Structural Bone Allografts Research Articles

Surgical revascularization in structural orthotopic bone allograft increases bone remodeling.

Osseous defects reconstructed with cryopreserved structural allografts are poorly revascularized and therefore are prone to nonunion, infection, deterioration of mechanical properties, and fracture. Whether this can be mitigated by specific interventions such as intramedullary surgical revascularization has been incompletely evaluated. We aimed to study surgical revascularization as a means to improve bone remodeling in cryopreserved allograft. Second, we questioned whether spatial histomorphometric differences occur in cortical bone areas after intramedullary surgical revascularization. Third, biomechanical properties of the graft-recipient construct in surgically revascularized allograft were compared with those of conventional allografts. Allografts were harvested from 10 Brown Norway rats, cryopreserved, and transplanted orthotopically in a 10-mm defect in two groups of 10 Lewis rats each (major histocompatibility mismatch). In the control group, no surgical revascularization was performed, whereas in the experimental group, a saphenous arteriovenous bundle was transposed in the bone marrow cavity. Bone remodeling was measured with histomorphometry, histology, and microcomputed tomography at 16 weeks. Spatial differences were analyzed with histomorphometry. To determine biomechanical properties, load at failure and structural stiffness in bending were evaluated by the three-point bend testing. In both groups, normal values of the contralateral femur also were analyzed. Surgically revascularized allografts had increased bone remodeling (bone formation rate to bone surface ratio: 130 ± 47 µm(3)/µm(2)/year versus 44 ± 43 µm(3)/µm(2)/year, p = 0.006) and higher cortical osteocyte counts (18.6% ± 12.7% versus 3.1% ± 2.8%, p = 0.002) than nonrevascularized grafts. In nonrevascularized grafts, the bone formation rate to bone surface ratio was 35% of the contralateral normal values, whereas in surgically revascularized grafts, the bone formation rate to bone surface ratio in the grafts exceeded the contralateral values (110%). Microcomputed tomography did not show differences in bone volume between groups, however in both groups, bone volume was less in grafts compared with the contralateral femurs. Inner cortical bone formation rate to bone surface ratio was greater in surgically revascularized grafts (65 ± 30 µm(3)/µm(2)/year versus 13 ± 16 µm(3)/µm(2)/year in the control group, p = 0.012). Outer cortical bone formation rate to bone surface ratio also increased in surgically revascularized grafts (49 ± 31 µm(3)/µm(2)/year versus 19 ± 21 µm(3)/µm(2)/year, p = 0.032). No differences were found in load at failure and structural stiffness between both groups. In the control group, load at failure and structural stiffness were lower in grafts than in the contralateral femurs (p = 0.004 and p = 0.02, respectively). In the experimental group, surgically revascularized grafts also had lower load at failure and structural stiffness than the contralateral femurs (p = 0.008 and p = 0.02, respectively). Surgical revascularization of large segmental allografts improved bone remodeling and viability without an adverse effect on total bone volume or bending strength and stiffness in this short-term analysis. Cryopreserved allografts remain largely necrotic and are associated with a high rate of complications. Surgical revascularization increases graft healing which could contribute to graft survival with time.

Bone mineral density and donor age are not predictive of femoral ring allograft bone mechanical strength.

While metal or plastic interbody spinal fusion devices are manufactured to appropriate mechanical standards, mechanical properties of commercially prepared structural allograft bone remain relatively unassessed. Robust models predicting compressive load to failure of structural allograft bone based on easily measured variables would be useful. Three hundred twenty seven femoral rings from 34 cadaver femora were tested to failure in axial compression. Predictive variables included age, gender, bone mineral density (BMD), position along femoral shaft, maximum/minimum wall thickness, outer/inner diameter, and area. We used support vector regression and 10-fold cross-validation to develop robust nonlinear predictive models for load to failure. Model performance was measured by the root-mean-squared-deviation (RMSD) and correlation coefficients (r). A polynomial model using all variables had RMSD = 7.92, r = 0.84, indicating excellent performance. A model using all variables except BMD was essentially unchanged (RMSD = 8.12, r = 0.83). Eliminating both age and BMD produced a model with RMSD = 8.41, r = 0.82, again essentially unchanged. Compressive strength of structural allograft bone can be estimated using easily measured geometric parameters, without including BMD or age. As DEXA is costly and cumbersome, and setting upper age-limits for potential donors reduces the supply, our results may prove helpful to increase the quality and availability of structural allograft.

