Stiffness of the human foot and evolution of the transverse arch.

The stiff human foot enables an efficient push-off when walking or running, and was critical for the evolution of bipedalism1-6. The uniquely arched morphology of the human midfoot is thought to stiffen it5-9, whereas other primates have flat feet that bend severely in the midfoot7,10,11. However, the relationship between midfoot geometry and stiffness remains debated in foot biomechanics12,13, podiatry14,15 and palaeontology4-6. These debates centre on the medial longitudinal arch5,6 and have not considered whether stiffness is affected by the second, transverse tarsal arch of the human foot16. Here we show that the transverse tarsal arch, acting through the inter-metatarsal tissues, is responsible for more than 40% of the longitudinal stiffness of the foot. The underlying principle resembles a floppy currency note that stiffens considerably when it curls transversally. We derive a dimensionless curvature parameter that governs the stiffness contribution of the transverse tarsal arch, demonstrate its predictive power using mechanical models of the foot and find its skeletal correlate in hominin feet. In the foot, the material properties of the inter-metatarsal tissues and the mobility of the metatarsals may additionally influence the longitudinal stiffness of the foot and thus the curvature-stiffness relationship of the transverse tarsal arch. By analysing fossils, we track the evolution of the curvature parameter among extinct hominins and show that a human-like transverse arch was a key step in the evolution of human bipedalism that predates the genus Homo by at least 1.5 million years. This renewed understanding of the foot may improve the clinical treatment of flatfoot disorders, the design of robotic feet and the study of foot function in locomotion.

Managing the Severe Cavus Foot Deformity in Global Humanitarian Programs.

The cavus foot represents a complex spectrum of deformity ranging from the subtle idiopathic to the severe sensorimotor neuropathy and other neuromuscular deformities. The successful surgical treatment of the cavus foot depends on a fundamental understanding of the underlying multiplanar deformity, inherent muscle balance, and the rigidity of the hindfoot. The location of the deformity is described and understood according to its multiple apices. These deformities are addressed with osteotomies or arthrodesis directed at the apices of deformity. Simultaneously, correction of muscular imbalances with appropriate tendon transfers must also be performed to prevent recurrent deformity. With these principles in mind, the surgical correction of the cavus foot becomes simplified and algorithmically driven.

Assessing the coronal plane deformity in Charcot Marie Tooth Cavovarus feet using automated 3D measurements.

BACKGROUND: This study assesses the coronal-plane deformities in cavovarus feet secondary to Charcot-Marie-Tooth disease (CMT) using Weightbearing-CT (WBCT) and semi-automated 3D-segmentation software. METHODS: WBCTs from 30 CMT-cavovarus feet were matched to 30 controls and analysed using semi-automatic 3D-segmentation (Bonelogic, DISIOR). The software used automated cross-section sampling with subsequent straight-line representation of weighted centre points to calculate 3D axes of bones in the hindfoot, midfoot and forefoot. Coronal relationships of these axes were analysed. Supination/pronation of the bones in relation to the ground and within each joint were measured and reported. RESULTS: The most significant deformity in CMT-cavovarus feet occurred at the talonavicular joint (TNJ) with 23 degrees more supination than normal feet (6.4 ± 14.5 versus 29.4 ± 7.0 degrees, p < 0.001). This was countered by relative pronation at the naviculo-cuneiform joints (NCJ) of 7.0 degrees (-36.0 ± 6.6 versus -43.0 ± 5.3 degrees, p < 0.001). Combined hindfoot varus and TNJ supination resulted in an additive supination effect not compensated by NCJ pronation. The cuneiforms in CMT-cavovarus feet were therefore supinated by 19.8 degrees to the ground relative to normal feet (36.0 ± 12.1 versus 16.2 ± 6.8 degrees, p < 0.001). The forefoot-arch and 1st metatarsal-ground angles demonstrated similar supination to the cuneiforms suggesting no further significant rotation occurred distally. CONCLUSION: Our results demonstrate coronal plane deformity occurs at multiple levels in CMT-cavovarus feet. Majority of the supination arises at the TNJ, and this is partially countered by pronation distally, mainly at the NCJ. An understanding of the location of coronal deformities may help when planning surgical correction. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Foot Deformity in Patients With Ankylosing Spondylitis: Is It Associated With Functionality and Disease Activity?

