Assistance force-line of exosuit affects ankle multidimensional motion: a theoretical and experimental study.

BACKGROUND: The talocrural joint and the subtalar joint are the two major joints of the ankle-joint complex. The position and direction of the exosuit force line relative to these two joint axes can influence ankle motion. We aimed to understand the effects of different force-lines on ankle multidimensional motion. METHODS: In this article, three assistance force line schemes for ankle exosuits were proposed: perpendicular to the talocrural joint axis (PT), intersecting with the subtalar joint axis (IS), and parallel to the triceps surae (PTS). A theoretical model was proposed to calculate the exosuit's assistance moment. Seven participants completed four experimental tests of ankle plantarflexion, including three passive motions assisted by the PT, PTS and IS schemes, and one active motion without exosuit assistance (Active). RESULTS: The simulation results demonstrated that all three exosuits were able to produce significant moments of ankle plantarflexion. Among these, the PT scheme exhibited the highest moments in all dimensions, followed by the PTS and IS schemes. The experimental findings confirmed the effectiveness of all three exosuit schemes in assisting ankle plantarflexion. Additionally, as the assistive force lines approached the subtalar joint, there was a decrease in ankle motion assisted by the exosuits in non-plantarflexion directions, along with a reduction in the average distance of ankle angle curves relative to active ankle motion. Furthermore, the linear correlation coefficients between inversion and plantarflexion, adduction and plantarflexion, and adduction and inversion gradually converged toward active ankle plantarflexion motion. CONCLUSIONS: Our research indicates that the position of the exosuit force line to the subtalar joint has a significant impact on ankle inversion and adduction. Among all three schemes, the IS, which has the closest distance to the subtalar joint axes, has the greatest kinematic similarity to active ankle plantarflexion and might be a better choice for ankle assistance and rehabilitation.

In Silico Analysis of Bone Tension During Fixation of the Medial Malleolus Fracture After Ankle Joint Endoprosthesis.

Total ankle arthroplasty (TAR) is a procedure alternative to arthrodesis which enables the biomechanical stabilization of the ankle joint. The procedure is associated with a high risk of complications, including fractures of the medial malleolus. In this study, the finite element method (FEM), based on CT examinations, was used to model the ankle fracture fixation after TAR. Three types of fracture stabilization were considered: screw, Blount staple, and both screw and Blount staple. In the in silico model, the maximum stress tension was found at prosthetic junctions with the base, cone, and talar components of the tibial prosthesis. When the fracture was stabilized with the Blount staple, tension along the cone of the tibial component was about 12% of the maximum tension. Stabilizations with the screw alone or Blount staple combined with a screw on the medial side of the cone induced tension in the immediate vicinity twice as high. In the area of the medial malleolus, the tension was alike for both types of stabilization. The tension was lowest when using the Blount staple alone. We conclude that, contrary to the hitherto clinical routine of using screws, fracture fixation using the Blount staple leads to the lowest bone tension around the fixation of the medial malleolus fracture after ankle joint endoprosthesis.

Three-dimensional analysis of shape variations and symmetry of the fibula, tibia, calcaneus and talus.

The bones forming the talocrural joint (TCJ) and subtalar joint (STJ) are often assumed to be bilaterally symmetric. Therefore, the contralateral limb (i.e. the fibula, tibia, calcaneus and talus) is used as a template or an intra-subject control in clinical and research practice. However, the validity of the symmetry assumption is controversial, because insufficient information is available on the shape variations and bilateral (a)symmetry of the fibula, tibia, calcaneus and talus. Using three-dimensional spatially dense sampled representations of bone shapes extracted from bilateral computed tomography scans of 66 individuals (55 male, mean age: 61 ±â€…10 years; 11 female, mean age: 53 ±â€…15 years), we analyzed whether: (i) similar shape patterns exist in the left and right bones of the same type; (ii) gender has an effect on bone shape variations; (iii) intra-subject shape variation is smaller than that of inter-subject for a given shape variance direction. For the first set of analyses, all left and right instances of the same type of bone were considered as two separate groups, and statistically compared with each other on multiple aspects including group location (central tendency), variance-covariance scale (dispersion) and orientation (covariance structure) using distance-based permutational tests. For the second and third sets of analyses, all left and right bones of the same type were pooled into one group, and shape variations in the TCJ and STJ bones were extracted using principal component analysis. The effects of gender on age-adjusted bone shape differences were assessed using an analysis of covariance. Moreover, intra-class correlation was employed to evaluate intra- and inter-subject bone shape variations. For each bone type, both sides had similar shape patterns (Ppermutational -values > 0.05). After Bonferroni adjustment, gender led to shape differences, which were mainly in the lateral and medial condyles of the tibia (P = 0.003), the length and height of the calcaneus (P < 0.001), the posterior and anterior talar articular surfaces of the calcaneus (P = 0.001), and in the posterior aspect of the talus (P = 0.001). Intra-subject shape variations in the tibial tuberosity together with the diameter of the tibia, and the curvature of the fibula shaft and the diameter of the fibula were as high as those of inter-subject. This result suggests that the shape symmetry assumption could be violated for some specific shape variations in the fibula and tibia.

