The mechanical role of the metatarsophalangeal joint in human jumping.

This study investigated the mechanical role of metatarsophalangeal (MTP) joints in human jumping. Eighteen healthy young men performed three types of single-leg jumps (SJ: squat jump; CMJ: countermovement jump; HJ: standing horizontal jump) on a force plate under barefoot (BARE) and forefoot immobilisation (FFIM) conditions. For FFIM, the forefoot was immobilised around the MTP joints of the dominant leg by a custom-made splint. Force-time components and the centre of pressure (COP) trajectory were measured from the ground reaction force (GRF) in the take-off phase of jumping. The vertical jump heights calculated from the net vertical impulse were lower under FFIM than under BARE during the CMJ (p < 0.05). The HJ distance under FFIM was significantly shorter than that under BARE (p < 0.01). The relative net vertical impulse was lower under FFIM than under BARE during the CMJ (p < 0.05). During the HJ, all the horizontal GRF variables were significantly lower under FFIM than under BARE (p < 0.01), but none of the vertical GRF variables differed between the two conditions. The horizontal relative GRF in the 90-95% of the final take-off phase during the HJ was significantly lower under FFIM than under BARE (p < 0.01). Under FFIM, the COP range in the antero-posterior direction in the take-off phase of the HJ decreased (p < 0.05), whereas its range in the anterior direction for the SJ and CMJ increased (p < 0.05). The results of this study indicate that MTP joint motion can play an important role in regulating force-generating capacities of toe flexor muscles in the take-off phase of human jumping, especially in the horizontal direction of horizontal jumping.

Finite Element Modeling of Planus and Rectus Foot Types for the Study of First Metatarsophalangeal and First Metatarsocuneiform Joint Contact Mechanics.

The foot is a highly complex biomechanical system for which finite element (FE) modeling has been used to evaluate its loading environment. However, there is limited knowledge of first metatarsophalangeal (MTP) and first metatarsocuneiform (MTC) joint contact mechanics. Our goal was to develop a framework for FE modeling of the medial forefoot which could accurately predict experimental measurements of first MTP and first MTC joint loading. Simulations of planus and rectus foot types were conducted for midstance of gait. A custom-built force-controlled cadaveric test-rig was used to derive intracapsular pressure sensor measurements of contact pressure, force, and area during quasi-static loading. The FE model was driven under the same boundary and loading conditions as the cadaver. Mesh sensitivity analyses and best-fit calibrations of moduli for first MTP and first MTC joint cartilage were performed. Consistent with previous experimental research, a lower compressive modulus was best-fit to the first MTP compared to first MTC joint at 10 MPa and 20 MPa, respectively. Mean errors in contact pressures, forces, and areas were 24%, 4%, and 40% at the first MTP joint and 23%, 12%, and 19% at the first MTC joint, respectively. The present developmental framework may provide a basis for future modeling of first MTP and first MTC joint contact mechanics. This study acts as a precursor to validation of realistic physiological loading across gait to investigate joint loading, foot type biomechanics, and surgical interventions of the medial forefoot.

The rise of the longitudinal arch when sitting, standing, and walking: Contributions of the windlass mechanism.

The original windlass mechanism describes a one-to-one coupling between metatarsal joint dorsiflexion and medial longitudinal arch rise. The description assumes a sufficiently stiff plantar aponeurosis and absence of foot muscle activity. However, recent research calls for a broader interpretation of the windlass mechanism that accounts for an extensible plantar aponeurosis and active foot muscles. In this study, we investigate the rise of the arch in response to toe dorsiflexion when sitting, standing, and walking to discuss the windlass mechanism's contributions in static and dynamic load scenarios. 3D motion analysis allowed a kinematic investigation of the rise and drop of the arch relative to the extent of toe dorsiflexion. The results suggest that static windlass effects poorly predict the relationship between arch dynamics and metatarsophalangeal joint motion during dynamic load scenarios, such as walking. We were able to show that toe dorsiflexion resulted in an immediate rise of the longitudinal arch during sitting and standing. In contrast, a decrease in arch height was observed during walking, despite toe dorsiflexion at the beginning of the push-off phase. Further, the longitudinal arch rose almost linearly with toe dorsiflexion in the static loading scenarios, while the dynamic load scenario revealed an exponential rise of the arch. In addition to that, the rate of change in arch height relative to toe motion was significantly lower when sitting and standing compared to walking. Finally, and most surprisingly, arch rise was found to correlate with toe dorsiflexion only in the dynamic loading scenario. These results challenge the traditional perspective of the windlass mechanism as the dominating source of foot rigidity for push-off against the ground during bipedal walking. It seems plausible that other mechanisms besides the windlass act to raise the foot arch.

