Three-dimensional morphometric study of the trapezium shape of the trochlea tali

Anthropomorphic Characterization of Ankle Joint

Even though total ankle replacement has emerged as an alternative treatment to arthrodesis, the long-term clinical results are unsatisfactory. Proper design of the ankle device is required to achieve successful arthroplasty results. Therefore, a quantitative knowledge of the ankle joint is necessary. In this pilot study, imaging data of 22 subjects (with both females and males and across three age groups) was used to measure the morphological parameters of the ankle joint. A total of 40 measurements were collected by creating sections in the sagittal and coronal planes for the tibia and talus. Statistical analyses were performed to compare genders, age groups, and image acquisition techniques used to generate 3D models. About 13 measurements derived for parameters (TiAL, SRTi, TaAL, SRTa, TiW, TaW, and TTL) that are very critical for the implant design showed significant differences (p-value < 0.05) between males and females. Young adults showed a significant difference (p-value < 0.05) compared to adults for 15 measurements related to critical tibial and talus parameters (TiAL, TiW, TML, TaAL, SRTa, TaW, and TTL), but no significant differences were observed between young adults and older adults, and between adults and older adults for most of the parameters. A positive correlation (r > 0.70) was observed between tibial and talar width values and between the sagittal radius values. When compared with morphological parameters obtained in this study, the sizes of current total ankle replacement devices can only fit a very limited group of people in this study. This pilot study contributes to the comprehensive understanding of the effects of gender and age group on ankle joint morphology and the relationship between tibial and talus parameters that can be used to plan and design ankle devices.

Lower Limb Biomechanics During Drop-Jump Landings on Challenging Surfaces in Individuals With Chronic Ankle Instability

CONTEXT

Individuals with chronic ankle instability (CAI) exhibit impaired lower limb biomechanics during unilateral drop-jump landings on a flat surface. However, lower limb biomechanical adaptations during unilateral drop-jump landings on more challenging surfaces, such as those that are unstable or inclined, have not been described.

OBJECTIVE

To determine how unilateral drop-jump landing surfaces (flat, unstable, and inclined) influence lower limb electromyography, kinematics, and kinetics in individuals with CAI.

DESIGN

Descriptive laboratory study.

SETTING

Biomechanics laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 22 young adults (age = 24.9 ± 4.9 years, height = 1.68 ± 0.08 m, mass = 70.6 ± 11.4 kg) with CAI.

INTERVENTION(S)

Participants completed 5 trials each of unilateral drop-jump landings on a flat surface (DROP), an unstable surface (FOAM), and a laterally inclined surface (WEDGE).

MAIN OUTCOME MEASURE(S)

Electromyography of the gluteus medius, vastus lateralis, gastrocnemius medialis, peroneus longus, and tibialis anterior muscles was recorded. Ankle and knee angles and moments were calculated using a 3-dimensional motion-analysis system and a force plate. Biomechanical variables were compared among tasks using 1-dimensional statistical nonparametric mapping.

RESULTS

During DROP, greater ankle-dorsiflexion and knee-extension moments were observed than during FOAM and WEDGE and greater vastus lateralis muscle activity was observed than during FOAM. Greater ankle-inversion and plantar-flexion angles were noted during FOAM and WEDGE than during DROP. Peroneus longus muscle activity was greater during DROP than during FOAM. During FOAM, greater ankle-inversion and knee-extension angles and ankle-inversion and internal-rotation moments, as well as less peroneus longus muscle activity, were present than during WEDGE.

CONCLUSIONS

The greater ankle-inversion and plantar-flexion angles as well as the lack of increased peroneus longus muscle activation during the FOAM and WEDGE conditions could increase the risk of recurrent lateral ankle sprain in individuals with CAI. These findings improve our understanding of the changes in lower limb biomechanics when landing on more challenging surfaces and will help clinicians better target deficits associated with CAI during rehabilitation.

