Inhibition of partial closure of epiphyseal plate in rabbits by indomethacin

Parecoxib has non-significant long-term effects on bone healing in rats when administered for a short period after fracture

INTRODUCTION

Selective and non-selective cyclo-oxygenase (COX) inhibitors impair bone healing by inhibiting prostaglandin synthesis. The purpose of this study was to evaluate the long-term effect of parecoxib, a selective COX-2 inhibitor, on bone healing in rats, when it is applied in a pattern similar to clinical treatment patterns, that is, in a high dose and for a short period after bone fracture.

METHOD

Closed non-displaced mid-diaphyseal fractures in the middle of the left femoral shaft were generated in each animal. In the study group, parecoxib sodium (1.06 mg/kg) was administered intra-peritoneally every day for 7 days. In the control group, normal saline was administered intra-peritoneally every day for 7 days. In both groups fracture healing (bone union and callus formation) was evaluated with X-rays 28 and 42 days after surgery.

RESULTS

Bone healing was lower in the study group (60 vs. 80% in the control group 28 days after fracture and 80 vs. 90% 42 days after fracture) but this difference was not statistically significant (P > 0.05).

CONCLUSION

Parecoxib does not have a significant long-term effect on bone healing in rats, when it is administered in a high dose and for a short period after bone fracture.

Pathological fracture after migration of cement used to treat distal femur physeal arrest

Treatment of physeal arrest with bar removal and placement of interposition materials in young patients has been shown to restore physeal growth. Among the various materials that have been used to prevent early reformation of the physeal bar (fat, silastic, cartilage), Peterson recommended the use of Cranioplast, as this material can prevent bar reformation, and it is radiolucent because it does not contain barium. Peterson suggested steps be taken to prevent migration of the Cranioplast, as migration of the interposition material might allow for reformation of the physeal bar. Although Peterson had not observed cement migration leading to pathologic fracture, he felt that this was a potential concern. We describe the case of cement migration from the epiphysis into the diaphysis, leading to a pathological femur fracture. Despite migration of the Cranioplast, the physeal bridge did not reform, and the patient had nearly normal growth 7 years after the initial physeal arrest procedure.

Local delivery of indomethacin by a polyorthoester inhibits reossification of experimental bone defects

Inhibition of orthotopic reossification after surgical removal of bone is sometimes indicated and may be accomplished by implantation of interpositional materials or by systemic administration of indomethacin. However, implantation of nonresorbable foreign material may induce a chronic inflammation and predispose to infections; and systemic administration of indomethacin may induce systemic adverse effects. We studied the effect of local delivery of indomethacin by a bioerodible polyorthoester on the reossification of segmental defects of the radius in rats. We divided 45 Wistar rats into three groups, A-C. A 3.5 mm-long middiaphyseal osteoperiosteal resection of the right radius was made in each rat. The defect was filled with 15 mg of polyorthoester with 5% indomethacin in group A and 15 mg of polyorthoester without drug in group B. No material was implanted in the defects in the group C rats. The rats were killed 50 days postoperatively. The mean area of the residual defects were greater in the defects with the polyorthoester with 5% indomethacin compared with defects with polyorthoester without drug or without implant as judged by computer-assisted area measurements on radiographs. By light microscopy, no inflammation was seen and only traces of the polyorthoester could be detected in the defects filled with the polyorthoester with or without indomethacin. The results of this study suggest that the polyorthoester may be used as a bioerodible system for local delivery of indomethacin to inhibit reossification of skeletal defects without tissue reaction, unabsorbed carrier, or systemic effects.

Influence of indomethacin on the regeneration of cortical bone within titanium implants in rabbits

The influence of indomethacin on cortical bone regeneration was studied in bone harvest chambers made of commercially pure titanium and inserted in rabbit tibia. Newly formed bone was harvested in situ every 3 wk for 33 wk. Indomethacin (1 mg/kg body weight) was given daily as subcutaneous injections for two periods, followed by two control periods with no drug administration and the same schedule was followed for indomethacin at a dose of 4 mg/kg body weight. These indomethacin dosages did not statistically influence the cortical bone regeneration.

