Ciprofloxacin inhibition of experimental fracture healing.

BACKGROUND: Fluoroquinolones, such as ciprofloxacin, have an adverse effect on growing cartilage and endochondral ossification in children. This study was carried out to determine whether ciprofloxacin also has an adverse effect on the healing of experimental fractures. METHODS: Sixty male 300-gram Wistar rats were divided equally into three groups, which received ciprofloxacin, cefazolin, or no treatment for three weeks, beginning seven days after production of a closed, nondisplaced, bilateral femoral fracture. The serum concentrations of the ciprofloxacin and the cefazolin were 2.4 and 146 micrograms per milliliter, respectively. Radiographic, histological, and biomechanical studies were used to evaluate fracture-healing. RESULTS: Radiographs revealed significantly more advanced healing of the control fractures compared with the fractures in the ciprofloxacin-treated group (average stage, 2.1 compared with 1.5, p = 0.01). The cefazolin-treated group was not different from the controls with respect to radiographic healing (average stage, 1.8 compared with 2.1, p = 0.18). Torsional strength-testing of fracture callus exposed to ciprofloxacin revealed a 16 percent decrease in strength compared with the controls (284 compared with 338 newton-millimeters, p = 0.04) and a 49 percent decrease in stiffness (twenty compared with thirty-nine newton-millimeters per degree, p = 0.001). The biomechanical strength in the cefazolin-treated group was not different from that of the controls. Fracture calluses in the animals treated with ciprofloxacin showed abnormalities in cartilage morphology and endochondral bone formation and a significant decrease in the number of chondrocytes compared with the controls (0.77 x 10(4) compared with 1.3 x 10(4) cells per square millimeter, p = 0.004). CONCLUSIONS: These data suggest that experimental fractures exposed to therapeutic concentrations of ciprofloxacin in serum demonstrate diminished healing during the early stages of fracture repair. The administration of ciprofloxacin during early fracture repair may compromise the clinical course of fracture-healing.

Oligoclonal T-cell proliferation and interferon-gamma production in periprosthetic inflammation.

Total joint arthroplasty has dramatically changed the treatment options for patients with destructive joint disease. The materials used to manufacture implants are regarded as biologically inert; accordingly, arthroplasty is a very successful intervention for most patients. However, a subset of patients develops an inflammatory reaction around the prosthesis, causing implant loosening and irreversible bone destruction. To identify mechanisms leading to periprosthetic inflammation, the function and composition of macrophages and T cells accumulated in the pseudosynovia were examined. Tissue-infiltrating macrophages synthesized a spectrum of proinflammatory cytokines including IL-1beta, IL-6, and TGF-beta. T cells recruited to the periprosthetic inflammatory lesions were characterized by restricted diversity of T-cell receptors and the emergence of dominant clonal populations. T cells with identical T-cell receptor sequences, and thus with identical antigen specificity, were isolated from anatomically distinct and independent regions of the tissue. Transcription of IL-2, IFN-gamma, and, in some patients, IL-4 genes in the periprosthetic membrane indicated functional activation of infiltrating T cells. Correlation of periprosthetic osteolysis with the tissue cytokine pattern demonstrated a relationship between IFN-gamma transcription and bone loss. We propose that antigen-recognition events are critically involved in the development of periprosthetic inflammation and that the functional commitment of T cells recruited to the periprosthetic region influences whether periprosthetic inflammation is complicated by bone destruction.

An effective method of completely removing contaminating genomic DNA from an RNA sample to be used for PCR.

A simple method for removing contaminating genomic DNA from an RNA preparation is presented. The method involves digestion of the RNA with RNase-free DNase I at room temperature followed by inactivation of the enzyme at 65 degrees C in presence of EDTA. This method produces an RNA sample that is negative for genomic DNA by PCR.

The use of demineralized bone matrix in the repair of segmental defects. Augmentation with extracted matrix proteins and a comparison with autologous grafts.

A soluble protein component of bone, bone morphogenetic protein, and decalcified bone matrix have been shown to induce the formation of bone in extraosseous tissue. Clinical and animal studies investigating the use of these materials as bone grafts have shown radiographic and histological evidence of formation of bone, but the clinical usefulness of these grafts remains unknown. This study compared the healing processes when plasma-coated demineralized bone matrix and autologous cancellous bone were used to graft segmental defects of bone. A standard procedure was used to make a two-centimeter defect bilaterally in the ulna of forty-eight skeletally mature New Zealand White rabbits. In each rabbit, one ulnar defect was grafted with autologous citrated plasma-coated demineralized bone matrix while the other defect served as a control and was grafted with either autologous cancellous bone from the iliac crest, demineralized bone matrix, or demineralized bone matrix augmented with bone proteins that had been extracted with guanidinium hydrochloride. The ulnar defect was stabilized by the intact radius, and no supplemental device was necessary for fixation. To examine spontaneous healing in this model, one group of rabbits had a control defect that was not grafted. The grafts were periodically evaluated by radiographs, and twelve weeks after surgery the grafts were harvested and tested to failure in a standard torsion-test machine. The mechanical parameters were calculated, and histological examination of major fragments of the grafts was performed. The results of the radiographic and histological evaluation showed that all of the grafted ulnae healed, with fusion of the graft to the cut ends of the defect and reformation of approximately normal anatomy. No ungrafted ulnar defects healed. The results from the mechanical tests were evaluated by comparing the defect that was grafted with plasma-coated demineralized bone matrix with the control graft in each animal. These data showed that: twelve weeks after grafting, the normal ulnae were significantly stronger than the ulnae that had been grafted with plasma-coated demineralized bone matrix; the ulnae that had been grafted with plasma-coated demineralized bone matrix and those that had been grafted with autologous bone were equivalent in strength; and twelve weeks after grafting, grafts of demineralized bone matrix that were augmented with extracted bone proteins were significantly stronger than those that had not been so augmented.