Normal biomechanics of the foot and ankle

The biomechanics of the foot and ankle are important to the normal function of the lower extremity. The foot is the terminal joint in the lower kinetic chain that opposes external resistance. Proper arthrokinematic movement within the foot and ankle influences the ability of the lower limb to attenuate the forces of weightbearing. It is important for the lower extremity to distribute and dissipate compressive, tensile, shearing, and rotatory forces during the stance phase of gait. Inadequate distribution of these forces could lead to abnormal stress and the eventual breakdown of connective tissue and muscle. The combined effect of muscle, bone, ligaments, and normal foot biomechanics will result in the most efficient force attenuation in the lower limb. This article will look specifically at the normal biomechanics of the foot and ankle. J Orthop Sports Phys They 1985;7(3):91-95.     

Mild-to-Moderate Hallux Valgus Does Not Decrease Ankle Muscle Strength in Middle-Aged Japanese Women: A Comparative Study

Extreme hallux valgus has been documented to be related to lower functional ability and health-related quality of life. It also has a negative effect on foot structure and biomechanical characteristics, which in turn may affect muscle strength in the foot and ankle. Thus, the purposes of this study were to determine whether there is a difference of ankle muscle strength in varied hallux valgus deformities and to investigate correlations between hallux valgus angles and ankle muscle strength. Hallux valgus angles and ankle muscle strength data were collected from 31 middle-aged Japanese women. The hallux valgus angle was measured with a 3-dimensional foot scanner; ankle muscle strength was measured with a dynamometer. Results showed no differences in ankle muscle strength between normal and mild-to-moderate hallux valgus at both 60º/second and 120º/second (p > .05). Unexpectedly, women with mild-to-moderate hallux valgus had a greater value for inversion peak torque per body weight and eversion-to-inversion ratio than those with normal hallux valgus (p = .019 and p = .022) at 120º/second. Furthermore, hallux valgus was correlated with inversion peak torque and peak torque per body weight (r?=?0.47; p = .012 and r?=?0.50; p?=?.007) and associated with eversion-to-inversion strength ratio (r?=?–0.47; p = .012). The findings indicated that mild-to-moderate hallux valgus did not result in a decrease in ankle muscle strength. Conversely, mild-to-moderate hallux valgus had greater ankle inversion strength in middle-aged Japanese women. Further studies are needed to investigate ankle muscle strength in severe hallux valgus deformities.     

Plantar Pressure Distribution in a Hyperpronated Foot before and after Intervention with an Extraosseous Talotarsal Stabilization Device—A Retrospective Study

Plantar pressure measurements have long been used by clinicians to provide information regarding potential impairments and disorders of the foot and ankle. Elevations in peak plantar pressures or a poor distribution of these pressures can be an indication of pathomechanics in the foot. Lower extremity deficits such as sensory impairment, foot deformities, limited joint mobility, and reduced plantar tissue thickness have been associated with high plantar pressures. The total pressures, pressure distribution, and peak pressures provide useful information to evaluate the abnormal functioning of the talotarsal joint. Instability of the talotarsal joint can result in excessive forces exerted on the joints and surrounding tissues in the foot that can then lead to dysfunction of the proximal musculoskeletal kinetic chain. In the present study, we performed a retrograde analysis of the pre- and postoperative measurements of the peak plantar pressures, peak forces, and area of contact between the foot and the ground during each phase of the gait cycle for 6 patients (12 feet) who had undergone a bilateral extraosseous talotarsal stabilization procedure using a type II extraosseous talotarsal stabilization device. After the procedure, a significant reduction was seen in the peak pressures (42%) over the entire foot and a significant increase in the contact area (19.7%) between the foot and the floor. This could imply that the extraosseous talotarsal stabilization procedure was effective in stabilizing the talotarsal joint complex, thus eliminating abnormal hindfoot motion and restoring the normal biomechanics of the foot and ankle complex, as indicated by a reduction and realignment of the peak plantar pressures and forces.     

