Purpose: To examine whether psychological factors are associated with chronic postoperative pain ≥12 months after total knee arthroplasty (TKA), given that ∼10% of patients report persistent pain despite otherwise successful surgery, and psychological influences are proposed contributors. Methods: A systematic review was conducted following PRISMA guidelines, including adults undergoing primary or revision TKA with postoperative pain assessed at a minimum of one year. Searches were performed in MEDLINE and Embase. Risk of bias was evaluated using the Newcastle–Ottawa scale. The protocol was registered with PROSPERO (CRD42024620401). Due to substantial heterogeneity in the studies, findings were synthesised narratively. Results: Thirty-seven studies met eligibility criteria. Twelve psychological factors were assessed across studies, most frequently depressive symptoms, pain catastrophising, and anxiety. Results were inconsistent, and no psychological factor showed a reproducible association with long-term postoperative pain across studies. Expectations were the only factor consistently associated with pain outcomes, while self-efficacy showed no association. Other factors, such as kinesiophobia and psychological distress, were examined in too few studies to support firm interpretation. Most studies demonstrated a moderate risk of bias, primarily due to reliance on self-reported measures and lack of non-exposed comparison cohorts. Conclusion: Substantial heterogeneity across studies limits firm conclusions regarding the influence of psychological factors on chronic postoperative pain one year after TKA. Patient expectations may play a meaningful role, whereas self-efficacy appears unrelated. Overall, most patients experienced pain improvement regardless of psychological profile. Standardised assessment methods are needed to clarify these associations and guide clinical practice.

Background and purpose: Hip migration is a common complication in children with cerebral palsy (CP). Although spasticity has long been considered a contributing factor, muscle-specific associations with hip migration remain unclear. We aimed to investigate whether assessed hip spasticity was associated with hip displacement risk in non-ambulant children with CP. Methods: In this population-based cohort study using Danish Cerebral Palsy Follow-Up Program (CPOP) data, children classified as Gross Motor Function Classification System (GMFCS) levels IV–V with at least 1 hip radiograph were included. Pathological hip migration was defined as migration percentage (MP) ≥ 30%. Spasticity was assessed using the Modified Ashworth Scale (MAS) for hip adductors, flexors, and extensors. Overall hip spasticity was defined as summed MAS (0, 1–3, 4–6, 7–9). Cumulative incidence was estimated with death as a competing event, and associations were evaluated using Fine–Gray regression adjusted for GMFCS level. Results: 422 children (786 hips) were included; 374 hips (48%) reached MP ≥ 30%, and death occurred as a competing event in 16 patients (25 hips). Higher overall hip spasticity was associated with increased risk of hip migration, with subdistribution hazard ratios (sHRs) of 1.46 (CI 1.05–2.01), 1.77 (CI 1.22–2.58), and 2.53 (CI 1.59–4.02) for MAS 1–3, 4–6, and 7–9, respectively, compared with MAS 0. Adductor spasticity showed the most consistent association with sHRs ranging from 1.44 to 1.97 across MAS categories. Conclusion: In children with CP classified as GMFCS levels IV–V, higher clinically assessed hip spasticity—particularly of the hip adductors—was associated with development of a hip at risk for displacement.

