Joseph E. Van Sickels

Relapse after rigid fixation of mandibular advancement

In 19 subjects rigid fixation of bilateral sagittal split osteotomies was used for mandibular advancement. Five angles and four linear measurements were determined cephalometrically for two time intervals: before surgery to immediately after surgery (T1-T2), and immediately after surgery to six months to one year after surgery (T2-TL). A multiple regression analysis with a backward stepping procedure was used to determine relationships between relapse, as defined by the position of pogonion at T2-TL (PgT2) and B point during this same time interval (BT2). The only significant predictor of PgT2 was PgT1 (P less than 0.001) (amount of advancement of pogonion during the time interval T1-T2). When BT2 was examined, both the change in position of B point at T1-T2 (P less than 0.001) and the change in anterior facial height at T1-T2 (P less than 0.02) were significant predictors of relapse. There were no other predictors of relapse. Advancements of 6 to 7 mm or greater as measured at B or Pg deserve special attention as they were more predisposed to relapse. Methods for preventing relapse are discussed.

Neurosensory disturbance with rigid fixation of the bilateral sagittal split osteotomy

Twenty-one patients who underwent bilateral sagittal split osteotomies using rigid fixation were evaluated by neurosensory testing. Neurosensory tests included light touch (LT), brush stroke direction (BSD), two-point discrimination (2-P), and temperature (T). Tests were conducted using the two-alternate forced choice method. The density of neurosensory disturbance was examined as well as the incidence of neurosensory disturbance as it correlated with age of the patient. The incidence of neurosensory disturbance was 45.2% (19/42) to LT, 52.4% (22/42) to BSD, 33.3% (14/42) to 2-P and 7.1% (3/42) to T. The majority of demonstrable neurosensory disturbances were not dense. Increased age was associated with an increased incidence of neurosensory disturbance.

Stability of orthognathic surgery: a review of rigid fixation

The use of rigid fixation with orthognathic surgery was greeted by both excitement and healthy concern when it began to find its way into the literature approximately 10 years ago. The purpose of this paper is to review the literature and make comments based on the experience of the senior author on whether one of the early premises was true. Has rigid fixation improved stability with orthognathic surgery? The authors chose to examine mandibular advancements treated with a bilateral sagittal split osteotomy and maxillary osteotomies treated with a Le Fort I osteotomy. When compared to wire osteosynthesis, rigid fixation has improved stability; however, the individual move associated with the osteotomy must be considered. In some cases, auxiliary techniques should be used to ensure stability. Condylar resorption with mandibular advancement continues to be an area of concern.

Condylar displacement and temporomandibular joint dysfunction following bilateral sagittal split osteotomy and rigid fixation

In this study changes in intercondylar width (ICW) and intercondylar angle (ICA) that occurred with rigid fixation after bilateral sagittal split osteotomy and mandibular advancement are documented and correlated with temporomandibular (TM) symptoms, magnitude of advancement, and mandibular shape. Even though individual changes occurred, there was no significant difference between the mean preoperative and postoperative ICA and ICW measurements. There was also no significant difference between the preoperative and postoperative incidence of TM pain or clicking. No correlation was found between the magnitude of advancement and the percent change in ICA or ICW, and the mandibular shape did not correlate to changes in ICW. This study suggests that screw osteosynthesis does not significantly change ICA or ICW. The fact that no significant increase in TM symptoms occurred indicates that the changes in condylar position that did occur were within the range of clinical adaptability of the patients.

Factors Contributing to Relapse in Rigidly Fixed Mandibular Setbacks

The incidence of, and factors accounting for, relapse in 25 subjects who underwent mandibular setbacks via a bilateral sagittal split osteotomy with rigid fixation were studied. Fourteen had single-jaw operations, and the remaining 11 had concomitant maxillary procedures. Cephalometric radiographs were reviewed preoperatively, immediately postoperatively, and 6 months to 3 years after surgery. Relapse was defined as forward movement of pogonion during the postoperative period. No difference in the movement of the mandible in one- or two-jaw cases was noted. Even with excellent occlusal results, there was a tendency for the mandible (chin point) to rotate forward. In the one-jaw cases 43.7% relapse was noted, whereas 53.4% was seen in the two-jaw cases. A regression analysis showed that the magnitude of setback was the single factor that significantly predicted relapse in one-jaw cases, whereas alteration of the proximal segment accounted for relapse in two-jaw procedures. These results seem interrelated when considering alterations in the spatial arrangement of the muscular tissues and their attachments.

Stability associated with mandibular advancement treated by rigid osseous fixation

Relapse after a mandibular sagittal ramus split osteotomy (SSO) fixed by transosseous wire has been shown to occur. Authors who use rigid screw fixation claim a lesser incidence of such relapse. Nine subjects with horizontal mandibular deficiency treated by an SSO and fixed with bone screws were prospectively studied. Serial cephalometric radiographs were traced and superimposed on the sella-nasion line and anterior cranial base structures. A markedly reduced horizontal movement during the first six weeks at both points B and Pg, followed by a slight advancement at six months, was observed. Concomitantly, the surgically increased facial height was shown to subsequently decrease during both those time intervals. The stability of this procedure warrants further investigation.

