Incorporation Of Bone Allografts Research Articles

STUDY OF BIOCHEMICAL MARKERS OF OSTEOGENESIS IN CASE OF BONE ALLOGRAFTS INCORPORATION IN RATS WITH FOLLOWED AFTER SURGERY ADMINISTRATION OF CISPLATIN AT THE DIFFERENT METHODS OF IMPLANT STERILIZATION

Bone allografts are commonly used for surgical treatment of cancer patients. However, such complications as violation of allograft fusion, its lysis and fractures, infection lead to additional research in this field of medicine. Objective. To study changes in biochemical osteogenesis markers under the action of cytostatics on the process of incorporation of bone allografts. Methods. The work was performed on 20 male white rats (age at the beginning of the experiment 5–6 months). All animals have a perforated defect in the distal metaphysis of the femur filled with bone allograft (diameter 2 mm, height 3 mm), γ-radiation sterilized (Control-1 and Experiment-1) or saturation of the antibiotics sterilized (Control-2 and Experiment-2). In groups «Control» 14 days after implantation intraperitoneally injected 2.0–2.4 ml of 0.9 % sodium chloride solution, in the groups «Experiment» — cisplatin at a dose of 2.5 mg/ kgonce. 30 days after surgery, blood glycoproteins, total protein, Ca, chondroitin sulfates, acidic and alkaline phosphatase activity were evaluated. The index of mineralization (ratio of alkaline to acid phosphatases), degree is analyzed mineralization (ratio of calcium to protein). Results. In the experimental groups, compared with the control, a significant decrease in total protein and values was determined: total calcium, which indicates the suppression of processes mineralization during remodeling of bone tissue of the recipient and allograft. The highest indicators of activity acid phosphatase were recorded in groups Experiment-1 and Experiment-2, reflecting the predominance of resorption over bone formation. The degree of mineralization in the experimental groups was higher than in the control, and the mineralization index was significantly smaller. Conclusions. The detected changes in the values of biochemical markers of bone metabolism reflect the negative effect of cisplatin on osteogenesis under the conditions of allograft implantation, which leads to the lack of their fusion with the recipient bone.

Effects of gamma radiation and post-operative cisplatin injection on the incorporation of bone allografts in rats

Background. The reconstruction of long bone defects that occur after resection of tumors is a problem that requires constant study. Bone allografts are often used in this scenario. Unfortunately, while they are prepared, allografts partially lose their strength and osteoinductive properties; their survivability in oncological patients is only 40% after 10 years. This is why the search for superior allograft treatment methods and the study of allograft remodeling and incorporation in oncological patients, whose state has been affected by radiation or chemotherapy, is an area of interest. Purpose – study the structure of bone tissue in the distal metaphysis of a rat’s femur after bone allograft implantation (sterilized using gamma radiation or antibiotic saturation) and post-operative intraperitoneal cisplatin injection. Materials and Methods. Experiments were performed on 20 male white rats aged 5–6 months at the beginning of the experiment and weighed 365.8 ± 6.4g. All rats underwent a surgery that created a defect in the distal metaphysis of the femur which was filled with a bone allograft treated with gamma radiation (Control-1 and Experimental-1 groups) or saturated with an antibiotic (Control-2 and Experimental-2 groups). 14 days after allograft implantation, animals from the control groups received an intraperitoneal injection of 2.0–2.4 ml of 0.9% NaCl, while animals from the experimental groups received 2.5mg/kg of cisplatin. Histological analysis and histomorphometry were completed 30 days after the surgery. Results. 30 days after the operation, the smallest relative area of bone tissue (11.79%) was observed in rats from the Experimental-1 group, with gamma radiation treated allografts and post-operative intraperitoneal cisplatin injections. A somewhat higher value was found in the Experimental-2 group (antibiotic saturation + cisplatin) – 31.64%. In the control groups, (intraperitoneal injection 0.9% NaCl), the relative area of bone tissue was 16.7% (Control-1, gamma radiation treatment) and 58.09% (Control-2, antibiotic saturation). The relative area of fibrous tissue was the largest in the Experimental-1 group – 31.55% and the smallest in the Control-2 group – 12.79%. Conclusions. Allograft remodeling occurs along with the formation of bone and fibrous tissue when allografts are used to fill defects in the distal femoral metaphysis of rats, However, the relative percentages of those tissues depend on the allograft sterilization method and the use of cytostatic agents. The largest relative percentage of bone tissue (58.09%) was obtained using an allograft saturated with antibiotics and without the administration of cisplatin. The smallest (11.79%), on the other hand, occurred in gamma radiation treated allografts with cisplatin injected intraperitoneally after the operation

