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The individual elements of the vertebrate skeleton are separated by three different types of joints, fibrous, cartilaginous and synovial joints. Synovial joint formation in the limbs is coupled to the formation of the prechondrogenic condensations, which precede the formation of the joint interzone. We are beginning to understand the signals involved in the formation of prechondrogenic condensations and the subsequent differentiation of cells within the condensations into chondrocytes. However, relatively little is known about the molecules and molecular pathways involved in induction of the early joint interzone and the subsequent formation of the synovial joints. Based on gain-of function studies Wnt-signalling, in particular the canonical pathway, has been implicated in the joint induction process. Here we provide genetic evidence from loss-of function analysis of embryos lacking either the central player of the canonical Wnt-pathway, beta-catenin, in the limb mesenchyme or the two ligands, Wnt9a and Wnt4, demonstrating that canonical Wnt-signalling plays an important role in suppressing the chondrogenic potential of cells in the joint thereby actively allowing joint formation. Furthermore our data show that the beta-catenin activity is not essential for the induction of molecular markers expressed in the joint interzone. Thus, suggesting that canonical Wnt-signalling is not required for the induction, but for the subsequent maintenance of the fate of the joint interzone cells.

Reasons for Performing Study: There is little information available about conformational changes in the forelimbs of growing foals., Objectives: To describe the conformation of the carpus and fetlock of Thoroughbred foals from birth to yearling sale age., Methods: Subjective assessments of the fetlock and carpal conformation of 119 Thoroughbred foals were made within the first month of life and then at 30 day intervals until at least age 120 days. At least 70 subjects were examined further at 60 day intervals until September of their second year. Conformation grades are reported for 5 age groups: first 7 days and at a mean of 46, 176, 362 and 525 days. The conformation of all available sires and dams of subjects was also graded., Results: All subjects demonstrated carpal deviations, such as valgus, outward rotation and offset, and approximately 30% had fetlock deviations. Heavier birth weights were associated with carpal offset and fetlock inward conformation at most ages, and heavier yearlings were more likely to be carpal valgus. The carpal conformation of the sire (offset and outward rotation) was associated with similar yearling carpal conformation. During the study period, the carpal conformation of Thoroughbred foals became less valgus and more offset. Fetlock conformation became more inwardly deviated during the first 6 months of the study., Conclusions: Carpal and fetlock conformation change greatly in Thoroughbred foals up to age 18 months. The phenotype of the sire can be associated with yearling carpal conformation and bodyweight, particularly at birth and as yearlings, is associated with yearling fetlock and carpal conformation., Potential Relevance: New factors associated with forelimb conformational deviations have been identified that may help breeders better to manage young racing stock.

Reasons for Performing Study: The tarsal joint is a frequent site of lameness, but little objective information is available regarding the effects of tarsal conformation on joint movements or forces., Objective: To compare tarsal kinematics and kinetics in horses with large, intermediate and small tarsal angles., Methods: Sagittal plane standing angle of the right tarsal joint was measured in 16 horses as they stood squarely with the hind hooves vertically beneath the hip joint. Tarsal angles were classified as small (< 155.5 degrees), intermediate (155.5-165.5 degrees) or large (> 165.5 degrees). Reflective markers, attached over the centres of joint rotation, were tracked during stance as the horses trotted across a force plate at a standardised speed. Joint angles and ground reaction forces were combined with morphometric data to calculate net joint moments and net joint powers across the tarsus using inverse dynamics., Results: In all horses, the tarsus flexed during the impact phase and extended in late stance. Tarsal angles were stratified according to standing tarsal angle throughout stance. Horses with large standing angles showed less flexion and less energy absorption at the tarsus during the impact phase than those with intermediate or small angles and generated less vertical impulse than horses with small standing angles. Net extensor moment at the tarsus during stance was lower for horses with large standing angles., Conclusions: In horses with large tarsal angles, less concussion was absorbed during the impact phase, which may be a factor in the development of degenerative joint disease; and the smaller vertical impulse and extensor moment later in stance may limit propulsive ability. However, the smaller net joint moment may reduce the risk of plantar ligament desmitis., Clinical Significance: The effects of conformation on kinematics and kinetics of the tarsal joint may influence both performance and soundness.

The first tarsometatarsal (TMT) joint has a complex role in regulating joint pressure in the midfoot. Despite its importance, there have been only a few studies of the functional morphology and biomechanical function of this joint. Here we report about the densitometric pattern of the subchondral bone layer of the articulating elements of the human first TMT joint. We studied dry bones of the first metatarsal and medial cuneiform bones in 64 human cadavers to establish the pattern of the density distribution and to correlate it with the biomechanical function of the joint. The articular surfaces of both the bones were analyzed planimetrically. Half of the specimens (n=32) were sectioned in the sagittal plane and the other 32 articulations were in the transverse plane. In all the sections, the subchondral bone density of the first TMT joint was measured. We found that in sagittal slices the dorsal area of the lateral parts and intermediate parts in females and the dorsal area of the lateral parts, the medial parts and intermediate parts in males were denser than the plantar area and that its density decreased towards the plantar area. The dorsal parts of transverse slices in males were the densest and its density decreased towards the plantar part. In the dorsal, middle and plantar parts in females in transverse slices, the lateral and intermediate areas were denser than the medial areas (P<0.05). There was no significant difference between the bone densities of females and males.

