Effects of simulated genu valgum and genu varum on ground reaction forces and subtalar joint function during gait

The mechanical effects of genu valgum and varum deformities on the subtalar joint were investigated. First, a theoretical model of the forces within the foot and lower extremity during relaxed bipedal stance was developed predicting the rotational effect on the subtalar joint due to genu valgum and varum deformities. Second, a kinetic gait study was performed involving 15 subjects who walked with simulated genu valgum and genu varum over a force plate and a plantar pressure mat to determine the changes in the ground reaction force vector within the frontal plane and the changes in the center-of-pressure location on the plantar foot. These results predicted that a genu varum deformity would tend to cause a subtalar pronation moment to increase or a supination moment to decrease during the contact and propulsion phases of walking. With genu valgum, it was determined that during the contact phase a subtalar pronation moment would increase, whereas in the early propulsive phase, a subtalar supination moment would increase or a pronation moment would decrease. However, the current inability to track the spatial position of the subtalar joint axis makes it difficult to determine the absolute direction and magnitudes of the subtalar joint moments.     

Double calcaneal osteotomy: realignment considerations in eight patients

Posterior calcaneal displacement and anterior calcaneal distraction osteotomies have been recommended for surgical management of flexible flatfoot deformity. We combined these procedures for surgical management of adolescent flatfoot and late stage II posterior tibial tendon dysfunction in the adult. Lateral column distraction has been shown to reduce rearfoot valgus and forefoot abduction by stabilizing the midtarsal joint. Posterior calcaneal displacement osteotomy, which results in medial translation of the tuberosity, converts the posterior muscle group from an everter to an inverter. A supinatory moment, therefore, is created about the subtalar joint axis, which results in supination during the midstance phase of gait. These procedures may be considered when calcaneal valgus, forefoot abduction, and midtarsal joint instability are clinically significant. We also include rearfoot alignment radiographs, long leg calcaneal axial radiographs, and malleolar valgus indices to further evaluate alignment of the foot, ankle, and leg. Ideal realignment is achieved when the heel is vertical in resting calcaneal stance position, the forefoot is parallel to the rearfoot in the frontal plane, and the medial column is stabilized, with elimination of forefoot abduction.     

Function of the windlass mechanism in excessively pronated feet

The foot postures of 39 subjects were evaluated for excessive pronation by means of six static weightbearing and five nonweightbearing measurements, and two types of footprint indexes. Visual evidence of windlass function was recorded by video. Chi-square analysis revealed that excessive pronation does not affect the establishment of the windlass mechanism. The position of the forefoot relative to the rearfoot, subtalar joint axis position, and navicular drift/foot length ratio were significantly associated with dynamic windlass function. These results suggest that selected static measurements may have value in predicting some aspects of dynamic foot function during the propulsive phase of the gait cycle.     

Three-dimensional movement of the foot during the stance phase of walking

This study presents research on typical movement of the rearfoot during walking. The data demonstrate the global nature of foot pronation and supination during gait. Study participants (N = 153) walked along a walkway while the angular displacement of the calcaneus, navicular, and first metatarsal relative to the tibia was measured; three-dimensional movement patterns for all three bones were very similar. This study provides additional information on how the foot functions during walking. This information should help to define and refine clinical management strategies for treating foot dysfunction.     

Effects of rearfoot-controlling orthotic treatment on dorsiflexion of the hallux in feet with abnormal subtalar pronation: a preliminary report

The aim of this study was to determine whether the treatment of abnormal subtalar pronation restores functional (as opposed to structural) limited dorsiflexion of the first metatarsophalangeal joint (functional hallux limitus). We studied 16 feet of eight individuals with abnormal subtalar pronation. Orthoses were made for all of the feet, and hallux dorsiflexion was measured during weightbearing. Each patient was unshod without the orthosis, unshod with the orthosis fitted on the same day, and unshod with the orthosis fitted approximately 5 months later. The results suggest that in functional hallux limitus caused by abnormal subtalar pronation, hallux dorsiflexion will gradually be restored by the use of foot orthoses to control the abnormal subtalar pronation.     

