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Ossification of the mouse metatarsal: differentiation and proliferation in the presence/absence of a defined growth plate.

There is significant diversity in growth plate behavior among sites within an individual skeleton and between skeletons of different species. This variation within wild-type animals is an underutilized resource for studying skeletal development. One bone that potentially exhibits the most diverse behavior is the metatarsal. While one end forms a growth plate with an epiphyseal secondary center of ossification as in other long bones, the opposite end undergoes direct ossification in a manner more similar to short bones. Although descriptions of human metatarsal/metacarpal ossification are available, a detailed comparative analysis has yet to be conducted in an animal model amenable to biomolecular analysis. Here we report an analysis of proximal and distal ossification in an age series of mouse metatarsals. Safranin O staining was used for qualitative and quantitative histology, and chondrocyte differentiation and proliferation were analyzed using immunohistochemistry for type X collagen and proliferative cell nuclear antigen expression. We establish that, as in the human, both growth plate formation and direct ossification occur in the mouse metatarsal, with chondrocyte populations showing distinct differentiation patterns at opposite ends of the bone. In addition, growth plate formation is characterized by a peak of proliferation in reserve zone chondrocytes that distinguishes it from both established growth plates and direct ossification. Our analysis demonstrates that the mouse metatarsal is a productive model for investigating natural variation in ossification that can further understanding of vertebrate skeletal development and evolution.

Animals↗

Mechanical stresses and endochondral ossification in the chondroepiphysis.

In 1911, Gebhardt used a photoelastic model to relate mechanical stresses to the ossification pattern of the chondroepiphysis. Pauwels later conducted a photoelastic study using the same model geometry to develop a theory that the secondary ossific nucleus originates at a position of high-magnitude hydrostatic pressure where the shear stresses are zero. We conducted two-dimensional finite element analyses of the model used by Gebhardt and Pauwels. We demonstrate that Pauwels's photoelastic results are correct but are based on the imposition of incorrect boundary conditions. When more realistic boundary conditions were used, the finite element results changed dramatically. These results suggest that (a) the ossific nucleus appears in an area of high shear (deviatoric) stresses; (b) the edge of the advancing ossification front (zone of Ranvier or ossification grove) also experiences high shear stresses; and (c) the joint surface, where articular cartilage forms, is exposed to high-magnitude hydrostatic compression. These findings support the theory proposed by Carter and associates that intermittently applied shear stresses (or strain energy) promote endochondral ossification and that intermittently applied hydrostatic compression inhibits or prevents cartilage degeneration and ossification.

Growth Plate↗

Maxillary ossification in a series of six human embryos and fetuses aged from 9 to 12 weeks of amenorrhea: clinical implications.

An anatomic controversy exists concerning the number of nuclei of ossification of the maxilla in human embryos and fetuses. Many authors have described two maxillary ossification nuclei, an incisor nucleus and a maxillary nucleus properly so-called. Some of these have explained congenital labiomaxillary clefts by a defect of bony fusion between these two ossification nuclei. Others consider that there is only a single nucleus for maxillary ossification. In order to settle this question we performed a histologic study in six heads of embryos and fetuses aged from 9 to 12 weeks of amenorrhea (WA) to demonstrate the presence of one or more sites of maxillary ossification at the earliest stages. Our study revealed, on each side, a single zone of maxillary ossification, present from 9 WA, in the form of a sheet of osteoid tissue situated in close contact with the dental lamina. Maxillary ossification then progressed in the lateromedial direction, preserving a median transverse and ventral mesenchymal septum. This septum may constitute the phylogenetic remnant of an ancestral premaxilla.

Amenorrhea↗

Selecting a surgical method for thoracic myelopathy caused by ossification of the posterior longitudinal ligament.

