Do Miniplates With Monocortical Screws Fail at an Unacceptably High Rate in Bilateral Sagittal Split Osteotomies? A Retrospective Chart Review
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 Lefort 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 Lefort 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 plate failure are the presence of a parafunctional habit and the magnitude of mandibular advancement (>7 mm).
References
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