectively. When applying the MSIS and EBJIS criteria and a calprotectin level ≥ 50 mg/L, synovial calprotectin revealed an area under the curve of 0.94 (95% CI 0.87-1.00), with 88.5% sensitivity and 100% specificity. The PPV and NPV were 100% and 89.7% respectively. Conclusions. The value of calprotectin in synovial fluid gives valuable information with a single test result, resulting in high predictive value in the diagnosis of PJI after hip or knee arthroplasty and should seriously be considered as part of PJI diagnostics in an outpatient clinical setting. The high specificity can help rule in patients that are suspected of PJI. Therefor this test can be helpful in a preop diagnostic work-up to avoid unnecessary revisions in patients with well-placed and well-fixed arthroplasties with a suspected PJI. These conclusions are independent of which criteria set was used as a gold standard

Aim. Periprosthetic joint infection (PJI) is one of the most frequent and devastating complications of total knee arthroplasty (TKA). Accurate diagnosis and proper treatment are essential to prevent functional loss and progression to systemic infection. However, the correct diagnosis of PJI is still a challenge since there is no accurate diagnostic method and the existing diagnostic criteria are based on serological, histological and microbiological tests that are imprecise and time-consuming. Recently, it was demonstrated that cell-free DNA is increased in the synovial fluid of patients with PJI. Therefore, this study aims to evaluate a new point-of-care methodology for quantifying free DNA in synovial fluid. Method. A prospective study was carried out with patients undergoing TKA revision surgery, from whom it was possible to collect synovial fluid (SF) during the surgical procedure. Cell-free DNA quantification was performed directly from the SF, using a portable fluorimeter. Sensitivity, specificity and receiver operating characteristic (ROC) curve were calculated. Results. Fifty-four patients were included in the study, of which 25 were diagnosed with PJI. Cell-free DNA levels measured immediately after collection were increased in the synovial fluid of patients with PJI (26.3 ± 14.8) in comparison with the uninfected group (4.6 ng/ml ± 3.8, p< 0.0001). The area under the receiver operating characteristic curve (AUC ROC) was 0.981 (95% CI 0.914 to 0.999). Conclusions. From the results presented, we can conclude that the quantification of free DNA with a portable fluorimeter proved to be a test with high sensitivity and specificity for the diagnosis of PJI

Aim. As the number of performed total hip arthroplasties (THA) and total knee arthroplasties (TKA) has increased over the years, revision surgeries are expected to increase as well. Revision surgeries are associated with a longer operating room time, prolonged length of stay (LOS), and more frequent complications. Postoperative hematomas are a major reason for wound healing disturbances and periprosthetic joint infections (PJI). We aimed to systematically assess the use and safety of a microporous polysaccharide hemosphere (MPH) in revision THA and TKA. We focused on the risk reduction of further revision surgeries in case of wound healing disorders and hematoma, transfusion of packed red blood cells (PRBC), loss of hemoglobin (hb) and mean LOS following the use of MPH. Method. Our prospective study includes 89 patients who underwent revision surgery after THA and TKA with application of MPH and were compared to 102 patients who did not receive MPH and underwent revision surgery after THA and TKA. Five grams of MPH. 1. were applied periarticular before fascia closure and to the subcutaneous soft tissue. The follow-up was conducted in daily clinical visits during the inpatient stay and three months postoperatively in our outpatient clinic. Repeated revision surgery was performed in case of prolonged secretion (>10 days) or clinical suspicion of infection. After matching the cohorts the outcomes were statistically analyzed using paired methods. Results. A significantly lower odds ratio for repeat revisions was found for the MPH cohort (OR=0.312; 95%-CI 0.090, 0.893; p=0.027). Differences between pre- and postoperative hb levels, LOS and transfusions of PRBC did not reach significance. No intra- or postoperative complications to MPH occurred. Moreover, no infection relapse occurred after applying MPH. Conclusions. Routine use of MPH in revision arthroplasty management after TKA and THA appears to be safe and an effective way to support hemostasis, with no observed adverse events related to MPH use. There were noticeably less hematomas and revision surgeries in the MPH group. 1. Arista BD, Franklin Lakes, NJ, USA

