Separate Centres Of Ossification Research Articles

Bipartitism in Tarsal Bones: A Retrospective Analysis of Clinical and Radiological Features

Background: Bipartitism in the foot, especially in the tarsal bones, is a rare anatomical variant characterised by dividing one bone into two separate ossification centers. This condition can be congenital or acquired, often remains asymptomatic, and is only discovered incidentally during radiological imaging. This study aims to present a comprehensive retrospective analysis of bipartitism in tarsal bones, assessing its prevalence, type of articulation and associated clinical features in a cohort of patients. Methods: A total of 4,645 patients were retrospectively evaluated from 6,145-foot images consisting of 4,975 computed tomography (CT) and 1,170 magnetic resonance imaging (MRI) scans obtained between 2015 and 2023. 15 patients with tarsal bipartitism were identified and contacted through the hospital system for in-person medical history and examination. Radiological exams assessed partial and complete bipartition, diastasis, and exostosis in the tarsal bones. Age, sex, side, trauma history, pain, foot deformity, gait disturbance, and other clinical findings were also recorded. Results: Bipartitism was detected in 15 patients (0.32%), predominantly affecting males (87%). The most common variant was medial cuneiform bipartitism, observed in 13 patients (0.28%). Talus and calcaneus bipartitism were each observed in one patient (0.02%). Bilateral involvement was present in 67% of the cases, with 60% of patients reporting chronic pain. Complete dissociation of bipartite bones was noted in 80% of cases. Accompanying bipartitism, two patients had pes planovalgus, and one had hallux varus deformity. Conclusion: Although bipartitism of the tarsal bones is rare, it remains a diagnostic challenge due to variability in clinical presentation and possible association with other foot deformities. Accurate diagnosis through advanced imaging techniques is essential to differentiate these variants from fractures and guide appropriate treatment. This study contributes valuable insights into the prevalence and clinical impact of bipartitism in the tarsal bones, emphasising the importance of early diagnosis and individualised treatment strategies.

Intravertebral vs. intervertebral integration and modularity in the vertebral column of mammalian carnivorans.

The vertebral column is a multicomponent structure whose organization results from developmental and functional demands. According to their distinct somitic origins, individual vertebrae exhibit intravertebral modularity between the centrum and neural spine. However, vertebrae are also organized into larger units called intervertebral modules that result from integration between adjacent vertebrae due to locomotory demands or from common developmental origins due to resegmentation. A previous hypothesis suggested that the boundaries of intervertebral modules coincide with changes in the patterns of intravertebral integration. Here, we explicitly test whether the patterns of modularity and integration between the centrum and neural spine (i.e., intravertebral) in the boundary vertebrae among previously defined intervertebral modules change with respect to those in the vertebrae within intervertebral modules. We quantified intravertebral modularity patterns and quantified the strength of intravertebral integration for each vertebra of the presacral region in 41 species of carnivoran mammals using 3D geometric morphometrics. Our results demonstrate a significant intravertebral modular signal between the centrum and neural spine in all post-cervical vertebrae, including the boundary vertebrae among intervertebral modules. However, the strength of intravertebral integration decreases at the boundary vertebrae. We also found a significant correlation between the degree of intravertebral integration and intervertebral integration. Following our results, we hypothesize that natural selection does not override the integration between the centrum and neural spine at the boundary vertebrae, a pattern that should be influenced by their distinct somitic origins and separate ossification centers during early development. However, natural selection has probably influenced (albeit indirectly) the integration between the centrum and neural spine in the vertebrae that compose the intervertebral modules.

Correlated Imaging of the Equine Hyoid Apparatus Using CT, Micro-CT, and Histology.

