We compared the intracompartmental pressures (ICPs) of open and closed tibial fractures with the same injury pattern in a rabbit model. In all, 20 six-month-old New Zealand White male rabbits were used. They were randomised into two equal groups of ten rabbits; an open fracture group (group 1) and a closed fracture group (group 2). Each anaesthetised rabbit was subjected to a standardised fracture of the proximal half of the right tibia using a custom-made device. In order to create a grade II open fracture in group 1, a 10 mm segment of fascia and periosteum was excised. The ICP in the anterior compartment was monitored at six-hourly intervals for 48 hours. Although there was a statistically significant difference in ICP values within each group (both p < 0.001), there was no significant difference between the groups for all measurements (all p ≥ 0.089). In addition, in both groups there was a statistically significant increase in ICP within the first 24 hours, whereas there was a statistically significant decrease within the second 24 hours (p < 0.001 for both groups). We conclude that open tibial fractures should be monitored for the development of acute compartment syndrome to the same extent as closed fractures. Cite this paper: Bone Joint J 2013;95-B:111–14

Aims. Little is known about the effect of haemorrhagic shock and resuscitation on fracture healing. This study used a rabbit model with a femoral osteotomy and fixation to examine this relationship. Materials and Methods. A total of 18 male New Zealand white rabbits underwent femoral osteotomy with intramedullary fixation with ‘shock’ (n = 9) and control (n = 9) groups. Shock was induced in the study group by removal of 35% of the total blood volume 45 minutes before resuscitation with blood and crystalloid. Fracture healing was monitored for eight weeks using serum markers of healing and radiographs. Results. Four animals were excluded due to postoperative complications. The serum concentration of osteocalcin was significantly elevated in the shock group postoperatively (p < 0.0001). There were otherwise no differences with regard to serum markers of bone healing. The callus index was consistently increased in the shock group on anteroposterior (p = 0.0069) and lateral (p = 0.0165) radiographs from three weeks postoperatively. The control group showed an earlier decrease of callus index. Radiographic scores were significantly greater in the control group (p = 0.0025). Conclusion. In a rabbit femoral osteotomy model with intramedullary fixation, haemorrhagic shock and resuscitation produced larger callus but with evidence of delayed remodelling. Cite this article: Bone Joint J 2018;100-B:1234–40

We investigated the effect of locally administered bisphosphonate on distraction osteogenesis in a rabbit model and evaluated its systemic effect. An osteotomy on the right tibia followed by distraction for four weeks was performed on 47 immature rabbits. They were divided into seven equal groups, with each group receiving a different treatment regime. Saline and three types of dosage of alendronate (low, 0.75 μg/kg; mid, 7.5 μg/kg and high 75 μg/kg) were given by systemic injection in four groups, and saline and two dosages (low and mild) were delivered by local injection to the distraction gap in the remaining three groups. The injections were performed five times weekly during the period of distraction. After nine weeks the animals were killed and image analysis and mechanical testing were performed on the distracted right tibiae and the left tibiae which served as a control group. The local low-dose alendronate group showed a mean increase in bone mineral density of 124.3 mg/cm. 3. over the local saline group (analysis of variance, p < 0.05) without any adverse effect on the left control tibiae. The findings indicate that the administration of local low-dose alendronate could be an effective pharmacological means of improving bone formation in distraction osteogenesis

We have previously shown that joint distraction and movement with a hinged external fixation device for 12 weeks was useful for repairing a large articular cartilage defect in a rabbit model. We have now investigated the results after six months and one year. The device was applied to 16 rabbits who underwent resection of the articular cartilage and subchondral bone from the entire tibial plateau. In group A (nine rabbits) the device was applied for six months. In group B (seven rabbits) it was in place for six months, after which it was removed and the animals were allowed to move freely for an additional six months. The cartilage remained sound in all rabbits. The areas of type II collagen-positive staining and repaired soft tissue were larger in group B than in group A. These findings provide evidence of long-term persistence of repaired cartilage with this technique and that weight-bearing has a positive effect on the quality of the cartilage