The geometrical axis of the talocrural joint-Suggestions for a new measurement of the talocrural joint axis.

BACKGROUND: Despite intensive research there is no consensus about the talocrural joint axis. The aim of the present study is a new method to determinate the geometric rotational axis of the talocrural joint. METHODS: We analyzed 98 CT-scans of full cadaver Caucasian legs. We generated three-dimensional reconstruction models of the talus. A best fitting cone was orientated to the talar articular surface. The geometric rotational axis was defined to be the axis of this cone. RESULTS: The geometric rotational axis of the talocrural joint is orientated from lateral-distal to medial-proximal (85.6°±10 compared to anatomical tibial axis in torsional plane), from posterior-distal to anterior-proximal (81.43°±44.35 compared to anatomical tibial axis in sagittal plane) and from posterior-medial to anterior-lateral (169.2°±5.91 compared to intermalleolar axis in axial plane). CONCLUSIONS: The consideration of our results might be helpful for better understanding of ankle biomechanics.

Ankle morphometry based on computerized tomography.

BACKGROUND: Thorough understanding of the morphometry of the ankle joint is crucial to optimize conservative and operative therapy of ankle joint disorders. Despite recent improvements, basic anatomic and biomechanical correlations of the ankle joint including the orientation of the ankle joint axis and joint morphology as its key biomechanical features are not sufficiently recorded to date. The aim of this study was the evaluation of the ankle morphometry to gain information about the ankle joint axis. MATERIAL AND METHODS: In this study 98 high-resolution CT-scans of complete Caucasian cadaver legs were analysed. Using the software Mimics and 3-Matic (Materialize) 22 anatomic parameters of the talocrural joint were assessed, including the length, width and surface area of the tibial and talar articular areas. Additionally, the radii of the articular areas, the medial distal tibial angle and the height of the talar dome were determined. RESULTS: The radius of the central trochlea tali was 44.6±4.1mm (mean±SD). The central trochlea tali arc length was 40.8±3.0mm and its width was 27.4±2.5mm. Additionally we determined 47.0±4.4mm for the tibial sagittal radius, 27.6±3.0mm for the tibial arc length and 27.4±2.5mm for the central tibial width. CONCLUSION: The present study describes the three-dimensional morphometry of Caucasian ankle joints in detail. This dimensional analysis of the ankle joint will inform the development and placements of implants and prostheses.

Three-Dimensional Registration of Freehand-Tracked Ultrasound to CT Images of the Talocrural Joint.

A rigid surface⁻volume registration scheme is presented in this study to register computed tomography (CT) and free-hand tracked ultrasound (US) images of the talocrural joint. Prior to registration, bone surfaces expected to be visible in US are extracted from the CT volume and bone contours in 2D US data are enhanced based on monogenic signal representation of 2D US images. A 3D monogenic signal data is reconstructed from the 2D data using the position of the US probe recorded with an optical tracking system. When registering the surface extracted from the CT scan to the monogenic signal feature volume, six transformation parameters are estimated so as to optimize the sum of monogenic signal features over the transformed surface. The robustness of the registration algorithm was tested on a dataset collected from 12 cadaveric ankles. The proposed method was used in a clinical case study to investigate the potential of US imaging for pre-operative planning of arthroscopic access to talar (osteo)chondral defects (OCDs). The results suggest that registrations with a registration error of 2 mm and less is achievable, and US has the potential to be used in assessment of an OCD' arthroscopic accessibility, given the fact that 51% of the talar surface could be visualized.