Background: Detailed radiological evaluation of the normal hyoid apparatus by computed tomography (CT) has not yet been conducted. Thus, it is unclear what type of junction connects the different parts of the equine hyoid apparatus.Objectives: To describe the normal CT anatomy of the equine hyoid apparatus, and to determine the junction type that connects the different parts of the hyoid apparatus.Study Design: Combination of retrospective study and prospective cadaver study.Methods: The medical records of horses that underwent head CT scans from 2009 to 2018 were retrieved. Inclusion criteria for the CT scans were visibility of at least two of the four junctions of the hyoid apparatus. CT images were analyzed in three different planes. Additionally, 10 cadaver heads were processed using CT, micro-CT of selected joints, and histology of all joints.Results: CT scans of 200 horses fulfilled the inclusion criteria. The tympanohyoid cartilage consisted of hyaline cartilage. Areas of mineralization within the cartilage were visible on CT scans as early as 2 years of age. The epihyoid was not fused with the stylohyoid in one-third of the horses. All horses younger than 2.5 years showed three ossification centers of the basihyoid, and all horses younger than 1.5 years had a non-fullydeveloped lingual process. In total, 10 of 11 horses between 1.5 and 3 years had separate ossification centers of the lingual process. We found a synchondrosis between the styloid process and the stylohyoid bone. The basihyoid and thyrohyoid, as well as the stylohyoid and epiyhoid were connected by a synostosis in two-thirds of the horses. The remaining parts were connected to one another by synovial joints.Main limitations: The junctions studied by histologic examination were from older horses, therefore growing patterns of different bones could not be totally clarified.Conclusion: The temporohyoid joint is a synchondrosis. The epihyoid is an ossification center of the stylohyoid and fuses with the stylohyoid in two-thirds of horses. The lingual process has a separate ossification center.

A STUDY ON THE OCCURRENCE OF WORMIAN BONES IN ADULT DRY SKULLS

Background: Sutural or wormian bones are islands of bone that are commonly found in the sutures of the skull mainly along the lambdoid suture. These sutural bones which are irregular in size, shape and number may arise from separate centres of ossification. The prior knowledge about the Wormian bones is important because they are present in normal individuals as well as in various disorders such as osteogenesis imperfect, rickets, etc. Aim: To study the occurence of wormian bones in adult dry skulls Materials and Methods: The present study was carried out on 95 adult dry human skulls in the department of Anatomy, Adichunchanagiri Institute of Medical Sciences, B G Nagara. Skulls with fractures and deformities were excluded from the study. Intact skulls were cleaned thoroughly and observed for the presence of wormian bones along the sutures of skull. Results: Out of 95 skull bones studied, 24 (25.26%) skulls showed the presence of wormian bones. We also observed that maximum number of such bones (single or multiple) were present along the lambdoid suture followed by lambda, asterion, sagittal suture & coronal suture. A very small wormian bone was also found near the bregma of the skull. Conclusion: The awareness about the occurrence of wormian bones and their topographical distribution will guide the clinicians mainly neurosurgeons in their practice. These bones mimic fracture lines in radiograph; therefore radiologists must also be aware of this normal variation. KEY WORDS: Wormian bone, Lambdoid suture, skull.

Sex-Related Differences in the Developmental Morphology of the Atlas: A Computed Tomography Study.

A retrospective study. To elucidate sex-related differences in the age at synchondroses closure, the normative size of the atlas, and the ossification patterns of the atlas in Japanese children. The atlas develops from three ossification centers during childhood. The anterior and posterior synchondroses, which are separate ossification centers, mimic fracture lines on computed tomography (CT). Sex-related differences of age dependent morphological changes of the atlas in a large sample size have not been reported. This study analyzed data of 688 subjects (449 boys) between 0 and 18 years old who underwent CT examination of the head and/or neck between January 2010 and July 2016. The age at synchondroses closure, anteroposterior outer, inner, and spinal canal widths of the atlas, and variations of the ossification centers were examined. Anterior synchondroses closed by 10 years in boys and by 7 years in girls. Significant earlier closure of anterior synchondroses was observed in girls than in boys (P < 0.05 at 4 and 5 years old). Posterior synchondrosis closed by 6 years in boys and by 5 years in girls. The outer, inner, and spinal canal widths increased up to 10 to 15 years in both sexes, although all three parameters in girls peaked 3 years earlier than those in boys. All parameters in boys were significantly larger than those in girls, except in the 10- to 12-year-old age category. Two or more ossification centers in the anterior arch were observed in 18.3% subjects, and 6% had midline ossification centers in the posterior arch of the atlas. Distinct sex-related differences in the age at anterior synchondroses closure and the size of the atlas were observed in Japanese children. Knowledge of morphological features of the atlas could help distinguish fractures from synchondroses. 3.