Shape Approximation and Size Difference of the Upper Part of the Talus: Implication for Implant Design of the Talar Component for Total Ankle Replacement

The implant design of the talar component for total ankle replacement (TAR) should match the surface morphology of the talus so that the replaced ankle can restore the natural motion of the tibiotalar joint and may reduce postoperative complications. The purpose of this study was to introduce a new 3D fitting method (the two-sphere fitting method of the talar trochlea with three fitting resection planes) to approximate the shape of the upper part of the talus for the Chinese population. 90 models of the tali from CT images of healthy volunteers were used in this study. Geometrical fitting and morphological measurements were performed for the surface morphology of the upper part of the talus. The accuracy of the two-sphere fitting method of the talar trochlea was assessed by a comparison of previously reported data. Parameters of the fitting geometries with different sizes were recorded and compared. Results showed that compared with previously reported one-sphere, cylinder, and bitruncated cone fitting methods, the two-sphere fitting method presented the smallest maximum distance difference, indicating that talar trochlea can be approximated well as two spheres. The radius of the medial fitting sphere $R_M$ was $20.69\pm 2.19$  mm which was significantly smaller than the radius of the lateral fitting sphere $R_L$ of $21.32\pm 1.88$  mm. After grouping all data by the average radius of fitting spheres, the result showed that different sizes of the upper part of the talus presented significantly different parameters except the orientation of the lateral cutting plane, indicating that the orientation of the lateral cutting plane may keep consistent for all upper part of the talus and have no relationship with the size. The linear regression analyses demonstrated a weak correlation ( $R^2<0.5$ ) between the majority of parameters and the average radius of the fitting spheres. Therefore, different sizes of the upper part of the talus presented unique morphological features, and the design of different sizes of talar components for TAR should consider the size-specific characteristics of the talus. The parameters measured in this study provided a further understanding of the talus and can guide the design of different sizes of the talar components of the TAR implant.

The influence of footwear on walking biomechanics in individuals with chronic ankle instability

BACKGROUND/PURPOSE

The effects of footwear on the walking kinematics, kinetics and electromyography (EMG) of individuals with chronic ankle instability (CAI) at different speeds are still unknown. The objective of this cross-sectional study was to evaluate the kinematic, kinetic and electromyography differences between shod and barefoot walking at comfortable (CW) and fast (FW) speeds in individuals with CAI.

METHODS

Twenty-one individuals with CAI walked on a 5-meter walkway shod and barefoot at CW and FW speeds. A force plate was used to record the ground reaction forces, a 3-D motion analysis system to record the lower limb kinematics and a surface EMG system to collect the gluteus medius, vastus lateralis, gastrocnemius lateralis, gastrocnemius medialis, peroneus longus and tibialis anterior muscles activity. The dependent variables were ankle and knee angles and moments and normalized muscle activity. The shod and barefoot data during CW and FW were compared using a one-dimensional non-parametric mapping analysis.

RESULTS

The main results of this study were that individuals with CAI exhibited more ankle dorsiflexion angle, knee extension and tibialis anterior muscle activation during the beginning of the stance phase during shod compared to barefoot walking. Also, the biomechanical effects of shoes are similar during walking at FW and CW.

CONCLUSION

The biomechanical deficits associated with CAI were partly attenuated during the shod compared to the barefoot condition and these effects were similar at CW and FW. These findings are compatible with the concept that locomotor interventions using suitable shoes may enhance gait abilities in individuals with CAI.

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 ± 10 years; 11 female, mean age: 53 ± 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 (P_{permutational}‐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.

