Pattern Of Bone Remodeling Research Articles

Roentgenographic Features of Digitized Clinical Orthopaedic Radiographs of Follow-up After Total Hip Arthroplasty

When a patient undergoes an arthroprosthesis implant, the stresses acting on the bone are redistributed, and correspondingly, the bone density adjacent to the entire prosthesis changes its pattern. In order to study these phenomena an automatic methodology has been developed: this methodology is based on the bone density measured on X-ray. The method is compared to other bone densitometry methods and to more recent bone remodeling pattern recognition methods; it turns out to be cost-effective and it has the advantage of allowing back-dated investigation exploiting the numerous existing radiograph records relative to arthroplastic follow-up. The results of the set-up videodensitometric analysis show the method not only has diagnostic capability, but also can effectively support prostheses designers; moreover, the results obtained offer a capable support to real-time observation of remodeling processes and to the biomechanical assessment of the behavior of bone implant systems.For the clinical practice a risk index has been set up in order to systematize the numerous data collected from the measuring mesh grids and to monitor dangerous situations, which can end in implant failure.

Remodelling and pain after uncemented total hip replacement.

We studied 70 patients after uncemented hip replacement with the Lord prosthesis which has a relatively long, completely macrotextured stem. The mean follow up was for 9.5 years. We compared radiographs at one year after operation, at 5 years and at the last follow up. Twenty-five patients (36%) had deep or circumferential pain in the thigh. Of the 44 who were most active at 5 years those with thigh pain had less proximal cortical loss than those without (p < 0.05), most cortical bone formation distally and most often had incomplete radiolucent lines at the mid-stem level, perhaps indicating more elastic displacement of the bone relative to the prosthesis. The presence of radiolucent lines correlated with the increase in cortical width at 5 years (p < 0.01). Cortical remodelling continued after 5 years at all levels except at the tip (p < 0.01). The relative elastic displacement at the interface could cause pain and may contribute to the pattern of bone remodelling in the femur after uncemented hip replacement.

BONE GROWTH AND REMODELLING AFTER FRACTURE

We used a rabbit model to investigate the mechanism by which the angulation of fractures is corrected in children. We produced a transverse proximal tibial fracture in one leg of 12 eight-week-old New Zealand white rabbits and measured bone alignment and length and the patterns of bone growth and remodelling. The angle between the joint surfaces changed rapidly to correct the alignment of the limb as a result of asymmetrical growth of epiphyseal plates. In an adult with closed plates, the angle between the joint surfaces cannot therefore improve. The angle at the fracture itself showed slow improvement because of bone drift and the asymmetrical growth of the epiphyseal plates. Remodelling corrected the shape of the bone in the region of the fracture. Periosteal division on the convex side increased the growth of the epiphyseal plate on that side, thus slowing the correction. The effect was relatively small, providing an indication that factors other than the periosteum are important in inducing correction. External torsional deformities developed because of helical growth at the plate. This was probably caused by abnormal posture which induced a torque at the growth plate. Helical growth is the mechanism by which rotational deformities can occur and correct.

Stress in bone adjacent to dental implants.

Finite element analysis (FEA) was employed to assess patterns of stress in bone adjacent to an implant after application of loads through an attached distal extension cantilever. Under all loading conditions, the highest stresses occurred at the distal cervical bone margin adjacent to the cantilever. In clinical studies, this is not consistently the site of the greatest bone changes seen radiographically. This suggests that extrapolation of FEA studies to clinical implantology should be approached with caution until further data become available on both mechanical properties of bone and patterns of bone remodelling induced by defined functional stresses in mandible and maxillae.

Altered bone remodeling pattern of the residual ridge in ovariectomized rats

This study investigated the effect of estrogen deficiency on residual ridge remodeling after tooth extraction. Ovariectomy was performed on female Sprague-Dawley rats, and the plasma levels of estrogen and progesterone were monitored. The maxillary molars of the ovariectomized and control rats were extracted and the remodeling residual ridge tissues were harvested at 2, 4, and 8 weeks postextraction. The specimens were examined at the mesiodistal center point of the residual ridge by use of light and scanning electron microscopy. The surface of the residual ridge of the control animals showed a number of osteoclastic lacunae indicating bone resorption activity. In the ovariectomized animals, the surface of the residual alveolar bone was partially covered by a distinct calcified tissue. This tissue contained large cells and a meshlike structure of thin calcified extracellular matrix consistent with the tissue characteristics of chondroid bone. The chondroid bonelike calcified tissue was found only in the ovariectomized animals throughout the experiment period. This study's data suggest that a systemic condition such as estrogen deficiency due to ovariectomy may alter the phenotypic expression of cells associated with the residual ridge and result in less osteoclastic activity and a different type of calcified tissue.

