Physiologic effects of long-term immobilization of the equine distal limb.

OBJECTIVE: To describe the effects of distal limb immobilization and remobilization in the equine metacarpophalangeal joint. STUDY DESIGN: Randomized, prospective experimental study. ANIMALS: Eight healthy, skeletally mature horses. METHODS: One forelimb of each horse was immobilized in a fiberglass cast for 8 weeks; this was followed by 12 weeks of a treadmill-based training program after the cast had been removed. Clinical examinations, radiography, computed tomography (CT), nuclear scintigraphy, MRI, and histomorphometry were used to examine the third metacarpal (MC3), proximal phalanx, proximal sesamoid bones, and associated soft tissues in each horse. Serum and synovial fluid were collected for biomarker analyses. RESULTS: Distal limb immobilization resulted in persistent lameness (P < .001), effusion (P = .002), and a decreased range of motion (P = .012) as well as radiographically visible fragments (P = .036) in the cast forelimb. Bone density was decreased (P < .001) in MC3 according to CT, and trabecular bone fluid was increased (P < .001) according to MRI in the cast forelimb. The cast forelimbs had a change (P = .009) in the appearance of the deep digital flexor tendon according to MRI immediately after removal of the cast. Numerous clinical, radiographic, CT, and MR abnormalities were visible at the end of the study period. CONCLUSION: Eights weeks of cast immobilization induced changes in bone, cartilage, and periarticular soft tissues that were not reversed after 12 weeks of remobilization. CLINICAL SIGNIFICANCE: Cast application should be used judiciously in horses with musculoskeletal injuries, balancing appropriate stabilization with potential morbidity secondary to cast placement.

Ex vivo effects of insulin on the structural integrity of equine digital lamellae.

BACKGROUND: Laminitis has a considerable impact on the equine industry. Endocrinopathic laminitis is the most common form and affected horses often have hyperinsulinaemia due to an underlying metabolic disorder. OBJECTIVES: The aim of this study was to determine if insulin weakens the structural integrity of digital lamellae and to develop an ex vivo model for the study of hyperinsulinaemia-induced lamellar failure. STUDY DESIGN: Ex vivo experiment. METHODS: Biomechanical testing was used to assess the structural integrity of lamellar explants exposed to either medium alone (control) or medium supplemented with insulin. Lamellar explants comprised of hoof wall, lamellar tissue and distal phalanx were harvested from four adult horses with no evidence of inflammatory disease or pre-existing disease of the digit. Following an equilibration period, explants were incubated in medium or medium supplemented with insulin (2.5 µg/ml) for 8 h prior to biomechanical testing to obtain load (N), stress (MPa), elongation to failure (mm), and Young's modulus (MPa) for each explant. Significant differences were assessed using a mixed linear model with horses as a random factor and control or insulin-treated group as a fixed factor. RESULTS: Lamellar explants incubated in medium supplemented with insulin failed at significantly lower load (P = 0.0001) and lower stress (P = 0.001) and had greater elongation to failure (P = 0.02). MAIN LIMITATIONS: In addition to the ex vivo nature of the study, location-dependent variability in explant structural integrity and variable diffusion of nutrients due to explant size may have been limitations. However, the study design attempted to account for these limitations through random assignment of explants to treatment groups independent of location and by evaluating stress to failure. CONCLUSIONS: Insulin weakens the structural integrity of equine lamellar explants and an ex vivo model for evaluation of hyperinsulinaemia-induced lamellar failure was established. The summary is available in Spanish - see Supporting Information.

Blastema formation and periosteal ossification in the regenerating adult mouse digit.