Aim. This study aimed to externally validate promising preoperative PJI prediction models in a recent, multinational European cohort. Method. Three preoperative PJI prediction models (by Tan et al., Del Toro et al., and Bülow et al.) which previously demonstrated high levels of accuracy were selected for validation. A multicenter retrospective observational analysis was performed of patients undergoing total hip arthroplasty (THA) and total knee arthroplasty (TKA) between January 2020 and December 2021 and treated at centers in the Netherlands, Portugal, and Spain. Patient characteristics were compared between our cohort and those used to develop the prediction models. Model performance was assessed through discrimination and calibration. Results. A total of 2684 patients were included of whom 60 developed a PJI (2.2%). Our patient cohort differed from the models’ original cohorts in terms of demographic variables, procedural variables, and the prevalence of comorbidities. The c-statistics for the Tan, Del Toro, and Bülow models were 0.72, 0.69, and 0.72 respectively. Calibration was reasonable, but precise percentage estimates for PJI risk were most accurate for predicted risks up to 3-4%; the Tan model overestimated risks above 4%, while the Del Toro model underestimated risks above 3%. Conclusions. In this multinational cohort study, the Tan, Del Toro, and Bülow PJI prediction models were found to be externally valid for classifying high risk patients for developing a PJI. These models hold promise for clinical application to enhance preoperative patient counseling and targeted prevention strategies. Keywords. Periprosthetic Joint Infection (PJI), High Risk Groups, Prediction Models, Validation, Infection Prevention

Introduction. This study aimed to evaluate the effectiveness of a novel intraoperative navigation platform for total knee arthroplasty (TKA) in restoring native knee joint kinematics and strains in the medial collateral ligament (MCL) and lateral collateral ligament (LCL) during squatting motions. Method. Six cadaver lower limbs underwent computed tomography scans to design patient-specific guides. Using these scans, bony landmarks and virtual single-line collateral ligaments were identified to provide intraoperative real-time feedback, aided in bone resection, implant alignment, tibiofemoral kinematics, and collateral ligament elongations, using the navigation platform. The specimens were subjected to squatting (35°-100°) motions on a physiological ex vivo knee simulator, maintaining a constant 110N vertical ankle load regulated by active quadriceps and bilateral hamstring actuators. Subsequently, each knee underwent a medially-stabilized TKA using the mechanical alignment technique, followed by a retest under the same conditions used preoperatively. Using a dedicated wand, MCL and LCL insertions—anterior, middle, and posterior bundles—were identified in relation to bone-pin markers. The knee kinematics and collateral ligament strains were analyzed from 3D marker trajectories captured by a six-camera optical system. Result. Both native and TKA conditions demonstrated similar patterns in tibial valgus orientation (Root Mean Square Error (RMSE=1.7°), patellar flexion (RMSE=1.2°), abduction (RMSE=0.5°), and rotation (RMSE=0.4°) during squatting (p>0.13). However, a significant difference was found in tibial internal rotation between 35° and 61° (p<0.045, RMSE=3.3°). MCL strains in anterior (RMSE=1.5%), middle (RMSE=0.8%), and posterior (RMSE=0.8%) bundles closely matched in both conditions, showing no statistical differences (p>0.05). Conversely, LCL strain across all bundles (RMSE<4.6%) exhibited significant differences from mid to deep flexion (p<0.048). Conclusion. The novel intraoperative navigation platform not only aims to achieve planned knee alignment but also assists in restoring native knee kinematics and collateral ligament behavior through real-time feedback. Acknowledgment. This study was funded by Medacta International (Castel San Pietro, Switzerland)