BACKGROUND:The superiority of medial unicompartmental knee arthroplasty (mUKA) versus total knee arthroplasty (TKA) for isolated anteromedial knee osteoarthritis (AMOA) remains a subject of ongoing debate. We present the 2-year results of a multicenter, randomized trial comparing the patient-reported and clinical outcomes of these 2 implant types in the treatment of AMOA. METHODS:This double-blinded superiority trial recruited patients with severe AMOA at 10 arthroplasty centers and randomized them to undergo either mUKA or TKA. The primary outcome was the average improvement in the Oxford Knee Score (OKS) over 2 years, analyzed by intention-to-treat. A range of patient-reported outcomes served as secondary outcomes. Death, revision, and other reoperations were analyzed as serious adverse events (SAEs). RESULTS:Between September 2017 and March 2021, 350 patients were randomized: 177 (79 female, 98 male; mean age, 67.7 ± 7.5 years) to mUKA and 173 (84 female, 89 male; mean age, 66.7 ± 7.8 years) to TKA. The average 2-year OKS improvement differed by 3.5 points (95% CI, 2.3 to 4.7; p < 0.001) in favor of mUKA, although this difference was below the generally accepted minimal clinically important difference (MCID) of 4 to 5 points. Ten of the 12 secondary outcomes favored mUKA, while the remaining 2 were nonsignificant. The differences in the Forgotten Joint Score (FJS) (14.1; 95% CI, 9.5 to 18.6), range of motion during the first 2 years (7.0°; 95% CI, 5.3° to 8.7°) and at 2 years (5.5°; 95% CI, 3.6° to 7.4°), Knee injury and Osteoarthritis Outcome Score (KOOS) symptoms score (10.3; 95% CI, 7.8 to 12.8), and Short Form-36 (SF-36) bodily pain score (7.6; 95% CI, 4.1 to 11.1) all favored mUKA and reached the MCID. Non-revision reoperations were performed in 4 patients (2.3%) after mUKA and in 12 patients (6.9%) after TKA (9 of the 12 underwent manipulation under anesthesia); the difference was 4.7% (95% CI, 0.2% to 9.8%). There were no differences in the rates of revision or death between the groups. CONCLUSIONS:Averaged over the 2-year follow-up, mUKA demonstrated minor advantages that did not achieve clear clinical superiority on the basis of the OKS difference. However, the FJS, range of motion, KOOS symptoms score, and SF-36 bodily pain score all demonstrated differences in favor of mUKA that were clinically meaningful. The overall findings suggest that mUKA and TKA yield similarly favorable short-term results, with small advantages for mUKA. LEVEL OF EVIDENCE:Therapeutic Level I . See Instructions for Authors for a complete description of levels of evidence.

Background: The superiority of medial unicompartmental knee arthroplasty (mUKA) versus total knee arthroplasty (TKA) for isolated anteromedial knee osteoarthritis (AMOA) remains a subject of ongoing debate. We present the 2-year results of a multicenter, randomized trial comparing the patient-reported and clinical outcomes of these 2 implant types in the treatment of AMOA. Methods: This double-blinded superiority trial recruited patients with severe AMOA at 10 arthroplasty centers and randomized them to undergo either mUKA or TKA. The primary outcome was the average improvement in the Oxford Knee Score (OKS) over 2 years, analyzed by intention-to-treat. A range of patient-reported outcomes served as secondary outcomes. Death, revision, and other reoperations were analyzed as serious adverse events (SAEs). Results: Between September 2017 and March 2021, 350 patients were randomized: 177 (79 female, 98 male; mean age, 67.7 ± 7.5 years) to mUKA and 173 (84 female, 89 male; mean age, 66.7 ± 7.8 years) to TKA. The average 2-year OKS improvement differed by 3.5 points (95% CI, 2.3 to 4.7; p < 0.001) in favor of mUKA, although this difference was below the generally accepted minimal clinically important difference (MCID) of 4 to 5 points. Ten of the 12 secondary outcomes favored mUKA, while the remaining 2 were nonsignificant. The differences in the Forgotten Joint Score (FJS) (14.1; 95% CI, 9.5 to 18.6), range of motion during the first 2 years (7.0°; 95% CI, 5.3° to 8.7°) and at 2 years (5.5°; 95% CI, 3.6° to 7.4°), Knee injury and Osteoarthritis Outcome Score (KOOS) symptoms score (10.3; 95% CI, 7.8 to 12.8), and Short Form-36 (SF-36) bodily pain score (7.6; 95% CI, 4.1 to 11.1) all favored mUKA and reached the MCID. Non-revision reoperations were performed in 4 patients (2.3%) after mUKA and in 12 patients (6.9%) after TKA (9 of the 12 underwent manipulation under anesthesia); the difference was 4.7% (95% CI, 0.2% to 9.8%). There were no differences in the rates of revision or death between the groups. Conclusions: Averaged over the 2-year follow-up, mUKA demonstrated minor advantages that did not achieve clear clinical superiority on the basis of the OKS difference. However, the FJS, range of motion, KOOS symptoms score, and SF-36 bodily pain score all demonstrated differences in favor of mUKA that were clinically meaningful. The overall findings suggest that mUKA and TKA yield similarly favorable short-term results, with small advantages for mUKA. Level of Evidence: Therapeutic Level I . See Instructions for Authors for a complete description of levels of evidence.

