Membranous Bone Grafts Research Articles

Role of Masquelet’s technique in the induction of membrane and secondary bone grafting in patients of long bone fractures with bone loss

Role of Masquelet’s technique in the induction of membrane and secondary bone grafting in patients of long bone fractures with bone loss

Antibiotic Cement Spacer and Induced Membrane Bone Grafting in Open Distal End Femur Fractures with Bone Loss; Radiographic and Functional Outcomes: A Retrospective Study

Background: Open fractures are a difficult entity, often complicated by infection and nonunion. Bone loss in such fractures adds to the complexity. Conventional techniques of bone defect management are mainly directed toward fracture union but not against preventing infection or joint stiffness.Objectives: In this study, we evaluated Masquelet's technique for the management of open distal end Femur fractures with bone loss.Methods: Twenty-two patients with open distal end fractures with bone defects who presented within 3 days of trauma from January 2015 to December 2018, treated by the Masquelet's technique are included in this study. All the patients were operated on by the same surgeon. All the patients were taken up for the first stage of surgery immediately after the presentation. Details of the type of injury, location, soft-tissue condition, length of bone defect, type of fixation, the time difference between antibiotic cement spacer placement and bone grafting, and time to the union were documented.Results: Fractures with Type IV bone loss (segmental loss) united slower than fractures having some cortical continuity (Type II and III), P=0.003. In Type IV, the bone loss average time to union was 316.6±44.5 days, whereas, in Type III and II, it was 240±30 and 180, respectively. In the first stage, internal fixation with antibiotics cement spacer was done in all cases. In patients with internal fixation with 2nd stage spacer removal plus bone grafting done, time to union was 244.1±42.9 days. No patients had an infection after the first stage of surgery.Conclusion: The technique of delayed bone grafting after the initial placement of a cement spacer provides a reasonable alternative for the challenging problem of significant bone loss in extremity reconstruction. This technique can be used in either an acute or delayed fashion with equally promising results. The bioactivity of the membrane created by filling large bony defects with cement leads to a favorable environment for bone formation and osseous consolidation of a large void. As this technique becomes more widely applied, the answer to which graft substances to place in the void may become clearer. Increasing clinical evidence will also help support the use of this technique in treating segmental bone loss.

Antibiotic Cement Spacer and Induced Membrane Bone Grafting in Open Fractures with Bone Loss: A Case Series.

Background:Open fractures are a difficult entity, often complicated by infection and nonunion. Bone loss in such fractures adds to the complexity. Conventional techniques of bone defect management are mainly directed toward fracture union but not against preventing infection or joint stiffness. In this case series, we evaluated Masquelet's technique for management of open fractures with bone loss.Materials and Methods:Twenty seven open fractures with bone defect, which presented within 3 days of trauma were planned for treatment by Masquelet's technique. Followup ranged from 21 to 60 months.Results:Average length of bone defect was 6 cm. Radiological union was obtained at a mean of 280 days since first stage of surgery. Time for union was not related to the size of defect. Union was faster in metaphyseal region (265.6 ± 38.8 days) as compared to diaphysis (300.9 ± 58.6 days). No patient had residual infection after stage 1. All the patients were able to mobilize with full weight bearing after radiological union with a satisfactory range of motion of adjacent joints.Conclusion:This technique can be routinely applied in compound fractures with bone loss with good results. Chances of infection are reduced using antibiotic cement spacer as an adjunct to thorough debridement. Induced biomembrane revascularizes the graft. Union can be expected in most of the cases, however, long time to union is a limitation. Technique is cost-effective and does not require special training or instrumentation. Although it is a two-stage surgery, requirement of multiple surgeries, as may be needed in conventional methods, is avoided.