Introduction. Distal femur fractures around a total knee arthroplasty (TKA) are a growing problem for orthopaedic surgeons. The purpose of this study was to identify risks of reoperation for nonunion following open reduction and internal fixation of TKA periprosthetic distal femur fractures (PDFF). Method. Patients with PDFF (AO 33A-C[VB1, C1, D1], Su types 1-3) managed operatively with open reduction and internal fixation (ORIF) were retrospectively reviewed. Exclusion criteria were acute management with a distal femur replacement, less than 6 months of follow-up, and lack of injury or follow-up radiographs. The primary outcome measure was reoperation to achieve bony union. Comparisons were made between cases that did and did not require a reoperation to achieve union. Univariate analysis was used to identify factors to be analyzed in multivariate analysis to determine independent risk factors for the primary outcome. Result. A total of 77 patients met inclusion criteria. Union rate was 69/77 (89.6%). There were no differences between the groups for age, sex, BMI, comorbidities, Su classification, open injury, or mechanism of injury. Multivariate analysis identified risks for nonunion including post-operative malalignment (OR 1.41; CI 1.20-1.64; p<0.001), notching pre-operatively (OR 1.22; CI 1.04-1.42; p=0.012), presence of screws through fracture line (OR 1.28; CI 1.17-1.39; p<0.001), plate length <12 holes (OR 1.16; CI 1.02-1.33; p=0.024) and screw density greater than 0.4 (OR 2.18; CI 1.25-3.78; p=0.006). Conclusion. The reoperation rate to promote union was 10.4%. The study identified post-operative malalignment, notching pre-operatively, presence of screws through fracture line, plate length <12 holes, and proximal screw density greater than 40% as independent risk factors for nonunion

Purpose. To compare postoperative clinical outcomes between posterior cruciate ligament (PCL) retaining and resecting total knee arthroplasty (TKA) using same cruciate-substituting (CS) inserts, and to elucidate the clinical relevance of the residual PCL in cruciate-retaining TKA, considering intraoperative influence factors, such as the posterior tibial slope, posterior condylar offset, joint gap, joint balance, and joint laxity. Methods. A total of 64 consecutive knees (44 patients) were enrolled in this study and divided into following two groups: 39 knees underwent PCL-retaining TKA group (CR group), and 25 underwent PCL-resecting TKA group (CS group). Preoperative patients’ demographic data and one-year postoperative clinical outcomes including range of motion, the Knee Injury and Osteoarthritis Outcome Score (KOOS), the Japanese Orthopaedic Association (JOA) score, and Forgotten Joint Score-12 (FJS-12) were compared between two groups. Results. Regarding range of motion, the average preoperative ROM was -14.3/120.0 degrees in the CR group and improved to -2.4/118.9 degrees postoperatively. In the CS group, the average preoperative ROM was -7.5/130 degrees and changed to -2.2/122.4 degrees postoperatively. There was no significant difference in the postoperative ROM between the groups (P=0.16). The KOOS (from 47.1 to 69.5 in CR group; from 41.1 to 70.8 in CS group) and JOA scores (from 59.2 to 76.9 in CR group; from 55.6 to 80.8 in CS group) were significantly improved postoperatively in both groups (P < 0.01). However, there was no significance in these postoperative scores between two groups (P = 0.09). There was also no significance in FJS-12 between two groups (70.3 in CR group and 66.9 in CS group; P=0.53). Conclusions. Residual PCL in TKA with a CS insert would not impact one-year postoperative clinical outcomes including KOOS, JOA, and FJS-12

