Assessment in rats of a new bioerodible bone-wax-like polymer

Efficacy and safety of a novel hemostatic material, BoneStat, compared with Ostene and Bone Wax in a rat calvarial defect model

Hemostasis has critical significance during surgical procedures. Bone Wax has traditionally been commonly used for bone hemostasis despite well-documented undesirable side effects: hindering osteogenesis and induction of inflammatory reactions with consequent increase in infection rates. A later developed formulation, Ostene, offers an alternative to Bone Wax with lesser undesired effects. In this study, BoneStat, a newly developed bone hemostatic formulation comprising water-soluble alkylene oxide co-polymers, was evaluated for water solubility, hemostatic efficacy, ease of handling, bone healing efficacy, and inflammatory reactions compared with Bone Wax and Ostene in a rat calvarial defect model. More than 95% of BoneStat was dissolved in water within 48 h, as was Ostene, but not Bone Wax. The time to hemostasis using BoneStat was significantly faster than with Ostene or Bone Wax. BoneStat also improved ease of handling compared to Ostene or BoneWax. BoneStat- and Ostene-treated groups constantly showed better bone healing than with Bone Wax. The BoneStat and Ostene groups presented no evidence of chronic inflammation reaction contrary to Bone Wax. These results suggest improved hemostasis, ease of handling, non-hindering bone healing, and unnoticeable chronic inflammatory reactions with BoneStat. Thus, Bonestat is a useful and reliable formulation for mechanical hemostasis.

Ostene, a new alkylene oxide copolymer bone hemostatic material, does not inhibit bone healing

OBJECTIVE

In this study, we investigate the effects of a soft bone hemostatic wax comprised of water-soluble alkylene oxide copolymers (Ostene; Ceremed, Inc., Los Angeles, CA) on bone healing in a rat calvaria defect model. We compared the effects with a control (no hemostatic agent) and bone wax, an insoluble and nonresorbable material commonly used for bone hemostasis.

METHODS

Two bilateral 3-mm circular noncritical-sized defects were made in the calvariae of 30 rats. Alkylene oxide copolymer or bone wax was applied or no hemostatic material was used (control). After 3, 6, and 12 weeks, rats were sacrificed and the calvariae excised. Bone healing, expressed as fractional bone volume (+/- standard error of the mean), was measured by microcomputed tomography.

RESULTS

Immediate hemostasis was achieved equally with bone wax and alkylene oxide copolymer. Bone wax-filled defects remained unchanged at all time points with negligible healing observed. At 3 weeks, no evidence of alkylene oxide copolymer was observed at the application site, with fractional bone volume significantly greater than bone wax-treated defects (0.20 +/- 0.03 versus 0.02 +/- 0.01; P = 0.0003). At 6 and 12-weeks, alkylene oxide copolymer-treated defects continued to show significantly greater healing versus bone wax (0.18 +/- 0.04 versus 0.05 +/- 0.01 and 0.31 +/- 0.04 versus 0.06 +/- 0.02, respectively). At all time points, alkylene oxide copolymer-treated and control defects showed good healing with no significant difference.

CONCLUSION

Alkylene oxide copolymer is an effective hemostatic agent that does not inhibit osteogenesis or bone healing.

Infection rates and healing using bone wax and a soluble polymer material

The effects of using a newly available water-soluble polymer bone hemostatic material in a contaminated environment were assessed in a rabbit tibial defect model. Infection rates and healing of polymer-treated bone were compared with the infection and healing of bone wax-treated bone and untreated controls after a bacterial challenge. Defects created in 24 rabbit tibias were treated with the polymer or bone wax, or left without a hemostatic agent. The defects were inoculated with Staphylococcus aureus ATCC-29213 (2.5 x 10(4) colony-forming units). After 4 weeks, all defects treated with bone wax were infected and osteomyelitis had developed, and none had evidence of bone healing. In the polymer and control groups, two defects in each group (25%) had osteomyelitis develop. The remaining six defects in each group (75%) showed no osteomyelitis and exhibited normal bone healing. The polymer-treated defects had a considerably lower rate of osteomyelitis and positive bone cultures compared with the bone wax-treated group. There were no differences between the polymer-treated and control groups in the rates of osteomyelitis, positive cultures, or bone healing. The use of a soluble polymer as an alternative to bone wax may decrease the rates of postoperative bone infections.