AIM:To estimate the prevalence of multiply revised knee arthroplasties in Denmark from 1998 to 2021 and to project the prevalence to 2050. METHODS:Three national Danish registries were queried for primary knee arthroplasties in the period of 1998-2021. A multi-state model was created using sex- and age-stratified proportional hazard functions to estimate the probabilities of receiving a primary arthroplasty, revision or dying. These probabilities were then applied to historical and projected population numbers from Statistics Denmark. Prevalence was defined as the number of revision knees per primary knees. RESULTS:In 2020, the number of knees alive with a primary knee arthroplasty was 101,956 knees. The prevalence of 1st revisions was 53.1 knees per 1000 primary knees, the prevalence of 2nd revisions was 9.5 per 1000 primary knees, the prevalence of 3rd revisions was 2.6 per 1000 primary knees, and the prevalence of 4th revisions was 1.4 per 1000 primary knees. In 2050, the number of knees alive with a primary knee arthroplasty was projected to increase 48%, while the prevalence of 1st revisions, 2nd revisions, 3rd revisions and ≥4th revisions was projected to increase 30.1%, 30.1%, 54%, and 114%. CONCLUSION:For knees that have been revised, we project large increases in the prevalence especially for knees that have been revised at least three times. A high proportion of knees with a revision knee arthroplasty in 2050 will be in patients above 80 years of age. Our model can be used in other populations to make future projections.

BACKGROUND AND PURPOSE:The aim of our study was to identify the absolute incidence and implant survival probability of multiply revised knee arthroplasties in Norway and Denmark from 1998 to 2021. METHODS:This was an observational study of primary and revision knee arthroplasties reported prospectively in Norway and Denmark. The nationwide registers in Norway and Denmark were utilized. After identification of all primary procedures reported from 1998 to 2021, revision procedures were identified. Probabilities of implant survival were calculated using Kaplan-Meier methods. A multiply revised knee arthroplasty was defined as at least 3 revisions of a primary knee arthroplasty. RESULTS:The proportion of third revisions was 0.4% in both Denmark (621/159,343) and Norway (404/105,192). The 16-year implant survival of third revisions was 57% (CI 52-62) in Denmark and 54% (CI 48-61) in Norway. No difference in the risk of revision between countries was found for the third revision (HR 1.1, CI 0.7-1.8). CONCLUSION:The incidence of multiply revised knee arthroplasties was not significantly different between Norway and Denmark. The risk and implant survival probability of multiply revised knee arthroplasties was similar in the 2 countries. The results can be used as a benchmark for incidence and prevalence calculations in other countries.

BACKGROUND AND PURPOSE:Total knee arthroplasties (TKA) affect the mechanical loading of the knee joint and may be associated with changes in bone mineral density (BMD). We aimed to evaluate adaptive periprosthetic BMD after cemented and uncemented TKA. METHODS:This is a secondary report of an earlier published RCT. Patients receiving cemented (n = 31) or uncemented (n = 32) TKA were included in a randomized controlled trial (RCT) with a 1:1 allocation. BMD was measured using Dual-energy X-ray Absorptiometry (DEXA) at 1 week and 3, 6, 12, and 24 months postoperatively in 3 regions of interest (ROI) in the femur and tibia. Changes in BMD were assessed using a paired t-test, and between-groups differences using an unpaired t-test. Time-related changes were analyzed using ANOVA. The study was registered at clinicaltrials.gov (NCT03563131) before enrolment. RESULTS:Femoral components: Over 2 years, BMD in ROI I decreased by 33% in the uncemented group and 21% in the cemented group, with a between-group difference of 12.2 percentage points (95% confidence interval [CI] 5.3-19.1; significant). In ROI II, the decrease was 19% vs 13%, with a between-group difference of 6.1 percentage points (CI -1.2 to 13.5; not significant). In ROI III, decreases were 6% vs 7%, with a between-group difference of -0.6 percentage points (CI -4.3 to 3.3; not significant). Tibial components: Changes were small (-4.7 to 3.3%), with significant decreases only in ROI I in the cemented group over 24 months. No significant between-group differences were observed. CONCLUSION:The periprosthetic BMD after TKA decreased both around cemented and uncemented components, particularly in ROI I after using an uncemented femoral component, whereas the decrease under the tibial components was small and of uncertain clinical significans.