STUDY DESIGN: The authors classified typical distributional patterns of ossification of the posterior longitudinal ligament of the thoracic spine in 1) central part of S-curve, 2) just above apical vertebra, and 3) combined with ossification of ligamentum flavum below apical vertebra. The results of the surgical methods selected according to the authors' classification were compared with those of previous reports. OBJECTIVES: To establish the criteria for selecting an appropriate surgical method for ossification of the posterior longitudinal ligament of the thoracic spine. SUMMARY OF BACKGROUND DATA: Poor surgical results for ossification of the posterior longitudinal ligament of "middle or lower thoracic spine" have been reported, but the unsuccessful location and curve has not been strictly defined. METHODS: The authors studied postsurgical results in 26 cases of thoracic myelopathy caused by ossification of the posterior longitudinal ligament. They also investigated radiographs of 111 cases, including 85 patients under observation, and examined the relationships between thoracic spine alignment and ossification of the posterior longitudinal ligament distribution. RESULTS: Twenty-three patients treated with methods conforming to the authors' criteria achieved satisfactory recovery in walking ability except for one patient. The results of the other three patients who underwent surgery with nonconforming methods were uneven. CONCLUSION: Posterior decompression, as well as anterior decompression, is effective in the first pattern in the cervicothoracic region. In case of the second pattern, the responsible ossification of the posterior longitudinal ligament always lies one or two levels above the apical vertebra and should be removed by anterior approach, regardless of the extent of kyphosis. Transthoracic anterior decompression surgery is considered the best method for most patients under the second and third patterns.

Adult↗

Fragmented coronoid process and incomplete ossification of the humeral condyle in a rottweiler.

OBJECTIVE: To describe incomplete ossification of the humeral condyle and fragmentation of the medial coronoid process in a Rottweiler. STUDY DESIGN: Clinical report. ANIMAL POPULATION: A 4-year-old sexually intact male Rottweiler. METHODS: Physical examination, radiography, and computed tomography of both elbow joints were performed initially. Drill holes were made across the humeral condyle to promote ossification. Radiography and computed tomography were repeated 14 weeks later. Radiography was repeated 15 months later. A mild intermittent lameness remained. RESULTS: Preoperatively a radiolucent line was present across the right humeral condyle. This radiolucent line remained unchanged 14 weeks after drill holes were made across the condyle. CONCLUSIONS: Incomplete ossification of the humeral condyle is present in Rottweilers. CLINICAL RELEVANCE: Incomplete ossification of the humeral condyle is present in Rottweilers and may coexist with fragmentation of the medial coronoid process in that breed. The radiographic diagnosis may be difficult because precise positioning is required to see the area of incomplete ossification. Computed tomography may be required to confirm the presence of incomplete ossification of the humeral condyle. Drilling holes across the humeral condyle does not appear to lead to union of the area of incomplete ossification.

Animals↗

[Comparative studies on bone growth in experimental animals. 1. Bone growth and ossification in mice (author's transl)].

Comparative studies are needed on the bilogical stage of the bone growth in experimental animals and human to extrapolate the data from animals to for estimating the risk of bone seeking redionuclides in man. The growth of bone length and the appearance and fusion of the secondary ossification centers of seven long bones were compared between both species. The stage of ossification was determined radiographically. The results showed that the ossifying process of the secondary ossification centers could be divided into the following three categories in mice; (1) acute ossification type, (2) remaining metastable stage type which is specific in mice and generally at the proximal end of bone, and (3) delayed ossification type. Compared with the average life span, differences in ossification between both species were that the appearance of secondary ossification centers was observed within concentrated period in mice and not in man, and that the fusion of these was observed with long duration in mice and not in man. From 17 weeks of age, the metastable status of the bone appeared in mice without complete fusion even at 27 weeks of age, for the experiment with bone seeking radionuclides, mice of age 17 weeks or more should be used consequently.

Age Factors↗

Comparative studies on maturation process of secondary ossification centers of long bones in the mouse, rat, dog and monkey.