Evaluation of incorporation of bone allograft at the site of implantation in various clinical conditions along with its complications

<p class="abstract"><strong>Background:</strong> Bone transplants have been used routinely in the present century for diverse purposes to unite fractures, fuse joints, and repair skeletal defects.</p><p class="abstract"><strong>Methods:</strong> Twelve patients with fracture, bone defect, deformity, difficulty in the fusion of bone, etc. were taken in the study for elective surgery with fresh frozen allograft in the orthopedics department with the incorporation of inclusion and exclusion criteria.<strong></strong></p><p class="abstract"><strong>Results:</strong> Out of 12 cases in this study, 7 cases were related to spinal fusion, 3 cases were of fractures with bone defects, 1 case of non-union neck femur fracture and 1 case was of revision hip arthroplasty with the acetabular bone defect. Seventy-five percent (9 patients) and 25% (3 patients) were graded fair and poor respectively in the preoperative phase. At 6 months, excellent results were obtained in 50% (6 patients), good in 25% (3 patients), fair in 25% (3 patients), while none were graded as poor in terms of clinical evaluation.</p><p class="abstract"><strong>Conclusions:</strong> Fresh frozen bone, a good source of abundant bone allograft, can be stored in -70° freezer for use in orthopedic surgery to fill any filling defect in the bone. Also, proper storage, better surgical technique, hospital infection control policy, antibiotic policy, preoperative use of antibiotics before surgery has a good clinical outcome.</p>

Bone Grafting and Two-Stage Revision Total Hip Arthroplasty

Periprosthetic deep infection in combination with substantial bone loss is one of the most challenging situations in revision hip surgery. We believe the effective management of these patients requires infection control as well as bone reconstruction. A review of our previously published studies on antibiotic loaded bone allografts is presented in this paper. These investigations provided us with information on the use of bone allografts in combination with antibiotics in cases of previous infection. Our protocol is based on removal of implants, meticulous debridement, parenteral antibiotic therapy and a second-stage reconstruction with vancomycin-supplemented bone allografts to treat an infected hip arthroplasty. We observed that vancomycin does not affect bone allograft incorporation at concentrations that are 300 times higher than the minimum inhibitory concentration for Staphylococcus aureus and Staphylococcus epidermidis. We also obtained adequate pharmacokinetics using these composites, with high local levels without renal impairment. This method has the capacity of acetabular and femoral bone stock restoration, with sound fixation and without increasing the rate of reinfection.

Healing of Long-term Frozen Orthotopic Bone Allografts is not Affected by MHC Differences Between Donor and Recipient

BackgroundThe use of bone grafting in orthopaedic surgery has increased dramatically in recent years. However, the degree to which immune responses are important for the survival of the allograft is not fully understood. In particular it remains unclear whether differences in the major histocompatibility complex (MHC) influence incorporation of bone allografts and their subsequent biologic performance.Questions/purposesTherefore, we asked whether isolated mismatch for MHC antigens of deep frozen bone allografts in the long-term causes (1) immune reactions, and whether these reactions have any effect on (2) morphologic features of the graft, (3) radiographic graft healing, and (4) graft strength.MethodsWe used an established orthotopic tibial segment transplantation technique that allows determination of mechanical strength, histologic evaluation, and immune responses. Tibial segments that had been deep-frozen at −80°C for 1 year were transplanted into 24 PVG (RT1 c) rats from either 12 syngeneic donors or 12 MHC congenic donors PVG.1U (RT1 u). We determined immune responses using an indirect Coombs reaction and determined graft healing radiographically and mechanically after 6 months.ResultsWe detected no alloantibody production to graft MHC-I antigens, and found no differences between syngeneic and MHC mismatched grafts in terms of remodeling with host bone, graft healing, and mechanical strength.ConclusionsMismatches for MHC antigens do not seem to play a decisive role in healing of long-term, deep-frozen bone allografts.