Sensitivity and specificity of the functional hallux limitus test to predict foot function

Functional hallux limitus is an underrecognized entity that generally does not produce symptoms but can result in a variety of compensatory mechanisms that can produce symptoms. Clinically, hallux limitus can be determined by assessing the range of motion available at the first metatarsophalangeal joint while the first ray is prevented from plantarflexing. The aim of this study was to determine the sensitivity and specificity of this clinical test to predict abnormal excessive midtarsal joint function during gait. A total of 86 feet were examined for functional hallux limitus and abnormal pronation of the midtarsal joint during late midstance. The test had a sensitivity of 0.72 and a specificity of 0.66, suggesting that clinicians should consider functional hallux limitus when there is late midstance pronation of the midtarsal joint during gait.     

Foot orthoses: a review focusing on kinematics

Orthoses have been broadly used by clinicians to treat mechanical misalignments, such as abnormal foot pronation. As such, the influences of orthoses on lower-limb kinematics have been studied numerous times, with many articles reporting nonsystematic results; the aim of this review, therefore, was to examine the recognized effects of foot orthoses on lower-limb kinematics. The findings from this review suggest that foot orthoses seem to have certain generic and common effects on the lower limb when designed to control rearfoot pronation. We also discuss the possible reasons behind the lack of consistent results between studies. Based on the findings, a list of recommendations is presented for future research on foot orthoses to facilitate comparisons between studies and enable the scientific and clinical communities to better comprehend the effects that these variables might have on the kinematics and, possibly, the treatment outcomes.     

The effect of high-Dye and low-Dye taping on rearfoot motion

High-Dye and low-Dye taping are commonly used by clinicians to treat a variety of foot and ankle pathologies, particularly those associated with excessive rearfoot pronation. While the effects of taping on end range of motion have been extensively studied, relatively little is understood about the effect of the two styles of taping on rearfoot motion. Eighteen participants were analyzed in three conditions: 1) barefoot, 2) with high-Dye taping, and 3) with low-Dye taping. Two-dimensional motion of the rearfoot was assessed for each condition. The results indicated maximum inversion was increased with both high-Dye and low-Dye taping as compared with no taping. Only high-Dye taping, however, significantly reduced the maximum eversion of the rearfoot. The results suggest that high-Dye taping is an appropriate taping choice when control of eversion of the rearfoot is desired.     

Serial measurement of calcaneal pitch during midstance

Although emerging evidence suggests a causal relationship between arch structure and musculoskeletal injury, few investigations have adequately assessed arch function during gait. In this study, digitized videofluoroscopy was used to evaluate the sagittal plane motion of the calcaneus during gait. Nine female subjects requiring diagnostic foot radiographs underwent videofluoroscopy. The calcaneal inclination angle, arch height ratio, and tarsal index were digitally analyzed for all radiographic images. Calcaneal pitch was correlated to both the arch height ratio and the tarsal index. Repeated measures analysis of variance helped to identify a significant reduction in the mean calcaneal pitch during the midstance and early propulsive periods of gait. These findings suggest that although calcaneal pitch may be used as an indicator of rearfoot position, biomechanical classification of foot types based on radiographs may result in erroneous conclusions concerning foot function.     

Changes in plantar foot pressure with in-shoe varus or valgus wedging

Varus and valgus wedging are commonly used by podiatric physicians in therapy with custom-made foot orthoses. This study aimed to provide scientific evidence of the effects on plantar foot pressure of applying in-shoe forefoot or rearfoot wedging. The plantar foot pressure distribution of 23 subjects walking on a treadmill was recorded using a pressure insole system for seven different wedging conditions, ranging from 3 degrees valgus to 6 degrees varus for the forefoot and from 4 degrees valgus to 8 degrees varus for the rearfoot. The results demonstrate that increasing varus wedging magnifies peak pressure and maximal loading rate at the medial forefoot and rearfoot, whereas increasing valgus wedging magnifies peak pressure and maximal loading rate at the lateral forefoot and rearfoot. As expected, the location of the center of pressure shifts medially with varus wedging and laterally with valgus wedging. However, these shifts are less significant than those in peak load and maximal loading rate. Timing variables such as interval from initial impact to peak load do not seem to be affected by forefoot or rearfoot wedging. Finally, rearfoot wedging does not significantly influence pressure variables of the forefoot; similarly, rearfoot pressure remains unaffected by forefoot wedging.     

