Calcium hydroxide ameliorates tobramycin toxicity in cultured chick tibiae

Nanostructured platforms for the sustained and local delivery of antibiotics in the treatment of osteomyelitis

This article provides a critical view of the current state of the development of nanoparticulate and other solid-state carriers for the local delivery of antibiotics in the treatment of osteomyelitis. Mentioned are the downsides of traditional means for treating bone infection, which involve systemic administration of antibiotics and surgical debridement, along with the rather imperfect local delivery options currently available in the clinic. Envisaged are more sophisticated carriers for the local and sustained delivery of antimicrobials, including bioresorbable polymeric, collagenous, liquid crystalline, and bioglass- and nanotube-based carriers, as well as those composed of calcium phosphate, the mineral component of bone and teeth. A special emphasis is placed on composite multifunctional antibiotic carriers of a nanoparticulate nature and on their ability to induce osteogenesis of hard tissues demineralized due to disease. An ideal carrier of this type would prevent the long-term, repetitive, and systemic administration of antibiotics and either minimize or completely eliminate the need for surgical debridement of necrotic tissue. Potential problems faced by even hypothetically "perfect" antibiotic delivery vehicles are mentioned too, including (i) intracellular bacterial colonies involved in recurrent, chronic osteomyelitis; (ii) the need for mechanical and release properties to be adjusted to the area of surgical placement; (iii) different environments in which in vitro and in vivo testings are carried out; (iv) unpredictable synergies between drug delivery system components; and (v) experimental sensitivity issues entailing the increasing subtlety of the design of nanoplatforms for the controlled delivery of therapeutics.

A review of bone substitutes

The use of bone grafts in the repair of defects has a long history of success, primarily with the use of autologous bone. With increasing technologic advances, researchers have been able to broaden the spectrum of grafting materials to allografts, xenografts, and synthetic materials, which provide the surgeon and patient with options, each with unique advantages. It is with the knowledge of each material that the clinician can present and suggest the best material and tailor treatment plans to fit each individual. In this article, we present an overview of the principles of bone grafting, the types of graft materials available, and an outlook to what the future holds in this area of medicine and dentistry.

Histomorphometric evaluation of bone regeneration using allogeneic and alloplastic bone substitutes

PURPOSE

The purpose of this investigation was to assess bone regeneration in critical sized defects in the rabbit calvarium using allogeneic and alloplastic bone substitutes.

MATERIALS AND METHODS

Thirty New Zealand White rabbits were divided into 3 groups of 10 animals each. Bilateral 15 mm x 17 mm calvarial defects were made in the parietal bones of each animal. Group 1 had demineralized bone matrix (DBM) gel placed in one defect, while the other defect was left unfilled and served as the control. Group 2 had one defect filled with calcium hydroxide (CaOH)-treated DBM gel and the other defect filled with DBM gel. Group 3, the calcium-phosphate cement group, had Norian CRS (Norian Corp, Cupertino, CA) placed on one side and Bone Source (Howmedica Leibinger, Dallas, TX) placed on the contralateral side. Five animals in each group were killed at 6 and 12 weeks. Data analysis included qualitative assessment of the calvarial specimens and radiographic evaluation. Histomorphometric analysis was used to quantify the amount of new bone within the defects.

RESULTS

Histomorphometric analysis showed that DBM gel-treated defects had significantly more new bone at 12 weeks compared with all other groups. There was no significant difference between defects filled with CaOH-treated DBM gel and those filled with DBM gel at 12 weeks. In group 3, Norian CRS- and Bone Source-treated defects were not statistically different from the unfilled controls.

CONCLUSION

DBM gel was an effective allogeneic bone substitute that showed reliable osseous healing of critical size defects in the rabbit calvarium. The addition of CaOH to DBM gel did not significantly improve the bone regenerative capacity of the DBM gel. Both Norian CRS and Bone Source did not promote bone regeneration in this animal model.

Use of antibiotic-impregnated cement in total joint arthroplasty

The use of antibiotic-impregnated cement in revision of total hip arthroplasty procedures is widespread, and a substantial body of evidence demonstrates its efficacy in infection prevention and treatment. However, it is not clear that it is necessary or desirable as a routine means of prophylaxis in primary total joint arthroplasty. In the management of infected implant sites, antibiotic-impregnated cement used in one-stage exchange arthroplasties has lowered reinfection rates. In two-stage procedures, use of beads and either articulating or nonarticulating antibiotic-impregnated cement spacers also has lowered reinfection rates. In addition, spacers reduce "dead space," help stabilize the limb, and facilitate reimplantation. Problems associated with antibiotic-impregnated cement in total joint arthroplasty include weakening of the cement and the generation of antibiotic-resistant bacteria in infected implant sites.

