Anatomy and pathology of the sesamoid bones. The hand compared to the foot

Diagnosis, imaging, and potential morbidities of the hallux interphalangeal joint os interphalangeus

Hallux pain is a common entity with a differential diagnoses including hallux valgus, hallux limitus/rigidus, and gout and specifically at the interphalangeal joint (IPJ), flexor hallucis longus (FHL) tenosynovitis, and joint arthrosis. An under-recognized source of pain is the os interphalangeus, an ossicle typically located at the plantar aspect of the hallucal interphalangeal joint. This ossicle is radiographically visible in its ossified form in 2-13% of individuals, but can also be present as an ossified or non-ossified nodule in patients. The os interphalangeus may be centrally or eccentrically located, and although originally believed to be a sesamoid bone in the FHL tendon, it is an ossicle located in the joint capsule of the IPJ and separated from the tendon by a bursa. When the ossicle is absent, the bursa is also absent and the tendon is attached to the joint capsule. Infrequently, the os may be located eccentrically under the first IPJ and reflect persistence of one of the distal phalanx. Rarely, the os interphalangeus may be dorsal to the IPJ. The os interphalangeus is best evaluated on radiographs, ultrasound, and MRI. Pain is a result of altered mechanics with arthrosis or frictional effects with bursitis, tenosynovitis, or intractable plantar keratosis (IPK). The ossicle may also displace into a dislocated IPJ, preventing reduction. The os interphalangeus may be centrally or eccentrically located, and although originally believed to be a sesamoid bone. This has been found within the plantar joint capsule of the distal hallucal interphalangeal joint and separated from the tendon by a bursa. Uncommonly, the location may be plantar eccentric and reflect persistence of one of the ossification centers of the distal phalanx. Although the ossicle can be imaged with standard AP and lateral radiographs in many cases, in those cases of unexplained pain with no radiographically visible ossicle, and the presence of friction blisters, intractable plantar keratosis (IPK), hyper-extension of the IPJ, hallux limitus/rigidus, or metatarsophalangeal joint (MTPJ) arthrodesis, an MRI or CT should be considered to identify a non-ossified fibrocartilaginous node. This is of particular concern in a patient with a history of underling diabetes mellitus or other metabolic disorders associated with diminished pedal sensation where neurotrophic changes place them most at risk for complications associated with excessive plantar pressure. Pain is a result of altered biomechanics with arthrosis, or frictional effects causing bursitis, tenosynovitis, or IPK. The ossicle may also displace into a dislocated IPJ, preventing reduction. In this article, we will describe the anatomy and imaging appearance of the common os interphalangeus variants and associated complications including frictional effects, arthrosis, and IPK and discuss conservative and surgical management of a symptomatic ossicle.

Sesamoid bones of the hand: A multicenter study

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.

Sesamoids in tetrapods: the origin of new skeletal morphologies

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.

Accessory Lesser Metatarsal Sesamoids in All of the Metatarsophalangeal JointsA Case Report

Lesser metatarsal sesamoids are one of the most common accessory bones of the foot and are most commonly seen at the fifth metatarsophalangeal joint. They are rarely seen in other metatarsophalangeal joints. In the literature, there are reports of solitary accessory sesamoid bones seen at lesser metatarsophalangeal joints. We report the case of a 68-year-old woman with lesser metatarsal sesamoids accompanying all of the metatarsophalangeal joints.

Distribution patterns and coincidence of sesamoid bones at metatarsophalangeal joints

PURPOSE

Our aim was to identify the incidence and distribution of sesamoid bones plantar to the metatarsophalangeal (MTP) joints in adults, and to evaluate patterns of coincidence among these sesamoid bones.

METHODS

We conducted a retrospective review of 7949 plain radiographs obtained from patients evaluated for foot trauma or symptomology. Associations between the distributions of MTP sesamoid bones as well as the association of age, sex, and laterality with identified prevalence, distribution, and coincidence were evaluated using Spearman's correlation coefficient.

