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PubMed2007

Prevalence of heterotopic ossification following total disc replacement. A prospective, randomized study of two hundred and seventy-six patients.

BACKGROUND: Despite reports of good clinical outcomes in patients treated with lumbar and cervical disc replacements, varying degrees of heterotopic bone have been observed around these devices. The purposes of the present study were to determine the prevalence of heterotopic ossification following lumbar disc replacement and to investigate whether heterotopic ossification results in loss of motion or negatively affects clinical outcome. METHODS: All preoperative and postoperative radiographs from a completed prospective, randomized, United States Food and Drug Administration-regulated trial comparing replacement with the CHARITE Artificial Disc with anterior interbody arthrodesis were analyzed. In each of 276 patients treated with disc replacement, heterotopic ossification was categorized with use of a validated 5-point radiographic classification system both preoperatively and at all protocol-specified follow-up intervals to two years. The range of motion on flexion and extension radiographs made preoperatively was compared with that on radiographs made two years postoperatively, and the motion was correlated with the presence or absence of heterotopic ossification. Similarly, validated clinical outcome measures were correlated with the presence or absence of heterotopic ossification at two years. RESULTS: The prevalence of heterotopic ossification in the 276 consecutive patients treated with lumbar disc replacement with the CHARITE Artificial Disc was 4.3%. There were four cases of Class-I heterotopic ossification and eight cases of Class-II heterotopic ossification. In five of the twelve patients, heterotopic bone was visible as early as six weeks postoperatively, and eleven of the twelve patients had evidence of heterotopic ossification by three months postoperatively. The postoperative range of motion exceeded the preoperative range in all of the patients with heterotopic ossification. With the numbers available, no difference in either the range of motion or the clinical outcome at twenty-four months postoperatively was found between the patients who had and those who did not have heterotopic ossification. CONCLUSIONS: Heterotopic ossification is infrequent in patients treated with the CHARITE Artificial Disc, and it does not impact the range of motion or clinical outcome.

Disability Evaluation↗

PubMed2000

Ossification of the cartilages in the front feet of young Norwegian coldblooded horses.

The purpose of the present study was to evaluate the nature of ossification of the cartilages in the front feet of young, about 2-year-old Norwegian coldblooded horses, and to compare offspring of different sires in this respect. Dorsopalmar radiographs of the front feet of 392 horses (187 female and 205 male) were evaluated for ossification at the base of the cartilage and for separate centres of ossification. The horses were offspring of 45 different sires. Ossification extending above the navicular bone and separate centres of ossification were considered as significant. Minimal to mild ossification at the base of the cartilages was commonly seen, and significant ossification was present in one or more of the cartilages in 11.5% of the horses. The lateral compared to medial cartilages had more ossification and females had more ossification and more separate centres of ossification than males. The prevalence of horses with significant ossifications was significantly higher (46.3%) among offspring of one frequently used stallion than in the group consisting of offspring of 4 other popular stallions (3.5%) and in another group consisting of offspring of other, less frequently used stallions (9.6%). Ossification of the cartilages is considered to have a hereditary background in Norwegian coldblooded horses.

Animals↗

PubMed1997

[Clinical aspects, differential diagnosis and histogenesis of heterotopic ossification].

