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Objective: To quantify the translation and angular rotation of the distal sesamoid bone (DSB) using computed tomography (CT) and medical modeling software., Sample: 30 thoracic limbs from equine cadavers., Procedures: Partial (n = 12), full (8), and matched full and subsequently transected (10) thoracic limbs were collected. Bone volume CT images were acquired in three positions: extension (200° metacarpophalangeal angle), neutral (180°), and maximal flexion (110°). Mean translation and angular rotation of each DSB were recorded. Differences were determined with two-way ANOVA and post hoc Tukey's tests for pairwise comparisons; P value was set at < 0.05., Results: Dorsal translation was significant during extension (1.4 ± 0.4 mm full limbs and 1.3 ± 0.2 mm partial limbs, P < 0.001). Distal translation was significant during extension (1.9 ± 0.4 mm full and 1.1 ± 0.4 mm partial) and flexion (5.4 ± 0.7 mm full and 6.22 ± 0.6 mm partial, P < 0.001). Rotation was significant (P < 0.001) about the mediolateral axis during extension (17.1° ± 1.4°) and flexion (2.6° ± 1.3°). Translation and rotation of the DSB were significantly different (P < 0.001) between full and partial limbs., Clinical Relevance: This study provides the first quantification of translation and angular rotation of the DSB within the equine hoof. Partial limbs had significantly reduced movement compared to full limbs, suggesting that transection of flexor tendons alters distal thoracic limb kinematics. Further studies are required to determine if pathologic changes in the podotrochlear apparatus have an impact in clinical lameness outcomes.

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

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., (© 2020 The American College of Veterinary Surgeons.)

Objectives: This study aims to document a detailed investigation on the sesamoid bones (SBs) of Turkish subjects from different parts of Turkey in a multi-center study, in both hands, according to gender, frequency and divisions of the bones' coexistence and bilaterality by radiography., Patients and Methods: This retrospective and three-centered study was performed between June 2010 and April 2012. Sesamoid bones were examined by anteroposterior and oblique X-rays of 1,444 hands of 772 subjects (367 males, 405 females; mean age 42.7 years; range, 18 to 87 years). All X-rays were evaluated by at least two independent observers. In controversial circumstances, at least three observers together gave the final decision by consensus., Results: Metacarpophalengeal (MCP) joint of the thumb (MCP 1) had sesamoid in all subjects (100%) and it was seen bilaterally. The prevalence of the SB was 42.8% in the second MCP joint (MCP 2) in 772 subjects and 36.6% in 1,444 hands, 1.6% in the third MCP joint (MCP 3) for the subjects and 1.1% for the hands, 0.1% in the fourth MCP joint (MCP 4) for the subjects and 0.1% for the hands, and 72.5% in the fifth MCP joint (MCP 5) for the subjects and 62.5% for the hands. The prevalence of SB in the first interphalangeal joint (IP 1) was 21.8% and SB was detected in 18.6% of the hands. Sesamoid bones of the MCP 2, MCP 5, and IP 1 was recorded more frequently in females. Sesamoid bone of the same joints (MCP 2, MCP 5 and IP 1) was detected more frequently bilaterally than unilateral right side and more frequently unilaterally on right side than unilateral left side., Conclusion: The distribution of SBs varies according to hand regions, gender, and side. Having knowledge of the locations and the rate of bilaterality of SBs may assist clinicians in both clinical and radiological diagnoses.