Background and purpose: Periprosthetic knee fractures (PPKFs) can be a serious complication after total knee arthroplasty (TKA). We aimed to compare patient-reported outcome (PRO) scores reported between 1 and 4 years after PPKF with a matched uncomplicated TKA control group. Methods: This nationwide cross-sectional matched cohort study included 372 TKA patients with a PPKF occurring from 2019 to 2022 and a control group of 878 uncomplicated TKA patients matched by age, time since TKA, and sex. The study population was derived from the Danish National Patient Register. The patients received questionnaires regarding knee function, quality of life, pain and satisfaction in 2023. The questionnaires included Oxford Knee Score (OKS), the Forgotten Joint Score (FJS), and the EQ-5D-5L Index. Results: The response rate was 48%. Mean OKS was 7 (confidence interval [CI] 5–9) points lower after a PPKF with a score of 30 (standard deviation [SD] 11) in the PPKF group vs 37 (SD 11) in the control group. The FJS was 13 (CI 7–19) points lower after a PPKF with a score of 50 (SD 30) in the PPKF group vs 63 (SD 30) in the control group. Mean EQ-5D-5L Index scores were 0.17 (CI 0.12–0.22) lower after a PPKF with a score of 0.68 (SD 0.25) in the PPKF group vs 0.85 (SD 0.25) in the control group. Additional analysis of patients who completed PROMs 1–2 years compared with 3–4 years after PPKF showed better PRO scores after 3–4 years with an OKS of 32 (SD 12) vs 27 (SD 12), FJS 55 (SD 32) vs 43 (SD 32), and EQ-5D-5L Index of 0.74 (SD 0.34) vs 0.60 (SD 0.34). Conclusion: Following PPKF, patients reported worse knee function, more pain, lower satisfaction, and poorer quality of life than those with uncomplicated TKAs.

Aims:The Oxford Knee Score (OKS) is a 12-item patient-reported outcome measure (PROM), developed for patients who are candidates for total knee arthroplasty (TKA). A prerequisite for a PROM to be considered an adequate measurement instrument is a unidimensional structure as demonstrated by a modern test theory (MTT) model, meaning that each (sub)scale reflects one construct (e.g. pain). However, the structural validity of OKS has only been sparsely evaluated with MTT, and with ambiguous results. This study aimed to assess the structural validity of the Danish OKS. Since the OKS includes items addressing both pain and physical function, it was hypothesized that scores were more accurately reported as two separate subscales. Methods:OKS responses from a study of 1,059 patients treated with a TKA were obtained. Four random subsamples (each with 400 patients) - female and male, preoperative and three months postoperative - were assessed by confirmatory factor analysis (CFA) and Rasch analysis. CFA model fit was evaluated using the chi-squared statistic and indices of close fit. Rasch fit was evaluated with item fit statistics. Both a one-factor solution and two-factor solutions with scores based on two separate subscales were considered for each subsample. Results:OKS data did not fit the original unidimensional model of one total score. Reporting OKS data as the two subscales "pain" and "function" improved CFA fit, but model fit was still inadequate. Results were consistent across subsamples. Conclusion:The structural validity of the Danish OKS is inadequate for evaluating patients awaiting TKA or surgically treated with TKA. OKS data should therefore be interpreted with caution. Randomized treatment studies showing no difference in OKS scores may be reanalyzed based on the two domains to reduce the risk of a potential type-2 error.

