Heterotopic neo-osteogenesis from vascularized periosteum and bone grafts

Reconstruction of mandibular vertical defects for dental implants with autogenous bone block grafts using a tunnel approach: clinical study of 50 cases

The objective of this study was to evaluate the outcomes of mandibular vertical defect reconstruction with autologous bone and the use of a sub-periosteal tunnel approach in preparation for dental implant insertion. Forty-three consecutive patients with an atrophic posterior mandible were reconstructed using this method. Two thin laminae of cortical bone, obtained by splitting blocks harvested from the retromolar area, were fixed in a box-like framework containing cancellous and particulate bone. The goal was to achieve an alveolar ridge width of ≥5.5mm and an effective bone height (EBH) of ≥10.5mm for dental implant insertion (≥3.4mm diameter, ≥9.5mm length). Fifty reconstruction procedures were performed. The mean EBH was 7.1±1.3mm pre-treatment and 12.3±1.1mm post-treatment (mean increase 5.2±1.4mm). Complete graft loss was recorded in two cases; the remaining complications were minor. After a mean consolidation period of 3.5 months, 96 dental implants were placed. No failure of osseointegration was observed at follow-up (mean 32.9 months). The average bone height reduction was 0.9mm (graft vertical resorption 17.4%). Reconstruction of posterior mandibular vertical defects using two autogenous cortical bone blocks with particulate bone between them, combined with a tunnelling technique, provided good healing with no wound dehiscence and minimum resorption of the grafted bone, favouring a substantial vertical bone gain.

A review of mouse critical size defect models in weight bearing bones

Current and future advances in orthopedic treatment are aimed at altering biological interactions to enhance bone healing. Currently, several clinical scenarios exist for which there is no definitive treatment, specifically segmental bone loss from high-energy trauma or surgical resection - and it is here that many are aiming to find effective solutions. To test experimental interventions and better understand bone healing, researchers employ critical size defect (CSD) models in animal studies. Here, an overview of CSDs is given that includes the specifications of varying models, a discussion of current scaffold and bone graft designs, and current outcome measures used to determine the extent of bone healing. Many promising graft designs have been discovered along with promising adjunctive treatments, yet a graft that offers biomechanical support while allowing for neovascularization with eventual complete resorption and remodeling remains to be developed. An overview of this important topic is needed to highlight current advances and provide a clear understanding of the ultimate goal in CSD research--develop a graft for clinical use that effectively treats the orthopedic conundrum of segmental bone loss.

Immunohistochemical and molecular characterization of the human periosteum

Purpose. The aim of the present study was to characterize the cell of the human periosteum using immunohistological and molecular methods. Methods. Phenotypic properties and the distribution of the cells within the different layers were investigated with immunohistochemical staining techniques and RT-PCR, focussing on markers for stromal stem cells, osteoblasts, osteoclasts and immune cells. Results. Immunohistochemical results revealed that all stained cells were located in the cambium layer and that most cells were positive for vimentin. The majority of cells consisted of stromal stem cells and osteoblastic precursor cells. The density increased towards the deeper layers of the cambium. In addition, cells positive for markers of the osteoblast, chondrocyte, and osteoclast lineages were found. Interestingly, there were MHC class II-expressing immune cells suggesting the presence of dendritic cells. Using lineage-specific primer pairs RT-PCR confirmed the immunofluorescence microscopy results, supporting that human periosteum serves as a reservoir of stromal stem cells, as well as cells of the osteoblastic, and the chondroblastic lineage, osteoclasts, and dendritic cells. Conclusion. Our work elucidates the role of periosteum as a source of cells with a high regenerative capacity. Undifferentiated stromal stem cells as well as osteoblastic precursor cells are dominating in the cambium layer. A new outlook is given towards an immune response coming from the periosteum as MHC II positive immune cells were detected.

Traumatic diaphyseal bone defects in children

Traumatic bone defects (BD) are rare in children. There are no pediatric series in the literature on this topic. The aim of this first pediatric series was to determine the epidemiological characteristics and evaluate the results of different treatments in this entity.

MATERIAL AND METHODS

This retrospective multicenter study evaluated diaphyseal bone defects in cases in which bone reconstruction was performed. BD was either initial and associated with trauma or secondary, resulting from infected non-union.

