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Background: In vivo measurements of tibiotalar and subtalar joint motion following TAR are unavailable. Using biplane fluoroscopy, we tested the hypothesis that the prosthetic tibiotalar joint and adjacent subtalar joint would demonstrate kinematic and range of motion differences compared to the contralateral untreated limb, and control participants. Methods: Six patients of 41 identified candidates that all underwent unilateral Zimmer TAR (5.4 ± 1.9 years prior) and 6 control participants were imaged with biplane fluoroscopy during overground walking and a double heel-rise activity. Computed tomography scans were acquired; images were segmented and processed to serve as input for model-based tracking of the biplane fluoroscopy data. Measurements included tibiotalar and subtalar kinematics for the TAR, untreated contralateral, and control limbs. Statistical parametric mapping quantified differences in kinematics throughout overground walking and the double heel-rise activity. Results: Patients with this TAR performed walking and heel-rise activities symmetrically with no significant kinematic differences at the tibiotalar and subtalar joints between limbs. Compared to control participants, patients exhibited reduced dorsi/plantarflexion range of motion that corresponded to decreased peak dorsiflexion, but only in the late stance phase of walking. This reduction in tibiotalar dorsi/plantarflexion range of motion in the TAR group became more apparent with double heel-rise activity. Conclusion: Patients with a Zimmer TAR had symmetric kinematics during activities of walking and double heel-rise, but they did exhibit minor compensations in tibiotalar kinematics as compared to controls. Clinical Relevance: The lack of significant kinematic compensation at the subtalar joint may explain why secondary subtalar osteoarthritis is reported as being relatively uncommon in patients with some TAR designs.

Although TTo characterize the variability in 2-year hip cartilage TProspective.A total of 25 women (age: 51.9 ± 16.3 years old; BMI: 22.6 ± 2.0 kg/mA 3 T MRI (GE), 3D combined TPrincipal component (PC) analysis of Z-score difference maps of 2-year changes in hip cartilage TShapiro-Wilk test, unpaired t-tests, Kruskal Wallis tests, Pearson or Spearman (ρ) correlations. Significance was set at P 0.05.Women (-6.40 ± 14.48) had significantly lower TMen exhibited accelerated T2 TECHNICAL EFFICACY: Stage 3.

The aims of this case-control study were to: (1) Identify cartilage locations and volumes at risk of osteoarthritis (OA) using subject-specific finite element (FE) models; (2) Quantify the relationships between the simulated biomechanical parameters and T2 and T1ρ relaxation times of magnetic resonance imaging (MRI). We created subject-specific FE models for seven patients with anterior cruciate ligament (ACL) reconstruction and six controls based on a previous proof-of-concept study. We identified locations and cartilage volumes susceptible to OA, based on maximum principal stresses and absolute maximum shear strains in cartilage exceeding thresholds of 7 MPa and 32%, respectively. The locations and volumes susceptible to OA were compared qualitatively and quantitatively against 2-year longitudinal changes in T2 and T1ρ relaxation times. The degeneration volumes predicted by the FE models, based on excessive maximum principal stresses, were significantly correlated (r = 0.711, p < 0.001) with the degeneration volumes determined from T2 relaxation times. There was also a significant correlation between the predicted stress values and changes in T2 relaxation time (r = 0.649, p < 0.001). Absolute maximum shear strains and changes in T1ρ relaxation time were not significantly correlated. Five out of seven patients with ACL reconstruction showed excessive maximum principal stresses in either one or both tibial cartilage compartments, in agreement with follow-up information from MRI. Expectedly, for controls, the FE models and follow-up information showed no degenerative signs. Our results suggest that the presented modelling methodology could be applied to prospectively identify ACL reconstructed patients at risk of biomechanically driven OA, particularly by the analysis of maximum principal stresses of cartilage.