Masquelet technique to treat a septic nonunion after nailing of a femoral open fracture

Septic nonunion is one of the most serious complications after an open fracture because both the infection and the bone defect need to be dealt with.Treatment is always protracted and expensive, and the result is uncertain.In the 1980s, Masquelet first described the technique of the induced membrane and autologous bone grafting to manage critical size bone defects.In septic nonunions, the described approach, characterised by two different surgical steps, allows a radical approach to manage the infection, and gives a significant biological stimulus to bone healing.In this case, we present a 35-year-old male patient with an open grade II femoral shaft fracture (AO / OTA 32C3). The patient was initially treated with an intramedullary nail and the resulting septic nonunion was subsequently managed with the induced membrane technique and a double-plate osteosynthesis to protect the biological chamber.

Guided tissue regeneration in communicating periodontal and endodontic lesions - A hope for the hopeless!

The use of guided tissue regeneration (GTR) has become a standard of care in Periodontology. GTR using membrane barriers and/or bone grafting materials has also been used in periapical surgery. However, the application of the GTR principle, particularly in communicating endodontic-periodontal lesions with loss of the buccal cortical plate, is a very challenging task, with very few reported human clinical studies. An interdisciplinary approach, combining endodontic and periodontal (surgical) procedures can save a tooth in the long run that has been defined as hopeless at the preliminary stage of treatment.

Secondary Alveolar Bone Grafting: the Dilemma of Donor Site Selection and Morbidity

Fresh autogenous cancellous bone is ideal for secondary alveolar cleft bone grafting because it supplies living, immunocompatible bony cells that integrate fully with the maxilla and are essential for osteogenesis. Recent animal studies have shown that the dynamics of cancellous inlay bone grafts are different from those of cortical onlay bone grafts, and they refute the assumption that membranous bone grafts are superior to endochondral bone grafts because of their embryological origin. These studies prove that inlay endochondral cancellous specimens have a higher percentage increase in actual bony volume than cortical membranous and cortical endochondral inlay bone grafts. There are various donor sites for secondary alveolar cleft bone grafts. Currently the main sites for autogenous cancellous bone are iliac crest, calvarium, mandibular symphysis, and tibia. Some authors have suggested that the iliac crest donor site causes an unacceptably high degree of postoperative morbidity, but it is still the first choice for secondary alveolar cleft bone grafts and should not be rejected solely because of such concerns. Recombinant human bone morphogenetic protein-2 (rhBMP-2) is now an attractive bony substitute that promotes the differentiation of pluripotential cells into bone-forming cells that lay down new host bone in the site of the defect. Much more research and development are necessary to find a suitable carrier for rhBMP-2, and to study the properties of newly formed bone that it has induced before it can be a substitute for autogenous bone.

Cortical Tenting Grafting Technique in the Severely Atrophic Alveolar Ridge for Implant Site Preparation

Alveolar ridge augmentation using intraoral autogenous block grafts to augment localized alveolar ridge defects before implant placement is a predictable method. However, large severely atrophic edentulous segments may require extraoral donor sites. The purpose of this study was to evaluate the effectiveness of using intraoral cortical block grafts in combination with particulate human mineralized allograft, in a "tenting" fashion, to augment large atrophic alveolar ridge defects for implant placement. This prospective case study evaluated augmentation in 10 consecutive patients with severely resorbed alveolar ridges missing a minimum of 4 adjacent teeth. Before augmentation, all grafted sites were deemed inadequate for placement of a standard 4-mm-diameter implant. Horizontal ridge augmentation was performed using autologous membranous cortical bone grafts from an oral donor site to tent out the soft tissue matrix and periosteum for the adjacent particulate allograft. The ridges were clinically evaluated 4 to 5 months after augmentation, and 42 implants were placed at that time. Implants were successfully placed at all grafted sites 4 to 5 months after the original graft date. Clinical evaluation of the grafted sites upon re-entry revealed uniform ridge anatomy. All edentulous segments had at least 2 implants placed of at least 4.0 mm diameter. In all, 42 implants were placed into grafted sites in the 10 patients. Implants were checked for osseointegration by using a counter torque of 35 N.cm. One implant failed to integrate. Mean follow-up was 22 months after implant placement. All augmented ridges had retained their functional and esthetic integrity at 1 year after original augmentation. Tenting of the periosteum and soft tissue matrix using a cortical bone block maintains space and minimizes resorption of the particulate allograft volume. In addition, bridging the cortical blocks with particulate bone avoids unaesthetic ridge defects between cortical block grafts in larger ridge defects. The result was a more uniform and esthetic alveolar ridge, capable of maintaining an implant-supported prosthesis. The technique offers predictable functional and esthetic reconstruction of large-volume defects without extensive amounts of autogenous bone. This offers a superior functional and esthetic result than with either cortical or particulate grafting alone.

