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Do Miniplates With Monocortical Screws Fail at an Unacceptably High Rate in Bilateral Sagittal Split Osteotomies? A Retrospective Chart Review
Poster Session
ORTHOGNATHIC
plate failure are the presence of a parafunctional habit and the magnitude of mandibular advancement (>7 mm).
POSTER 36 Do Miniplates With Monocortical Screws Fail at an Unacceptably High Rate in Bilateral Sagittal Split Osteotomies? A Retrospective Chart Review P. M. Stefanuto: Dalhousie University, J. C. Doucet The purpose of this study is to determine the rate of fixation failure when using miniplates with monocortical screws for rigid internal fixation in orthognathic surgery. A retrospective chart review was carried out for all bilateral sagittal split osteotomy (BSSO) operations undertaken from the years 2004 to 2012 at the Department of Oral and Maxillofacial Surgery , Queen Elizabeth II Health Sciences Center, Halifax, Nova Scotia, Canada. Operations were carried out by one of 7 attending surgeons at the QEII for a variety of dentofacial deformities including maxillomandibular advancement for obstructive sleep apnea syndrome (OSAS). All hardware failures that occurred due to miniplates bending or breaking, as well as the loosening of monocortical fixation screws were included in the study. Procedural parameters examined were: initial skeletal deformity, movement magnitude, number of screws used, presence of parafunctional habit, and one-jaw vs. two jaw surgery. A total of 4626 miniplates with monocortical screws were placed in 2313 BSSO performed with or without concurrent Le fort I osteotomies. Of the sample, 443 patients received a BSSO for the purpose of mandibular setback and 1870 required mandibular advancement. A total of 11 failures were recorded (11/ 4626=0.24%) in 7 patients (1 male; 6 female). Five of the 7 patients (71%) had undergone maxillomandibular advancement for the purpose of OSAS correction. The initial skeletal deformity was mandibular anteroposterior deficiency in 7 patients, with concurrent vertical maxillary excess in 4 patients, and vertical maxillary deficiency in 1 patient. No failures were associated with a mandibular setback. The average amount of mandibular advancement was 9 mm (SD=2.17) in failure cases. No failures were recorded in patients with fewer than 7 mm of advancement. The average number of monocortical screws used in failed plates was 4.2 (SD=0.82). Five of the patients (71%) had a parafunctional habit (nocturnal bruxism) and all but one failure had a concurrent Le fort I osteotomy. According to subjective analysis, the incidence of miniplate with monocortical screw failure in BSSO is very low. The most significant factors associated with AAOMS 2013
References: 1. Blomqvist J E, Ahlborg G, Isaksson S, Svartz K (1997): A comparison of skeletal stability after mandibular advancement and use of two rigid internal fixation techniques. Journal of Oral and Maxillofacial Surgery: Official Journal of the American Association of Oral and Maxillofacial Surgeons, 55(6), 568-74; discussion 574-5. 2. Yamashita Y, Mizuashi K, Shigematsu M, Goto M (2007): Masticatory function and neurosensory disturbance after mandibular correction by bilateral sagittal split ramus osteotomy: A comparison between miniplate and bicortical screw rigid internal fixation. International Journal of Oral and Maxillofacial Surgery, 36(2), 118-122. doi:10.1016/j.ijom.2006.09.020
POSTER 37 Retrospective Study: A Study Evaluating the Anatomical Variances of the Pterygomaxillary Junction and its Impact on Pterygoid Plate Fractures With Le Fort I Osteotomies D. M. Wilson: University of Michigan Retrospective Study: A study evaluating the anatomical variances of the pterygomaxillary junction and its impact on pterygoid plate fractures with Le Fort I osteotomies. Le Fort 1 osteotomies are used to correct a variety of maxillofacial deformities. Its technical ease and relatively low complication rates have made this procedure dependable and stable in resolving functional and aesthetic issues. However, a Le Fort 1 osteotomy may be associated with untoward pterygoid plate fractures that extend cephalad at the time of maxillary down fracture. It is the goal of the authors to determine if there are any anatomical variances that may contribute to these untoward fractures. 87 Patients who underwent Le Fort 1 Osteotomies from the dates of 02/10/10 to 12/22/11. Prior to downfracture, surgery at the pterygomaxillary junction was carried out with an osteotome, oscillating saw, or nothing. Computer tomography scans were done before surgery and 6 weeks postoperatively and evaluated. The pterygoid plates were evaluated for fracture. If a fracture occurred it was recorded as either a low or high fracture. High fracture was determined if higher than half way up pterygoid plate. The reference points for evaluation included the length of the maxilla (from piriform rim to pterygomaxillary junction), the lateral plate, the medial plate, anterior-posterior and medial-lateral length of the pterygomaxillary junction, the distance from the lateral maxillary sinus wall to pterygomaxillary junction, the e-61
ORTHOGNATHIC
plate failure are the presence of a parafunctional habit and the magnitude of mandibular advancement (>7 mm).
