Foot asymmetry in healthy adults: elliptic fourier analysis of standardized footprints

The size and shape of paired structures differ in the left and right sides of the body. Shape characteristics should be analyzed separately from size to supply information about the normal variations of human organs. In the present study, the within-subject normal symmetry of footprint shape and size was analyzed from a mathematical standpoint. On the standardized left and right footprints of 46 healthy adults (23 women and 23 men; 19-26 years old), the outline of each foot excluding the toes was identified and its shape was quantified independently from size by the elliptic Fourier analysis. The symmetry in shape was quantified on an intra-subject basis by calculating a morphologic distance D between the mathematical reconstructions of the left and right footprints of each subject. Symmetry in size was assessed by the right-to-left area ratio and found to be very good for all subjects; it ranged from 0.948 to 1.049. The subjects were also grouped by sex, and mean values were calculated. Within-subject symmetry in the footprint shape appeared high, with morphologic distances ranging between 8.94 and 2.66 in men and between 7.15 and 3.09 in women. No consistent associations between footprint symmetry and age, body height and weight, or shoe size were found. On average, women had more symmetric size-standardized footprints than did men (women: mean 4.57, SD 1.14; men: mean 5.46, SD 1.7; p < 0.05). Mean size-independent shapes of male and female left and right footprints were also calculated. Together with the analysis of individual asymmetry, they could be used for the quantitative diagnosis of borderline patients.

Evans osteotomy in the adult foot: an anatomic study of structures at risk

The Evans osteotomy has become an important option in the surgical treatment of adult pes planus deformity of multiple causes. Despite its increasing popularity, however, no single study, to our knowledge, has thoroughly examined the structures at risk when performing the Evans osteotomy on the adult foot. We performed the Evans osteotomy on 20 adult cadaver specimens to determine which soft tissues and bony structures were endangered by the procedure. We found that the optimal Evans osteotomy site should be exactly 10 mm proximal to the calcaneocuboid joint because this location best affords the opportunity of avoiding damage to the anterior or middle subtalar facets in those specimens with separate facets. In addition, we determined that the sural nerve, peroneus longus tendon, and peroneus brevis tendon were consistently at risk during the operative approach. Regarding the medial soft tissues, we found that these structures did, in fact, consistently pass in the line of the Evans osteotomy, and so are at risk.

Muscle and tendon morphogenesis in the avian hind limb

The proper development of the musculoskeletal system in the tetrapod limb requires the coordinated development of muscle, tendon and cartilage. This paper examines the morphogenesis of muscle and tendon in the developing avian hind limb. Based on a developmental series of embryos labeled with myosin and tenascin antibodies in whole mount, an integrative description of the temporal sequence and spatial pattern of muscle and tendon morphogenesis and their relationship to cartilage throughout the chick hind limb is presented for the first time. Anatomically distinct muscles arise by the progressive segregation of muscle: differentiated myotubes first appear as a pair of dorsal and ventral muscle masses; these masses subdivide into dorsal and ventral thigh, shank and foot muscle masses; and finally these six masses segregate into individual muscles. From their initial appearance, most myotubes are precisely oriented and their pattern presages the pattern of future, individual muscles. Anatomically distinct tendons emerge from three tendon primordia associated with the major joints of the limb. Contrary to previous reports, comparison of muscle and tendon reveals that much of their morphogenesis is temporally and spatially closely associated. To test whether reciprocal muscle-tendon interactions are necessary for correct muscle-tendon patterning or whether morphogenesis of each of these tissues is autonomous, two sets of experiments were conducted: (1) tendon development was examined in muscleless limbs produced by coelomic grafting of early limb buds and (2) muscle development was analyzed in limbs where tendon had been surgically altered. These experiments demonstrate that in the avian hind limb the initial morphogenetic events, formation of tendon primordia and initial differentiation of myogenic precursors, occur autonomously with respect to one another. However, later morphogenetic events, such as subdivision of muscle masses and segregation of tendon primordia into individual tendons, do require to various degrees reciprocal interactions between muscle and tendon. The dependence of these later morphogenetic events on tissue interactions differs between different proximodistal regions of the limb.