The Medial Surface of the Mandible as an Alternative Source of Bone Grafts in Orthognathic Surgery

A technique of harvesting bone grafts from the medial surface of the angle of the mandible during a bilateral sagittal split osteotomy procedure is described. In 20 patients who underwent mandibular setback for the correction of class III dentofacial deformities, bone grafts were harvested from the medial mandibular angle and used for simultaneous augmentation of the midface or for interpositioning and stabilization of the maxilla after LeFort I maxillary anterior or inferior repositioning. The mean postoperative follow-up was 6 months (range, 3-12 months). No complications occurred, and postoperative morbidity was similar to that encountered by patients who undergo sagittal split osteotomy without bone harvest. The technique described shows that the medial mandibular angle is a suitable donor site for membranous bone grafts in patients who undergo sagittal split osteotomy.

Long‐term stability of autogenous bone grafts following combined application with guided bone regeneration

The aim of the study was to compare the long-term stability of membranous and endochondral autogenous bone grafts with or without combined application of guided bone regeneration (GBR). Twenty-five, male, 6-month old, albino rats were used in the study. The animals were divided into four groups (A5, A11, B5 and B11). Group A5 (control): The inferior border of the mandible was exposed in both sides. At one side of the jaw, a calvarial bone graft (baseline -3 x 4 x 0.64 mm) was placed at the inferior border of the mandible and was fixed with a standardized screw-type titanium microimplant. At the contralateral side, an ischiac bone graft (baseline -3 x 4 x 0.87) was transplanted. The healing period was 5 months. Group A11 (control): The animals were treated in the same manner as in Group A5 with the difference that the healing period was 11 months. Group B5 (test): The animals were treated in the same manner as in Group A5 with the difference that an e-PTFE membrane was adapted over the bone graft on each side of the jaw. Group B11 (test): The animals were treated in the same manner as in Group B5 with the difference that 5 months following transplantation the animals were subjected to a second operation and the membranes were removed. The healing period was 11 months. The animals were killed at 5 (Groups A5 and B5) or at 11 months (Groups A11 and B11) following mandibular augmentation and the jaws were defleshed. The width, the length and the thickness/height of the bone graft were evaluated by means of a stereomicroscope. At 5 months, both types of the membrane-treated bone grafts presented increase in all dimensions compared with baseline. However at 11 months, both types of the membrane-treated bone grafts exhibited a decrease in their dimensions which were similar to the baseline measurements. In the control groups, both types of bone graft presented significant resorption both at 5 and at 11 months with the ischiac bone grafts presenting more resorption in width and length than the calvarial bone grafts. It can be concluded that the long-term volume stability of autogenous endochondral and membranous onlay bone grafts combined with GBR is superior to that of autogenous endochondral and membranous onlay bone grafts alone.

Allogeneic bone grafting of calvarial defects: an experimental study in the rabbit

Abstract. The purpose of this study was to investigate the incorporation of fresh frozen irradiated membranous allogeneic bone grafts into critical size calvarial defects in the rabbit. Fifteen rabbits had calvarial defects prepared. Twelve rabbits received allogeneic grafts and three received autogenous bone grafts. The rabbits were sacrificed at 9 and 12 months postoperatively, and the specimens were examined radiologically, histopathologically and with fluorescence microscopy. Neovascularization, bone marrow regeneration and new bone formation was evident throughout the grafts however revitalization of the entire graft was incomplete at 12 months. This study revealed that the FFI membranous grafts were well incorporated into rabbit calvarial defects.