Effects of Short-Term Limitation of Movement of the First Metatarsophalangeal Joint on the Biomechanics of the Ipsilateral Hip, Knee, and Ankle Joints During Walking.

BACKGROUND We analyzed the effect of limitation of movement of the first metatarsophalangeal joint (FMJ) on the biomechanics of the lower limbs during walking. MATERIAL AND METHODS Eight healthy college students completed walking under barefoot (BF) and FMJ constraint (FMJC) conditions. We synchronously collected kinematics and dynamics data, and calculated the torque, power, and work of hip, knee, and ankle joints. RESULTS Compared with normal conditions, when the FMJ is restricted from walking, the maximum ankle dorsiflexion angle is significantly increased (P<0.001), the maximum plantar flexion angle is significantly reduced (P<0.001), the maximum plantar flexion torque (P<0.001) and the maximum dorsiflexion torque (P<0.05) increased significantly, the maximum power increased significantly (P<0.001), the minimum power decreased significantly (P<0.001), and the negative work increased significantly (P<0.001). The torque of hip and knee joints increased significantly (P<0.05). CONCLUSIONS After the movement of the FMJ is restricted, the human body mainly compensates and transfers compensation by increasing the angle of dorsiflexion, increasing work and the activity level of surrounding muscles through the ankle joint, thereby increasing the torque load of the knee and hip joints to maintain the dynamic balance of kinematics. FMJC condition increases the energy consumption of the human ankle, knee, and hip joints during walking. The load is compensated by the gradual attenuation of the ankle, knee, and hip. Long-term limitation may cause damage to the posterior calf muscles and increase the incidence of knee arthritis.

Effect of consecutive jumping trials on metatarsophalangeal, ankle, and knee biomechanics during take-off and landing.

This study examined the differences in single and consecutive jumps on ground reaction forces (GRF) as well as metatarsophalangeal (MTP), ankle and knee kinematics and kinetics during jumping take-off and landing. Eighteen basketball players performed countermovement jumps in both single and consecutive movement sessions. Synchronised force platform and motion capture systems were used to measure biomechanical variables during take-off and landing. Paired t-tests (or Wilcoxon signed-rank tests) were performed to examine any significant differences regarding mean and coefficient of variation in each of the variables tested. A Holm-Bonferroni correction was applied to P-values to control the false discovery rate of 5%. The findings indicated that consecutive jumps had lower jump height, take-off velocity and landing impact. During take-off, consecutive jumps demonstrated larger peak MTP and ankle extension velocities, knee extension moments as well as larger values for ankle and knee power generation; During landing, the consecutive jumps had larger peak MTP flexion angle, joint velocities (MTP, ankle and knee), and peak knee flexion moments and power absorption. Additionally, consecutive jumps had higher within-trial reliability (i.e. smaller CV) for peak MTP flexion angle at landing (P < 0.05), but lower reliability (i.e. higher CV) for peak knee flexion velocity and power absorption at landing. These results suggest that the consecutive jump trials led to distinct movement kinematics and higher loading responses in jump take-off and landing.

Ossification timeline of sesamoid bones at metatarsophalangeal joints.

Ossification timeline is a critical issue in studies regarding sesamoid bones at metatarsophalangeal (MTP) joints, but actual knowledge is still incomplete. The present study determines the cutoff age of sesamoids ossification at MTP joints. We conducted a retrospective review of radiographs of the feet from 5553 males and 3225 females between November 2005 and September 2012 to identify presence of sesamoids at 5 MTP joints and 3 variations of hallucal sesamoids. Age-specific prevalence of each presence and variations was calculated and clustered to produce latent age groups corresponding to the sesamoid ossification process in males and females, respectively. Males older than 7 years of age were divided into 5 age groups (8-11, 12-15, 16-29, 30-76, and 77-92 years), while females were classified into 4 age groups (8-11, 12-26, 27-76, and 77-92 years). According to the characteristics of sesamoid prevalence in each age group, the pre-ossification stage was defined at age 1-7 years in both genders and the ossifying stage was defined at age 8-29 years in males and 8-26 years in females. We also defined ossified stage as age 30-92 years in male and 27-92 years in females. The ossifying and ossified stages include 2 or 3 substages in both genders. A clustering analysis provided novel cutoff age points as ossification timelines for the sesamoid bones at MTP joints in males and females, which may have an impact on future sesamoid and skeletal development research.