Along with supernumerary bones, sesamoids, defined as any organized intratendinous/intraligamentous structure, including those composed of fibrocartilage, adjacent to an articulation or joint, have been frequently considered as enigmatic structures associated with the joints of the skeletal system of vertebrates. This review allows us to propose a dynamic model to account for part of skeletal phenotypic diversity: during evolution, sesamoids can become displaced, attaching to and detaching from the long bone epiphyses and diaphysis. Epiphyses, apophyses and detached sesamoids are able to transform into each other, contributing to the phenotypic variability of the tetrapod skeleton. This dynamic model is a new paradigm to delineate the contribution of sesamoids to skeletal diversity. Herein, we first present a historical approach to the study of sesamoids, discussing the genetic versus epigenetic theories of their genesis and growth. Second, we construct a dynamic model. Third, we present a summary of literature on sesamoids of the main groups of tetrapods, including veterinary and human clinical contributions, which are the best-studied aspects of sesamoids in recent decades. Finally, we discuss the identity of certain structures that have been labelled as sesamoids despite insufficient formal testing of homology. We also propose a new definition to help the identification of sesamoids in general. This review is particularly timely, given the recent increasing interest and research activity into the developmental biology and mechanics of sesamoids. With this updated and integrative discussion, we hope to pave the way to improve the understanding of sesamoid biology and evolution., (© 2019 Cambridge Philosophical Society.)

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

The patella ("kneecap") is a biomechanically important feature of the tendinous insertion of the knee extensor muscles, able to alter the moment arm lengths between its input and output tendons, and so modify the mechanical advantage of the knee extensor muscle. However, patellar gearing function is little-explored outside of humans, and the patella is often simplified or ignored in biomechanical models. Here, we investigate patellar gearing and kinematics in the ostrich-frequently used as an animal analogue to human bipedal locomotion and unusual in its possession of two patellae at the knee joint. We use x-ray reconstruction of moving morphology (XROMM) techniques to capture the kinematics of the patellae in an adult ostrich cadaver, passively manipulated in flexion-extension. Moment arm ratios between the input and output tendons of each patella are calculated from kinematically determined centers of patellofemoral joint rotation. Both patellae are found to decrease the mechanical advantage of the extensor muscle-tendon complex, decreasing the tendon output force for a given muscle input force, but potentially increasing the relative speed of knee extension. Mechanically and kinematically, the proximal patella behaves similarly to the single patella of most other species, whereas the distal patella has properties of both a fixed retroarticular process and a moving sesamoid. It is still not clear why ostriches possess two patellae, but we suggest that the configuration in ostriches benefits their rapid locomotion and provides tendon protection., (© 2017 Wiley Periodicals, Inc.)

Background: The anatomy of the first metatarsophalangeal (MTP) joint, particularly the metatarsosesamoid articulation, remains poorly understood. Our goal was to quantitatively define the excursion of the sesamoids., Methods: Seven cadavers were dissected to assess the articulating surfaces throughout a normal range of motion. The dissections were digitally reconstructed in various positions using a MicroScribe., Result: For first MTP joint, excursion averaged 14.7mm for the tibial sesamoid in the sagittal plane and 7.5mm for the fibular sesamoid. The sesamoids also moved medially to laterally when the joint was dorsiflexed. For the maximally dorsiflexed joint, excursion averaged 2.8mm for the tibial sesamoid and 3.5mm for the fibular sesamoid., Conclusion: Hallucal sesamoids appear to have differential tracking: the tibial sesamoid has greater longitudinal excursion; the fibular sesamoid has greater lateral excursion. The anatomical data will interest those involved with the design of an effective hallux arthroplasty., (Copyright © 2014 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.)

The posterolateral corner of the knee accommodating the fabella complex is of importance in orthopaedic surgery. Unfortunately, there is a lack of data in literature for clinical routine. Therefore, we investigated the fabella's characteristics, biomechanical nature, and present histologic details. Of special interest were the fabella's occurrence and position, calcium concentration as long-term load intake indicator, and the histology. Within our analysis, fabellae were found in 30.0% of all datasets, located on the upper part of the posterolateral femoral condyle. The region of fabella contact on this condyle showed a significantly lower calcium concentration than its surroundings. Histologically, the fabella showed no articular cartilage but a clearly distinguishable fabellofibular ligament that consisted of two bundles: one, as already described in literature inserted at the fibular tip, and another part newly described on the top of the lateral meniscus. In its role of stabilizing the soft tissue structures of the posterolateral knee, the fabella seems to serve as suspension for the ligaments evolving from its base. Even though a joint formation of any kind is unlikely, the presence of a fabella needs to be kept in mind during knee examination and any surgical procedures.