While mammals cannot regenerate amputated limbs, mice and humans have regenerative ability restricted to amputations transecting the digit tip, including the terminal phalanx (P3). In mice, the regeneration process is epimorphic and mediated by the formation of a blastema comprised of undifferentiated proliferating cells that differentiate to regenerate the amputated structures. Blastema formation distinguishes the regenerative response from a scar-forming healing response. The mouse digit tip serves as a preclinical model to investigate mammalian blastema formation and endogenous regenerative capabilities. We report that P3 blastema formation initiates prior to epidermal closure and concurrent with the bone histolytic response. In this early healing response, proliferation and cells entering the early stages of osteogenesis are localized to the periosteal and endosteal bone compartments. After the completion of stump bone histolysis, epidermal closure is completed and cells associated with the periosteal and endosteal compartments blend to form the blastema proper. Osteogenesis associated with the periosteum occurs as a polarized progressive wave of new bone formation that extends from the amputated stump and restores skeletal length. Bone patterning is restored along the proximal-distal and medial digit axes, but is imperfect in the dorsal-ventral axis with the regeneration of excessive new bone that accounts for the enhanced regenerated bone volume noted in previous studies. Periosteum depletion studies show that this compartment is required for the regeneration of new bone distal to the original amputation plane. These studies provide evidence that blastema formation initiates early in the healing response and that the periosteum is an essential tissue for successful epimorphic regeneration in mammals.

Phalangeal joints kinematics in ostrich (Struthio camelus) locomotion on sand.

In ostriches, the toes are the only body parts that contact loose sand surfaces. Thus, toe interphalangeal joint motions may play vital biomechanical roles. However, there is little research on ostrich phalangeal joint movements while walking or running on sand. The results from the three-dimensional motion track analysis system Simi Motion show that gait pattern has no significant effect on the key indicators (angles at touch-down, mid-stance, lift-off and range of motion) of the toe joint angles. The motion of the toe phalanges when walking and running on sand is basically the same. The ground medium is the key factor that changes the toe postures adopted by ostriches during the stance phase in slow to fast locomotion. The 3rd toe and the 4th toe are connected by the interphalangeal ligament, and the motions of the MTP3 and MTP4 joints are highly synchronized on a loose sand substrate. The 3rd toe and 4th toe are coupled to maintain static balance in slow locomotion and dynamic balance in fast locomotion. In addition, the gait pattern has a marked effect on the range of forward displacement of the toenail (YTN). The ostrich toenail plays an important role in preventing slip and provides traction at push-off in a sandy environment. The metatarsophalangeal joint plays an important role in energy saving during fast locomotion on loose sand substrates. Simulation reveals that the particle velocity field, particle force field and sand particle disturbance in the running gait are denser than those in the walking gait.

Level-specific amputations and resulting regenerative outcomes in the mouse distal phalanx.

Mouse digit tip regeneration involves an intricate coordinated regrowth of the terminal phalanx, nail, dermis and epidermis. During this time, regenerating digits undergo wound healing, blastema formation, and differentiation. However, the regenerative response of the digit is dependent on the level of the amputation. Amputation of <30% of the distal phalanx (P3), with part of the base nail remaining, results in extensive digit regeneration. In contrast, >60% P3 removal results in no regeneration. This level-dependent regenerative ability of the mouse digit provides a comparative model between regeneration and non-regeneration that may enable identification of specific factors critical to regeneration. Although the ability to create regenerating and non-regenerating conditions has been well established, the regenerative response between these regions ("intermediate" zone) has received less scrutiny, and may add insight to the regenerative processes, including the degree of histolysis, and the level of blastema formation. The objective of this study is then to compare the regeneration capacity between amputation levels within the regenerating (<30%), intermediate (40-59%), and non-regenerating (>60%) regions. Results indicated that regenerative and intermediate amputations led to significant histolysis and blastema formation of the distal phalanx 14 days post-amputation. Unlike the regenerating digits, intermediate amputations led to incomplete regeneration whereby regrowth of the digits were not to the levels of the intact or regenerating digits. Non-regenerating amputations did not exhibit significant histolysis or blastema formation. Remarkably, the histolytic process resulted in day 14 P3 lengths that were similar regardless of the initial amputation over 19%. The differences in histolysis, blastema formation and injury outcomes were also marked by changes in the number of proliferating cells and osteoclasts. Altogether, these results indicate that although intermediate amputations result in histolysis and blastema formation similar to regenerating digits, the resulting cellular composition of the blastema differs, contributing to incomplete regeneration.