Evaluating the biomechanics of the pediatric foot in Turner syndrome: a case report

Turner syndrome is a genetic disorder that can present clinically with multiple concurrent comorbidities. This case report describes a 12-year-old girl with Turner syndrome who was referred for podiatric medical assessment and explores the application of optoelectronic stereophotogrammetry in the biomechanical assessment of the foot and lower limb. A four-segment kinematic foot model using 14-mm reflective markers was applied to the foot and lower limb of the patient to track motion at the tibia, rearfoot, forefoot, and hallux. Kinematic results presented in this case study illustrate evidence of excessive foot pronation throughout the stance phase of gait. Whether excessive pronation is a general characteristic of foot function in Turner syndrome remains to be confirmed, but the findings presented suggest that a comprehensive evaluation of foot biomechanics in patients with Turner syndrome may be warranted.     

Biomechanics of the normal and abnormal foot

The foot is an engineering marvel that allows the body to perform many physical activities over a wide variety of terrain with remarkable efficiency. The functions of the foot and the lower extremity are biomechanically integrated; thus normal lower-extremity function requires normal foot function and vice versa. Because the subtalar joint is the main pedal joint allowing the triplanar translation of motion between the foot and lower extremity, normal subtalar joint function is critical to normal foot and lower-extremity function. This article provides an overview of the interrelationships between foot and lower-extremity function and mechanically based pathology of the foot and lower extremity, with an emphasis on the subtalar joint.     

Effects of hallux limitus on plantar foot pressure and foot kinematics during walking

The effects of hallux limitus on plantar foot pressure and foot kinematics have received limited attention in the literature. Therefore, a study was conducted to assess the effects of limited first metatarsophalangeal joint mobility on plantar foot pressure. It was equally important to identify detection criteria based on plantar pressures and metatarsophalangeal joint kinematics, enabling differentiation between subjects affected by hallux limitus and people with normal hallux function. To further our understanding of the relation between midtarsal collapse and hallux limitus, kinematic variables relating to midtarsal pronation were also included in the study. Two populations of 19 subjects each, one with hallux limitus and the other free of functional abnormalities, were asked to walk at their preferred speed while plantar foot pressures were recorded along with three-dimensional foot kinematics. The presence of hallux limitus, structural or functional, caused peak plantar pressure under the hallux to build up significantly more and at a faster rate than under the first metatarsal head. Additional discriminators for hallux limitus were peak dorsiflexion of the first metatarsophalangeal joint, time to this peak value, peak pressure ratios of the first metatarsal head and the more lateral metatarsal heads, and time to maximal pressure under the fourth and fifth metatarsal heads. Finally, in approximately 20% of the subjects, with and without hallux limitus, midtarsal pronation occurred after heel lift, validating the claim that retrograde midtarsal pronation does occur.     

Sagittal plane compensations for artificially induced limitation of the first metatarsophalangeal joint: a preliminary study

This study was undertaken to establish whether reduced dorsiflexion at the first metatarsophalangeal joint affects sagittal plane kinematics at the ankle, knee, and hip. Twenty individuals with symptom-free metatarsophalangeal joints were studied as they walked with and without an insole designed to restrict first metatarsophalangeal joint dorsiflexion. Sagittal plane kinematics at the ankle, knee, and hip were compared in the two conditions. When walking with the insole, the ankle was more dorsiflexed during late midstance and less plantarflexed during propulsion, the knee was more flexed during midstance, and the hip was less extended during late midstance. This evidence of a link between the first metatarsophalangeal joint and the kinematics of the proximal joints demonstrates the potential for the clinical entities of hallux rigidus and hallux limitus to influence gait and justifies more detailed study of this relationship.     

The subtalar joint axis locator: a preliminary report

A new clinical device, the subtalar joint axis locator, was created to track the three-dimensional location of the subtalar joint axis during weightbearing movements of the foot. The assumption was that if the anterior exit point of the subtalar joint axis is stationary relative to the dorsal aspect of the talar neck, then, by performing radiographs of the feet with the subtalar joint axis locator in place on the foot, the ability of the locator to track rotations and translations of the talar neck and thus the subtalar joint axis in space could be approximated. In this preliminary study of two adults, the subtalar joint axis locator accurately tracked the talar neck position during weightbearing rotational motions of the subtalar joint. The device was also used in a series of subjects to determine its dynamic capabilities. It is possible, then, that the subtalar joint axis locator can reliably track the spatial location of the subtalar joint axis during weightbearing movements of the foot.     

