Forefoot Joints Research Articles

Effects of different step lengths at a preferred walking speed on forefoot, midfoot, and hindfoot motion in healthy young adults

Hindfoot, midfoot, and forefoot motion during the stance phase of walking provide insights into the forward progression of the body over the feet via the rocker mechanisms. These segmental motions are affected by walking speed. Increases in walking speed are accomplished by increasing step length and cadence. It is unknown if taking short, medium, and long steps at the same speed would increase hindfoot, midfoot, and forefoot motion similarly to walking speed. We examined effects of different step lengths at the same preferred walking speed on peak forefoot, midfoot, and hindfoot motions related to the foot rockers. Twelve young healthy adults completed five walking trials under three step length conditions in a random order as feet and lower extremity motion were measured via marker positions for the combined Oxford foot and conventional gait models. Peak hindfoot, midfoot, and forefoot joint angles indicating heel, ankle, and forefoot rockers were identified. When walking at the same preferred speed with increase in step length, there were increases in peak hindfoot-tibia plantarflexion angle (p < 0.001; ηp2 = 0.76) in early stance associated with the heel rocker and peak hindfoot-tibia dorsiflexion angle (p = 0.016; ηp2 = 0.39) in midstance associated with ankle rocker. In late stance, the peak hindfoot-tibia plantarflexion angle, forefoot-hindfoot angle, and forefoot-hallux dorsiflexion angle indicating forefoot rocker motion also increased with step length (p < 0.01). When foot kinematics are compared across different individuals or the same individual across different sessions, researchers and clinicians should consider the influence of step length as a contributor to differences in foot kinematics observed.

Acute Charcot neuropathy: A devastating consequence of diabetes mellitus

Abstract Introduction Acute Charcot neuropathy (ACN) is a complication of diabetes mellitus. The prevalence of ACN may be up to 13% in diabetic individuals. ACN has a complex etiology. Although it mostly affects middle of the foot, hind-foot joints, the ankle, and forefoot joints; upper limp may also be affected. Here, we present a case with ACN, whose diagnosis was hard to differentiate and manage. Clinical Case A fifty-nine-year-old female admitted to our emergency department with a complaint of pain, numbness, swelling, edema and erythema on left arm. When questioned, she had a history of type 2 diabetes for 22 years and had impaired glycemic regulation with 12.2% HbA1c level. She had all macro and micro vasculary complications of diabetes. On physical examination, her left arm was swollen, pulses were not palpabl. With a suspicion of acute thromboembolism, doppler ultrasound was performed and USG showed no arterial occlusion, but thrombosis from the basilic vein to the proximal brachial vein was seen. She initiated anticoagulant therapy with heparin. After 2 weeks, her complaints increased and pallor, coldness, and pain with passive movements on the left arm were added. She admitted to our intensive care unit with a diagnosis of compartment syndrome. She was followed in ICU with stable hemodynamics and without oxygen supplementation. She had transient acute kidney injury due to rhabdomyolysis but resolved without hemodialysis. Despite fasciotomy, myonecrosis developed on left arm and transhumeral resection was performed. After this devastating result, the patient transferred to endocrinology clinic. Intensive insulin therapy and appropriate antibiotic treatment were continued. During her stay in our clinic, she had the same complaints and physical examination findings on her left foot. Imaging studies (X-ray, bone scintigraphy) showed no osteomyelitis but acute charcot arthropathy was seen. Her glucose levels were regulated, and antibiotics completed. The physical strengthening and ROM exercises for lower extremity and oral total calorie intake was adjusted. Her HbA1c level was decreased to 6.2% without hypoglycemia and she is stable on follow-up. Conclusion ACN is a devastating complication of diabetic neuropathy with its consequences. The diagnosis may mislead clinicians to cellulitis, acute venous thrombosis, arthritis or gout. Misdiagnosis or delay in diagnosis may result in serious consequences such as infection, ulceration even amputation as in our case. A multidisciplinary approach and close monitoring of the findings may provide huge benefit for the patient.