What goes up must come down: Consequences of jump strategy modification on dance leap take-off biomechanics.

Chronic foot and ankle injuries are common in dancers; understanding how lower extremity loading changes in response to altered task goals can be beneficial for rehabilitation and injury prevention strategies. The purpose of this study was to examine mechanical demands during jump take-offs when the task goal was modified to focus on either increasing jump distance or increasing jump height. It was hypothesized that a jump strategy focused on height would result in decreased energetic demands on the foot and ankle joints. Thirty healthy, experienced female dancers performed saut de chat leaps while travelling as far as possible (FAR) or jumping as high as possible (UP). Ground reaction force (GRF) impulses and peak sagittal plane net joint moments and sagittal plane mechanical energy expenditure (MEE) of the metatarsophalangeal (MTP), ankle, knee, and hip joints were calculated. During take-off, vertical and horizontal braking GRF impulses were greater and horizontal propulsive GRF impulse was lower in the UP condition. MEE at the MTP, ankle, and hip joints was lower in UP, and MEE at the knee was higher in UP. These results suggest that a strategy focused on height may be helpful in unloading the ankle and MTP joints during dance leaps.

Systematic Review of the Role of Footwear Constructions in Running Biomechanics: Implications for Running-Related Injury and Performance.

Although the role of shoe constructions on running injury and performance has been widely investigated, systematic reviews on the shoe construction effects on running biomechanics were rarely reported. Therefore, this review focuses on the relevant research studies examining the biomechanical effect of running shoe constructions on reducing running-related injury and optimising performance. Searches of five databases and Footwear Science from January 1994 to September 2018 for related biomechanical studies which investigated running footwear constructions yielded a total of 1260 articles. After duplications were removed and exclusion criteria applied to the titles, abstracts and full text, 63 studies remained and categorised into following constructions: (a) shoe lace, (b) midsole, (c) heel flare, (d) heel-toe drop, (e) minimalist shoes, (f) Masai Barefoot Technologies, (g) heel cup, (h) upper, and (i) bending stiffness. Some running shoe constructions positively affect athletic performance-related and injury-related variables: 1) increasing the stiffness of running shoes at the optimal range can benefit performance-related variables; 2) softer midsoles can reduce impact forces and loading rates; 3) thicker midsoles can provide better cushioning effects and attenuate shock during impacts but may also decrease plantar sensations of a foot; 4) minimalist shoes can improve running economy and increase the cross-sectional area and stiffness of Achilles tendon but it would increase the metatarsophalangeal and ankle joint loading compared to the conventional shoes. While shoe constructions can effectively influence running biomechanics, research on some constructions including shoe lace, heel flare, heel-toe drop, Masai Barefoot Technologies, heel cup, and upper requires further investigation before a viable scientific guideline can be made. Future research is also needed to develop standard testing protocols to determine the optimal stiffness, thickness, and heel-toe drop of running shoes to optimise performance-related variables and prevent running-related injuries.

Evaluation of the Association Between Plantar Fasciitis and Hallux Valgus.

