Analysis of Microvascular Free Flaps for Reconstruction of Advanced Osteoradionecrosis: A Retrospective Cohort Study

Oral Abstract Session 2 general treatment groups: group A: osteotomy with the addition of a bone graft harvested from the preparation of the osteotomy site, and group B: osteotomy without bone graft. Each animal in each group received PRP in one osteotomy site, either with or without the bone graft, determined randomly. Each animal served as its own internal control. After appropriate local and intramuscular anesthesia was established, an ear vessel was cannulated for blood draw, and the sample was used to produce PRP with a centrifuge. Bilateral 1.0 cm by 0.5 cm mandibular inferior border osteotomies were performed on each animal 0.5 cm anterior to the antegonial notch. Osteotomized bone was particulated and re-grafted into the harvest site on both sides for the subjects in the group A (bone graft), and only one side received PRP. Subjects in group B (no bone graft) received PRP in one osteotomy site but not the other. Soft tissues were re-approximated and wounds were closed. Subjects were sacrificed at one, two and three-month intervals for the purposes of evaluating bony healing in the osteotomy sites by histologic and radiographic analysis. Method of Data Analysis: Within animal comparisons were made using a non-parametric paired Wilcoxon signed rank test, and between animal comparisons were made using a non-parametric 2-group Wilcoxon rank sum test. Results: The following measurements were obtained using a four-point ordinal healing scale: Radiographic density, radiographic height, microscopic density, and microscopic cortical thickness. For each pair-wise analysis, results indicated that the addition of PRP to either group A or group B animals did not increase the overall score of any measured parameter (p ⬎ 0.9). It is noted, however, that for the radiographic density analysis, scores for group A with PRP appeared to be increased over group A without PRP (p ⫽ 0.02), and group B animals (p ⫽ 0.001). The radiographic and histologic height analyses showed values for group A to be increased over group B animals (p ⫽ 0.02, p ⫽ 0.007). Although scores increased in the PRP group over time, none of the effects of time on bone healing were significant (p ⫽ 0.2). Conclusion: The results of this study indicate that in the rabbit mandible osteotomy model, PRP alone does not seem to provide the same benefit of healing that a bone graft or bone graft with PRP would provide. PRP should not be expected to regenerate the height or density of bone in a critical size defect that could be provided by bone grafting. Due to the small sample size, the results must be interpreted cautiously, and further investigation may be able to determine differences in the rate of bone healing in bone-grafted sites with and without PRP. 38

References Aghaloo T, Moy P, Freymiller E: Investigation of platelet-rich plasma in rabbit cranial defects: A pilot study. J Oral Maxillofac Surg. 60:1176, 2002 Aghaloo T, Moy P, Freymiller E: Evaluation of PRP in combination with anorganic bovine bone in the rabbit cranium. Int J Oral Maxillofac Implants 19:59, 2004 Funding Source: W. Lorenz Surgical, Jacksonville, FL

Analysis of Microvascular Free Flaps for Reconstruction of Advanced Osteoradionecrosis: A Retrospective Cohort Study David L. Hirsch, DDS, MD, 1849 NW Kearney, Suite 300, Portland, OR 97209 (Bell RB; Homer L; Buehler M; Dierks EJ; Potter BE) Statement of the Problem: Previous studies have suggested that radiation therapy does not impact local complication rates after microvascular free flap (MVFF) reconstruction for head and neck cancer. There is little data, however, indicating whether or not the presence of osteoradionecrosis (ORN) affects treatment outcome. The purpose of this retrospective cohort study is to review the outcome of patients undergoing MVFF reconstruction for ORN and to determine if there is a difference in outcome and/or complications when compared to similarly reconstructed patients who received radiation therapy but did not develop ORN, as well as unradiated controls. Materials and Methods: The records of 305 consecutive patients that underwent MVFF reconstruction for a variety of cancer-related therapies or post-traumatic craniofacial defects from 1994-2004 were reviewed. Of these, all patients that underwent surgery for Marx stage III ORN involving the craniofacial region were identified (mandible ⫽ 19, skull base ⫽ 2). For purposes of comparison, patients that received pre-operative XRT and underwent similar reconstruction but did not have ORN were identified and included in the study group. Similarly matched patients that never received XRT served as controls. Patients were reconstructed with a variety of MVFFs harvested from the fibula (n ⫽ 47), radial forearm (n ⫽ 11), rectus abdominus (n ⫽ 3), latissimus dorsi (n ⫽ 4), and iliac crest (n ⫽ 1). The study cohort was divided according to radiation therapy (XRT) status: Group 1 (ORN), patients that received XRT and developed ORN (n ⫽ 21); Group 2 (no ORN), patients that received XRT but did not develop ORN (n ⫽ 20); and Group 3 (control), patients that never received XRT (n ⫽ 25). The following data were collected: age, gender, diagnosis, recipient site, donor site, hyperbaric oxygen therapy (HBO), flap complications, flap survival, patient survival. Outcome measures were defined as flap survival and complications. AAOMS • 2006