Magnetic resonance (MR) images of the right tarsal joint of 22 normal male Han:Wistar rats were acquired using a 4.7 T magnet. An intermediate-high signal area associated with the tendon of the flexor hallus longus muscle was noticed in three rats on T2-weighted images. These areas appeared as an intermediate-high signal on lightly T2-weighted images, but appeared as an iso-signal to muscle structure on proton density weighted images. Histology preparations showed that such areas were caused by a sizable fluid collection within the synovial sheath of the tendon of the flexor hallus longus muscle, with all other joint structures appearing normal. This anatomic variant could be potentially regarded as a lesion on T2-weighted MR images, such as inflamed tissue with oedema, especially when the spatial resolution and/or signal-to-noise ratio are not optimal.

Reasons for Performing Study: Osteoarthritis (OA) is a common cause of distal tarsal pain, but disease development is poorly understood. Awareness of normal tarsal structure and function is important in order to understand the pathogenesis of OA. Thickening of the subchondral bone (SCB) plate has been related to the development of OA, but SCB plate patterns in the equine tarsus have not been documented., Hypotheses: There is a repeatable pattern of SCB thickness across the distal tarsal joints, and specifically that thickness would be greatest dorsally and laterally., Methods: Twenty cadaver tarsi were collected from mature horses that had undertaken low-level exercise only with no history of hindlimb lameness. Magnetic resonance images were acquired using a high-resolution sagittal 3-dimensional T1-weighted spoiled gradient echo sequence. Subchondral bone thickness was measured on sagittal images at dorsal and plantar locations on the proximal and distal aspects of the central (CT) and third (T3) tarsal bones and proximal aspect of the third metatarsal bone (Mt3)., Results: On the proximal aspect of CT, medial and lateral SCB thickness were significantly greater than midline. On the distal aspect of CT and T3 and proximal Mt3, lateral SCB thickness was significantly greater than medial and midline sites. Dorsal SCB thickness was greatest on the proximal and distal aspects of CT and proximal Mt3. Subchondral bone accounted for a greater proportion of CT and T3 on the dorsal aspect than the plantar., Conclusions: There is a repeatable pattern of SCB thickness in the distal tarsal bones of horses with no history of hindlimb lameness. This reflects the pattern of loading across the joints., Potential Relevance: This study provides evidence of a consistent osteochondral pattern in the equine tarsus for reference in identification of osteoarticular pathologies.

The navicular bone, located in the midfoot, articulates with the head of the talus, cuboid, and the three cuneiform bones that are involved in the acetabulum pedis. It gives attachment to the spring ligament (superomedial and inferior calcaneonavicular ligament)that can be injured in a failure of the posterior tibialis tendon and cause an adult acquired flatfoot deformity. The navicular bone provides insertion for the posterior tibialis tendon. Some pathologies can be related to the presence of an accessory navicular bone. Osteonecrosis or stress fractures can affect the navicular bone because of its poor vascularization, especially in its central portion.

The transverse tarsal plays a critical role in allowing the foot to transition from a flexible structure that dissipates impact as the foot strikes the ground and accepts the body's weight to the rigid structure that is required for efficient propulsion during toe off.Similarly, the medial longitudinal arch of the foot is controlled by the supportive structures of the talonavicular joint. A fine balance exists between muscular control and static support structures of the talonavicular joint. Failure of one support structure is often followed by fatigue of the remaining support and loss of function of the entire joint complex. This article describes the osseous and ligamentous anatomy of the talonavicular and calcaneocuboid joints and describes the biomechanical role of the transverse tarsal joint in standing and gait. Biomechanical principles are used to illustrate orthotic management of diseases that affect the transverse tarsal joint.

Tendon ossification in the crus and tarsometatarsal regions of cranes makes ultrasonography difficult everywhere except for joints, where ossification is absent. Normal ultrasonographic anatomy of the adult Florida sandhill crane (Grus canadensis pratensis) intertarsal joint is described on the basis of ultrasonography that was performed on the limbs of a cadaver, which were dissected and cross-sectioned subsequently, to correlate ultrasonographic images with anatomic structures. Intertarsal joints of five normal sandhill cranes and two cranes with known intertarsal abnormalities were then imaged bilaterally in transverse and sagittal planes. Ultrasonographic imaging can be used to evaluate the soft-tissue structures on the dorsal and plantar aspects of the intertarsal joint of cranes, and it is a useful adjunct to physical and radiographic examination for localizing injuries to this area.

Bush crickets have long, thin hind legs but jump and kick rapidly. The mechanisms underlying these fast movements were analysed by correlating the activity of femoral muscles in a hind leg with the movements of the legs and body captured in high-speed images. A female Pholidoptera griseoaptera weighing 600 mg can jump a horizontal distance of 300 mm from a takeoff angle of 34 degrees and at a velocity of 2.1 m s(-1), gaining 1350 microJ of kinetic energy. The body is accelerated at up to 114 m s(-2), and the tibiae of the hind legs extend fully within 30 ms at maximal rotational velocities of 13500 deg. s(-1). Such performance requires a minimal power output of 40 mW. Ruddering movements of the hind legs may contribute to the stability of the body once the insect is airborne. During kicking, a hind tibia is extended completely within 10 ms with rotational velocities three times higher at 41800 deg. s(-1). Before a kick, high-speed images show no distortions of the hind femoro-tibial joints or of the small semi-lunar groove in the distal femur. Both kicks and jumps can be generated without full flexion of the hind tibiae. Some kicks involve a brief, 40-90 ms, period of co-contraction between the extensor and flexor tibiae muscles, but others can be generated by contraction of the extensor without a preceding co-contraction with the flexor. In the latter kicks, the initial flexion of the tibia is generated by a burst of flexor spikes, which then stop before spikes occur in the fast extensor tibiae (FETi) motor neuron. The rapid extension of the tibia can follow directly upon these spikes or can be delayed by as long as 40 ms. The velocity of tibial movement is positively correlated with the number of FETi spikes. The hind legs are 1.5 times longer than the body and more than four times longer than the front legs. The mechanical advantage of the hind leg flexor muscle over the extensor is greater at flexed joint angles and is enhanced by a pad of tissue on its tendon that slides over a protuberance in the ventral wall of the distal femur. The balance of forces in the extensor and flexor muscles, coupled with their changing lever ratio at different joint positions, appears to determine the point of tibial release and to enable rapid movements without an obligatory co-contraction of the two muscles.