BACKGROUND: The windlass mechanism, first described by John Hicks in 1954, defines the anatomical and biomechanical relationship between the hallux and the plantar fascia. Hallux valgus (HV) and plantar fasciitis are the most common foot disorders, and, to date, no study has evaluated the relationship between these disorders. The purpose of this study was to determine the incidence of and factors associated with plantar fasciitis in patients with HV deformity. METHODS: In this prospective observational study, 486 patients with HV were divided into three groups according to stage of HV deformity. Patient sex, age, and body mass index were recorded. Presence of accompanying plantar fasciitis and heel spur was investigated by physical and radiographic examination. First metatarsophalangeal joint dorsiflexion of the affected side was measured. Patients with or without plantar fasciitis were also compared to evaluate factors associated with plantar fasciitis. RESULTS: Mean age and body mass index of the patients were significantly different among the three HV groups. The incidence of plantar fasciitis and heel spur significantly increased in correlation with the severity of HV deformity. Increased age and HV stage and decreased first metatarsophalangeal joint dorsiflexion were significantly associated with presence of plantar fasciitis in HV. CONCLUSIONS: In this study, the incidence of plantar fasciitis was significantly increased in correlation with the severity of HV deformity. Significant association was found between plantar fasciitis and HV, which are anatomically and biomechanically related to each other by the windlass mechanism.

Effectiveness and Duration of Plantar Pressure Off-loading by Two Designs of Felt Padding: A Preliminary Study.

BACKGROUND: The aim of this study was to observe the pressure changes in the felt padding used to off-load pressure from the first metatarsal head, the effects obtained by different designs, and the loss of effectiveness over time. METHOD: With a study population of 17 persons, two types of 5-mm semicompressed felt padding were tested: one was C-shaped, with an aperture cutout at the first metatarsophalangeal joint, and the other was U-shaped. Pressures on the sole of the foot were evaluated with a platform pressure measurement system at three time points: before fitting the felt padding, immediately afterward, and 3 days later. RESULTS: In terms of decreased mean pressure on the first metatarsal, significant differences were obtained in all of the participants (P < .001). For plantar pressures on the central metatarsals, the differences between all states and time points were significant for the C-shaped padding in both feet (P < .001), but with the U-shaped padding the only significant differences were between no padding and padding and at day 3 (P = .01 and P = .02). CONCLUSIONS: In healthy individuals, the U-shaped design, with a padding thickness of 5 mm, achieved a more effective and longer-lasting reduction in plantar pressure than the C-shaped design.

Increased toe-flexor muscle strength does not alter metatarsophalangeal and ankle joint mechanics or running economy.

The intrinsic foot musculature (IFM) supports the arches of the foot and controls metatarsophalangeal joint (MTPJ) motion. Stronger IFM can increase the effective foot length, potentially altering lower-extremity gearing similar to that of using carbon-fibre-plated footwear. The purpose of this study was to investigate if strengthening of the IFM can alter gait mechanics and improve running economy. Eleven participants were randomly assigned into an experimental group and nine into a control group. The experimental group performed IFM strengthening exercises for ten weeks. Toe-flexor strength, gait mechanics, and running economy were assessed at baseline, five weeks, and ten weeks; using a custom strength testing apparatus, motion capture and force-instrumented treadmill, and indirect calorimetry. Toe-flexor strength increased in the experimental group (p = .006); however, MTPJ and ankle mechanics and running economy did not change. The dearth of changes in mechanics may be due to a lack of mechanical advantage of the IFM, runners staying within their preferred movement path, a need for MTPJ dorsiflexion to facilitate the windlass mechanism, or the primary function of the IFM being to support the longitudinal arch of the foot as opposed to modulating MTPJ mechanics.

Dynamic angular stiffness about the metatarsophalangeal joint increases with running speed.

Altering the longitudinal bending stiffness of footwear has the potential to affect mechanics of the metatarsophalangeal (MTP) joint. Recent efforts have been put forth to identify an optimal bending stiffness of footwear to improve running performance. However, little is known about how this optimal bending stiffness may change with running speed. The purpose of this study was to investigate how dynamic angular stiffness about the MTP joint changes across running speeds. Eighteen participants ran at five speeds from 3.89 to 6.11 m/s. Metatarsophalangeal joint angles, moments, and stiffness were estimated for each speed. Two MTPJ load-displacement metrics were defined, active and critical stiffness. Instantaneous stiffness of the MTP joint was also quantified. There was a significant main effect of speed on critical stiffness (p < .001), maximum MTP moment (p < .001), MTP moment at maximum dorsiflexion (p < .001), and MTP range of motion (p = .013). There was no effect of speed on active stiffness (p = .094). These results support the notion that involvement of the MTP joint increases with running speed. Individual contributions of the foot and shoe to the MTP joint moment and stiffness suggest that the foot appears to dominate the stiffness of the foot-shoe complex and torque generation about the MTP joint. Instantaneous stiffness fluctuated throughout stance phase, suggesting that foot-shoe complex stiffness is time dependent. The ratio by which critical stiffness and MTP joint range of motion increase with running speed may provide insight for how to guide construction of performance footwear. These results suggest that when utilizing MTP joint mechanics for insights into designing a shoe for performance purposes, the effect of speed should be taken into consideration.