Disorders of the hallux sesamoids can be a source of considerable pain and disability. Inappropriate or inept removal can lead to further disability and pain. Surgical intervention should only follow careful accurate assessment, appropriate investigation, and failure of conservative treatments., (Copyright © 2014 Elsevier Inc. All rights reserved.)

It has been hypothesized that diabetic foot ulceration might be internally initiated. This study established a three-dimensional and nonlinear finite element model of a human foot complex with comprehensive skeletal and soft-tissue components. The model was validated by experimental data of subject-specific barefoot plantar pressure measurements. The feasibility of the model to predict the 3D, internal, plantar soft-tissue deformation and stress was evaluated. The preliminary results indicate that large von Mises stress occurs where plantar soft-tissue contacts with geometrically irregular bony structures, thus internal stress distribution within the plantar soft-tissue was dramatically influenced by bony prominences due to stress concentration. At the forefoot part, an average stress magnification factor of 3.01 was quantified. The lateral sesamoid bone associated to the 1st MTH showed the largest effect of stress concentration. The modeling approach presented provides a possible way to explore the complexity of the mechanical environment inside the plantar soft-tissue.

The equine distal forelimb is a common location of injuries related to mechanical overload. In this study, a two-dimensional model of the musculoskeletal system of the region was developed and applied to kinematic and kinetic data from walking and trotting horses. The forces in major tendons and joint reaction forces were calculated. The components of the joint reaction forces caused by wrapping of tendons around sesamoid bones were found to be of similar magnitude to the reaction forces between the long bones at each joint. This finding highlighted the importance of taking into account muscle-tendon wrapping when evaluating joint loading in the equine distal forelimb.

The distal forelimb of the horse has a complex array of ligaments that play a critical role in determining function of the digit and are often associated with the initiation of foot pathologies. The collateral ligaments of the distal sesamoid bone (CLDS) play an important role in digit stabilization near the end of foot contact and there is also limited evidence to suggest that the CLDS stabilize the proximal interphalangeal joint (PIPJ) during weight bearing. By virtue of their anatomical attachments where the ligaments pass dorsal to the axis of rotation of the PIPJ, it is reasonable to assume that the CLDS prevent flexion of the PIPJ during weight bearing or midstance in a moving horse. To test this functional hypothesis, forelimb specimens from three mixed-breed horses were loaded in compression in a materials testing frame. Limb loading was applied with the CLDS intact and following transection. Average PIPJ angle and metacarpophalangeal joint (MCPJ) angle at maximum load (approximately 3000 N) were calculated from angular changes of proximal and middle phalanges and the third metacarpal, which were compared between intact and transected trials. PIPJ angles were found to be the same (175 degrees) at maximum load for intact and transected trials. The proximal and middle phalanges rotated together remaining aligned, regardless of the CLDS condition. Contrary to expectation, however, the combined proximal and middle phalanges unit rotates less relative to the third metacarpal under load after transection, indicating less digit extension at the metacarpophalangeal (fetlock) joint without the influence of CLDS. Since the mechanical properties of the fetlock joint are unchanged by CLDS transection, observed proximal and middle phalanx motion is dependent on increased rotation of the distal phalanx after transection. The original hypothesis was not supported and the results suggest that at midstance the CLDS function primarily to stabilize the articulation of the middle phalanx about the distal phalanx to limit distal interphalangeal joint extension during weight bearing. Establishing the functional role of the CLDS may help to better understand the biomechanical consequences of ligament injuries and diseases of the pastern., (Copyright (c) 2006 Wiley-Liss, Inc.)