Clinicians often examine movement patterns to design hip osteoarthritis (OA) interventions, yet traditional biomechanical analyses only report a single timepoint. Multivariate principal component analysis (MFPCA) analyzes the entire waveform (i.e., movement pattern), which clinicians observe to direct treatment. This study investigated hip OA indicators, by (1) employing MFPCA to characterize variance across the hip, knee, and ankle angles in healthy and early-to-moderate hip OA participants; and (2) investigating relationships between these waveform features and hip cartilage health. Bilateral hip magnetic resonance images from 72 participants with Kellgren-Lawrence grades ranging from 0 to 3 were used to calculate mean T1ρ and T2 relaxation times in the femoral and acetabular cartilage. MFPCA was performed on lower-limb gait biomechanics and used to identify primary modes of variation, which were related to T1ρ and T2 relaxation times. Here, a MFPC = mode of variation = waveform feature. In the femoral cartilage, transverse plane MFPCs 3 and 5 and body mass index (BMI) was related to T1ρ , while MFPC 2 and BMI were related to T2 relaxation times. In the acetabular cartilage, sagittal plane MFPC 1 and BMI were related to T1ρ , while BMI was related to T2 relaxation times. Greater internal rotation was related to increased T1ρ and T2 relaxation times in the femoral cartilage, while the greater extension was related to increased T1ρ relaxation times in the acetabular cartilage. This study established a data-driven framework to assess relationships between multi-joint biomechanics and quantitative assessments of cartilage health and identified waveform features that could be evaluated in future hip OA intervention studies.

Background Tibiotalar arthrodesis is a common treatment for end-stage tibiotalar osteoarthritis, and is associated with a long-term risk of concomitant subtalar osteoarthritis. It has been clinically hypothesized that subtalar osteoarthritis following tibiotalar arthrodesis is the product of compensatory subtalar joint hypermobility. However, in vivo measurements of subtalar joint motion following tibiotalar arthrodesis have not been quantified. Using dual-fluoroscopy motion capture, we tested the hypothesis that the subtalar joint of the limb with a tibiotalar arthrodesis would demonstrate differences in kinematics and increased range of motion compared with the subtalar joint of the contralateral, asymptomatic, untreated ankle. Methods Ten asymptomatic patients who had undergone unilateral tibiotalar arthrodesis at a mean (and standard deviation) of 4.0 ± 1.8 years previously were evaluated during overground walking and a double heel-rise task. The evaluation involved markerless tracking with use of dual fluoroscopy integrated with 3-dimensional computed tomography, which allowed for dynamic measurements of subtalar and tibiotalar dorsiflexion-plantar flexion, inversion-eversion, and internal-external rotation. Range of motion, stance time, swing time, step length, and step width were also measured. Results During the early stance phase of walking, the subtalar joint of the limb that had been treated with arthrodesis was plantar flexed (-4.7° ± 3.3°), whereas the subtalar joint of the untreated limb was dorsiflexed (4.6° ± 2.2°). Also, during the early stance phase of walking, eversion of the subtalar joint of the surgically treated limb (0.2° ± 2.3°) was less than that of the untreated limb (4.5° ± 3.2°). During double heel-rise, the treated limb exhibited increased peak subtalar plantar flexion (-7.1° ± 4.1°) compared with the untreated limb (0.2° ± 1.8°). Conclusions A significant increase in subtalar joint plantar flexion was found to be a primary compensation during overground walking and a double heel-rise activity following tibiotalar arthrodesis. Clinical relevance Significant subtalar joint plantar flexion compensations appear to occur following tibiotalar arthrodesis. We found an increase in subtalar plantar flexion and considered the potential relationship of this finding with the increased rate of subtalar osteoarthritis that occurs following ankle arthrodesis.