Early Revascularization of Membranous Inlay Bone Graft in Canine Mandible Model

The early revascularization of a membranous inlay bone graft in a canine mandible was investigated using bone scans and histological examinations. Eight 5-month-old mongrel dogs were used as the subjects. The inlay bone graft, a 1- x 2-cm critically sized bone, was completely separated from the lower border of the canine mandible and then refixed to the original site. Bone scans and histological examinations were performed in the first, second, third, and fourth postoperative weeks. The bone scan in the first postoperative week revealed radioisotope uptake on the margin of the grafted bone with an isotope count that was 21% of the normal bone uptake. In the second postoperative week, the radioisotope uptake in the grafted bone increased to 52% of the normal bone uptake. In the third and fourth postoperative weeks, the isotope uptakes were 111% and 124%, respectively. The histological findings in the first postoperative week showed an absence of osteoblastic activity and 6 viable blood vessels in a field magnified x 200, which was the equivalent of 25% of the vessels of the normal bone. In the second postoperative week, osteoblastic activity was noted, and the number of viable blood vessels increased to 15, that is, 63% of the vessels of the normal bone. In the third postoperative week, there was an increase in osteoblastic activity, and the number of viable blood vessels was 21, that is, 88% of the vessels of the normal bone. In the fourth postoperative week, there was a marked increase in osteoblastic activity with the number of vessels reaching 23, that is, 96% of the normal bone. In summary, revascularization of the membranous inlay bone graft began within the first week after the bone graft and thereafter gradually increased. In the third postoperative week, revascularization returned to a near-normal value compared with the value of the adjacent normal mandibular bone.

A Comparative Analysis of the Microarchitecture of Cortical Membranous and Cortical Endochondral Onlay Bone Grafts in the Craniofacial Skeleton

Previous work in this laboratory established that an onlay bone graft's survival is determined primarily by its relative cortical and cancellous composition rather than its embryologic origin. A volumetric analysis of external bone graft resorption, however, does not explain the internal microarchitectural changes that may be occurring as these grafts become incorporated. To expand the knowledge of bone graft dynamics beyond volumetric parameters, a better understanding of the internal processes of bone graft remodeling is needed. In this comparative study of cortical onlay bone graft microarchitecture, the authors propose to show that cortical onlay bone grafts undergo measurable internal microarchitectural changes as they become incorporated into the surrounding craniofacial skeleton. In addition, the authors propose to further demonstrate similarities between the internal microarchitecture of cortical onlay bone grafts of different embryologic origin over time. Twenty-five adult New Zealand White rabbits were used for this study. They were divided into two groups of eight animals and one group of nine. The groups were killed at 3, 8, and 16 weeks. Cortical membranous and endochondral bone grafts were placed subperiosteally onto each rabbit's cranium. In addition, five ungrafted cortical endochondral and membranous bone specimens were used as controls. Microcomputed tomography (MCT) scanning and histomorphometric analysis were performed on all of the specimens to obtain detailed information regarding the microarchitecture of the cortical bone grafts. The parameters of bone volume fraction, bone surface area to volume, mean trabecular number, and anisotropy were used to give quantitative information about a bone's micro-organization. The results showed that there is no statistically significant difference between the cortical endochondral and the cortical membranous bone grafts for bone volume fraction, bone surface to volume, mean trabecular number, and anisotropy measurements for all time points. There were, however, statistically significant differences when comparing the control and 3-week groups to the 16-week group for all parameters. The advanced MCT technology and histomorphometric techniques proved to be effective in providing a qualitative and quantitative ultrastructural comparison of cortical endochondral and membranous onlay bone grafts over time. In this study, a statistically significant change in the internal microarchitecture of cortical onlay bone grafts of different embryologic origins was seen as they were remodeled and resorbed at all time points. Specifically, the onlay cortical bone grafts developed a less dense, more trabecular, and less organized internal ultrastructure. In addition, no difference in the three-dimensional ultrastructure of cortical endochondral and membranous bone was found. These results challenge some of the currently accepted theories of bone-graft dynamics and may eventually lead to a change in the way clinicians approach bone-graft selection for craniofacial surgery. (Plast. Reconstr. Surg. 104: 139, 1999.)