RESULTS

The series included 27 patients (17 boys and 10 girls), mean age 11.4 years old (3-16) (20 traffic accidents). At the outset of all patients' history was an open fracture (one stage 1, seven stage 2, 11 stage 3A and seven stage 3B, 1 NR). BD involved 13 tibias, 9 femurs, three humerus, one radius and one ulna. Bone defects were initial in 20 cases and secondary in seven cases. They were less than 2 cm in two cases, between 2 and 5 cm in 9 cases, between 5 and 10 cm in 10 cases and more than 10 cm in six cases. Treatment of BD was immediate in one case and delayed in 26 cases. Techniques used included: induced membrane in 10 cases, bone transport in seven cases, bone autograft in eight cases, vascularized fibular transfer in one case, no bone reconstruction in one case. Union was obtained in 27 patients. Union was obtained within a mean 12.3 months BD (3-62). Fifteen patients presented with sequellae.

DISCUSSION

Traumatic bone defects have a better prognosis in children than in adults. The thicker, more active and richly vascularized periosteum in children is an important prognostic factor. Treatment of BD requires good initial bone stabilization. Reconstruction depends on the integrity of the periosteum. In case of an intact periosteum, bone reconstruction does not seem necessary in young children. If one part of the periosteum is intact, a simple autograft seems sufficient even with extensive bone defects. In the absence of the periosteum or especially in case of infection, the induced membrane technique seems preferable, with bone transport or a vascularized bone transfer.

LEVEL OF EVIDENCE

IV: retrospective study.

Vascularized bone grafts for upper limb reconstruction: defects at the distal radius, wrist, and hand

Vascularized bone grafts have been successfully applied for the reconstruction of bone defects at the forearm, distal radius, carpus, and hand. Vascularized bone grafts are most commonly used in revision cases in which other approaches have failed. Vascularized bone grafts can be obtained from a variety of donor sites, including the fibula, the iliac crest, the distal radius (corticocancellous segments and vascularized periosteum), the metacarpals and metatarsals, and the medial femoral condyle (corticoperiosteal flaps). Their vascularity is preserved as either pedicled autografts or free flaps to carry the optimum biological potential to enhance union. The grafts can also be transferred as composite tissue flaps to reconstruct compound tissue defects. Selection of the most appropriate donor flap site is multifactorial. Considerations include size matching between donor and defect, the structural characteristics of the graft, the mechanical demands of the defect, proximity to the donor area, the need for an anastomosis, the duration of the procedure, and the donor site morbidity. This article focuses on defects of the distal radius, the wrist, and the hand.

Donor sites for pedicled skeletal grafts of the hand, wrist, and forearm

Pedicled bone and periosteal grafts provide successful reconstruction of skeletal problems of the distal radius, wrist, and hand. The purpose of this study was to evaluate the available alternatives and to propose the most suitable skeletal grafts for the reconstruction of the distal radius, and the carpal and hand bones. The alternative donor sites (dorsal and palmar distal radius, and metacarpals), their pedicles, and the potential coverage area in relation to specific wrist and hand pathology were determined in the cadaveric dissections. In the clinical setting, 75 pedicled grafts were used for the treatment of scaphoid nonunions (62 cases), lunate necrosis (8 cases), reconstruction of the metacarpal defects (2 cases), and wrist fusions (3 cases). All alternatives have the advantage of a single approach that may be performed under tourniquet control, from the same team. Among the available alternatives, surgeon's familiarity plays the most important role for the final selection of the graft.

The use of a vascularised periosteal patch onlay graft in the management of nonunion of the proximal scaphoid

We describe the use of a vascularised periosteal patch onlay graft based on the 1,2 intercompartmental supraretinacular artery in the management of 11 patients (ten men, one woman) with chronic nonunion involving the proximal third of the scaphoid. The mean age of the patients was 31 years (21 to 45) with the dominant hand affected in eight. Six of the patients were smokers and three had undergone previous surgery to the scaphoid. All of the proximal fragments were avascular. The presence of union was assessed using longitudinal axis CT.

Only three patients progressed to union of the scaphoid and four required a salvage operation for a symptomatic nonunion. The remaining four patients with a persistent nonunion are asymptomatic with low pain scores, good grip strength and a functional range of wrist movement.

Although this technique has potential technical advantages over vascularised pedicled bone grafting, the rate of union has been disappointing and we do not recommend it as a method of treatment.

Vascularised bone grafts for the management of non-union

Non-union of the long bones may have severe consequences, particularly when combined with other post-traumatic sequelae, such as tendon adhesions, reflex sympathetic dystrophy and infection, among others. In these cases, it is important to treat the delayed union or non-union first or at the same time with the other problems in order to achieve adequate function. Once the normal bony healing process has been slowed or stopped, it is necessary to provide both stability to the fracture site, as well as a biological stimulus for the fibrocartilagenous callus to finish the healing process. Vascularised grafts, such as the free fibula, offer not only structural support, but also promote bone healing. The later is achieved by trabecular bone formation, as well as vascular sprouting from pedicle vessels.