Background Several multi-segment foot models have been developed to evaluate foot and ankle motion using skin-marker motion analysis. However, few multi-segment models have been evaluated against a reference standard to establish kinematic accuracy. Research question How accurately do skin-markers estimate foot and ankle motion for the modified Shriners Hospitals for Children Greenville (mSHCG) multi-segment foot model when compared against the reference standard, dual fluoroscopy (DF), during gait, in asymptomatic participants? Methods Five participants walked overground as full-body skin-marker trajectory data and DF images of the foot and shank were simultaneously acquired. Using the mSHCG model, ankle and midfoot angles were calculated throughout stance for both motion analysis techniques. Statistical parametric mapping assessed differences in joint angles and marker positions between skin-marker and DF motion analysis techniques. Paired t tests, and linear regression models were used to compare joint angles and range of motion (ROM) calculated from the two techniques. Results In the coronal plane, the skin-marker model significantly overestimated ROM (p = 0.028). Further, the DF model midfoot ROM was significantly positively related to differences between DF and skin-marker midfoot angles (p = 0.035, adjusted R2 = 0.76). In the sagittal plane, skin-markers underestimated ankle angles by as much as 7.26°, while midfoot angles were overestimated by as much as 9.01°. However, DF and skin-marker joint angles were not significantly different over stance. Skin-markers on the tibia, calcaneus, and fifth metatarsal had significantly different positions than the DF markers along the direction of walking for isolated portions that were less than 10 % of stance. Euclidean distances between DF and skin-markers positions were less than 9.36 mm. Significance As the accuracy of the mSHCG model was formerly unknown, the results of this study provide ranges of confidence for key angles calculated by this model.

Abnormal angular and translational (ie, kinematic) motion at the tibiotalar and subtalar joints is believed to cause osteoarthritis in patients with chronic ankle instability (CAI).In this preliminary study the investigators quantified and compared in vivo tibiotalar and subtalar kinematics in 4 patients with CAI (3 women) and 10 control subjects (5 men) using dual fluoroscopy during a balanced, single-leg heel-rise and treadmill walking at 0.5 and 1.0 m/s.During balanced heel-rise, 69%, 54%, and 66% of mean CAI tibiotalar internal rotation/external rotation (IR/ER), subtalar inversion/eversion, and subtalar IR/ER angles, respectively, were outside the 95% confidence intervals of control subjects. During 0.5-m/s gait, 50% and 60% of mean CAI tibiotalar dorsi/plantarflexion and subtalar IR/ER angles, respectively, were outside the 95% confidence intervals of control subjects. During 1.0-m/s gait, 62%, 65%, and 73% of mean CAI subtalar dorsi/plantarflexion, inversion/eversion, and IR/ER, respectively, were outside the 95% confidence intervals of control subjects. Patients with CAI exhibited less tibiotalar and subtalar translational motion during gait; no clear differences in translations were noted during balanced heel-rise.Overall, the balanced heel-rise activity exposed more tibiotalar and subtalar kinematic variation between patients with CAI and control subjects. Therefore, weight-bearing activities involving large range of motion, balance, and stability may be best for studying kinematic adaptations in patients with CAI.These preliminary results suggest that patients with CAI require more tibiotalar external rotation, subtalar eversion, and subtalar external rotation during weight-bearing stability exercises, all with less overall joint translation.

Use of subject-specific axes of rotation may improve predictions generated by kinematic models, especially for joints with complex anatomy, such as the tibiotalar and subtalar joints of the ankle. The objective of this study was twofold. First, we compared the axes of rotation between generic and subject-specific ankle models for ten control subjects. Second, we quantified the accuracy of generic and subject-specific models for predicting tibiotalar and subtalar joint motion during level walking using inverse kinematics. Here, tibiotalar and subtalar joint kinematics measured in vivo by dual-fluoroscopy served as the reference standard. The generic model was based on a cadaver study, while the subject-specific models were derived from each subject’s talus reconstructed from computed tomography images. The subject-specific and generic axes of rotation were significantly different. The average angle between the modeled axes was 12.9° ± 4.3° and 24.4° ± 5.9° at the tibiotalar and subtalar joints, respectively. However, predictions from both models did not agree well with dynamic dual-fluoroscopy data, where errors ranged from 1.0° to 8.9° and 0.6° to 7.6° for the generic and subject-specific models, respectively. Our results suggest that methods that rely on talar morphology to define subject-specific axes may be inadequate for accurately predicting tibiotalar and subtalar joint kinematics.