BackgroundThis study aims to investigate the effect of the systematic use of patient-reported outcomes (PROs) across healthcare sectors on treatment outcomes and cost-effectiveness (measured as cost per improvement in quality of life) in people with chronic degenerative shoulder conditions.MethodsIn this randomised controlled trial with a 1-year inclusion period and 2-year follow-up, patients with a degenerative shoulder condition (glenohumeral impingement/pain of the acromioclavicular joint, glenohumeral osteoarthritis, rotator cuff degeneration or frozen shoulder) will be included. Every 2nd month, they will be asked to complete questionnaires about the shoulder function (Oxford Shoulder Score), quality of life (EQ-5D-5L) and a trial-specific questionnaire. Healthcare contacts at the general practitioner (GP), the orthopaedic department and the municipal physiotherapeutic centres will be registered prospectively during the follow-up period. In the intervention group, all collected data will be available to the patient and any treating party (GP, orthopaedic surgeons and physiotherapists). For the control group, trial data will be collected, but neither patient nor healthcare professionals will have access to these. After trial termination, follow-up data on use of healthcare services during the 2-year follow-up time will be collected from the Danish National Registries and the intervention and the control group will be compared with regard to use of healthcare services and satisfaction with the evaluation and treatment of their shoulder problem.DiscussionSystematic use of PROs may be a tool to provide patients and clinicians with an insight into symptom development during treatment and to optimise both the treatment of the individual patient as well as a smarter use of the resources available in the healthcare system. The inclusion of patients begins on the 12th of August 2024.Trial registrationClinicalTrials.gov NCT06435494. Registration date 16th of May 2024.

Background: Aseptic loosening remains a main complication following total knee arthroplasty (TKA), requiring revision surgery. Radiostereometric analysis (RSA) can assess the risk of aseptic loosening. This study evaluated the migration and segmental motion of cemented and uncemented femoral and asymmetrical tibial Persona components (Zimmer Biomet) with model-based RSA. Methods: We conducted a randomized controlled trial with 63 patients (22 male patients and 41 female patients, with a mean age of 62 years) and compared patients who underwent TKA with cemented and uncemented Persona components. The primary outcome measure was the maximal total point motion (MTPM) after 2 years. The Mann-Whitney U test was used to compare groups. Migration was visualized by plotting the mean and 95% confidence interval (CI). Results: After 3 months, femoral components demonstrated an MTPM of 0.41 mm (95% CI, 0.35 to 0.48 mm) in the cemented group and 0.65 mm (95% CI, 0.50 to 0.80 mm) in the uncemented group. Subsequently, a stabilization occurred, and the MTPM after 24 months was 0.51 mm (95% CI, 0.41 to 0.61 mm) in the cemented group and 0.83 mm (95% CI, 0.65 to 1.02 mm) in the uncemented group. There was a significant difference between fixation types at 3 months (p = 0.04), 6 months (p = 0.03), 12 months (p = 0.02), and 24 months (p = 0.02). At 3 months postoperatively, the tibial component demonstrated an MTPM of 0.70 mm (95% CI, 0.53 to 0.88 mm) in the cemented group and 0.76 mm (95% CI, 0.61 to 0.91 mm) in the uncemented group. A stabilization was then observed, and migration after 24 months was 0.72 mm (95% CI, 0.55 to 0.89 mm) for cemented components and 0.78 mm (95% CI, 0.64 to 0.92) for uncemented components. Conclusions: TKA with cemented and uncemented Persona components showed migration values within acceptable ranges, suggesting successful long-term fixation; however, significant differences in mean MTPM between cemented and uncemented femoral components were found. Level of Evidence: Therapeutic Level I . See Instructions for Authors for a complete description of levels of evidence.