Ankle Salvage Surgery with Autologous Circular Pillar Fibula Augmentation and Intramedullary Hindfoot Nail

Tibiotalocalcaneal arthrodesis with an intramedullary hindfoot nail is an established procedure for fusion of the ankle and subtalar joints. In cases involving ankle bone loss, such as in failed total ankle replacement, it can be difficult to salvage with sufficient bone restoration stability and a physiologic leg length and avoiding below the knee amputation. In addition to the alternatives of using a structural allograft or metal bone substitution, we describe the use of autologous ipsilateral circular pillar fibula augmentation in tibiotalocalcaneal retrograde nail arthrodesis combined with a ventral (anterior) plate in a prospective series of 6 consecutive cases with a mean follow-up duration of 26 ± 9.95 (range 12 to 34) months. The 6 patients (3 female and 3 male), with a mean age of 55 ± 13.89 (range 38 to 73) years were treated with revision surgery of the ankle (1 after talectomy, 5 [83.33%] after failed ankle replacement). The visual analog scale for pain and the American Orthopaedic Foot and Ankle Society hindfoot score were used to assess functional outcome, and radiographs and computed tomography scans were used to determine the presence of fusion. All patients improved clinically from pre- to postoperatively in regard to the mean pain visual analog scale score (from 7.5 to 2.0) and American Orthopaedic Foot and Ankle Society hindfoot score (from 29 to 65 points, of an 86-point maximum for fused joints). Radiologically, no loss in the reduction or misalignment of the hindfoot was detected, and all cases fused solid. One patient (16.67%) required hardware removal. The fixation construct provided good clinical and radiologic outcomes, and we recommend it as an alternative to structural allografts or metallic bone grafts for revision ankle surgery with severe bone loss.

Reconstruction of massive uncontained acetabular defects using allograft with cage or ring reinforcement

We retrospectively reviewed 44 consecutive patients (50 hips) who underwent acetabular re-revision after a failed previous revision that had been performed using structural or morcellised allograft bone, with a cage or ring for uncontained defects. Of the 50 previous revisions, 41 cages and nine rings were used with allografts for 14 minor-column and 36 major-column defects. We routinely assessed the size of the acetabular bone defect at the time of revision and re-revision surgery. This allowed us to assess whether host bone stock was restored. We also assessed the outcome of re-revision surgery in these circumstances by means of radiological characteristics, rates of failure and modes of failure. We subsequently investigated the factors that may affect the potential for the restoration of bone stock and the durability of the re-revision reconstruction using multivariate analysis. At the time of re-revision, there were ten host acetabula with no significant defects, 14 with contained defects, nine with minor-column, seven with major-column defects and ten with pelvic discontinuity. When bone defects at re-revision were compared with those at the previous revision, there was restoration of bone stock in 31 hips, deterioration of bone stock in nine and remained unchanged in ten. This was a significant improvement (p < 0.001). Morselised allografting at the index revision was not associated with the restoration of bone stock. In 17 hips (34%), re-revision was possible using a simple acetabular component without allograft, augments, rings or cages. There were 47 patients with a mean follow-up of 70 months (6 to 146) available for survival analysis. Within this group, the successful cases had a minimum follow-up of two years after re-revision. There were 22 clinical or radiological failures (46.7%), 18 of which were due to aseptic loosening. The five and ten year Kaplan-Meier survival rate was 75% (95% CI, 60 to 86) and 56% (95% CI, 40 to 70) respectively with aseptic loosening as the endpoint. The rate of aseptic loosening was higher for hips with pelvic discontinuity (p = 0.049) and less when the allograft had been in place for longer periods (p = 0.040). The use of a cage or ring over structural allograft bone for massive uncontained defects in acetabular revision can restore host bone stock and facilitate subsequent re-revision surgery to a certain extent.