Mandibular reconstruction with the Dacron urethane tray: A radiologic assessment of bone remodeling

A retrospective study was made of 22 consecutive patients who underwent mandibular reconstruction with a Dacron (Osteo-mesh, Xomed Inc, Jacksonville, FL) tray technique from September 1988 to April 1992. Free autogenous iliac bone, in the form of particulate cancellous chips and marrow, was densely packed into the Dacron tray, that was adapted to bridge the mandibular segmental defect. Sixteen cases underwent uneventful healing with the formation of a continuous bony bridge and union with the remaining mandible. The pattern of bone remodeling and rate of resorption in these cases were assessed by sequential panoramic radiographs taken up to 3 years postoperatively. The mean horizontal dimension of the mandibular defects was 75 mm and the mean vertical reconstructed height was 25 mm. When the grafted bone was radiographically of uniform density, it progressed into a mature trabecular pattern matching that of the normal mandible. However, when there were areas of radiolucency, most likely from inadequate condensation of the graft, such areas were not replaced by bone in the long term. The bony height at both ends and the middle of the reconstructed segment underwent reasonably even resorption and retained about 80% of the bony height over a 3-year period. The rate of resorption was highest in the first 6 months and stabilized at about 2 years. There were six failures, all showing significant irregular bony resorption prior to tray removal.

Roentgenographic Densitometry of Bone Adjacent to a Femoral Prosthesis

A digital imaging method was developed to quantitate the stress-related changes in roentgenographic bone density after total hip arthroplasty. A technique termed "histogram-directed equalization" was used to compensate for differences in postimaging data caused by the effects of variable quality obtained from ten patients. Quantitative change due to variation in delivered energy was decreased by 7% for roentgenograms obtained with a 2 kVp variation and 31% for roentgenograms obtained with a 4 kVp variation. The method allowed the authors to accurately describe the changes observed on annual postoperative roentgenograms obtained over the past decade. The utility of the method was demonstrated in 15 of the senior author's long-term cases treated with fully porous-coated implants. These cases were divided into two groups based on the diameter of the prosthetic stem implanted in each case. Five patients were grouped with small-diameter stems and ten with large-diameter stems. Both groups showed substantial decrease in roentgenographic bone density (from 11% to 28%) in the medial and lateral proximal regions. The large-diameter group had an overall larger decrease in roentgenographic bone density at two and five years. Roentgenographic bone remodeling changes were most pronounced in the first two years. Changes between two and five years progressed at a slower rate. The results also confirmed the predicted effect of stem diameter on bone remodeling patterns.

Determinants of Stress Shielding

Experimental studies of cementless porous-coated total hip arthroplasty indicate that a critical design variable for femoral remodeling is stem stiffness. In the long term (two years) in the canine model, other variables, including the presence, type, and placement of the porous coating, did not significantly affect the pattern of bone remodeling when tested with metallic stems. The basic pattern of bone remodeling was characterized by proximal cortical atrophy, and distal cortical and medullary bone hypertrophy. In the short term (six months), the use of low-stiffness stems altered this pattern, leading to reduced proximal bone loss, increased proximal medullary bone hypertrophy, and no distal cortical hypertrophy, suggesting that stem stiffness had a profound effect on stress shielding.