Outcomes of Locking-Plate Fixation for Hindfoot Fusion Procedures in 15 Patients.

Tibiotalocalcaneal arthrodesis is a salvage procedure for various end-stage foot and ankle pathologic entities. Several factors are known to influence the union rate after these procedures, including construct rigidity. The data on locked plates as a fixation technique have been inconclusive, with variable union rates reported. One recent study suggested that locking plates can lead to high nonunion rates owing to excessive rigidity. The purpose of the present study was to retrospectively examine the outcomes of locking plate fixation. We retrospectively reviewed the cases of 15 patients (7 [46.7%] male, 8 [53.3%] female) who underwent tibiotalocalcaneal, tibiocalcaneal, or tibiotalar arthrodesis fixed with a locking plate from January 2013 to January 2014. The average age was 52.19 ± 5.8 years. The mean follow-up period was 17 ± 5.3 months. We examined the overall union rates and the effects of smoking, diabetes, and rheumatologic status on the union rate. Of the 15 cases, 11 (73.3%) did not achieve union. The mean time to failure was 10 ± 5.3 months. Age, gender, smoking, diabetes, use of augmentation screws outside the plate, and operating surgeon did not have an effect on the failure rate (p > .50). In addition, gender, smoking, and diabetes did not predict for nonunion. The high failure rate of rigid locking plate fixation reported might be attributable to the high incidence of smoking and diabetic comorbidities in our study. However, excessive construct rigidity might play an important role. Larger studies are needed to establish more reliable union rates with the use of locking plates in foot and ankle fusion.

Bone shape difference between control and osteochondral defect groups of the ankle joint.

OBJECTIVE: The etiology of osteochondral defects (OCDs), for which the ankle (talocrural) joint is one of the common sites, is not yet fully understood. In this study, we hypothesized that bone shape plays a role in development of OCDs. Therefore, we quantitatively compared the morphology of the talus and the distal tibia between an OCD group and a control group. METHODS: The shape variations of the talus and distal tibia were described separately by constructing two statistical shape models (SSMs) based on the segmentation of the bones from ankle computed tomography (CT) scans obtained from control (i.e., 35 CT scans) and OCD (i.e., 37 CT scans) groups. The first five modes of shape variation for the SSM corresponding to each bone were statistically compared between control and OCD groups using an analysis of variance (ANOVA) corrected with the Bonferroni for multiple comparisons. RESULTS: The first five modes of variation in the SSMs respectively represented 49% and 40% of the total variance of talus and tibia. Less than 5% of the variance per mode was described by the higher modes. Mode 5 of the talus (P = 0.004) primarily describing changes in the vertical neck angle and Mode 1 of the tibia (P < 0.0001) representing variations at the medial malleolus, showed statistically significant difference between the control and OCD groups. CONCLUSION: Shape differences exist between control and OCD groups. This indicates that a geometry modulated biomechanical behavior of the talocrural joint may be a risk factor for OCD.

The influence of gastrocnemius stretching combined with joint mobilization on weight-bearing ankle dorsiflexion passive range of motion.

[Purpose] The purpose of this study was to investigate the effect of gastrocnemius stretching combined with talocrural joint mobilization on weight-bearing ankle dorsiflexion passive range of motion. [Subjects] Eleven male subjects with bilateral limited ankle dorsiflexion passive range of motion with knee extended participated in this study. [Methods] All subjects received talocrural joint mobilization while performing gastrocnemius stretching. Ankle dorsiflexion passive range of motion was measured using an inclinometer under weight-bearing conditions before and immediately after intervention. A paired t-test was used to analyze the difference between weight-bearing ankle dorsiflexion passive range of motion pre- and post-intervention. [Results] A significant increase in weight-bearing ankle dorsiflexion passive range of motion was found post-intervention compared with pre-intervention. [Conclusion] These findings demonstrate that gastrocnemius stretching combined with joint mobilization is effective for increasing weight-bearing ankle dorsiflexion passive range of motion.

Influence of reduced passive ankle dorsiflexion range of motion on lower limb kinetics and stiffness during gait.