Outcomes of Schatzker II Tibial Plateau Fracture Open Reduction Internal Fixation Using Structural Bone Allograft

The purpose of this study is to report the rate of anatomic reduction, articular subsidence, and clinical outcomes for Schatzker II tibial plateau fractures treated with structural bone allografts. This is a retrospective case series. Academic Level I Trauma Center. A trauma registry was used to identify 77 Schatzker II tibial plateau fractures. Schatzker II tibial plateau fracture open reduction internal fixation and structural bone graft using either Plexur P (N = 29) or fibular allograft (N = 48). The primary outcome was articular subsidence. Secondary outcomes included fracture malreduction and clinical outcomes including the Knee Outcome Survey Activities of Daily Living Scale, the Lower Extremity Functional Scale, and the Short Form (SF)-36. No patients experienced subsidence > 2mm. This rate is significantly lower than published rates for autogenous iliac crest (30.3%, P < 0.0001) and calcium phosphate cement (8.7%, P = 0.0099). The rate of fracture malreduction was 11.7% (9/77); only 4 had more than 3 mm of residual incongruity. Average outcome scores were the following: Knee Outcome Survey Activities of Daily Living Scale, 81.7; Lower Extremity Functional Scale, 78.5; SF-36 physical component, 48.3; and SF-36 mental component, 53.1. There was no difference between patients treated with Plexur P or fibula with regard to the primary or secondary outcomes. The use of structural allograft resulted in a high rate of anatomic reduction and negligible rate of articular subsidence and good clinical outcomes in the treatment of this population of Schatzker II tibial plateau fractures. This compares favorably with historical results using nonstructural grafts. Therapeutic level IV. See instructions for authors for a complete description of levels of evidence.

The effect of mesenchymal stem cell sheets on structural allograft healing of critical sized femoral defects in mice

Structural bone allografts are widely used in the clinic to treat critical sized bone defects, despite lacking the osteoinductive characteristics of live autografts. To address this, we generated revitalized structural allografts wrapped with mesenchymal stem/progenitor cell (MSC) sheets, which were produced by expanding primary syngenic bone marrow derived cells on temperature-responsive plates, as a tissue-engineered periosteum. In vitro assays demonstrated maintenance of the MSC phenotype in the sheets, suggesting that short-term culturing of MSC sheets is not detrimental. To test their efficacy in vivo, allografts wrapped with MSC sheets were transplanted into 4-mm murine femoral defects and compared to allografts with direct seeding of MSCs and allografts without cells. Evaluations consisted of X-ray plain radiography, 3D microCT, histology, and biomechanical testing at 4- and 6-weeks post-surgery. Our findings demonstrate that MSC sheets induce prolonged cartilage formation at the graft-host junction and enhanced bone callus formation, as well as graft-host osteointegration. Moreover, a large periosteal callus was observed spanning the allografts with MSC sheets, which partially mimics live autograft healing. Finally, biomechanical testing showed a significant increase in the structural and functional properties of MSC sheet grafted femurs. Taken together, MSC sheets exhibit enhanced osteogenicity during critical sized bone defect repair, demonstrating the feasibility of this tissue engineering solution for massive allograft healing.

Porous metal augments

The conventional method for reconstructing acetabular bone loss at revision surgery includes using structural bone allograft. The disadvantages of this technique promoted the advent of metallic but biocompatible porous implants to fill bone defects enhancing initial and long-term stability of the acetabular component. This paper presents the indications, surgical technique and the outcome of using porous metal acetabular augments for reconstructing acetabular defects.

Three-Dimensional Virtual Bone Bank System Workflow for Structural Bone Allograft Selection: A Technical Report

Structural bone allograft has been used in bone defect reconstruction during the last fifty years with acceptable results. However, allograft selection methods were based on 2-dimensional templates using X-rays. Thanks to preoperative planning platforms, three-dimensional (3D) CT-derived bone models were used to define size and shape comparison between host and donor. The purpose of this study was to describe the workflow of this virtual technique in order to explain how to choose the best allograft using a virtual bone bank system. We measured all bones in a 3D virtual environment determining the best match. The use of a virtual bone bank system has allowed optimizing the allograft selection in a bone bank, providing more information to the surgeons before surgery. In conclusion, 3D preoperative planning in a virtual environment for allograft selection is an important and helpful tool in order to achieve a good match between host and donor.