Gait analysis with an integrated system for functional assessment of talocalcaneal coalition

There is little knowledge of the functional performance of patients with talocalcaneal coalition because of the marginal quantitative information accessible using current motion-analysis and plantar pressure-measurement techniques. A novel system was developed for comprehensively measuring foot-floor interaction during the stance phase of gait that integrates instrumentation for simultaneously measuring bony segment position, ground reaction force, and plantar pressure with synchronization of spatial and temporal variables. An advanced anatomically based analysis of foot joint rotations was also applied. Tracking of numerous anatomical landmarks allowed accurate selection of three footprint subareas and reliable estimation of relevant local forces and moments. Eight patients (11 feet) with talocalcaneal coalition were analyzed. Major impairment of the rearfoot was found in nonsurgical patients, with an everted attitude, limited plantarflexion, and overloading in all three components of ground reaction force. Surgical patients showed more normal loading patterns in each footprint subarea. This measuring system allowed for accurate inspection of the effects of surgical treatment in the entire foot and at several footprint subareas. Surgical treatment of talocalcaneal coalition seems to be effective in restoring more physiologic subtalar and forefoot motion and loading patterns.     

Relationship between the subtalar joint inclination angle and the location of lower-extremity injuries

This study hypothesized that individuals who have a history of knee pain during repetitive weightbearing activities have a higher subtalar joint inclination angle than those with a history of foot pain. Study participants were selected on the basis of results of a written questionnaire that asked about the site and cause of injury and pain frequency and intensity. Pain items were graded on a 7-point Likert scale. Subjects were mainly young (18 to 32 years of age), healthy university students who had a history of knee pain (knee group) or foot pain (foot group) during weightbearing activity. Both foot and lower-leg kinematic data were used to estimate the magnitude of each participant's subtalar joint inclination angle. These data were obtained while participants performed a series of open- and closed-kinetic-chain motions. The subtalar joint inclination angle was significantly greater for the knee group than for the foot group. The results of this study support the hypothesis that a higher subtalar joint inclination angle may predispose an individual to knee pain, and a lower subtalar joint inclination angle to foot pain.     

距舟关节在体运动与足内侧纵弓变化的相关性

目的通过数字化技术探讨距舟关节的在体运动特点及其对足内侧纵弓变化的影响。方法采集5名健康志愿者(4男1女)9例足部在进行内翻内收背伸运动时初始体位(中立位)和终末体位(最大内翻内收背伸位)的足部CT影像,利用mimics和geomagic逆向工程软件,结合刚体运动学原理,计算出距舟关节在足部这一运动过程中的三维空间6个自由度的变化及其与足内侧纵弓变化之间关系。结果足内翻内收背伸运动时,距舟关节发生了内翻内收跖屈运动,其内翻幅度:(38.82±5.98)°,内收幅度:(19.71±6.33)°,跖屈幅度:(-5.09±6.89)°;距舟关节运动中足舟骨向内侧移位与足内弓顶角变化具有显著相关性(P<0.05)。结论数字化技术解决了距舟关节在体三维运动测量的难题,通过这一技术的测量与分析发现:距舟关节虽然是一个杵臼状关节,但其主要进行绕矢状轴旋转,距舟关节的运动是引起足内侧纵弓变化的主要因素之一。     

Effect of cast and noncast foot orthoses on plantar pressure and force during normal gait

A variety of plantar pressure and force measures were explored in 22 healthy individuals with excessive pronation. The measures were obtained while the subjects wore a thin-soled athletic shoe alone, a modified Root foot orthosis made from a neutral cast, and a flat noncast insole with a 6 degrees varus rearfoot post. The data obtained from subjects wearing the noncast insole differed only minimally from those obtained while they were wearing the shoe only. In contrast, the modified Root orthosis had a profound effect on foot function. Heel forces and pressures were reduced, and the rearfoot contact area was increased. Measures of force in the midfoot demonstrated substantial increases in load in this region, but the increase in area associated with the contoured device resulted in no increase in midfoot pressure measurements. Forefoot pressures were reduced both medially and laterally with the cast device in place.