Anatomical observations on the attachment of human temporalis and masseter muscles

It is very important for orthodontics to investigate the bone remodeling pattern in the area of the attachment of the masticatory muscles induced by the changing muscular function. In the present study, the insertion pattern of Sharpey's fibers and the bone structure are comparatively studied on the temporalis and the masseter muscles macroscopically, light microscopically and electron microscopically, respectively. The following results are obtained: 1) The periosteum on the squamous part of the temporal bone is thinner, while the one on the lower ridge of the zygomatic arch is relatively thicker. 2) The fine and loose Sharpey's fibers are found mostly on the squamous part of the temporal bone, while the ones on the lower ridge of the zygomatic arch are relatively coarse and dense. 3) Comparing with the squamous part of the temporal bone, the fibrous bone is thinner and also few reversal lines and resting lines are observed at the lower ridge of the zygomatic arch. These findings seem to prove the fact that the bone remodeling proceeds frequently within the limited narrow area. These differences are directly due to the differences of the anatomical site and the muscular function.

Producing and Avoiding Stress Shielding

Experimental canine model studies of stiff versus flexible, fully porous-coated, metallic femoral stems (differing by three- to fivefold in stiffness characteristics) revealed markedly different resorptive bone remodeling patterns. The flexible stem resulted in about 30% more cortical bone retention adjacent to the implant at one-year postimplantation and larger differences in dogs killed two and three years after surgery. Strain-gauge studies confirmed that there are differences in cortical bone strains with the two stem designs, the flexible stem producing a more uniform and more nearly normal strain distribution medially. Differences in cortical bone remodeling were quantified using dual energy X-ray absorptiometry (DEXA). The bone mineral content in femora with the flexible stem decreased less than 20%, compared to normal. At three years postimplantation, the bone mineral content of the femora with the stiff stem was about 50% that of the femora with the flexible stem. Clinically, DEXA revealed that 5%-15% changes in bone mineral density at various periimplant sites were common within the first two years after surgery; these changes were not usually evident roentgenographically. Serial roentgenographically distinct bone resorption was usually associated with bone mineral density changes of 20%-50%. Five- to 13-year roentgenographic follow-up observations of 213 cases with the Anatomic Medullary Locking prosthesis showed that pronounced bone resorption occurred in 33% of patients. Larger stems (greater than 13 mm in diameter) and stems with extensive porous coating had a significantly higher incidence of pronounced bone resorption than smaller stems and those with proximal coating. The stiffness characteristics of the human femur were established as a function of canal size and compared with those of noncemented hip prostheses. Increased mechanical compatibility was found for stems made of titanium alloy and with design features that reduce cross-sectional area and moment of inertia. Clinical data suggest that to reduce the likelihood of pronounced bone resorption, it would be beneficial for the implant to possess a bending stiffness of about one half to one third that of the human femur.

New bone formation and cancer implants; relationship to tumour proliferative activity

The interaction between tumour and bone with respect to the proliferative activity of transplanted tumour cells was studied using five transplantable human urogenital tumours in nude mice. Cells from those tumours were injected subcutaneously over the calvaria of nude mice following disruption of the periosteum. The extent of tumour-bone interaction varied with the type of implanted tumour as shown on X-ray and by histologic examinations of the calvaria. The classic histologic pattern of bone remodelling including the destruction of bone with proliferation of osteoclasts and reactive new bone formation was seen with all five tumours. Tumour proliferative activity determined from the tumour doubling time and the S-phase fraction using bromodeoxyuridine labelling showed that the rate of reactive bone formation appeared to be inversely proportional to the rate of tumour cell proliferation.

Calvarial Sutural Abnormalities

The purposes of this study were (1) to evaluate the histologic differences between synostotic versus deformational suture abnormalities and (2) to correlate these histologic findings with anatomic and three-dimensional computed tomographic (CT) scans. We examined three infants with premature metopic synostosis; one infant also had microcephaly trisomy 13 and curious overriding of the coronal sutures. The three-dimensional CT scans demonstrated obliteration of the metopic suture inferiorly. Histologic sections of this suture showed complete bony stenosis. The same pattern was found in all three infants, including the two infants with trigonocephaly who did not have trisomy 13 or microcephaly. In the trisomy 13 infant, the overlapped inferior coronal suture was obliterated on CT examination. However, histologic sections in this region showed a merging of bone; there was no synostosis. In summary, three-dimensional CT re-formation correlated with metopic suture histology. "Stenotic" fusion existed in all infants with trigonocephaly, those with normal and abnormal karyotypes, with and without microcephaly. However, three-dimensional CT re-formation of the trisomic infant showed opacification of the coronal suture in the areas of greatest overlap, whereas histology revealed a curious bone remodeling pattern, possibly a precursor to "deformational" craniosynostosis.