Grasping primate development: Ontogeny of intrinsic hand and foot proportions in capuchin monkeys (Cebus albifrons and Sapajus apella).

Young primates have relatively large hands and feet for their body size, perhaps enhancing grasping ability. We test the hypothesis that selection for improved grasping ability is responsible for these scaling trends by examining the ontogeny of intrinsic hand and foot proportions in capuchin monkeys (Cebus albifrons and Sapajus apella). If selection for improved grasping ability is responsible for the observed patterns of hand and foot growth in primates, we predicted that fingers and toes would be longer early in life and proportionally decline with age. We measured the lengths of manual and pedal metapodials and phalanges in a mixed-longitudinal radiographic sample. Bone lengths were (a) converted into phalangeal indices (summed non-distal phalangeal length/metapodial length) to test for age-related changes in intrinsic proportions and (b) fit to Gompertz models of growth to test for differences in the dynamics of phalangeal versus metapodial growth. Manual and pedal phalangeal indices nearly universally decreased with age in capuchin monkeys. Growth curve analyses revealed that metapodials generally grew at a faster rate, and for a longer duration, than corresponding phalanges. Our findings are consistent with the hypothesis that primates are under selection for increased grasping ability early in life. Relatively long digits may be functionally adaptive for growing capuchins, permitting a more secure grasp on both caregivers and arboreal supports, as well as facilitating early foraging. Additional studies of primates and other mammals, as well as tests of grasping performance, are required to fully evaluate the adaptive significance of primate hand and foot growth.

Does subchondral bone of the equine proximal phalanx adapt to race training?

Sagittal fractures of the first phalanx are a common, potentially catastrophic injury in racehorses. These fractures are often linked to an acute, one time, biomechanical event; however, recent evidence implies that chronic exposure to stress can lead to the accumulation of bony changes that affect the structural integrity of the bone and increase the likelihood of fracture. The aim of the study was to compare variations of two common metrics of bone adaptation - subchondral bone density and thickness across the proximal articular surface of the first phalanx in Thoroughbred horses that (1) raced but never experienced a first phalanx fracture (Raced Control); (2) raced and had experienced fracture of the contralateral first phalanx (Contralateral to Fracture); (3) had never raced or experienced a first phalanx fracture (Unraced Control). A total of 22 first phalangeal bones were sampled post-mortem and imaged using micro-computed tomography calibrated for mineral density measures. Measurements of volumetric subchondral bone mineral density and thickness were taken from images at five sites from medial to lateral, in three coronal planes (25, 50 and 75% dorsal-palmar). At each of the 15 sites, measurements were repeated and averaged across 10 adjacent micro-computed tomography slices of bone, spanning 0.75 mm. The magnitude and variance of these measurements were compared between sites and between cohorts with non-parametric statistical tests. Across the proximal osteochondral surface of the first phalanx, the pattern of subchondral bone volumetric bone mineral density and thickness varied with each coronal section studied. The subchondral bone thickness was greater for the central and dorsal coronal sections, compared with the palmar section. For the race-fit groups (Raced Control and Contralateral to Fracture), the highest volumetric bone mineral density was in the central sagittal groove. The volumetric bone mineral density was significantly greater in the sagittal groove in the central coronal section in the raced than the unraced group. The Contralateral to Fracture group demonstrated significantly greater variance of volumetric bone mineral density compared with the Raced Control and Unraced Control (P < 0.0001), with no difference in variance noted between the Raced Control and Unraced Control groups. There was a small (R rank = 0.3) but significant correlation between subchondral bone volumetric bone mineral density and thickness in the Contralateral to Fracture group (P = 0.005). The findings demonstrate that differences exist in subchondral bone volumetric bone mineral density and thickness across the proximal osteochondral surface of the equine first phalanx in horses with different training histories. The findings also demonstrate that the subchondral bone of the sagittal groove of the equine first phalanx adapts to race-training in the race-fit groups (Raced Control and Contralateral to Fracture) with an increase in volumetric bone mineral density relative to unraced controls. Within the race-trained groups, the Contralateral to Fracture bones had a greater variance of volumetric bone mineral density, suggesting that stress-induced bone adaptation had become more erratic, potentially contributing to the aetiology of sagittal fractures of the first phalanx in the Thoroughbred racehorse.