Investigations regarding proliferation behaviour, histogenesis and bone transformation were carried out on soft tissue samples with 133 heterotopic ossifications (HO), collected from the surgical material of the Institute of Pathology, Berufsgenossenschaftliche Kliniken Bergmannsheil, using methods of conventional histology, histochemistry, immunohistochemistry, electron microscopy and molecular biology, yielding the following results: 1. There is only a limited pathognomonic growth pattern for the variant of non-traumatic heterotopic ossification. Basically, the ossification foci may be divided into central, intermediate and peripheral zones. Expression intensities of the proliferation markers PCNA and MIB-1 show the proliferation behaviour in peripheral areas of osteogenesis to be similar to that found in autonomous osseous neoplasias. The phenotypical picture of zonal architecture found in HO can be seen by the simultaneous demonstration of variable image sequences of multifocally arising ectopic formations of new bone with varying degrees of maturation. 2. Vascular endothelium and pericytes are integrated into the formal histogenesis of heterotopic ossification and belong to osteoprogenitor cells as "stem cells" of heterotopic ossification. 3. The histochemically established expression pattern of alkaline phosphatasis is in good correlation with the degree of activity of the step-by-step development of heterotopic ossification. The intracellular demonstration of alkaline phosphatasis is an indicator for the transformation towards an osteogenic direction. In HO, the enzyme is a major characteristic of osteoprogenitor cells. 4. According to our immunohistochemical results, the proteoglycanes Decorin and PG 100-osteogenic matrix proteins-show a phase-like expression and are involved in osteoneogenesis. They are predominantly found in the area of mineralization. The proteoglycane 100 experiences a "modulation" and can be demonstrated almost selectively in osteoclasts in advanced stages of osteodevelopment. 5. Using in situ hybridization-with digoxigenin labeled cDNA probes- and a propidium iodide counterstaining a co-expression of collagene types I, II and III-mRNA could be demonstrated in samples of ossification. The expression pattern is similar to the collagen expression I. in early phases of embryonal bone development II. with callus proliferation and shows III. also similarities to chondral neoplasias. The results underline the reactive-neoplastic character of heterotopic ossification. 6. TGF-beta 1 mRNA shows a polytopic expression pattern with accumulation in areas of osteogenesis. TGF-beta 1 was found mostly in cartilage cells of heterotopic ossifications, as were collagene types I (alpha 1) and III (alpha 1) mRNAs. In sum, our in situ hybridization results underline the central part of cartilage cells in the ossification process in ectopic osteoneogenesis. This is also indicated by a phenotypical alteration of collagen expression as well as by an accumulation of TGF-beta 1 in chondral ossification areas. In situ hybridization propidium iodide counterstaining offers a reproducable image of morphological structures in the histological slide sample by means of fluorescence microscopy. 7. Phenotyping of osteroclasts in HO revealed their derivation from mature local macrophages. The immunohistochemical characterization with the demonstration of the vitronectin receptor classified the multinucleate giant cells of HO as original osteoclasts. Their origin is in accordance with the histogenetical concept of original bone. 8. Summarizing, the results characterize heterotopic ossification as a reactive proliferative and reversible neoplasia in chronically damaged soft tissue. From the formal pathogenetical point of view, relations could be established to orthotopic osteoneogenesis as well as to impaired proliferation kinetics, similar to osseous autonomous neoplastic lesions. (ABSTRACT TRUNCATED)

Biomarkers↗

PubMed2005

[Prevention of heterotopic ossifications in hip arthroplasty: effectiveness of selective Cox-2 inhibitors (celecoxib) versus ketoprofen].

PURPOSE OF THE STUDY: Peri-prosthetic ossifications are a frequent complication of total hip arthroplasty, which, if effective preventive measures are not taken, occur in 60% of patients. Numerous classic antiinflammatory agents have shown their preventive efficacy. New selective Cox-2 inhibitors offer the possibility of reducing the adverse effects of antiinflammatory drugs but remain to be proven effective in this indication. The purpose of this pilot study was to compare the efficacy of celecoxib versus ketoprofen. MATERIAL AND METHODS: In order to obtain sufficient statistical power to have a 70% chance of detecting a 25% difference between the two treatments with a 5% risk of error, we evaluated the incidence of peri-prosthetic ossifications of the hip in a prospective monocentric series of 52 patients receiving 400 mg celecoxib a day during a week. It was compared with the incidence in a control series of 52 matched patients (same age, gender, diagnosis, operator experience) given 200 mg ketoprofen iv for 48 hr then 300 mg po for 5 days as preventive treatment. Ossifications were studied on the plain AP view of the pelvis at a mean follow-up of more than 11 months (11.4 vs 11.9). The Brooker classification was determined. RESULTS: The percent of patients presenting peri-prosthetic ossifications was equivalent. For the celecoxib group, 60% of the patients were free of ossifications; 28.9% presented stage 1 ossification and 11.1% stage 2 ossification; none of the hip exhibited a higher stage. In the ketoprofen control group, 53.2% of patients were free of ossification, 38.2% had stage 1 ossification, 6.4% stage 2, and 2.1% stage 3; there was no patient with stage 4. Fisher's exact test did not demonstrate a significant difference between the groups (p<0.51). Compared with an older series of patients who were not given preventive treatment, there was a significant reduction in incidence of peri-prosthetic ossification (p=0.014). DISCUSSION: The two study groups were not significantly different for age, gender, or underlying disease. There were an equivalent number of cases of intolerance to treatment in the two groups. CONCLUSION: These findings appear to indicate an equivalent efficacy for celecoxib and ketoprofen for the reduction of peri-prosthetic ossifications. Based on these results, a randomized prospective comparative study can be undertaken without risk of losing effective prevention in one group. This prospective study should enable a more precise evaluation of treatment equivalence and quantify any potential gain in morbidity obtained with celecoxib.