RESULTS

Overall, 17,060 sesamoid bones were identified for 9005 MTP joints, with 16 distinctive distribution patterns. Among possible patterns, we identified a prevalence rate of complete absence of MTP sesamoid of 0.04 %, of a single sesamoid at the hallux of 89.08 % of radiographs; and of sesamoid at ≥2 MTP joints of 10.88 %. The presence of a sesamoid at the hallux was consistent, and was not correlated with the presence or absence of a sesamoid bone at one of the other MTP joints (P > 0.05). However, there was a positive correlation between the presence and absence of sesamoid bones at any two of the other four MTP joints (P < 0.001). Age was positively correlated with both the total number of sesamoids present (P < 0.001) and the number of MTP joints with sesamoids (P < 0.001).

CONCLUSIONS

Information from this study would assist clinicians in the diagnosis of patients presenting with pain and discomfort of the foot after trauma and overuse, as well as contribute a robust data set for research in forensic science and anthropology.

The sesamoids of the feet in humans: a systematic review and meta-analysis

The prevalence and distribution of the sesamoid bones in the feet has been reported in the literature with a high degree of variability. This systematic review aims to provide a better estimate of the frequency of the sesamoids of the foot and their association with variables such as ancestry, gender, and side. Thirty-seven studies met the inclusion criteria and were submitted for meta-analyses, sensitivity analyses and proportion difference tests, whenever possible. At the metatarsophalangeal (MTP) joint of the hallux, sesamoids were nearly always present. At the interphalangeal (IP) joint, the pooled true estimates of large-sampled studies were: (1) an overall prevalence of 22.4 %, (2) a cadaveric rate at 71.6 %, and (3) a radiological rate (based on X-ray images) of 21.1 %. The pooled partition frequencies of the hallucal medial and lateral sesamoids were 10.7 and 1.3 %, respectively. Bipartism was the most frequent partition type (92 %), followed by tripartism (7.5 %) and quadripartism (0.5 %). Middle Eastern ancestry was associated with significantly lower hallucal partition rate (P < 0.0001) and African ancestry with significantly lower prevalence of the IP sesamoid than all other ethnicities (P < 0.001). Feet with a hallux valgus deformity seemed to be associated with significantly higher rate of partition of the medial sesamoid (odds ratio = 3) than that of the normal feet. The respective values of the pooled true prevalence in adults at the MTP joint for the 2nd, 3rd, 4th and 5th toes were 1.9, 0.32, 0.9 and 13 %, respectively. There was a significantly higher prevalence of tibial sesamoids vs lateral sesamoids, with pooled odds ratio of 34.7, 8, 4.8, and 2.27, respectively. Partition was found in around 10 % of the sesamoids of the 5th MTP joint; no partition was noted in the other toes. For most 2nd-5th MTP joints, European ancestry showed the highest frequency whereas African ancestry showed the lowest; Middle Eastern ancestry was in between. No sesamoids were found at the 4th proximal IP joint and at the 4th and 5th distal IP joints. No sesamoids were found at any IP joint in the feet of Middle Eastern and African populations. The pooled rates of the IP sesamoids of the second and third toes in European populations were 1.2 % for the 2nd proximal, 0.33 % for the second distal and 0.6 % for both IP joints of the third toe. This anatomical meta-analysis yielded results that are likely to be more accurate regarding the rates of the sesamoids in the foot, their laterality and partition. It also provided solid evidence for the genetic basis of the frequency distribution among the different populations.

The prevalence of the sesamoid bones of the hand: a systematic review and meta-analysis

The literature contains various estimates of the prevalence and distribution of the sesamoid bones in the hands. The aims of this systematic review are to provide a better estimate of the frequency of hand sesamoids and its association with variables such as ancestry, gender, and side. Nineteen studies met the inclusion criteria. The pooled rates of the sensitive meta-analyses from large-sample studies in adults showed: (a) true overall rates of 99.9% for the metacarpophalangeal (MCP) joint of the thumb (MCP-I), 53% for the interphalangeal joint (IP-I), 43.4% for the MCP of the index (MCP-II), 1.47% for the MCP of the medius finger (MCP-III), 0.6% for the MCP of the ring finger (MCP-IV), and 67.7% for the MCP of the auricular finger (MCP-V); (b) true radiological rates of 99.9% for the radial thumb sesamoid, 99.6% for the ulnar thumb sesamoid, 47.8% for IP-I, 40% for MCP-II, 1.3% for MCP-III, 0.8% for MCP-VI, and 62.8% for MCP-V. Black, Middle Eastern, and European ancestries conferred significantly higher sesamoid frequencies at IP-I, MCP-II, and MCP-V, respectively. There was a significant association with female gender at MCP-II, MCP-IV, and MCP-V, with ORs of 1.53, 4, and 1.3, respectively, and a nonsignificant "female" trend for the other locations. There was no significant association with hand side. The pooled rates of hand sesamoids in children aged 10-17 years were 92.7, 42.2, 33.8, 0.5, 0.3, and 36.5% for MCP-I, IP-I, MCP-II, MCP-III, MCP-IV, and MCP-V, respectively. The findings of this evidence-based anatomical review provide quantitative evidence that the incidence of sesamoid bones in human hands depends on genetic rather than functional factors.