A histological and immunohistochemical study of tissue reactions to solid poly(ortho ester) in rabbits

In many cases only the temporary presence of a biomaterial is needed in tissue support, augmentation or replacement. In such cases biodegradable materials are better alternatives than biostable ones. At present, biodegradable polymers are widely used in the field of maxillofacial surgery as sutures, fracture fixation devices and as absorbable membranes. The most often used polymers are aliphatic polyesters, such as polyglycolic acid (PGA) and polylactic acid (PLA). Poly(ortho ester) is a surface eroding polymer, which has been under development since 1970, but is used mostly in drug delivery systems in semisolid form. The aim of this study was to evaluate the tissue reactions of solid poly(ortho ester) (POE), histologically and immunohistochemically. Resorption times and the effect of 2 different sterilization methods (gamma radiation and ethylene oxide) upon resorption were also evaluated. Material was implanted into the tibia and subcutaneously into the mandibular ramus area of 24 rabbits. Follow-up times were 1-10, 14 and 24 weeks. Histological studies showed that POE induces a moderate inflammation in soft tissue and in bone. At 24 week follow-up, inflammation was mild in soft tissue and moderate in bone. In immunohistochemical studies, no highly fluorescent layer of tenascin or fibronectin was found adjacent to the implant. Resorption of gamma-sterilized rods was faster than ethylene oxide-sterilized rods. The total resorption time was more than 24 weeks in both groups. Clinically the healing was uneventful and the implants the well tolerated by the living tissue. This encourages these authors to continue studies with this interesting new material to search for the ideal material for bone filling and fracture fixation.

Ostene, a New Water-Soluble Bone Hemostasis Agent

Traditional formulations of bone wax are composed largely of beeswax and are well known to interfere with bone healing and cause inflammatory reactions. Ostene, a newly available bone hemostasis agent made of water-soluble alkylene oxide copolymers, was evaluated. The soft tissue response to Ostene was compared with bone wax and a polyethylene control after implantation into the paravertebral muscles of three rabbits. After 2 weeks, Ostene elicited no fibrous response, the polyethylene elicited a thin (less than 0.5 mm) fibrous response, and the bone wax was encased in a fibrous capsule 0.6 to 1.0 mm thick infiltrated with inflammatory cells. The effects of Ostene were compared with bone wax in a femur defect model in eight rabbits. Ostene showed no evidence of an adverse response in the cortical defect site, medullary cavity, or the surrounding tissue at 4 and 8 weeks. In contrast, bone wax at both time intervals elicited a foreign body response consisting of fibrous tissue infiltrated by macrophages, giant cells, and lymphocytes at the sites of the bone defects. Bone wax also displaced the bone marrow and interfered with bone ingrowth into the defects. Ostene provides the clinician a water-soluble bone hemostasis material that does not demonstrate the adverse tissue response or the interference with bone healing seen with the use of bone wax.

Histologically verified bone wax (beeswax) granuloma after median sternotomy in 17 of 18 autopsy cases

AIM

To evaluate the sternum from ordinary or forensic autopsy cases with a midline sternal cutaneous scar macro- and microscopically and using computed tomography (CT) to detect if the haemostatic bone sealant bone wax (beeswax) had been applied after median sternotomy and if the bone wax had elicited inflammation.

METHODS

During a 3-year period, the sterna of 18 consecutive cadavers (15 ordinary autopsies, 3 forensic) who prior to death had undergone surgery with median sternotomy were examined macro- and microscopically and with CT. In addition, one virgin sternum was smeared with bone wax at the upper half after bench sternotomy, sutured and examined with CT. Unused bone wax was examined with CT for attenuation measurements.

RESULTS

Macroscopically, bone wax was seen in 17 of 18 sterna. Acute inflammation was found in one, chronic inflammation and foreign body multinucleated giant cells were seen around the bone wax in 17 sterna. No inflammation was found in one. CT could only detect foci in the operated sterna with attenuation values from -45 to +20 Hounsfield units (HU) and values about -80 HU were found in the virgin sternum. Unused bone wax measured about -100 HU.

CONCLUSIONS

Bone wax is non-resorbable and induces chronic inflammation in the operated sternum up to 10 years after application. Measurement of Hounsfield units with CT of the operated sterna could not verify bone wax granuloma.

Efficacy and safety of a novel moldable, resorbable, and degradable sealant of bone surfaces for hemostasis after bone graft harvesting from the iliac crest

STUDY DESIGN

A prospective, controlled, open, randomized multicenter study.