Foot involvement affects mobility and functionality in patients with ankylosing spondylitis but it remains unknown if foot deformities in ankylosing spondylitis patients affect functionality, disease activity, and quality of life. The aim of this study was to evaluate in detail the presence of a relationship between radiologically detected foot deformities in ankylosing spondylitis patients and both clinical and electrophysiological findings. The cross-sectional study included 110 patients with ankylosing spondylitis who were diagnosed according to the Assessment in Spondyloarthritis International Society criteria and were followed in our hospital. Demographic and clinical data of all patients were recorded. Bilateral lateral foot x-rays and electrophysiology examinations were evaluated in all subjects. The arch in the dominant foot of the patients was classified in 3 groups as pes cavus, pes planus, or normal. The clinical outcomes, physical examination and electrophysiological findings were compared between the groups, and correlations were examined of the foot deformities with these parameters. Foot deformities were determined at a high rate (74.5%). These deformities affected foot pain, disability and quality of life. Pes cavus deformity was found to be associated with hip pain and enthesopathy. In the electrophysiological studies, the presence of pes planus was found to be associated with the findings of the tibial and sural nerve conduction studies, and the presence of pes cavus with the findings of the peroneal nerve conduction study. In conclusion, foot deformities may have an effect on the quality of life and functionality in ankylosing spondylitis patients.

Forefoot Adduction, Hindfoot Varus or Pes Cavus: Risk Factors for Fifth Metatarsal Fractures and Jones Fractures? A Systematic Review and Meta-Analysis.

The origin of fractures of the fifth metatarsus and Jones fracture is not clear. The goal of this study was to investigate the evidence of anatomical deformities such as metatarsus adductus, hindfoot varus, or pes cavus as risk factors for this pathology. A literature search of records related to the review question was performed screening PubMed/Medline, Embase and Cochrane library databases (last update: May 2020) according to PRISMA guidelines. A meta-analysis was performed using the mean difference of the assessed angles (in patients with the fractures vs controls) as outcome measure to summarize literature findings about metatarsus adductus angle (MAA) indicating forefoot adduction, calcaneal pitch angle (CP) indicating hindfoot cavus and varus deformity and Talo-1st metatarsus angle/Meary's angle (T1stMA) for varus alignment. Eight studies were included in the qualitative analysis (296 patients), 5 in the quantitative synthesis (132 patients). The pooled mean difference of MAA between fracture versus control group on a per patient-based analysis was 4.62 (95% CI 1.31-7.92). Statistical heterogeneity among studies was detected (I-Square: 76.1%), likely due to different patient groups and low number of studies. The pooled mean differences of CP and T1stMA among fracture group versus controls did not show statistical significance. Despite limited literature data, metatarsus adductus deformity seems to be correlated with higher risk of proximal metatarsal fractures and Jones fracture. A significant relationship between hindfoot varus or pes cavus and these fractures was not demonstrated. Further studies and trials are warranted to shed more lights on this topic.

Joint preserving procedures for painful plantar callosities in patients with flexible cavovarus foot.

BACKGROUND: The outcome of a constant joint preserving procedure for painful plantar callosities with cavovarus foot remains unclear. METHODS: Eleven patients (11 feet) who underwent lateral displacement calcaneal osteotomy (LDCO), dorsiflexion first metatarsal osteotomy (DFMO), and plantar fasciotomy (PF), simultaneously were included. The presence of painful callosities, heel alignment of standing (HA), and the Japanese Society for Surgery of the Foot ankle/hindfoot (JSSF) score were evaluated. Radiographically, the talonavicular coverage angle (TNCA), lateral talo-first metatarsal angle (LTMA), calcaneal pitch angle (CPA), and heel alignment angle (HAA) were measured. RESULTS: Postoperatively, painful plantar callosities disappeared in 10 patients and remained in one patient. The postoperative HA and JSSF score significantly improved. The postoperative TNCA, LTMA, CPA, and HAA significantly improved. CONCLUSIONS: In patients with flexible cavovarus foot, LDCO, DFMO, and PF yielded good outcomes at mid-term follow-up with preservation of the foot and ankle joints.

