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Purpose. Metallic resurfacing implants have been developed for the treatment of early, focal, small, condylar and trochlear osteoarthritis (OA) lesions. They represent an option for patients who are either too young to fulfill the criteria for total knee arthroplasty (TKA) or too old for biological treatment. Although relevant clinical evidence has been collected for different resurfacing types, the in vivo post-operative knee kinematics remains unknown. The present study aims to measure and analyse the knee joint kinematics in subjects with patient-specific Episealer implants
Methods. Retrospective study design. Fluoroscopic analyses during high flexion activities (unloaded flexion-extension and loaded lunge) were conducted at >12 months post-surgery in ten Episealer knees. The post-operative knee joint kinematics was compared to equally assessed kinematic from ten healthy knees, twenty G-Curve TKA knees and 10 J-Curve knees. Pre- and postoperative clinical data of the Episealer knees were collected using a visual analog scale (VAS), the EQ 5d Health Questionnaire and the Knee Injury and Osteoarthritis Outcome Score (KOOS).
Results. During unloaded flexion-extension and loaded lunge, the medial condyle in the Episealer knees remained relative stationary, indicating a medial pivot, while the lateral condyle translated consistently towards posterior. Similarly, reduced movement of the medial condyle and posterior translation of the lateral condyle was also observed in the healthy knees, although to a lesser extent. In contrast, the kinematics of both TKA cohorts during unloaded flexion-extension showed a tendency towards anterior displacement in the medial compartment, which led to significant differences in comparison with the Episealer knees. In the lateral compartment, a certain degree of femoral rollback was noted in the G-Curve TKA cohort. Improved scores were observed in the Episealer subjects between the preoperative and 1-year postoperative follow-up.
Conclusion. At 12 months postsurgery, a physiological-like knee kinematics was observed in the group of patient-specific reconstructed chondral/osteochondral lesions by means of a resurfacing Episealer implant strategy. Considering that these patients are physically active and do not fulfill the criteria for TKA, the group is hard to be compared to TKA patients which usually are less active and more challenging. Nevertheless, the comparison to either healthy knee kinematics as well as to TKA reconstructed knees with different implant designs showed a more physiological-like kinematics in the resurfacing implants that seems more appropriate for such a patient group. Despite positive results, careful clinical follow-up of treated patients is recommended for the long-term OA progression. Further investigations need to be encouraged not only in larger patient groups but also in a prospective manner to assess the pre- to postoperative kinematic changes.
Introduction: Anterior knee pain and other patello-femoral (PF) complications frequently limit the success of total knee arthroplasty as the final treatment of end stage osteoarthritis. However, knowledge about the in-vivo loading conditions at the PF joint remains limited, as no direct measurements are available. We hypothesised that the external knee flexion moment (EFM) is highly predictive of the PF contact forces during activities with substantial flexion of the loaded knee.
Materials and methods: Six patients (65–80 years, 67–101 kg) with total knee arthroplasty (TKA) performed two activities of daily living: sit-stand-sit and squat. Tibio-femoral (TF) contact forces were measured in vivo using instrumented tibial components, while synchronously internal TF and PF kinematics were captured with mobile fluoroscopy. The measurements were used to compute PF contact forces using patient specific musculoskeletal models. The relationship between the EFM and the PF contact force was quantified using linear regression.
Results: Mean peak TF contact forces of 1.97–3.24 times body weight (BW) were found while peak PF forces reached 1.75 to 3.29 times body weight (BW). The peak EFM ranged from 3.2 to 5.9 %BW times body height, and was a good predictor of the PF contact force (R2 = 0.95 and 0.88 for sit-stand-sit and squat, respectively).
Discussion: The novel combination of in vivo TF contact forces and internal patellar kinematics enabled a reliable assessment of PF contact forces. The results of the regression analysis suggest that PF forces can be estimated based solely on the EFM from quantitative gait analysis. Our study also demonstrates the relevance of PF contact forces, which reach magnitudes similar to TF forces during activities of daily living.
OBJECTIVES:
To evaluate the reliability of the modified Radiographic Union Score for Tibial fractures (mRUST) as a reliable tool for monitoring lower limb fractures (femur, tibia) treated with various modalities (nail, plate).
METHODS:
Design:
Retrospective analysis.
Setting:
Single center academic hospital in Germany.
Patient Selection Criteria:
Adult patients (≥18 years) with extra-articular long bone fractures of the lower extremities treated surgically between January 2005 and April 2022, requiring radiographs in two perpendicular planes and at least one follow-up visit, were included. Exclusion criteria were critical clinical conditions, inability to consent, joint articulation fractures, inadequate documentation, or insufficient imaging quality.
Outcome Measures and Comparisons:
Six international investigators (five orthopedic surgeons, one radiologist) independently assessed fracture line and callus growth per cortex (mRUST) at individualized follow-up time points based on clinical practice. To evaluate interrater reliability, intraclass correlation coefficients were calculated for the overall dataset, and for subsets of rated images, that were defined based on anatomical location (femur/tibia), treatment type (plate/nail fixation), and treatment combinations across locations.
RESULTS:
A total of 166 patients (63 femur fractures, 103 tibia fractures; 32.5% female, mean age 43.4 (18–84)) with 1136 follow-up time points were analyzed. Overall interrater reliability for mRUST was good (intraclass correlation coefficient 0.77), consistent across fixation methods (nail/plate fixation, 0.79) and anatomical locations (tibia, 0.78; femur, 0.81). Cortex-specific reliability varied, with highest agreement for the medial cortex (0.70–0.74) and lowest for the posterior cortex (0.65–0.74).