Comparison of Structural Bone Autografts and Allografts in Pediatric Foot Surgery

Autogenous bone has been the gold standard as the source for structural bone-graft material due to its osteogenic potential, nonimmunogenicity, and efficiency of incorporation. However, donor-site morbidity can lead to significant problems. Allograft bone is readily available and obviates the risks associated with bone-graft harvesting. However, its use raises concerns of disease transmission, infection, slower incorporation, and immunologic reaction. Despite these concerns, allograft use has become widespread. The few comparative studies of the 2 graft types used in spine and tumor surgery are promising. We sought to compare the speed and completeness of graft incorporation and the relative safety of autograft and allograft structural bone in pediatric foot surgery. A retrospective analysis was performed on 161 children who underwent foot surgery requiring 182 allografts and 63 autografts from 1982 to 1994. Follow-up ranged from 2 to 146 months (mean=51.4). Graft-host union, defined as radiographic evidence of healing with a clinical lack of tenderness at graft insertion site, occurred within 12 weeks in both groups. Average time to healing in both groups was just over 7 weeks. In the allograft group, there was 1 nonunion, 3 graft displacements due to technical error requiring reoperation, and 1 partial displacement that did not require reoperation. All of these complications can be attributed to technique rather than to graft type. There were no infections or instances of disease transmission. There were no reported complications in the autograft group. Small, structural bone allografts provide a safe, efficient, and cost-effective alternative to iliac crest bone autograft in pediatric foot surgery. Level III, therapeutic study, retrospective comparative study.

Treatment using structural bone allografts in long bone tumour resections. A review of 37 cases

Structural bone allografts have become an alternative in the treatment of limb bone tumours with a chance of limb-saving surgery. We present an observational retrospective study on the use of structural bone allografts in bone tumours of the long bones in our hospital between January 1993 and January 2010, with a sample of 37 patients subjected to this surgical technique. After obtaining clinical information from our sample we applied the Mankin and EVACOM HUVA functional scales with excellent, very good and good results in 84%, and with the radiological information we applied the International Symposium on Limb Salvage (ISOLS) osseointegration scale, with 95.6% of excellent results after 24 months. These results demonstrate that structural bone allografts are a valid and reproducible technique in patients with destructive long bone tumours.

Surgical revascularization induces angiogenesis in orthotopic bone allograft.

Remodeling of structural bone allografts relies on adequate revascularization, which can theoretically be induced by surgical revascularization. We developed a new orthotopic animal model to determine the technical feasibility of axial arteriovenous bundle implantation and resultant angiogenesis. We asked whether arteriovenous bundles implanted in segmental allografts would increase cortical blood flow and angiogenesis compared to nonrevascularized frozen bone allografts and contralateral femoral controls. We performed segmental femoral allotransplantation orthotopically from 10 Brown Norway rats to 20 Lewis rats. Ten rats each received either bone allograft reconstruction alone (Group I) or allograft combined with an intramedullary saphenous arteriovenous flap (Group II). At 16 weeks, we measured cortical blood flow with the hydrogen washout method. We then quantified angiogenesis using capillary density and micro-CT vessel volume measurements. All arteriovenous bundles were patent. Group II had higher mean blood flow (0.12 mL/minute/100 g versus 0.05 mL/minute/100 g), mean capillary density (23.6% versus 2.8%), and micro-CT vessel volume (0.37 mm(3) versus 0.07 mm(3)) than Group I. Revascularized allografts had higher capillary density than untreated contralateral femora, while vessel volume did not differ and blood flow was lower. Axial surgical revascularization in orthotopic allotransplants can achieve strong angiogenesis and increases cortical bone blood flow.