Aged↗

PubMed1997

Bone mineral density in patients with ossification of the posterior longitudinal ligament. Minimal decrease of bone mineral density with aging.

STUDY DESIGN: Bone mineral density of individuals with ossification of the posterior longitudinal ligament and that of normal people was determined by dual-energy x-ray absorptiometry. OBJECTIVES: To determine whether bone mineral density in the people with ossification of the posterior longitudinal ligament is higher than that in normal individuals even in body parts other than the spine, and to evaluate the relation between bone mineral density and age in patients with ossification of the posterior longitudinal ligament. SUMMARY OF BACKGROUND DATA: It is unknown whether the bone mineral density of patients with ossification of the posterior longitudinal ligament is greater in body parts other than the spine. If so, it provides a basis for the theory that certain systemic factors are involved in the pathogenesis of ossification of the posterior longitudinal ligament. Because bone mineral density decreases physiologically after middle age, the influence of age must be considered in evaluating bone mineral density. METHODS: In the rib area and upper and lower limb areas, which are not affected by ossification of the spinal ligament, bone mineral density of 45 men with ossification of the posterior longitudinal ligament of the cervical spine was compared with that of 25 men without ossification of the posterior longitudinal ligament (normal group). RESULTS: Bone mineral density was higher in the group with ossification of the posterior longitudinal ligament in each part and significantly higher in the rib and lower limb areas (rib: P < 0.01, lower limb: P < 0.05). The age-related decrease was significantly less in the group with ossification of the posterior longitudinal ligament (rib: P < 0.01, upper limb: P < 0.05, lower limb: P < 0.01). CONCLUSIONS: Systemic factors that increase bone mineral density appear to be involved in the pathogenesis of ossification of the posterior longitudinal ligament, and these factors may be activated after middle age.

Absorptiometry, Photon↗

PubMed2004

Variation in the ossification process of the anconeal and medial coronoid processes of the canine ulna.

This morphological and radiographic study investigates the ossification process of the anconeal and medial coronoid processes of the ulna in a sample of 142 dogs ranging in age from neonatal to 44 weeks. The anconeal process was noted to develop by appositional ossification, formation of a separate ossification center, or a combination of both. Several developmental stages of the ossification center of the anconeal process as well as its anatomic position and radiographic appearance are described. Differences have been noted in the shape of this ossification center as well as the ossification process itself. The medial coronoid process develops exclusively by appositional ossification. Unlike ossification of the anconeal process, ossification of the medial coronoid process was completed earlier (p < 0.05) in smaller than in the larger dogs. In smaller dogs, both the medial coronoid and anconeal processes were found to be mature by the age of 16 weeks. In the larger dogs, ossification of the anconeal process was completed not before 14 weeks of age and ossification of the medial coronoid process was completed about 6 weeks later.

Animals↗

PubMed1990

The development of centres of ossification of bones forming elbow joints in young swine.

Epiphyseal centres of ossification in the bones forming the elbow joints of pigs between one day and 15 weeks of age were examined radiographically, macroscopically, mesoscopically and microscopically. Thoracic limbs from 39 pigs were perfused with India ink or silicone rubber injection compound and the bones were dissected free of soft tissues. The humerus, ulna and radius were fixed in formalin or ethyl alcohol and then cleared by the modified Spalteholz technique. Bones were radiographed, examined grossly, and then cut into slabs for mesoscopical evaluation. Foci considered to be calcifying within cartilaginous anlage were selected for microscopical examination. It was concluded that the epiphyseal centre of ossification develops at different times in different sites in the bones forming the elbow joint. Centres of ossification are initiated when foci of chondrocytes adjacent to one side of a cartilage canal undergo hypertrophy and the inter-territorial matrix becomes calcified. Osteogenesis then proceeds in the calcified focus, presumably with osteoprogenitor cells that originate within the cartilage canals. Subsequently, each epiphyseal centre of ossification enlarges by one of two methods. Firstly, the layer of cartilage adjacent to the centre undergoes endochondral ossification, thus allowing for the circumferential growth of the epiphyseal centre of ossification. Secondly, foci of calcification develop adjacent to the ends of cartilage canals near the epiphyseal centre of ossification and eventually the focus of calcification coalesces with the developing epiphyseal centre of ossification, thus establishing a new ossification front. Endochondral ossification continues at the periphery of the mass of bone. Mesoscopical examination is more useful than radiographical evaluation for identifying small foci of calcification which precede epiphyseal centres of ossification.