Measurements of joint kinematics are essential to understand the pathomechanics of ankle disease and the effects of treatment. Traditional motion capture techniques do not provide measurements of independent tibiotalar and subtalar joint motion. In this study, high-speed dual fluoroscopy images of ten asymptomatic adults were acquired during treadmill walking at 0.5 m/s and 1.0 m/s and a single-leg, balanced heel-rise. Three-dimensional (3D) CT models of each bone and dual fluoroscopy images were used to quantify in vivo kinematics for the tibiotalar and subtalar joints. Dynamic tibiotalar and subtalar mean joint angles often exhibited opposing trends during captured stance. During both speeds of walking, the tibiotalar joint had significantly greater dorsi/plantarflexion (D/P) angular ROM than the subtalar joint while the subtalar joint demonstrated greater inversion/eversion (In/Ev) and internal/external rotation (IR/ER) than the tibiotalar joint. During balanced heel-rise, only D/P and In/Ev were significantly different between the tibiotalar and subtalar joints. Translational ROM in the anterior/posterior (AP) direction was significantly greater in the subtalar than the tibiotalar joint during walking at 0.5 m/s. Overall, our results support the long-held belief that the tibiotalar joint is primarily responsible for D/P, while the subtalar joint facilitates In/Ev and IR/ER. However, the subtalar joint provided considerable D/P rotation, and the tibiotalar joint rotated about all three axes, which, along with translational motion, suggests that each joint undergoes complex, 3D motion.

Evidence suggests that the tibiotalar and subtalar joints provide near six degree-of-freedom (DOF) motion. Yet, kinematic models frequently assume one DOF at each of these joints. In this study, we quantified the accuracy of kinematic models to predict joint angles at the tibiotalar and subtalar joints from skin-marker data. Models included 1 or 3 DOF at each joint. Ten asymptomatic subjects, screened for deformities, performed 1.0m/s treadmill walking and a balanced, single-leg heel-rise. Tibiotalar and subtalar joint angles calculated by inverse kinematics for the 1 and 3 DOF models were compared to those measured directly in vivo using dual-fluoroscopy. Results demonstrated that, for each activity, the average error in tibiotalar joint angles predicted by the 1 DOF model were significantly smaller than those predicted by the 3 DOF model for inversion/eversion and internal/external rotation. In contrast, neither model consistently demonstrated smaller errors when predicting subtalar joint angles. Additionally, neither model could accurately predict discrete angles for the tibiotalar and subtalar joints on a per-subject basis. Differences between model predictions and dual-fluoroscopy measurements were highly variable across subjects, with joint angle errors in at least one rotation direction surpassing 10° for 9 out of 10 subjects. Our results suggest that both the 1 and 3 DOF models can predict trends in tibiotalar joint angles on a limited basis. However, as currently implemented, neither model can predict discrete tibiotalar or subtalar joint angles for individual subjects. Inclusion of subject-specific attributes may improve the accuracy of these models.