Effects of calcium hydroxide and transforming [correction of tumor] growth factor-beta on collagen synthesis in subcultures I and V of osteoblasts

Collagen protein synthesis by osteoblasts is influenced by transforming growth factor-beta (TGF-beta 1) and is essential to bone formation. The effectiveness of TGF-beta 1 depends on efficient delivery of the growth factor to target cells, adequate binding to cell surface receptors, and an optimum environment for promotion of collagen synthesis. The effects of calcium hydroxide (Ca(OH)2), TGF-beta 1, and Ca(OH)2/TGF-beta 1 co-administration on total protein, collagen protein, and noncollagen protein synthesis by early (subculture I) and late (subculture V) osteoblast cultures were tested. TGF-beta 1 significantly increased all protein synthesis in subculture I osteoblasts (p = 0.001; p < 0.001; p = 0.019). Ca(OH)2/TGF-beta 1 co-administration significantly increased total protein and collagen protein levels in subculture I osteoblasts as well (p = 0.048; p = 0.012). TGF-beta 1 increased total protein and collagen protein synthesis significantly in subculture V cells (p = 0.025; p = 0.01). These data indicate that co-administration of Ca(OH)2 and TGF-beta 1 enhances collagen synthesis by osteoblasts and may have implications for the clinical setting.

TGF-beta 1 alone and in combination with calcium hydroxide is synergistic to TGF-beta 1 production by osteoblasts in vitro

AIM

To examine the effects of calcium hydroxide (Ca(OH)2), transforming growth factor-beta (TGF-beta 1), and Ca(OH)2/TGF-beta 1 coadministration on TGF-beta 1 and interleukin-6 (IL-6) synthesis by early (subculture 1) and late (subculture 5) osteoblast cultures.

METHODOLOGY

Early and late cultures were established using bone cells harvested from 21-day-old fetal rat calvaria. Cell cultures of both early and late osteoblasts were divided into four groups: group 1, control; group 2, cells challenged with Ca(OH)2; group 3, cells challenged with TGF-beta 1; and group 4, cells challenged with Ca(OH)2 and TGF-beta 1 in combination. TGF-beta 1 and IL-6 levels for all groups were determined using ELISA methodology.

RESULTS

ANOVA and Tukey HS analyses revealed that osteoblasts of groups 3 and 4 significantly increased (P < 0.001) TGF-beta 1 synthesis in both early and late cultures of osteoblasts. IL-6 was not detected in any of the groups considered in this study.

CONCLUSIONS

Exogenous TGF-beta 1 has an autocrine effect on cell cultures of osteoblasts. Administration of TGF-beta 1 alone or in combination with Ca(OH)2 increases the synthesis of TGF-beta 1 in osteoblast cultures. Ca(OH)2 and TGF-beta 1 are compatible when placed in a culture of osteoblasts. Ca(OH)2 provides a favourable environment for the anabolic effects of TGF-beta 1.

Effects of very high antibiotic concentrations on human intervertebral disc cell proliferation, viability, and metabolism in vitro

STUDY DESIGN

Four antibiotics commonly used during spinal surgery (cefazolin, gentamycin, cefamandole, and vancomycin) were tested for their effects on cultured human disc cells from the anulus.

OBJECTIVE

To determine the viability, proliferation, and metabolism of cells cultured from the human anulus after they were exposed to four antibiotics.

SUMMARY OF BACKGROUND DATA

Previous studies concerning the effect of antibiotics on the disc have used animal models or explanted discs, but little is understood about the effect of antibiotics on the proliferation, viability, and metabolism of cells from the anulus.

METHODS

In this study, 3H-thymidine incorporation, trypan blue exclusion, and cell metabolism were determined using cells from the human anulus grown in monolayer culture. The latter measurement used a cytosensor microphysiometer to monitor the rate at which cells acidified their microenvironment, an event that is proportional to cellular metabolism because it reflects the excretion over time of acidic products such as lactic acid from glycolysis and CO2 from cellular respiration.

RESULTS

After 48 hours of antibiotic exposure, cell viability was significantly lower as a result of all four antibiotics at the highest concentration tested. Cell proliferation was lower after exposure to cefazolin and cefamandole. During a 6-hour antibiotic exposure, anulus cells in the highest concentration of cefamandole or vancomycin displayed a significantly decreased rate of cell metabolism.

CONCLUSIONS

These findings show that high doses of antibiotics can have direct, deleterious effects on cultured disc cell survival, cell proliferation, and metabolic rates. Discitis is a serious primary or postoperative complication that often requires prolonged antibiotic treatment. Studies such as the current investigation with cultured cells from the anulus show the importance of a greater understanding concerning antibiotic effects on disc cell proliferation and metabolism.

Antibiotic beads in the treatment of diabetic pedal osteomyelitis

Antibiotic-impregnated polymethylmethacrylate (PMMA) beads have improved the outcome of osteomyelitis treatment in both experimental models and clinical trials. The primary benefit of antibiotic-impregnated PMMA beads is that they provide high local concentrations of antibiotic while systemic levels of antibiotic remain low. Little has been written about the specific use of antibiotic-impregnated PMMA beads in the treatment of diabetic pedal osteomyelitis. The authors review antibiotic-impregnated PMMA beads and provide examples of their use in the treatment of diabetic pedal osteomyelitis.