Scintigraphy using technetium-labelled methylene diphosphonate was performed on 110 scoliotic patients six months after an attempted fusion and the findings compared with those at exploration to detect the possible sites of pseudarthroses. The majority of patients (65 per cent) had a uniform uptake of isotope over the fused area and all but one had a solid fusion. A second group (35 per cent) had a more patchy uptake and eight of the nine patients with pseudarthroses were in this group. Pseudarthroses were detected as localised areas of increased uptake but there were also a number of false positives and scans that were difficult to interpret due to continuing new bone formation in immature fusions. In those scans performed after one year the pseudarthroses which had been missed were seen more clearly in contrast to the diminished generalised activity in the fused area

Demineralised homologous bone-matrix implant was used to bridge a large circumferential osteoperiosteal gap in the diaphysis of the ulna of rabbits. Periodic observations of the graft were made clinically, radiologically, histologically and by tetracycline fluorescence up to forty-two weeks. By the twelfth week after operation 81 per cent of the animals revealed bone formation in the implant and complete bridging of the gap. The new bone was laid on the surface and in the substance of the matrix, suggesting that the inductive principle was acting locally. The bone, once formed, remodelled to the texture of a mature tubular bone and did not undergo absorption during a long follow-up period. Demineralise bone-matrix proved to be a highly osteoinductive and readily osteoconductive material. The graft did not evoke any appreciable local foreign-body or immunogenic reaction. The high degree of success in bridging massive bone defects justifies further serious studies and hopes for a useful substitute for massive autologous bone grafts

1. Experiments are described in which total infarction of the epiphysis was produced in the metatarsal bones of growing rabbits. 2. After operation both proliferation and normal maturation of the cells of the growth plate were slowed or stopped. Cartilage destruction on the metaphysial side of the growth cartilage continued with consequent thinning of the cartilage. Localised areas of cell death appeared in the growth cartilage as early as the second day after operation. These increased in size and led to revascularisation of the epiphysis by metaphysial vessels which grew through the growth cartilage, reaching the epiphysis seven days after operation. The main, central part of the growth cartilage survived intact and its normal structure was restored after epiphysial revascularisation took place. Vessels growing into the bone from outside also contributed to revascularisation of the epiphysis. After revascularisation occurred, new bone formation led to increased radiographic density of the epiphysis

Aims

The purpose of this study was to evaluate the biological fixation of a 3D printed porous implant, with and without different hydroxyapatite (HA) coatings, in a canine model.

Objectives

Many in vitro studies have investigated the mechanism by which mechanical signals are transduced into biological signals that regulate bone homeostasis via periodontal ligament fibroblasts during orthodontic treatment, but the results have not been systematically reviewed. This review aims to do this, considering the parameters of various in vitro mechanical loading approaches and their effects on osteogenic and osteoclastogenic properties of periodontal ligament fibroblasts.

Extraskeletal bone formation can be induced in rodents by implantation of demineralised bone matrix and such implantation has been used to treat bone defects in man, but it is uncertain if induction or merely conduction occurs. We studied bone induction in primates by excising segments of the fibulae of adult squirrel monkeys, defatting and demineralising them before reimplanting them into the quadriceps of the same animal. As a control experiment, rat matrix was prepared in exactly the same way and implanted in rats. After six weeks the implants were harvested and either ashed and analysed for calcium content or prepared for histology. In the rats, the calcium content indicated that about 20% of the original matrix had been replaced by new bone. In the monkeys the calcium content was about the same as that in normal body fluid and no bone was seen in histological sections. This result casts doubt on the use of demineralised human bone matrix as a bone inductor, although it may function by other mechanisms

1. Experimental defects in the cranial vaults of young adult rabbits were implanted with decalcified, deproteinised and deep frozen homogenous whole bone. The experiments were similar to those of Ray and Holloway (1957) except that these workers used rats as the experimental animals. In addition, six control defects were made and not implanted. 2. All animals were killed six weeks after operation and thirty-four defects were studied by radiology and by histology. 3. All implants became surrounded by connective tissue and in all cases some new bone formed in apposition to implanted fragments. The degree of incorporation of the implants in new bone varied widely, not only between the three implanted groups, but also within each group. In general, new bone formation was greatest in defects implanted with deproteinised and whole bone, least in defects implanted with decalcified bone. 4. The fate of bone implants and the extent to which they can be said to induce osteogenesis are discussed

