(38) Application of Tissue Engineering During Intraoral Inverted L Osteotomy: A Description of Technique and Case Series

Abstract:

Background: While the bilateral sagittal split osteotomy (BSSO) is the most commonly employed procedure to correct the mandibular skeletal deformity, MacIntosh reported as high as 85% immediate postoperative neurosensory deficit (NSD) (1) and others have reported postoperative incidence varying between 5% to 70% (2-4). In 1927, the extraoral inverted L osteotomy (ILO) technique introduced by Wassmund showed low risk of inferior alveolar nerve injury. But it failed to gain traction due to the requisite of bilateral neck incisions resulting in some poor cosmetic outcomes, wired intermaxillary fixation and trade off of NSD risk with the potential facial nerve injury (5). Additionally, as the indication for the ILO technique was reserved for large mandibular advancements, consequential large bony gap between the proximal and distal segments were often grafted with iliac crest graft or other autologous bone to facilitate favorable bony union. But this requires a second surgical site, increasing patient morbidity and increases the surgical operating time (6-8). Over the years, the inverted L osteotomy has become refined to intraoral only technique with improvements in fixation techniques, virtual surgical planning (VSP) and custom designed hardware (9-10). Since 2002, the concept of tissue engineering by increasing osteogenic signals with the use of commercially available human recombinant bone morphogenic protein (rhBMP) has changed the paradigm in how the maxillofacial bony defects are augmented and grafted. The aim of this report is to present the methodology of our institution’s ILO technique and the details of the cases rendered by the Oral and Maxillofacial Residency Program of the Naval Medical Center San Diego.
Materials and

Methods: The Clinical Investigation Department at NMCSD approved this investigation as a retrospective observational study. In this case series, seven adult patients underwent orthognathic surgery with an bilateral intraoral inverted L osteotomy with application of rhBMP-2 into the bony defect site. The variability of the grafting method, in which type of osteoconductive matrix was utilized between the two segments, is listed in Table-1. All of the cases were planned with the assistance of VSP. The three-dimensional imaging was completed at preoperative period (T0) and at minimum 6 months post-surgical period (T1). All of the patients’ grafting outcomes were analyzed with three-dimensional imaging from preoperative and postoperative period using volumetric analysis. As a secondary outcome, the authors looked at average surgical time of Inverted L osteotomy compared to traditional orthognathic that employed BSSO, listed complications if any, and patient-reported satisfaction were also documented.

Results: The volumetric analysis demonstrated bone formation and sustained stability in all of the cases that utilized BMP, with improved structural integrity compared to conventional techniques. Patients exhibited favorable functional and aesthetic outcomes with minimal complications to include 0% neurosensory deficit rate

Conclusion: The ILO technique has become a versatile mandibular surgical technique at our institution. With the utilization of virtual surgical planning and additional use of rhBMP, we are able to achieve speedy operating time with a single surgical team. The combination of intraoral ILO and rhBMP enhances mandibular reconstruction by promoting bone regeneration and maintaining postoperative bony volume without requiring a second-site surgery. This technique offers a promising approach for improving clinical outcomes in mandibular surgery. A large, prospective randomized clinical trial is needed to validate potential non-inferiority of our initial findings compared to cases that utilize secondary surgical site.

Reference:
Macintosh RB: Experience with the sagittal osteotomy of the mandibular ramus: A 13 year review. J Maxillofac Surg 9:151, 1981
Karas ND, Boyd SB, Sitm DP: Recovery of neurosensory function following orthognathic surgery. J Oral Maxillofac Surg 48124, 1990
Details of the treatment rendered