Comparative studies was made on the whole processes of maturation of the secondary ossification centers in the extremity in the mouse, rat, dog and monkey in order to determine points of similarity and difference among these species. The appearance and the union of the secondary ossification centers were observed to follow a common sequence and order in all the species examined. The total bone score was defined as the sum of the bone scores of respective secondary ossification centers over the observation period according to a set criteria. By plotting these indices against the chronological age it was shown in all of these species that the whole process of maturation of the secondary ossification centers in the long bone consisted of three biological stages as indicated by the three straight lines with different slopes. The first stage is considered to account for the appearance of the secondary ossification centers and their accelerated development at early period, while the second stage corresponds to the subsequent gradual development. The third stage represents a period where the ossification centers reach a complete or almost complete unmion to diaphysis. It is concluded that in the mouse, rat, dog and monkey the maturation process of the secondary ossification centers follow the same growth consisting of three developmental stages and that each of these three stages provides a measure of comparison among these species.

Animals↗

Relationships between fetal body weight of Wistar rats at term and the extent of skeletal ossification.

We investigated the relationship between fetal body weight at term (pregnancy day 21) and the extent of ossification of sternum, metacarpus, metatarsus, phalanges (proximal, medial and distal) of fore- and hindlimbs and cervical and coccygeal vertebrae in Wistar rats. The relationships between fetal body weight and sex, intrauterine position, uterine horn, horn size, and litter size were determined using historical control data (7594 fetuses; 769 litters) of untreated rats. Relationships between body weight and degree of ossification were examined in a subset of 1484 historical control fetuses (154 litters) which were subsequently cleared and stained with alizarin red S. Fetal weight was independent of horn size, uterine horn side (left or right) or intrauterine position. Males were heavier than females and fetal weight decreased with increasing litter size. Evaluation of the skeleton showed that ossification of sternum, metacarpus and metatarsus was extensively complete and independent of fetal weight on pregnancy day 21. In contrast, the extent of ossification of fore- and hindlimb phalanges and of cervical and sacrococcygeal vertebrae was dependent on fetal body weight. The strongest correlation between body weight and degree of ossification was found for hindlimb, medial and proximal phalanges. Our data therefore suggest that, in full-term rat fetuses (day 21), reduced ossification of sternum, metacarpus and metatarsus results from a localized impairment of bone calcification (i.e., a malformation or variation) rather than from general growth retardation and that ossification of hindlimb (medial and proximal) phalanges is a good indicator of treatment-induced fetal growth retardation.

Animals↗

The prognostic importance of the ossific nucleus in the treatment of congenital dysplasia of the hip.

Ischemic necrosis of the femoral head occurring after the treatment of congenital dysplasia of the hip can negatively affect the long-term prognosis of the involved hip. Some investigators have suggested that the presence of the ossific nucleus of the femoral head at the time of closed or open reduction is associated with a lower rate of ischemic necrosis. This finding, if verified, could lead to a delay in the treatment of a dislocated hip until ossification of the femoral head has begun, which may be well after the age when the patient has started to walk. We conducted a computerized search of the medical records at our two tertiary-care children's hospitals to identify all patients with congenital dysplasia of the hip who had had a closed or open reduction between January 1, 1979, and December 31, 1993. One hundred and twenty-four patients (153 hips) who satisfied the criteria for inclusion were identified. The ossific nucleus was present in ninety hips and absent in sixty-three. Closed reduction was used in 112 hips and open reduction, in forty-one. Ischemic necrosis was identified in five hips (3 percent): four (6 percent) of the sixty-three hips that did not have an ossific nucleus and one (1 percent) of the ninety hips that had an ossific nucleus at the time of the reduction. With the numbers available for study, we could not detect a difference between these two groups. The age at reduction (p > 0.99), the method of reduction (p = 0.611), previous treatment with a Pavlik harness (p = 0.592), the use of preliminary traction (p = 0.602), concomitant procedures (p > 0.99), and a failure of the primary closed reduction (p = 0.579) were not associated with the development of ischemic necrosis after reduction. In our analysis of patients who were managed over a fifteen-year period, the data did not support the hypothesis that the presence of an ossific nucleus at the time of reduction of a congenitally dislocated hip is associated with a lower prevalence of ischemic necrosis of the femoral head. Sound operative principles dictate that operative reduction of a congenitally displaced hip should be performed when the child can be safely placed under anesthesia and without regard to the presence or absence of the ossific nucleus.