Horizontal force production and multi-segment foot kinematics during the acceleration phase of bend sprinting.

This paper investigated horizontal force production, foot kinematics, and metatarsophalangeal (MTP) joint push-off axis use during acceleration in bend (anti-clockwise) and straight-line sprinting. It was hypothesized that bend sprinting would cause the left step push-off to occur about the oblique axis, resulting in a decrease in propulsive force. Three-dimensional kinematic and ground reaction force data were collected from nine participants during sprinting on the bend (36.5 m radius) and straight. Antero-posterior force was reduced at 38%-44% of stance during bend sprinting compared with the straight. This coincided with an increase in mediolateral force for the majority of the stance phase (3%-96%) on the bend compared with the straight. In addition, a lower propulsive impulse was reported on the bend compared with the straight. Analysis of multi-segment foot kinematics provides insight into the possible mechanisms behind these changes in force production. Mean mediolateral center of pressure position was more lateral in relation to the second metatarsal head in the left step on the bend compared with the straight, indicating the oblique axis was used for push-off at the MTP joint. Greater peak joint angles of the left foot were also reported, in particular, an increase in left step midfoot eversion and internal ankle rotation. It is possible these changes in joint kinematics are associated with the observed decrease in propulsive force. Therefore, practitioners should seek to strengthen muscles such as tibialis posterior in frontal and sagittal planes and ensure specificity of training which may aid in addressing these force reductions.

Establishing a common instantaneous center of rotation for the metatarso-phalangeal and metatarso-sesamoid joints: a theoretical geometric model based on specific morphometrics.

BACKGROUND: Previous research has identified separate sagittal plane instantaneous centers of rotation for the metatarso-phalangeal and metatarso-sesamoid joints, but surprisingly, it does not appear that any have integrated the distinctive morphological characteristics of all three joints and their respective axes into a model that collectively unifies their functional motions. Since all joint motion is defined by its centers of rotation, establishing this in a complicated multi-dimensional structure such as the metatarso-phalangeal-sesamoid joint complex is fundamental to understanding its functionality and subsequent structural failures such as hallux abducto valgus and hallux rigidus. METHODS: Based on a hypothesis that it is possible to develop an instantaneous center of rotation common to all four osseous structures, specific morphometrics were selected from a sequential series of 0.5-mm sagittal plane C-T sections in one representative cadaver specimen randomly selected from a cohort of nine, seven which were obtained from the Body Donation Program, Department of Anatomy, University of California, San Diego School of Medicine, and two which were in the possession of one author (MD). All mature skeletal specimens appeared grossly normal, shared similar morphological features, and displayed no evidence of prior trauma, deformity, or surgery. Specific C-T sections isolated the sagittal plane characteristics of the inter-sesamoidal ridge and each sesamoid groove, and criteria for establishing theoretical sesamoid contact points were established. From these data, a geometric model was developed which, to be accurate, had to closely mimic all physical and spatial characteristics specific to each bone, account for individual variations and pathological states, and be consistent with previously established metatarso-phalangeal joint functional motion. RESULTS: Sequential sagittal plane C-T sections dissected the metatarsal head from medial to lateral and, at approximately midway through the metatarsal head, the circular nature of the inter-sesamoidal ridge (crista) was isolated; other C-T sections defined, respectively, the elliptical characteristics of the tibial (medial) and fibular (lateral) sesamoid grooves in each specimen. A general plane model representing the most basic form of the joint was developed, and its center of rotation was established with a series of tangential and normal lines. Simplified tibial sesamoid and fibular plane models were developed next which, when combined, permitted the development of a spherical model with three separate contact points. Based on the morphometrics of each sesamoid groove and a more distally positioned tibial sesamoid, the model was modified to accurately define the center of rotation and one distinctive sagittal plane geometric and functional characteristic of each groove. CONCLUSION: Consistent with our hypothesis, this theoretical geometric model illustrates how it is possible to define an instantaneous center of rotation common to all three joints while simultaneously accounting for morphometric and spatial variability. This should provide additional insight into metatarso-phalangeal-sesamoid joint complex functionality and the physical characteristics that contribute to its failure.