Technique tip: 3D printing surgical guide for pes cavus midfoot osteotomy.

BACKGROUND: Pes cavus can be defined as an abnormal elevation of the longitudinal arches, which is often secondary to a muscle imbalance. This deformity affects the foot's three dimensions (3D) and our osteotomies are usually planned on a lateral (two-dimension) X-ray. Are we really considering all the spatial components of the deformity? The aim of this study is to present a technique tip to identify the apical plane of the pes cavus deformity and perform a midfoot dorsal-based wedge resection osteotomy by using customized 3D printed surgical guides. METHODS: Three patients underwent the presented technique, all for the indication of symptomatic neuromuscular pes cavus with both anterior and posterior deformity. RESULTS: 3D-printed patient-specific guides help the surgeon to minimize human error, improving intraoperative accuracy, while reducing surgical time and intraoperative X-ray exposure. CONCLUSIONS: Closing wedge midfoot osteotomy to correct anterior pes cavus may be an interesting indication to use customized 3D printed surgical guides.

Clinical presentation and evolution of Xia-Gibbs syndrome due to p.Gly375ArgfsTer3 variant in a patient from DR Congo (Central Africa).

Xia-Gibbs syndrome (XGS) is a very rare genetic condition. The clinical spectrum is very broad and variable. The phenotype and evolution in a Congolese boy with XGS have been reported. At 6 years he had speech delay, drooling, marked hyperactivity, attention deficit, aggressive behavior, and intellectual disability. Dysmorphological evaluation revealed strabismus, mild unilateral ptosis, uplifted ear lobes, flat philtrum, thin upper lip vermillion, high arched palate, and flat feet. Patient-only whole exome sequencing identified a known pathogenic frameshift variant in the AHDC1 gene [NM_001029882.3(AHDC1):c.1122dupC;(p.Gly375ArgfsTer3)]. The clinical follow-up revealed the deterioration of his fine motor skills and significant cerebellar phenotype including tremor, pes cavus, and gait instability at the age of 12 years. This patient was compared with three previously reported patients with the same variant but did not identify a consistent pattern in the evolution of symptoms with age.

[Cavovarus foot]. / Ballenhohlfuß.

The cavovarus foot (CF) is a complex three-dimensional foot deformity. In addition to primary forms, secondary forms can be distinguished. The diagnosis of CF is made clinically; however, anamnestic information, a targeted examination including neurological status and at least radiological imaging using the hindfoot-centered imaging technique are required to determine the treatment. Conservative treatment for CF consists of the provision of insoles up to the adaptation of an orthopedic custom-made shoe, depending on the severity of the deformity. The indications for a surgical procedure are present in the case of increasing complaints, although the timing should be extensively discussed with the patient in order to be able to achieve the best functional results. Surgical treatment is generally complex but a combination of soft tissue interventions and osteotomy/arthrodesis can usually be used to achieve a plantigrade foot position and thereby enable the patient to walk with a functionally improved gait.

A histological study on the tendons at chiasma plantare in pes cavus.