Hardness map of human meta tarsals and phalanges of toes.

Predicting location of fracture in human bones has been a keen area of research for the past few decades. A variety of tests for hardness, deformation and strain field measurement have been conducted in the past; but considered insufficient due to various limitations. Researchers therefore have proposed further studies due to inaccuracies in measurement methods, testing machines and experimental errors. Advancement and availability of hardware, measuring instrumentation and testing machines can now provide remedies to these limitations. Human foot is a critical part of body exposed to various forces throughout its life. A number of products are developed for using over it for protection and care. Which many times do not provide sufficient protection and may itself become a source of stress due to non-consideration of the delicacy of bones in the feet. A continuous strain or overloading on feet may occur resulting to discomfort and even fracture. Not knowing how the hardness is spread all over the Meta tarsals and phalanges is one of major contributory factor for unsatisfactory design of foot protection products. This paper provides a complete hardness distribution map developed by experimental testing of all the Meta tarsals and Phalanges of toes for a typical human foot. The bones were taken from two left feet of a 40 and 42 year old male cadaver. These were dehydrated prior to measurements of hardness using Leeb hardness testing method. Hardness was measured around the circumference of a bone as well as along its length. Hardness values can be related to tensile strength of the bones to predict possible values of stress that could be borne by these bones. Results may also be used for design and developing various accessories for human feet health care and comfort.

Metrical analysis of dromedary digital bones.

Dromedary camels are large even-toed ungulates which are well adapted to life in large deserts. Examinations of their feet have revealed many structural peculiarities. We have measured the digital bones of the dromedary in order to determine whether there are morphometric variations in the digital bones between the lateral and medial sides in individual limbs and/or in the right and left thoracic and pelvic limbs, with the aim to clarify whether there are anatomical differences in the digital bones of dromedary as a suborder of the order Artiodactyla. Measurements were made of 240 lateral and medial proximal, middle, and distal phalanges in the left and right thoracic and pelvic limbs of ten healthy adult male dromedaries, ranging in age from 6 to 10 years. A total of 17 linear dimensions were measured using a caliper. The results indicate that there are no significant differences between corresponding measurements of digital bones of the lateral and medial in the same limb, nor between measurements of the right and left sides. The lengths and widths of the proximal and middle, and distal phalanges in the thoracic limb were found to be greater than those of the pelvic limb. The sum of the total lengths of the three phalanges of the thoracic limbs was 15 mm greater than that of the phalanges of the pelvic limbs due to a longer proximal phalanx (76 %) and middle phalanx of the former (24 %). The perspectives obtained by our morphometric study of dromedary digital bones not only provide a tool to distinguish the osteological remains of the dromedary from those of the Bactrian camel or other artiodactyls in archaeological sites, but they also suggest a possible influence of digital structure on digit functions and digital disorders.

Analysis of joint force and torque for the human and non-human ape foot during bipedal walking with implications for the evolution of the foot.

The feet of apes have a different morphology from those of humans. Until now, it has merely been assumed that the morphology seen in humans must be adaptive for habitual bipedal walking, as the habitual use of bipedal walking is generally regarded as one of the most clear-cut differences between humans and apes. This study asks simply whether human skeletal proportions do actually enhance foot performance during human-like bipedalism, by examining the influence of foot proportions on force, torque and work in the foot joints during simulated bipedal walking. Skeletons of the common chimpanzee, orangutan, gorilla and human were represented by multi-rigid-body models, where the components of the foot make external contact via finite element surfaces. The models were driven by identical joint motion functions collected from experiments on human walking. Simulated contact forces between the ground and the foot were found to be reasonably comparable with measurements made during human walking using pressure- and force-platforms. Joint force, torque and work in the foot were then predicted. Within the limitations of our model, the results show that during simulated human-like bipedal walking, (1) the human and non-human ape (NHA) feet carry similar joint forces, although the distributions of the forces differ; (2) the NHA foot incurs larger joint torques than does the human foot, although the human foot has higher values in the first tarso-metatarsal and metatarso-phalangeal joints, whereas the NHA foot incurs higher values in the lateral digits; and (3) total work in the metatarso-phalangeal joints is lower in the human foot than in the NHA foot. The results indicate that human foot proportions are indeed well suited to performance in normal human walking.