Animals↗

PubMed1991

Long term follow-up of diffuse idiopathic skeletal hyperostosis in the cervical spine. Analysis of progression of ossification.

In eleven patients with diffuse idiopathic skeletal hyperostosis who presented with extensive ossification in the cervical spine, progression or regression of ossification during the follow-up period were measured in extent and thickness radiographically. Intervertebral range of motion was also measured and the relation between changes of ossification and intervertebral mobility was analyzed. The range of motion at the segments at which ossification progressed was statistically quite different from those at which no progression was observed. It was found that ossification grew in thickness at mobile segments and no growth of ossification was present at immobile segments. Dysphagia caused by massive ossification was cured by surgical removal in two cases. Recurrent ossifications were detected in them some years after surgery, and one of them complained of dysphagia again. To prevent recurrent ossification and dysphagia, it was considered that immobilization of the concerned segment was necessary by bone grafting or preservation of the continuity of ossification.

Aged↗

PubMedDate not supplied

[Prevention of para-articular ossifications by radiotherapy after cementless total hip endoprosthesis implantation].

By means of a prospective study, concerning the postoperative rate of ossification after cementless total hip replacement, it was due to prove the efficacy of radiotherapy in preventing periarticular ossification. In 1992 arthroplasty was followed by radiotherapy of 50 hip joints as regular therapy. The radiation was performed with a focal dose of 8 Gy. Patients with bilateral cementless total hip replacement and radiotherapy only at one side were of special interest in this study. Within the 24th postoperative week in 28 (56%) of the radiated hip joins no periarticular ossifications were found. In 20 (40%) we found ossifications grade 1, in 1 case ossification grade II and in 1 further case ossification grade III following the classification of Arcq. By 8 patients with former cementless total hip replacement without postoperative radiotherapy, a significant reduction of the ossification rate was found in the contralateral hip joint treated by postoperative radiotherapy. The rate of ossification was reduced by 28%. In correlation to reduction of periarticular ossification the increase on the overall range of motion in the radiated hip joins was 10.9%. By none of the patients treated by radiotherapy we found a disturbed healing process, a deep infection or an early loosening of the endoprosthesis. Postoperative radiotherapy as regular therapy for prophylaxis of periarticular ossification after Cementless total hip replacement can subsequently be recommended.

Adult↗

PubMed2001

Response of peripheral lymphocytes from patients with ossification of posterior longitudinal ligament.

The in vitro response of peripheral blood mononuclear cells or enriched CD4+ T cells from patients with ossification of the posterior longitudinal ligament to anti-CD3 monoclonal antibody has been studied. The response in both was significantly lower in patients with the continuous-type ossification than in patients with the segmental-type ossification and in healthy volunteers, and was inversely correlated with the number of vertebral bodies with ossified ligament. In patients with the segmental-type ossification, the response of peripheral blood mononuclear cells was significantly lower than that in healthy volunteers, but that of the enriched T cells was not. B cell proliferation in response to fixed Staphylococcus aureus cells was significantly lower in patients with the continuous-type ossification than in healthy volunteers but was not correlated with the number of vertebral bodies with ossified ligament. The B cell response in patients with the segmental-type ossification was not lower than that in healthy volunteers. Serum concentrations of transforming growth factor-beta1 and basic fibroblast growth factor also were higher in patients with the continuous-type ossification than in patients with the segmental-type ossification and in healthy volunteers. The findings raise the possibility that continuous-type ossification of posterior longitudinal ligament might develop differently from segmental-type ossification.

Aged↗

PubMed1995

Ultrastructural observations on the ossification of the supraspinous ligament.