Prevalence of accessory ossicles and sesamoid bones in hallux valgus

BACKGROUND

Sesamoid bones and accessory ossicles of the foot and ankle, although mostly asymptomatic, can be sources of pain or degenerative changes in response to overuse and trauma. We investigated the prevalence of accessory ossicles and sesamoid bones in a population of Italian women with hallux valgus.

METHODS

A single-center study was performed to determine the prevalence of accessory ossicles and sesamoid bones in the ankle and foot. A total of 505 women with hallux valgus aged 26 to 80 years at the time of hallux valgus correction were examined. Anteroposterior, oblique, lateral foot radiographs and a Muller view were examined regarding the presence, prevalence, coexistence, and distribution of accessory ossicles and sesamoid bones in both feet. The radiographs were analyzed independently by three experienced specialists in foot and ankle surgery. Disagreements were discussed in a consensus meeting, where the radiographs were reevaluated and a final decision was made.

RESULTS

There was no statistically significant difference between data of the accessory ossicles and sesamoid bones according to the χ(2) test. Sesamoid bones were detected in 404 of the 505 patients. The fifth metatarsal sesamoid bone was found in 97 patients. All of the patients presented hallucal sesamoid bones.

CONCLUSIONS

This is the first detailed report of the prevalence of accessory ossicles and sesamoid bones of the feet in Italian women with hallux valgus. These findings could help clinicians in the diagnosis and management of disorders of accessory ossicles and sesamoid bones, which are often undiagnosed, painful foot syndromes.

Fractures of the lesser sesamoids: case series

We present 3 cases of sesamoid fractures involving the index, ring, and little finger metacarpophalangeal joints. These injuries present similar to more common sprains of the finger metacarpophalangeal joint and may be difficult at times to appreciate on standard posteroanterior and lateral x-rays. Oblique images can aid in making the diagnosis at times. Whereas we still recommend immobilization as the initial treatment for these injuries, all 3 of our cases failed nonoperative management and eventually required sesamoid excision.

Long-term results using a treatment algorithm for chronic sesamoiditis of the thumb metacarpophalangeal joint

PURPOSE

We report a series of 18 patients with chronic sesamoiditis of the metacarpophalangeal joint of the thumb treated in the period from 1997 to 2002. We describe a diagnostic clinical test (sesamoid provocation test [SPT]) and present the long-term results of the senior author's treatment algorithm.

METHODS

The study included 20 thumbs in 18 patients (8 men and 10 women) with an average age of 36 years. The mean duration of symptoms at initial presentation was 6 months. The dominant thumb was symptomatic in 80% of patients, and 30% of patients gave history of prior trauma. The diagnosis was made clinically and aided by the SPT. Radiographs were normal in 65% of thumbs. The treatment algorithm consisted of steroid injection(s) into the subsesamoid joint. Sesamoidectomy was reserved for patients who were symptomatic (visual analog pain score ≥ 3) after 2 steroid injections. The patients were contacted by telephone in 2010 for an assessment of long-term results.

RESULTS

Eight thumbs improved with a single steroid injection whereas 5 thumbs required a second steroid injection. Of the 6 thumbs that underwent sesamoidectomy, 1 required secondary surgery for recurrent symptoms. At long-term follow-up (average, 9 y), 1 patient, who had declined sesamoidectomy, continued to have persistent pain affecting thumb function.