Do methods for predicting paleohabitats apply for mountain and insular fossil bovids?

A variety of methods have been developed to use bovid postcranial elements in the functional morphology approach to paleohabitat prediction. This study represents a first attempt at testing morphometric methods based on astragalus and phalanges on extant mountain-dwelling bovids and insular fossil bovids from Sardinia assigned to the so-called 'Nesogoral group', already regarded as close to the Caprini tribe. We intended to answer the questions whether a classic four-habitats model could be successfully applied to extant mountain-dwelling bovids, and whether results obtained could support the hypothesis of a radiative evolution for the Sardinian bovids. Results obtained, on the one hand, highlighted some inadequacies of the method if not applied to African bovids; on the other hand, they stressed the difficulties of discriminating habitat preferences of Sardinian taxa only based on biometry of astragalus and phalanges. Nonetheless, statistical habitat predictions suggest the contemporaneous presence in Sardinia of bovids having about the same size, but inhabiting different environments, giving support to the hypothesis that Sardinian representatives of the genus Nesogoral originated from a still unknown ancestor by an adaptive radiation evolutionary process.

First metatarsophalangeal joint motion in Homo sapiens: theoretical association of two-axis kinematics and specific morphometrics.

BACKGROUND: The metatarsal head and proximal phalanx exhibit considerable asymmetry in their shape and geometry, but there is little documentation in the literature regarding the prevalence of structural characteristics that occur in a given population. Although there is a considerable volume of in vivo and in vitro experiments demonstrating first metatarsal inversion around its longitudinal axis with dorsiflexion, little is known regarding the applicability of specific morphometrics to these motions. METHODS: Nine distinctive osseous characteristics in the metatarsal head and phalanx were selected based on their location, geometry, and perceived functional relationship to previous studies describing metatarsal motion as inversion with dorsiflexion. The prevalences of the chosen characteristics were determined in a cohort of 21 randomly selected skeletal specimens, 19 of which were provided by the anatomical preparation office at the University of California, San Diego, and two of which were in the possession of one of us (M.D.). RESULTS: The frequency of occurrence of each selected morphological characteristic in this sample and the relevant summary statistics confirm a strong association between the selected features and a conceptual two-axis kinematic model of the metatarsophalangeal joint. CONCLUSIONS: The selected morphometrics are consistent with inversion of the metatarsal around its longitudinal axis as it dorsiflexes.

Morphological correlates of the grooming claw in distal phalanges of platyrrhines and other primates: a preliminary study.

Grooming claws are present on the second pedal digits of strepsirhines and on the second and third pedal digits of tarsiers. However, their presence in New World monkeys is often overlooked. As such, the absence of a grooming claw is generally considered an anthropoid synapomorphy. This study utilizes a quantitative multivariate analysis to define grooming claw morphology and document its presence in platyrrhine monkeys. Our results show that owl monkeys possess grooming claws similar to those of strepsirhines, while titi monkeys possess grooming claw-like morphology. Therefore, we conclude that anthropoids are not clearly united by the absence of a grooming claw. Furthermore, due to their presence in three major primate clades, we infer that it is likely that a grooming claw was present on the second pedal digit of the ancestor of living primates. Therefore, we advise the reassessment of fossil adapids in light of the anatomical correlates described here. This should increase resolution on the homology and polarity of grooming claw morphology, and, therefore, will help provide a sharper picture of primate evolution.

Radiographic evaluation of changes in the proximal phalanx of Thoroughbreds in race training.