The healing potential of the periosteum molecular aspects

The presence of pluripotential mesenchymal cells in the under surface of the periosteum in combination with growth factors regularly produced or released after injury, provide this unique tissue with an important role in the healing of bone and cartilage. The periosteum contributes in the secondary callus formation with cells and growth factors and should always be preserved and protected when surgery is performed for the management of a fracture. The current evidence about the cellular interactions, the stimulants and the signalling pathways related to osteogenesis and chondrogenesis is described. An essential knowledge of the basics related to the contribution of the periosteum in the healing of fractures, osteotomies, during the process of distraction osteogenesis and in some degree in the repair of cartilagenous defects, provides the surgeons with a better insight to understand the upcoming "biological" interventions in the management of skeletal injuries.

Guided Bone Regeneration at the Donor Site of Iliac Bone Grafts for Future Use as Autogenous Grafts

BACKGROUND

Autogenous bone grafting is considered the standard in management of bony defects but has some disadvantages, including limited source of graft material, especially in children. This study represents an attempt to regenerate bone at the donor site of iliac bone grafts using the guided bone regeneration principle for future use in multistage bone reconstruction by grafting.

METHODS

Critical size defects were created in 24 iliac bones of 12 skeletally mature New Zealand White rabbits. Defects in group 1 (n = 12) were covered with inverted U-shaped resorbable mesh (space maintainer) and polytetrafluoroethylene membranes underneath the periosteum. In group 2 (n = 6), inverted U-shaped resorbable mesh was used alone (positive control). In group 3 (n = 6), neither resorbable mesh nor polytetrafluoroethylene membranes were used (negative control). An unpaired t test was used for comparison between each two groups.

RESULTS

Plain radiographs and contact microradiographic studies showed that bone regeneration was significantly higher in group 1 and group 2 than in group 3 (p < 0.001). There was no significant difference between group 1 and group 2 regarding density.

CONCLUSIONS

The periosteum acted as an ideal membrane for guided bone regeneration so that the polytetrafluoroethylene membranes could be used only to compensate for the deficient periosteum. Space maintenance was essential for bone regeneration.

Vascularized periosteal flaps of distal forearm and hand

BACKGROUND

Vascularized periosteal flaps (VPFs) are flexible osteogenic flaps, suitable for the reconstruction of small skeletal defects. Pedicled VPFs, harvested near the recipient site, minimize donor-site morbidity and procedure duration. The donor sites and the potential recipient sites for pedicled VPFs of the distal forearm-hand were identified in this study.

METHODS

In 16 fresh cadaver upper extremities, the dimensions and arcs of rotation of the VPF pedicle(s) were studied.

RESULTS

Pedicled VPFs with mean dimensions ranging between 0.5 x 3 cm and 2.5 x 4 cm could cover, after adequate mobilization, the distal half of the forearm, wrist, and hand to the proximal interphalangeal joints.

CONCLUSION

The VPFs identified in this study can be used for the reconstruction of small skeletal defects and for the treatment of osteonecrotic lesions and nonunions of the distal forearm, wrist, and hand. The choice of the most suitable VPF will be based on the anatomic location and the dimensions of the recipient site.

A novel murine segmental femoral graft model

To further understand the cellular and molecular mechanisms underlying cortical bone graft healing, we have developed a novel mouse femur model that permits quantitative and molecular analysis of structural bone graft healing. A 4 mm mid-diaphyseal femoral segment was removed and replaced by either immediate implantation of a fresh autograft, a frozen, genetically identical isograft or a frozen allograft from a different strain of mouse, which was secured with a 22-gauge metal intramedullary pin. Healing was evaluated by radiology, histomorphometry, and in situ hybridization. Autograft repair occurred by endochondral bone formation at the host-graft junction and by intramembranous bone formation along the length of the graft bed at 2 weeks, with maturation and remodeling apparent by 4 weeks. Bone repair in allografts and isografts completely relied on endochondral bone formation at the host-graft cortical junction, with absence of periosteal bone formation along the length of the graft, suggesting that live periosteal cells from the donor tissue are necessary for this response. This small animal model of structural bone grafting can be used to evaluate tissue-engineered allografts and novel bone graft substitutes using quantitative and molecularly defined outcome measures.