Tratamiento mediante aloinjertos óseos estructurales en resecciones por tumores óseos de huesos largos. Revisión de 37 casos

Structural bone allografts have become an alternative in the treatment of limb bone tumours with a chance of limb-saving surgery. We present an observational retrospective study on the use of structural bone allografts in bone tumours of the long bones in our hospital between January 1993 and January 2010, with a sample of 37 patients subjected to this surgical technique. After obtaining clinical information from our sample we applied the Mankin and EVACOM HUVA functional scales with excellent, very good and good results in 84%, and with the radiological information we applied the ISOLS osseointegration scale, with 95.6% of excellent results after 24 months. These results demonstrate that structural bone allografts are a valid and reproducible technique in patients with destructive long bone tumours.

Sponge swabs increase sensitivity of sterility testing of processed bone and tendon allografts

Sterility testing is the final, and critical, step in quality control of tissue banking. It informs the decision whether to release the tissue allografts for clinical use, or not. The most common method for sterility testing of structural bone and tendon allografts is to swab using cotton tip streaks. This method provides low recovery efficiency; and therefore may pass allografts with low bioburden, providing false negatives. Our pilot data revealed organism recovery efficiencies of 60, 30 and 100% from cotton swab, membrane filtration and sponge swaps, respectively. Our aim was to develop a high sensitivity sterility test for structural bone and tendon allografts using a sponge sampling method. Eighty-one bone and tendon allograft samples were inoculated with organism suspensions (10(2) or less organisms per 0.1 mL) of Clostridium sporogenes, Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, Bacillus subtilis, Aspergillus niger, Staphylococcus epidermidis and Micrococcus spp. Nasco sponges (4 × 8 cm) were used to aseptically sample the whole surface of allograft samples. The sponges were cut in half and cultured in either tryptone soya or fluid thioglycollate broths for 14 days. Positive culture samples were further examined for microbial morphology. The results showed that the sensitivity of the method, and negative predictive value, is 100% for all inoculated organisms incubated with thioglycollate. We conclude that this sponge sampling method should be applied as the standard for sterility testing of structural bone and tendon allografts.

Total Knee Arthroplasty for Post-Traumatic Proximal Tibial Bone Defect: Three Cases Report

Bone stock deficiency in primary as well as in revision total knee arthroplasty (TKA) represents a difficult problem to surgeon with regard to maintaining proper alignment of the implant components and in establishing a stable bone-implant interface. Different surgical procedures are available in these situations, for instances the use of bone cement, prosthetic augments, custom implant, and wire mesh with morsellized bone grafting and structural bone allograft. Structural allograft offers a numerous advantages as easy remodeling and felling cavitary or segmental defects, excellent biocompatibility, bone stock restoration and potential for ligamentous reattachment. In this article we report a short term result of three cases affected by severe segmental medial post/traumatic tibial plateau defect in arthritic knee, for which massive structural allograft reconstruction and primary total knee replacement were carried. The heights of the bone defect were between 27-33 mm and with moderate medio-lateral knee instability. Pre-operative AKS score in three cases was 30, 34 and 51 points consecutively and improved at the last follow-up to 83, 78 and 85 consecutively. No acute or chronic complication was observed. Last radiological exam referred no signs of prosthetic loosening, no secondary resorption of bone graft and well integrated graft to host bone. These results achieved in our similar three cases have confirmed that the structural bone allograft is a successful biological material to restore hemi-condylar segmental tibial bone defect when total knee replacement is indicated.

Elastomeric Osteoconductive Synthetic Scaffolds with Acquired Osteoinductivity Expedite the Repair of Critical Femoral Defects in Rats