Objective: To assess the frequency of malalignment in the 1st, 2nd and 3rd tarso-metatarsal joints (Lisfranc joint) in cadaveric specimen and asymptomatic individuals utilizing oblique axial MR images., Design and Patients: Four fresh frozen cadaveric feet were dissected in the oblique axial plane at 5 mm slice thickness. Thirty MR studies in 29 patients who had no history of pain, trauma or surgery at the tarso-metatarsal area were included in our study. The 1st to 3rd tarso-metatarsal joints were evaluated on the MR studies and cadaveric slices by two musculoskeletal radiologists for (1) the presence of a medial and/or lateral step-off and (2) articular surface divergence., Results: In the cadaveric dissections there were lateral step-offs in the 1st ( n=3) and in the 2nd ray ( n=3) respectively. No joint incongruity was evidenced. The MR studies in the patients population depicted 28 step-offs (9 medial, 19 lateral) in the 1st ray, 16 (2 medial, 14 lateral) in the 2nd ray and two in the 3rd ray. Joint incongruity was present in the 2nd ray ( n=6) and in the 3rd ray ( n=12). All the above findings were limited to a few images., Conclusions: Isolated joint malalignment with otherwise normal findings (no ligamentous injury, no fracture and no bone marrow edema) might reflect normal anatomic features at the tarso-metatarsal joints and must be interpreted carefully.

Purpose: To develop a technique for dynamic magnetic resonance imaging (MRI) of joint motion based on a combination of real-time TrueFISP (fast imaging with steady state precession) imaging with surface radiofrequency (RF) coils., Materials and Methods: The metacarpal, elbow, tarsal, and knee joint of five volunteers and the knees of four patients were examined with a real-time TrueFISP sequence during movement of the joints., Results: All examined joints could be assessed under dynamic conditions with high image contrast and high temporal resolution., Conclusion: Dynamic MRI of joints with TrueFISP is feasible and can provide information supplemental to static joint examinations., (Copyright 2002 Wiley-Liss, Inc.)

Alterations of ankle cartilage are observed in degenerative and inflammatory joint disease, but cartilage cannot be directly visualized by radiography. The purpose of this study was therefore to analyze the feasibility and precision of quantitative cartilage imaging in the human hind foot (talocrural, talotarsal, and intertarsal joints), and to report the inter-subject variability for cartilage volume, thickness and surface areas. The feet of 16 healthy volunteers were imaged using a 3D gradient-echo magnetic resonance imaging sequence with water-excitation. After interpolation to a resolution of 1 x 0.125 x 0.125 mm3 the cartilage plates were segmented, and the cartilage volume, thickness, and surface areas determined. The precision (four repeated measurements) was examined in eight volunteers, the RMS average CV% being 2.1% to 10.9% in single joint surfaces, and < or = 3% for the cumulative values of all joints. The mean cartilage thickness ranged from 0.57+/-0.08 (navicular surface) to 0.89+/-0.19 mm (trochlear surface for tibia). In conclusion this study shows that it is feasible to quantify thin cartilage layers in the hind foot under in vivo imaging conditions, and that the precision errors are substantially smaller than the inter-subject variability in healthy subjects.

Purpose: To describe the normal magnetic resonance (MR) imaging-depicted anatomy of the intermetatarsal spaces, with emphasis on the MR imaging appearance of the intermetatarsal bursae, and to correlate the MR findings with those seen in anatomic sections and at histopathologic analysis., Materials and Methods: Conventional radiography and pre- and postcontrast T1-weighted and fat-saturated T1-weighted spin-echo MR imaging were performed in 32 intermetatarsal spaces in eight human cadaveric feet. The cadaveric specimens were sectioned in planes corresponding to those at MR imaging for anatomic correlation. The intermetatarsal space anatomy was analyzed. Histopathologic examinations of the bursae were performed., Results: The intermetatarsal spaces were located in the forefoot between two metatarsal heads, below and above the deep transverse metatarsal ligament (DTML) that separated the spaces into two levels. The superior level contained the synovial bursa, the plantar and dorsal interosseous muscles and tendons, and the collateral ligament complexes of the metatarsophalangeal joints. The inferior level contained lumbrical muscles and neurovascular bundles. The bursae extended distally to the DTML in the second and third spaces close to the neurovascular bundles and did not extend beyond the DTML in the first and fourth spaces. In the first intermetatarsal space, the bursa had a specific appearance as it coursed along the adductor hallucis tendon as a tendon sheath. Histopathologic examination of the bursae revealed a single layer of attenuated cells., Conclusion: MR bursography provided detailed information about the intermetatarsal anatomy, especially the intermetatarsal bursae.

