Theoretical model for bone graft success.

Theoretical assumptions must correlate with clinical efficacy and good surgical outcomes to be of value to clinicians and patients. This article examines several common assumptions regarding the use of bone marrow aspirate to enhance bone grafting procedures. Contrary to these assumptions, evidence-based research suggests the following: (1) No more than 4 mL of bone marrow should be aspirated from a single donor site. Aspiration of more than that amount does not substantially increase the number of progenitor cells harvested but instead dilutes the concentration of progenitor cells with other nucleated cells from peripheral blood. (2) Bone marrow aspirate should not be concentrated using centrifuge technology. Rather than isolating desired cells, centrifuging concentrates all nucleated cells, increasing the overall metabolic activity to the detriment of the desired cells. (3) Increasing the volume of graft material brought to a graft site has the unwanted effect of increasing the diffusion distance for oxygen and nutrients and may lead to graft necrosis. (4) Histomorphometric analysis is the most effective method of evaluating bone graft outcomes because only such analysis allows for quantification of the percentage of bone and viable cells within a bone core biopsy.

Growth factors and gene expression of stem cells: bone marrow compared with peripheral blood.

PURPOSE: To evaluate and compare the presence of cytokines and growth factors in both bone marrow (BM) and peripheral blood. MATERIAL: Samples of autogenous BM aspirate and peripheral blood (PB) from 7 patients ranging in age from 49 to 80 years were analyzed with real-time polymerase chain reaction technology to identify and compare selected gene expression for specific cytokines and growth factors. The genes selected for analysis included those involved in osteogenesis, hematogenesis, angiogenesis, extracellular matrix molecules, and cell-adhesion molecules. A maximum of 4 cc';s BM aspirate was taken from the anterior iliac crest and 0.5 mL of venous blood was drawn from each of 7 patients. RESULTS: The results of the analysis indicate that both circulating blood and BM aspirate contain large quantities of a host of growth factors and cytokines. More platelet-derived growth factor is expressed in patient blood (PB) than in BM. Vascular endothelial growth factor alpha is expressed slightly greater in BM and vascular endothelial growth factor beta is slightly more prominent in PB. Transforming growth factors (TGFs) TGFA, TGFB1, and TGFB3 were equally expressed in BM and PB, and TGFB2 had a greater expression in PB. Bone morphogenetic proteins (BMPs) 1, 3, 7, 8B, R1A, and PR2 were almost equally expressed in BM and PB. BMPs 4 and 6 were expressed greater in PB. BMP2 was expressed more in BM. Extracellular matrix factors were equally expressed in PB and BM. Mesenchymal stem cell lineage markers varied in PB and BMA, and hematopoietic stem cell lineage markers were expressed more in PB than BM. Gene expression for angiogenic factors were equally expressed in PB and BM. CONCLUSION: In this investigation, specific cytokines and growth factors in BM are compared with those in peripheral blood. Each has similar biologic effects and most expressed equally in BM and PB. However, BMP2 and vascular endothelial growth factor alpha had greater expression in BM.

The inverted periosteal flap: a source of stem cells enhancing bone regeneration.

The periosteum is a necessary component for bone growth, healing, and remodeling. It provides vascularity, osteoblasts, and osteoclasts. It is a regenerative source for stem cells similar to those obtained from bone marrow aspiration. This article describes the inverted periosteal flap technique at an oral bone graft site as a means of enhancing bone regeneration. The technique is recommended when augmenting sites with 3- or 4-wall defects, in conjunction with implant placement or in combination with bone graft surgery.