Impact of freezing on immunology and incorporation of bone allograft

With an increasing clinical use of deep frozen allograft for bone reconstruction, it is important to understand the immunological and biological events of allograft incorporation. In this study, we have investigated the impact of deep freezing on immunology and biopotency for incorporation of bone allografts. Deep frozen bone grafts matched or mismatched for major histoscompatibilty complex (MHC) were implanted in an 8-mm segmental defect in the tibia in rats. The construct was stabilized with intramedullary nailing. The immune response was evaluated by determination of serum antibody against the grafts MHC molecules at day 1 and after 2 and 4 months. Incorporation of the graft was compared with fresh syngeneic grafts and assessed with the use of conventional radiography, biomechanical testing and measurement of bone mineral content and density after 4 months. The analyses revealed no antibody responses in the rats that received grafts from donors differing at histocompatibility loci, and at 4 months the frozen grafts showed an overall reconstruction that was not significantly different from the fresh grafts. This study indicates that in the long run there are no significant consequences; either immunological or biomechanical, of the use of deep frozen allogenous bone as compared to fresh autogenous bone grafts in this animal model.

The enhancement of bone allograft incorporation by the local delivery of the sphingosine 1-phosphate receptor targeted drug FTY720

Poor vascularization coupled with mechanical instability is the leading cause of post-operative complications and poor functional prognosis of massive bone allografts. To address this limitation, we designed a novel continuous polymer coating system to provide sustained localized delivery of pharmacological agent, FTY720, a selective agonist for sphingosine 1-phosphate receptors, within massive tibial defects. In vitro drug release studies validated 64% loading efficiency with complete release of compound following 14 days. Mechanical evaluation following six weeks of healing suggested significant enhancement of mechanical stability in FTY720 treatment groups compared with unloaded controls. Furthermore, superior osseous integration across the host–graft interface, significant enhancement in smooth muscle cell investment, and reduction in leukocyte recruitment was evident in FTY720 treated groups compared with untreated groups. Using this approach, we can capitalize on the existing mechanical and biomaterial properties of devitalized bone, add a controllable delivery system while maintaining overall porous structure, and deliver a small molecule compound to constitutively target vascular remodeling, osseous remodeling, and minimize fibrous encapsulation within the allograft–host bone interface. Such results support continued evaluation of drug-eluting allografts as a viable strategy to improve functional outcome and long-term success of massive cortical allograft implants.

Effects of low intensity pulsed ultrasound with and without increased cortical porosity on structural bone allograft incorporation

BackgroundThough used for over a century, structural bone allografts suffer from a high rate of mechanical failure due to limited graft revitalization even after extended periods in vivo. Novel strategies that aim to improve graft incorporation are lacking but necessary to improve the long-term clinical outcome of patients receiving bone allografts. The current study evaluated the effect of low-intensity pulsed ultrasound (LIPUS), a potent exogenous biophysical stimulus used clinically to accelerate the course of fresh fracture healing, and longitudinal allograft perforations (LAP) as non-invasive therapies to improve revitalization of intercalary allografts in a sheep model.MethodsFifteen skeletally-mature ewes were assigned to five experimental groups based on allograft type and treatment: +CTL, -CTL, LIPUS, LAP, LIPUS+LAP. The +CTL animals (n = 3) received a tibial ostectomy with immediate replacement of the resected autologous graft. The -CTL group (n = 3) received fresh frozen ovine tibial allografts. The +CTL and -CTL groups did not receive LAP or LIPUS treatments. The LIPUS treatment group (n = 3), following grafting with fresh frozen ovine tibial allografts, received ultrasound stimulation for 20 minutes/day, 5 days/week, for the duration of the healing period. The LAP treatment group (n = 3) received fresh frozen ovine allografts with 500 μm longitudinal perforations that extended 10 mm into the graft. The LIPUS+LAP treatment group (n = 3) received both LIPUS and LAP interventions. All animals were humanely euthanized four months following graft transplantation for biomechanical and histological analysis.ResultsAfter four months of healing, daily LIPUS stimulation of the host-allograft junctions, alone or in combination with LAP, resulted in 30% increases in reconstruction stiffness, paralleled by significant increases (p < 0.001) in callus maturity and periosteal bridging across the host/allograft interfaces. Longitudinal perforations extending 10 mm into the proximal and distal endplates filled to varying degrees with new appositional bone and significantly accelerated revitalization of the allografts compared to controls.ConclusionThe current study has demonstrated in a large animal model the potential of both LIPUS and LAP therapy to improve the degree of allograft incorporation. LAP may provide an option for increasing porosity, and thus potential in vivo osseous apposition and revitalization, without adversely affecting the structural integrity of the graft.