OBJECTIVE

The study's objective was to demonstrate equivalence of a novel, moldable, resorbable, and degradable synthetic polymer (Bone Seal) compared with a collagen fleece (Lyostypt) in efficacy and safety for topical hemostasis after iliac crest bone graft harvesting.

SUMMARY OF BACKGROUND DATA

Harvesting cortico-cancellous bone from the iliac crest is a well established procedure in orthopedic and particularly in spine surgery. It is associated with significant morbidity at the donor site where hematoma formation may cause impaired wound healing and infections in up to 10% of cases.

METHODS

A total of 112 patients were included in the safety analysis. Safety was determined by a compound wound healing score and the incidence of adverse clinical effects. One hundred and eight patients were studied for equivalence in efficacy using a compound bleeding score. The handling properties and the application to the bone surface of either device were measured with two additional compound scores.

RESULTS

The mean bleeding scores in the final analysis was 4.5 +/- 1.3 for the Bone Seal group and 4.2 +/- 1.3 for the collagen fleece group. Bone Seal was better applicable to the bleeding bone surfaces than the collagen fleece, even though its handling was more complicated. Wound healing and the incidences of adverse clinical events were comparable in either study group.

CONCLUSIONS

Bone Seal is an effective and safe hemostatic material for sealing bleeding bone surfaces after iliac crest bone graft harvesting. By virtue of its hemostatic efficacy, Bone Seal is preventive for wound healing disorders.

Poly(ortho esters): synthesis, characterization, properties and uses

Over the last 30 years, poly(ortho esters) have evolved through four families, designated as POE I, POE II, POE III and POE IV. Of these, only POE IV has been shown to have all the necessary attributes to allow commercialization, and such efforts are currently underway. Dominant among these attributes is synthesis versatility that allows the facile and reproducible production of polymers having the desired mechanical and thermal properties as well as desired erosion rates and drug release rates that can be varied from a few days to many months. Further, the polymer is stable at room temperature when stored under anhydrous conditions and undergoes an erosion process confined predominantly to the surface layers. Important consequences of surface erosion are controlled and concomitant drug release as well as the maintenance of an essentially neutral pH in the interior of the matrix because acidic hydrolysis products diffuse away from the device. Two physical forms of such polymers are under development. One form, solid materials, can be fabricated into shapes such as wafers, strands, or microspheres. The other form are injectable semi-solid materials that allow drug incorporation by a simple mixing at room temperature and without the use of solvents. GMP toxicology studies on one family of POE IV polymers has been concluded, an IND filed and Phase I clinical trials are in progress. Important applications under development are treatment of post-surgical pain, osteoarthritis and ophthalmic diseases as well as the delivery of proteins, including DNA. Block copolymers of poly(ortho ester) and poly(ethylene glycol) have been prepared and their use as a matrix for drug delivery and as micelles, primarily for tumor targeting, are being explored.

Therapeutic applications of viscous and injectable poly(ortho esters)

Poly(ortho esters) (POE) are hydrophobic and bioerodible polymers that have been investigated for pharmaceutical use since the early 1970s. Among the four described generations of POE, the third (POE III) and fourth (POE IV) are promising viscous and injectable materials which have been investigated in numerous biomedical applications. POE III has been extensively studied for ophthalmic drug delivery, it presents an excellent biocompatibility and is currently being investigated as a vehicle for sustained drug delivery to treat diseases of the posterior segment of the eye. POE IV is distinguishable by a highly reproducible and controlled synthesis, a higher hydrophobicity, and an excellent biocompatibility. It is currently under development for a variety of applications, such as ocular delivery, periodontal disease treatment and applications in veterinary medicine. This review will also focus on new perspectives for this promising family of polymers, such as guided tissue regeneration, treatment of osteoarthritis, as well as peptide and protein delivery.

A new, pluronic-based, bone hemostatic agent that does not impair osteogenesis

OBJECTIVE

Intraoperative bone hemostasis can be accomplished using surgical beeswax (bone wax). However, bone wax locally interferes with osteogenesis, and its use is avoided when bone fusion is critical. We describe the use of a Pluronic copolymer blend as a biocompatible, absorbable, hemostatic agent.

METHODS

A rat femur defect model and a femur gap nonunion model were used. For each surgical model, 24 rats were divided into three treatment groups, i.e., those receiving bone wax implants, Pluronic (90% Pluronic P85/10% Pluronic F88) implants, or no implants (control group). After 10, 21, or 42 days, animals were killed and femora were removed for radiographic analysis and hematoxylin and eosin staining.