Reasons for Performing Study: Proximal sesamoiditis has been a common and confusing radiographic diagnosis in Thoroughbred yearling surveys. This study categorised the radiographic appearance of yearling proximal sesamoid bones and determined their effect on the number of races started and earning potential for racing at ages 2 and 3 years., Hypothesis: Yearlings with moderate to severe proximal sesamoiditis have decreased performance at age 2 and 3 years., Methods: Survey radiographs of 487 Thoroughbred yearlings were reviewed. Proximal sesamoid bones were examined and findings placed into 7 categories, 5 of which measured size, shape, and number of vascular canals, and 2 examined the radiographic shape of the sesamoid abaxial surface. Records of horses age 2 and 3 years were reviewed to obtain the number of races completed and money won in those races., Results: Vascular canals with parallel sides < 2 mm in width in any number were normal. Yearlings with 1 or 2 abnormally conformed vascular canals (nonparallel sides and > 2 mm in width) had a decrease in number of race starts at age 2 years when compared to normal horses. This same change in the fore- or hindlimbs was associated with decreases in starts and earnings at age 2 years. If uniformly present in both fore- and hindlimbs there was no difference from normal horses. Yearlings with > 2 irregular vascular canals had a decrease in number of race starts and earnings at age 2 and 3 years. Changes in proximal sesamoid bone contour did not affect performance., Conclusions: Horses with enlarged vascular canals, within their sesamoids as yearlings, start fewer races and earn less prize money than horses with normal vascular canals., Potential Relevance: One or two enlarged canals affected horses as 2-year-olds. Three or more enlarged vascular canals affected horses at ages 2 and 3 years, which should be taken into account when examining radiographs for potential purchase of young horses.

We test the premise that peak plantar pressure is located directly under the bony prominences in the forefoot region. The right foot of standing volunteers was examined in three different postures by a CT-scanner. The plantar pressure distribution was simultaneously recorded. The position of the metatarsal heads and the sesamoids could be related to the corresponding local peak plantar pressures. The metatarsal heads 1, 4, and 5 had a significantly different position than the local peak plantar pressures. The average difference in distance between the position of the metatarsal heads and the peak plantar pressure showed a significant correlation: on the medial side the head was located more distally to the local peak plantar pressure, on the lateral side more proximally. The findings suggest that normal plantar soft tissue is able to deflect a load. The observations might improve insight into the function of the normal forefoot and might direct further research on the pathological forefoot and on the design of footwear.

The well-developed radial sesamoid bone presented a rod-like shape in the lesser panda. It could be separated into two components: (1) an ulnar cartilaginous, (2) a radial osseous part. The radial sesamoid bone was connected with four elements as follows: (1) the tendon of the M. abductor pollicis longus, (2) M. abductor pollicis brevis and M. opponens pollicis, (3) Aponeurosis palmaris, and (4) Flexor retinaculum. The bone made no articulation with the first metacarpal. The movement of the radial sesamoid bone may be controlled by the connecting muscles and muscle-related structures. It is suggested that the bone acts as a supporting ridge in the gripping action in the lesser panda. However, we suggest that the grasping mechanism is obviously different from that of the giant panda, in which the radial sesamoid bone is connected strongly with the first metacarpal.

Mechanical overload due to poor conformation or shoeing has been suggested to contribute to the development of navicular disease. While studies have determined the compressive force exerted on the navicular bone in normal horses, this has not been reported for horses with navicular disease. Also, the force has not been converted to stress by correction for contact area. In this study we developed a technique for the determination of the contact area between the deep digital flexor tendon and the navicular bone in vivo, and used a forceplate system to determine the force and stress on the bone at trot in 6 normal and eight diseased horses. The mean +/- s.d. peak force and peak stress were 5.62+/-1.45 N/kg and 2.74+/-0.76 MPa for the normal group and 6.97+/-1.50 N/kg and 3.07+/-0.55 MPa for the navicular disease group. The peak force and peak stress were similar for both groups but the force and stress in the horses with navicular disease were approximately double control group values early in the stance phase. This was due to a higher force in the deep digital flexor tendon, which was attributed to a contraction of the deep digital flexor muscle in early stance in an attempt to unload the heels.