Pelvic limb musculature in the emu Dromaius novaehollandiae (Aves: Struthioniformes: Dromaiidae): adaptations to high-speed running

Emus provide an excellent opportunity for studying sustained high-speed running by a bird. Their pelvic limb musculature is described in detail and morphological features characteristic of a cursorial lifestyle are identified. Several anatomical features of the pelvic limb reflect the emus' ability for sustained running at high speeds: (1) emus have a reduced number of toes and associated muscles, (2) emus are unique among birds in having a M. gastrocnemius, the most powerful muscle in the shank, that has four muscle bellies, not the usual three, and (3) contribution to total body mass of the pelvic limb muscles of emus is similar to that of the flight muscles of flying birds, whereas the pelvic limb muscles of flying birds constitute a much smaller proportion of total body mass. Generally, the pelvic limb musculature of emus resembles that of other ratites with the notable exception of M. gastrocnemius. The presence and arrangement of four muscle bellies may increase the effectiveness of M. gastrocnemius and other muscles during cursorial locomotion by moving the limb in a cranio-caudal rather than a latero-medial plane.

Magnetic resonance imaging of the peroneal tendons

Injuries of the peroneal tendons include tendinosis, tenosynovitis, tears, and dislocation. These injuries are being detected with greater frequency since the advent of MRI. After a review of the normal MRI anatomy of the peroneal tendons, this article will focus on the MR features of peroneal tendon disorders in the foot and ankle.

Normal variants and pitfalls in magnetic resonance imaging of the ankle and foot

Distinction of normal from disease is one of the principal tenets in magnetic resonance imaging (MRI) interpretation of the foot and ankle. Therefore, familiarity with normal anatomic variants and pitfalls in the foot and ankle is crucial for accurate diagnostic analysis of MR images. This article will focus on outlining variants and MRI interpretation pitfalls of the tendons, muscles, bones, ligaments, and other miscellaneous structures of the foot and ankle.

Instrumentation considerations of a clinical and a computerized technique for the measurement of foot angles

Measurement of the foot angles either directly from the patient, from video images, or from radiographs is integral to podiatric clinical practice to confirm diagnoses and to plan, prescribe, and monitor treatment protocols. The reliability, precision, and accuracy involved in any measured value limits the validity and usefulness of the measurement to optimal patient management. Studies are described that ensured the accuracy and validity of the standard clinical tool, the universal goniometer (UG), by applying a calibration protocol. These same calibration angles were then measured by a computer-assisted human movement analysis system, the Ariel Performance Analysis System (APAS). The APAS was found to overestimate consistently the UG angular measures by less than 1 degree and this amount of error was considered clinically irrelevant. The angular results obtained by a clinician and a technician using the APAS on two separate days were tested and were found to be comparable and reliable to within 1 degree, and thus the analysis was deemed to be of excellent reliability and precision. The study found that clinicians could establish the accuracy and validity of their instruments by means of simple calibration, and that computer measures could be repeated on patients by a clinical or a technician. The simple calibration procedure described will assist the clinician to ensure that the measures obtained in the clinical setting have minimal measurement error and that the values can be confidently used to make decisions and draw clinical inferences.

Geometric models that classify structural variations of the foot

The author presents a description of three geometric models to serve as a framework for establishing a numerical classification system of unlimited refinement for structural variations of the foot and foot types. Such a classification system may identify different forms (foot types) that may be closely aligned to complex movements of the foot (dynamic foot function). This may help in the diagnosis and treatment of biomechanical disabilities. Clinical evaluations are based on radiographic landmark data from weightbearing radiographs.

The reliability of three techniques for measuring foot position

The reliability of three commonly used techniques for measuring foot position--valgus index, navicular height, and arch height--was evaluated in a study involving 20 healthy subjects. The results demonstrated significant differences (P < .05) between two observers for all three techniques, although there were no significant differences between two visits for the same observer (P < .05). Secondary analysis demonstrated that navicular height yielded the highest degree of intraobserver and interobserver agreement. The results suggest that there is a wide variation in foot position in the general population, and that measurement error may result from difficulties in defining foot position, techniques used, and instrumentation.

Changes in Achilles tendon moment arm from rest to maximum isometric plantarflexion: in vivo observations in man

1. The purpose of the present study was to examine the effect of a plantarflexor maximum voluntary contraction (MVC) on Achilles tendon moment arm length. 2. Sagittal magnetic resonance (MR) images of the right ankle were taken in six subjects both at rest and during a plantarflexor MVC in the supine position at a knee angle of 90 deg and at ankle angles of -30 deg (dorsiflexed direction), -15 deg, 0 deg (neutral ankle position), +15 deg (plantarflexed direction), +30 deg and +45 deg. A system of mechanical stops, support triangles and velcro straps was used to secure the subject in the above positions. Location of a moving centre of rotation was calculated for ankle rotations from -30 to 0 deg, -15 to +15 deg, 0 to +30 deg and +15 to +45 deg. All instant centres of rotation were calculated both at rest and during MVC. Achilles tendon moment arms were measured at ankle angles of -15, 0, +15 and +30 deg. 3. At any given ankle angle, Achilles tendon moment arm length during MVC increased by 1-1.5 cm (22-27 %, P < 0.01) compared with rest. This was attributed to a displacement of both Achilles tendon by 0.6-1.1 cm (P < 0.01) and all instant centres of rotation by about 0.3 cm (P < 0.05) away from their corresponding resting positions. 4. The findings of this study have important implications for estimating loads in the musculoskeletal system. Substantially unrealistic Achilles tendon forces and moments generated around the ankle joint during a plantarflexor MVC would be calculated using resting Achilles tendon moment arm measurements.