BACKGROUND: The ankle dorsiflexion range of motion (ADF-ROM) during single support phase allows elastic energy storage in the calcaneal tendon, contributing to advance the body forward. Reduced ADF-ROM may influence lower limb kinetics and stiffness. RESEARCH QUESTION: What is the influence of reduced passive ADF-ROM on lower limb internal moments and stiffness during gait? METHODS: Thirty-two participants, classified into two groups according to passive ADF-ROM (smaller than 10° and greater than 15°), were submitted to gait assessment at self-selected speed with a force platform and a three-dimensional motion analysis system. Statistical parametrical mapping (SPM) analyses were used to compare the lower limbs' internal moments between groups. Independent t-tests analyzed the differences between groups on lower limb stiffness during gait. RESULTS: The lower ADF-ROM group had greater knee flexor moment (terminal stance and push-off), greater ankle abductor (i.e., shank internal rotator) moment in terminal stance and greater knee internal rotator moment in mid to terminal stance. The lower ADF-ROM group also had higher lower limb stiffness during gait. SIGNIFICANCE: Individuals with reduced passive ADF-ROM had greater lower limb stiffness and adopted a gait pattern with increased knee and ankle moments, suggesting increased loading at these joints.

Anatomical evaluations of the adipose tissue surrounding the flexor hallucis longus tendon.

This study aimed to evaluate the presence of adipose tissue surrounding the flexor hallucis longus (FHL) tendon through gross dissection and magnetic resonance imaging (MRI). Grossly, we observed the FHL tendon and surrounding tissues in nine cadavers. Using MRI, we quantitatively evaluated each tissue from the horizontal plane in 40 healthy ankles. Macroscopic autopsy revealed the presence of adipose tissue behind the ankle joint between the FHL and fibula, and horizontal cross-sections showed an oval-shaped adipose tissue surrounding the tendon. The cross-sectional area on MRI was 14.4 mm2 (11.7-16.7) for the FHL tendon and 120.5 mm2 (100.3-149.4) for the adipose tissue. Additionally, the volume of the adipose tissue was 963.3 mm3 (896.2-1115.6). There is an adipose tissue around FHL tendon and maybe this close anatomical relationship might influence the function of the tendon and be involved in its pathologies.

Effects of added trunk load on the in vivo kinematics of talocrural and subtalar joints during landing.

BACKGROUND: Landing from heights is a common movement for active-duty military personnel during training. And the additional load they carry while performing these tasks can affect the kinetics and ankle kinematic of the landing. Traditional motion capture techniques are limited in accurately capturing the in vivo kinematics of the talus. This study aims to investigate the effect of additional trunk load on the kinematics of the talocrural and subtalar joints during landing, using a dual fluoroscopic imaging system (DFIS). METHODS: Fourteen healthy male participants were recruited. Magnetic resonance imaging was performed on the right ankle of each participant to create three-dimensional (3D) models of the talus, tibia, and calcaneus. High-speed DFIS was used to capture the images of participants performing single-leg landing jumps from a height of 40 cm. A weighted vest was used to apply additional load, with a weight of 16 kg. Fluoroscopic images were acquired with or without additional loading condition. Kinematic data were obtained by importing the DFIS data and the 3D models in virtual environment software for 2D-3D registration. The kinematics and kinetics were compared between with or without additional loading conditions. RESULTS: During added trunk loading condition, the medial-lateral translation range of motion (ROM) at the talocrural joint significantly increased (p < 0.05). The subtalar joint showed more extension at 44-56 ms (p < 0.05) after contact. The subtalar joint was more eversion at 40-48 ms (p < 0.05) after contact under the added trunk load condition. The peak vertical ground reaction force (vGRF) significantly increased (p < 0.05). CONCLUSIONS: With the added trunk load, there is a significant increase in peak vGRF during landing. The medial-lateral translation ROM of the talocrural joint increases. And the kinematics of the subtalar joint are affected. The observed biomechanical changes may be associated with the high incidence of stress fractures in training with added load.

Hindfoot kinematics and kinetics - A combined in vivo and in silico analysis approach.