Our aim was to investigate vascular endothelial growth factor (VEGF) expression after lacerations of a meniscus in a rabbit model. Specimens of meniscus were examined using immunohistochemistry, enzyme-linked immunoassay and the reverse transcription polymerase chain reaction after one, two, five or ten weeks. In the periphery of the meniscus 90% of the lacerations had healed after five and ten weeks, but no healing was observed in the avascular area. Expression of VEGF protein and VEGF mRNA was found in the meniscus of both the operated and the contralateral sites but both were absent in control rabbits which had not undergone operation. The highest expression of VEGF was found in the avascular area after one week (p < 0.001). It then lessened at both the vascular and avascular areas, but still remained greater in comparison with the control meniscus (p < 0.05). Despite greater expression of VEGF, angiogenesis failed at the inner portion. These findings demonstrated the poor healing response in the avascular area which may not be caused by an intrinsic cellular insufficiency to stimulate angiogenesis

Aim

Mesenchymal stem cells (MSCs) have several properties that may support their use as an early treatment option for osteoarthritis (OA). This study investigated the role of multiple injections of allogeneic bone marrow-derived stem cells (BMSCs) to alleviate the progression of osteoarthritic changes in the various structures of the mature rabbit knee in an anterior cruciate ligament (ACL)-deficient OA model.

We studied the effects of hyperbaric oxygen (HBO) and zoledronic acid (ZA) on posterior lumbar fusion using a validated animal model. A total of 40 New Zealand white rabbits underwent posterior lumbar fusion at L5–6 with autogenous iliac bone grafting. They were divided randomly into four groups as follows: group 1, control; group 2, HBO (2.4 atm for two hours daily); group 3, local ZA (20 μg of ZA mixed with bone graft); and group 4, combined HBO and local ZA. All the animals were killed six weeks after surgery and the fusion segments were subjected to radiological analysis, manual palpation, biomechanical testing and histological examination.

Five rabbits died within two weeks of operation. Thus, 35 rabbits (eight in group 1 and nine in groups 2, 3 and 4) completed the study. The rates of fusion in groups 3 and 4 (p = 0.015) were higher than in group 1 (p < 0.001) in terms of radiological analysis and in group 4 was higher than in group 1 with regard to manual palpation (p = 0.015). We found a statistically significant difference in the biomechanical analysis between groups 1 and 4 (p = 0.024). Histological examination also showed a statistically significant difference between groups 1 and 4 (p = 0.036).

Our results suggest that local ZA combined with HBO may improve the success rate in posterior lumbar spinal fusion.

Aims

We aimed to evaluate the temperature around the nerve root during drilling of the lamina and to determine whether irrigation during drilling can reduce the chance of nerve root injury.

The method of producing osteogenic sarcoma in rabbits by the injection of beryllium in the form of "zinc beryllium silicate" is presented. In five of ten animals which had such injections, osteogenic sarcomas developed several months later. There was new bone formation in the medullary cavities of the long bones before malignant changes were apparent. It is of particular interest to note that there was atrophy of the spleen in those animals in which bone tumours developed, whereas the spleen seemed to be quite normal in the rabbits which did not develop bone tumours. The tumours usually developed in the metaphysial regions. More than one tumour often developed in the same animal.

We investigated whether strontium-enriched calcium phosphate cement (Sr-CPC)-treated soft-tissue tendon graft results in accelerated healing within the bone tunnel in reconstruction of the anterior cruciate ligament (ACL). A total of 30 single-bundle ACL reconstructions using tendo Achillis allograft were performed in 15 rabbits. The graft on the tested limb was treated with Sr-CPC, whereas that on the contralateral limb was untreated and served as a control. At timepoints three, six, nine, 12 and 24 weeks after surgery, three animals were killed for histological examination. At six weeks, the graft–bone interface in the control group was filled in with fibrovascular tissue. However, the gap in the Sr-CPC group had already been completely filled in with new bone, and there was evidence of the early formation of Sharpey fibres. At 24 weeks, remodelling into a normal ACL–bone-like insertion was found in the Sr-CPC group. Coating of Sr-CPC on soft tissue tendon allograft leads to accelerated graft healing within the bone tunnel in a rabbit model of ACL reconstruction using Achilles tendon allograft.