Estimation of age-specific reference ranges via smoother AVAS

This paper proposes a new non-parametric procedure to estimate age-dependent reference ranges based on Tibshirani's AVAS (additivity and variance stabilization) procedure for non-parametric estimation of transformations for regression. Several examples are given to illustrate the flexibility and applicability of the proposed method; these include alkaline phosphatase in girls, and foot length and head circumference during gestation.

Functional and adaptive significance of primate pads and claws: evidence from New World anthropoids

This study tests predicted morphoclines in fingertip morphology among four small-bodied (<1 kg) New World monkeys (Saimiri sciureus, Leontopithecus rosalia, Callithrix jacchus, and Saguinus oedipus) in order to test previous functional and adaptive explanations for the evolution of flattened nails, expanded apical pads, and grasping extremities within the Order Primates. Small-bodied platyrrhines which frequently forage among small-diameter substrates are expected to possess 1) relatively expanded apical pads, 2) well-developed epidermal ridges, 3) distally broad terminal phalanges, and 4) reduced flexor and extensor tubercles compared to those species which use large-diameter arboreal supports more frequently for their locomotor and postural behaviors. Results show that as the frequency of small-branch foraging increases among taxa within this sample, relative distal phalanx breadth also increases but distal phalanx length, height, and flexor tubercle size decrease. Moreover, epidermal ridge development becomes more pronounced as the frequency of small-branch foraging increases. Terminal phalanx breadth and epidermal ridge complexity are both positively correlated with apical pad size. The large, flexible apical pad increases stability of the hand and foot on small-diameter arboreal supports because the pad can contact the substrate in several planes which, in turn, enables the pad to resist disruptive forces from different directions by friction and interlocking (Hildebrand, 1995). The observed morphoclines demonstrate that a gradient in form from claw- to nail-like tegulae exists among these taxa. Thus, the distinction between claw- and nail-bearing platyrrhines is essentially arbitrary. These observations corroborate Cartmill's (1972) functional and adaptive model for the loss of claws in primates: namely, expanded apical pads are required for habitual locomotor and postural behaviors on small-diameter supports whereas claws are more useful for positional behaviors on large-diameter substrates. Finally, results from this study support previous suggestions that the keeled tegulae of callitrichines represent a derived postural adaptation rather than a primitive retention from an ancestral eutherian condition.

Relationship between foot pressure pattern and foot type

Foot type and location of area of peak pressure under the metatarsal heads were determined for 54 healthy adults between the ages of 21 and 39 years. Feet were classified as neutral, pronated, or supinated. Each subject walked barefoot over a pedobarograph, and the area of peak pressure was identified as being either medial, central, or lateral under the metatarsal heads. A Fisher's exact test determined that there was a significant relationship between the area of peak pressure and foot type. A post hoc lambda asymmetric test showed that the relationship was very weak. Nearly half (49%) of the feet were classified as neutral, 36% were pronated, and 15% were supinated. Pressure patterns were as follows: 62% central, 26% medial, and 12% lateral. Other factors besides foot type influence the area of peak pressure under the metatarsal heads.

Arterial and lymphatic supply of the knee integuments

The surgical approach to the anterior knee region carries a risk for postoperative integument infection and skin necrosis. A hypothesis is that surgical approach may damage integumental blood supply and additionally the lymphatic drainage from the foot and leg. The goal of this study was to describe the arteries and lymphatics directly affected by the antero-medial approach. Injection of the femoral a. was used to identify the femoral and popliteal aa. and their branches distributed to the integument of the anterior, medial and lateral aspects of the knee. Lymphatic injection into the plantar aspect of the first toe was also performed to identify the subdermal lymphatics traversing the area. Our results showed that most of the blood supply arises from the medial aspect of the knee integuments. However, subcutaneous arterial anastomoses provide a significant blood-supply when there is interruption of the medial vessels as seen in the medial surgical approach to the knee. Most of the lymphatic drainage originating from the foot crosses the knee region on the medial side, opposite or below the tibial tuberosity. Because the subdermal arterial network is well-developed, the medial approach for knee surgery does not endanger the anterior knee integuments as long as the lateral vascular supply is preserved. However, this approach may interrupt the lymphatic circulation, particularly in the case of an extended incision, which could explain postoperative edema and an increased rate of wound infection.