Regenerative medicine aspires to reduce reliance on or overcome limitations associated with donor tissue-mediated repair. Structural bone allografts are commonly used in orthopedic surgery, with a high percentage of graft failure due to poor tissue integration. This problem is aggravated among elderly, those suffering from metabolic conditions, or those undergoing cancer therapies that compromise graft healing. Toward this end, we developed a synthetic graft named FlexBone, in which nanocrystalline hydroxyapatite (50 wt%) was structurally integrated with crosslinked poly(hydroxyethyl methacrylate) hydrogel, which provides dimensional stability and elasticity. It recapitulates the essential role of nanocrystalline hydroxyapatite in defining the osteoconductivity and biochemical microenvironment of bone because of its affinity for biomolecules. Here, we demonstrate that FlexBone effectively absorbed endogenously secreted signaling molecules associated with the inflammation/graft healing cascade upon being press-fit into a 5-mm rat femoral segmental defect. Further, when preabsorbed with a single dose of 400 ng recombinant human (rh) bone morphogenetic protein-2/7 heterodimer, it enabled the functional repair of the critical-sized defect by 8-12 weeks. FlexBone was stably encapsulated by the bridging bony callus and the FlexBone-callus interface was continuously remodeled. In summary, FlexBone combines the dimensional stability and osteoconductivity of structural bone allografts with desirable surgical compressibility and acquired osteoinductivity in an easy-to-fabricate and scalable synthetic biomaterial.

In vitro biomechanics of an expandable vertebral body replacement with self-adjusting end plates

Background context Unstable burst fractures of the thoracolumbar spine may be treated surgically. Vertebral body replacements (VBRs) give anterior column support and, when used with supplemental fixation, impart rigidity to the injured segments. Although some VBRs are expandable, device congruity to the vertebral end plates is imprecise and may lead to stress risers and device subsidence. Purpose The objective of this study was to compare the rigidity of a VBR that self-adjusts to the adjacent vertebral end plates versus structural bone allograft and with an unsupported anterior column in a traumatic burst fracture reconstruction model. Study design Biomechanical flexibility testing with rod strain measurement. Patient sample Twelve T11–L3 human spine segments. Outcome measures Range of motion, neutral zone, and posterior fixation rod stress (moments). Methods Flexibility testing was performed to±6 Nm in flexion-extension, lateral bending, and axial rotation on 12 intact human T11–L3 specimens. Burst fractures were created in L1, and flexibility testing was repeated in three additional states: subtotal corpectomy with posterior instrumentation (PI) only from T12 to L2, reconstruction with a femoral strut allograft and PI, and reconstruction with a VBR (with self-adjusting end plates) and PI. The PI consisted of pedicle screws and strain gage instrumented rods that were calibrated to measure rod stress via flexion-extension bending moments. Results There was no statistical difference in range of motion or neutral zone between the strut graft and VBR constructs, which both had less motion than the PI-only construct in flexion/extension and torsion and were both less than the intact values in flexion/extension and lateral bending (p<.05). Posterior rod moments were significantly greater for the PI-only construct in flexion/extension relative to the strut graft and VBR states (p=.03). Conclusions This study, which simulated the immediate postoperative state, suggests that a VBR with self-adjusting end plate components has rigidity similar to the standard strut graft when combined with PI. Posterior rod stress was not significantly increased with this type of VBR compared with the strut graft reconstruction. The benefits of burst fracture stabilization using a self-adjusting VBR ultimately will not be known until long-term clinical studies are performed.

Femoral Head Allograft for Tibiotalocalcaneal Fusion Using a Cup and Cone Reamer Technique

End-stage degenerative joint disease of the hindfoot with large structural bone deficits is a complex problem encountered by the foot and ankle surgeon. Surgical treatment of this condition often requires tibiotalocalcaneal fusion with use of structural allograft bone. In this article, we describe a technique in which an acetabular reamer is used to create a concave surface for placement of a convex femoral head allograft. This “cup-and-cone” technique provides a congruent area for placement of the allograft, thereby increasing stability of the graft during preparation and placement of an intramedullary nail, while maximizing bone-to-bone surface contact at the arthrodesis site.

A Novel Strategy Incorporated the Power of Mesenchymal Stem Cells to Allografts for Segmental Bone Tissue Engineering.