Case-Control Studies↗

Postnatal ossification centers of the atlas and axis in miniature schnauzers.

Postnatal ossification of the atlas and axis was studied in Miniature Schnauzers by examining alizarin-stained bone clearings, cleaned dry bones, radiographs, histologic sections, and arterially perfused bone clearings. Sixty-two pups (1 day to 16 weeks old) and 4 adults were examined. In 1-day-old pups, the atlas consisted of 3 separate ossification centers: a left and right neural arch center and midventrally, the intercentrum 1, which formed the body of the atlas. The axis contained 4 separate ossification centers: a left and right neural arch center; centrum 2 in the main part of the axis body; and centrum 1, which formed the caudal part of the dens and the cranial part of the axis body. By 6 weeks of age, the epiphysis on the caudal end of the axis body had begun to ossify. At this time, the intercentrum 2, which developed as a cuboidal ossification center intercalated between centrum 1 and centrum 2 in the middle of the cranial half of the axis body, also began to ossify. The centrum of the proatlas, which formed the apex of the dens, was first seen ossified in a 9-week-old pup. These 10 ossification centers were seen as constant and separate elements. In all dogs, the dens developed from 2 separate ossification centers: the centrum of the proatlas formed the cranial one-quarter, and centrum 1 formed the caudal three-quarters. Dens dysplasia is unlikely to be a result of failure of development of one of the ossification centers for the dens.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

[Ossification principle of the laryngeal skeleton of the human and mammals. Comparative anatomic studies].

In 3 oxen, 24 deer, 40 common hares and 27 rabbits, the laryngeal cartilages, freed from soft tissue, were examined roentgenologically for ossification, and compared with the well-known ossification pattern of the human thyroid cartilage. In the human, the thyroid cartilage ossifies in four preferential directions: horizontal-caudal, vertical-lateral, vertical-median, and obliquely tongue-shaped; in cattle ossification in the three directions: horizontal-caudal, vertical-median, and vertical-lateral; and in the deer in two directions: median-concentric and vertical-lateral. The cricoid cartilage in cattle and deer ossifies at the lamina and the upper border of the arch, the arytenoid cartilages ossify at the muscular process. In the common hare the thyroid cartilage ossifies only rarely, the other cartilages, in common with the entire laryngeal skeleton of the rabbit, never. The cause of ossification of the laryngeal cartilages is their deformation by the muscles of the larynx. The differences in the ossification patterns in humans, cattle and deer are due to the species-specific mechanical stress determined by the respective anatomy. The absence of ossification in the common hare and rabbit, on the other hand, is an expression of too small a deformational stress of their laryngeal skeleton. Ossification and nonossification are examples of the same principle, the self-regulating adaptation of connective and supportive tissues to mechanical stresses.

Age Factors↗

Ossification of lateral components in the human prenatal cranial base.

The purpose of the present study was to perform a radiographic description of the developing osseous structures in the prenatal human cranial base and to describe the sequence in which these structures ossify. The material consisted of 58 normal human fetuses (crown-rump length (CRL) 26-180 mm). The period investigated covered the time interval from the period before start of ossification at 8 weeks gestational age to occurrence of distinct ossification at 22 weeks gestational age. The osseous structures of 48 cranial bases were identified by radiography, supplemented by inspection of ten deviscerated cranial bases. The time of appearance of ossification of the individual bones was in agreement with former reports. The study showed a remarkable consistency in the sequence of ossification in the lateral part of the cranial base (parasagittal segment, PSS). The development was divided into eight stages. Bilateral agreement in ossification pattern was observed. The ossification pattern in the parasagittal segments of the cranial base was characterized by occurrence of osseous bone structures in the squama regions before occurrence in the cranial base region. It is suggested that a connection exists between the ossification pattern of the cranial base and the developmental pattern of the brain.