Influence of Arch-Support Orthoses with Heel Lift Manipulation on Joint Moments and Forefoot Mechanics in Running

While foot orthosis is suggested to improve rearfoot motion in running, little information is known about forefoot biomechanics. The objective of this study was to examine the effects of arch-support orthoses with various heel lift manipulation on the loading rate, spatiotemporal, and forefoot joint mechanics using a skin marker set model. Fifteen male habitual rearfoot strikers ran at their selected speeds on an instrumented treadmill in four foot orthoses conditions: flat-control, D2 (2 mm heel lift, arch-support), D6 (6 mm heel lift, arch-support), and D10 (10 mm heel lift, arch-support). A repeated measures ANOVA was performed to examine any significant difference in each of the tested variables, with α = 0.05. Wearing D10 led to smaller maximum loading rate than D2 (p &lt; 0.001) and control (p = 0.002). For sagittal plane, D10 had larger rearfoot touchdown dorsiflexion than D2 (p = 0.027) and control (p = 0.007) and larger in D6 than control (p = 0.025). For frontal plane, wearing D10 demonstrated larger rearfoot frontal RoM than D2 (p = 0.018) and peak forefoot eversion than D6 (p = 0.047) and control (p = 0.048). Furthermore, the forefoot frontal range of motion was lowest when wearing D6. For joint moment, wearing control orthosis exhibited larger peak rearfoot eversion moment than D6 (p = 0.035), but smaller peak knee extension moment than D2 (p = 0.025) and D10 (p = 0.010). These findings indicate that the use of arch-support orthoses would alter the running mechanics that are related to injury potential. Lower heel lift orthoses led to alternations to most of the biomechanical variables than higher heel lift orthoses. Further longitudinal study seems necessary to optimize arch-support orthoses design in running.

Sonographic comparison of transcutaneous stimulation versus percutaneus stimulation of the tibialis anterior: a pilot study

Abstract Background and Aims Previous studies have evaluated electrostimulation of the tibialis anterior muscle via ultrasound. However, to the best of our knowledge, to date, no study has compared percutaneous stimulation compared to transcutaneous stimulation. The aim of this study was to analyze and compare the influence of percutaneous stimulation versus transcutaneous stimulation on the angle and muscle width of the proximal motor point of the tibialis anterior among healthy individuals using ultrasound. Material and Methods A longitudinal prospective study. The study variables were muscle thickness and pennation angle, measured using ultrasound. A sample of 4 healthy individuals with a mean age of 35.25 years ( ± 2.17), mean height of 1.70m ( ± 0.03) and weight of 67.35kg ( ± 6.32), participated in this study. Stimulation was performed on the tibialis anterior of the dominant leg of each individual (n = 4). The subjects were seated in a vertical position. For position 1, the knee of the dominant leg remained completely extended and the ankle was fixed in a neutral position with an orthosis comprised of Velcro straps which immobilized the ankle and forefoot joints. For position 2, the knee remained flexed 90 degrees with the foot fixed in the orthosis and supported on the floor. The proximal motor point of the tibialis anterior muscle was located. A biphasic symmetric pulse current was used with the maximum tolerated intensity. Transcutaneous stimulation was performed via a small circular electrode, and for percutaneous stimulation a filiform acupuncture needle was used. To capture the ultrasound images, the probe was placed on a system with an articulated mechanical arm and a clamp that enabled the possibility of adjusting the height and/or angle and the position marked on the skin. Normality was contrasted using the Shapiro-Wilk test and sphericity was tested using the Mauchly's test. Analysis of variance was performed (ANOVA) for repeated measures. Results The comparison of both techniques in position 1 did not show significant differences between the transcutaneous technique versus the percutaneous technique neither for the angle (F = 2.07; p-valor = 0.18), nor for the width (F =0.28; p-value = 0.60). In the case of position 2, significant differences were not found between the transcutaneous technique versus the percutaneous technique, neither for the angle (F = 0.28; p-value = 0.606) nor for the weight (F =0.11; p-value = 0.75). Conclusions The comparison of transcutaneous stimulation versus percutaneous stimulation in the proximal motor point of the tibialis anterior does not seem to show statistically significant differences for muscle width nor pennation angle.

Cartilage Stiffness Effect on Foot Biomechanics of Chinese Bound Foot: A Finite Element Analysis.

The purpose of this study is to investigate the effect of cartilage stiffness on inner foot biomechanics of Chinese bound foot while balanced standing using finite element method. A three-dimensional FE model of bound foot involving 28 bones, 72 ligaments, 5 plantar fascia, cartilages, and encapsulated soft tissue was constructed and validated. To conduct the sensitivity analysis of cartilage stiffness, the incremental Young’s modulus of 1, 5, 10, and 15 MPa were assigned to the cartilage. 25% of the body weight was applied to the Achilles tendon to adjust the anterior- posterior displacement of center of pressure agreeable with the measured result. As the Young’s modulus of cartilage increased, the peak von Mises stress in the fifth metatarsal increased obviously, while that in the calcaneus remains unchanged. The plantar fascia experienced reduced total tension with stiffer cartilage. The cartilage stiffening also caused a general increase of contact pressure at mid- and forefoot joints. Cartilage stiffening due to foot binding gave rise to risks of foot pain and longitude arch damage. Knowledge of this study contributes to the understanding of bound foot biomechanical behavior and demonstrating the mechanism of long-term injury and function damage in terms of weight-bearing due to foot binding.