OBJECTIVE: To evaluate changes in the cortical bone of the proximal phalanx of the fore-limbs of Thoroughbreds in response to training. ANIMALS: Twenty-seven 2-year-old Thoroughbreds (20 females, 2 males, and 5 geldings). PROCEDURES: Horses were principally in training for races in a straight line and in a clockwise direction. Lateromedial and dorsopalmar radiographic views of each metacarpophalangeal joint were obtained before the horses started training and 1 year after starting exercise and racing. Width of the dorsal, palmar, lateral, and medial cortex and the width and thickness of the medulla were measured. Ratios (rather than absolute values) were used to remove the effect of differences in bone size among horses. RESULTS: 10 horses were lost from the study. Radiographs were obtained for 17 horses 1 year after starting training (9 horses raced in a clockwise direction, and 8 raced in clockwise and counterclockwise directions). There was no difference between the cortical bone in the right and left forelimbs at the start of the study. After training for 1 year, the palmar cortex in the right forelimb was significantly thicker than that in the left forelimb. CONCLUSIONS AND CLINICAL RELEVANCE: The strain patterns, biomechanics of rapid exercise, and type of training most probably determined differences in the adaptive responses of the proximal phalanx. The data reported here can be used in the evaluation of weight-bearing distribution along the proximal phalanx and evaluation of the relationship between exercise and bone remodelling of the proximal phalanx.

Receptor tyrosine kinase-like orphan receptor 2 (ROR2) and Indian hedgehog regulate digit outgrowth mediated by the phalanx-forming region.

Elongation of the digit rays resulting in the formation of a defined number of phalanges is a process poorly understood in mammals, whereas in the chicken distal mesenchymal bone morphogenetic protein (BMP) signaling in the so-called phalanx-forming region (PFR) or digit crescent (DC) seems to be involved. The human brachydactylies (BDs) are inheritable conditions characterized by variable degrees of digit shortening, thus providing an ideal model to analyze the development and elongation of phalanges. We used a mouse model for BDB1 (Ror2(W749X/W749X)) lacking middle phalanges and show that a signaling center corresponding to the chick PFR exists in the mouse, which is diminished in BDB1 mice. This resulted in a strongly impaired elongation of the digit condensations due to reduced chondrogenic commitment of undifferentiated distal mesenchymal cells. We further show that a similar BMP-based mechanism accounts for digit shortening in a mouse model for the closely related condition BDA1 (Ihh(E95K/E95K)), altogether indicating the functional significance of the PFR in mammals. Genetic interaction experiments as well as pathway analysis in BDB1 mice suggest that Indian hedgehog and WNT/beta-catenin signaling, which we show is inhibited by receptor tyrosine kinase-like orphan receptor 2 (ROR2) in distal limb mesenchyme, are acting upstream of BMP signaling in the PFR.

The anatomy and physiology of the suspensory apparatus of the distal phalanx.

The equine hoof capsule protects the softer, more sensitive, structures within. Failure of the connection between hoof and bone (suspensory apparatus of the distal phalanx or SADP) results in the crippling lameness of laminitis. Active basal cell proliferation occurs principally in tubular hoof and proximal and distal lamellae. The remaining lamellae are virtually non-proliferative and the hoof wall moves past the stationary distal phalanx, by controlled activation and inhibition of constituent proteases. The lamellar corium derives most of its blood supply from the branches of the terminal arch which perforate the distal phalanx. Valveless veins within the foot can be exploited clinically for retrograde venous therapy or contrast radiography (venography). The basement membrane (BM) forms the interface between the lamellar epidermis and the adjacent dermis and the plasma membrane of each lamellar basal cell is attached to the BM by numerous electron dense adhesion plaques or hemidesmosomes the ultimate attachment unit of the SADP. Laminitis destroys and dislocates the BM and its components and without an intact, functional BM, the structure and function of the lamellar epidermis is pathologically compromised. Transcription and activation of constituent proteases occurs in normal hoof lamellae but in increased amounts during laminitis.

Joint orientation and function in great ape and human proximal pedal phalanges.