A comparison of metatarsophalangeal joint center locations on estimated joint moments during running.

The forefoot functions as the base of support during late stance, rotating about the dual-axis of the metatarsophalangeal joints. Previous research has shown that joint axis definition affects estimated joint moments about the forefoot. However, little is known about how metatarsophalangeal joint center definition affects estimated joint kinetics. This study compared moments about the metatarsophalangeal joint using four different defined joint centers. There was a significant difference (p < .001) in peak moments between joint center definitions, differing by up to 0.488 N-m/kg for the slow and 0.878 N-m/kg for the fast running speeds tested. Additionally, there was a significant difference (p < .001) for when peak plantar flexor moment occurred during the slower running condition. The more posteriorly oriented joint centers resulted in higher moments and earlier onset of the plantar flexor moment. In addition to careful modeling of the metatarsophalangeal joint axis, it is recommended that joint center definition should be considered as well.

An analysis of the foot in turnout using a dance specific 3D multi-segment foot model.

INTRODUCTION: Recent three-dimensional (3D) kinematic research has revealed foot abduction is the strongest predictor of standing functional and forced turnout postures. However, it is still unknown how the internal foot joints enable a large degree of foot abduction in turnout. The primary purpose of this study was to use a dance specific multi-segment foot model to determine the lower leg and foot contributions to turnout that female university-level ballets use to accentuate their turnout. METHODS: Eighteen female dance students (mean age, 18.8 ± 1.6 years) volunteered for this study. Retro-reflective markers were attached to the dancers' dominant foot. Each dancer performed three repetitions of functional turnout, forced turnout and ten consecutive sautés in first position. Repeated measures ANOVA with Bonferroni adjustments for the multiple comparisons were used to determine the kinematic adjustments, hindfoot eversion, midfoot and forefoot abduction, navicular drop (i.e. lowering of the medial longitudinal arch) and first metatarsophalangeal joint abduction between natural double leg up-right posture and the first position conditions. RESULTS: Hindfoot eversion (4.6°, p < 0.001) and midfoot abduction (2.8°, p < 0.001) significantly increased in functional turnout compared to the natural double leg up-right posture. Thirteen dancers demonstrated increased first metatarsophalangeal joint (MTPJ) abduction in forced turnout, however no statistically significant increase was found. Navicular drop during sautés in first position significantly increased by 11 mm (p < 0.001) compared to the natural double leg up-right posture. CONCLUSION: Our findings suggest dancers do pronate, via hindfoot eversion and midfoot abduction in both functional and forced turnout, however, no immediate association was found between forced turnout and first MTPJ abduction. Foot pronation does play a role in achieving turnout. Further prospective research on in situ measures of the lower limb in turnout and injury surveillance is required to improve our understanding of the normal and abnormal dance biomechanics.

Range of Motion of the First Metatarsophalangeal Joint After Different Capsulorrhaphies: A Comparative Cadaver Study.

BACKGROUND: Capsulorrhaphy restricts the motion of the first metatarsophalangeal joint (MTPJ) in hallux valgus surgery. However, changes in motion of the first MTPJ immediately after surgery that resulted from different capsulorrhaphy methods have not been compared. The primary aim of this study was to compare the immediate effect of Y-shaped and inverted L capsulorrhaphy methods on the range of motion (ROM) of the first MTPJ. METHODS: Y-shaped and inverted L capsulorrhaphies were performed on 16 human cadaveric feet. Passive dorsiflexion and plantarflexion of the first MTPJ were then compared preoperatively and postoperatively. RESULTS: In this cadaveric study, the inverted L capsulorrhaphy method led to a ROM loss in the first MTPJ; the joint stiffness from the Y-shaped capsulorrhaphy is significantly less than that from the inverted L capsulorrhaphy. CONCLUSIONS: The inverted L capsulorrhaphy may lead to a ROM loss in the first MTPJ immediately after surgery. We recommend that surgeons close the capsule of the first MTPJ with a Y-shaped capsulorrhaphy, which is less likely to result in a ROM loss in the first MTPJ in the early postoperative period.