Correlation between three-dimensional medial longitudinal arch joint complex mobility and medial arch angle in stage II posterior tibial tendon dysfunction

The purpose of this study was to evaluate correlation between three-dimensional medial longitudinal arch joint complex mobility and medial arch angle in stage II posterior tibial tendon dysfunction flatfoot under loading. CT scans of 15 healthy feet and 15 feet with stage II posterior tibial tendon dysfunction flatfoot were taken both in non- and simulated weight-bearing condition. The CT images of the hindfoot and medial longitudinal arch bones were reconstructed into three-dimensional models with Mimics and Geomagic reverse engineering software. The three-dimensional complex mobility of each joint in the medial longitudinal arch and their correlation with the medial arch angle change were calculated. From non- to simulated weight-bearing condition, the medial arch angle change and the medial longitudinal arch joints mobility were significant larger in stage II posterior tibial tendon dysfunction flatfoot (p<0.05). The eversion of the talocalcaneal joint, the proximal translation of the calcaneus relative to the talus, the dorsiflexion of the talonavicular joint, the dorsiflexion and abduction of the medial cuneonavicular joint, and the lateral translation of the medial cuneiform relative to the navicular, and the dorsiflexion of the first tarsometatarsal joint were all significantly correlated to the medial arch angle change in stage II posterior tibial tendon dysfunction flatfoot (all r>0.5, p<0.05). There is increased mobility in the medial longitudinal arch joints in stage II posterior tibial tendon dysfunction flatfoot and the medial arch angle change under loading causes displacement not only at hindfoot joints but also involve midfoot and forefoot joint.

Custom 3D-printed Total Talar Prostheses Restore Normal Joint Anatomy Throughout the Hindfoot

Category: Hindfoot Introduction/Purpose: Third generation total talar prostheses (TTP) are viable options for talar avascular necrosis (AVN) in the absence of neighboring joint pathology. The use of modern three-dimensional (3D) printing allows for the production of custom implants that exactly mimic the patient’s anatomy. The aim of this study is to determine the accuracy of 3D printing in reproducing a synthetic talus, and in doing so, restoring more normal anatomic relationships. We hypothesize that this mode of replication will restore and maintain normal radiographic alignment of the ankle, subtalar, and forefoot joints in the setting of talar AVN. Methods: A retrospective analysis was performed on all patients undergoing TTP implantation for the treatment of talar AVN between 2016 and 2017. Pertinent demographic and operative factors were recorded. Radiographic measurements were taken pre- and post-operatively to determine native talar dimensions, TTP implant dimensions, and the corresponding radiographic alignment about the forefoot, hindfoot, and ankle. Results: Fourteen patients, treated for AVN between 2016-2017, were identified in our cohort. Talar arc length and width were not found to be significantly changed, however talar height was significantly increased with use of TTP. Five alignment dimensions were measured (tibiotalar alignment, talar tilt angle, Boehler’s angle, talar declination angle, and Meary’s Angle), of which, only talar tilt angle was significantly changed. Instances of Meary’s angle correction were observed in cavus and planus foot deformity. Conclusion: This study represents the largest case series of TTP performed in the United States, and is the first to investigate the 3D printed TTP. As a proof-of-concept, 3D printed TTP was successful in restoring talar height and talar tilt in the setting of AVN. Additionally, the procedure maintained normal alignment in non-pathologic joints. Total talar prosthesis, based on our cohort, is a viable option to restore more normal anatomic alignment.

Custom 3D-Printed Total Talar Prostheses Restore Normal Joint Anatomy Throughout the Hindfoot.