Development of the Osteocranium in Natrix natrix (Serpentes, Colubridae) Embryogenesis II: Development of the jaws, palatal complex and associated bones

AbstractSnakes differ from the other vertebrates with their hyperkinetic skull. To establish the developmental features of the skull bones, involved in prey capture and ingestion, the Grass snake Natrix natrix (Serpentes, Colubridae) embryos are studied at all the successive stages of embryogenesis. Thirty‐five N. natrix embryos are examined. Twenty embryos are studied with histological methods; fifteen embryos are cleared and double‐stained with alizarin red and alcian blue. The sequence of appearance and formation of the upper and lower jaw bones, palatal complex and associated bones is described in accordance with the table of developmental stages. New features in the ossification mode of some bones are revealed: each bone, namely, the vomer, septomaxilla and maxilla, is formed from three separate ossification centres. Three ossification centres in the maxilla, two ossification centres in the bodies of the septomaxilla and vomer, as well as the unknown additional ossification centre in the vomer had not been previously described in snake embryos. The new data can be used in further comparative research on the reptile skull development and vertebrate phylogeny.

Analysis of risk factors for elbow dysplasia in giant breed dogs.

Identify radiographic risk factors for development of elbow dysplasia in giant breed dogs less than one year of age. Twenty-five giant breed puppies (Bernese Mountain dogs, English Mastiff, and Newfoundland) were studied. Both elbows of each dog were radiographed monthly from two to six months of age, then every other month until radial and ulnar physeal closure, followed two months later by bilateral elbow computed tomography. Radiographic parameters measured included the presence or absence of a separate centre of ossification of the anconeal process (SCOAP), medial coronoid disease (MCD), ununited anconeal process, humeral osteochondrosis, elbow incongruity, as well as the length of the radius and ulna, radius-to-ulna ratio, and date of closure of the radial and ulnar physes. Fifteen dogs completed the study. Two Bernese Mountain dogs were diagnosed with MCD. Risk factors significantly associated with medial coronoid disease included dyssynchronous physeal closure and a decreased radius-to-ulna ratio, both detected between eight to 11 months of age. A separate centre of ossification of the anconeal process was present in 60% of the dogs, and was not a risk factor for development of elbow dysplasia. Transient, dyssynchronous growth of the radius and ulna may be a risk factor for development of MCD in Bernese Mountain dogs. Dyssynchronous physeal closure or decreased radius-to-ulna ratio prior to radiographic closure of the distal ulnar and radial physes warrants further study in Bernese Mountain dogs and other breeds subject to MCD development.

Radiographic characterization of ossification of the ungular cartilages in horses: 271 cases (2005–2012)

To describe in detail the radiographic appearance of ossified ungular cartilages in horses and to evaluate the usefulness of a flexed dorsolateral-palmaromedial oblique (flexed oblique) radiographic view in evaluating the ungular cartilages. Retrospective case series. Sample-Radiographs of 1,255 front feet of horses. Ossification of the ungular cartilages was graded during evaluation of radiographs on a scale from 0 to 5; feet with cartilages with an ossification grade ≥ 2 were included (386 feet [271 horses]). The shape (straight, curved outward or inward, and dorsopalmar extension of ossification) was determined. The view on which abnormalities were best identified was documented. Abnormalities of the compact bone, radiopacity, trabecular architecture, compactospongious demarcation, and presence of radiolucent lines were recorded; grouped as modeling, adaptive changes, or both; compared with ossification grade, separate centers of ossification, mediolateral symmetry of ossification, shape, cartilage (medial or lateral), and foot (left or right); and tested for significant associations. Fractures (n = 35) were most common in feet with cartilages with an ossification grade of 4 (18) or 5 (17) and were best identified in flexed oblique images, compared with more commonly recommended images. Multivariable logistic regression showed a significant positive association of ossification grade with modeling or adaptive changes; feet with cartilages with an ossification grade of 4 (OR, 11.59; 95% CI, 6.52 to 20.60) or 5 (OR, 72.90; 95% CI, 25.32 to 209.90) were more likely than those with an ossification grade of 2 or 3 to have modeling or adaptive changes. Abnormally shaped cartilages were more likely to have modeling or adaptive changes, compared with normally shaped cartilages (OR, 4.90; 95% CI, 1.94 to 12.42). Extensive ossification and the presence of inward or outward curvature as well as palmar curvature or a bulbous shape were significant risk factors for modelling and adaptive changes. Flexed oblique images provided clinically useful information, including detection of abnormal shape and fractures, that may not be evident on other currently recommended images. Such images are recommended for complete radiographic appraisal of ossified ungular cartilages of the foot in horses.

An Update on the Pathogenesis of Osteochondrosis.

