Aims

This study aimed to examine the effects of tumour necrosis factor-alpha (TNF-α) on osteoblasts in metal wear-induced bone loss.

Objectives

Bioresorbable orthopaedic devices with calcium phosphate (CaP) fillers are commercially available on the assumption that increased calcium (Ca) locally drives new bone formation, but the clinical benefits are unknown. Electron beam (EB) irradiation of polymer devices has been shown to enhance the release of Ca. The aims of this study were to: 1) establish the biological safety of EB surface-modified bioresorbable devices; 2) test the release kinetics of CaP from a polymer device; and 3) establish any subsequent beneficial effects on bone repair in vivo.

Aims

In the context of tendon degenerative disorders, the need for innovative conservative treatments that can improve the intrinsic healing potential of tendon tissue is progressively increasing. In this study, the role of pulsed electromagnetic fields (PEMFs) in improving the tendon healing process was evaluated in a rat model of collagenase-induced Achilles tendinopathy.

1. Tendon possesses an active potential for repair and remodelling. 2. Large defects made in the flexor tendons of rabbits showed tenoblastic activity and repair without the formation of adhesions. 3. The failure to show this intrinsic ability for repair in previous studies may have been influenced by adverse factors introduced in order to hold the cut tendon ends together

1. The behaviour of various types of cortical bone graft has been studied in rabbits by histological and injection techniques. 2. The results suggest that penetration of the graft by blood vessels plays an important part in the incorporation of autogenous and homogenous grafts. 3. Autogenous and homogenous grafts are both incorporated–the latter more slowly than the former–but heterogenous grafts are rejected. The reasons for this rejection are discussed

New methods of limb lengthening are being adopted in the hope of overcoming the poor osteogenic responses characteristic of distraction. Delay between the osteotomy and starting distraction is said to be important but there is little experimental evidence. We have compared immediate with delayed distraction in the rabbit tibia and shown that delay is an important factor in promoting osteogenesis. It seems that its effects are partly mediated by an improvement in the extra-osseous blood supply

The effect of cortisone on the repair of simple muscle injury was studied in rabbits. The histological findings in the crushed muscle are described for a period up to twenty-one days after injury. Cortisone defers the onset of muscle regeneration, and retards its progress, but it does not change the course of the repair process or alter its eventual outcome under the conditions of the experiment. This apparent refractoriness of repair of muscle, as compared with that of other connective tissues, is discussed

Aims

Kashin-Beck disease (KBD) is a kind of chronic osteochondropathy, thought to be caused by environmental risk factors such as T-2 toxin. However, the exact aetiology of KBD remains unclear. In this study, we explored the functional relevance and biological mechanism of cartilage oligosaccharide matrix protein (COMP) in the articular cartilage damage of KBD.

1. Breech malposition and hormonal joint laxity produce atraumatic posterior dislocations in the hip joints of young rabbits. 2. Experimental studies were shown to cause the development of a limbus and other softtissue changes similar to those found in human congenital dislocations. 3. The development of femoral retroversion and anteversion in the presence of joint laxity is described. 4. The co-existence of breech malposition and hormonal joint laxity in utero, and their importance as prime factors in the etiology of congenital dislocation of the hip, are discussed

1. An experimental technique for the transplantation of epiphysial cartilage in the rabbit is described. 2. Autogenous transposition of the distal epiphysial cartilage of the ulna was followed by normal growth in five of eighteen animals. 3. Homogenous transplantation was unsuccessful in all the animals studied. 4. Homogenous grafting gives rise to an immunity reaction confined to the reserve Zone of the cartilage. 5. It is suggested that the difference between the fate of homogenous grafts of epiphysial and non-epiphysial cartilage lies in the vascularity of the former

1. The principal nutrient canal of the femur in day-old rabbits was occluded and subsequent femoral growth observed. 2. An initial shortening is followed by equalisation and a final absolute shortening of the order of 3 per cent in occluded femora as compared with controls. 3. It is emphasised that the medullary arterial system, fed by principal nutrient, metaphysial and epiphysial arteries, is the mechanism for the delivery of arterial blood to long bones, and that the arteries of bone extremities are of overwhelming importance in the nutrition of the long bone as a whole