Cite this article: Bone Joint J 2013;95-B:923–8.

1. Degenerative arthritis has been produced consistently in adult rabbits by the injection of the proteolytic plant enzyme papain into the hip joint. Arthritic changes were recognisable radiographically after six weeks.

2. A progression of changes occurred, from loss of acid mucopolysaccharide staining in the matrix, fibrillation, fissuring and erosion of articular cartilage with death of chondrocytes in the weight-bearing areas, to secondary bony changes of subchondral sclerosis, occasional cysts and osteophyte formation.

3. Synovial inflammation occurred with accumulation of cartilage and bone debris in the inferior capsule and later capsular thickening.

4. It is suggested that this arthritis is sufficiently similar to human osteoarthritis to be useful as a model for further studies of the pathogenesis of the disease and the effects of different methods of treatment.

1. In two-month-old rabbits the femoral heads were made necrotic by transecting the ligament of the femoral head and applying a ligature around the femoral neck. The animals were killed at different periods, from six hours to twenty-one weeks after the operation. The changes in the femoral heads were studied histologically, microradiographically and radiographically.

2. In the first three weeks the necrotic bone marrow was penetrated by granulation tissue in which cellular differentiation gradually developed. Subsequently large quantities of new bone were deposited on the dead trabeculae. This led to an increase in the bone volume at the expense of the marrow volume; this increase coincided with an increase in the radiographic density (sclerosis) of the femoral head. The new bone tissue was attached to the necrotic trabeculae by a specific cement line and showed the features of woven bone. At a later stage lamellar bone was deposited. From six weeks on a normal bone-marrow ratio was gradually restored with concomitant radiographic loss of sclerosis.

3. It is suggested that mechanical weakening of the femoral head is the consequence of this late post-operative restoration of the normal pre-operative bone-to-marrow ratio, the new bone trabeculae being mechanically inferior because of the presence of woven bone and cement lines. This weakness may initiate collapse and deformation of the revascularised femoral head.

1. The source of nutrition of articular cartilage still remains a subject of controversy.

2. Experiments are described in which an attempt to demonstrate the direct transfer of fluid from the subchondral bone has been made using 355 and an autoradiographic technique. These experiments were based on ones originally performed by Ekholm (1951), except that two distinct groups of animals were used : immature rabbits and adult rabbits whose skeletons were mature.

3. The transfer of fluid to the cartilage could be demonstrated only in the immature rabbits.

4. It is suggested that some of the conflicting opinions which have been advanced on this subject stem from a failure to distinguish between mature and immature joint cartilage. Subchondral nutrition is a feature only of the immature animal.

1. Transplantations of autografts and of Kiel bone to the iliac bone and to muscle tissue were performed in rabbits. Through labelling with two tetracycline compounds which have different fluorescent colours in ultraviolet light, bone formation between the labelling periods could be followed.

2. It was shown that bone formation between the fifth and the tenth day after transplantation to bone took place in about 50 per cent of the fresh autografts. Storage of the transplants in saline for one hour before replacement had little adverse effect, whereas exposure to air for one hour seemed to reduce the osteogenic effect of the grafts. Bone formation was not observed in grafts of Kiel bone during this period.

3. The fact that new bone formation in fresh autografts could be demonstrated even during the first four days after transplantation to bone indicates that osteogenic cells from the fresh autografts continue their activity under favourable conditions. This is supported by microradiographic and histological evidence.

4. The amount of callus which developed in close contact with the grafts during the first ten days after transplantation to bone was more pronounced both in fresh autografts and in autografts kept in saline than in autografts exposed to air for one hour. Callus developing at a later stage showed no significant difference between the various grafts, including those of Kiel bone.

5. In fresh autografts transplanted to muscle tissue callus formation could be demonstrated in most cases by the tenth day, indicating either survival of osteoblasts or the transformation of more primitive cells from the graft or from the host bone into osteogenic cells. No bone formation was observed when Kiel bone was embedded in muscle tissue.