Histological and immunohistochemical analysis of an allogenic bone graft engineered with autologous bone marrow mononuclear cells in the treatment of a large segmental defect of the ulna. A case report

The treatment of large (6 cm) segmental bone defects, especially in areas associated with soft tissue damages and exposure, is challenging. Massive bone allografts are widely used in reconstructive surgery to replace missing bone parts such as critical size defects, nevertheless, early vascular invasion is a critical factor in bone allograft incorporation and in the consequent success of the surgery. Unfortunately, it has been proven that only slow and incomplete bone integration is possible by using frozen allografts in the treatment of large bone defects. An allogenic frozen bone graft was engineered with bone marrow mononuclear cells (BMMCs) to repair a large ulna defect in a male patient. When infection and sinus developed at the graft site 4 months after implantation, the partially reabsorbed graft was removed and send to the lab for examination. The histological and immunohistochemical analysis performed on a graft removed from the central zone of the defect demonstrated areas of neo-vascularisation, indicating that a remodelling process was actively occurring even in an area not usually repopulated with the conventional techniques. For these reasons, we may hypothesise that the use of BMMCs has a role in the re-building of large segmental defects.

Particulate Bone Allograft Incorporation in Regeneration of Osseous Defects; Importance of Particle Sizes

Packing of bone defect with particulate allografts is a commonly performed clinical procedure. However, the ideal size of bone particles used to fill bone defects is ill-defined. For this reason the study of biology of bone allografts with different particle sizes has been performed. Standard size bone defects in the femur and the tibia of experimental animals were filled with freeze-dried cortical bone allografts with particle sizes of 1-2mm, 800-500μm, 500-300μm, 300-90μm, 250-125μm, 125-106μm, 106 to 75μm and 75-25μm. Unfilled defects and those filled with autologous bone served as controls. Cortical bone was chosen because it produced better clinical results than did cancellous bone. Likewise freeze-dried particulate bone effected more rapid healing than did frozen bone. Numerical scores were assigned to each defect based on the gross, radiographic and histomorphometric studies. Particles in the range of 300 to 90 microns produced rapid healing by direct ossification. Particles below 100µm had a significantly reduced osteogenic potential. Particles in the range of 75-25μm failed to heal the defects all together. Healing of defects packed with particles larger than 300μm was slower than with 300 – 90 μm grafts. Rapid healing of bone defects packed with particulate bone allografts in the range of 300 to 90μm indicates such allografts can be used effectively in the filling of bone defects. This is of clinical relevance.

Analysis of Cartilage Tissue on a Cellular Level in Fresh Osteochondral Allograft Retrievals