The Reverse Peroneus Brevis Muscle Flap for Ankle Wound Coverage

Coverage of lower extremity wounds, especially those in the ankle region, presents a challenge to the foot and ankle surgeon. The present case illustrates a surgical technique for the use of the reverse (distally based) peroneus brevis muscle flap for coverage of a postoperative ankle wound with exposed bone. The reverse peroneus brevis muscle flap provides an option for wound coverage in the ankle region in limb salvage cases in medically frail patients.     

What future direction should podiatric biomechanics take?

With researchers from many scientific and medical disciplines currently devoting countless hours trying to solve the mechanical mysteries of the foot, it is important that the proper direction for research be established. The author of this article believes that one of the most important directions in podiatric biomechanics will focus on the development of accurate models of the human foot and lower extremity. Accurate models will be useful because they provide relatively accurate predictions of the magnitudes of loading forces that occur in the structural component of the human foot and lower extremity during weight-bearing activities. From its beginnings in the early 1960s, podiatric biomechanics has developed from a fledgling collection of thoughts and observations from Merton Root and his colleagues to an internationally recognized clinical science with numerous researchers, past and present, contributing to its growing base of knowledge. With an emphasis on accurate modeling of the foot and lower extremity to allow better prediction of the internal forces that create pathologic conditions during weight-bearing activities, podiatric biomechanics will continue to provide valuable insight into many of the painful syndromes that plague children and adults of the world.     

Aplastic Posterior Tibial Artery in the Presence of Trimalleolar Ankle Fracture Dislocation Resulting in Below-the-Knee Amputation

We present an interesting, but unfortunate, case of an 86-year-old female who sustained a trimalleolar ankle fracture dislocation that resulted in below-the-knee amputation after open reduction and internal fixation of the fracture. To the best of our knowledge, this is the first case report describing popliteal variants that ultimately resulted in critical limb ischemia and below-the-knee amputation after foot and ankle trauma. The anatomic variation altered the expected outcome from a relatively straightforward surgical case. We introduce the previously described lower extremity Allen test and describe how it can be a useful adjunct in the initial physical examination of lower extremity trauma. The ability to identify abnormal distal perfusion to the foot could provide enough insight to warrant evaluating the patient with angiography or computed tomography angiography.     

The effect of ankle equinus upon the diabetic foot

The association between ankle equinus and common foot pathologies such as Achilles tendinitis, metatarsalgia, Morton's neuroma, hallux abductovalgus, and plantar fasciitis has been described. However, the association between ankle equinus and diabetic foot pathology has only been recognized recently. Over half of the non-traumatic amputations occurring in the United States are related to complications of diabetes. It is imperative that risk factors for lower extremity ulceration and amputation are identified and addressed. This article reviews the effect of ankle equinus deformity on the diabetic foot and the available treatment options. New data on the prevalence of equinus in a population of patients with diabetes are also presented.     

第一跖骨头下籽骨的解剖及生物力学研究进展

第一跖骨头下籽骨位于足拇短屈肌腱内,是足部最重要的籽骨,对于保持人体正常承重和足部正常生物力学具有重要意义。由于其在外翻的发生中扮演重要角色,是近年来足踝外科研究的热门。其解剖及生物力学等研究是各种临床研究的基础。本文就第一跖骨头下籽骨的解剖及生物力学国内外最新研究进行概述。     

Outcome study of hallux valgus surgery--an AOFAS multi-center study.

Three hundred and eleven patients have been enrolled in a multi-center prospective study evaluating the outcome of hallux valgus surgery by the members of the American Orthopaedic Foot and Ankle Society. One hundred seventy-nine of these patients have completed six-month follow-up questionnaires, and 195 have completed 12-month questionnaires. The AAOS Lower Limb Outcomes Data Collection Questionnaire and the Foot and Ankle Outcomes Data Collection Questionnaire were used to assess patients' perceptions of their results. Both of these instruments are validated lower extremity instruments. They contain the SF-36 instrument as well as questions relating to lower extremity function. At six- and 12-month follow-up, significant improvement has been noted in the patients' SF-36 physical function scores, role physical scores, and bodily pain scores. Role emotional scores were increased at six months but returned to baseline at 12 months. The scores for physical health and pain and satisfaction with symptoms for the lower extremity have significantly improved. The global foot and ankle score and shoe comfort score from the foot and ankle module have also significantly improved. This outcome study is the first to focus on the patient's perception of results of hallux valgus surgery and demonstrates a significant improvement in pain, function, and satisfaction after bunion surgery performed by members of the American Orthopaedic Foot and Ankle Society.     