Third generation total talar prostheses (TTPs) are viable options for talar avascular necrosis (AVN) in the absence of neighboring joint pathology. The use of modern three-dimensional (3D) printing allows the production of custom implants that exactly mimic the patient's anatomy. The aim of this study is to determine the accuracy of 3D printing in reproducing a synthetic talus and, in doing so, restoring more normal anatomical relationships. We hypothesize that this mode of replication will restore and maintain normal radiographic alignment of the ankle, subtalar, and forefoot joints in the setting of talar AVN. A retrospective analysis was performed on all patients undergoing TTP implantation for the treatment of talar AVN between 2016 and 2017. Radiographic measurements were taken preoperatively and postoperatively to determine native talar dimensions, TTP implant dimensions, and the corresponding radiographic alignment about the forefoot, hindfoot, and ankle. A total of 14 patients were identified in our cohort. Talar arc length and width were not found to be significantly changed; however, talar height was significantly increased with use of TTP. Five alignment dimensions were measured, of which, only talar tilt angle was significantly changed. Instances of Meary's angle correction were observed in cavus and planus foot deformity. As a proof of concept, 3D-printed TTP was successful in restoring talar height and talar tilt in the setting of AVN. Additionally, the procedure maintained normal alignment in nonpathological joints. TTPs, based on our cohort, are a viable option to restore more normal anatomical alignment. Level IV: Case series.

A pilot investigation of the prevalence of US-detectable forefoot joint pathology and reported foot-related disability in participants with systemic lupus erythematosus.

BackgroundThe main aim of this study was to determine the prevalence of US-detectable forefoot bursae, metatarsophalangeal (MTP) joint and metacarpophalangeal (MCP) joint synovial hypertrophy (SH), Power Doppler (PD) signal or erosion in participants with systemic lupus erythematosus (SLE). A secondary aim was to determine the strength of potential association between patient reported foot-related disability and US-detected forefoot bursae, MTP joint SH, PD signal or erosion in participants with SLE.MethodA cross-sectional observational study of 20 participants with SLE was completed to determine the prevalence of US-detected forefoot bursal, MTP and MCP joint pathology. Patient-reported foot-related impairment and activity limitation (accumulatively referred to as disability) were also recorded. Spearmans’ Rank Correlation analyses were completed to determine the potential strength of association between US-detected pathology and patient report disability.ResultsThe prevalence of MTP joint SH and PD was 80 % (16/20) and 10 % (2/20), respectively. The prevalence of MCP joint SH and PD was 60 % (12/20) and 30 % (6/20) respectively. A significant association was noted between PD scores for the MTP joints and MCP joints (r = 0.556; p = 0.011) although this was not demonstrated for SH scores (r = 0.176; p = 0.459). Significant associations between forefoot bursal prevalence and MTP joint PD were noted (r = 0.467; p = 0.038). The prevalence of bursae and bursal PD (grade 2 or above) was 100 % (20/20) and 10 % (2/20), respectively. Moderate foot-related impairment and activity limitation was reported by 95 and 85 % of participants respectively.ConclusionThis pilot study suggests that US-detected MTP, MCP joint and forefoot bursal abnormalities may be prevalent in participants with SLE and they may experience a moderate level of foot-related disability. Further research is required to substantiate these preliminary findings.

Muscle and Joint Factors Associated With Forefoot Deformity in the Diabetic Neuropathic Foot.

Diabetic forefoot joint deformities are a known risk factor for skin breakdown and amputation, but the causes of deformity are not well understood. The purposes of this study were to determine the effects of intrinsic foot muscle deterioration and limited ankle joint mobility on the severity of metatarsophalangeal joint (MTPJ) deformity, and determine the relationships between these potential contributing factors and indicators of diabetic complications (peripheral neuropathy and advanced glycation end products). A total of 34 participants with diabetic neuropathy (average age, 59 years; range 41-73) were studied. MTPJ angle and intrinsic foot muscle deterioration were measured with computed tomography and magnetic resonance imaging, respectively. Maximum ankle dorsiflexion was measured using kinematics. Skin intrinsic fluorescence served as a proxy measure for advanced glycation end product accumulation. Total forefoot lean muscle volume (r = -0.52, P < .01) and maximum ankle dorsiflexion (r = -0.42, P < .05) were correlated with severity of MTPJ deformity. Together they explained 35% of the variance of MTPJ angle. Neuropathy was correlated with forefoot muscle deterioration (ρ = 0.53, P < .01). Skin intrinsic fluorescence was correlated to severity of neuropathy (r = 0.50, P < .01) but not maximum ankle dorsiflexion, or forefoot deterioration when controlling for neuropathy. These results suggest that the interplay of intrinsic foot muscle deterioration and limited ankle mobility may be the primary contributor to the development of MTPJ deformity. Identifying these muscle and ankle motion impairments as risk factors for MTPJ deformity supports the need for targeted interventions early in the disease process to slow, or possibly stop the progression of deformity over time and reduce the risk of amputation. Level IV, case series.