POSTER 36 Do Miniplates With Monocortical Screws Fail at an Unacceptably High Rate in Bilateral Sagittal Split Osteotomies? A Retrospective Chart Review P. M. Stefanuto: Dalhousie University, J. C. Doucet The purpose of this study is to determine the rate of fixation failure when using miniplates with monocortical screws for rigid internal fixation in orthognathic surgery. A retrospective chart review was carried out for all bilateral sagittal split osteotomy (BSSO) operations undertaken from the years 2004 to 2012 at the Department of Oral and Maxillofacial Surgery , Queen Elizabeth II Health Sciences Center, Halifax, Nova Scotia, Canada. Operations were carried out by one of 7 attending surgeons at the QEII for a variety of dentofacial deformities including maxillomandibular advancement for obstructive sleep apnea syndrome (OSAS). All hardware failures that occurred due to miniplates bending or breaking, as well as the loosening of monocortical fixation screws were included in the study. Procedural parameters examined were: initial skeletal deformity, movement magnitude, number of screws used, presence of parafunctional habit, and one-jaw vs. two jaw surgery. A total of 4626 miniplates with monocortical screws were placed in 2313 BSSO performed with or without concurrent Le fort I osteotomies. Of the sample, 443 patients received a BSSO for the purpose of mandibular setback and 1870 required mandibular advancement. A total of 11 failures were recorded (11/ 4626=0.24%) in 7 patients (1 male; 6 female). Five of the 7 patients (71%) had undergone maxillomandibular advancement for the purpose of OSAS correction. The initial skeletal deformity was mandibular anteroposterior deficiency in 7 patients, with concurrent vertical maxillary excess in 4 patients, and vertical maxillary deficiency in 1 patient. No failures were associated with a mandibular setback. The average amount of mandibular advancement was 9 mm (SD=2.17) in failure cases. No failures were recorded in patients with fewer than 7 mm of advancement. The average number of monocortical screws used in failed plates was 4.2 (SD=0.82). Five of the patients (71%) had a parafunctional habit (nocturnal bruxism) and all but one failure had a concurrent Le fort I osteotomy. According to subjective analysis, the incidence of miniplate with monocortical screw failure in BSSO is very low. The most significant factors associated with AAOMS 2013
References: 1. Blomqvist J E, Ahlborg G, Isaksson S, Svartz K (1997): A comparison of skeletal stability after mandibular advancement and use of two rigid internal fixation techniques. Journal of Oral and Maxillofacial Surgery: Official Journal of the American Association of Oral and Maxillofacial Surgeons, 55(6), 568-74; discussion 574-5. 2. Yamashita Y, Mizuashi K, Shigematsu M, Goto M (2007): Masticatory function and neurosensory disturbance after mandibular correction by bilateral sagittal split ramus osteotomy: A comparison between miniplate and bicortical screw rigid internal fixation. International Journal of Oral and Maxillofacial Surgery, 36(2), 118-122. doi:10.1016/j.ijom.2006.09.020
POSTER 37 Retrospective Study: A Study Evaluating the Anatomical Variances of the Pterygomaxillary Junction and its Impact on Pterygoid Plate Fractures With Le Fort I Osteotomies D. M. Wilson: University of Michigan Retrospective Study: A study evaluating the anatomical variances of the pterygomaxillary junction and its impact on pterygoid plate fractures with Le Fort I osteotomies. Le Fort 1 osteotomies are used to correct a variety of maxillofacial deformities. Its technical ease and relatively low complication rates have made this procedure dependable and stable in resolving functional and aesthetic issues. However, a Le Fort 1 osteotomy may be associated with untoward pterygoid plate fractures that extend cephalad at the time of maxillary down fracture. It is the goal of the authors to determine if there are any anatomical variances that may contribute to these untoward fractures. 87 Patients who underwent Le Fort 1 Osteotomies from the dates of 02/10/10 to 12/22/11. Prior to downfracture, surgery at the pterygomaxillary junction was carried out with an osteotome, oscillating saw, or nothing. Computer tomography scans were done before surgery and 6 weeks postoperatively and evaluated. The pterygoid plates were evaluated for fracture. If a fracture occurred it was recorded as either a low or high fracture. High fracture was determined if higher than half way up pterygoid plate. The reference points for evaluation included the length of the maxilla (from piriform rim to pterygomaxillary junction), the lateral plate, the medial plate, anterior-posterior and medial-lateral length of the pterygomaxillary junction, the distance from the lateral maxillary sinus wall to pterygomaxillary junction, the e-61