Can we predict body height from segmental bone length measurements? A study of 3,647 children

It is well known that significant differences exist in the anthropometric data of different races and ethnic groups. This is a cross-sectional study on segmental bone length based on 3,647 Chinese children of equal sex distribution aged 3-18 years. The measurements included standing height, weight, arm span, foot length, and segmental bone length of the humerus, radius, ulna, and tibia. A normality growth chart of all the measured parameters was constructed. Statistical analysis of the results showed a very high linear correlation of height with arm span, foot length, and segmental bone lengths with a correlation coefficient of 0.96-0.99 for both sexes. No differences were found between the right and left side of all the segmental bone lengths. These Chinese children were found to have a proportional limb segmental length relative to the trunk.

An ergonomic approach to public squatting-type toilet design

This paper reports a case study on public squatting-type toilet design, which was undertaken with a special emphasis on ergonomic considerations. A field survey on the use of public toilets in Taipei reveals that almost half of the subjects take a non-sitting posture while using the sitting-type public toilets and 86% of the subjects agreed that the squatting-type public toilets better satisfy sanitary requirements. An experiment was conducted to determine relevant anthropometric data for a redesign of squatting-type toilets. One of the variables studied was the effect of the footstep slope on squatting comfort. A total of 80 subjects as tested on four footstep slopes: 0 degrees, 15 degrees, 30 degrees and 45 degrees. Their heart rates were measured before and after the test, and their subjective evaluations of squatting comfort were also recorded. The 15 degrees slope was found to be preferred. These findings were then used in design development where mock-ups were presented to subjects for evaluation, then modifications were made and further tests conducted for verification. The result shows that the ergonomic approach is feasible recommended to be adopted in the process of product design of such facilities.

Morphological diversity of the avian foot is related with the pattern of msx gene expression in the developing autopod

The formation of the digits in amniota embryos is accompanied by apoptotic cell death of the interdigital mesoderm triggered through BMP signaling. Differences in the intensity of this apoptotic process account for the establishment of the different morphological types of feet observed in amniota (i.e., free-digits, webbed digits, lobulated digits). The molecular basis accounting for the differential pattern of interdigital cell death remains uncertain since the reduction of cell death in species with webbed digits is not accompanied by a parallel reduction in the pattern of expression of bmp genes in the interdigital regions. In this study we show that the duck interdigital web mesoderm exhibits an attenuated response to both BMP-induced apoptosis and TGFbeta-induced chondrogenesis in comparison with species with free digits. The attenuated response to these signals is accompanied by a reduced pattern of expression of msx-1 and msx-2 genes. Local application of FGF in the duck interdigit expands the domain of msx-2 expression but not the domain of msx-1 expression. This change in the expression of msx-2 is followed by a parallel increase in spontaneous and exogenous BMP-induced interdigital cell death, while the chondrogenic response to TGFbetas is unchanged. The regression of AER, as deduced by the pattern of extinction of fgf-8 expression, takes place in a similar fashion in the chick and duck regardless of the differences in interdigital cell death and msx gene expression. Implantation of BMP-beads in the distal limb mesoderm induces AER regression in both the chick and duck. This finding suggests an additional role for BMPs in the physiological regression of the AER. It is proposed that the formation of webbed vs free-digit feet in amniota results from a premature differentiation of the interdigital mesoderm into connective tissue caused by a reduced expression of msx genes in the developing autopod.

The effect of foot structure on the three-dimensional kinematic coupling behavior of the leg and rear foot

BACKGROUND AND PURPOSE

Differences in foot structures have been reported to account for the large variability in findings in previous studies that have examined the relationship between foot structure and the interdependent rotations of the lower extremity. The purpose of this study was to determine, in individuals with radiographically distinct foot structures, the effect of foot structure on three-dimensional kinematic behavior of the leg and rear foot during running.

SUBJECTS AND METHODS

Based on radiographic measurements, 10 recreational runners were assigned to a low rear-foot group and another 10 recreational runners were assigned to a high rear-foot group. Three-dimensional kinematic data were collected during treadmill running. Individual axis rotations and the "coupled" relationship between the leg and rear-foot segments were defined using a Cardan angle system of three ordered rotations.