STUDY DESIGN: This study analyzed the process of ossification of spinal ligaments. Supraspinous ligaments excised during surgery were studied by light and scanning electron microscopy. OBJECTIVES: The results were correlated to determine the mechanism of ossification of spinal ligaments. SUMMARY OF BACKGROUND DATA: Ossification of the ligamentum flavum has been described in detail by Hiraoka, Yamaguchi, and others. However, the pathogenesis of ossification of the spinal ligaments remains unclear. Some studies have been performed by light and transmission electron microscopy, but no detailed investigation of the ossification of the spinal ligaments by scanning electron microscopy has been performed. METHODS: Specimens of supraspinous ligament were taken from 41 patients during spinal surgery. Ossification was diagnosed macroscopically and radiologically for 20 patients. The specimens were examined using light and scanning electron microscopy. RESULTS: Collagen fibrils were 700-2000 A in diameter and were arranged in parallel. The ligament insertion divided into four zones and seemed to fit the description of Enthesis histologically. Close to the ossification region, there were a region in which some fibrils were thinner and branchings became slightly stronger, tending to form bridges of minute fibrils between other fibrils. Closer to the region of actual ossification, there was a region in which extra-fibrillar substances completely deposited. In the region of actual ossification, there were medullary spaces of varying sizes, and the surrounding collagen fibers were dense and arranged in a lamellar fashion. Osteocyte lacunae had formed and the cells regarded to be the osteocytes were present on the inside. CONCLUSION: Ossification of the supraspinous ligament possibly occurs as follows. Fibroblasts or chondrocyte-like cells respond to some external stimulus, form an irregular network of fine fibrils, and produce acid mucopolysaccharide. These undergo calcification and capillary invasion. Undifferentiated mesenchymal cells invaded and are transformed into osteoblasts. Then osteogenesis ensues with progressive calcification.

Adolescent↗

PubMed1996

Effects of strain distribution in the intervertebral discs on the progression of ossification of the posterior longitudinal ligaments.

STUDY DESIGN: Strain distribution in the intervertebral discs was evaluated biomechanically using an engineering true strain calculation formula. OBJECTIVES: This study was performed to clarify the involvement of dynamic factors in the progression of ossification of the posterior longitudinal ligament. SUMMARY OF BACKGROUND DATA: In patients with ossification of the posterior longitudinal ligament of the cervical spine, ossification frequently progresses after laminectomy. This suggests the involvement of dynamic factors in the progression of ossification. However, these factors have not yet been clarified. METHODS: The analysis was performed on 101 patients with ossification of the posterior longitudinal ligament by employing dynamic lateral x-ray films of the cervical spine. The x-ray films were digitized and used as computer data for calculating the strain distribution. X-ray films were obtained again 5 years later, and the strain distribution and the presence or absence of progression of ossification were evaluated. RESULTS: The progression of ossification of the posterior longitudinal ligament was highly correlated with abnormal strain distribution in the intervertebral discs. Progression of ossification was frequently observed in areas having disc distortion in tension and extension on the posterior longitudinal ligament. CONCLUSIONS: In this study, the area of progression of ossification corresponded to the area showing uneven strain distribution and resultant concentration of dynamic stress. These results suggest an important role for dynamic factors in the progression of ossification of the posterior longitudinal ligament.

Adult↗

PubMed2003

Radiculopathy due to ossification of the yellow ligament at the lower lumbar spine.

STUDY DESIGN: A case report. OBJECTIVES: To report a rare case of a 27-year-old female with ossification of yellow ligament at the lower lumbar spine presenting radiculopathy with a drop foot. SUMMARY OF BACKGROUND DATA: The majority of cases of ossification of yellow ligament occur at the lower third of the thoracic or the thoracolumbar spine. There are only a few reports of ossification of yellow ligament in the lumbar spine and radiculopathy due to ossification of yellow ligament at L4-L5 and L5-S1 levels is very uncommon. METHODS: A 27-year-old female with a prior fracture of posterior ring apophysis of L5 presented with leg pain and a drop foot. Magnetic resonance imaging demonstrated stenosis with compression of the cauda equina at the L4-L5 and L5-S1 levels. RESULTS: Decompressive laminectomy of L5 and removal of the ossified yellow ligaments were performed. Histologic examination of en bloc specimen of ossification of yellow ligament revealed degenerative changes of the elastic fibers in the yellow ligament with adjacent chondrosis and ossification. The patient's severe leg pain disappeared completely, although the extent of the drop foot had not fully recovered at the final follow-up examination. CONCLUSIONS: The mechanism of ossification of yellow ligament in the present case was unclear. The patient did not have any previous generalized disorders besides the history of a ring apophysial fracture or any family history of treatment for ossification of the posterior longitudinal ligament or ossification of yellow ligament. Therefore, localized mechanical stress might have influenced the development of ossification of yellow ligament at lower lumbar spine.