AB1026 Plantar Pressure and Forefoot Deformity in the Patients with Rheumatoid Arthritis

BackgroundAt the onset of rheumatoid arthritis (RA), the forefoot is involved in approximately 20% of all patients, and during the course of the disease more than 70% of such patients...

THU0147 Predicting Eventual Need for Orthopaedic Surgery of Hand and Foot Joints. Value of Radiographic Scores in the First Three Years of RA in a Long Term Inception Cohort

BackgroundHand and foot surgery in Rheumatoid Arthritis (RA) is accepted as a surrogate marker for joint destruction and the result of failed medical treatment. The ability to predict this outcome...

AB1448-HPR The effect of customized inserts on pain, physical function and quality of life in rheumatological patients with foot pain

BackgroundRheumatoid arthritis (RA), Ankylosing spondylitis (AS), Systemic lupus erythematosus (SLE) are rheumatological diseases which cause pain and loss of function affecting the foot and ankle. In foot pain with rheumatological...

Contribution of assessing forefoot joints in early rheumatoid arthritis patients: Insights from item response theory

To evaluate the contribution of assessing forefoot joints to the measurement range and measurement precision of joint counts in early rheumatoid arthritis (RA) using item response theory. Baseline measures of tender and swollen joint counts were analyzed in 459 early RA patients from the Dutch Rheumatoid Arthritis Monitoring remission induction cohort. The contribution of forefoot joints was studied by evaluating their effect on the measurement range and measurement precision of measures based on 28-joint counts. In addition, the alignment between the patient and joint distributions was investigated to determine whether the forefoot joints were informative for measuring joint tenderness or swelling of an early RA patient. In total, 233 patients (50.76%) experienced tenderness and 200 patients (43.57%) experienced swelling in ≥1 forefoot joint. Forefoot joints were more informative for measuring joint tenderness than joint swelling, but did not significantly improve the measurement range and measurement precision of the 28-joint counts. Furthermore, including forefoot joints did not remove the existing discrepancy between the joint and patient distributions in both joint counts. Forefoot joints were frequently affected on an individual level, but did not significantly improve the measurement range or precision of 28-joint counts in patients with early RA. From a measurement perspective, reduced joint counts are appropriate for use on a population level. The contribution of assessing forefoot joints on an individual level requires further investigation. Additionally, the results should be cross-validated in patients with longer disease durations to determine whether the pattern of joint involvement is similar in later stages of RA.

A comparison between joint coordinate system and attitude vector for multi-segment foot kinematics

The joint angles of multi-segment foot models have been primarily described using two mathematical methods: the joint coordinate system and the attitude vector. This study aimed to determine whether the angles obtained through these two descriptors are comparable, and whether these descriptors have similar sensitivity to experimental errors. Six subjects walked eight times on an instrumented walkway while the joint angles among shank, hindfoot, medial forefoot, and lateral forefoot were measured. The angles obtained using both descriptors and their sensitivity to experimental errors were compared. There was no overall significant difference between the ranges of motion obtained using both descriptors. However, median differences of more than 6° were noticed for the medial-lateral forefoot joint. For all joints and rotation planes, both descriptors provided highly similar angle patterns (median correlation coefficient: R>0.90), except for the medial-lateral forefoot angle in the transverse plane (median R=0.77). The joint coordinate system was significantly more sensitive to anatomical landmarks misplacement errors. However, the absolute differences of sensitivity were small relative to the joints ranges of motion. In conclusion, the angles obtained using these two descriptors were not identical, but were similar for at least the shank-hindfoot and hindfoot-medial forefoot joints. Therefore, the angle comparison across descriptors is possible for these two joints. Comparison should be done more carefully for the medial-lateral forefoot joint. Moreover, despite different sensitivities to experimental errors, the effects of the experimental errors on the angles were small for both descriptors suggesting that both descriptors can be considered for multi-segment foot models.