As a prerequisite for the identification of navicular disease markers, the concentrations of cartilage oligomeric matrix protein (COMP), total glycosaminoglycans (GAG), hyaluronan, metalloproteinases (MMP) 2 and 9 and total protein were measured in synovial fluid samples obtained from the distal interphalangeal joint (DIP), the metacarpophalangeal joint (MCP) and the navicular bursa of 24 horses. Mean GAG, COMP and total protein levels were significantly higher in the DIP joint and in the navicular bursa compared to the MCP joint. Hyaluronan content was lower. MMP -2 activity was present in all fluids measured and had similar levels in different joints. MMP -9 was present in 42 per cent of MCP joint samples and 58 per cent of DIP joint samples and of navicular bursal samples. In relation to the constituents measured, the composition of navicular bursal fluid was similar to the articular synovial fluids, in particular that obtained from the DIP joint. Correlation between the constituents of DIP joint fluid and navicular bursal fluid obtained from the same legs was statistically significant for all the parameters measured.

Objective: This study compared the mechanical properties of the normal intact suspensory apparatus and two methods of fixation for repair of transverse, midbody fractures of the proximal sesamoid bones of adult horses: transfixation wiring (TW) and screws placed in lag fashion (LS)., Study Design: An in vitro, paired study using equine cadaver limbs mounted in a loading apparatus was used to test the mechanical properties of TW and LS., Animal or Sample Population: Seventeen paired (13 repaired, 4 normal) equine cadaver limbs consisting of the suspensory apparatus third metacarpal bone, and first and second phalanges., Method: The two methods of repair and normal intact specimens were evaluated in single cycle-to-failure loading. Yield failure was defined to occur at the first notable discontinuity (>50 N) in the load-displacement curve, the first visible failure as evident on the videotape, or a change in the slope of the moment-fetlock angle curve. Ultimate failure was defined to occur at the highest load resisted by the specimen. Corresponding resultant force and force per kg of body weight on the suspensory apparatus, fetlock joint moment, and angle of fetlock dorsiflexion were calculated by use of specimen dimensions and applied load. These were compared along with specimen stiffness, and ram displacement., Results: Load on the suspensory apparatus, load on the suspensory apparatus per kg of body weight, moment, applied load, and angle of fetlock dorsiflexion at yield failure were significantly greater for the TW-repaired than for the LS-repaired specimens. A 3 to 5 mm gap was observed before yield failure in most TW-repaired osteotomies., Conclusions: Transfixation wiring provided greater strength to yield failure than screws placed in lag fashion in single cycle load-to-failure mechanical testing of repaired transverse osteotomized specimens of the medial proximal forelimb sesamoid bone.

The objective of this study was to provide a map of cartilage biomechanical properties, thickness, and histomorphometric characteristics in the human, cadaveric first metatarsophangeal joint, to determine if normal articular cartilage was predisposed topographically to biomechanical mismatches in articulating surfaces. Cartilage intrinsic material properties and thickness were obtained from seven pairs of human, freshly frozen, cadaveric, metatarsophalangeal joints using an automated creep indentation apparatus under conditions of biphasic creep. Eight sites were tested: four on the metatarsal head, two on the proximal phalanx base, and one on each sesamoid bone to obtain the aggregate modulus, Poisson's ratio, permeability, shear modulus, and thickness. Cartilage in the lateral phalanx site of the left metatarsal head had the largest aggregate modulus (1.34 MPa), whereas the softest tissue was found in the right medial sesamoid (0.63 MPa). The medial phalanx region of the right joint was the most permeable (4.56 x 10(-15) meter4/Newton-second), whereas the medial sesamoid articulation of the metatarsal head of the left joint was the least permeable (1.26 x 10(-15) meter4/Newton-second). Material properties and thickness are indicative of the tissue's functional environment. The lack of mismatches in cartilage biomechanical properties of the articulating surfaces found in this study may be supportive of clinical observations that early degenerative changes, in the absence of traumatic events, do not occur at the selected test sites in the human first metatarsophalangeal joint.