Introduction. There is a lack of evidence-based treatments for patients with chronic pain after total knee arthroplasty (TKA). It is well-established that knee extensor and flexor muscle strength are markedly impaired following TKA, but no studies have examined muscle strength and power in patients with chronic pain after TKA. Therefore, the aim was to investigate if neuromuscular exercises and pain neuroscience education (PNE) were superior to PNE alone for improvement of muscle strength and power in patients with chronic pain after TKA. Method. This report presents the exploratory analysis of a randomized controlled trial (NCT03886259). Participants with chronic moderate-to-severe average daily pain intensity and no signs of prosthesis failure at least one year after primary TKA were included. Participants were randomized to receive either supervised neuromuscular exercise and PNE or the same PNE sessions alone. The outcomes were changes from baseline to 12-months for peak leg extension power and maximum muscle strength, measured during maximal voluntary isometric contractions, for the knee extensors and flexors. Result. Sixty-nine participants (age 62.2±7.2, 40 females) were included. No between-group differences were observed for peak leg extension power (difference 13.6 Watts, 95% CI -22.2 to 49.3), maximum knee extensor muscle strength (difference -20.9 Newtons, 95% CI -65.8 to 24.0) or maximum knee flexor muscle strength (difference 8.6 Newtons, 95% CI -11.9 to 29.1). Peak leg extension power (26.3 Watts, 95% CI 4.3 to 48.3) and maximum knee flexor muscle strength (19.7 Newtons, 95% CI 7.6 to 31.9) improved significantly in the neuromuscular exercise and PNE group with no significant improvements observed in the PNE alone group. Conclusion. Neuromuscular exercise and PNE did not improve muscle strength and power compared to PNE alone in patients with chronic pain after TKA. Acknowledgements. This study was funded by the Danish Rheumatism Association, the Svend Andersen Foundation and Lions Club Denmark

Aims. Distal femoral osteotomies (DFOs) are commonly used for the correction of valgus deformities and lateral compartment osteoarthritis. However, the impact of a DFO on subsequent total knee arthroplasty (TKA) function remains a subject of debate. Therefore, the purpose of this study was to determine the effect of a unilateral DFO on subsequent TKA function in patients with bilateral TKAs, using the contralateral knee as a self-matched control group. Methods. The inclusion criteria consisted of patients who underwent simultaneous or staged bilateral TKA after prior unilateral DFO between 1972 and 2023. The type of osteotomy performed, osteotomy hardware fixation, implanted TKA components, and revision rates were recorded. Postoperative outcomes including the Forgotten Joint Score-12 (FJS-12), Tegner Activity Scale score, and subjective knee preference were also obtained at final follow-up. Results. A total of 21 patients underwent bilateral TKA following unilateral DFO and were followed for a mean of 31.5 years (SD 11.1; 20.2 to 74.2) after DFO. The mean time from DFO to TKA conversion was 13.1 years (SD 9.7) with 13 (61.9%) of DFO knees converting to TKA more than ten years after DFO. There was no difference in arthroplasty implant systems employed in both the DFO-TKA and TKA-only knees (p > 0.999). At final follow-up, the mean FJS-12 of the DFO-TKA knee was 62.7 (SD 36.6), while for the TKA-only knee it was 65.6 (SD 34.7) (p = 0.328). In all, 80% of patients had no subjective knee preference or preferred their DFO-TKA knee. Three DFO-TKA knees and two TKA-only knees underwent subsequent revision following index arthroplasty at a mean of 12.8 years (SD 6.9) and 8.5 years (SD 3.8), respectively (p > 0.999). Conclusion. In this self-matched study, DFOs did not affect subsequent TKA function as clinical outcomes, subjective knee preference, and revision rates were similar in both the DFO-TKA and TKA-only knees at mean 32-year follow-up. Cite this article: Bone Jt Open 2024;5(11):1013–1019

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The mechanism by which synovial fluid (SF) kills bacteria has not yet been elucidated, and a better understanding is needed. We sought to analyze the antimicrobial properties of exogenous copper in human SF against Staphylococcus aureus.

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While residual fixed flexion deformity (FFD) in unicompartmental knee arthroplasty (UKA) has been associated with worse functional outcomes, limited evidence exists regarding FFD changes. The objective of this study was to quantify FFD changes in patients with medial unicompartmental knee arthritis undergoing UKA, and investigate any correlation with clinical outcomes.