The relationship between altered tibiotalar and subtalar kinematics and development of ankle osteoarthritis is unknown, as skin marker motion analysis cannot measure articulations of each joint independently. Here, we quantified the accuracy and demonstrated the feasibility of high-speed dual fluoroscopy (DF) to measure and visualize the three-dimensional articulation (i.e. arthrokinematics) of the tibiotalar and subtalar joints. Metal beads were implanted in the tibia, talus and calcaneus of two cadavers. Three-dimensional surface models of the cadaver and volunteer bones were reconstructed from computed tomography images. A custom DF system was positioned adjacent to an instrumented treadmill. DF images of the cadavers were acquired during maximal rotation about three axes (dorsal–plantar flexion, inversion–eversion, internal–external rotation) and simulated gait (treadmill at 0.5 and 1.0 m/s). Positions of implanted beads were tracked using dynamic radiostereometric analysis (DRSA). Bead locations were also calculated using model-based markerless tracking (MBT) and compared, along with joint angles and translations, to DRSA results. The mean positional difference between DRSA and MBT for all frames defined bias; standard deviation of the difference defined precision. The volunteer was imaged with DF during treadmill gait. From these movements, joint kinematics and tibiotalar and subtalar bone-to-bone distance were calculated. The mean positional and rotational bias (±standard deviation) of MBT was 0.03 ± 0.35 mm and 0.25 ± 0.81°, respectively. Mean translational and rotational precision was 0.30 ± 0.12 mm and 0.63 ± 0.28°, respectively. With excellent measurement accuracy, DF and MBT may elucidate the kinematic pathways responsible for osteoarthritis of the tibiotalar and subtalar joints in living subjects.

Category: Ankle Introduction/Purpose: Measurements of joint angles and translations (i.e. kinematics) are essential to understand the pathomechanics of ankle disease and functional changes following treatment. Traditional motion capture techniques, which track the positions of reflective markers adhered to the skin, cannot measure motion of the tibiotalar and subtalar joints independent of one another. To overcome this limitation, we used high-speed dual fluoroscopy (DF), an x-ray videography technique, to quantify in-vivo kinematics of healthy asymptomatic ankles during activities of daily living. Using these kinematics as baseline data, our secondary objective was to assess preliminary kinematic differences between chronic ankle instability (CAI) patients and asymptomatic control subjects. Methods: High-speed DF images of the hindfoot of ten healthy, asymptomatic adults and four adults with CAI were acquired during treadmill walking at 0.5 m/s and 1.0 m/s and during a single-leg, balanced heel-rise. Three-dimensional (3D) CT models of the calcaneus, tibia, and talus and DF images served as input to the validated model-based markerless tracking software that quantified in vivo kinematics for the tibiotalar and subtalar joints. Dynamic joint kinematics and mean range of motion (ROM) were calculated and reported as dorsi/plantarflexion (D/P), inversion/eversion (In/Ev) and internal/external rotation (IR/ER) angles or translations along the medial/lateral (ML), anterior/posterior (AP), and superior/inferior (SI) directions. Results: During gait, the tibiotalar joint had significantly greater D/P ROM than the subtalar joint (0.5 m/s: p=0.004; 1.0 m/s: p=0.003). The subtalar joint had significantly greater In/Ev (0.5 m/s: p < 0.001; 1.0 m/s: p < 0.001) and IR/ER (0.5 m/s: p=0.01; 1.0 m/s: p=0.02) ROM than the tibiotalar joint. However, during balanced heel-rise, D/P and In/Ev were significantly different between the two joints (p < 0.001; p < 0.001). For AP translation, subtalar ROM was significantly greater than tibiotalar ROM during walking at 0.5m/s (p=0.002). CAI patients often demonstrated rotational profiles with dynamic trends that fell outside the 95% confidence intervals of the asymptomatic subjects (Figure 1). CAI patients exhibited smaller ROM than asymptomatic subjects. However, only 0.5 m/s tibiotalar SI translational (p=0.049) and 1.0 m/s subtalar In/Ev (p=0.03) ROM were significant. Conclusion: To our knowledge, this is the first study to quantify in-vivo joint angles and translations in asymptomatic and CAI subjects. Our results support the belief that the tibiotalar joint is primarily responsible for D/P, while the subtalar joint facilitates In/Ev and IR/ER. Secondary rotational contributions suggest that both joints undergo complex, 3D motion. Our comparison of CAI and asymptomatic subjects is not conclusive, yet suggests that a larger sample size will detect significant differences. With a larger sample size, dual-fluoroscopy may provide insight into the clinical relevance of altered kinematics and the pathomechanics responsible for ankle instability and other pathologies.