Relationship between lower limb muscle strength and hallux valgus severity in older people

ObjectiveTo examine differences in lower limb muscle strength between older people with varying degrees of hallux valgus deformity.MethodsMuscle strength was measured at the knee, ankle and foot using hand-held dynamometry and a clinical test of toe strength (the paper grip test) in 157 older people (99 women and 58 men) aged 65 to 91 (mean 74.1, SD 5.9) years. Hallux valgus severity was documented as none, mild, moderate or severe using validated photographs. Differences in muscle strength according to hallux valgus severity were evaluated using analysis of variance, adjusting for age. Paper grip test performance was compared across the hallux valgus severity groups using the chi-square (χ²) statistic.ResultsKnee extension, ankle joint dorsiflexion, ankle joint plantar flexion, ankle joint inversion, ankle joint eversion and lesser toe plantarflexion strength were not significantly different across the four hallux valgus severity groups. However, there was a significant, dose-response reduction in hallux plantarflexion strength with increasing severity of hallux valgus. This persisted after adjustment for age (F₃ = 5.5, p = 0.001) with a medium effect size (partial η² = 0.10). The number of participants who could successfully complete the paper grip test of the hallux significantly reduced across the four hallux valgus categories (χ² = 18.5, p < 0.001).ConclusionsThere is a specific and progressive reduction in hallux plantarflexion strength with increasing severity of hallux valgus in older people. This finding has potential implications for both the aetiology and treatment of this common and disabling condition.     

Muscle performance and ankle joint mobility in long-term patients with diabetes

Background  

Long-term patients with diabetes and peripheral neuropathy show altered foot biomechanics and abnormal foot loading. This study aimed at assessing muscle performance and ankle mobility in such patients under controlled conditions.     

Number of Segments Within Musculoskeletal Foot Models Influences Ankle Kinematics and Strains of Ligaments and Muscles

Multi‐segment foot models (MFMs) are becoming a common tool in musculoskeletal research on the ankle‐foot complex. The purpose of this study was to compare ankle joint kinematics as well as ligament and muscle strains that result from MFM with a different number of segments during vertical hopping. Ten participants were recruited and performed double‐limb vertical hops. Marker positions and ground reaction forces were collected. Two‐segment (2MFM), three‐segment (3MFM), and five‐segment MFM (5MFM) were used to calculate ankle kinematics and the strains of the anterior talofibular and calcaneofibular ligaments and of the soleus and gastrocnemius muscles. Ranges of motion and peak strains were analyzed with Kruskal–Wallis and post hoc tests, whereas the time‐series of the ankle kinematics and ligament and muscle strains were analyzed with statistical parametric mapping. There were significant main effects for MFM in the talocrural joint range of motion and peak strains of ligaments and muscles. In addition, there were significant main effects for MFM in time‐series data of the talocrural joint angle as well as for ligament and muscle strains. In all cases, the post hoc analyses showed that the 2MFM consistently overestimated the range of motion and tissue strains compared to the 3MFM and 5MFM, while 3MFM and 5MFM did not differ from each other in the most variables. This study showed that the number of segments in MFM significantly affects the biomechanical estimates of joint kinematics and tissue strains during hopping. Clinical significance: MFM that combine all foot structures beyond the talus into one segment likely overestimate ankle joint biomechanics. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2231–2240, 2019     