Injuries to the midtarsal joints are relatively uncommon and often unrecognized entities. Acute and chronic instability patterns to the calcaneocuboid joint can occur from such injuries. No previous determinations of normal calcaneocuboid laxity have been reported. Utilizing a previously described technique, stress radiographs were performed in human cadaveric specimens following serial sectioning of the ligamentous supports of the calcaneocuboid joint. Significant differences in calcaneocuboid gap and angle occurred between unstressed and stressed conditions. Cadaveric specimen testing determined that the dorsal and plantar calcaneocuboid ligaments both provide significant contributions to joint stability. Prior to defining pathologic states of joint laxity, normal ranges of stability must be determined. By more clearly defining normal stability of the calcaneocuboid joint and its ligamentous contributions, greater insight into the diagnosis and treatment of calcaneocuboid instability can be obtained.

Orthotic devices are an effective method of treating degenerative arthrosis of the foot and ankle. When combined with appropriate medications and activity modifications, operative intervention may be postponed or rendered unnecessary. A thorough comprehension of relevant anatomy, biomechanics, and available devices is crucial to maximize the benefits of this modality.

The foot is constituted from a series of small bones making a segmented structure with multiple joints, likened to a dome, in contact with the ground in three points: posteriorly the calcanear tuberosity; anteriorly and medially the head of 1st metatarsum, and anteriorly and laterally the head of 5th metatarsum. In fact, each foot presents a semi-arch whose base is represented by the lateral border and the summit by the medial border of the foot. The foot has been likened to a half-dome, so that when the medial borders of the two feet are placed together, a complete dome is formed. In the foot are present two longitudinal arches: the medial consists of the calcaneus, the talus, the navicular, the three cuneiform bones and the first three metatarsal bones. It is more arcuated and elastic then the lateral, that consist of the calcaneus, the cuboid and the 4th and 5th metatarsus. This is flattened and in contact with the ground. We can identify two transverse arches between longitudinal arches, extending from the medial to the lateral borders of the foot: the first is a lancet dome, between midfoot and forefoot, at the tarsometatarsal joint level; it consists of the bases of the metatarsal bones and the cuboid and the three cuneiform bones; the second is at flat dome, in correspondence of forefoot, at the metatarsophalangeal joint level; it consists of the bases of the proximal phalanges of the fingers and the head of five metatarsal bones. Longitudinal and transversal arches are supported from: the shape of stones of the structure (foot bones); the long and short plantar ligaments, larger and stronger than the dorsal ligaments, tie together the lower edges of the bones; a beam (the plantar aponeurosis and the plantar muscles and tendons) connecting the ends of the bridge effectively prevents separation of the pillars and consequent sagging of the arch; the maintenance of the arch depends on multiple support (ligaments, tendons of extrinsic muscles of the foot) suspending the arch from a cable above the level of the bridge. In this manner, we obtain a "functional unit" with two important aims: to support the body weight (static foot), and to serve as a lever to propel the bodies forward in walking and running (dinamic foot). Imaging techniques are able to provide further data on functional anatomy of the foot; in particular, these techniques show the bones structures, ligaments, muscles and tendons, taking part to the arch setting. Routine x-ray examinations precise information about the bone-shape and their relationship. The short and long ligaments, the tendons and the suspending the arch from above are instead successfully valuable using ultrasonography, CT and MR.

Joint and soft-tissue aspiration and injection procedures are relatively easy to master once the physician has acquired an understanding of the techniques and subtleties of performing these procedures at certain sites. These techniques can be used to diagnose and treat many painful joint and soft-tissue conditions and are useful additions to the primary care physician's treatment repertoire.

In selected patients, fusion of the talonavicular joint can be an effective treatment of adult flatfoot deformity. Restriction of motion and altered hindfoot mechanics, however, are a consequence of talonavicular fusion and can lead to accelerated arthrosis of adjacent joints. In patients with severe long-standing deformity, medial displacement calcaneal osteotomy may be a necessary adjunct to talonavicular fusion for adequate correction of heel valgus.

Objectives: To define the anatomy and mechanical properties of two ligaments stabilizing the medial tarsometatarsal joints: the Lisfranc ligament and the dorsal cuneometatarsal ligament., Design: Cadaveric study in normal feet., Setting: Biomechanics laboratory., Patients or Participants: Twelve fresh-frozen cadaveric feet were studied., Intervention: The Lisfranc and dorsal cuneometatarsal ligaments were dissected, dimensions measured, and material properties determined with a servohydraulic MTS machine on bone-ligament-bone preparations., Main Outcome Measurements: Stiffness, strain, stress, modulus, failure load, ligament length, width, thickness, and cross-sectional area were determined., Results: Dorsal ligament stiffness was 66.3+/-18.3 newtons per millimeter and the Lisfranc ligament stiffness was 189.7+/-57.2 newtons per millimeter. The failure load of the dorsal ligament averaged 150.7+/-33.1 newtons and for the Lisfranc ligament, 368.8+/-126.8 newtons., Conclusions: The stiffness and load to failure of the dorsal cuneometatarsal ligament were much higher than anticipated, which indicates that it contributes significantly to stabilizing the second metatarsal to the first cuneiform.