BACKGROUND: The complex anatomical structure of the foot-ankle imposes challenges to accurately quantify detailed hindfoot kinematics and estimate musculoskeletal loading parameters. Most systems used to capture or estimate dynamic joint function oversimplify the anatomical structure by reducing its complexity. RESEARCH QUESTION: Can four dimensional computed tomography (4D CT) imaging in combination with an innovative foot manipulator capture in vivo hindfoot kinematics during a simulated stance phase of walking and can talocrural and subtalar articular joint mechanics be estimated based on a detailed in silico musculoskeletal foot-ankle model. METHODS: A foot manipulator imposed plantar/dorsiflexion and inversion/eversion representing a healthy stance phase of gait in 12 healthy participants while simultaneously acquiring 4D CT images. Participant-specific 3D hindfoot rotations and translations were calculated based on bone-specific anatomical coordinate systems. Articular cartilage contact area and contact pressure of the talocrural and subtalar joints were estimated using an extended foot-ankle model updated with an elastic foundation contact model upon prescribing the participant-specific rotations measured in the 4D CT measurement. RESULTS: Plantar/dorsiflexion predominantly occurred at the talocrural joint (RoM 15.9±3.9°), while inversion/eversion (RoM 5.9±3.9°) occurred mostly at the subtalar joint, with the contact area being larger at the subtalar than at the talocrural joint. Contact pressure was evenly distributed between the talocrural and subtalar joint at the beginning of the simulated stance phase but was then redistributed from the talocrural to the subtalar joint with increasing dorsiflexion. SIGNIFICANCE: In a clinical case study, the healthy participants were compared with four patients after surgically treaded intra-articular calcaneal fracture. The proposed workflow was able to detect small but meaningful differences in hindfoot kinematics and kinetics, indicative of remaining hindfoot pathomechanics that may influence the onset and progression of degenerative joint diseases.

Combining specific task-oriented training with manual therapy to improve balance and mobility in patients after stroke: a mixed methods pilot randomised controlled trial.

PURPOSE: In absence of existing studies, to describe changes in balance and mobility, following specific task-oriented training (TOT), its combination with talocrural manual therapy (MT-TOT) or no intervention, in chronic stroke patients. To explore the feasibility of a full-scale randomised controlled trial (RCT) based on criteria of recruitment, retention and adherence rates, adverse events, falls and acceptability of the intervention. MATERIALS AND METHODS: Using an assessor-blinded pilot RCT, 36 stroke patients were allocated to either MT-TOT, TOT, or controls. Supervised interventions were performed 45 min, 2×/weekly, for 4 weeks, and home-based practice 20 min, 4x/weekly for 4 weeks. Qualitative interviews evaluated intervention acceptability. Outcomes of balance, mobility, ankle dorsiflexion range of motion (ROM), falls and health-related quality of life (HRQoL) were assessed at baseline, post-intervention and 4-week follow-up. RESULTS: Preliminary efficacy of MT-TOT and TOT was shown in improving balance (effect size 0.714), walking speed (0.683), mobility (0.265), dual-tasking mobility (0.595), falls (0.037), active and passive talocrural ROM (0.603; 0.751) and activities and social participation related HRQoL domains (0.332-0.784) in stroke patients. The feasibility of a larger RCT was confirmed. CONCLUSIONS: Specific MT-TOT and TOT appeared effective and are feasible in stroke patients. A larger RCT is needed to validate the results.Trial Registration: German Clinical Trials Register, DRKS00023068. Registered on 21.09.2020, https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00023068.

A specific goal- and task-oriented training involving timed mobility and dynamic balance activities based on the demands of daily life, of high intensity and progressed in difficulty according to predefined criteria is feasible in patients after stroke.In this mixed methods pilot study patients indicated high acceptability of task-oriented training with and without ankle mobilisations, with their descriptions being in line with the Theoretical Framework of Acceptability.Specific task-oriented training and its combination with talocrural joint manual therapy improved balance, mobility, talocrural dorsiflexion range of motion and some domains of health-related quality of life in people after stroke.

Effects of fatigue on the in vivo kinematics and kinetics of talocrural and subtalar joint during landing.