RESULTS

The predominant rotations suggest a combined subtalar and talocalcaneal joint axis to favor calcaneal eversion and inversion for the low rear-foot group and tibial medial and lateral rotation for the high rear-foot group. Group differences were also found for the coupling ratio, which described the proportion of calcaneal eversion and inversion transferred or coupled to tibial axial rotation.

CONCLUSION AND DISCUSSION

The rotational patterns and coupling response unique to each foot group may enhance our understanding of lower-extremity injuries related to certain foot structures. An assessment of the coupling relationship in combination with traditional frontal-plane measurements may better guide decisions regarding selection of footwear and orthoses.

MR imaging of the foot: anatomy and pathology

MR imaging has become a valuable tool in the diagnosis of pathologic conditions of the foot. The direct multiplanar imaging capability, superior soft tissue contrast discrimination, and spatial resolution afforded by MR are advantages over other imaging modalities. The complex anatomy and spectrum of pathology in this region present a significant challenge to the radiologist. Familiarity with the anatomy, various clinical conditions, and their appearance on MR imaging is essential for accurate diagnosis. In this article, a limited review of the anatomy of the foot is presented together with a more in-depth discussion and illustration of a wide variety of pathologic conditions of the foot. Emphasis is placed on those conditions that are relatively unique to the foot.

MRI of plantar fasciitis

At present, MRI is the only imaging method that can precisely visualize lesions of the superficial plantar aponeurosis, whether they be musculoaponeurositides, enthesopathies or tears, and whether they be acute or chronic, with or without complications. By its direct visualization of the lesion, MRI enables an accurate assessment of the injury to be made and thereby better orients the therapeutic strategy.

Aging and time to instability in posture

Two experiments are reported that were set up to examine the spatial-temporal boundaries of postural instability in upright stance as a function of age (60-96 years) and postural conditions. Subjects stood on a force platform under different experimental conditions (vision/no vision and arms up/down) so that the effect of age on key dynamic properties of postural stability could be determined. The findings showed that the ratio of the area of the motion of the center of pressure to the area within the stability boundary increased with age. Also, the virtual time-to-contact with the postural stability boundary decreased with age. Collectively, the findings show that the margins to the spatial-temporal boundaries of postural stability decrease with advancing age in the elderly. These reduced margins of dynamic stability may be a factor contributing to the progressive instability of posture with aging in the elderly.

Selectivity of superficial vein occlusion at the ankle and calf level: a methodological study in healthy volunteers

Judgement of deep venous function may be necessary before surgery for superficial vein incompetence is performed. Assessment of deep venous function needs selective entrapment of superficial venous compartments between the ankle and knee, which may not be guaranteed if conventional tourniquets are used. This study was, therefore, aimed at modifying the technique of selective compression of superficial vein compartments. Twenty apparently normal legs of 10 volunteers were investigated on two study days. The subjects were in a supine position with the feet resting 30 cm above heart level. Ankle cuffs (3 cm wide) were placed just above the malleoli and stepwise inflated with air. The steady-state venous volume of the forefoot as a function of the pressure within the ankle cuff was measured with a mercury-in-rubber strain gauge. The maximum venous outflow velocity from the foot was also measured at each cuff pressure step after the addition of conventional thigh vein occlusion. The same protocol was used on the second study day: calf cuffs (3 cm wide) were then used instead of the ankle cuffs. In the forefoot, venous volume increased and the maximum venous outflow velocity decreased significantly either at ankle cuff pressures > 30 mmHg or at calf cuff pressures of > 60 mmHg. By using small cuffs, selective superficial vein occlusion seems to occur at cuff pressures ranging between 10 and 30 mmHg (ankle) and between 30 and 60 mmHg (calf), provided the feet are 30 cm above heart level. Higher cuff pressures seem to interact with deep venous function.

Factors associated with ankle injuries. Preventive measures

A sense of foot position in humans is precise when barefoot, but is distorted by athletic footwear, which accounts for the high frequency of ankle sprains in shod athletes. It is unclear whether taping and rigid and semi-rigid devices protect against ankle sprains, as all of the studies suggesting this are flawed by inadequate controls. If these devices do protect the ankle, it is not through added support but rather through a partial correction of the deceased foot position awareness caused by footwear. Since taping and rigid and semi-rigid devices interfere with normal movement, there is concern that these might actually increase the frequency of injury at the ankle and/or at different locations. In this respect, taping is less of a concern because it interferes least with normal movement. The best solution for reducing ankle sprains in shod athletes is the use of more advanced footwear to retain maximal tactile sensitivity, thereby maintaining an awareness of foot position comparable to that of the barefoot state or perhaps even improving on it.