CONCLUSIONS

Previous reports have suggested that nonoperative treatment is not effective in the management of chronic sesamoiditis. We found that steroid injections were an acceptable treatment modality with long-lasting results. Failures can be successfully treated with sesamoidectomy.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Prevalence of sesamoid bones in the interphalangeal joint of the thumb and fingers: a radiographic study

The prevalence of sesamoid bones in the hands has been reported in some previous articles. Most of them, however, have reported sesamoid bones of the metacarpophalangeal joint of the hand and of the interphalangeal (IP) joint of the thumb. The present study investigates the prevalence of sesamoid bones of the IP joint of the thumb and fingers. A retrospective review of radiologic views of the IP joints in the thumb or fingers was performed, including a total of 650 patients (1,096 thumbs or fingers). Sesamoid bones were found in the IP joint of the thumb at 67% (212 of 318), while the index, middle, ring, little fingers had sesamoid bones in the proximal interphlangeal (PIP) joint at 0% (0 of 172), 0.4% (1 of 244), 0.5% (1 of 183), and 1% (2 of 179), respectively. None of the four fingers had sesamoid bones in the distal IP joint. Previous articles have described the similar prevalence to the present study, of sesamoid bones of the IP joint of the thumb, while some others reported the different prevalence. About the PIP joint, no previous articles have found a sesamoid bone. Because the lateral X-ray view is more accurate and suitable to evaluate sesamoid bones, we used the lateral one for the present study. The knowledge that sesamoid bones occurs at these rates in the thumb IP joint and finger PIP joints is helpful to differentiate chip fractures from sesamoid bones near the IP joint, including the PIP joint.

Sesamoid arthritis mimicking trigger thumb

This article presents a case of undiagnosed sesamoid arthritis with coexisting trigger thumb. A 25-year-old woman presented with a 2-year history of metacarpophalangeal joint pain and triggering of the thumb. She was a right-handed bank employee and recalled a trivial thumb sprain. The pain improved slightly while on medication, but the triggering recurred 1 month after the steroid injection. Six months after the first visit, she underwent A1 pulley release surgery for the triggering without a more detailed evaluation such as radiographs or sonographs. Intraoperatively, no definite abnormalities in the fibrous flexor sheath or flexor tendon were observed. The triggering resolved, but the pain persisted. One month postoperatively, a repeat physical examination was performed, and the painful region was localized to the radial sesamoid area. Radiography was then performed, which showed joint space narrowing of the sesamoid metacarpal head and sclerotic changes and spur formation on the metacarpal head. An additional diagnosis of sesamoid arthritis of the thumb was made and the pain finally resolved as a result of the sesamoidectomy. Orthopedic surgeons often overlook pathologies around the metacarpophalangeal joint, especially those related to triggering. A high index of suspicion and clinical findings consistent with intermittent mechanical obstruction and tenderness in the palmar aspect of the metacarpophalangeal joint warrant inclusion of sesamoid arthritis as a differential diagnosis for metacarpophalangeal joint pathology. Detailed physical examinations should be performed and proper radiographs taken in all patients with tenderness in the metacarpophalangeal joint even if triggering of the thumb is present.

Sesamoid and accessory bones of the hand--an epidemiologic survey in a Mediterranean population

The prevalence and distribution of sesamoid and accessory bones in the hands is quite variable between different populations and ethnic groups. However, there are no published data on their distribution in Mediterranean populations. Studies on the validity of radiographic assessment for the presence of these bones are also lacking. A retrospective review of 442 radiographs of adult patients was performed in order to assess the incidence of sesamoid and accessory bones in the hands of a Mediterranean population. Additionally, two independent observers reviewed 174 radiographs and used the Kappa parameter in order to assess the validity of radiographic interpretation of radiographs for the presence of those bones. There was an incidence of 99.5% sesamoid bones (n = 440) in the 1st metacarpophalangeal (MCP) joint, 42.3% in the 2nd MCP joint (n = 187), and 41.1% (n = 182) in the 5th MCP joint. The incidence in the 1st interphalangeal joints was 26.2% (n = 116). The incidence of sesamoid bones in the 1st, 2nd, and 5th metacarpophalangeal joints in a Mediterranean population was found to be similar to that of Arab and Caucasian populations, whereas their prevalence in the 1st interphalageal joint coincided more with Arab populations. Interobserver reliability of the interpretation of radiographs for the presence of sesamoid bones in the hand was good (Kappa > 0.68) in all locations, except for the 1st MCP joint. Further research is warranted to further elucidate the genetic and/or environmental reasons for the differences between those populations.

