Radiographic measurement of the congruence angle according to Merchant: validity, reproducibility, and limits

Abstract Purpose The objective of this study was to analyze the intra- and interobserver variability of this measurement according to a strict methodology and on a representative sample of the general population, as well as to identify the possible difficulties of measurement in case of patellar or trochlear dysplasia. Methods This observational study involved radiographic analysis by three independent observers of a total of 50 patients who had a loaded patellofemoral X-ray taken with the knee flexed to 45°. An initial reading was taken to measure the angle of the trochlear sulcus, the Merchant angle, and to classify the knees according to a possible trochlear dysplasia and/or patellar dysplasia according to Wiberg. A second measurement was then performed to analyze intraobserver agreement. Interobserver agreement was measured on all radiographic measurements (n = 100). Results The Merchant patellofemoral congruence angle showed good intraobserver concordance ranging from 0.925 (95% CI 0.868–0.957) to 0.942 (95% CI 0.898–0.967), as well as interobserver concordance ranging from 0.795 (95% CI 0.695–0.862) to 0.914 (95% CI 0.872–0.942). Poor results were found in terms of interobserver concordance on the measurement of the Merchant angle in case of stage 3 Wiberg patella ranging from 0.282 (95% CI −0.920 to 0.731) to 0.611 (95% CI 0.226–0.892). Conclusion Congruence angle is one of most commonly used measurements for patellar tracking. However, the convexity of the patellar surface makes it difficult to identify the patellar apex on its intraarticular facet, making the measurement of the Merchant congruence angle unreliable and not very reproducible in cases of stage 3 Wiberg patella. Registration N°IRB 2021/13

Study of Mechanical Behavior in Epiphyseal Fracture Treated by Reduction and Cement Injection: No Immediate Post-Operative Weight-Bearing but Only Passive and Active Mobilization Should be Advised

International audienceThe development of new percutaneous treatment techniques using a balloon for the reduction and cement for the stabilization for tibial plateau fractures (TPF) are promising. The biomechanical changes brought by the cement in the periarticular fracture are unknown. The objective of this study was to provide elements of understanding of the bone behavior in an epiphyseal fracture treated with cementoplasty and to define the modifications brought about by the presence of this cement in the bone from both an architectural and biomechanical point of view. In vitro animal experimentation was conducted. Bones samples were prepared with a cavity created with or without cancellous compaction, aided by balloon expansion following the same protocol as in the treatment of TPF. A uniaxial compression test was performed with various speeds and by using Heaviside Digital Image Correlation to measure mechanical fields. Preliminary finite element models were constructed with various boundary conditions to be compared to our experimental results. The analysis of the images permits us to obtain a representative load vs. time response, the displacement fields, and the strain distribution for crack initiation for each sample. Microcracks and discontinuity began very early at the interface bone/cement. Even when the global behavior was linear, microcracks already happened. There was no strain inside the cement. The finite element model that matched our experiments had no link between the two materials. In this work, the use of a novel correlation process highlighted the biomechanical role of the cement inside the bone. This demonstrated that there is no load transfer between bone and cement. After the surgery, the cement behaves like a rigid body inside the cancellous bone (same as a screw or plate). The cement provides good reduction and primary stabilization (mini-invasive approach and good stress distribution), permitting the patient to undergo rehabilitation with active and passive mobilization, but no weight-bearing should be authorized while the cortical bone is not consolidated or stabilized

Extrusion and meniscal mobility evaluation in case of ramp lesion injury: a biomechanical feasibility study by 7T magnetic resonance imaging and digital volume correlation

International audienceIntroduction: The existing body of literature on the biomechanical implications of ramp lesions is limited, leaving a significant gap in our understanding of how these lesions impact joint kinematics and loading in the medial compartment. This cadaveric biomechanical study aims to address this gap by employing an innovative Digital Volume Correlation (DVC) method, utilizing 7 Tesla Magnetic Resonance Imaging (MRI) images under various loading conditions. The primary objective is to conduct a comprehensive comparison of medial meniscal mobility between native knees and knees affected by grade 4 ramp lesions. By focusing on the intricate dynamics of meniscal mobility and extrusion, this work seeks to contribute valuable insights into the biomechanical consequences of medial meniscus ramp lesions.Materials and methods: An initial set of 7T MRI imaging sessions was conducted on two intact native knees, applying load values up to 1500N. Subsequently, a second series of images was captured on these identical knees, with the same loads applied, following the creation through arthroscopy of medial meniscus ramp lesions. The application of DVC enabled the precise determination of the three components of displacement and spatial variations in the medial menisci, both with and without ramp lesions.Results: The measured directional displacements between native knees and injured knees indicate that, following the application of axial compression load, menisci exhibit increased extrusion and posterior mobility as observed through DVC.Discussion: Injuries associated with Subtype 4 medial meniscus ramp lesions appear to elevate meniscal extrusion and posterior mobility during axial compression in the anterior cruciate ligament of intact knees. Following these preliminary results, we plan to expand our experimental approach to encompass individuals undergoing weight-bearing MRI. This expansion aims to identify meniscocapsular and/or meniscotibial insufficiency or rupture in patients, enabling us to proactively reduce the risk of osteoarthritic progression

Prognosis of lymphoma in patients with known inflammatory bowel disease: A french multicentre cohort study

International audienceBackground and Aims: The prognosis of lymphoma that occurs in patients with inflammatory bowel disease [IBD] is poorly known. Methods: A multicentre retrospective cohort analysis was done in seven French tertiary centres from 1999 to 2019. Only lymphoma occurring in patients with previous established diagnosis of IBD were analysed. The primary outcome was progression-free survival at 3 years. Results: A total of 52 patients [male 65%, Crohn's disease 79%, median age 48.3 years, median duration of IBD 10.1 years] were included, of whom 37 had been previously exposed to immunosuppressants and/or biologics for at least 3 months and 20 had primary intestinal lymphomas. The lymphoma histological types were: Diffuse large B cell lymphomas [N = 17], Hodgkin lymphomas [N = 17], indolent B cell lymphomas [N = 12], and others including T cell lymphomas, mantle cell lymphomas, and unclassifiable B cell lymphoma [N = 6]. The median follow-up after lymphoma was 5.1 years (interquartile range [IQR] 4-7.8). Progression-free survival at 3 years was 85% in the overall population (95% confidence interval [CI] 75%-96%) with no significant difference between the exposed and unexposed group, 79% for patients exposed to immunosuppressants and/or biologics [95% CI 67%-94%], and 83% for patients diagnosed with primary intestinal lymphoma [95% CI 67%-100%]. No relapse of IBD has been observed during chemotherapy. The IBD relapse rate at the end of the last chemotherapy cycle was 23% at 3 years [95% CI 11%-39%] in the overall population. Conclusions: In this large cohort, the prognosis for lymphomas occurring in IBD appears to be good and similar to what is expected, irrespective of the exposure to biologics and/or immunosuppressants