We evaluated the effects of a serum protein coating on prosthetic infection in 29 adult male rabbits divided into three groups: control, albumin-coated and uncoated. We used 34 grit-blasted, commercially pure titanium implants. Eleven were coated with cross-linked albumin. All the implants were exposed to a suspension of Staphylococcus epidermidis before implantation. Our findings showed that albumin-coated implants had a much lower infection rate (27%) than the uncoated implants (62%). This may be a useful method of reducing the infection of prostheses

We measured the adenosine triphosphate (ATP) content of callus at various intervals during healing in 78 fractured tibiae in 10- to 12-week-old rabbits. The results, compared with the level in normal tissues, showed a high rate of energy metabolism in the early phase of fracture healing, which persisted until the callus was corticalised and remodelling had started. The ATP content could provide a more sensitive index to monitor fracture healing in animal studies. Our findings lend support to the need for nutritional supplements for patients with multiple fractures

In rabbits and goats, test implants with a porous surface of two layers of Tl-6A;-4V beads were examined at intervals for bond strength with bone. Half of the implants were coated with hydroxyapatite by plasma spray. The bonding strength with bone in the coated specimens was about four times greater than that of the uncoated specimens at two weeks, and twice as strong at six weeks. Twelve weeks after implantation, the strengths were similar. The hydroxyapatite coating of the beads provided earlier and stronger fixation

In 30 rabbits, the medial meniscus was used to replace the anterior or posterior cruciate ligament. The changes that took place were followed in histological sections, obtained both from the area of insertion into bone and from the intra-articular part of the graft. There was a gradual differentiation to chondroid tissue, with subsequent calcific deposition and no appearance of normal ligamentous tissue. The strength of the graft after 52 weeks was only one-quarter of that of the normal ligament. Our results do not justify the use of the meniscus to replace a torn cruciate ligament

The effect of early fusion on growth of the spine has been studied in rabbits. Free periosteal grafts from the tibia were transplanted either posteriorly between the spinous and articular processes or postero-laterally between the articular and transverse processes. Sound bony fusion was achieved in both the thoracic and the lumbar spine. Spinal fusion caused local narrowing and wedging of the intervertebral spaces, followed by retardation of growth and wedging of the vertebrae. A progressive structural scoliosis developed after unilateral postero-lateral fusion and a lordosis developed after posterior fusion

The effects on articular cartilage of continuous and intermittent excessive pressures have been studied in the knees of rabbits. Severe degenerative changes in the cartilage were observed; these resembled the typical lesions seen in osteoarthritis in man. They included fibrillation of cartilage, death of chondrocytes, eburnation of joint surfaces, sclerosis of bone and the production of "bone cysts." Regeneration of cartilage was common and it was brought about either by the deeply situated chondrocytes which had escaped death or by metaplasia of young connective tissue cells of the bone marrow

1. By reducing the viscosity of the synovial fluid within the ankle joints of rabbits and then subjecting these to prolonged exercise, wear and tear of articular cartilage can be consistently produced. 2. This finding is an indirect confirmation of the view that fluid film lubrication is an important factor in the mechanical efficiency of joints. 3. The special properties of synovial fluid and articular cartilage that allow fluid film lubrication to exist within joints that are, in effect, slowly moving, heavily loaded, reciprocating bearings are discussed. They account for the remarkable resistance to wear and tear exhibited by synovial joints under physiological conditions

We studied the effects of high-dose irradiation on the mechanical properties and morphology of cortical bone in rabbits for 52 weeks after a single dose of 50 Gy of electron-beam to the tibia. After four weeks, the bending strength of the irradiated bone was unchanged, but at 12 weeks, the strength had decreased significantly. At 24 weeks after irradiation mean strength was less than half of controls but by 52 weeks there was a tendency toward recovery. Similar, synchronous changes of damage and recovery were seen in cortical porosity, haematopoietic cells in the bone marrow and endosteal new bone formation