Increased IGF-I and IGF-II mRNA and IGF-I Peptide in Fusing Rat Cranial Sutures Suggest Evidence for a Paracrine Role of Insulin-Like Growth Factors in Suture Fusion

Previous work in this laboratory established that an onlay bone graft's survival is determined primarily by its relative cortical and cancellous composition rather than its embryologic origin. A volumetric analysis of external bone graft resorption, however, does not explain the internal microarchitectural changes that may be occurring as these grafts become incorporated. To expand the knowledge of bone graft dynamics beyond volumetric parameters, a better understanding of the internal processes of bone graft remodeling is needed. In this comparative study of cortical onlay bone graft microarchitecture, the authors propose to show that cortical onlay bone grafts undergo measurable internal microarchitectural changes as they become incorporated into the surrounding craniofacial skeleton. In addition, the authors propose to further demonstrate similarities between the internal microarchitecture of cortical onlay bone grafts of different embryologic origin over time. Twenty-five adult New Zealand White rabbits were used for this study. They were divided into two groups of eight animals and one group of nine. The groups were killed at 3, 8, and 16 weeks. Cortical membranous and endochondral bone grafts were placed subperiosteally onto each rabbit's cranium. In addition, five ungrafted cortical endochondral and membranous bone specimens were used as controls. Microcomputed tomography (MCT) scanning and histomorphometric analysis were performed on all of the specimens to obtain detailed information regarding the microarchitecture of the cortical bone grafts. The parameters of bone volume fraction, bone surface area to volume, mean trabecular number, and anisotropy were used to give quantitative information about a bone's micro-organization. The results showed that there is no statistically significant difference between the cortical endochondral and the cortical membranous bone grafts for bone volume fraction, bone surface to volume, mean trabecular number, and anisotropy measurements for all time points. There were, however, statistically significant differences when comparing the control and 3-week groups to the 16-week group for all parameters. The advanced MCT technology and histomorphometric techniques proved to be effective in providing a qualitative and quantitative ultrastructural comparison of cortical endochondral and membranous onlay bone grafts over time. In this study, a statistically significant change in the internal microarchitecture of cortical onlay bone grafts of different embryologic origins was seen as they were remodeled and resorbed at all time points. Specifically, the onlay cortical bone grafts developed a less dense, more trabecular, and less organized internal ultrastructure. In addition, no difference in the three-dimensional ultrastructure of cortical endochondral and membranous bone was found. These results challenge some of the currently accepted theories of bone-graft dynamics and may eventually lead to a change in the way clinicians approach bone-graft selection for craniofacial surgery.

Occipital calvarial bone graft in posterior occipitocervical fusion.

Dorsal occipitocervical fusion is associated with a high rate of fusion failure and requires an additional surgical site for donor bone graft harvesting. In this series, an autologous occipital calvarial bone graft obtained from the same occipitocervical incision with contoured metal loops was used in 25 adults to achieve craniovertebral stabilization and fusion. To study the use of autologous occipital calvarial bone grafts in occipitocervical fusion. Cranial bone grafts have been used successfully in craniofacial reconstruction with good long-term results. In the plastic surgery literature, there are claims that membranous bone grafts are superior to endochondral bone grafts in fusions because of decreased resorption. In recent studies, results have shown successful use of calvarial bone in fusing the upper cervical spine in children. The use of autologous occipital bone in posterior occipitocervical fusions avoids many of the problems associated with traditional donor sites and provides a sufficient quantity of good quality bone for the fusion. This is especially true in the fragile rheumatoid arthritis patient with cranial cervical instability. Split-thickness, autologous calvarial bone grafts with contoured loop and cable instrumentation were used for posterior occipitocervical stabilization and fusion in 25 patients, most of whom had rheumatoid arthritis. The calvarial bone graft was harvested from the occipital skull, using a microair impactor, and was secured next to the loop construct. After surgery, all patients were immobilized with external orthoses. None of the patients had hardware failure or complications from the occipital graft procurement. In 22 patients, good alignment, stability, and bony fusion were shown on radiographs. Occipital calvarial bone graft appears to work as well as other autologous corticocancellous bone grafts routinely used in posterior occipitocervical fusions.

