New anatomical reference systems for the bones of the foot and ankle complex: definitions and exploitation on clinical conditions

Background A complete definition of anatomical reference systems (ARS) for all bones of the foot and ankle complex is lacking. Using a morphological approach, we propose new ARS for these bones with the aim of being highly repeatable, consistent among individuals, clinically interpretable, and also suited for a sound kinematic description. Methods Three specimens from healthy donors and three patients with flat feet were scanned in weight-bearing CT. The foot bones were segmented and ARS defined according to the proposed approach. To assess repeatability, intra class coefficients (ICC) were computed both intra- and inter-operator. Consistency was evaluated as the mean of the standard deviations of the ARS position and orientation, both within normal and flat feet. Clinical interpretability was evaluated by providing a quantification of the curvature variation in the medial-longitudinal and transverse arches and computing the Djiann-Annonier angle for normal and flat feet from these new ARS axes. To test the capability to also provide a sound description of the foot kinematics, the alignment between mean helical axes (MHA) and ARS axes was quantified. Results ICC was 0.99 both inter- and intra-operator. Rotational consistency was 4.7 ± 3.5 ° and 6.2 ± 4.4° for the normal and flat feet, respectively; translational consistency was 4.4 ± 4.0 mm and 5.4 ± 2.9 mm for the normal and flat feet, respectively. In both these cases, the consistency was better than what was achieved by using principal axes of inertia. Curvature variation in the arches were well described and the measurements of the Djiann-Annoier angles from both normal and flat feet matched corresponding clinical observations. The angle between tibio-talar MHA and ARS mediolateral axis in the talus was 12.3 ± 6.0, while the angle between talo-calcaneal MHA and ARS anteroposterior axis in the calcaneus was 17.2 ± 5.6, suggesting good capability to represent joint kinematics. Conclusions The proposed ARS definitions are robust and provide a solid base for the 3-dimensional description of posture and motion of the foot and ankle complex from medical imaging.

Novel Design of a Rotation Centre Auto-Matched Ankle Rehabilitation Exoskeleton with Decoupled Control Capacity

This paper presents a novel ankle rehabilitation exoskeleton for post-stroke patients, with its rotational centre automatically conforming with ankle complex once people wear it. This exoskeleton has 2 rotation DOFs and is able to provide 2 different rotation patterns by reconfiguring. In the combined-rotation pattern arrangement, the mechanism can generate all three kinds of rotations that the ankle complex is naturally capable of realising. Among these rotational motions, adduction/abduction rotation is coupled motion. This rotation can be further reduced, or eliminated, by minimizing the distance between the lower connection points of the actuated links and the human ankle complex, and vice versa. For the other rotation pattern, a 90-degree arrangement of the side link offers decoupled motion control of the mechanism. Numerical studies reveal that the required rehabilitation workspace for dynamical gait exercises can be achieved with high dexterity, without generating singularities. Further investigations indicate that this mechanism has great potential for rehabilitating post-stroke patients of a wide range of heights and weights.

Isolated Talonavicular Arthrodesis for Traumatic Talonavicular Arthritis: Report of 2 Cases With Gait Analyses

Isolated talonavicular arthrodesis is one of the surgical procedures for patients with talonavicular arthritis. However, the 3-dimensional kinematic behavior of the hip, knee, and foot/ankle complex during walking after the arthrodesis remains unclear. The clinical outcomes and gait analyses of 2 cases who underwent isolated arthrodesis for talonavicular osteoarthritis with chronic dislocated navicular fracture are presented. Gait analysis was carried out in both cases 1 year after surgery to clarify the side-to-side differences in the ranges of motion of the hip, knee, and foot/ankle complex during walking. Both cases showed good clinical results and radiographic bone union. The kinematic data of the gait analyses showed considerable restriction in the range of motion of the ankle in all 3-dimensional planes for the fused foot compared with the contralateral side. Additionally, hyperextension of the knee in the late stance of gait on the operated side was observed in both cases. When talonavicular arthrodesis was performed for talonavicular osteoarthritis with chronic dislocated navicular fracture, postoperative generalized stiffness of the ankle and future disorder of the knee should be considered. Levels of Evidence: Level V: Case report

Ankle complex musculature adaptations after Energy Drinks consumption in healthy young adult

Over the past few years, energy drink consumption has increased among students aged 18–34 years. Energy drinks alter the balance, reduce blood flow and interfere with neuromuscular activation in the lower extremities. We attempted to determine which specific additive of three different drinks (red bull, rockstar, and bang) could contribute to changes in muscle activation of the ankle complex. Twenty healthy young adults aged 22–28 years were included in this study and allocated among 3 groups, red bull, rockstar, and bang. Neuromuscular data were obtained from EMG sensors positioned on the anterior tibialis and gastrocnemius before completing the four balance tasks. Each participant completed all the tasks before and after the 16-ounce Edrink. ANOVA was performed to compare the data before and after the beverage. Statistical significance was set at P <0.05. A trend was observed in red bull and bang groups revealing a faster anterior tibial activity and prolong activation for gastrocnemius. The rockstar group also showed a more rapid activation trend and shorter response during all tasks for the gastrocnemius. It appears that the additives found in Redbull and Bang produce an increased posterior sway, indicated by the faster activity observed on the anterior tibial muscle. On the other hand, the elements encountered in rockstars provoke anterior movements, creating the need for a quicker response from the gastrocnemius muscle. Further research is required to explore certain energy drink ingredients' effects on dynamic activities such as walking.