Ultrasonographic examination of the tarsus was performed on four clinically and radiographically normal limbs of adult horses. Particular attention was paid to the articular cartilage surfaces of the trochlear ridges of the talus and the distal intermediate ridge of the tibia. Two separate measurements of articular cartilage thickness were acquired from a longitudinal view at each site. Anatomy was confirmed with post mortem dissection. Ultrasonography was found to be a practical method for imaging the articular cartilage over the trochlear ridges of the talus and distal intermediate ridge of the tibia. The cartilage appeared as a hypoechoic band overlying the hyperechoic subchondral bone. The mean cartilage thickness over the lateral and medial trochlear ridges of the talus and the distal intermediate ridge of the tibia were 0.57 mm, 0.58 mm and 0.7 mm respectively. These measurements may have value for comparison to thickened cartilage and lesions of osteochondrosis and abnormally thinned cartilage of osteoarthritis. Ultrasound examination was not helpful in evaluating the proximal and distal intertarsal and tarsometatarsal joints, the close proximity of the articular surfaces obscured visualization of the articular cartilage.

High resolution MRI was performed on four cadaveric foot specimens of human feet to demonstrate the ligaments of the tarsal joints. Spin echo T1 images were obtained using a local gradient coil that produces 6 G/cm and 100 A in all three axes. The best views for each of the individual ligaments were determined. High resolution MRI potentially can demonstrate most of the intertarsal ligaments.

The purpose of this work is to study the architecture of the rearfoot using in vivo MR image data. Each data set used in this study is made of sixty sagittal slices of the foot acquired in a 1.5-T commercial GE MR system. We use the live-wire method to delineate boundaries and form the surfaces of the bones. In the first part of this work, we describe a new method to characterize the three-dimensional (3-D) relationships of four bones of the peritalar complex and apply this description technique to data sets from ten normal subjects and from seven pathological cases. In the second part, we propose a procedure to classify feet, based on the values of these new architectural parameters. We conclude that this noninvasive method offers a unique tool to characterize the 3-D architecture of the feet in live patients, based on a set of new architectural parameters. This can be integrated into a set of tools to improve diagnosis and treatment of foot malformations.

Background: The human foot is often modelled as a rigid body in gait analysis. A more realistic model separates this segment into a forefoot and rearfoot. However, no three-dimensional data has been published on dynamic relative ab-adduction between these segments, and how this impacts changes in foot shape., Objective: The purpose was to quantify three-dimensionally forefoot ab-adduction relative to the rearfoot in vitro, and to determine how forefoot ab-adduction affects foot length., Methods: Video data were collected from reflective marker triads affixed to the ends of Steinmann pins drilled into the tibia, calcaneus, cuboid, and the first and fifth metatarsal bones. Medial and lateral foot length and forefoot ab-adduction relative to the rearfoot were calculated under two axial tibial loads (200 N, 600 N) and two input motions (dorsi-plantarflexion, internal-external tibial rotation)., Results: It was found that patterns of change for each variable were dependent on the degree of rigidity of the foot. Relative forefoot ab-adduction values ranged from 4.4 degrees of adduction to 1.7 degrees of abduction. Medial foot length values changed +/- 0.8 mm (+/- 0.5%) and lateral foot length values changed +/- 0.5 mm (+/- 0.3%). Medial foot length was correlated positively with relative forefoot abduction, and external tibial rotation was correlated positively with relative forefoot adduction.

The surface area, thickness, and composition of the articular cartilage of the peroneocuboid articulation and the location of the synovium were investigated in 15 cadaver foot specimens. The articulations of the medial side of the peroneus longus tendon and lateral side of the cuboid were covered with fibrous and hyaline cartilages, respectively. On the lateral tuberosity of the cuboid, there is a facet that has 79.37+/-20.24 mm2 articular cartilage area with an oval shape to conform to that of the articular surface of the peroneus longus tendon (articular cartilage area, 67.35+/-28.53 mm2) with which it articulates. The mean thickness of the articular cartilage of the peroneus longus tendon and cuboid was 0.34+/-0.08 and 0.52+/-0.07 mm, respectively. The peroneocuboid joint has its own joint capsule. The synovial cavity does not communicate with the sheath of the peroneus longus tendon. Synovial membranes were attached to the margins of the articular surfaces of the cuboid immediately peripheral to the cartilage region.

The authors describe a previously unreported anatomical structure in the calcaneocuboid joint of the foot and discuss the clinical significance. Fibroadipose synovial folds or labra are present in different locations throughout the calcaneocuboid joint of the foot. They appear to be wedge-shaped infections attached to the joint capsule in areas of incongruent joint spaces. Their surface is covered with synovial cells with a highly vascular loose connective tissue sublayer. Nerve fibers were seen in association with the joint capsule, but not within the V-shaped labrum. The clinical significance of the presence of the labrum is discussed, but their function is uncertain. These structures can project up to half the joint distance and have the possibility of producing impingement syndromes, or even tears. Since they are covered with two to three layers of synoviocytes, they also have the ability to produce a synovitis. The labrum can be identified using MRI, and once their presence is known arthroscopic repair of these structures is theoretically possible.