Osteochondrosis is defined as a focal disturbance in endochondral ossification. The cartilage superficial to an osteochondrosis lesion can fracture, giving rise to fragments in joints known as osteochondrosis dissecans (OCD). In pigs and horses, it has been confirmed that the disturbance in ossification is the result of failure of the blood supply to epiphyseal growth cartilage and associated ischemic chondronecrosis. The earliest lesion following vascular failure is an area of ischemic chondronecrosis at an intermediate depth of the growth cartilage (osteochondrosis latens) that is detectable ex vivo, indirectly using contrast-enhanced micro- and conventional computed tomography (CT) or directly using adiabatic T1ρ magnetic resonance imaging. More chronic lesions of ischemic chondronecrosis within the ossification front (osteochondrosis manifesta) are detectable by the same techniques and have also been followed longitudinally in pigs using plain CT. The results confirm that lesions sometimes undergo spontaneous resolution, and in combination, CT and histology observations indicate that this occurs by filling of radiolucent defects with bone from separate centers of endochondral ossification that form superficial to lesions and by phagocytosis and intramembranous ossification of granulation tissue that forms deep to lesions. Research is currently aimed at discovering the cause of the vascular failure in osteochondrosis, and studies of spontaneous lesions suggest that failure is associated with the process of incorporating blood vessels into the advancing ossification front during growth. Experimental studies also show that bacteremia can lead to vascular occlusion. Future challenges are to differentiate between causes of vascular failure and to discover the nature of the heritable predisposition for osteochondrosis.

Development of the bony skeleton in the Taiwan salamander, Hynobius formosanus MAKI, 1922 (Caudata: Hynobiidae): Heterochronies and reductions

The development of the bony skeleton in a partially embryonized lotic-breeding salamander Hynobius formosanus is studied using the ontogenetic series from late embryos to postmetamorphic juveniles and adult specimen. Early stages of skull development in this species are compared with the early cranial ontogeny in two non-embryonized lentic-breeding species H. lichenatus and H. nigrescens. The obtained results show that skeletal development distinguishes H. formosanus from other hynobiids by a set of important features: 1) the reduction of provisory ossifications (complete absence of palatine and reduced state of coronoid), 2) alteration of a typical sequence of ossification appearance, namely, the delayed formation of vomer and coronoid, and 3) the absence of a separate ossification center of a lacrimal and formation of a single prefrontolacrimal. These unique osteological characters in H. formosanus are admittedly connected with specific traits of its life history, including partial embryonization, endogenous feeding until the end of metamorphosis and relatively short larval period.

Os Trigonum syndrome – A case report

The ostrigonum is a small bone present on the posterolateral aspect of the talus. It is formed from a separate ossification center which fails to unite with the talus itself. Incidence is about 3-15% .The diagnosis can be difficult to make as symptoms and physical exam findings mimic those that occur withproblems related to an accessory soleus muscle, flexor hallucislongus, posteriortibialis, or peroneal tendons, arthritis involving the posterior tibiotalar or subtalar joints, or ostrigonum syndrome. Misdiagnosis of such injuries may result in inadequate management including immediate weight bearing and prolonged symptoms.

Age Determination from of Ossification Center Fusion around Knee Joint in Mumbai Region: A Radiological Study

The bones of human skeletons develop from separate ossification centers. From these centers ossification progresses till the bone is completely formed. These changes can be studied by means of Xrays and these changes are age related. It is therefore possible to determine the approximate age of an individual by radiological examination of bones till ossification is complete. This radiological study was carried out with the objective to assess the general skeletal maturity around knee joint, of subjects in Mumbai region. 170 males between age group of 3–25 years and 66 females between age group of 3–23 years attending the outpatient department of this hospital were selected. Age confirmed from history and noting the birth dates from driving license, passport, rations card or voter's card. The cases were selected after ruling out the nutritional, developmental, and endocrinal abnormality which affects the skeletal growth. Data analysis was done in P4 computer using HPSS software. At the end conclusions were drawn which are compared with available results of various previous studies.