Ossification of the sesamoid bone of the first finger was studied in left hand-and-wrist X-rays of 296 Czech boys and 272 girls 9 to 15 years old using data collected between 1962 and 1966. The logit and the YES or NO methods were used in treating the data. A sesamoid bone, clearly visible to the naked eye, was considered as positive and when it was not yet visible, as negative. The sesamoid bone was developed in 50 per cent of boys at the age of 13.6 years and in 50 per cent of girls at the age of 11.2 years. This stage preceded the age at onset of menarche in Czech girls by 1.9 years. Boys showed a greater variability (SD = 1.4) than girls (SD = 0.8). Both sexes with clearly visible (ossified) sesamoid bones in their first fingers showed to be, on the average, taller and heavier in comparison with the Czech standard and with those boys and girls of corresponding ages without the sesamoid bone. In contrast to the still continuing secular trend in stature in Czech youths, the age of menarche remained in the last cca 30 years unchanged. In view of the close link between bone age and onset of menarche which remained unchanged for the past 30 years, we may consider our finding as still applicable to present-day adolescents.

Many theories have been advanced concerning the relationship between structure and function in the human foot, yet few of these theories have been subjected to quantitative examination. In this study, foot structure was characterized by 27 measurements taken from standardized lateral and dorsi-plantar weight-bearing plain radiographs of 50 healthy adult subjects. Regional plantar pressure distribution data collected from the same feet were chosen as the functional measures. A stepwise regression analysis was performed to (1) explore what portion of the variance in peak plantar pressure during walking can be explained by the radiographic measurements, and (2) identify structural characteristics of the foot which are significant predictors of peak plantar pressure under the heel and the first metatarsal head (MTH1). Most of the radiographic measurements were highly reliable. However, only 31 and 38% of the variance in peak plantar pressure at the heel and MTH1, respectively, could be explained using multiple regression analyses with the radiographic measurements as independent variables. Among the structural predictors that were identified, soft tissue thickness (e.g. calcaneus or sesamoid heights), and arch-related measurements were the strongest predictors of plantar pressure under both the heel and the first metatarsal head. We conclude that, in normal subjects, only about 35% of the variance in dynamic plantar pressure can be explained by the measurements of foot structure derived from radiographs. This implies that the dynamics of gait are likely to exert the major influences on plantar pressure during walking.

The function of the radial sesamoid bone (RS) in the giant panda (Ailuropoda melanoleuca) was examined by macroscopic study of RS-related bones and muscles. The RS was observed to be connected to the scapholunar and the 1st metacarpal bones. A joint cavity was present between the proximal surface of the RS and the distal area of the scapholunar bone but the RS possessed a fibrous joint connecting it to the proximal radial surface of the 1st metacarpal bone. It is suggested that the RS possesses no substantial abductor-adductor function as the articulation between the RS and the 1st metacarpal bone (FM) seems not to permit flexible movement of the RS. The RS may be a supporting process opposite the digits in the palm when the animal flexes its 5 digits to grip objects, but it is not an active grasping apparatus. In the muscular system, abductor pollicis longus provided strong tendons to the RS as an RS-abductor, whereas the abductor pollicis brevis, opponens pollicis and aponeurosis palmaris were well developed as an RS-adductor muscle group. Observation of RS articulations, however, showed that the muscles do not provide appreciable abduction-adduction actions for the RS.