Background Fresh human osteochondral allografting is a biological cartilage replacement technique used to treat articular and osteoarticular defects in the knee. A small number of grafts fail, and we analyzed every retrieved graft during a 4-year period in order to learn more about the potential causes of failure. Hypothesis A large percentage of chondrocytes still remain viable many years after fresh osteochondral allografting. Study Design Descriptive laboratory study. Methods Retrieval specimens were obtained at the time of revision surgery and immediately analyzed. Chondrocyte viability and viable cell density were determined using a live/dead staining technique followed by confocal microscopy. Glycosaminoglycan content was a measure of the cartilage matrix. Radiolabeled sulfate uptake served as a biochemical marker of chondrocyte metabolic activity. Cartilage and subchondral bone were examined histologically. Results Fourteen patients yielded a total of 26 retrieval specimens that had been originally implanted as individual fresh osteochondral allografts. Average graft survival was 42 months. Chondrocyte viability was 82% ± 17%, and chondrocyte viable cell density was 15 590 ± 5900 viable cells/mm3. Retrieved tissue demonstrated radiolabeled sulfate uptake of 437 ± 270 counts per minute and 3.5% ± 0.8% hexosamine per dry weight. Histologically, all specimens showed some degree of cartilage fibrillation. There was evidence of bone allograft incorporation in most specimens, as well as pannus formation in 4 specimens, but no evidence of immune rejection. Conclusion A small percentage of fresh osteochondral allografts fail, but the precise cause is unknown. The main theories for failure investigated here include immunologic rejection, failure of bony incorporation, and chondrocyte death causing breakdown of the cartilage matrix. We show that chondrocytes remain viable many years after transplantation, allograft bone incorporates, and immune rejection does not seem to play a primary role in failure. Clinical Relevance Fresh osteochondral allografting is becoming more common in the treatment of articular cartilage defects in the knee. Our findings support the paradigm of fresh osteochondral allografting, the transplantation of hyaline cartilage with biological incorporation of the underlying bone scaffold. The reasons for failure of a small percentage of grafts remain unclear.

COX‐2 has a Critical Role During Incorporation of Structural Bone Allografts

Nonsteroidal anti-inflammatory drugs (NSAIDs), which inhibit cyclooxygenase (COX) activity, reduced pain and are commonly used in patients with skeletal injury. In this article we will also present data to show that selective COX-2 inhibitor delays allograft healing and incorporation. In contrast, local delivery of prostaglandin E2 (PGE2) enhanced bone formation at cortical bone graft junction. A 4-mm mid-diaphyseal segmental femoral defect was created and then repaired by frozen bone allograft of the same size. A 22-gauge metal pin was placed in the intramedullary cavity to stabilize the bone graft. Healing was evaluated weekly by X ray and by a semiquantitative histomorphometric analysis at 5 weeks postsurgery. Celecoxib (25 mg/kg/day) and Ketorolac (4 mg/kg/day) were administered daily for 2 weeks or 5 weeks. PGE2 was infused locally at a dose of 800 nmol/kg per day via osmotic minipump for 4 weeks. Inhibition of cyclooxygenase by daily administration of the Celecoxib or Ketorolac for 5 weeks reduced new bone ingrowth by about 60% (P < 0.05). The percentage of bony bridging in both drug-treated groups was significantly decreased at 5 weeks. Temporal administration of Celecoxib for 2 weeks also significantly reduced bone formation by 45% and withdrawal of the Celecoxib only led to slight recovery of bone formation at the graft side. In contrast to the inhibitory effects of NSAIDS, PGE2 infusion at the cortical bone junction increased bone formation by about twofold. These results demonstrated that COX-2 is essential for bone allograft incorporation. Furthermore, our data support the notion that COX-2-dependent PGE2 produced at the early stage of bone healing is prerequisite for efficient skeletal repair.

The Effect of Host Tissue Irradiation on Large-Segment Allograft Incorporation

Therapeutic radiation delivered to bone and the adjacent local tissues before allograft limb-salvage surgery has been associated with poor graft incorporation and higher numbers of clinical complications. Our objective was to determine the effect of preoperative radiation therapy on specific histologic, molecular and structural parameters of large-segment, bone allograft incorporation in a canine model. Skeletally mature dogs received a total of 0, 25, or 50 Gy of radiation to the foreleg (radius and ulna) delivered in 2-Gy fractions during a 5-week period before reconstruction of a 3.5-cm defect in the radius. The dogs were sacrificed at postoperative day 150. Nondestructive four-point bending was done on the harvested allograft-host bone immediately after euthanasia and specimens were compared using biomechanical, histomorphometric, immunohistochemical, and in situ reverse transcription polymerase chain reaction techniques. Preoperative irradiation significantly impaired allograft incorporation as determined by radiographic healing scores, histomorphometry, and frequency of nonunions. Biochemical differences included diminished bone morphogenetic protein-2 and bone morphogenetic protein-4 protein levels and messenger ribonucleic acid expression. Vascular endothelial growth factor expression was not altered. These data suggest that bone morphogenetic protein-2 and bone morphogenetic protein-4 signaling at the allograft-host junction is altered after preoperative fractionated radiation and provides a plausible albeit partial mechanistic explanation for radiation-mediated delays in allograft incorporation.