INTRODUCTION: In the dysfunction of large muscles of the leg, tendon transfer surgery is found to be very helpful in restoring the normal function of these muscles. The tendons involved in the chiasma plantare play a major role in this regard. OBJECTIVE: The present cadaveric study has been carried out in cadavers presenting pes cavus. MATERIAL AND METHODS: Cadaveric feet presenting pes cavus were identified based on their foot prints. All these tendons and their interconnections were subjected to histological procedures. The sections of the tendons were stained with hematoxylin and eosin in order to identify the underlying pathologies in the tendons. RESULTS: Various types of tendinous interconnections between the tendons of flexor digitorum longus and flexor hallucis longus were noted. The histological findings showed infiltration of lymphocytes in the tendon sheath indicating tenosynovitis and tendinitis. This could be attributed to the compression of the tendons. A few tendons were also stretched due to the skeletal framework of the foot in pes cavus. The bones along the medial longitudinal arch in pes cavus feet could tend to develop spurs or elongated tuberosity that could impinge on the tendons causing the tendons to stretch and elongate. CONCLUSION: In harvesting the tendons for grafting, the surgeons must be aware about the pathologies involved, such as tendinitis or tenosynovitis, in order to reduce the time taken for the healing of the graft post-surgery. These variations and histological findings can sub-serve as an efficient guide for the restoration of non-functioning muscles of the lower limb.

Pes cavovarus in Charcot-Marie-Tooth compared to the idiopathic cavovarus foot: A preliminary weightbearing CT analysis.

BACKGROUND: Pes cavovarus is a foot deformity that can be idiopathic (I-PC) or acquired secondary to other pathology. Charcot-Marie-Tooth disease (CMT) is the most common adult cause for acquired pes cavovarus deformity (CMT-PC). The foot morphology of these distinct patient groups has not been previously investigated. The aim of this study was to assess if morphological differences exist between CMT-PC, I-PC and normal feet (controls) using weightbearing computed tomography (WBCT). METHODS: A retrospective analysis of WBCT scans performed between May 2013 and June 2017 was undertaken. WBCT scans from 17 CMT-PC, 17 I-PC and 17 healthy normally-aligned control feet (age-, side-, sex- and body mass index-matched) identified from a prospectively collected database, were analysed. Eight 2-dimensional (2D) and three 3-dimensional (3D) measurements were undertaken for each foot and mean values in the three groups were compared using one-way ANOVA with the Bonferroni correction. RESULTS: Significant differences were observed between CMT-PC or I-PC and controls (p<0.05). Two-dimensional measurements were similar in CMT-PC and I-PC, except for forefoot arch angle (p=0.04). 3D measurements (foot and ankle offset, calcaneal offset and hindfoot alignment angle) demonstrated that CMT-PC exhibited more severe hindfoot varus malalignment than I-PC (p=0.03, 0.04 and 0.02 respectively). CONCLUSIONS: CMT-related cavovarus and idiopathic cavovarus feet are morphologically different from healthy feet, and CMT feet exhibit increased forefoot supination and hindfoot malalignment compared to idiopathic forms. The use of novel three-dimensional analysis may help highlight subtle structural differences in patients with similar foot morphology but aetiologically different pathology. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Distance mapping of the foot and ankle joints using weightbearing CT: The cavovarus configuration.

INTRODUCTION: The goal of this study was to characterize the abnormal joint surface interaction at the ankle, hindfoot and midfoot joints of the cavovarus foot using distance mapping on weightbearing computed tomography (WBCT) images by comparing a series of cavovarus feet to a series of normally-aligned feet. METHODS: In this case-control study, ten feet (10 patients) with asymptomatic cavovarus shape (cases; N = 10) were compared to 10 matched-paired (by age, gender and body mass index) normally-aligned feet (10 patients) (controls; N = 10). Three-dimensional models were produced from the images and distance maps representing joint surface configuration were generated for the ankle, hindfoot and midfoot joints. The distance maps for each joint were then compared between the two groups and between regions in the same group. RESULTS: In the cavovarus group there was a significant increase in surface-to-surface distance at the posterior tibiotalar joint and a reduced distance at the anterior part, together with a greater distance at the posterior half of the medial gutter. Also, a decrease in surface-to-surface distance on the anterior half of the anterior facet and an increased distance on the posterior quadrants of the posterior facet of the subtalar joint were found. At the sinus tarsi, the lateral aspect of the talonavicular joint, the naviculocuneiform and the tarsometatarsal joints there was a statistically significant increase in surface-to-surface distance in cavovarus patients as compared to controls. CONCLUSION: Distance mapping analysis on WBCT images identified significant differences in surface-to-surface interaction at the foot and ankle joints between cavovarus and normally-aligned feet. LEVEL OF EVIDENCE: Level III, case-control study.