Murine metapodophalangeal sesamoid bones: morphology and potential means of mineralization underlying function

Normal murine metapodophalangeal sesamoid bones, closely associated with tendons, were examined in terms of their structure and mineralization with reference to their potential function following crystal deposition. This study utilized radiography, whole mount staining, histology, and conventional electron microscopy to establish a maturation timeline of mineral formation in 1- to 6-week-old metapodophalangeal sesamoids from CD-1 mice. An intimate cellular and structural relationship was documented in more detail than previously described between the sesamoid bone, tendon, and fibrocartilage enthesis at the metapodophalangeal joint. Sesamoid calcification began in 1-week lateral sesamoids of the murine metacarpophalangeal joint of the second digit. All sesamoids were completely calcified by 4 weeks. Transmission electron microscopy of 2-week metacarpophalangeal sesamoids revealed extensive Type I collagen in the associated tendon and fibrocartilage insertion sites and Type II collagen and proteoglycan networks in the interior of the sesamoid. No extracellular matrix vesicles were documented. The results demonstrate that murine sesamoid bones consist of cartilage elaborated by chondrocytes that predominantly synthesize and secrete Type II collagen and proteoglycan. Type II collagen and proteoglycans appear responsible for the onset and progression of mineral formation in this tissue. These data contribute to new understanding of the biochemistry, ultrastructure, and mineralization of sesamoids in relation to other bones and calcifying cartilage and tendon of vertebrates. They also reflect on the potentially important but currently uncertain function of sesamoids as serving as a fulcrum point along a tendon, foreshortening its length and altering advantageously its biomechanical properties with respect to tendon-muscle interaction.

Distribution of the metatarsophalangeal sesamoids in Turkish subjects

No statistically significant pattern of metatarsophalangeal sesamoid distribution has been reported in the literature in relation to genetic pool or group, unilaterality or bilaterality, or sesamoid division. A study was undertaken to evaluate the presence and distribution of the metatarsophalangeal sesamoid bones of the foot in Turkish subjects. A total of 602 foot radiographs from 371 patients without forefoot complaints other than those of the hallux were included in the study. Absence or hypoplasia of the first-ray sesamoids was seen on 0.7% of the radiographs, and second-, third-, fourth-, and fifth-ray sesamoids were present on 2.8%, 0.5%, 1.0%, and 15.1% of the radiographs, respectively. Fifth-ray sesamoids were more prevalent in men (odds ratio, 2.71; 95% confidence interval, 1.52-4.84). The frequency of a normal foot profile (two sesamoids in the first ray) was 83.2%. Divisions of the sesamoids were seen on 4.0% of the radiographs at the first ray and on 20.9% at the fifth ray. Distribution and division of sesamoids were predominantly bilateral (kappa = 0.91, 0.91, and 0.95 for the first, second, and fifth digits, respectively; P < .001).

Complex dislocation with double sesamoid entrapment of the interphalangeal joint of the hallux

A 23-year-old soccer player presented with a traumatic complex dislocation of the interphalangeal joint of the hallux with intraarticular entrapment of 2 sesamoid bones. Successful closed reduction was undertaken with excellent recovery of toe function.

Pathologie par fragmentation du sésamoïde de l'index dans le cadre de microtraumatismes répétés : à propos d'un cas et revue de la littérature

Pathology of the sesamoid bones have been rarely described in the literature especially those of the index. We present the case of a 45 years old amateur tennis player who presented with pain on the radial border of the index finger at the level of the metacarpophalangeal joint. The clinical examination and the operative findings allow us to conclude that the symptoms were due to tendinitis of the flexors of the index associated with fracture of the sesamoid and cartilaginous degenerative changes. We also present a review of the literature.

Mechanical induction in limb morphogenesis: the role of growth-generated strains and pressures

Morphogenesis is regulated by intrinsic factors within cells and by inductive signals transmitted through direct contact, diffusible molecules, and gap junctions. In addition, connected tissues growing at different rates necessarily generate complicated distributions of physical deformations (strains) and pressures. In this Perspective we present the hypothesis that growth-generated strains and pressures in developing tissues regulate morphogenesis throughout development. We propose that these local mechanical cues influence morphogenesis by: (1) modulating growth rates; (2) modulating tissue differentiation; (3) influencing the direction of growth; and (4) deforming tissues. It is in this context that we review concepts and experiments of cell signaling and gene expression in various mechanical environments. Tissue and organ culture experiments are interpreted in light of the developmental events associated with the growth of the limb buds and provide initial support for the presence and morphological importance of growth-generated strains and pressures. The concepts presented are used to suggest future lines of research that may give rise to a more integrated mechanobiological view of early embryonic musculoskeletal morphogenesis.