Stromal Stem Cells and Platelet-Rich Plasma Improve Bone Allograft Integration

Early vascular invasion is a key factor in bone allograft incorporation. It may reduce the complications related to slow and incomplete bone integration. Bone-marrow-derived stromal stem cells associated with platelet-rich plasma are potent angiogenic inducers proven to release vascular endothelial growth factor. Our goal was to test whether the combination of stromal stem cells and platelet-rich plasma is able to increase massive allograft integration in a large animal model with sacrifice at 4 months. A critical defect was made in the mid-diaphysis of the metatarsal bone of 10 sheep; the study group received an allograft plus stromal stem cells, platelet-rich plasma, and collagen (six animals) and the control group received only the allograft (four animals). Investigation was done with radiographs, mechanical tests and histomorphometric analysis, including new vascularization. Results showed substantial new bone formation in the allograft of the study group. Bone formation is correlated with better vascular invasion and remodeling of the graft in the study group. These results confirm the key role played by stromal stem cells and platelet-rich plasma in bone repair. Further studies are needed to better define the role stromal stem cells play when implanted alone.

Blood vessel formation after soft-tissue implantation of hyaluronan-based hydrogel supplemented with copper ions

The possibility of ameliorating bone healing of implanted bone allografts is a field of great interest. Early vascular invasion is a key factor in bone allograft incorporation. It is well known that copper ions (Cu 2+) show a proangiogenic action favouring the development of new vessels. In this work a hyaluronan based 50% hydrogel (Hyal-50%) was enriched with (Cu 2+) and its proangiogenic activity was evaluated. Fifteen Sprague Dawley female rats were submitted to the subcutaneous implantation of Hyal-50%, freeze-dried bone allografts, Hyal-50%-Cu 2+, freeze-dried bone allografts plus Hyal-50% and freeze-dried bone allografts plus Hyal-50%-Cu 2+. One month later, histomorphometric analysis evidenced the presence of a fibrous-reactive capsule around all specimens showing significant differences among groups ( p<0.0005). The highest thickness of the fibrous capsule was found around the freeze-dried bone implants ( p<0.05); as well as the Hyal-50%-Cu 2+ plus freeze-dried bone (15.2%, p<0.05) and Hyal 50% plus freeze-dried bone (21.4%, p<0.0005) implants showed a significant higher thickness compared with Hyal 50% and Hyal-50%-Cu 2+. Statistical analysis showed a significant ( p<0.01) higher vascular density in Hyal- 50%-Cu 2+ and Hyal-50%-Cu 2+ plus freeze-dried bone group when compared to other groups. The present preliminary results suggest the advantages offered by the combined use of a well-known biocompatible and tissue healing promoting material (Hyal-50%) and a new technique that consists of stimulating tissue vascularization using Cu 2+ and that bone allograft incorporation may benefit from this technology.

Rehabilitation after total femur replacement: a report of 2 cases

We describe the rehabilitation of 2 patients who underwent total femur replacement after neoplastic involvement of the bone. In the past, patients with cancer of the femur were generally advised to undergo a hip disarticulation or transfemoral amputation. It is now feasible to salvage the limb in selected patients, by excising the entire femur together with any contiguous soft tissue tumor and replacing it with an endoprosthesis. The surgical literature contains a number of reports on total femur replacement, which mention the rehabilitation aspects only briefly, but we found nothing on this relatively uncommon form of surgery in the rehabilitation literature. Physiotherapy techniques such as active assisted exercises, isometric exercises, and hydrotherapy are extremely useful during the early phase of rehabilitation to facilitate a graduated strengthening program. Certain exercises, such as active hip abduction or knee flexion, may not be permitted for several weeks to protect muscles that have been reattached to the prosthesis. Partial weight bearing may be required to allow incorporation of bone allograft around the prosthetic hip joint. Because of these factors patients with total femur replacement may need a longer period of rehabilitation (6–8wk) than patients with total hip or knee replacement. Patients with total femur replacement can, however, achieve full independence with an appropriate rehabilitation program.