Intrinsic material properties and histomorphometry of freshly frozen, human cadaveric cartilage from the second metatarsal intermediate cuneiform (SMIC) articulation were obtained to provide biomechanical mapping of the surfaces. The biphasic creep indentation methodology and an automated creep indentation apparatus were used to measure aggregate modulus, Poisson's ratio, permeability, shear modulus, and thickness. Biomechanical experiments were performed on four sites of the SMIC joint in 14 specimens (seven pairs): two sites in the second metatarsal base and two sites in the intermediate cuneiform head. Results of the study indicate that no significant variations exist in the biomechanical comparisons between specific articulations, gross articulations, and left and right joints. For example, cartilage from the second metatarsal base and intermediate cuneiform head had an aggregate modulus of 0.99 MPa and 1.05 MPa, respectively. The Poisson's ratio and permeability of all test sites grouped together were found to be 0.08 and 3.05 x 10(-15) m4/N.s, respectively. Cartilage thickness was measured at 0.61 mm. This biomechanical study suggests that similarities in cartilage properties may be beneficial in preventing the human SMIC articulation from developing early degenerative changes. Histological evaluation demonstrated that SMIC cartilage exhibits structural characteristics (such as the absence of chondrocyte columnar arrangement in the deep zone) which may be typical of cartilage that does not experience habitually high compressive stresses. This knowledge could aid surgeons in generating a deeper perspective of the relationship between clinical pathologies of articular cartilage and intrinsic biomechanical etiologies of degenerative joint diseases.

Intramedullary tibiotalocalcaneal arthrodesis (IMTCA) is an increasingly used procedure for salvage of complex hindfoot and ankle disorders. To avoid injury to vital plantar neurovascular structures, it is important to begin with an appropriate insertion site during retrograde IMTCA. We use a simple, reproducible method to determine this site based on anatomic landmarks.

In seven cases of Lisfranc joint injury after trauma, bunion deformity developed. This "traumatic bunion" occurs over a prolonged period of time after injury. A high index of suspicion is needed to identify the deformity as being traumatic in origin. Injury about the first metatarsophalangeal joint complex may also contribute to this deformity. When recognized, it may need to be treated with a first metatarsal-cuneiform fusion and distal soft tissue realignment.

Purpose: To evaluate the diagnostic capabilities of magnetic resonance (MR) imaging in the tarsometatarsal ([TMT] Lisfranc) joint with close anatomic correlation., Materials and Methods: Six normal cadaveric feet were imaged by using T1-weighted spin-echo (oblique axial) and three-dimensional spoiled gradient-recalled acquisition in the steady state ([SPGR] coronal, sagittal) sequences. Subsequently, gadolinium-enhanced arthrography was performed in three specimens followed by T1-weighted spin-echo and SPGR MR imaging. Specimens were sectioned in all three planes followed by correlation of the MR imaging results with gross anatomic findings., Results: In all specimens, the oblique axial and, less effectively, the coronal and sagittal planes allowed visualization of the Lisfranc ligament. Intermetatarsal ligaments were seen almost exclusively on the coronal images, and TMT ligaments on the sagittal images. Bone alignment could be assessed on the oblique axial images., Conclusion: MR imaging reliably depicts the anatomy of the TMT joint including ligamentous and osseous structures.

The authors describe the anatomical necessity and functional significance of torsion of the tendon of tibialis posterior. A wooden model of the right lower extremity has been constructed which includes representations of the ankle, subtalar, and oblique midtarsal joints. The model is used to show that the presence of torsion within the tendon of tibialis posterior eliminates the need for any longitudinal slippage between individual tendon fibers during triplane movement of the joints of the lower extremity.

The authors describe the anatomy, portal placement, technique, indications, and preliminary results of seven cases of calcaneocuboid or talonavicular joint pathology that underwent elective investigational diagnostic or therapeutic arthroscopy with a follow up of 3-14 months. All patients had failed available conservative therapy. Results of treatment were five excellent and two good cases. Two patients required arthrotomy. There were no complications associated with portal placement, arthroscopic technique, or instrumentation. Arthroscopy of the calcaneocuboid and talonavicular joints has proven to be a relatively safe and valuable diagnostic and therapeutic tool. It is hoped that advances in small joint arthroscopy application will encourage further technological evolution in arthroscopic instrumentation and establish a foundation for further arthroscopic exploration of the small joints of the foot.

We studied 15 cadaver feet to determine three-dimensional motion of selected tarsal bones under axial loading at three different loading levels. We determined the motion of individual joints and also the rotation of the tarsal bones in relation to the tibia. Joint rotations increased consistently with higher loads. The naviculartalar joint had the greatest total screw axis rotation, which averaged 9.4 degrees +/- 2.2 degrees at 667 N of load, followed by the first metatarsal-navicular (mean, 7.2 degrees +/- 1.5 degrees), talartibial (mean, 5.2 degrees +/- 1.6 degrees), and calcaneal-talar (mean, 4.4 degrees +/- 1.7 degrees) joints. The observed changes indicate the need for assessment of foot and ankle alignment clinically and radiologically while the patient is weightbearing.

Fifty-three ankles of 29 normal volunteers were examined with Magnetic Resonance Imaging (MRI) to improve the anatomical MR knowledge of tibiotalar and subtalar joints. The aim of our study was therefore to assess the visibility of articular cartilages, tendons and ligaments of the ankle and to define the best scan plane for their visualization. MR studies were performed with SE T1-weighted sequences on the sagittal, coronal and axial planes. The visibility of articular cartilages was 70.8% for the tibiotalar joint and 56.3% for the subtalar joint. All ankle tendons and four of the eight ankle ligaments considered in our study were assessed, at least on one of the sagittal, coronal or axial planes, with over 70% visibility. The deltoid ligament was detected in 95% of the cases on coronal images, the anterior and the posterior talofibular ligaments were seen respectively in 82% and in 75% of the cases on axial images, while the interosseous ligament was detected in 87.5% of the cases on sagittal images. Our study assessed both the capabilities and the limitations of MRI in the detection of anatomical structures of the tibiotalar and subtalar joints and defined the best scan plane for their visualization.