Radiographic examination of the metacarpo- and metatarsophalangeal joints was performed on 753 Standardbred trotters (6-21 months of age): 21 showed obvious changes in 26 proximal sesamoid bones on lateromedial projection. The radiographic changes were divided into 6 different types: (1) irregular abaxial margin (8 horses); (2) enlargement of the sesamoid bone (6 horses); (3) 'fracture' or separate centre of ossification of the apex (4 horses); (4) vertical, non-articular fracture of the plantar part of the sesamoid bone (1 horse); (5) a small bony fragment located in a defect in the apical part of the bone (2 horses); and (6) multiple areas of decreased radiodensity (1 horse). Each horse displayed only one type of radiographic change except for one which possessed those of types 3 and 5. Follow-up radiographic examination of 21 of the 26 affected proximal sesamoid bones at approximately 6-month intervals revealed a reduction in the changes in 13 bones and an unaltered condition in 8. Lameness examination was performed on 16 of the 21 horses at 3 years of age and 14 (87.5%) were observed to be lame, but detected lameness did not seem to be referrable to the sesamoid changes. Earnings after the racing season as 3- and 4-year-old horses showed no differences (P > 0.05) between horses with radiographic changes in the proximal sesamoid bones and those without such changes.

Extensive research has been done on disorders of the sesamoid bone of the hallux. However, reports on the mechanism of the disorder are few and a comprehensive assessment of the biomechanical role played by the sesamoid bone has not been done. In an effort to elucidate the role of the sesamoid bone, we have developed a force sensor which utilizes the capacitance method, and evaluated the biomechanical aspects of fatigue fracture associated with it. Three frozen stored human limbs were thawed at room temperature. The force between the sesamoid bone and the first metatarsal head was measured using force sensors which were placed on the bilateral sesamoid bones. Measurements were also taken at varying loads and angles of dorsiflexion of the MTP (metatarsophalangeal) joint of the hallux from 0 degrees to 60 degrees at increments of 10 degrees. This was done by applying weights ranging from 0 to 4 kg to the first metatarsal head at increments of 1 kg. Load and angle of dorsiflexion of the MTP joint were found to be correlated with the degree of compression force between the hallux sesamoid bone and the first metatarsal head; the load applied affected the force to a greater extent than did the angle. Dorsiflexion of the MTP joint of the hallux had no effect on the amount of compression force between the medial and lateral sesamoid bones, but the increase in compression force became pronounced when the angle of dorsiflexion exceeded 30 degrees.

Eight untrained 2-year-old Thoroughbred horses were used in a study of the remodeling response of the proximal sesamoid bone (PSB) to training-related stimuli. Two horses each were assigned to 1 of 4 groups: group 1, untrained, pasture turnout (control); group 2, modified-classically trained, dirt track; group 3, classically trained, dirt track; and group 4, classically trained, wood chip track. Horses were given fluorochromic bone labels every 28 days during training. All horses were euthanatized after 5 months of training, and the proximal sesamoid bones (PSB) were removed. A midsagittal section of bone 85- to 95-microns thick was prepared for histomorphometric analysis by use of computerized image analysis and epifluorescent microscopy. Porosity (percent), trabecular width (micrometer), extent of anisotropy (percent), mineralizing surface (percent), fractional mineralizing surface (percent), and mineral apposition rate (micrometers per day) were determined at 5 circular regions of each specimen. Region 1 was located within the apex of the PSB, regions 2, 3, and 4 were subjacent to the subchondral plate, and region 5 was within the basilar articular margin. Data were pooled to allow comparison by training group and by region. The PSB from horses trained on dirt tracks (groups 2 and 3) had significantly (P less than 0.05) lower porosities and greater trabecular width, compared with the control group. The PSB from all training group specimens had significantly larger mineralizing surfaces than control group specimens. The fractional mineralizing surface revealed a rapid and vigorous response of the endosteal surface of the PSB in horses trained on dirt tracks.(ABSTRACT TRUNCATED AT 250 WORDS)