CONCLUSIONS:
The mRUST (radiographic score) demonstrated reliability for monitoring fracture healing in the femur and tibia, irrespective of fixation method, supporting its use as a generalizable tool across lower limb fractures.
LEVEL OF EVIDENCE:
Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.
Callus formation during healing is guided by local strain: a retrospective clinical observation
(2026)
Abstract
Background
Clinically, fracture healing is typically monitored though serial radiographs. Specifically, callus development (growth and mineralization) is an indicator of healing and associated with local mechanical strain. However, a sustainable relationship between mechanical conditions and the respective healing progress has not been shown so far.
Material and methods
One hundred sixty-six patients with extra-articular lower-limb fractures treated by osteosynthesis plates or intramedullary nails were included. Callus formation (visible area in X-ray relative to bone shaft) and quality (image intensity relative to the cortex) were measured by consecutive X-ray analyses as well as the modified Radiographic Union-Score for Tibia (mRUST) during follow-up. Corresponding load- and fixation-matched finite element analysis (FEA) modelling was developed for tibia or femur loading as well as plate or intramedullary nail fixation. Mechanical strains (medially, laterally, dorsally, anteriorly) were evaluated from FEA and compared to the progress in X-ray callus formation and quality to perform a correlation analysis between observed callus formation and simulated local mechanical strains.
Results
For femoral fractures, callus size was largest dorso-medially (1.41 ± 1.57 cm
2
/cm and 1.18 ± 1.11 cm
2
/cm at 180 ± 45 days post-surgery) while largest callus formations were found laterally in tibial fractures (0.75 ± 0.49 cm
2
/cm at 365 ± 45 days post-surgery). These locations of maximal callus size in femur and tibia matched the locations of extreme principal strains from FEA. In femur, callus density increased steadily and exceeded cortex density at 365 ± 45 days post-surgery. For tibia, no such clear trend was observable. While initially showing a similar increase in callus bridging score mRUST, increase over 2 years was 48% higher for the tibial fractures compared to femoral fractures. While principal strains correspond to increases in early callus formation in both femur and tibia (Kendall-Tau-b:
p
= 0.021 for volumetric strain at 90 ± 45 days post-surgery), shear strains are consistently associated with less callus formation (Kendall-Tau-b:
p
= 0.048 for volumetric/shear strain associated with callus size*density at 365 ± 45 days post-surgery).
Conclusions
Callus formation during bone healing may be associated with local mechanical strain in lower limb fractures within a clinically relevant cohort including different fracture locations and fixation types. Shear strain at the fracture site appeared to be associated with reduced quality callus formation, whereas principal strain was observed to correlate with increased early callus formation. The presented methodology may have potential as a predictor of healing processes and could help identify mechanically challenging fracture fixation settings.
Level of evidence
II.
Trial registration
Ethical approval was obtained from the local ethics board to this retrospective study design (EA4/099/24).
Anterior knee pain and other patello-femoral (PF) complications frequently limit the success of total knee arthroplasty as the final treatment of end stage osteoarthritis. However, knowledge about the invivo loading conditions at the PF joint remains limited, as no direct measurements are available. We hypothesised that the external knee flexion moment (EFM) is highly predictive of the PF contact forces during activities with substantial flexion of the loaded knee.Six patients (65-80 years, 67-101 kg) with total knee arthroplasty (TKA) performed two activities of daily living: sit-stand-sit and squat. Tibio-femoral (TF) contact forces were measured in vivo using instrumented tibial components, while synchronously internal TF and PF kinematics were captured with mobile fluoroscopy. The measurements were used to compute PF contact forces using patient specific musculoskeletal models. The
relationship between the EFM and the PF contact force was quantified using linear regression.Mean peak TF contact forces of 1.97 to 3.24 times body weight (BW) were found while peak PF forces reached 1.75 to 3.29 times body weight (BW). The peak EFM ranged from 3.2 to 5.9 %BW times body height, and was a good predictor of the PF contact force (R^2 = 0.95 and 0.88 for sit-standsit and squat, respectively).The novel combination of in vivo TF contact forces and internal patellar kinematics enabled a reliable assessment of PF contact forces. The results of the regression analysis suggest that PF forces can be estimated based solely on the EFM from quantitative gait analysis. Our study also demonstrates the relevance of PF contact forces, which reach magnitudes similar to TF forces during activities of daily living.
Anterior knee pain (AKP) remains as one of the most cited causes of patient’s dissatisfaction after total knee arthroplasty (TKA) with non-physiological knee joint kinematics patterns during flexion and patellar maltracking being frequently associated with it. Incorporating in vivo knee joint kinematics into the design of new TKA systems could significantly reduce these negative outcomes. This study aims to show the outcome of a new TKA system developed considering previously assessed in vivo knee joint kinematics.
Retrospective study design. Eleven patients treated with the 5C® LATic TKA system were included. In-vivo fluoroscopic measurements in loaded lunge to collect the 3D TKA motion from extension to maximal flexion was conducted at 12 months after index surgery. All patients answered the KSS, FJS and HFKS questionnaires.
The kinematics of the 5C® LATic system were characterized by a lateral stability as well as reduced anterior movement in the medial compartment, resulting in an external rotation of the femoral component of the tibia plateau.
Moreover, the frontal points reveal a consistent posterior movement of the frontal aspect until maximal achieved flexion. All patients showed improvements in all administered questionnaires compared to their preoperative state, with high overall satisfaction reported for the prosthesis. The results show an expected design-based kinematics. Although the posterior translation of the frontal aspect of the femoral component can only be interpreted as an indirect measure of patellar movement, the increased motion observed, together with the external rotation on the tibia plateau, may contribute to improvement in patellar tracking, which is recognized as a direct contributor to AKP