Previous studies have referred to the degree of dorsal canting of the base of the proximal phalanx as an indicator of human-like metatarsophalangeal joint function and thus a diagnostic trait of habitual bipedality in the fossil record. Here, we used a simple method to investigate differences in forefoot function on a finer scale. Building on Duncan et al.'s (Am J Phys Anthropol 93 [1994] 67-81) research, we tested whether dorsal canting reflects differences between sexes in locomotor behavior, whether habitual shoe wear influences dorsal canting in humans, and whether proximal joint morphology differs between rays in Pan and humans. Our results corroborate previous research in showing that humans have proximal phalanges with joint orientations that are significantly more dorsal than, but overlap with, those of great apes. We also found that male gorillas have significantly more dorsally canted second proximal phalanges than their female counterparts, while the opposite pattern between the sexes was found in Pan troglodytes. Inter-ray comparisons indicate that Pan have more dorsally canted first proximal phalanges than second proximal phalanges, while the opposite pattern was found in humans. Minimally shod humans have slightly but significantly more dorsally canted second proximal phalanges than those of habitually shod humans, indicating that phalanges of unshod humans provide the most appropriate comparative samples for analyses of early hominins. Overall, our analysis suggests that though the measurement of dorsal canting is limited in its sensitivity to certain intraspecific differences in function, phalangeal joint orientation reflects interspecific differences in joint function, with the caveat that different patterns of forefoot function during gait can involve similar articular sets of metatarsophalangeal joints.

Long distance running increases plantar pressures beneath the metatarsal heads: a barefoot walking investigation of 200 marathon runners.

BACKGROUND: The growing popularity of endurance sports activities is associated with a growing number of metatarsal stress fractures in recreational runners. Excessive foot loading has been suggested as a potential cause for these problems [Bennell, K, Matheson G, Meeuwisse W, Brukner P. Risk factors for stress fractures. Sports Med 1999;28(2):91-122]. Therefore, the question arises whether long distance running affects foot loading characteristics like ground reaction forces and peak pressure in specific areas of the foot. PURPOSE: To investigate the effects of long distance running on plantar pressure patterns before and after a marathon race. STUDY DESIGN: Repeated measurements of recreational runners before and after a marathon race. METHODS: Two hundred participants of the third Muenster marathon, 2004, were measured before and after the race with plantar pressure measurements during barefoot walking on a capacitive platform. The ratio between forefoot and toe loading was calculated to assess a suggested loading shift between these areas. RESULTS: The results of the whole group of participants revealed a significant difference in foot loading characteristics before and after the race. Post-race peak pressure and impulse values were higher in the forefoot regions and reduced under the toes. CONCLUSIONS: The increased peak pressure under the metatarsal heads after the race indicates a load shift from the toes to the metatarsal heads. This suggests an increased loading of the metatarsal bones and could explain the increased incidence of metatarsal stress fractures in long distance runners.

Comparative morphometrics of the primate apical tuft.

The relationship between the structure and function of the primate apical tuft is poorly understood. This study addresses several hypotheses about apical tuft morphology using a large modern primate comparative sample. Two indices of tuft size are employed: expansion and robusticity. First, comparisons of relative apical tuft size were drawn among extant nonhuman primate groups in terms of locomotion and phylogenetic category. Both of these factors appear to play a role in apical tuft size among nonhuman primates. Suspensory primates and all platyrrhines had the smallest apical tufts, while terrestrial quadrupeds and all strepsirrhines (regardless of locomotor category) had the largest tufts. Similarly, hypotheses regarding the apical tufts of hominins, especially the large tufts of Neandertals were addressed using a comparison of modern warm- and cold-adapted humans. The results showed that cold-adapted populations possessed smaller apical tufts than did warm-adapted groups. Therefore, the cold-adaptation hypothesis for Neandertal distal phalangeal morphology is not supported. Also, early modern and Early Upper Paleolithic humans had apical tufts that were significantly less expanded and less robust than those of Neandertals. The hypothesis that a large apical tuft serves as support for an expanded digital pulp is supported by radiographic analysis of modern humans in that a significant correlation was discovered between the width of the apical tuft and the width of the pulp. The implications of these findings for hypotheses about the association of apical tuft size and tool making in the hominin fossil record are discussed.