The growth plates of the femoral head of Japanese white rabbits aged 5, 10, 15 and 20 weeks were stained for apoptotic and proliferating chondrocytes using the TUNEL and PCNA antibody staining techniques. Both TUNEL- and PCNA-positive chondrocytes were detected in all of the specimens. The positive ratios of both stainings were calculated for the whole plate and for the resting, proliferating and hypertrophic zones. The highest ratios in both stainings occurred in the hypertrophic zone in all age groups. With growth, the TUNEL-positive ratio increased whereas the proliferating ratio decreased.

We suggest that the increase in chondrocytic death by apoptosis and the decrease in cell proliferation potential led to closure of the growth plate.

1. Synovitis was induced in the hip joints of fifty-six rabbits by the intra-articular injection of surgical talc. The opposite hip joint and eleven suitable"sham" operations served as controls.

2. The results in the hips injected with talc were as follows. Widening of the medial joint space and sometimes acetabular changes were seen; enlargement of the femoral head and neck in two planes was found, with, in most cases, flattening of the superior aspect of the head; there was thickening of the joint cartilage and sometimes deformity of the capital epiphysis; thickening of the cartilage was the main cause of the coxa magna, cervix magna and ischium magnum.

3. The embryology, micro-anatomy and development of the hip joint is reviewed and attention is drawn to the configuration of the layers of germinal cartilage cells. The effect of an induced synovitis in producing hyperplasia of the joint cartilage, incongruity of the articulating surfaces and subsequent subluxation is discussed.

1. An investigation was made of the tolerance of the cells in the femoral head in rabbits for ischaemia brought about by transecting the ligament of the femoral head and applying a ligature around the femoral neck. The animals were killed two, six, twelve, twenty-four and seventy-two hours after operation.

2. In the cells of the bone marrow and in the osteoblasts distinct histological signs of disintegration were present six hours after operation. Pyknosis of the osteocyte nuclei was found after twenty-four hours' ischaemia; sometimes vacuolar clarifications could be observed in these pyknotic nuclei. After three days of ischaemia the staining affinity for Feulgen and haematoxylin of a number of osteocyte nuclei had visibly decreased.

3. The Feulgen-DNA content of the osteocyte nuclei-as measured in individual nuclei by means of an integrated microdensitometer-was significantly reduced as compared with similar nuclei from the control side as early as after six hours of ischaemia. This DNA loss was progressive with the period of ischaemia. From these facts, the conclusion was reached that in the femoral head of the rabbit the period of reversible damage for osteocytes must have ended within six hours.

1. A quantitative study of phosphatase distribution in the limb bones of growing rabbits is reported.

2. Alkaline phosphatase is present in high concentrations in areas of deposition of new bone. Both local concentrations and the total alkaline phosphatase content of a bone are found to decrease with age. There is good correlation between total alkaline phosphatase activity and monthly increment of weight.

3. Acid phosphatase is present in these bones in greatly less concentrations than alkaline phosphatase.

4. The acid phosphatase of bone shows nearly full activity in the presence of 0·5 per cent formaldehyde. It can be subdivided into two enzymes with characteristically different distributions by the effect of M/100 tartrate on activity.

5. The formaldehyde-stable and tartrate-stable acid phosphatase of rabbit bone (FTS) has a distribution very similar to that of alkaline phosphatase, though very much less in amount, and, like the latter, declines in activity as the bone matures.

6. Tartrate-inhibited, formaldehyde-stable acid phosphatase (FSTI) is found mainly in red marrow and cancellous bone, and full activity persists in mature bone. This enzyme may be associated with resorption and remodelling of bone, or it may represent residual activity under these conditions of the acid phosphatase of developing erythrocytes in the marrow.

The experiments showed that the administration of sodium citrate retards fracture healing. This is probably due to a change in the solubility of the calcium or to a relative calcium deficiency on account of the excretion in the urine, or to a combination of both factors. Other reasons cannot, however, be excluded, such as a biochemical effect on the ground substance or an enzyme deficiency.