Use of microcomputed tomography scanning as a new technique for the evaluation of membranous bone.

Previous basic bone studies in cranial bone biology and bone grafting have used calipers, volume displacement, and cephalometric tracings to measure membranous bone and to infer fundamental properties of cranial bone. These tools have limited accuracy and reproducibility. Histomorphometry has also been used in the quantitative analysis of cranial bone; however, two-dimensional histology is unable to capture a precise representation of the three-dimensional structure of bone. For the first time, we have used the advanced technology of three-dimensional microcomputed tomographic (micro-CT) scanning as a highly accurate and automated tool to precisely measure changes in bone stereology, volume and projection, and microarchitecture in the evaluation of membranous bone. The advantages of this technology are numerous and include the rapid and nondestructive three-dimensional analysis of bone microstructure at resolutions between 10 and 75 microns. Measures of "connectivity" in three dimensions and the architectural parameter of "anisotropy" are available through micro-CT imaging but can only be inferred through two-dimensional histological series. We successfully imaged two full-thickness cranial bone specimens and one cancellous iliac bone graft. The images demonstrate a similarity between the two membranous specimens and a marked difference in comparison with the endochondral graft. These differences are borne out by mathematical analysis, and their significance is discussed. The utility of micro-CT in the evaluation of membranous bone was displayed by its ability to rapidly calculate differences in bone stereology and to quantitatively measure morphological changes at an ultrastructural level. We believe the benefits of this system will prove to be extremely useful for investigations into the basic biology of membranous bone, bone grafts, and craniofacial interfaces, and we encourage its use by other scientific investigators in the field of craniofacial surgery as they strive for more scientifically rigorous tools to understand the basic biology of membranous bone.

The effect of infection and lag screw fixation on revascularization and new bone deposition in membranous bone grafts in a rabbit model.

We have suggested that rigid fixation of membranous bone grafts in the presence of infection may improve graft-recipient bone union by facilitating graft revascularzation. To test this hypothesis, we grafted autogenous membranous bone grafts to the mandibles of 94 New Zealand White rabbits. Lag screw fixation was applied in half the animals. The wounds were inoculated with a range of Staphylococcus aureus doses. Infected and noninfected rabbits were injected weekly over a 5-week course with fluorescein bone markers and with a marker of vascular endothelium (procion red) just prior to sacrifice. Revascularization and new bone deposition in the grafts were then quantified histologically for the 75 rabbits available for data collection. Infection decreased the amount of graft revascularized and the amount of new bone deposited for both rigidly fixated and nonfixated grafts. Grafts fixated with a lag screw showed a greater amount of revascularization and new bone deposition in the presence and absence of infection when compared with nonfixated grafts, supporting the hypothesis that rigid fixation of membranous bone grafts in the presence of infection may promote graft survival and union by improving revascularization and osteogenesis within the graft.

Cranial Bone Grafting

Rigid internal fixation with miniplates and screws has enabled reconstructive surgeons to position bony segments precisely. Unfortunately, our present systems have been associated with a potential adverse effect on ultimate craniofacial growth and development. Also, they may be palpable, necessitating secondary procedures for removal of the hardware. We have been involved in an ongoing study evaluating the efficacy of a commercially developed biodegradable system. In this study, we compared biodegradable lag screw fixation with traditional titanium screw fixation in full-thickness, membranous bone grafts harvested from the zygomatic arches to the snout in a rabbit model. The results were compared with standard hematoxylin and eosin stains and laser densometry. Although this study adds further credence to the resorption of bone grafts, those secured with the polyglycolic acid screws demonstrated significantly less resorption than those maintained in position by traditional methods.