Purpose:To estimate the downstream effect of septic first revision total knee arthroplasty (rTKA) on the risk of second and third revision compared with aseptic first rTKA. Methods:A register study of The Danish National Patient Registry and The Danish Knee Arthroplasty Register. rTKAs performed in Denmark from 1998 to 2021 were identified. We included only major revisions defined as the exchange of the tibial and/or femoral components and isolated liner exchanges or patella revisions were not included. Two-stage revisions were counted as one revision. The exposure group was defined as revisions due to any septic indication (Group 1) while the control group was revisions due to all aseptic indications (Group 2). Cox regression analysis was used to compare the groups and estimate the hazard ratio with 95% confidence interval (95% CI) for revision. Results:We identified 1016 septic first revisions in Group 1 and 3902 aseptic first revisions in Group 2. The adjusted cox regression analysis demonstrated that Group 1 had a greater risk of a second revision compared to Group 2 (HR 1.4 [95% CI 1.2-1.7]). Additionally, Group 1 had a greater risk of a third revision compared to Group 2 (adjusted HR 1.6 [95% CI 1.1-2.3]). Conclusions:This is the first study to investigate the downstream risk of revision after a first revision TKA. The adjusted HR of the risk of a third revision was 1.6 higher for septic first rTKAs compared to aseptic first rTKAs, not counting insertions of spacers. This prolonged consequence of PJI is important information for both surgeons and patients. Level of Evidence:Level III, retrospective comparative study.

PURPOSE:The aim of this study was to estimate the relative risk of revision for total knee arthroplasty (TKA) with prior knee arthroplasties compared to TKAs in knees without prior surgery. In addition, this study aimed to assess if there was a dose-response relationship between the number of prior knee arthroscopies and the risk of TKA revision. METHODS:A retrospective observational study of three Danish Health Registries. All primary TKAs performed in Denmark from 1998 to 2021 were identified. Knee arthroscopies prior to primary arthroplasty were identified for these knees. The patients were grouped by whether they had an arthroscopy prior to the TKA or not. Kaplan-Meier analysis and Cox regression analysis was used to estimate implant survival and hazard ratio (HR) for revision. RESULTS:The study included 96,781 primary TKAs without prior surgery (de novo TKA) and 15,042 primary TKAs that had had one or more arthroscopies as only prior surgery. After adjusting for age, sex, and Charlson Comorbidity Index (CCI) the HR for revision was 1.38 (95% confidence interval [CI] 1.29-1.47, p < 0.001) for knees with prior arthroscopy compared to knees without prior arthroscopy. After adjusting for age, sex, and CCI each additional arthroscopy increased the HR for revision of 1.27 (95% CI 1.21-1.33, p < 0.001) in a dose-response manner. CONCLUSION:Previous knee arthroscopies increase the risk of revision following primary TKA. More importantly, each additional knee arthroscopy increased the risk by 27%. Although the exact mechanism behind the observation is unknown, this is important information for both surgeons and patients when considering treatment options for knees affected by degenerative conditions. LEVEL OF EVIDENCE:Level III, retrospective comparative study.

Clinically relevant animal models of peri-prosthetic joint infection (PJI) are essential for studying infection initiation and progression. This study developed a PJI model in adult Göttingen minipigs, explicitly focusing on the early stages of infection to gain new perceptions of PJI initiation. The model was established by drilling a hole into the femoral head, followed by inoculation with either Staphylococcus aureus (n = 6) or saline (n = 4) and inserting a stainless-steel screw. The animals were euthanized within 2 or 3 days post-inoculation. Comprehensive bone and joint pathology analyses were performed. All S. aureus inoculated animals had bacteria reisolated from bone, screw, synovial fluid, and synovial membrane. Histology revealed numerous bacterial colonies in the peri-implant bone tissue, many of which were unaccompanied by neutrophils, indicating delayed neutrophil recruitment to bacteria. In contrast, all synovial membrane-located bacteria were recognized by the immune system. Digital pathology measures showed deep bacterial dispersion within the bone, at a far distance from the point of inoculation. This study presents a new PJI model, which facilitates the investigation of infection initiation and supports studies aimed at preventing PJI. The study uncovered two previously unknown insights into the development of PJI: delayed bacterial neutrophil recruitment and widespread osseous bacterial dissemination within 48 h.