A semi-quantitative technique to assess excursion of the flexor hallucis longus.

BACKGROUND: Recent research indicates that restriction in excursion of flexor hallucis longus (FHL) contributes to hallux rigidus development. As described in the literature, clinical evaluation of FHL excursion has poor interobserver reliability. A simple, inexpensive, easily used FHL relative excursion measurement device was developed and tested. METHODS: 64 subjects were enrolled with shoe size, height, weight, BMI, and age compared. Using a footplate and series of mechanical wedges, maximum ankle dorsiflexion was measured with the great toe in 15°, 30°, and 45° of dorsiflexion. RESULTS: Ankle dorsiflexion decrease with progressive hallux dorsiflexion increase was statistically significant with a linear correlation (r2=.814 p<.001) and was not statistically related to shoe size, height, weight, BMI, or age. CONCLUSIONS: This technique provides consistent assessment of the limitation to ankle dorsiflexion incurred by decreased FHL excursion, establishing groundwork for future studies to assess the relationship between diminished FHL excursion and FHL pathology.

Flexion location of the first metatarsophalangeal joint and the location of forefoot bend in general purpose women's footwear.

BACKGROUND: General purpose footwear could have a built-in flexion location which may not match the anatomical fulcrum location for an individual's foot. Mismatched fulcra impact on joint function, and may delay healing of an injured first metatarsophalangeal joint (first MP joint). This study compared the location of the first MP joint in an asymptomatic sample of the South African female population to the bend location set within the lasts (used by footwear manufacturers) to find whether mismatches of the flexion locations of the joint to the bending location of the footwear were likely. METHODS: The study used a three dimensional foot measurement database of 453 female participants to find the fulcrum location of the first MP joint. The distance between the heel and the first MP joint was expressed as a percentage of the overall length of the unshod foot. Similar measures for sandals and closed shoes were derived, and all were compared to manufacturer last data. RESULTS: The location of first MP joint ranged from 70% to 79% of total foot length, significantly different from last design specifications of 63% or 66% (p<0.0001). The range of first MP joint fulcrum locations in the same size feet occurred in a wide 24mm mediolateral band under the forefoot, termed a flexion zone. CONCLUSIONS: The first MP joint cannot properly function as a fulcrum unless footwear has a matching flexion location. Footwear designs should incorporate a wide flexion zone located under the forefoot to permit the range of first MP joint flexion locations. Recommendations to patients are to select appropriate flexible footwear to prevent shear forces, reduce strain, prevent injury and enable range of motion function and healing of injury.

Metatarsophalangeal joint flexion affects dorsiflexor activity in subjects with a dominant extensor hallucis longus.

BACKGROUND AND OBJECTIVES: Normal dorsiflexion (DF) required for normal gait is achieved through balance of the tibialis anterior (TA) and extensor hallucis longus (EHL). Imbalance may induce ankle and foot deformities and exacerbate pathology. EHL dominance is associated with progressive TA weakness, attributable to muscle non-use. When the EHL dominantly dorsiflexes the ankle, the big toe extends at the metatarsophalangeal joint (MTPJ) and pure ankle DF is absent. The effects of active MTPJ flexion on TA and EHL muscles, TA/EHL ratio, and the force applied during active DF in EHL-dominant (EHL-D) and EHL-non-dominant (EHL-ND) subjects were compared. METHODS: The 38 subjects were divided into EHL-D and EHL-ND groups. All subjects performed active ankle DF with and without active MTPJ flexion. Surface electromyographic data, ankle active range of motion, and DF force were measured. Two-way mixed analysis of variance was used to evaluate differences in dependent variables. RESULTS: Compared to the EHL-ND group, the EHL-D group exhibited less TA activity, more EHL activity, and a reduced TA/EHL activity ratio. Active application of MTPJ flexion during DF significantly reduced muscle imbalance, whereas EHL activity decreased and the TA/EHL activity ratio increased. The DF force decreased significantly with MTPJ flexion in both groups. CONCLUSIONS: Active MTPJ flexion can reduce EHL and/or increase TA activity and increase the TA/EHL activity ratio during active ankle DF in both EHL-D and EHL-ND subjects.