Antibiotic Impregnated Cement Spacer for Salvage of Diabetic Osteomyelitis

Florid infection and osteomyelitis of the forefoot in patients with diabetic neuropathy often requires minor amputation, with risk of subsequent reulceration, reamputation, and patient dissatisfaction. We investigated use of an antibiotic-impregnated cement spacer (ACS) to release antibiotic locally to resolve residual infection and to fill the cavity created by debridement. We report 23 cases of osteomyelitis and associated severe infection of forefoot joints in 20 consecutive patients, age 60.3 +/- 13.4 years. Antibiotic-impregnated cement, extensive meticulous debridement, and ACS placement to fill the gap were employed in all cases. Deep cultures were taken routinely. Fixation with Kirschner wires was used as necessary. Mean followup was 21.2 +/- 10.2 months. A successful result was resolution of infection and wound healing to full skin closure without amputation. Of 23 cases, 21 (91.3%) healed and two required toe amputation. ACS was left permanently in 10 patients, removed with arthrodesis in six, and removed without arthrodesis in five. One patient recovered but subsequently underwent transtibial amputation due to infection of a different site. Severe infection associated with osteomyelitis of the foot in diabetic patients was successfully treated with extensive debridement and use of ACS, which filled the void created by debridement. Amputation was avoided in most patients. This procedure allowed extensive debridement through filling large voids with ACS, with prolonged antibiotic release.

Foot loading characteristics of different graduations of partial weight bearing

Limited weight bearing of the lower extremity is a commonly applied procedure in orthopaedic rehabilitation after reconstructive forefoot surgery, trauma surgery and joint replacement. The most frequent limitations are given as percentage of body weight (BW) and represent 10 or 50% BW. The extent of foot loading under these graduations of partial weight bearing has not yet been described in detail. The objective of this study was to investigate forces at the foot-sole interface, which occur under graduated limitations of weight bearing. Peak pressure, maximum force, pressure-time integral and force-time integral (Pedar Cable) were assessed for a total of three trials with 10 healthy individuals. The results from limited weight bearing with 10 or 50% BW as taught by an experienced physiotherapist with a bathroom scale were referred to results of a normal gait. The limitation of weight bearing to 10% BW was equal to a bisection of peak pressure and maximum force for the total foot. Halved BW left a remaining 82% of peak pressure and 59% of maximum force for the total foot. We concluded that weight-bearing limitations to 10 and 50% BW lead to discernible differences in foot loading and may be applied to graduate forces of the lower limb for rehabilitation purposes. Foot loading with partial weight bearing exerts the percentage of BW and should be monitored to avoid an exertion of strains on the lower limb.

Development of a multi-segment foot model for sport shoe research to quantify midfoot motion

In the past 10 years several multi-segment kinematic foot models were developed for gait analysis in clinical research in order to investigate the motion within the midfoot and forefoot joints of t...

We should not forget the foot: relations between signs and symptoms, damage, and function in rheumatoid arthritis

We studied rheumatoid arthritis (RA) patients with foot complaints to address the associations between clinical signs and symptoms, radiographic changes, and function in connection with disease duration. Secondly, we describe the contribution of several foot segments to the clinical presentation and function. In 30 RA patients with complaints of their feet, attributed to either signs of arthritis and/or radiographic damage, we compared radiographic, ultrasound, clinical, and functional parameters of the feet and ankle. Pain and swelling of the ankle were correlated weakly but statistically significantly with limitation and disability (0.273 to 0.293) as measured on the 5-Foot Function Index (FFI). The clinical signs of the forefoot joints did not influence any of the functional outcome measures. Radiographic scores for both forefeet (SvdH) and hindfeet (Larsen) were correlated with the total Health Assessment Questionnaire Disability Index (HAQ DI) and the 5-FFI limitation subscale. Pain and disease duration, more than radiographic damage, influence the total HAQ DI significantly. With the progression of time, structural damage and function of the rheumatic foot worsen in RA patients. Pain and swelling of the ankle contribute more to disability than radiographic damage of the foot and ankle.

Segmentation of foot and ankle complex based on kinematic criteria

Although various foot models were proposed for kinematics assessment using skin makers, no objective justification exists for the foot segmentations. This study proposed objective kinematic criteria to define which foot joints are relevant (dominant) in skin markers assessments. Among the studied joints, shank–hindfoot, hindfoot–midfoot and medial–lateral forefoot joints were found to have larger mobility than flexibility of their neighbour bonesets. The amplitude and pattern consistency of these joint angles confirmed their dominancy. Nevertheless, the consistency of the medial–lateral forefoot joint amplitude was lower. These three joints also showed acceptable sensibility to experimental errors which supported their dominancy. This study concluded that to be reliable for assessments using skin markers, the foot and ankle complex could be divided into shank, hindfoot, medial forefoot, lateral forefoot and toes. Kinematics of foot models with more segments must be more cautiously used.