Assessment and Management of the Pediatric Cavovarus Foot.

The cavovarus foot is challenging to treat. The deformity is typically progressive with an unpredictable natural history. There are concurrent deformities in the fore-, mid-, and hindfoot: the medial arch is elevated, the first ray is plantarflexed, and the heel is in varus. Muscle imbalance and joint contractures are common. Successful correction requires confirmation of the underlying diagnosis and the application of principles to select the appropriate surgical procedures.

[Hindfoot-centred X-ray technique for the evaluation of cavovarus deformity : A proposal for the optimization of radiologic delineation]. / Die "rückfußzentrierte Röntgentechnik" zur Erfassung von Cavovarusdeformitäten : Vorschlag zur Optimierung der radiologischen Darstellung.

In surgical correction of cavovarus deformity bony hindfoot procedures are required in most cases. For treatment planning X­rays in two or more planes are usually used. In conventional X­ray-techniques the hindfoot and ankle joint are presented in a more or less outward rotated position. Moreover, the peritalar complex is not delineated in the most corrected position. Therefore, the frequently used talus-metatarsal-I-angle (Meary angle) cannot be measured correctly. By application of the Coleman block test and additional adjustment of the malrotation in the lateral view, the peritalar complex and ankle joint can be evaluated in the corrected and "hindfoot-centred" position. Also, the frequently seen anterior ankle impingement can be observed precisely. Planning of osteotomies or corrective peritalar fusions is supported thereby. Some treatment examples are presented.

Intraobserver and interobserver reliability of cone beam weightbearing semi-automatic three-dimensional measurements in symptomatic pes cavovarus.

INTRODUCTION: Pes cavovarus is a three-dimensional (3D) foot deformity. New 3D semi-automatic measurements utilising weightbearing computerised topography (WBCT) images have recently been proposed to assess hindfoot alignment, but reliability in pes cavovarus has never been investigated. The aim of this study was to assess intraobserver and interobserver reliability of the foot ankle offset (FAO), calcaneal offset (CO) and hindfoot alignment angle (HAA) in pes cavovarus. METHODS: Anonymised WBCT datasets from 51 feet (17 Charcot-Marie-Tooth related cavovarus, 17 idiopathic cavovarus and 17 controls) were retrospectively reviewed. Three observers (two senior foot and ankle fellows and one orthopaedic resident) independently measured FAO, CO and HAA using dedicated software, with measurements repeated two weeks apart. Subgroup analysis was performed to assess whether aetiology or severity of varus deformity and level of seniority affected reliability. RESULTS: Mean values for intra and interobserver reliability for FAO (r=0.98; ICC: 0.99), CO (r=0.97; ICC: 0.98) and HAA measurements (r=0.97; ICC: 0.98) were excellent. Subgroup analyses showed that FAO, CO and HAA's intra (r/ρ range, 0.77-0.95) and interobserver (ICC range, 0.88-0.98) reliability remained excellent in patients with Charcot-Marie-Tooth related cavovarus, idiopathic pes cavovarus and normal feet, regardless of the severity of deformity. No difference was found in FAO, CO and HAA mean values from three observers (p>0.05 in all cases). DISCUSSION: This study demonstrates that 3D semi-automatic measurements of WBCT images have excellent intra and interobserver reliability in the assessment of hindfoot alignment in pes cavovarus. Aetiology and severity of deformity, and level of seniority do not affect reliability of these measurements. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Is subtle cavus foot a risk factor for chronic ankle instability? Comparison of prevalence of subtle cavus foot between chronic ankle instability and control group on the standing lateral radiograph.