Sesamoiditis of the index finger presenting as acute suppurative flexor tenosynovitis

Sesamoiditis involving the hand is uncommon, usually reported in the thumb, and has not been reported in the index finger. As rare as this clinical entity remains, its presentation simulating an acute suppurative flexor tenosynovitis is even more rare. We report a patient who presented with Kanavel's 4 cardinal signs of acute suppurative tenosynovitis who was subsequently found to have an acute sesamoiditis of the index finger. This finding was supplemented by a cadaveric and radiographic study to better delineate the anatomy of the index sesamoid and further explain the clinical presentation.

Coincident development of sesamoid bones and clues to their evolution

Sesamoid bones form within tendons in regions that wrap around bony prominences. They are common in humans but variable in number. Sesamoid development is mediated epigenetically by local mechanical forces associated with skeletal geometry, posture, and muscular activity. In this article we review the literature on sesamoids and explore the question of genetic control of sesamoid development. Examination of radiographs of 112 people demonstrated that the relatively infrequent appearances of the fabella (in the lateral gastrocnemius tendon of the knee) and os peroneum (in the peroneus longus tendon of the foot) are related within individuals (P < 0.01). This finding suggests that the tendency to form sesamoids may be linked to intrinsic genetic factors. Evolutionary character analyses suggest that the formation of these sesamoids in humans may be a consequence of phylogeny. These observations indicate that variations of intrinsic factors may interact with extrinsic mechanobiological factors to influence sesamoid development and evolution.

Hyperextension injuries of the MP joint of the thumb

We report 26 cases of hyperextension injury of the MP joint of the thumb. These were classified into the following three categories; dorsal dislocation of the MP joint or volar plate avulsion; locking of the MP joint and fracture of the sesamoid bone. We report the pathomechanics and clinical features of these injuries.

The blood supply to the great toe sesamoids

The purpose of this study was to define the intraosseous and extraosseous blood supply of the hallucal sesamoids by studying a total of 10 fresh-frozen, below-knee specimens with no evidence of vascular disease. Most specimens were injected with high grade India ink, cleared using a standard Spalteholz technique, and processed to delineate the extraosseous and intraosseous blood supply to include soft tissue dissection and coronal sectioning. Two additional specimens were injected with blue Mercox acrylic solution to further define the extraosseous vasculature. The major extraosseous blood supply to the sesamoids is via the posterior tibial artery. This vessel then branches into the medial plantar artery which further divides upon entering the medial and lateral sesamoids in their proximal poles. Vessels in the peripheral soft tissues, although abundant, do not seem to penetrate the cortex of the sesamoids. The intraosseous blood supply to the sesamoids seems to be threefold. Mainly, sesamoid arteries enter the lateral and medial sesamoids from the proximal aspect via a single vessel. This proximal vessel proceeds distally with a network of branching. Plantar, nonarticular vessels enter the sesamoids, constituting a second source of vascularity. Finally, small vessels also enter the sesamoids through medial and lateral capsular attachments. Based on this study, a possible explanation for avascular necrosis and nonunion of sesamoids is proposed, and an optimal surgical approach is discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

Morphometric analysis of the plantar plate apparatus of the first metatarsophalangeal joint

Reliable and reproducible radiographic assessment of plantar plate integrity of the great toe is possible with standard radiographic techniques. Normal values in 100 pairs of feet (200 feet) are defined for comparison of one foot to the other and absolute values emerge if comparison is not possible. Bipartite sesamoids occurred in 13.5% of 200 feet with a 37% bilaterality.

The Sesamoids of the Metacarpo-Phalangeal Joint of the Thumb: An Anatomical and Clinical Study

Two unusual cases of injury to the sesamoids of the M.P. joint of the thumb are described. An anatomical dissection of the M.P. volar plate region, including the sesamoids, was undertaken to delineate the details of the sesamoids’ relationship to the M.P. joint, flexor tendon, flexor tendon sheath and capsule of the joint. Histological studies were carried out to demonstrate a tendinous extension of the muscles that attach to the sesamoids.