In six horses, a 0.05% solution of chlorhexidine diacetate was used to lavage one tarsocrural joint; the contralateral control joint was lavaged with lactated Ringer's solution. Horses were evaluated daily for lameness. Synovial fluid samples were collected on days 1, 4, and 8 for determination of protein concentration, total and differential leukocyte counts, and mucin clot formation. After death on day 8, synovium and osteochondral samples were collected from the tarsocrural joints for examination of morphology and proteoglycan staining. Lavage with chlorhexidine solution caused lameness that was reduced but still evident at day 8. Synovial protein concentration was significantly increased by chlorhexidine lavage; the greatest increase occurred on day 1. Joint lavage increased synovial leukocyte counts on day 1, primarily by increasing polymorphonuclear (PMN) cell counts. Although total synovial leukocyte counts returned to normal by day 4, PMN cell counts remained elevated through day 8; PMN cell counts for chlorhexidine-lavaged joints were typically twice that of control joints. Chlorhexidine lavage caused synovial ulceration, inflammation, and abundant fibrin accumulation. Consistent differences in proteoglycan staining were not detected between control and chlorhexidine-lavaged joints. Joint lavage with 0.05% chlorhexidine diacetate, the lowest known bactericidal concentration, is not recommended for equine joints.

Subtalar joint (STJ) measurements are commonly made in the clinic to assess foot and ankle positions because of the high incidence of lower extremity dysfunctions. The purposes of this study were to investigate the intratester and intertester reliability of the open kinetic chain subtalar joint neutral (OKC STJN) and closed kinetic chain subtalar joint neutral (CKC STJN) positions and the navicular drop test (NDT). Two inexperienced testers performed repeated measurements on 15 subjects (N = 30 feet) during two testing sessions. Intratester and intertester reliability (ICC 1,1) and standard error of measurement (SEM) were determined for each dependent variable. For OKC STJN, the intratester ICC values were .06 and .27, and the intertester ICC value was .00. The intratester SEM values were 1.81 and 2.29 degrees, and the intertester was 2.51 degrees. The CKC STJN intratester ICC values were .14 and .18, with SEM values of 2.46 and 2.40 degrees. The intertester CKC ICC value was .15, with an SEM of 2.43 degrees. For the NDT, the intratester ICC values were .61 and .79, and the SEM values were 1.92 mm and 2.57 mm. The intertester ICC value was .57 and the SEM was 2.72 mm. The results reveal that both OKC and CKC STJN yield poor intratester and intertester reliability and the NDT yields poor to moderate intratester reliability and poor intertester reliability. We conclude that these foot and ankle measurements are not reliable when performed by inexperienced testers. Therefore, clinicians should practice these measurement techniques and determine their measurement error.

A model of the human foot is proposed in which the foot is represented as eight rigid segments and eight monocentric, single-degree-of-freedom joints. The soft tissue under the foot is divided into seven independent sites of contact, or loading, and each of these is modelled as a nonlinear spring and a nonlinear damper in-parallel. The model was used to estimate the kinematics and kinetics of the foot during the stance phase of walking. The force sustained at each loading site was calculated from walking trials in which only portions of the foot landed on a small force platform. The position of the calcaneus was defined by surface markers, whereas the position of the distal segments were based upon chalk footprints and an estimate of the compression of the plantar soft tissue. The results suggest that the joints that constitute the longitudinal arch extend slightly when the forefoot is loaded. During push-off, these joints flex as the metatarsophalangeal joints extend. Similar kinematic results were estimated when the distal segments of the foot were defined by surface markers. The magnitude of the joint moments of force depended largely on the distribution of the load under the foot which varied considerably between subjects. The stable, yet resilient properties of the foot, as highlighted by this model, should be considered in three-dimensional dynamic models used to study human locomotion. The model provides an objective tool to quantify foot motion and loading, which may prove useful for describing foot function in normal and pathological conditions.

The frequency of communication between the tarsometatarsal and distal intertarsal joints was investigated in 27 horses and 12 ponies. After the injection of diluted latex into the tarsometatarsal joints using the plantarolateral approach, the horses and ponies were walked for 200 meters. Latex was found in the distal intertarsal joints of 19 of 73 tarsi (26% communication) at necropsy. In 3 tarsi, latex was also found in the proximal intertarsal and tarsocrural joints.

The MR imaging anatomy of the ankle has been well described. The anatomy of the forefoot, however, is not well understood by most radiologists. In many institutions, MR imaging studies are performed by using the head coil with large fields of view so that the appearance of the asymptomatic side can be used for comparison. At our institution, studies of the forefoot are performed with a specialized solenoid coil that allows a field of view of 8 cm with a resultant in-plane spatial resolution of approximately 0.3-0.4 mm. In this report, we present the MR imaging anatomy of the normal forefoot. Pertinent osseous, musculotendinous, and neurovascular structures are shown. Particular emphasis is placed on the compartmental anatomy of the foot, which is best imaged in the coronal plane.