Bipartite os Centrale Carpi in a Patient with the First Metacarpal Bone Fracture

Bipartite os Centrale Carpi in a Patient with the First Metacarpal Bone Fracture

Radiological Characterisation of Ossified Ungular Cartilages of the Foot

AimsOssified ungular cartilages may be associated with foot pain. There are no detailed descriptions of their radiological appearance. Dorsopalmar images are considered best for evaluation of ossification; the usefulness of oblique images has not been assessed. The aims were to describe the radiological appearance of ossified cartilages and to determine the usefulness of oblique images.MethodsRadiographs of all feet (n = 169, 2005–2012) with ≥ Grade 2 ossification (Dyson et al. ) of one/both ungular cartilages were assessed subjectively using a purpose‐designed grading system, after a repeatability study in which 10 sets of radiographs were examined 10 times. Detection of abnormalities was compared among conventional and oblique images.ResultsRadiological abnormalities including focal/diffuse increase in trabecular bone opacity, loss of trabecular architecture, and loss of definition between the trabecular bone and the cortices were more frequent in lateral cartilages (72, 59 and 60, respectively) than medial (41, 36 and 33, respectively). Cartilage shape varied in dorsopalmar images, being straight (270), curving axially (19) or abaxially (10). There was modelling of the cortices in 52 lateral (33 mild, 19 moderate) and 23 medial (17 mild, 6 moderate) cartilages. There were separate centres of ossification (SCsO) in 30 lateral and 14 medial cartilages. Fractures were present in 18 medial and 13 lateral cartilages, 20 at the base. Accurately distinguishing between fractures and osseous reaction around junctions between ossification centres was impossible in 8 cartilages. In total SCsO or fractures were seen in 59 dorsopalmar and 81 oblique images. Fracture sites and junctions between ossification centres were consistently best seen in oblique images. Palmar curvature of the cartilages could only be accurately detected in oblique images and was present in 31 cartilages.Conclusions and practical significanceLateral cartilages had a greater variation in radiological appearance than medial cartilages. Oblique images can provide information not available from other images.Ethical animal researchNot required by this Congress: retrospective analysis of archived radiographs. Sources of funding: None. Competing interests: None.

The pea‐shaped human pisiform results from the evolutionary loss of a growth plate

The human pisiform is a small nodular bone that serves as the distal attachment for the powerful forearm muscle, the flexor carpi ulnaris. In contrast, most other mammals, including primates and the ancestral hominid Australopithecus afarensis, possess a pisiform that is substantially elongated. An underappreciated fact is that in these species the pisiform develops from two separate ossification centers. A secondary center implies the presence of a growth plate (similar to the calcaneus) whose loss could serve as an evolutionary mechanism underlying human pisiform reduction. Here we perform a histological analysis of pisiform ossification in juvenile mice. We confirm the existence of a pisiform growth plate with distinct organized columnar and hyptertrophic chondrocyte zones. We also conducted a comparative analysis of hominoid pisiform ossification and confirm that epiphyses are present in Pan, Gorilla, and Pongo but not in humans. In addition, the initial ossification occurs substantially earlier in apes relative to humans, thus raising questions concerning the homology of the human pisiform and the two distinct ossification centers of other mammals. The research is funded by Penn State University.Grant Funding Source: Pennsylvania State University

Os Odontoideum as a Consequence of a Posttraumatic Displaced Ossiculum Terminale

1Department of Orthopaedic Surgery, Ehime Prefectural Central Hospital, 83-banchi, Kasugamachi, Matsuyama, Ehime 790-0024, Japan. E-mail address: [email protected] 2Department of Orthopaedic Surgery, Hoshigaoka Koseinenkin Hospital, 4-8-1 Hoshigaoka, Hirakata, Osaka 573-8511, Japan

Number of Ossification Centers in the Anuran Cranial Bones Depends upon the Rate of Development: Experimental Evidence

Cranial development was compared in Rana temporaria (Anura; Ranidae) and Bombina variegata (Anura; Discoglossidae) specimens reared at normal, high, and low level of thyroid hormone (TH). Sequence and timing of cranial ossification as well as rate of a particular bone’s differentiation and growth depend upon TH level. Also, bones which normally develop from a single ossification center (frontoparietal, parasphenoid, vomer, squamosal, angulosplenial, septomaxilla, pterygoid, and premaxilla) were revealed to form from two or more ossification centers in specimens reared at high and low TH level. This indicates them to develop from several early precalcified anlagen which normally fuse prior to the beginning of calcification thus appearing as a single ossification center. Changes in the rate of a particular bone’s differentiation and growth caused by manipulation with a TH level may cause precocious beginning of their calcification or their delayed fusion. As a result, they begin to calcify prior to their fusion thus appearing as several separate ossification centers. Number of ossification centers depends upon the rate of cranial and overall somatic development. Interspecies and individual differences in the rate of cranial and overall ontogeny are responsible for the inter- and intraspecific variability in the number of ossification centers recorded in anurans.