RESULTS

In the femur defect model, no differences were observed between the Pluronic-treated and control groups; hematoxylin and eosin staining demonstrated bone formation and osteocytes within the defect. In the femur gap nonunion model, no fusions occurred in any group. Development of an osseous callus at the gap site was observed for the control and Pluronic-treated groups. In both models, rats that received bone wax implants exhibited no osseous growth.

CONCLUSION

The Pluronic blend exhibits handling properties similar to those of bone wax, readily achieves hemostasis, and does not inhibit bone regrowth. Pluronic compounds may serve as effective absorbable hemostatic agents for the treatment of bone bleeding in sites where fusion is critical. In addition, this copolymer blend may find use as a vehicle for the short-term release of pharmacological agents, which may further reduce the incidence of infections, reduce inflammation, and improve fusion rates.

Biocompatibility and effect on osteogenesis of poly(ortho ester) compared to poly(DL-lactic acid)

Implantation of demineralized bone induces new bone formation by the action of contained growth factors, of which bone morphogenetic proteins are of prime importance. A biodegradable polymer may be used as a carrier for demineralized bone particles or recombinant bone growth factors to prevent displacement of the implant, preserve its volume and shape, and assure sustained release of the incorporated active components. A polymer for this use should be biocompatible and completely absorbed without interfering with the osteogenesis. We investigated the host-tissue response and effect on demineralized bone-induced bone formation by two biodegradable polymers, a poly(ortho ester) and an amorphous low-molecular poly(DL-lactic acid). Both polymers had a plastic consistency, could easily be molded, and adhered well to the demineralized bone particles. Demineralized bone particles were implanted alone and in combination with each of the polymers in the abdominal muscles of 45 male Wistar rats. Four weeks after the operation the implants were recovered and subjected to (85)Sr uptake analysis to quantify bone formation and histologic examination. The poly(ortho ester) provoked little inflammation; it was largely absorbed by 4 weeks, and no qualitative or quantitative effect on bone formation was found. The poly(DL-lactic acid) provoked a chronic inflammation with multinuclear giant cells, macrophages with engulfed material, and proliferating fibroblasts; part of the material was still present, and the bone formation was inhibited.

Polyethylene glycol/microfibrillar collagen composite as a new resorbable hemostatic bone wax

Although bone wax is effective at achieving hemostasis, it is nonresorbable, causes a foreign body reaction, and inhibits osteogenesis. We report development of a polyethylene glycol/microfibrillar collagen composite (PEG/MFC) that has inherent hemostatic qualities, is biodegradable, and is compatible with bone repair. PEG/MFC composite (n = 42) was placed in 5 mm cranial defects in New Zealand white rabbits. Hemostasis and healing were compared to unfilled defects (n = 32) and defects filled with standard bone wax (n = 10). Both PEG/MFC and bone wax handled well and stopped bleeding. The polyethylene glycol component was resorbed by 8 h, and the microfibrillar collagen was resorbed over 2 months, eliciting only a minor inflammatory response during the first month. Defects filled with the PEG/MFC composite showed similar amounts of bony regeneration as did unfilled control defects. At 4 weeks, healing bone accounted for 43 +/- 13% in those treated with PEG/MFC and 47 +/- 19% defect area in untreated holes. In contrast, less than 1% of the area was bone in defects filled with bone wax (p < 0.05). PEG/MFC composite provided excellent bony hemostasis and did not inhibit bone growth.

Haemostasis in periradicular surgery

The successful performance of endodontic surgical procedures is predicated on many factors. However, the ability of achieve sustained tissue haemostasis in the surgical site is crucial to the performance of these procedures. This achievement improves vision in the surgical site, minimizes surgical time, enhances the surgical procedures (root-end resection, preparation and filling), and reduces surgical blood loss, postsurgical haemorrhage and postsurgical swelling. A multitude of materials have used in dentistry and medicine to achieve both generalized and localized haemostasis, many without full assessment of their biological implications. The purpose of this paper is to provide a thorough and critical review of these materials from the perspective of surgical endodontics, highlighting their development, application and potential role in achieving proper haemostasis.

Surgical bone wax causing epistaxis

A case of recurrent epistaxis caused by bone wax in the nasal cavity is reported. This is the first reported case of a nasal complication due to surgical bone wax.

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.