[99mTc]diphosphonate uptake and hemodynamics in experimental arthritis: effect of naproxen in the canine carrageenan injection model

The impact of naproxen treatment on juxta-articular hemodynamics and bone metabolism in experimental juvenile arthritis was studied in the articular carrageenan injection model. Unilateral gonarthritis was induced for 12 weeks in eight dogs receiving naproxen (dosage, 2 mg/kg) and eight controls. Regional blood flow was assessed by the microsphere method, plasma volume by the distribution space of [125I]fibrinogen, and bone metabolism by the 2-h uptake of [99mTc]diphosphonate ([99mTc]DPD). Synovial effusion was less prominent with naproxen treatment as judged by joint fluid volume and pressure. Naproxen reduced the arthritic capsular hyperemia, almost normalized a severe blood flow increase in patella and both juxta-articular epiphyses, ameliorated an expansion of plasma volume in the patella and the distal femoral epiphysis, and normalized an increased [99mTc]DPD uptake in subchondral femoral bone and the tibial cortex. Significantly increased arteriovenous shunting in the arthritic extremity was unaffected by naproxen. The study suggests that long-term cyclooxygenase inhibition offers protection against hemodynamic and metabolic changes in juxta-articular bone secondary to synovial inflammation.

Fracture healing in rats inhibited by locally administered indomethacin

We studied the inhibitory effect of indomethacin on fracture healing in 135 young, male rats after oral administration compared with local application into the fracture. A closed mid-diaphyseal fracture of the left femur was performed in all the rats. The fractures were not immobilized. In one experiment, half of the animals received indomethacin via a stomach tube (2 mg/kg/day) for 10 days; the controls received only the vehicle. In another experiment, 0.5 mg of indomethacin, contained in a bioerodible polyorthoester gel, was injected into the fracture area in half the rats; in the controls, only the gel was injected. In both experiments, random animals were killed on Days 0, 5, 10, and 20. As assessed by radiographs and manual testing, the same inhibition of fracture healing was found regardless of whether indomethacin was given orally or locally. However, the amount of indomethacin that was applied locally was only one fourth of the total dose given orally; no indomethacin was detected in the serum.

Uncertain effect of indomethacin on physeal growth injury. Experiments in rabbits

Growth arrest and shortening remain significant sequelae of growth-plate injuries. Nonsteroidal anti-inflammatory agents, known to inhibit callus and bone formation, may be useful to diminish callus-induced growth effects after epiphyseal fracture. In this study, we created a longitudinal osteotomy of the medial distal femoral condyle in 54 rabbits to model a Type IV epiphyseal fracture. We treated half with indomethacin and half with normal saline for 6 weeks. Nineteen animals of each group developed deformity, with indomethacin-treated animals averaging only slightly less angulation than the controls. However, the mean femoral shortening was less in the indomethacin-treated animals as compared with the controls.

Effects of acetylsalicylic acid and naproxen on the mechanical properties of intact femora in rats

The influence of acetylsalicylic acid (ASA) and naproxen on growing bones was studied. Young male rats were used. The drugs were administered via gastric gavage twice a day for 9 or 18 days. Drug doses giving serum concentrations corresponding to ordinary anti-inflammatory steady-state levels in humans were used. There was a drug-related influence on the strength of the growing femur. After 9 days the ultimate bending moment of the distal femoral epiphyseal plate and ultimate torsional moment and stress of the femoral diaphysis increased by about 10% in the rats treated with 150 mg/kg/12 h of ASA as compared with controls. After 18 days there were no differences. The ultimate metaphyseal bending moment of the distal femur was not influenced after 9 days with this dose, but was reduced by about 10% compared with controls after 18 days. Doses of 100 mg/kg/12 h of ASA and 20 mg/kg/12 h of naproxen did not change the bone strength. The doses used were well tolerated and did not influence the bone growth or body weight of the rats. A naproxen dose of 40 mg/kg/12 h was lethal; rats that received this dose succumbed to jejunal perforations. The results indicate that ASA influences the remodeling of normally growing bones.