Objective: Fatigue can affect the ankle kinematic characteristics of landing movements. Traditional marker-based motion capture techniques have difficulty in accurately obtaining the kinematics of the talocrural and subtalar joints. This study aimed to investigate the effects of fatigue on the talocrural and subtalar joints during the landing using dual fluoroscopic imaging system (DFIS). Methods: This study included fourteen healthy participants. The foot of each participant was scanned using magnetic resonance imaging to create 3D models. High-speed DFIS was used to capture images of the ankle joint during participants performing a single-leg landing jump from a height of 40 cm. Fatigue was induced by running and fluoroscopic images were captured before and after fatigue. Kinematic data were obtained by 3D/2D registration in virtual environment software. The joint kinematics in six degrees of freedom and range of motion (ROM) were compared between the unfatigued and fatigued conditions. Results: During landing, after the initial contact with the ground, the main movement of the talocrural joint is extension and abduction, while the subtalar joint mainly performs extension, eversion, and abduction. Compared to unfatigued, during fatigue the maximum medial translation (1.35 ± 0.45 mm vs. 1.86 ± 0.69 mm, p = 0.032) and medial-lateral ROM (3.19 ± 0.60 mm vs. 3.89 ± 0.96 mm, p = 0.029) of the talocrural joint significantly increased, the maximum flexion angle (0.83 ± 1.24° vs. 2.11 ± 1.80°, p = 0.037) of the subtalar joint significantly increased, and the flexion-extension ROM (6.17 ± 2.21° vs. 7.97 ± 2.52°, p = 0.043) of the subtalar joint significantly increased. Conclusion: This study contributes to the quantitative understanding of the normal function of the talocrural and subtalar joints during high-demand activities. During landing, the main movement of the talocrural joint is extension and abduction, while the subtalar joint mainly performs extension, eversion, and abduction. Under fatigue conditions, the partial ROM of the talocrural and subtalar joints increases.

Establishing a New Patient-Specific Implantation Technique for Total Ankle Replacement: An In Vitro Study.

BACKGROUND: Revision rates after total ankle replacements (TARs) are higher compared with other total joint replacements. The present study aimed to establish a new patient-specific implantation (PSI) technique for TAR. MATERIAL AND METHODS: A total of 10 complete Caucasian cadaver legs had whole leg computed tomography scans. The individual geometrical ankle joint axis was determined, and based on this axis, the position of the prosthesis was planned. We assessed prosthesis placement, guiding block position, and preoperative and postoperative ankle rotational axes. RESULTS: The guiding block position interobserver reliability was 0.37 mm 0.45 (mean ± SD) for the tibial guiding block. The value for the first talar guiding block was 1.72 ± 1.3 mm and for the second talar guiding block, 0.61 ± 0.39 mm. The tibial slope as well as the frontal angles of the anatomical tibial axis compared to the tibial and talar articular surfaces showed no statistically relevant differences with numbers available. The deviation of the assessed preoperative joint axis to the postoperative joint axis was 14.6° ± 7.8. CONCLUSION: The present study describes the results of an establishing process of a new PSI technique for TAR. The reliability of guiding block positioning and, thereby, prosthesis placement is sufficient. LEVEL OF EVIDENCE: Biomechanical study.

Repeatability, reproducibility, and agreement of three methods for finding the mechanical axis of the human tibia.

BACKGROUND: Identifying the center of the talocrural joint is crucial in defining the tibia's mechanical axis, which is used in a variety of applications such as a reference for measuring alignment variables following total knee arthroplasty. The objectives of this study were to 1) describe a new method for determining the center of the talocrural joint, 2) determine the repeatability and reproducibility of the new method and two previously described methods for locating the center, 3) determine the limits of agreement between pairs of methods, and 4) determine angular differences in the coronal and sagittal planes between tibial mechanical axes generated by the different methods. METHODS: The new area centroid method identified the center of the talocrural joint as the centroid of the distal tibia's articular surface. Previously described methods included the diagonal intersection and biplanar methods. For each method, the medial-lateral, anterior-posterior, and proximal-distal coordinates of the talocrural joint center and angular differences between tibial mechanical axes were determined in thirteen 3D full tibia bone models. RESULTS: For the area centroid method, ICC values indicated excellent repeatability (0.97) and reproducibility (0.92). For the biplanar method, ICC values indicated good repeatability (0.86) and fair reproducibility (0.40). For the diagonal intersection method, ICC values indicated moderate repeatability (0.71) and fair reproducibility (0.46). Limits of agreement were tightest between the area centroid and diagonal intersection methods (± 4.1 mm). Angular differences between tibial mechanical axes were limited to 3°. CONCLUSION: The area centroid method locates the anatomic center of the talocrural joint, offers better repeatability and reproducibility than existing methods, and is recommended when identifying the tibial mechanical axis.