First metatarsophalangeal (MTP) joint reaction forces were calculated for 11 normal females during the toe-off phase of gait while walking in bare feet and in high heeled shoes. A biomechanical model was used to calculate the forces utilizing kinematic, kinetic, footprint, and radiographic data. The results showed that the MTP joint reaction forces (FJ), the metatarsal-sesamoid forces (FS), and the resultant of these forces (FRES), were twice as large in high heels compared to barefoot walking. The average peak forces for barefoot and high-heeled gait were FJ: 0.8 and 1.58 times body weight, FS: 0.44 and 1.03 times body weight, and FRES: 0.93 and 1.88 times body weight. Also, the kinematics changed when wearing high heels, making angles of application of forces and sesamoidal articulations less favorable.

The authors undertake an anatomical study of the sesamoid apparatus to determine its mechanical functions. The intersesamoid ligament is of particular interest, since its functions are diverse and complex. The sesamoid apparatus appears to coordinate the various forces that converge upon the forefoot into the great toe. The apparatus then seems to form part of a catapult that assists propulsion.

Serial data from cephalometric radiographs were analyzed for 34 boys and 33 girls who had cephalometric radiographs annually near each birthday from at least age 7 through 18 years. Spurts were defined for this study as increases between successive cranial base increments that exceeded 0.75mm/year in boys or 0.5mm/year in girls. The corresponding criterion for the mandible was 1.0mm/year in either sex. Pubescence was defined as the 4- year period spanning 2 years before and after peak height velocity. Spurts during pubescence were common, tending to occur about 1.6yr earlier in girls than boys. The mean increments at first pubertal spurt (FPS) and the mean sizes of FPS were about 25% to 33% greater in the boys than in the girls. The rate of growth during the year before FPS tended to be greater in the girls, while in the year after FPS it tended to be greater in the boys. The timing of FPS in either cranial base of mandible was not closely related to the onset of ossification in the ulnar sesamoid, the age at peak height velocity, or age at menarche. FPS generally occurred after the onset of ossification of the ulnar sesamoid, but before peak height velocity and menarche. There was no evidence of difference between craniofacial EPS in children who passed rapidly or slowly through pubescence, nor was any difference noted between the size of pubertal spurts in tall or short boys. larger total increments after peak height velocity were found in the short boys. Significant correlations were identified between the cranial base and the mandible in the timing but not in the magnitude of FPS. The children were approximately equally divided between those in whom cranial base spurts occurred first, those in whom mandibular spurts were first, and those in whom FPS occurred in both areas within the same annual interval.

Forty-eight limbs of 12 freshly euthanized horses were used to generate data on the strength of the equine suspensory apparatus. The point of failure of the suspensory apparatus of each limb was determined. Immediately before euthanasia, 6 of the 12 horses (thoroughbreds and standardbreds) had been engaged in active training or racing, and six horses in stall and/or pasture activity. In the actively training or racing horses, the point of acute failure of the suspensory apparatus was within the proximal sesamoid bones in 20 (83%) limbs (resulting in 17 apical fractures, 2 basilar fractures, and 1 midbody fracture). In the pasture exercised or stalled horses, the point of failure of the suspensory apparatus was either acutely within the suspensory ligament (10 horses, 42%) or, if no acute failure occurred, insidiously within the suspensory ligament (12 horses, 50%). Active training appeared to have a strengthening effect on the suspensory ligament, causing the weakest point in the suspensory apparatus to become the sesamoid bones rather than the suspensory ligament. An average force of 1338 kg (between 1082 and 1673 kg) was needed to fail the suspensory apparatus in this group of horses. In nontraining horses, the site of failure was most often the suspensory ligament. An average force of 1100 kg (between 918 and 1241 kg) used to fail the suspensory apparatus in this group of horses was significantly (p less than 0.5) less than in the first group.