Regional patterns of bone loss and altered bone remodeling in response to calcium deprivation in laboratory rabbits

This study explores the effects of a calcium-deficient diet on patterns of bone remodeling, and examines regional differences in the amount of bone lost. Skeletally mature female rabbits (n = 6) were fed a calcium-deficient diet (0.10% Ca2+ and 0.50% P) for 14 weeks. A separate group of rabbits (n = 4) were fed a maintenance diet (1.2% Ca2+ and 0.45% P). Bone mineral content, serum calcium, and serum phosphorus were measured each week during the experimental period. Following sacrifice, the L3 vertebra, femoral head, proximal tibial metaphysis, and tibial midshaft were analyzed histomorphometrically. Rabbits had 20% less vertebral bone after only 14 weeks of a calcium-deficient diet. As in human postmenopausal osteoporosis, bone loss in calcium-deficient rabbits occurs in the trabecular bone of the lumbar spine before that in the trabecular bone of the lower extremity. Calcium-deficient diets alone do not lead to increased osteoid volume or thickness. Because bone loss is relatively rapid and because the pattern of loss is similar in some respects to that found in humans, adult rabbits may provide an attractive model of calcium deficiency osteoporosis in a skeletally mature mammal in which remodeling is predominant over modeling.

Muscle function as a determinant of mandibular growth in normal and hypocalcaemic rat.

The aim of the present investigation was to study the influence of low muscle function on the form, growth and structure of the mandible in rats with a metabolic bone disturbance due to hypocalcaemia. Growing rats were randomly divided into four groups where two factors were combined: hard or soft diet consistency to normal or calcium deficient diet. The experimental period was 30 days. At day 0 and day 15 the animals were injected with oxytetracycline. At the end of the experiment X-rays were taken from the mandibles for cephalometric analysis and the bone remodelling pattern was studied under a fluorescence microscope and with help of microradiograms. The cephalometric analysis showed that calcium deficiency was an unfavourable factor for the growth of the mandible as a whole, while muscle function was a significant factor affecting the angular and the condylar processes. General decreased bone apposition and increased endosteal resorption were found in the two calcium deficient diet groups. The cortical bone in these groups was thinner and the trabecular system sparser than in the two normal diet groups. The hard diet groups had higher bone apposition rate and better organized trabecular system than the respective soft diet groups. It was concluded that changes in the mechanical strain environment of the mandible, caused by reducing the vigorous mastication, is a powerful determinant of remodelling behaviour at certain sites, even in situations when a metabolic bone disturbance exists.

Tumor-bone interaction induced by transplantable human tumors in nude mice.

Tumor-bone interactions were experimentally studied using four transplantable human urogenital tumors in nude mice. The method consisted of subcutaneously (SC) inoculating tumor cells over the calvaria in nude mice after the periosteum has been disrupted. This resulted in a local tumor causing fragmentation of the bone. The degree of tumor-bone interaction also varied with the type of implanted tumors as shown in radiographic and histologic examinations. All tumors were associated with histologic patterns of classical bone remodeling, including bone destruction with osteoclast proliferation and reactive new bone formation. The evidence presented here suggests that the majority of tumor-bone interaction showed a combination of both features, bone destruction and new bone formation, and the mechanisms whereby tumors interact with bone may vary with the biological properties of the tumor. Our new system would be suitable for studying the biology of local interaction between bone and tumor cells and searching out a method to protect the bone from cancer cells.

Annual skeletal changes in the little brown bat, Myotis lucifugus lucifugus, with particular reference to pregnancy and lactation.

Studies of bone from summer-active little brown bats, Myotis lucifugus lucifugus, have demonstrated sex differences in the renewal of skeletal mineral reserves following spring-arousal from hibernation. Patterns of bone remodeling in both sexes of bats indicate that new bone formation does not occur during hibernation: All new bone formation occurs during the summer-active season. Results show that a short period of time elapses after hibernation before the initial demands of a large fetus and rapidly growing neonate are expressed on maternal skeletal reserves. Bone loss in summer-active females was associated with pregnancy and lactation, whereas summer-active males did not show evidence of bone loss but, instead, uninterrupted bone accretion throughout the summer-active season. Osteoclasts and bone-forming osteoblasts, absent during the hibernation period, reappeared on bone surfaces following spring-arousal from hibernation. There was no apparent increase in osteoclast numbers or activity during lactation but resorption cavities were found in deep cortical lamellae distant from bone surfaces. The increase in bone resorption in lactating bats appeared to be by osteocytic osteolysis, suggesting that it might be a significant mechanism of bone/calcium regulation in this hibernating mammal throughout the year.