Aims. Day-case success rates after primary total hip arthroplasty (THA), total knee arthroplasty (TKA), and medial unicompartmental knee arthroplasty (mUKA) may vary, and detailed data are needed on causes of not being discharged. The aim of this study was to analyze the association between surgical procedure type and successful day-case surgery, and to analyze causes of not being discharged on the day of surgery when eligible and scheduled for day-case THA, TKA, and mUKA. Methods. A multicentre, prospective consecutive cohort study was carried out from September 2022 to August 2023. Patients were screened for day-case eligibility using well defined inclusion and exclusion criteria, and discharged when fulfilling predetermined discharge criteria. Day-case eligible patients were scheduled for surgery with intended start of surgery before 1.00 pm. Results. Of 6,142 primary hip and knee arthroplasties, eligibility rates for day-case surgery were 34% for THA (95% CI 32% to 36%), 34% for TKA (95% CI 32% to 36%), and 52% for mUKA (95% CI 49% to 55%). Surgery before 1.00 pm was achieved in 85% of eligible patients. The day-case success rate among patients with surgery before 1.00 pm was 59% (95% CI 55% to 62%) for THA, 61% (95% CI 57% to 65%) for TKA, and 72% (95% CI 68% to 76%) for mUKA. Overall day-case success rates (eligible and non-eligible) were 19% (95% CI 17% to 20%) for THA, 20% (95% CI 18% to 21%) for TKA, and 42% (95% CI 39% to 45%) for mUKA. Adjusted analysis confirmed higher day-case success in eligible mUKA patients (odds ratio 1.9 (1.6 to 2.3)) compared to TKA and THA patients. Primary causes for day-case failure were mobilization issues (9% to 12% between procedures), prolonged spinal anaesthesia (4% to 9%), and postoperative nausea and vomiting (PONV) (4% to 14%). Conclusion. THA and TKA patients showed comparable eligibility (34%) with similar day-case success rates (59 to 61%), whereas mUKA patients demonstrated higher eligibility (52%) and day-case success (72%). Mobilization issues, prolonged spinal anaesthesia, and PONV were the most frequent causes for not being discharged

Aims. This multicentre retrospective observational study’s aims were to investigate whether there are differences in the occurrence of radiolucent lines (RLLs) following total knee arthroplasty (TKA) between the conventional Attune baseplate and its successor, the novel Attune S+, independent from other potentially influencing factors; and whether tibial baseplate design and presence of RLLs are associated with differing risk of revision. Methods. A total of 780 patients (39% male; median age 70.7 years (IQR 62.0 to 77.2)) underwent cemented TKA using the Attune Knee System) at five centres, and with the latest radiograph available for the evaluation of RLL at between six and 36 months from surgery. Univariate and multivariate logistic regression models were performed to assess associations between patient and implant-associated factors on the presence of tibial and femoral RLLs. Differences in revision risk depending on RLLs and tibial baseplate design were investigated with the log-rank test. Results. The conventional and novel Attune baseplates were used in 349 (45%) and 431 (55%) patients, respectively. At a median follow-up of 14 months (IQR 11 to 25), RLLs were present in 29% (n = 228/777) and 15% (n = 116/776) of the tibial and femoral components, respectively, and were more common in the conventional compared to the novel baseplate. The novel baseplate was independently associated with a lower incidence of tibial and femoral RLLs (both regardless of age, sex, BMI, and time to radiograph). One- and three-year revision risk was 1% (95% CI 0.4% to 1.9%)and 6% (95% CI 2.6% to 13.2%), respectively. There was no difference between baseplate design and the presence of RLLs on the the risk of revision at short-term follow-up. Conclusion. The overall incidence of RLLs, as well as the incidence of tibial and femoral RLLs, was lower with the novel compared to the conventional tibial Attune baseplate design, but higher than in the predecessor design and other commonly used TKA systems. Cite this article: Bone Joint J 2024;106-B(11):1240–1248

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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.

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This study aimed to investigate the optimal sagittal positioning of the uncemented femoral component in total knee arthroplasty to minimize the risk of aseptic loosening and periprosthetic fracture.

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The aim of this study was to determine whether obesity had a detrimental effect on the long-term performance and survival of medial unicompartmental knee arthroplasties (UKAs).