Embryonic and Fetal Development↗

Incomplete ossification of the tarsal bones in foals: 22 cases (1988-1996).

OBJECTIVE: To determine outcome for foals with incomplete ossification of the tarsal bones and to determine whether clinical and radiographic abnormalities at the time of initial examination were associated with outcome. DESIGN: Retrospective study. ANIMALS: 22 foals. PROCEDURE: Information on signalment, history, owner's initial complaint, clinical findings, whether tarsus valgus was evident, and radiographic abnormalities was obtained from medical records. Radiographic lesions were classified as type I (i.e., incomplete ossification with < 30% collapse of the affected bones) or type II (incomplete ossification with > 30% collapse and pinching or fragmentation of the affected bones). Follow-up information was obtained via telephone conversations with owners. RESULTS: Foals were between 1 day and 10 months old when first examined. Eleven were premature (i.e., < 320 days of gestation) or were twins. Sixteen had tarsus valgus. Severity of radiographic lesions was associated with outcome; 4 of 6 foals with type-I incomplete ossification of the tarsal bones performed as intended, but only 3 of 16 foals with type-II incomplete ossification of the tarsal bones performed as intended. CLINICAL IMPLICATIONS: For foals with incomplete ossification of the tarsal bones, severity of the radiographic lesions was associated with outcome. Foals with type-II incomplete ossification of the tarsal bones have a guarded prognosis for athletic soundness.

Animals↗

Ossification of the posterior atlantoaxial membrane and the transverse atlantal ligament.

STUDY DESIGN: Case report. OBJECTIVE: To report a case of ossification of the posterior atlantoaxial membrane (PAAM) and ossification of the transverse ligament of the atlas (TAL). SUMMARY OF BACKGROUND DATA: Ossification of the PAAM and TAL are both very rare clinical entities. This is the first case involving ossification of both the PAAM and TAL with the development of cervical myelopathy. METHODS: Patient's history, physical examination, radiographic evaluation, surgical treatment, and outcome are examined. Relevant literature is also reviewed. RESULTS: The patient's neurological symptoms significantly improved after posterior decompressive surgery. CONCLUSION: Ossification of various parts of the spinal ligament have been reported previously. Among them, ossification of both the PAAM and TAL has never been reported previously and is thus extremely rare. Surgical intervention improved the neurological impairment.

Aged↗

Human BMP-2 gene transfer using transcutaneous in vivo electroporation induced both intramembranous and endochondral ossification.

It has been generally accepted that bone morphogenetic protein-2 (BMP-2) can induce osteogenesis in skeletal muscles via endochondral ossification. However, it is not clear how the ossification process occurs after the BMP-2 gene transfer to skeletal muscles in rats using in vivo electroporation. In this study, we evaluated the ossification process by BMP-2 gene transfer using in vivo electroporation. The gastrocnemius muscles of Wistar rats were injected with human BMP-2 gene expression vector (pCAGGS-BMP-2), followed by electroporation under the condition of 100 V, 50 msec per 1 sec, x8. Light and electron microscopic and radiographic analyses were performed at 1, 3, 5, 7, and 10 days after treatment. At 7 days, no sign of cartilage and/or bone formation was detected. However, at 10 days after in vivo electroporation, soft X-ray analysis revealed small lucent areas around the plasmid-injected region. Clusters of both cartilage tissues, leading to endochondral ossification and intramembranous bones of various sizes, were observed between muscle fibers. RT-PCR detected osteocalcin mRNA, showing bone formation at 10 days. Our findings strongly suggest that BMP-2 gene transfer using in vivo electroporation induces not only endochondral ossification but also intramembranous ossification.