Sexual dimorphism in the distribution of estrogen receptors in the temporomandibular joint complex of the baboon

The localization of radiolabeled estradiol was examined in the temporomandibular complex of male baboons by means of an autoradiographic technique. Five baboons were studied. Four animals received only the tritiated estrogen (1 microgram/kgm) and one animal, which served as the control, received both the tritiated estrogen and the unlabeled estrogen (100 micrograms/kgm). The study failed to demonstrate nuclear uptake and retention of tritiated estrogen in any of the tissues of the temporomandibular joint complex, including the articular surface of the condyle, articular disk, capsule, and muscles of mastication. However, estrogen receptors were identified in other tissues, including the pituitary. All tissues examined in the control animal were negative for estrogen receptors. It was concluded that there were no estrogen receptors in the temporomandibular joint complex of aged male baboons. As in previous studies, these findings provide additional evidence of a sexual dimorphism with respect to estrogen receptor distribution in the temporomandibular joint complex of the baboon. Furthermore, it is reasonable to speculate that estrogens may modulate a variety of metabolic functions in these tissues that could be important in the maintenance, repair, and/or pathogenesis of the temporomandibular joint.

Causes, location, and timing of relapse following rigid fixation after mandibular advancement

The purpose of this study was to evaluate two different groups of patients who underwent bilateral sagittal split osteotomy for mandibular advancement. One group demonstrated no relapse, whereas a second group had documented relapse. The following questions were asked: 1) What factors contribute to relapse? 2) At what site in the mandible is movement seen? and 3) During what period does movement occur? A retrospective lateral cephalometric serial analysis was performed on 50 patients at multiple time intervals. Criteria for a candidate include 1) mandibular advancement surgery with rigid fixation, with or without genioplasty, 2) no maxillary surgery, and 3) relapse of 25% or more of the advancement. Of the 50 patients analyzed, 13 (26%) showed relapse of 25% or more and served as the relapse group. Twelve patients showed no relapse and served as the comparison group. Multiple-regression analysis for the relapse group showed that magnitude of advancement, increasing gonial arc and changing mandibular plane significantly accounted for 84.9% of the variance observed in relapse (P less than .001). Repeated-measures ANOVA showed that the majority of relapse occurred in the first 6 weeks after surgery (68%, P less than .05). Results of a paired t test showed that a significant change occurred in all the linear and angular measures except SN-AR-GO (P less than .05).

Estrogen receptors in the temporomandibular joint of the baboon (Papio cynocephalus): An autoradiographic study☆

Using an autoradiographic method, the temporomandibular joint (TMJ) complex of five aged female baboons was studied for the presence of receptors for estradiol-17 beta. The study was performed in an effort to learn more of the pathophysiology of this joint and in an attempt to provide a scientific basis to explain the reported preponderance of women who seek and undergo treatment for signs and symptoms referable to the TMJ. This experiment revealed that the TMJ complex contains numerous cells with receptors for estrogen, particularly the articular surface of the condyle, articular disk, and capsule. Muscles of mastication contained relatively fewer receptors. As a result, one may postulate a role for the sex steroid hormones in the maintenance, repair, and/or pathogenesis of the TMJ. Additional studies are necessary to fully determine the significance of hormone receptors in this site and any correlation between diseases of the TMJ and the endocrine status of affected patients.

Condylar Resorption After Bicortical Screw Fixation of Mandibular Advancement

PURPOSEnThis study evaluated long-term condylar resorption after mandibular advancements stabilized with bicortical screws.nnnPATIENTS AND METHODSnOne hundred mandibular deficiency patients who underwent bilateral sagittal split osteotomies (BSSO) fixed with three bicortical screws per side, and who were followed for a minimum of 1 year with complete radiographic records, were evaluated. Preoperative panoramic radiographs were traced and superimposed as a best fit over long-term panoramic radiographs. Cephalometric tracings were available on all patients preoperatively, immediately after surgery, 6 to 8 weeks after surgery, and at long term after surgery. These tracings were used to show the amount of the initial advancement and any changes that occurred between 6 to 8 weeks and long term in those patients who exhibited 10% or greater changes in their condylar height. Preoperative temporomandibular joint signs and symptoms were recorded on all patients before surgery and at 6 months after surgery.nnnRESULTSnThere were 10 patients who had 10% or greater vertical change in their condyles; all changes were unilateral. Large advancement (P > .009) and preoperative temporomandibular joint symptoms (P > .01) statistically correlated with long-term postoperative condylar resorption. There was not a direct correlation between the amount of vertical change in the condyle and the amount of relapse. There was an improvement in temporomandibular joint symptoms for the group as a whole and in the group with condylar resorption.nnnCONCLUSIONSnPatients with large advancements and preoperative temporomandibular joint symptoms appear to be at risk for condylar resorption. These results are similar to those from other studies in which rigid fixation or miniplates were used for cases of mandibular advancement.