Adult↗

PubMed2006

Heterotopic ossification in total cervical artificial disc replacement.

STUDY DESIGN: Prospective clinical study enrolled in 2 centers (Munich and Liberec) as part of a prospective European multicenter study with ProDisc C (Synthes Inc., Paoli, PA). OBJECTIVES: The first goal of the study was to evaluate the rate of heterotopic ossifications identified with plain radiograph following total cervical disc replacement (TCDR). The second goal was to show whether segmental motion can be preserved, and whether TCDR can provide improvement of the patient's ability to perform activities of daily living as well as a decrease of pain. SUMMARY OF BACKGROUND DATA: Only a few reports about the radiologic outcome after TCDR are published so far. Heterotopic ossification is a well-known phenomenon after total hip arthroplasty. The rate of heterotopic ossification following TCDR is unclear. METHODS: The radiographs of 54 patients (in total, 77 implanted prostheses) were analyzed 1 year after TCDR with a ProDisc C prosthesis. We classified the heterotopic ossification in 5 grades according to a recently published classification system for lumbar total disc replacement. For clinical parameters, the visual analog scale and the Neck Disability Index were evaluated preoperatively and 1 year postoperatively. The Student t test and Wilcoxon test were used for statistical analysis. RESULTS: In 26 treated segments (33.8%), no heterotopic ossification was detectable. Grade 1 ossifications were present in 6 levels (7.8%). A total of 30 segments (39.0%) showed grade 2 ossifications. Heterotopic ossifications that led to restrictions of the range of motion were present in 8 cases (10.4%). One year postoperatively, 7 cases (9.1%) had a spontaneous fusion of the treated segment. The clinical parameters improved significantly and were similar to previous reports about TCDR. CONCLUSIONS: Only 33.8% of the patients did not show any signs of heterotopic ossification, and the rate of spontaneous fusion after TCDR 1 year after surgery was unexpectedly high. There were 49.4% of the patients with grade 2-3 ossification, which lets us suspect an even higher rate of spontaneous fusion after long-term follow-ups. Motion preservation after TCDR is only guaranteed if spontaneous fusion can be prevented. Thus, mobility of the implanted segments needs to be further studied.

Cervical Vertebrae↗

PubMed2005

Development of adjacent-level ossification in patients with an anterior cervical plate.

BACKGROUND: It has been our experience that ossification occurs adjacent to anterior cervical plates. Our hypothesis was that the closer the plate is to the adjacent disc space, the greater the ossification. METHODS: We retrospectively reviewed the lateral radiographs of the cervical spine of 118 patients who had a solid fusion following an anterior cervical arthrodesis with a plate for the treatment of a degenerative cervical condition; none of the patients had had cervical spine surgery prior to the index arthrodesis. The plate-to-disc distance was measured on the postoperative lateral radiograph and was used to divide the patients into two groups for each of the two adjacent disc spaces. In group A the plate-to-disc distance was <5 mm, and in group B it was >/=5 mm. The mean duration of follow-up was 25.7 months. The severity of the ossification at the two adjacent disc spaces was classified on a scale ranging from grade 0 (no ossification) to grade 3 (complete bridging). Eighteen patients were excluded from the measurement of the severity of the caudal ossification because overlapping by the bone of the shoulder precluded adequate visualization of the caudal level. RESULTS: Ossification developed in seventy (59%) of the 118 cephalad adjacent disc spaces and twenty-nine (29%) of the 100 caudal adjacent disc spaces (p < 0.001). The mean cephalad plate-to-disc distance was shorter than the mean caudal plate-to-disc distance (p < 0.001). The rate of ossification was higher in group A than in group B, both at the cephalad adjacent disc spaces (67% compared with 24%) and at the caudal adjacent disc spaces (45% compared with 5%) (both p < 0.001). In addition, 93% (twenty-six) of the twenty-eight cases of moderate-to-severe ossification developed in group A. CONCLUSIONS: We found a positive association between adjacent-level ossification following anterior cervical plate procedures and the plate-to-disc distance. We now strive to place anterior cervical plates at least 5 mm away from the adjacent disc spaces in order to decrease the likelihood of moderate-to-severe adjacent-level ossification.