BACKGROUND: Subtle cavus foot (SCF) is an entity characterized by mild cavus. However, few studies have examined whether a SCF may be a risk factor for chronic ankle instability (CAI). METHODS: This study included 116 patients who underwent lateral ankle ligament repair (modified Broström operation) for CAI and 105 controls. We used the standing lateral radiograph, so compared calcaneal pitch angle, Meary's angle, heights of the first and fifth metatarsal bases, and fibular positions between groups. Additionally, two observers subjectively rated the standing lateral radiographs for the presence of SCF. RESULTS: There were no significant intergroup differences in any of the radiographic angles. The prevalence of SCF was 20.7% in the CAI group and 18.1% in the control group according to observer 1 versus 21.6% and 28.6% (CAI group and control group, respectively) according to observer 2. There were no significant intergroup differences in the proportion of SCF between the two observers (p=0.105 and 0.211, respectively). CONCLUSION: SCF was not a significant risk factor for CAI when judging by standing lateral radiograph, and the detection of SCF seems to require considerable experience. Thus, care should be taken when determining whether to perform corrective osteotomies when treating CAI patients with SCF. LEVEL OF EVIDENCE: III, case control.

Foot measures in patients with pes cavus with and without charcot-marie-tooth disease: A pilot study.

INTRODUCTION: Pes cavus often signals the presence of Charcot-Marie-Tooth (CMT) in adult patients, although its prevalence in the general population makes it a finding of unclear significance. METHODS: We undertook a pilot double cohort study to investigate the feasibility of comparing preselected bedside and radiographic foot measures in pes cavus patients with and without CMT. RESULTS: A total of 16 CMT and 11 non-CMT patients were recruited. Although no findings consistently met statistical significance, recruitment was highly limiting. CONCLUSIONS: Formalized foot measurement comparisons of CMT and non-CMT pes cavus are feasible. Larger studies will be necessary to determine if there are differences in foot structure based on the presence of a hereditary neuropathy. Muscle Nerve 59:122-125, 2019.

Case 255: Foot Binding.

History A 99-year-old Chinese-Indonesian woman with a longstanding history of diabetes mellitus was admitted for chest infection and was incidentally found to have bilateral deformed feet. She was otherwise asymptomatic and could ambulate independently. Photographs and radiographs of the feet were obtained.

An Analysis of Relative Gait Impairment in Commonly Diagnosed Pediatric Conditions.

BACKGROUND: Gait indices were developed to represent the magnitude of impairment extracted from a gait analysis with a single value. The Gillette Gait Index (GGI), and the Gait Deviation Index (GDI) are 2 widely used indices that represent gait impairment differently based on their statistical properties. Our purpose was to (1) report on the results of gait analysis for a broad spectrum of pediatric conditions using the GGI and GDI, and (2) identify the parameters that dominate impairment. METHODS: A total of 1439 children with 13 different diagnoses with a complete, baseline gait analysis were identified. The GGI and its 16 parameters were calculated in all cases, and the GDI was calculated from a smaller subset. T tests, and z-scores were used to compare each of these values to typically developing children for each diagnosis. A separate linear regression controlling for age, sex, and use of an orthosis, or assistive device was performed for the GGI. RESULTS: In our series, there were 71 typically developing children with a GGI of 31. We qualify relative gait impairment as severe, mild, or moderate as based on the GGI, and propose that values <100 represent mild, 100 to 200 represent moderate, and >200 represents severe impairment. On the basis of strong correlation between the GGI and GDI, we suggest that GDI values >80 represent mild, and values <70 represent severe impairment. T tests and z-scores demonstrated that both the number and magnitude of abnormal parameters increase the GGI. These tests also identified the most clinically relevant parameters contributing to functional impairment for each diagnosis. Multivariate linear regression showed that all diagnoses except flatfoot and scoliosis demonstrated statistically significant differences in GGI scores. CONCLUSIONS: This is the first study to apply these gait indices to a large population of diverse pediatric conditions. We propose GGI and GDI values to qualify gait impairment among these conditions as severe, moderate, or mild. Furthermore, impairment in gait reflects both the number and magnitude of abnormal parameters within each condition. LEVEL OF EVIDENCE: Level III-retrospective comparative study.