Comparative study of the osseous healing process following three different techniques of bone augmentation in the mandible: an experimental study

Technical refinements of the scapular tip-free flap for mandibular reconstruction

BACKGROUND

The use of scapular tip chimeric free flaps (STFFs) for reconstructing mandibular defects has recently become popular, but its utility relative to other bone-containing free flaps remains debatable. The aim of the report is to describe how technical modification of STFF impacted in its use for mandibular reconstruction also commenting results obtained in a unicentric series of patients.

PATIENTS AND METHODS

Patients undergoing mandibular reconstruction using an STFF from January 1, 2014 to June 1, 2022 were retrospectively enrolled in this report. We collected data on chimeric flap type, bone management, vascular pedicles, and the final outcomes. In total, 31 patients (13 men and 18 women) with a mean age of 68 years were enrolled. According to the classification system of Urken, 15 patients had body defects, while 7 had ramus defects, another 7 had symphysis defects, and 2 had both ramus and bodily defects. STFF was always harvested working in two equips simultaneously, in supine position. Dissection included preparation of chimeric components of the flap as latissimus dorsi, serratus and scapular tip. After pedicle dissection scapular bone was cut basing on reconstructive needing with a rectangular (stick) shape including the border of the scapula. In cases of longer bone harvesting, circumflex pedicle was also included to perfuse the upper portion of the scapular border. In five cases, the STFF was harvested with only the scapular angle component, and was thus a composite osteomuscular flap; for the remaining 26 cases, a chimeric STFF was used. Circumflex pedicle was included for eight patients. Six of the seven patients with symphyseal defects underwent a single osteotomy.

RESULTS

The average length of the harvested was 69.92 mm (maximum length = 104 mm). The average height of transplanted bone was 26.78 mm (maximum height = 44.2 mm). Mouth-opening was normal in 25 patients, limited in 6 patients, and severely impaired in no patients. The cosmetic results were rated as excellent by 20 patients, good by 8 patients, and poor by 3 patients.

CONCLUSION

The STFF is an excellent option for mandibular reconstruction when other flaps are not available and for patients in poor general condition. Technical innovations here presented made possible to harvest long bone segments with accurate shape thanks to osteotomies if needed and with adequate soft tissues components of the chimeric flap, ensuring satisfactory functional and cosmetic results.

Experimental Model for the Study of Reparative Bone Regeneration in the Reconstruction of the Lower Jaw

An experimental in vivo model has been developed on the rabbit mandible to study reparative regeneration of alveolar bone after intercortical split osteotomy and the role of the periosteum in the process of reparative osteogenesis. The peculiarity of this model is fixation of the periosteum over the reconstruction zone, which allows preserving the bone block displaced during surgery and leads to the formation of an organotypic structure of the regenerate with cortical and spongy bone.

Evaluation of the Proximal Tibia as a Donor Site of Cancellous Bone for Intraoral Grafting Procedures-A Retrospective Study

Background: Autogenous bone grafts remain the “gold standard” in maxillofacial reconstructive procedures. The objective of this study was to evaluate the proximal tibia as a donor site of cancellous bone for bone grafting procedures of the mandible on the basis of intraoperative parameters and clinical observations. Methods: The study was based on a medical record search of 40 patients who underwent surgical procedures because of benign pathological lesions of the jaws resulting in 3-wall bone defects of the mandible and qualified for surgical removal of the lesion with simultaneous bone grafting of the defect with autogenous cancellous bone harvested from the proximal tibia. Results: The use of the proximal tibia for bone grafting procedures enables large amounts of cancellous bone (15.09 cc in average) to be obtained. The procedure is characterized by a low risk of early and late complications, which include excessive bleeding, wound infection, lengthy healing time, scars, a loss of sensation around the scars, aching, a dip in bone, swelling and tenderness. Conclusions: The ability to obtain large amounts of cancellous bone and a low risk of intra- and postoperative complications make the proximal tibia an attractive donor site for the bone grafting procedures in maxillofacial surgery.

Histologic and histomorphometric evaluation of the bone regeneration following cortical bone repositioning in a rabbit mandible

BACKGROUND

Although bone graft (BG) is the gold standard for bone augmentation, its use is hampered by donor site morbidity and limited quantity.

PURPOSE

To evaluate the capabilities of bone formation by cortical bone repositioning (CBR) as the healing response following grafting of autogenous bone block without filling biomaterial at the gap between gap and recipient.

MATERIALS AND METHODS

Twelve Japanese White rabbits were divided into three groups (postoperative 2, 5, and 8 weeks). A cortical block was freed from the mandibular body, half of the block was positioned and fixed overlapped the original bone surface beside the defect and the other half remained only elevated above the defect. Three areas were decided for the evaluation; BG, CBR, and defect (D) area. Areas were evaluated by micro-CT, histology, and histomorphometric analysis.

RESULTS

There is no statistical difference between BG and CBR by evaluating distance and area in histomorphometrical analysis (P < .05). D area showed statistical decrease compared with BG and CBR at week 2. Histologically, new bone was evident at week 2, mature bone was observed in all three areas at week 8, D area disappeared and fused completely with the elevated bone block.

CONCLUSION

CBR has potential for bone augmentation as BG induced from its own regenerative ability of healing process.

Hyaluronic Acid/Bone Substitute Complex Implanted on Chick Embryo Chorioallantoic Membrane Induces Osteoblastic Differentiation and Angiogenesis, but not Inflammation

Microscopic and molecular events related to alveolar ridge augmentation are less known because of the lack of experimental models and limited molecular markers used to evaluate this process. We propose here the chick embryo chorioallantoic membrane (CAM) as an in vivo model to study the interaction between CAM and bone substitutes (B) combined with hyaluronic acid (BH), saline solution (BHS and BS, respectively), or both, aiming to point out the microscopic and molecular events assessed by Runt-related transcription factor 2 (RUNX 2), osteonectin (SPARC), and Bone Morphogenic Protein 4 (BMP4). The BH complex induced osteoprogenitor and osteoblastic differentiation of CAM mesenchymal cells, certified by the RUNX2 +, BMP4 +, and SPARC + phenotypes capable of bone matrix synthesis and mineralization. A strong angiogenic response without inflammation was detected on microscopic specimens of the BH combination compared with an inflammatory induced angiogenesis for the BS and BHS combinations. A multilayered organization of the BH complex grafted on CAM was detected with a differential expression of RUNX2, BMP4, and SPARC. The BH complex induced CAM mesenchymal cells differentiation through osteoblastic lineage with a sustained angiogenic response not related with inflammation. Thus, bone granules resuspended in hyaluronic acid seem to be the best combination for a proper non-inflammatory response in alveolar ridge augmentation. The CAM model allows us to assess the early events of the bone substitutes–mesenchymal cells interaction related to osteoblastic differentiation, an important step in alveolar ridge augmentation.