The role of stainless steel wire mesh and cement in bone allograft incorporation in impaction grafting technique: An experimental study in rabbits

Cages of flexible stainless steel wire mesh were filled with impacted morcellized cancellous allograft. Bone defects were created in both tibial metaphyseal regions of 10 adult white New Zealand rabbits. The base of both defects was plugged with a small amount of bone cement. The cages were implanted in the right tibia while the left tibia was filled with impacted bone allograft. Histologic and histomorphometric evaluation of the retrieved specimens at 3 months showed a statistically significant difference in active bone formation parameters between the 2 groups. Active bone formation was more prominent away from the bone cement. The biological process of bone graft incorporation in the “impaction grafting” technique seems to be adversely affected by stainless steel wire mesh and in areas adjacent to bone cement.

Rinsing morselized allografts improves bone and tissue ingrowth.

Bone defects in revision hip surgery can be reconstructed with impacted morselized bone grafts. Rinsing these trabecular allografts may enhance graft incorporation by washing out immunogenic factors present in blood, marrow, and fat. However, it has been proposed that impaction of the graft releases biologically active factors, which can provide sufficient activity to stimulate new bone formation. Rinsing before impaction could enhance bone allograft incorporation, but rinsing after impaction could diminish the incorporation process of impacted bone graft. To study the effect of rinsing and impaction of morselized bone grafts on bone ingrowth, a bone chamber study was done in goats. Autografts and allografts were divided into three treatment groups: (A) impacted; (B) rinsed and impacted; and (C) rinsed, impacted, rinsed, and impacted again. Ten goats received three bone chambers in each proximal tibia. The chambers were filled with either allograft or autograft, yielding six different implants per goat. After 6 weeks, histologic analyses were done and bone and tissue ingrowth were measured. New bone and total tissue ingrowth were higher in autografts than in allografts, especially in the nonrinsed group. With rinsing, total tissue ingrowth increased in the allograft group to approach that of autografts. Rinsing after impaction did not additionally alter bone ingrowth. The current findings show that incorporation of allografts can be improved by rinsing the grafts before impaction.

Incorporation of vancomycin-supplemented bone incorporation of vancomycin-supplemented bone allografts: radiographical, histopathological and immunohistochemical study in pigs.

We compared the incorporation of bone allografts with or without vancomycin in tibial defects of 18 pigs. High-quality radiographs, histological examination, immunological expression of metalloproteinase-13 (MMP-13) and transforming growth factor-beta 2 (TGFbeta2) indicated that there was no significant difference in bone allograft incorporation between up to 220 times the MIC (minimum inhibitory concentration) in bone allografts with 1 g of vancomycin in each 300 g of allograft or without this supplement.

No effect of growth hormone on bone graft incorporation. Titanium chamber study in the normal rat.

A recent series of publications reported greatly improved mechanical properties and increased callus size during the late stages of fracture healing in normal (not hypophysectomized) rats after twice daily injections of growth hormone (GH). We tested whether GH could enhance the incorporation of bone allografts in a new experimental model where we have demonstrated an increase in bone allograft incorporation by local application of basic fibroblast growth factor (bFGF). Cylinders of defatted allogeneic cancellous bone were placed as grafts in titanium Bone Conduction Chambers in the tibiae of female rats. Only one end of this chamber is open for tissue ingrowth. This permits us to measure the distance into the graft that new bone penetrates after entering the chamber. We injected 10 rats with 1.5 IU per rat of subcutaneous human recombinant GH twice daily for 6 weeks and another 10 rats with similar doses of sterile normal saline. GH caused a constant increase in the rate of weight gain and in the serum concentration of insulin-like Growth Factor 1 (IGF 1). Tibiae became longer and the ash weight of the second tail vertebra was increased. We also noted an increased joint cartilage thickness. There was no difference in the amount of new bone that had penetrated and replaced parts of the graft in GH-treated or control rats and this was also the case with TcMDP activity of bone samples from both groups. New bone forms in the grafts by membranous (metaplastic) ossification. It appears that the effects of excessive GH stimulation on endochondral and membranous ossification in this model are markedly different.