1. Cancellous bone cubes from calf and man were deproteinised with hydrogen peroxide and with ethylenediamine. 2. Long bones were removed aseptically from sheep, stored in the bone bank and used for cancellous homografts. 3. Holes were drilled in the upper part of the tibia or ulna or in the lower part of the femur of sheep. Some were left empty; others were filled with plugs of the deproteinised heterogenous bone, with autografts, or with homografts. 4. Histological appearances were studied after seventeen and thirty-six days. 5. At seventeen days repair was more advanced in the plugged holes; the biological result was better with the ethylenediamine-treated than with the peroxide-treated material. After thirty-six days repair was at an advanced stage. As much new bone had been deposited on the trabeculae of the deproteinised heterografts as on those of the homografts. 6. There was no evidence of metaplastic bone formation; new bone seemed to form from endosteal osteoblasts. 7. Certain clinical implications are briefly discussed

1. The detailed anatomy and calcification of the upper half of the tibia in rabbits varying in age from six weeks to twelve months has been studied. 2. The structure of the bone varies at different levels, but a section taken from the same level in the tibia from animals of the same age presents a reasonably constant picture. 3. It has been shown that this variation in structure at different levels is directly related to a difference between the axis of growth and the bone axis. This difference is a result of the unique shape of the tibia. 4. Autoradiographic studies confirm the localised concentration of radioactive strontium in areas of active bone formation where uptake is rapid. 5. The long retention of radioactive strontium in the skeleton (that is, the slow turnover) is a result of the slowness of resorption of bone (endosteal, periosteal or Haversian) in the cortex. Not only is the process slow but it is extremely localised. 6. The significance of these anatomical and physiological characteristics in relation to radiation injury is discussed

1. The capsular changes in osteoarthritis of the hip and their pathogenesis are described, and it is concluded that symptoms are due mainly to this abnormality. 2. The clinical significance and pathogenesis of subchondral sclerosis, cysts, osteophytes, secondary subluxation and new bone formation on the lower border of the femoral neck are discussed. 3. These bony features which can be seen in the radiograph may, under certain circumstances, be correlated with the symptoms. 4. The influence of joint debris and capsular fibrosis upon the symptoms arising in other osteoarthritic joints is considered. 5. The mechanism by which osteoarthritis develops in hip joints with an anatomical abnormality is discussed in relation to the normal functional anatomy of the hip. 6. The evolution of osteoarthritis in dysplasia of the hip is considered with special reference to its diagnosis, prognosis and early treatment. 7. The supposition that osteoarthritis is commonly due to progressive ischaemia in the femoral head has been investigated and is rejected. 8. The cause of idiopathic osteoarthritis remains obscure but the evidence suggests that constitutional rather than local conditions in the joint account for many of these cases

Bone loss around replacement prostheses may be related to the activation of mononuclear phagocytes (MNP) by prosthetic wear particles. We investigated how osteoblast-like cells were regulated by human MNP stimulated by particles of prosthetic material. Particles of titanium-6-aluminium-4-vanadium (TiAlV) stimulated MNP to release interleukin (IL)-1β, tumour necrosis factor (TNF)α, IL-6 and prostaglandin E. 2. (PGE. 2. ). All these mediators are implicated in regulating bone metabolism. Particle-activated MNP inhibited bone cell proliferation and stimulated release of IL-6 and PGE. 2. The number of cells expressing alkaline phosphatase, a marker associated with mature osteo-blastic cells, was reduced. Experiments with blocking antibodies showed that TNFα was responsible for the reduction in proliferation and the numbers of cells expressing alkaline phosphatase. By contrast, IL-1β stimulated cell proliferation and differentiation. Both IL-1β and TNFα stimulated IL-6 and PGE. 2. release from the osteoblast-like cells. Our results suggest that particle-activated mono-nuclear phagocytes can induce a change in the balance between bone formation and resorption by a number of mechanisms

Aims

To examine the relationship of sex steroid hormones with osteopenia in a nationally representative sample of men in the USA.

Aims

This single-centre observational study aimed to describe the results of extensive bone impaction grafting of the whole acetabular cavity in combination with an uncemented component in acetabular revisions performed in a standardized manner since 1993.