The Influence of Bony Architecture on Fixed Membranous Bone Graft Survival

The aim of this study was to examine the influence of membranous bone graft architecture on graft survival. Eighteen adult New Zealand rabbits underwent full-thickness harvesting of their zygoma, which was then divided into two parts, resulting in a wider, thicker anterior graft and a tapered posterior graft. The grafts were then rigidly fixed, one to each nasal bone, using titanium lag screws. On postgrafting days 15 and 45, 3 animals each were killed. The remaining 12 animals were killed on day 90. The graft, graft-host interface, and contralateral zygoma were assessed volumetrically, histologically (nondecalcified), and stereologically. Volumetrically, the anterior (thicker, wider) grafts demonstrated 100% survival while the posterior (thinner, more narrow) grafts demonstrated 80% survival (p = 0.004). Histologically, the anterior grafts demonstrated less resorption and porosity and greater labeling activity. At the graft-host interface, the anterior grafts exhibited a 2.5-fold increase in full incorporation of the grafts, and the posterior grafts had almost twice the incidence of nonincorporation. Stereological measurements, including interlabel width (20.3 microns anteriorly, 18.9 microns posteriorly), confirmed the enhanced survival of the anterior grafts. Using multiple forms of analyses, this study demonstrates that membranous bone graft architecture influences graft survival. To assist in understanding these differences, we also analyzed the normal contralateral zygoma. While the anterior and posterior halves had a relatively constant amount of bicortical bone, the thicker grafts had a proportionally greater trabecular component (i.e., increased diploë-to-cortical ratio). In the rabbit model, differences in membranous bone thickness imply differences in the cancellous portion of the graft, thereby influencing ultimate graft survival.

Revascularization of calvarial, mandibular, tibial, and iliac bone grafts in rats.

Some studies have suggested that membranous bone grafts undergo less resorption than endochondral grafts, and faster revascularization of the former has been proposed as the explanation. We studied fresh syngeneic full-thickness bone grafts from calvaria, mandibula, tibia diaphysis, and iliac bone implanted in the back muscles of young Lewis rats. As a measure of the quantity of cancellous bone in grafts before implantation, the ratio of the total area of soft-tissue spaces to the total area of the graft was measured histomorphometrically. Revascularization in grafts 3 weeks postoperatively was evaluated by deposit of 141Ce-labeled microspheres. Both the quantity of cancellous bone (before implantation) and the revascularization (3 weeks postoperatively) were greater in the mandibular and iliac bone grafts than in the calvarial and tibia diaphyseal grafts. The results suggest that the anatomical area of harvest of bone graft is important regarding early revascularization, but the results do not support the theory that different embryological mode of development is the cause since mandibula (high 141Ce index) and calvaria (low 141Ce index) are of membranous origin and iliac bone (high 141Ce index) and tibia (low 141Ce index) are of endochondral origin. The difference in revascularization between the different grafts may be explained by differences in quantity of cancellous bone since cancellous bone is revascularized faster than cortical bone.

The Effect of Infection and Lag Screw Fixation on the Union of Membranous Bone Grafts in a Rabbit Model

Infection complicating craniofacial procedures contributes significantly to patient morbidity and health care costs. The role of fixation materials in this setting remains unclear. As foreign material, does fixation hardware increase patients' susceptibility to developing postoperative infection? Furthermore, once infection is established, should fixation hardware be removed? To answer these questions, we performed an onlay membranous bone grafting procedure to the mandible in 94 New Zealand White rabbits, applied lag-screw fixation in half the animals, and inoculated the wounds with different bacterial doses. We quantified the differential rates of infection and rates of graft union in the presence of infection. The infection rates for the rigidly fixated group were not significantly different from the rates for the nonfixated group for a range of bacterial inoculum doses. There was no significant difference in the rates of resolution of infection and sepsis between the two groups. Gross and histologic assessments revealed a significantly lower union rate for infected grafts when compared with uninfected grafts. Furthermore, grafts rigidly fixated with a lag screw showed a higher rate of union when compared with nonfixated grafts in the presence of infection. In the absence of infection, the union rates for fixated and nonfixated groups did not differ significantly. While fixation hardware has been cited as a risk factor for postoperative infection, we were unable to show that lag-screw fixation contributes to this risk. Although infection impaired the union of membranous bone grafts to the recipient mandible, fixation of the grafts with a lag screw significantly decreased this deleterious effect of infection.(ABSTRACT TRUNCATED AT 250 WORDS)