Foot and ankle sensory neuropathy, proprioception, and postural stability

Foot and ankle sensory neuropathy may result from a variety of pathologic conditions, especially diabetes mellitus. Decreased sensation, particularly on the plantar surface of the feet, leads to obvious risks of cutaneous injury. Less obvious are the risks of fall-related injury associated with changes in other sensory systems of the foot and ankle, such as the receptors involved in joint movement and position perception. The results of a number of studies demonstrate that the neuropathic process affects these receptors in individuals with diabetes mellitus. Associated with the decreased sensory function of the foot and ankle is decreased performance on tests of static and dynamic postural stability. Subjective feelings of instability and an increased incidence of fall-related injuries have also been reported. The reduced postural stability in persons with diabetic neuropathy cannot be attributed exclusively to loss of plantar cutaneous sensation; it appears to be the result of a general loss of peripheral sensory receptor function in the lower legs, including that of the muscle spindles. During the evaluation of an individual with foot and ankle sensory neuropathy, the possibility of balance deficits should be given proper attention. Assessment of balance deficits could be particularly important when planning the course of rehabilitation for individuals with foot and ankle neuropathy who use modified footwear or have an amputation of a section of the foot or lower extremity.     

Feet injuries in rock climbers

While injuries of the upper extremity are widely discussed in rock climbers, reports about the lower extremity are rare. Nevertheless almost 50 percent of acute injuries involve the leg and feet. Acute injuries are either caused by ground falls or rock hit trauma during a fall. Most frequently strains, contusions and fractures of the calcaneus and talus. More rare injuries, as e.g., osteochondral lesions of the talus demand a highly specialized care and case presentations with combined iliac crest graft and matrix associated autologous chondrocyte transplantation are given in this review. The chronic use of tight climbing shoes leads to overstrain injuries also. As the tight fit of the shoes changes the biomechanics of the foot an increased stress load is applied to the fore-foot. Thus chronic conditions as subungual hematoma, callosity and pain resolve. Also a high incidence of hallux valgus and hallux rigidus is described.     

Biomechanics of the ankle joint. A perspective on total ankle replacement

The biomechanics of the ankle present a unique set of challenges for arthroplasty surgery. Its biomechanics are not simple. Although the ankle joint may seem like a hinge, it is not in a line perpendicular to the tibia. The axis of rotation does not stay constant during range of motion, despite a relative congruency of this joint. Allowing for rotational forces must be accomplished, while maintaining the stability of the joint and its components. Success of the arthroplasty depends on how successful designs can dissipate these rotational forces, while maintaining the stability of the joint. It is not yet clear from the biomechanical analysis of the normal ankle joint that this dissipation of forces has been accomplished successfully in modern implants, although early results in the semiconstrained designs are encouraging. Careful assessment of long-term follow-up will determine how close the present designs are to mimicking the unique requirements of the arthritic foot and ankle. Further work on the biomechanics of these replacements would be beneficial.     

Bacterial skin contamination after surgical preparation in foot and ankle surgery

An effective presurgical preparation is an important step in limiting surgical wound contamination and preventing infection. The purpose of this study was to evaluate residual bacterial skin contamination after surgical skin preparation in foot and ankle surgery to determine if current techniques are satisfactory in eliminating harmful pathogens. Fifty consecutive patients having surgical procedures of the foot and ankle were studied. Each lower extremity was prepared randomly with either a one-step povidone-iodine topical gel or a two-step iodophor scrub followed by a povidone-iodine paint. After preparation and draping, cultures were obtained at three locations: the hallux nailfold, web space between the second and third, and fourth and fifth toes, and the anterior ankle (control). In the gel group, positive cultures were obtained from 76% of halluces, 68% of toes, and 16% of controls. In the scrub and paint group, positive cultures were obtained from 84% of halluces, 76% of toes, and 28% of controls. Numerous pathogens were cultured, with Staphylococcus epidermidis being the most prevalent. Based on the findings of the current study, presurgical skin preparation with a povidone-iodine based topical bactericidal agent is not sufficient in eliminating pathogens in foot and ankle surgery. The unique environment of the foot and its resident organisms may play a role in the higher infection rates associated with surgery of the foot and ankle.     