Neuroscan of Normal and Abnormal Vertebrae and Spinal Cord

Abstract The vertebral body, neural arch and its processes develop from the sclerotome of the primitive mesodermal segments. After chondrification, separate ossification centres appear for the body and one for each of the neural arches. Vertebrae are composed of a body and a vertebral arch. The vertebral foramina, which consist of the vertebral arch and back of vertebral body, form the vertebral canal including and protecting the spinal cord. The vertebral arches are formed by two pedicles and two laminae which unite as a spinous process. Relation between the vertebrae and spinal cord during pregnancy is interesting. In embryonal period, the CNS develops earlier than other part of embryonal structures and occupies approximately one third of the whole embryonal body. At the 3rd month of development the length of the spinal cord equals that of the vertebral column. The spinal nerves and the relationship of the spinal nerves to the vertebra are established. Therefore the spinal cord segment is at the same level as the corresponding vertebral level. In subsequent fetal period, however, fetal body structure including vertebral column develops faster than the neural tube. As the consequence of this different development of the column and nerves, caudal end of the spinal cord within the vertebral column relatively moves upward with advancing gestation and reaches to the level of the third lumber vertebra at birth.

Scintigraphic examination of the cartilages of the foot

Radiographic examination of the cartilages of the foot is well documented; however, there is limited information about their scintigraphic assessment. To evaluate the scintigraphic appearance of the cartilages of the foot using subjective and quantitative image analysis and to correlate radiographic and scintigraphic findings. An ossified cartilage would have similar radiopharmaceutical uptake (RU) to the ipsilateral aspect of the distal phalanx; RU would extend throughout the length of the ossified cartilage; a separate centre of ossification (SCO) would be identified on a scintigraphic image; and fracture or trauma to an ossified cartilage would manifest as increased RU (IRU). Front feet (n = 223) of horses (n = 186) that had dorsopalmar radiographic views and dorsal scintigraphic images were included in the study. The cartilages of the foot were graded radiographically and scintigraphically. Quantitative evaluation of the scintigraphic images was carried out using region of interest (ROI) analysis. For statistical analysis RU ratios were used. Correlations between a radiographically detected SCO and focal RU and between IRU and radiographic abnormalities were assessed. There was a good correlation and an excellent agreement between radiographic and scintigraphic grades. ROI analysis showed a proximal to distal increase in RU ratios within each cartilage of the foot. A radiographically identified SCO could be detected scintigraphically in 12/17 feet (70.6%). Thirty-eight feet had IRU in the region of a cartilage, 25 of which (65.8%) had corresponding radiographic abnormalities. Fracture of an ossified cartilage was associated with IRU in all horses. Scintigraphy may give information about the potential clinical significance of ossification of the cartilages of the foot and associated lesions, therefore prompting further investigation by use of a uniaxial ipsilateral palmar nerve block and imaging, using either magnetic resonance imaging and/or computed tomography.

Variation in mammalian proximal femoral development: comparative analysis of two distinct ossification patterns

The developmental anatomy of the proximal femur is complex. In some mammals, including humans, the femoral head and greater trochanter emerge as separate ossification centres within a common chondroepiphysis and remain separate throughout ontogeny. In other species, these secondary centres coalesce within the chondroepiphysis to form a single osseous epiphysis much like the proximal humerus. These differences in femoral ontogeny have not been previously addressed, yet are critical to an understanding of femoral mineralization and architecture across a wide range of mammals and may have key implications for understanding and treating hip abnormalities in humans. We evaluated femora from 70 mammalian species and categorized each according to the presence of a 'separate' or 'coalesced' proximal epiphysis based on visual assessment. We found that ossification type varies widely among mammals: taxa in the 'coalesced' group include marsupials, artiodactyls, perissodactyls, bats, carnivores and several primates, while the 'separate' group includes hominoids, many rodents, tree shrews and several marine species. There was no clear relationship to body size, phylogeny or locomotion, but qualitative and quantitative differences between the groups suggest that ossification type may be primarily an artefact of femoral shape and neck length. As some osseous abnormalities of the human hip appear to mimic the normal morphology of species with coalesced epiphyses, these results may provide insight into the aetiology and treatment of human hip disorders such as femoroacetabular impingement and early-onset osteoarthritis.