After definition of the normal anatomic features of the tarsal sinus and canal at magnetic resonance (MR) imaging, 123 ankle MR imaging studies in 116 patients were reviewed. Abnormalities of the tarsal sinus and canal were seen on MR images in 33 cases (26.8%), were highly associated with tears of the lateral collateral ligament, and could be categorized according to the pathologic findings in patients with sinus tarsi syndrome: (a) diffuse infiltration with low T1- and T2-weighted signal intensity (n = 17) consistent with fibrosis, (b) diffuse infiltration with low T1-weighted signal intensity and increased T2-weighted signal intensity (n = 11) consistent with chronic synovitis and nonspecific inflammatory changes, and (c) multiple abnormal fluid collections (n = 5) consistent with synovial cysts. Absence of the anterior microrecesses of the posterior subtalar joint was a common finding on normal MR imaging studies (46 of 90) and may reflect lack of iatrogenic joint distention. Tears of the posterior tibial tendon may have a previously unrecognized association with the sinus tarsi syndrome.

The authors have performed 20 systematical dissections of the distal part of the foot, conserved in the Toulon's liquor and 3 dissections of fresh cadavers. The last ones have been submitted at different puttings in charge before and after the resection of the intermetatarsal transverse ligament. The intermetatarsal transverse ligament is supple, extensible, but very strong. It constitutes the area of convergence of all the neighbouring fibrous structures and of several tendons of the foot. It connects together the heads of the metatarsus. It renders them jointly liable and its action is reflected above. By its modulating of the convergence of the metatarsus and their necessary associated palmar inclination, by its limitation of their divergence in relation with their dorsal inclination, it modulates and it limits the amplitude of the tarsometatarsal joints. It is helped for that by the little intermetatarsal transverse ligaments, whose the presence has been always confirmed. The metatarsus varus, very frequently associated with the hall valgus, means the escape of the first ray from the effect of the transverse intermetatarsal ligament.

300 medial cuneiform bones were examined to explore the different forms of the joint surface on the lateral side of the bone facing the intermediate cuneiform bone. This joint surface consists of two parts, a proximal one and a dorsal one. The proximal part is orientated dorsoplantarally. At its proximal margin there exists a tight contact with the proximal joint surface for the navicular bone. The dorsal part is sited at the dorsal margin of the lateral side of the bone. Different forms of fusion of these part could be seen. In 62.67% they show tight confluence. In 17.67% the fusion is limited to a slight contact. In the rest, 19.67%, there exists no contact between these two parts. These forms correlate to the proximal height of the bone. A large proximal height extends the degree of separation of the dorsal joint surfaces (consisting of the dorsal section of the proximal part and the whole dorsal of the joint surface for the intermediate cuneiform bone as well as the joint surface for the second metatarsal bone). Therefore these joint surfaces are split to their components.

Study Objectives: To reappraise Boehler's angle and evaluate factors, including centering of the central beam, sex of subjects, and side of the body, that may affect angle measurement., Design: Retrospective clinical review., Setting: Emergency department, Level I trauma center., Type of Participants: 120 consecutive patients radiographed for ankle injury who had normal bones on the ankle and/or foot radiographs., Measurements and Main Results: The mean and SD of Boehler's angle were 30 degrees C +/- 6 degrees (range, 14 degrees to 50 degrees). There was no difference in Boehler's angle between male and female subjects (P greater than .05) or between left and right feet (P greater than .05). Slight variations in central beam location for ankle and foot radiographs had no significant effect on Boehler's angle., Conclusion: If 28 degrees is taken as the lower limit of normal for Boehler's angle, 37 cases (31%) would be false-positive "abnormal." The use of 20 degrees as the lower limit may decrease the number of false-positive to three cases (2.5%); using 18 degrees (mean -2 SD) reduces the false-positive rate to less than 1% (one case).

The normal anatomy of the lateral ankle and subtalar ligaments seen at magnetic resonance (MR) imaging was studied in four cadaver ankles. Sixteen ankles of 11 healthy volunteers were imaged with four different MR imaging protocols to optimize technique. The anterior talofibular ligament was identified in 100% of the ankles of the volunteers in the axial plane, the calcaneofibular ligament in 81% of the ankles in the coronal plane, the cervical ligament in 69% of the ankles in the coronal plane and in 88% of the ankles in the sagittal plane, and the talocalcaneal ligament in 56% of the ankles in the coronal plane and in 62% of the ankles in the sagittal plane. It is concluded that thin-section (1-3-mm) MR imaging techniques, especially the one in which data are acquired with three-dimensional Fourier transform, are best for visualization of the ligaments. These techniques may play a role in the evaluation of patients with chronic ankle pain and instability.

This study compares the standardized measurements of the foot in nonweight-bearing and weight-bearing radiographs. Both normal and hallux valgus patients were studied. The results show that some changes thought to occur with weight-bearing cannot be consistently demonstrated. Obtaining both weight-bearing and nonweight-bearing views may not be routinely indicated in all patients.

Hallucal tarsometatarsal joints from African pongids, modern humans, and Australopithecus afarensis are compared to investigate the anatomical and mechanical changes that accompanied the transition to terrestrial bipedality. Features analyzed include the articular orientation of the medial cuneiform, curvature of the distal articular surface of the medial cuneiform, and the articular configuration of the hallucal metatarsal proximal joint surface. Morphological characteristics of the hallucal tarsometatarsal joint unequivocally segregate quadrupedal pongids and bipedal hominids.

Dislocations and fracture-dislocations of the tarsometatarsal joints, fractures of the base of the fifth metatarsal bone, fractures of the shafts and necks of the metatarsal bones, dislocations of the metatarsophalangeal joints, fractures of the phalanges and dislocations of the interphalangeal joints each have a specific mechanism of injury, characteristic diagnostic feature, and requirement for treatment. Only by an accurate diagnosis established by careful physical and roentgenographic examination can complications be avoided.