Animals↗

Frequency and size of ossifications in the caudal attachments of the ligamentum flavum of the thoracic spine. Role of rotatory strains in their development. An anatomic study of 121 spines.

Ossifications in the caudal attachments of the ligamentum flavum were studied on 121 dried thoracic spines. Most of them were aged. Frequency increased in a caudal direction. At T12, frequency depended on the orientation of the zygapophyseal joints of T11-12 which determined the range of rotation. When they were of thoracic orientation, allowing large range of rotation, ossifications were present in 83% of cases. If orientation was lumbar, allowing poor range of rotation, ossifications became much less frequent:33%. The size of ossifications was also studied. The smaller were in T1 and T2. In T11 and T12, size also depended on the orientation of the zygapophyseal joints of T11-12. If it allowed important range of rotation, ossifications were large sized. In the opposite case, they were small sized. Ossifications of caudal attachments of ligamentum flavum appear to be a normal feature of the aged lower thoracic spine. Their frequency in a given motion segment seems to be influenced by rotational strains.

Biomechanical Phenomena↗

[Value of a combined ossification prophylaxis with indomethacin and radiotherapy for acetabular fractures].

BACKGROUND: Heterotopic ossification is a complication in patients with surgically treated acetabular fractures. The incidence is related to the surgical approach (extended iliofemoral, posterior or a combined approach). The objective of this study was to evaluate the incidence of heterotopic ossification in patients with acetabular fractures who received a combined prophylaxis with both a single dose of radiation and indomethacin compared to those who received only a prophylaxis with radiation or indomethacin. PATIENTS AND METHODS: A total of 24 patients with a combined prophylaxis after surgery were examined retrospectively 24 months after trauma. A systematic literature review was performed and our own results were compared with different methods for prophylaxis of heterotopic ossification from the literature. RESULTS: Only one patient developed a heterotopic ossification. In accordance with the literature, combined prophylaxis showed the least incidence of ossification compared to the other methods. Differences in incidence frequencies were significant between the different prophylaxis methods. CONCLUSION: A combined prophylaxis for heterotopic ossification in surgically treated acetabular fractures seems to be a better alternative than a prophylaxis with radiation or indomethacin alone.

Acetabulum↗

Extra pelvic ossification centers in thanatophoric dysplasia and platyspondylic lethal skeletal dysplasia-San Diego type.

The platyspondylic lethal skeletal dysplasias (PLSD) are a group of heterogeneous disorders including thanatophoric dysplasia (TD) and the TD variants (San Diego, Torrance, and Luton types). TD is the most common form and has been divided into two subtypes (TD1 and TD2) based on clinical and radiologic criteria and analysis of mutations in the fibroblast growth factor receptor 3 (FGFR3) gene. The variants are distinguished from TD by characteristic radiographic and chondro-osseous morphologic features. We have recently identified FGFR3 mutations in PLSD-San Diego type (PLSD-SD) which are identical to those found in TD1, but the known TD FGFR3 mutations were not found in the other PLSD variants. After reviewing radiographs from 32 cases of PLSD-SD and 47 cases of TD with gestational ages under 24 weeks, we noted novel accessory ossification centers in the ischia of 18 cases of PLSD-SD and 44 of TD, and the ilia in 18 cases of PLSD-SD and 20 of TD. Only three cases of TD and five cases of PLSD-SD did not have extra pelvic ossification centers. At a gestational age greater than 24 weeks, the extra centers are fused with the main bone. The radiographic appearance and chondro-osseous morphology of cases with and without accessory pelvic ossification centers were otherwise indistinguishable. Morphologically, the accessory pelvic ossification centers resulted from membranous ossification. Extra pelvic ossifications are a common radiographic finding in TD and PLSD-SD.

Abnormalities, Multiple↗