The risk of infection when inserting orthopedic devices like prostheses, screws, and plates represents a serious and challenging complication in orthopedic surgery. Most infections result from bacterial introduction during surgery, making it crucial and clinically relevant to protect the devices and surrounding tissue with intraoperative antimicrobials, especially in high-risk patients. Therefore, to mitigate this risk, antimicrobial coatings for different types of orthopedic devices have received substantial attention in recent decades with the goal of developing a "self-cleaning" surface. In here, we investigated a new and highly promising coating candidate. The coating was made of a hyperbranched poly(ethylene imine (PEI)) + orthosilicic acid-based hydrogel, that in a sol-gel process was transformed into a solid xerogel, which afterwards was loaded with gentamicin as active compound. The gentamicin-loaded xerogel coating was applied to functional implants i.e., cancellous bone screws, and tested within an advanced minipig model of Staphylococcus aureus induced peri-prosthetic joint infection, without the use of systemic antimicrobial therapy. The study included evaluation of antimicrobial efficacy (quantification of bacterial load on the screw surface and within the surrounding tissues), pre -and postinsertion characterization of the coating, assessment of local inflammation and gene expression, and acute toxicity. Additionally, the pharmacokinetic in-vivo gentamicin release profile was measured using microdialysis in relevant local compartments. Due to a quick, locally high, and complete gentamicin release, the coating completely eradicated S. aureus from all compartments in all but one minipig. Therefore, this study shows proof of concept for the effectiveness of preventive antimicrobial release-based coatings.

Importance:Surgeon training with a specific implant is often not considered in implant registry-based studies, which may lead to unobserved confounding bias. Discrepancies between registry and clinical trial outcomes for patellofemoral arthroplasty (PFA) may originate from differences in surgeon training levels. Objective:To compare revision rates for knees operated on by knee surgeons specifically trained for PFA and knee surgeons who were not. Design, Setting, and Participants:In this population-based cohort study, the framework of a target trial was used to compare outcomes for 2 patient groups: patients who underwent PFA performed by knee surgeons who had (trial surgeons) vs who had not (nontrial surgeons) received focused PFA training as part of a randomized clinical trial. All primary PFA procedures from January 1, 2008, through December 31, 2015, were identified using Danish registries and individual hospital notes with 6 years' follow-up. Data were analyzed from January 24 to March 1, 2024. Exposure:Focused PFA training. Main Outcomes and Measures:The primary outcome was 6-year risk of revision. Analyses were conducted according to a prespecified statistical analysis plan, using multiple logistic regression to estimate marginal risk ratios for 6-year risks of revision, reoperation, and mortality, adjusting for potential confounders. Results:Of 482 eligible knees of patients who had undergone PFA, 274 (57%; 206 female [75%]; mean [SD] age, 61 [13] years) were operated on by trial surgeons, and 208 (43%; 142 female [68%]; mean [SD] age, 57 [12] years) by nontrial surgeons. Trial surgeons operated on knees with higher patellofemoral Kellgren-Lawrence osteoarthritis grade (range 0-4, with 0 indicating no osteoarthritis and 4 indicating severe osteoarthritis) than nontrial surgeons (79% vs 53% with grade 3 to 4) and higher tibiofemoral Kellgren-Lawrence osteoarthritis grades (37% vs 17% with grade 2 to 4). The 6-year revision rate for trial surgeons was 8% (22 of 274 knees) vs 26% (54 of 208 knees) for nontrial surgeons, corresponding to an adjusted relative risk (RR) of 0.35 (95% CI, 0.22-0.56; P < .001). The reoperation rate was 12% (33 of 274 knees) for trial surgeons vs 19% (40 of 208 knees) for nontrial surgeons, with an adjusted RR of 0.71 (95% CI, 0.42-1.18; P = .19). There was no difference in mortality for trial vs nontribal surgeon groups (18 of 274 knees [7%] vs 12 of 208 knees [6%]; adjusted RR, 1.11 [95% CI, 0.53-2.33; P = .79). Conclusions and Relevance:In this cohort study using a target trial emulation approach to assess the association of surgeon training with PFA outcomes, the cumulative 6-year revision rate for PFA was lower for knees operated on by PFA-trained knee surgeons, suggesting that such surgeon training was associated with a better outcome. This suggests that the level of training may be an important confounder for registry-based comparisons of implant outcome, and that this confounder may even obscure inherent implant outcomes.