In Silico Finite Element Analysis of the Foot Ankle Complex Biomechanics: A Literature Review

Computational approaches, especially Finite Element Analysis (FEA), have been rapidly growing in both academia and industry during the last few decades. FEA serves as a powerful and efficient approach for simulating real-life experiments, including industrial product development, machine design, and biomedical research, particularly in biomechanics and biomaterials. Accordingly, FEA has been a "go-to" high biofidelic software tool to simulate and quantify the biomechanics of the foot-ankle complex, as well as to predict the risk of foot and ankle injuries, which are one of the most common musculoskeletal injuries among physically active individuals. This paper provides a review of the in silico FEA of the foot-ankle complex. First, a brief history of computational modeling methods and Finite Element (FE) simulations for foot-ankle models is introduced. Second, a general approach to build a FE foot and ankle model is presented, including a detailed procedure to accurately construct, calibrate, verify, and validate a FE model in its appropriate simulation environment. Third, current applications, as well as future improvements of the foot and ankle FE models, especially in the biomedical field, are discussed. Lastly, a conclusion is made on the efficiency and development of FEA as a computational approach in investigating the biomechanics of the foot-ankle complex. Overall, this review integrates insightful information for biomedical engineers, medical professionals, and researchers to conduct more accurate research on the foot-ankle FE models in the future.

Design of a Prosthetic Ankle Complex

Nature has, over a large span of geological time, engineered near perfect solutions to most problems humans face today. Motion of the limbs is one such area, and the cutting edge in the development of effective prostheses is biomimetics. Limb prostheses have been used by mankind for the better part of known history, and most of the technology currently available in prosthetics is not exclusively new. However, modern prosthetics either are uncomfortable—and the lack of flexion affects the gait of the patient—or too expensive for a large segment of the populace. This chapter seeks to study the mimicry of physiological systems through the design for an ankle prosthesis that includes a passive damper and mimics the shape and behavior of the natural ankle joint.

Limited intrarater and interrater reliability of acute ligamentous ankle injuries on 3 T MRI

ObjectivesTo determine the diagnostic reliability of the Schneck grading system for acute ligamentous injuries of (1) the three major ligamentous ankle complexes, (2) the individual ankle ligaments and (3) the Sikka classification for syndesmosis injury.MethodsAll acute ankle injuries in adult athletes (≥18 years), presenting to the outpatient department of a specialised Orthopaedic and Sports Medicine Hospital, within 7 days postinjury were screened for inclusion. Ankle injuries were excluded if imaging demonstrated a frank ankle fracture or if the 3 T MRI study could not be acquired within 10 days postinjury. Two radiologists graded the three major ligamentous complexes (lateral ankle complex, deltoid complex and syndesmosis complex) and their comprising individual ligaments according the four-grade Schneck grading system. Syndesmotic injuries were classified according the four-grade Sikka classification for consequent injury of the individual syndesmosis ligaments and the deltoid complex. Agreement and kappa (K) statistics were calculated to determine intrarater and interrater reliability.ResultsBetween September 2016 and September 2018, a total of 92 MR scans were obtained (87 patients). Interrater and intrarater reliability of the Schneck grading system was moderate to substantial for the lateral ankle complex (K=0.47–0.76), fair to almost perfect for the syndesmosis complex (K=0.37–0.89) and fair to moderate for the deltoid complex (K=0.14–0.51). For the individual ligaments, kappa values ranged from moderate to substantial for the anterior talofibular ligament (ATFL) (K=0.55–0.73), fair to substantial for the calcaneofibular ligament (K=0.31–0.62) and fair to almost perfect for the anteroinferior tibiofibular ligament (AITFL) (K=0.36–0.89). Diagnostic reliability of the Sikka classification ranged from moderate to almost perfect (K=0.51–0.95).ConclusionsGrading of the three major ligamentous complexes and of the individual ankle ligaments according the Schneck grading system resulted in limited diagnostic reliability. When dichotomised for the presence of complete discontinuity, the interrater reliability of the Schneck grading system improved to substantial and almost perfect for the ATFL and AITFL, respectively. Classification of syndesmosis injury according the Sikka classification resulted in moderate interrater reliability.

The Flexor Retinaculum Connects the Surrounding Structures into the Medial Ankle Complex

This study aimed to prove the hypothesis that the medial structures of the ankle are interconnected through the flexor retinaculum’s projections. We conducted a retrospective re-evaluation of 132 MRI examinations of the ankle joint from 57 females and 75 males with an age range of 18–65 and a mean age of 35 years. The correlation between the presence of connections between the flexor retinaculum and the deltoid ligament, the spring ligament, the inferior extensor retinaculum, the paratenon, the fibulotalocalcaneal ligament, the fascia covering the abductor hallucis, and the flexor fibrous sheath were studied. The most common connections of the flexor retinaculum were to the deltoid ligament (97%), the fibulotalocalcaneal ligament (84.1%), and the flexor fibrous sheath (83.3%). Interconnection between the flexor retinaculum and the deltoid ligament correlated with the presence of connections between the flexor retinaculum and the inferior extensor retinaculum, the paratenon, and the spring ligament. Side difference was noticed in connections to the flexor fibrous sheath, the deltoid ligament, the fascia on the abductor hallucis, and the paratenon (p < 0.05). The flexor retinaculum formed a more complex anatomical unit with adjacent structures.