Mesenchymal stem cells (MSCs) hold great promise for bone regeneration. However, the power of mesenchymal stem cells has not been applied to structural bone allografts in clinical practice. This study designed a new strategy to enhance the efficiency of allografts for segmental bone regeneration. Isolated MSCs were cultured to form a cell sheet. The MSC sheet was then wrapped onto structural allografts. The assembled structures were cultured in vitro to evaluate the differentiation potential of MSC sheet. The assembled structures were implanted subcutaneously into nude mice as well as into the segmental radius defect of rabbits to investigate the efficiency of MSC sheets to repopulate allografts for bone repair. MSC sheets, upon assembling on bone grafts, showed similar differentiation properties to the in situ periosteum in vitro. After implantation the MSC sheets accelerated the repopulation of bone grafts in nude mice. Moreover, MSC sheets induced thicker cortical bone formation and more efficient graft-to-bone end fusion at the segmental bone defects in rabbits. This study thus presented a novel, more efficient, and practical strategy for large weight-bearing bone reconstruction by using MSC sheets to deliver large number of MSCs to repopulate the bone allografts.

Autologous mesenchymal stem cells loaded in Gelfoam® for structural bone allograft healing in rabbits

This study was designed to evaluate the effect of autologous bone marrow mesenchymal stem cells (MSCs) seeded into Gelfoam® on structural bone allograft healing. Thirty New Zealand white rabbits were divided into two groups. Segmental bone defect was created on diaphysis of the femur, and the defect was reconstructed with structural bone allograft. In experimental group, structural allograft was wrapped around by Gelfoam® containing autologous MSCs, whereas cells were not included in control group. At 4, 8, 12 weeks, the femur of rabbits underwent radiographic and histologic evaluation for bony union. Bone morphogenic protein-2 (BMP-2), BMP-4, BMP-7, vascular endothelial growth factor (VEGF), and receptor activator of nuclear factor-kappa B ligand (RANKL) were measured within the grafted periosteal tissue. Bony union was not achieved in both groups at 4 and 8 weeks. At 12 weeks, three out of five femurs in experimental group were united, but one out of five in control group was united. Mean Taira scores were significantly different between two groups. The expression of BMP-2 was significantly higher at 4, 8 weeks, the expressions of BMP-4 and BMP-7 were significantly higher at 8 and 12 weeks, and the expression of VEGF and RANKL were significantly higher at all time points in experimental group. Incorporation of the structural bone allograft could be enhanced if allograft is covered with Gelfoam® containing autologous MSCs. MSCs have influence on not only bone formation, but neo-angiogenesis, and bone resorption.

Variability in Tissue Bank Practices Regarding Donor and Tissue Screening of Structural Allograft Bone

A standardized questionnaire was directed to medical directors of US structural allograft bone providers regarding their practices in screening potential donors and allograft bone itself for parameters potentially affecting mechanical strength. To determine the uniformity of practices within the US allograft bone industry regarding parameters related to structural allograft bone mechanical strength. Despite oversight with respect to disease transmission and contamination, few guidelines exist regarding donor eligibility and bone itself for issues potentially affecting the mechanical integrity of structural allograft bone. A survey regarding donor and tissue screening practices impacting mechanical strength of structural allograft bone was administered to medical directors of American Association of Tissue Banks-accredited structural allograft bone providers. Results are reported as the percentage of all tissue banks using a given donor or tissue screening method and the percentage of the total US supply of structural allograft bone affected. Eighty-one percent (14 of 16) of bone-processing banks completed the survey, accounting for 98% of the US supply of structural allograft bone. Approximately 76% (18,712 of 24,671) of all tissue donors are used as a source of structural bone allograft. Thirty-nine percent (6 of 14) of tissue banks have no upper age limit or accept structural allograft bone donors up to age 80. Fifty percent (7 of 14) of banks exclude donors with a diagnosis of osteoporosis. Sixty-four percent (9 of 14) of banks require a minimum cortical dimension of structural bone allograft, representing 81% (15,110 of 18,712) of the US supply. No tissue bank performs dual energy x-ray absorptiometry scans of potential bone donors. Substantial variability exists in screening practices of US tissue banks regarding mechanical strength of structural allograft bone. Reported variations may reflect the lack of regulatory standards regarding these issues. Further data regarding these variables' impacts on allograft strength and clinical outcomes would be helpful in developing appropriate standards.