Oral Abstract Session 2 Method of Data Analysis: Descriptive statistics were recorded and an analysis of variance was calculated to evaluate differences between the three groups. The Fisher exact test was used to evaluate whether a complication occurred more frequently in any one particular group. Results: The mean age of the 66 patients included in the study was 57 years (SD ⫽ 15.4) years (M ⫽ 32, F ⫽ 35) and there were no significant demographic differences between the three groups (p ⫽ 0.8528). All patients were successfully reconstructed although 21% required re-operation for various reasons. Overall flap survival was 88% (ORN ⫽ 86%, noORN ⫽ 87%, control ⫽ 90%) and there was no difference between the three groups studied (p ⫽ 1.0). Complications were evenly distributed among the three groups (50% overall) and included skin necrosis (p ⫽ 0.824), wound infection (p ⫽ 0.6374), salivary fistula (p ⫽ 0.1178), and partial flap loss (p ⫽ 1.0). Carotid blowout occurred in 2 patients in the ORN group, however, this was not statistically significant (p ⫽ 0.1844). Fourteen of the 21 patients in the ORN group received preoperative hyperbaric oxygen therapy (HBO), which did not affect flap survival or the complication rate (p ⬍ 0.05). Conclusion: Overall MVFF survival and complication rates among patients with ORN versus control groups are the same in this study cohort. Free tissue transfer is a viable option for advanced ORN of the craniofacial skeleton. References Choi S, Schwartz DL, Farwell DG, Austin-Seymour M, Futran N: Radiation therapy does not impact local complication rates after free flap reconstruction for head and neck cancer. Arch Otolaryngol Head Neck Surg 130:1308, 2004 Ang E, Black C, Irish J, Brown DH, Gullane P, O’Sullivan B, Neligan PC: Reconstructive options in the treatment of osteoradionecrosis of the craniomaxillofacial skeleton. Br J Plast Surg. 56(2):92, 2003

Immediate Provisionalization of Dental Implants Eduardo A.C. Humes, DDS, MPH, 11300 Expo Blvd, Apt 1006, San Antonio, TX 78230 (Edgin WA; Cagna DR; Lang LA; Verrett RG; Pratt TC) Statement of the Problem: There exists a paucity of long-term data evaluating the periodontal and osseous response to immediately restored dental implants in a statistically significant number of patients. In comparison to the conventional protocol (requiring a four to six month healing period prior to placement of provisional crowns) immediate provisionalization of dental implants are, so far, showing similar success rates. Materials and Methods: In this prospective study, twenty healthy patients, each with an anterior edentulous space, were evaluated for placement of a single AAOMS • 2006

osseointegrated implant. The cohort consisted of individuals who were 18 years of age or older. A 3.7 mm diameter implant at least 13 mm in length was placed in adequate native bone without active periodontal disease, and which required no bone grafting. The implants were restored immediately with an acrylic resin provisional crown that was adjusted to eliminate occlusal contacts. Metal-ceramic final restorations were placed four to six months postoperatively. Radiographic and clinical data was collected at three-month intervals to evaluate periodontal status (bone loss and tissue health). The patients were followed for an average of approximately 2.5 years. Method of Data Analysis: During the investigation, the primary efficacy variable was immobility of the implant, and was assessed beginning at the three month recall visit following placement of the definitive restoration. To be considered a success at the primary level, the implant had to demonstrate no visible mobility. The secondary level of success was evaluated using measurement of infection/pain and radiolucency. To be considered successful, the implant site could not demonstrate persistent and/or irreversible signs of pain and/or infection. Bone surrounding the implant had to demonstrate an absence of radiolucent borders. Bone loss, levels of gingival recession, and the amount of plaque accumulation around the implant were also recorded. Periapical radiographs were used to measure marginal bone loss and implant health. Investigators estimated bone loss radiographically by using the implant platform as a reference point. The height of the crestal bone was measured and recorded from both the mesial and distal surfaces of the implant platform. The implant itself was used to reference bone height measurements. All measurements were made from periapical radiographs. The implants were examined with a calibrated periodontal probe which standardized force delivery during pocket depth determination (Pressure Standardized Probes, Vivadent, Inc.). With the crown removed to improve access, six sites were probed for each implant including direct facial, direct lingual, mesial-lingual line angle, distal-lingual line angle, mesial-facial line angle, and distal-facial line angle sites. The six clinical measurements were averaged as well as evaluated individually. To avoid disrupting gingival maturation, probing was not initiated until the prostheses had been in place for at least 6 months. Historical controls were used for comparison to the experiment group in this study. The historical control group consisted of subjects reported to have received conventional dental implant therapy. Historical control data was acquired from available dental literature. A review of the literature shows that conventional implant systems perform successfully at a rate of about 95%. Statistical Considerations: The data collected for each variable was presented using descriptive statistics, 39