Adult↗

PubMed2000

Mechanobiology and joint conformity regulate endochondral ossification of sesamoids.

Sesamoid bones form by the endochondral ossification of sesamoid cartilages. This ossification process is thought to be similar to that responsible for the formation of secondary ossific nuclei in long-bone epiphyses. Sesamoids ossify much later in development than do epiphyses, however, and bone formation within sesamoids often begins by way of multiple ossific nuclei. Endochondral growth and ossification in the formation of secondary ossific nuclei have previously been correlated with distributions of the octahedral shear and hydrostatic stresses generated in vivo within cartilage anlagen. In this study, we used two-dimensional finite element analysis to predict the distributions of octahedral shear and hydrostatic stresses in an idealized model of a sesamoid cartilage subjected to in vivo loading. We examined the influence of sesamoid joint conformity. The distribution of an osteogenic stimulus was calculated with an approach similar to that used to predict epiphyseal ossification. The results suggest that, compared with conforming joints, nonconformity between the sesamoid cartilage and its articulating surface, which arises during early development, produces higher contact pressures within the sesamoid and leads to a thicker articular cartilage layer. For a nonconforming joint surface, the results suggest that ossification is favored anywhere within a broad internal region of the sesamoid, whereas a layer at the articular surface will remain cartilaginous. These findings highlight the subtle differences between ossification processes in epiphyses and sesamoids, indicating that the mechanical stress environment in sesamoids produces a diffuse stimulus leading to the onset of ossification and that the degree of joint nonconformity may influence the thickness of the articular cartilage layer.

Cartilage↗

PubMed2002

Ossification sequence in infants who die during the perinatal period: population-based references.

PURPOSE: To determine population-based references for the relationships between the presence of ossification centers and gestational age and skeletal length measurements among infants who die during the perinatal period, as well as to evaluate the possible influence of intrauterine growth restriction on ossification stage. MATERIALS AND METHODS: During an 11-year period, nearly all infants who died perinatally in a well-defined geographic area routinely underwent radiography with a standardized technique. The presence of visible secondary ossification centers in the singletons (n = 495) was evaluated. Cluster analysis was used to identify stages of ossification; a sequential appearance of secondary ossification centers was assumed. Comparisons were made with Wilks lambda between male and female infants and between infants who were presumed to have growth restriction and those who were not. Reference ranges for the presence of ossification centers were calculated for interquartile ranges of femur length and gestational age. RESULTS: Eight clusters of ossification defining different stages of ossification of the pelvis, hindfeet, and knees were identified. The sequential clusters outlined well-defined intervals of femur length and gestational age. Bone lengths, birth weight, and gestational age within ossification clusters did not differ between the sexes (Wilks lambda = 0.989, P =.532) or according to whether growth restriction was presumed to exist (Wilks lambda = 0.958, P =.481). CONCLUSION: The reference diagrams calculated with this method indicate relationships between ossification sequence and both gestational age and skeletal length measurements.

Birth Weight↗

PubMed1984

Fetal ossification centers as predictors of gestational age in normal and abnormal pregnancies.

The main fetal ossification centers appear ultrasonically as egg-shaped echo-rich areas. The calcaneal and talar ossification centers are seen at the level of the tarsus osseus, and the distal femoral epiphyseal and proximal tibial epiphyseal ossification centers are found at the level of the knee. Examination of 312 normal pregnancies between 20 and 40 weeks of gestation showed that the calcaneal ossification center was detectable for 24 weeks of gestation, the talar ossification center from 26 weeks, and the distal femoral epiphyseal and proximal tibial epiphyseal ossification centers, from 32 and 36 weeks, respectively. Corresponding figures found for 36 pregnancies showing intrauterine growth retardation (IUGR), examined between 34 and 40 weeks of gestation, were similar for the calcaneal and talar ossification centers but showed delays in the development of the epiphyseal ossification centers, which were particularly striking in cases of symmetrical IUGR. The amniotic fluid lecithin/sphingomyelin ratio was also evaluated in 51 normal pregnancies between 31 and 38 weeks of gestation and was found to be greater than or equal to 2 in every case where the distal femoral epiphyseal ossification center was greater than or equal to 6 mm in diameter. Evaluation of fetal ossification centers may be another useful means to evaluate gestational age in late pregnancy

Calcaneus↗