Cancer research has demonstrated that immune checkpoints have a central role in mediating immunosuppressive signalling within tumors. Immune checkpoint inhibitors, designed to block these signals, can enhance immune responses to eliminate cancer cells. Emerging evidence suggests that bacteria, similar to cancer cells, can upregulate immune checkpoints to escape immunosurveillance. Here, we explore if immune checkpoints are also upregulated in intraoperative tissue samples from periprosthetic joint infection (PJI). Paraffin-embedded periprosthetic membrane tissue from 35 patients (mean age: 69 years) undergoing revision surgery of a hip or knee joint was obtained and classified as infected (n=17) or aseptic (n=18) according to EBJIS diagnostic criteria. Tissue sections were stained with immunohistochemical protocols towards the immune checkpoints VISTA and TIM-3. A pixel classifier algorithm was trained to quantify positive immune checkpoint staining in digitally scanned tissue sections using the bioimage analysis software QuPath (Figure 1). The percentage of global VISTA staining was significantly increased in infected (mean: 1.4%, range: 0.05-5.7%) compared to aseptic revisions (mean: 0.4%, range: 0.008-1.9%), while there was no difference in TIM-3 staining. VISTA primarily stained neutrophils and lymphocytes, while TIM-3 broadly stained cells such as lymphocytes, macrophages, giant cells and fibroblasts. The percentage of VISTA and TIM-3 staining showed a significant correlation with joint type, with higher staining observed in tissue from knee compared to hip joints (r = 0.34-0.51). Increased expression of VISTA suggests that local immunosuppression is present in PJI. Therefore, it seems relevant to investigate immune checkpoints as immunotherapeutic targets for PJI. The observed heterogeneity in immune checkpoint expression among patients may reflect individual variations in immune responses during PJI. Further research on different immune checkpoints with distinct functional properties across larger patient populations is needed to understand their potential as therapeutic targets in PJI settings. Funding: Novo Nordisk Foundation and Gigtforeningen For any figures or tables, please contact the authors directly.

BACKGROUND:Knee arthroplasty is a common surgical treatment aimed at improving function and reducing pain. While generally successful, some patients experience complications or dissatisfaction, leading to a sequence of revision surgeries. These revisions are less successful than primary surgeries and carry risks. This study explores the impact on daily life of knee revisions for pain and poor knee function, patient motivations, and experiences, aiming to inform better decision-making. METHODS:A qualitative approach was used to investigate the experiences and thoughts of multiply revised knee patients with pain and poor function as dominating indications. We conducted 12 semi-structured single interviews with patients from three tertiary referral centres. Patients who had undergone two or more knee revisions, were cognitively competent and able to communicate in Danish were considered for inclusion. Patients who were revised because of infection or fracture were excluded from interviews. RESULTS:The patient conversations highlighted the daily struggle to achieve what each of the patients identified as a normal existence. The study identified one main theme: striving for a normal life and two sub-themes: (1) the desire for an active life and (2) the hope for improvement. The themes highlight the patients' wishes and thoughts in the period following surgery, what they find particularly challenging, and the underlying reasons for their willingness to undergo another revision. The results emphasize how patients' strong wish for a physically and socially active life free from pain, combined with their high hopes for improvement and faith in the biomedical model, drives a willingness to undergo additional surgeries despite previous suboptimal outcomes. CONCLUSION:The study finds that patients' desire for a normal life and hope for improvement influence their decision to undergo revisions despite the potential risks. The pain impacting their daily lives and a strong trust in biomedical solutions leads them to consider further surgeries. The results of the study contribute to a better understanding of this patient group and can be used for informed decision-making regarding revision surgery, ensuring that the offered surgery aligns with the patients' needs. TRIAL REGISTRATION:Our article does not report on health care intervention on human participants Clinical trial number: not applicable.