人体足踝部有限元模型的建立及有效性分析

背景：传统的足踝部生物力学研究有其局限性,本文介绍一种足踝部有限元建模方法,使其具有高度的几何相似及物理相似。目的：探讨建立足踝部有限元模型的方法,为生物力学研究提供数字化仿真平台。方法：通过CT扫描1名男性志愿者踝关节获取足踝部影像学资料,将其输入Mimics软件重建骨骼和韧带,通过Geo—magic处理并生成关节软骨后导入Ansys的Workbench模块,建立足踝部有限元模型,参考相关文献确定材料属性,划分网格,设置边界条件,模拟踝关节正常站立状态下受力,进行加载分析。结果：本研究建立了一个包含骨、软骨及韧带的足踝部有限元模型,相对客观地反映了人体足踝部的基本解剖结构和力学特性。模拟人体站立状态垂直加载600N载荷于胫、腓骨下端的上截面,踝关节胫骨下关节面的接触应力主要分布在中部及前外侧,最大接触应力为3．74MPa,接触面积为335．5mm2。踝关节周围四条主要韧带的位移（拉伸长度）中：胫跟韧带〉胫舟韧带〉跟腓韧带〉下胫腓联合前韧带。结论：本研究所建立的人体足踝部有限元模型经验证结果可靠,可进一步用于足踝部生物力学研究。     

Biomechanical basis of foot orthotic prescription

Foot orthoses are prescribed to improve posture in the foot and ankle. The decade of the 1980s witnessed the widespread use of foot orthoses in an attempt to produce relief of a variety of symptoms in the foot and leg and pathologies due to hindfoot and/or forefoot malalignments. While it is documented that many overuse injuries of the lower limb can be relieved with the use of foot orthoses, it remains unclear how an orthosis can produce this effect. The following review examines the use of foot orthoses in various foot pathologies and their relationship to the biomechanics of the foot.     

Efficacy of surgical preparation solutions in foot and ankle surgery

BACKGROUND: Previous studies have demonstrated higher infection rates following orthopaedic procedures on the foot and ankle as compared with procedures involving other areas of the body. Previous studies also have documented the difficulty of eliminating bacteria from the forefoot prior to surgery. The purpose of the present study was to evaluate the efficacy of three different surgical skin-preparation solutions in eliminating potential bacterial pathogens from the foot. METHODS: A prospective study was undertaken to evaluate 125 consecutive patients undergoing surgery of the foot and ankle. Each lower extremity was prepared with one of three randomly selected solutions: DuraPrep (0.7% iodine and 74% isopropyl alcohol), Techni-Care (3.0% chloroxylenol), or ChloraPrep (2% chlorhexidine gluconate and 70% isopropyl alcohol). After preparation, quantitative culture specimens were obtained from three locations: the hallux nailfold (the hallux site), the web spaces between the second and third and between the fourth and fifth digits (the toe site), and the anterior part of the tibia (the control site). RESULTS: In the Techni-Care group, bacteria grew on culture of specimens obtained from 95% of the hallux sites, 98% of the toe sites, and 35% of the control sites. In the DuraPrep group, bacteria grew on culture of specimens obtained from 65% of the hallux sites, 45% of the toe sites, and 23% of the control sites. In the ChloraPrep group, bacteria grew on culture of specimens from 30% of the hallux sites, 23% of the toe sites, and 10% of the control sites. ChloraPrep was the most effective agent for eliminating bacteria from the halluces and the toes (p < 0.0001). CONCLUSIONS: The use of effective preoperative preparation solution is an important step in limiting surgical wound contamination and preventing infection, particularly in foot and ankle surgery. Of the three solutions tested in the present study, the combination of chlorhexidine and alcohol (ChloraPrep) was most effective for eliminating bacteria from the forefoot prior to surgery.     

Surgical management of Charcot midfoot deformities

Diagnosing Charcot neuroarthropathy requires a heightened index of suspicion. Early recognition and intervention can limit deformity. Aggressive conservative management should be initiated early in the treatment plan to minimize the devastating effects often seen with this condition. Any delay in therapy can result in severe foot and ankle deformity in which traditional nonoperative methods alone may be inadequate. These deformities may lead to ulcerations and ultimately progress to amputation of the lower extremity. Surgical correction and stabilization is an effective method to prevent further deformity and ulcer recurrence. If performed in the appropriate setting and for the right indications, Charcot foot reconstruction is a better alternative to lower limb amputation.