Aims. The aims were to assess whether joint-specific outcome after total knee arthroplasty (TKA) was influenced by implant design over a 12-year follow-up period, and whether patient-related factors were associated with loss to follow-up and mortality risk. Methods. Long-term follow-up of a randomized controlled trial was undertaken. A total of 212 patients were allocated a Triathlon or a Kinemax TKA. Patients were assessed preoperatively, and one, three, eight, and 12 years postoperatively using the Oxford Knee Score (OKS). Reasons for patient lost to follow-up, mortality, and revision were recorded. Results. A total of 94 patients completed 12-year functional follow-up (62 females, mean age 66 years (43 to 82) at index surgery). There was a clinically significantly greater improvement in the OKS at one year (mean difference (MD) 3.0 (95% CI 0.4 to 5.7); p = 0.027) and three years (MD 4.7 (95% CI 1.9 to 7.5); p = 0.001) for the Triathlon group, but no differences were observed at eight (p = 0.331) or 12 years’ (p = 0.181) follow-up. When assessing the OKS in the patients surviving to 12 years, the Triathlon group had a clinically significantly greater improvement in the OKS (marginal mean 3.8 (95% CI 0.2 to 7.4); p = 0.040). Loss to functional follow-up (53%, n = 109/204) was independently associated with older age (p = 0.001). Patient mortality was the major reason (56.4%, n = 62/110) for loss to follow-up. Older age (p < 0.001) and worse preoperative OKS (p = 0.043) were independently associated with increased mortality risk. An age at time of surgery of ≥ 72 years was 75% sensitive and 74% specific for predicting mortality with an area under the curve of 78.1% (95% CI 70.9 to 85.3; p < 0.001). Conclusion. The Triathlon TKA was associated with clinically meaningful greater improvement in knee-specific outcome when compared to the Kinemax TKA. Loss to follow-up at 12 years was a limitation, and studies planning longer-term functional assessment could limit their cohort to patients aged under 72 years. Cite this article: Bone Jt Open 2024;5(10):911–919

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This study examined windswept deformity (WSD) of the knee, comparing prevalence and contributing factors in healthy and osteoarthritic (OA) cohorts.

Aims. The outcomes of patients with unexpected positive cultures (UPCs) during revision total hip arthroplasty (THA) and total knee arthroplasty (TKA) remain unknown. The objectives of this study were to establish the prevalence and infection-free implant survival in UPCs during presumed aseptic single-stage revision THA and TKA at mid-term follow-up. Methods. This study included 297 patients undergoing presumed aseptic single-stage revision THA or TKA at a single treatment centre. All patients with at least three UPCs obtained during revision surgery were treated with minimum three months of oral antibiotics following revision surgery. The prevalence of UPCs and causative microorganisms, the recurrence of periprosthetic joint infections (PJIs), and the infection-free implant survival were established at minimum five years’ follow-up (5.1 to 12.3). Results. Of the 297 patients undergoing aseptic revisions, 37 (12.5%) had at least three UPCs obtained during surgery. The UPC cohort included 23 males (62.2%) and 14 females (37.8%), with a mean age of 71.2 years (47 to 82). Comorbidities included smoking (56.8%), hypertension (48.6%), diabetes mellitus (27.0%), and chronic renal impairment (13.5%). The causative microorganisms included Staphylococcus epidermidis (49.6%), Bacillus species (18.9%), Micrococcus species (16.2%), and Cutibacterium acnes (16.2%). None of the study patients with UPCs developed further PJIs or required further surgical intervention during follow-up. Conclusion. The prevalence of UPCs during presumed aseptic revision THA and TKA was 12.5%. The most common causative microorganisms were of low virulence, and included S. epidermidis, Bacillus species, Micrococcus species, and C. acnes. Microorganism-specific antibiotic treatment for minimum three months’ duration of UPCs in presumed aseptic revision arthroplasty was associated with excellent infection-free implant survival at mid-term follow-up. Cite this article: Bone Jt Open 2024;5(10):832–836