Gravity stress tibiotalar laxity evaluation with a biomedical gyroscopes device - cadaver study with progressive sectioning of lateral ankle ligaments.

PURPOSE: Despite the evidence on the role of gravity stress test to access the instability of other ankle injuries, there is limited literature regarding gravity stress on the lateral ankle ligament's insufficiency. The objective of our study was to objectively measure the tibiotalar angular movement under gravity stress after progressive sectioning of the lateral ankle ligaments. METHODS: We performed sequential sectioning of the anterior talofibular (ATFL), calcaneofibular (CFL), and posterior talofibular ligaments (PTFL) in twelve ankle specimens. Under gravity stress, we measured the angular movement of the talus in relation to the tibia. The measuring device is based on a three-axis gyroscope and accelerometer. RESULTS: Comparing to the intact condition, the plantar flexion increased on average 1.78° (95% confidence interval [CI] 1.15;2.42), 5.13° (95%CI 3.10;7.16) and 8.63° (95%CI 6.05;11.22), the rotation increased by 1.00° (95 CI -0.51;2.51), 3.68° (95%CI 1.97;5.40) and 15.62° (95%CI 10.09;21.14), and the varus increased 2.89° (95% CI 1.39, 4.39), 8.12° (95% CI 5.16, 11.07) and 11.68° (95% CI 7.91, 15.46), after sectioning the ATFL, CFL, and PTFL, respectively. The overall changes were statistically significant. CONCLUSIONS: There was a significant tibiotalar laxity after sectioning of lateral ankle ligaments when the foot position is influenced only by gravity. The tibiotalar angular displacement was significant when the CFL and PTFL were cut which suggests that the gravity test could be used to assess combined lateral ankle ligament injury. This evidence might be a step forward in the development of lateral ankle ligaments gravity stress tests. LEVEL OF EVIDENCE: 5 (cadaver study).

Comparative anatomy of the mouse and human ankle joint using Micro-CT: Utility of a mouse model to study human ankle sprains.

The use of mouse models as a tool to study ankle sprain requires a basic understanding of the similarities and differences between human and mouse ankle joint anatomy. However, few studies have been conducted that address the merits and drawbacks of these differences in the functioning of joints. Twenty hindfoot specimens were obtained from 10 male C57BL/6J mice and scanned using micro-CT. The foot and ankle skeletal structures were reconstructed in three dimensions. Morphological parameters were then measured using a plane projection method and normalized data were compared with those of human ankles. There was no significant difference in the malleolar width, maximal tibial thickness, tibial arc length, trochlea tali arc length or trochlea tali width of the mouse specimens compared with the human model. However, a groove was observed on the talar dome in the mouse specimens which was not observed in humans, the talar dome being more symmetric. The mouse ankle was to a large extent able to mimic the mechanism of a human ankle and so a mouse model could be appropriate for expanding our understanding of ankle biomechanics in general. However, the structural differences in the talar dome in the mouse and human should not be ignored. Although there are some differences in the mouse and human ankle that cannot be ignored, compared to other animals, the human ankle is more similar to that of the mouse.

Ankle Osteoarthritis - Arthroplasty or Arthrodesis?

Osteoarthritis of the talocrural joint accounts for only 4% of cases of degenerative disease of the musculo-skeletal system. Unlike other joints, idiopathic OA of the ankle joint is identified in only 7% of patients. Until the end of the 1960's, arthrodesis was the treatment of choice in advanced OA of ankle joint. Absolute indi-ca-tions for arthrodesis include irreversible loss of joint anatomy, neurological conditions, advanced osteoporosis and chronic inflammation. Currently, the surgical treatment of ankle joint OA relies on third-generation endo-prostheses of the ankle. Arthroplasty is indicated in patients under 60 years of age with no history of non-ortho-paedic co-morbidities, engaging in little physical activity, with an intact joint axis and satisfactory mobility and non-smoking. This article analyzes the available literature on the results of surgical treatment in patients with osteoarthritis of the talocrural joint treated with arthrodesis or arthroplasty, taking into consideration the strict indications for each of these surgical methods.