We designed an in vivo study to determine if the superimposition of a microtexture on the surface of sintered titanium beads affected the extent of bone ingrowth. Cylindrical titanium intramedullary implants were coated with titanium beads to form a porous finish using commercial sintering techniques. A control group of implants was left in the as-sintered condition. The test group was etched in a boiling acidic solution to create an irregular surface over the entire porous coating. Six experimental dogs underwent simultaneous bilateral femoral intramedullary implantation of a control implant and an acid etched implant. At 12 weeks, the implants were harvested in situ and the femora processed for undecalcified, histological examination. Eight transverse serial sections for each implant were analysed by backscattered electron microscopy and the extent of bone ingrowth was quantified by computer-aided image analysis. The extent of bone ingrowth into the control implants was 15.8% while the extent of bone ingrowth into the etched implants was 25.3%, a difference of 60% that was statistically significant. These results are consistent with other research that documents the positive effect of microtextured surfaces on bone formation at an implant surface. The acid etching process developed for this study represents a simple method for enhancing the potential of commonly available porous coatings for biological fixation

1. It is well known that the administration of corticosteroids may result in necrosis and progressive destruction of the femoral head. Identical changes have been found in chronic alcoholics, in South African negroes suffering from iron-overload osteoporosis and in patients with arthritis of the hip treated with non-steroid anti-inflammatory and analgesic preparations. The term "drug-induced arthropathy" is used to describe the common pathological lesion. 2. Seventy-two patients with this complication have been investigated and forty-two femoral heads were available for detailed study. The characteristic change is subchondral fragmentation and osteonecrosis, followed later by reactive bone formation and the typical increased radiographic density. 3. The frequent occurrence of fat occupying the Haversian canals in the affected femoral heads has not been adequately explained and its relationship to the destructive arthropathy remains obscure. The findings presented here do not support the theory that fat emboli are responsible for the subchondral bone changes. 4. More credence is given to the theory of subchondral microfracture in osteoporotic bone. The destructive arthropathy invariably follows the administration of some anti-inflammatory or analgesic preparation. It is postulated that a state of diminished sensibility predisposes to microtrauma in osteoporotic bone resulting in subarticular collapse of the femoral head

Aims

To investigate the benefits of denosumab in combination with nerve-sparing surgery for treatment of sacral giant cell tumours (GCTs).

We used an experimental rabbit model of leg lengthening to study the morphology and function of muscle after different distraction rates. Lengthening was in twice-daily increments from 0.4 to 4 mm per day. New contractile tissue formed during lengthening, but some damage to the muscle fibres was seen even at rates of less than 1 mm per day; abnormalities increased with larger rates of lengthening. There was proliferation of fibrous tissue between the muscle fibres at distraction rates of over 1 mm per day. Active muscle function showed adaptation when the rate was 1.0 mm per day or less, but muscle compliance was normal only after rates of 0.4 mm per day. Muscle responded more favourably at rates of distraction slower than those shown to lead to the most prolific bone formation. At present the rate of distraction in clinical practice is determined mainly by factors which enhance osteogenesis. Our study suggests that it may be advisable to use a slower rate of elongation in patients with poor muscle compliance associated with the underlying pathology; this will allow better accommodation by the contractile and connective tissues of the muscles

The role of three genetically distinct collagen types in the formation of endochondral bone and in calcification and resorption of cartilage has been assessed. Using antibodies specific to types I, II and III collagen we have demonstrated in the embryonic chick tibia that endochondral bone formation began with deposition of type III collagen in lacunae of hypertropic chondrocytes by invading bone-marrow-derived cells. This was followed by the deposition of type I collagen, which is the collagenous constituent of endochondral osteoid. At later stages of development endochondral osteoid was found in the epiphysial growth plate in apparently intact lacunae of hypertrophic chondrocytes; this indicated that the latter might contribute to the synthesis of osteoid type I collagen. Immuno-histological staining for collagen types, and von Kossa staining for calcium phosphate on parallel sections, demonstrated that type I and type II collagen matrices were substrates for calcification. Endochondral bone (with type I collagen) was found on scaffolding of both uncalcified and calcified cartilage (with type II collagen), indicating that calcification of endochondral osteoid and of the underlying cartilage occurred independentyl. Spicules of endochondral cancellous bone of a four-week-old chick contained a core of calcified type II collagen