Activation of the vascular system: A main mediator of periodontal fiber remodeling in orthodontic tooth movement

The behavior and role of blood vessels and blood-borne cells in the process of the remodeling of the periodontal ligament (PDL) incident to experimental tooth movement was studied in rats. Particular interest was focused on areas of tension and of pressure with frontal bone resorption but without overt hyalinization. An increase of vascular activity occurred in the above mentioned situations. Extensive breakdown of collagen was observed in pressure areas with frontal resorption and in areas of tension concomitant with vascular invasion. Two patterns of fiber and bone remodeling were seen in areas of tension: (1) intense vascular activity within the periodontal membrane and (2) intense vascular activity inside the alveolar bone. Macrophages occurred consistently near blood vessels both in areas of tension and in areas of resorption. These are multipotent cells that obviously influence the remodeling process.

Ethmoid sinus disease: CT evaluation in 400 cases. Part I. Nonsurgical patients.

The unique anatomy of the ethmoid sinuses makes it difficult to interpret "soft-tissue clouding," especially on plain films. The clinical significance of isolated or generalized soft-tissue disease within ethmoid cells is unclear, and the patterns of bone erosion or remodeling must be relied on in establishing a specific differential diagnosis. Of 400 patients studied, 186 had inflammatory disease and 214 had tumors. Squamous cell carcinomas, metastases, and a few aggressive sarcomas were found almost exclusively to have bone destruction, while 94% of the remaining neoplasms were characterized by cavity remodeling. Further differentiation was sometimes possible because of the pattern and degree of tumor enhancement. Of the neoplasms, only the minor salivary gland lesions and neuromas had nonhomogeneous enhancement. Malignant lesions cannot be diagnosed with computed tomography (CT) unless bone destruction is present. Similarly, although the significance of persistent, benign-appearing soft-tissue disease during chemotherapy is unclear, tumor must always be suspected, even after many months of a stable CT appearance.

The cellular basis of metastatic bone disease in patients with lung cancer.

Histologic patterns of tumor-bone interaction were systematically evaluated in 80 cases of metastatic lung cancer involving bone. Patterns of tumor-bone interaction varied with the histologic type of lung cancer, reflecting the biochemical and biologic differences among the different types of lung cancer. Evidence presented here suggests that destruction of bone by metastatic lung cancer is mediated neither by direct contact of tumor cells with bone matrix nor by release of diffusible substances that lyse bone matrix. Among indirect mechanisms, the most prevalent and important was the activation of bone-lining cells by metastatic tumor. Epidermoid carcinomas in particular were associated with histologic patterns of classical bone remodelling, including osteoblastic, osteoclastic, and osteocytic activity. Adenocarcinomas showed a particularly high association with microfractures and manifested a stromal pattern consistent with release of prostaglandins. Ischemic necrosis of bone due to compression of vessels by expanding tumor mass is also a common and important mechanism. Correlation of histologic patterns with reported data on the frequency of metastases and syndromes of ectopic hormone production provides insight into the mechanism(s) of paraneoplastic hypercalcemia in patients with lung cancer.

Translative and transformative growth of the rat mandible.

The growth of the rat mandible was studied during a period from 14 to 30 days of age. Roentgencephalometric and alizarin vital staining techniques were employed. Growth in length doubles the growth in breadth; the angle between the mandibular halves decreases slightly. Bone remodeling patterns were revealed with the alizarin technique. Posteriorly facing surfaces and the anterior end of the incisal process show apposition. Lateral facing surfaces of the posterior part of the mandibles were resorptive. A medio-posterior growth direction of these parts were found. The intermandibular articulation plays no role in the translative growth movements, in contrast to other articulations between skull bones as sutures and synchondroses, but serves primarily during biting and chewing.