Morphomics of the Talus

Previous studies of frontal crash databases reported that ankle fractures are among the most common lower extremity fractures. While not generally life threatening, these injuries can be debilitating. Laboratory research into the mechanisms of ankle fractures has linked dorsiflexion with an increased risk of tibia and fibula malleolus fractures. However, talus fractures were not produced in the laboratory tests and appear to be caused by more complex loading of the joint. In this study, an analysis of the National Automotive Sampling System - Crashworthiness Data System (NASS-CDS) for the years 2004-2013 was conducted to investigate foot-ankle injury rates in front seat occupants involved in frontal impact crashes. A logistic regression model was developed indicating occupant weight, impact delta velocity and gender to be significant predictors of talus fracture (p<0.05). Separately, a specific set of Computed Tomography (CT) scans from the International Center for Automotive Medicine (ICAM) scan database was used to characterize the talar dome. This control population consisted of 207 adults aged 18 to 84, with no foot or ankle trauma, and scans that had suitable coverage of the talus. Size of the talus was determined using medial-to-lateral width and anterior-to-posterior depth measurements. Geometry was assessed by evaluating the radius of the articulating talus and strength was assessed using a combination of cross sectional area and density. Demographics were studied to investigate correlation with talus measurements from the CT scan database. A multi-variable linear regression model of the morphomics showed gender to be statistically significant (p<0.05) for talus depth, width, cross-sectional area, radius and strength. Body Mass Index (BMI) was significant for depth and radius. Weight was significant for depth, width, density and strength. Stature was significant for depth, cross-sectional area, radius and strength. Age was significant for radius and density.

How to drill the talar tunnel in ATFL reconstruction?

PURPOSE

Reconstruction of the anterior talofibular ligament may be indicated in cases of residual instability after conservative treatment. Often, a bone tunnel is used for fixation in the talar bone. The purpose of this study is to evaluate possible routes for drilling the talar tunnel.

METHODS

Virtual tunnels were generated in a 3D bone model, oriented towards the following external landmarks: the talar neck, the most anterior point of the medial malleolus (MM), the most distal point of the MM, the most medial point of the MM, and the most posterior point of the MM. The parameters analysed for tunnels with lengths of 20, 25, and 30 mm were the maximum distance inside the bone and the distance from the tunnel to the bone surface. A minimal safe distance (MSD) was calculated for a tunnel with a diameter of 5 mm.

RESULTS

The shortest measured distance before arriving outside the talar bone was 16.7 mm. The longest distances were obtained in the tunnels oriented towards the talar neck (mean value of 36.6, SD 2.8) and towards the most posterior point of the MM (mean value of 35.8, SD 0.3). Only one tunnel, measuring 20 mm in depth and oriented towards the most posterior point of the MM, revealed no individual values below the MSD.

CONCLUSION

External landmarks are useful for drilling a talar tunnel during reconstruction of the anterior talofibular ligament. Only one tunnel, oriented towards the most posterior point of the MM, measuring 5 mm in diameter and with a maximum depth of 20 mm, was safe in all individuals. Surgeons should be aware of these limits when treating patients with ankle instability.

Correlation between subchondral bone plate thickness and cartilage degeneration in osteoarthritis of the ankle

BACKGROUND

Osteoarthritis (OA) is characterized not only by cartilage degeneration, but also subchondral bone changes. The subchondral bone plate (SBP) plays an important role in cartilage metabolism, and elucidation of the relationship between the SBP and cartilage degeneration would be helpful to determine the most appropriate treatment strategy for ankle OA. The purpose of this study was to evaluate the SBP and to compare it with cartilage degeneration with arthroscopic findings.

METHODS

Computed tomography (CT) was used to compare the thickness of the SBP of 11 ankle OA patients with that of 11 non-ankle OA patients in 9 areas of the talar dome. The French Society of Arthroscopy (SFA) grading system was used to analyze the relationship between findings on the thickness of SBP and on articular cartilage degeneration in ankle OA.

RESULTS

The SBP in ankle OA was significantly thicker than that of the non-OA ankle. The more severe the articular cartilage degeneration, the thicker the SBP became. The SBP on the sclerotic trabecular bone was significantly thicker than that on decreased trabecular bone. The SFA grade for sclerotic subchondral bone was significantly higher than that for decreased trabecular bone.

CONCLUSION

This study shows that the thickness of SBP and the findings of subchondral bone such as decreased trabecular bone and sclerosis in CT are related to the cartilage degeneration of ankle OA, although a small number of patients were analyzed.

LEVEL OF EVIDENCE

Level III, comparative series.