Analysis of relapse after mandibular advancement surgery.

Seventeen cases of mandibular advancement surgery were evaluated for skeletal relapse; 12 included long-term evaluation. Inferior movement of the proximal segment with displacement of the condyle occurred at the time of surgery or in the immediate postoperative period. This movement was closely associated with subsequent skeletal relapse of the distal segment. This may represent a cause-and-effect relationship mediated through the soft tissue attachments of periosteum and muscle that are stretched at the time of surgery.     

Independent risk factors for long-term skeletal relapse after mandibular advancement with bilateral sagittal split osteotomy

The purpose of this retrospective cohort study was to identify the independent risk factors for long-term skeletal relapse following mandibular advancement with bilateral sagittal split osteotomy. Univariate and multivariate linear regression analyses were performed including nine common risk factors for relapse as independent variables and horizontal/vertical long-term (≥2 years) skeletal relapse as dependent variables. Ninety-six patients were analyzed; 66 were female (68.8%) and the average age of the patients was 29.7 ± 10.5 years. Over an average follow-up of 3.8 ± 1.8 years after an initial mandibular advancement of 8.8 ± 2.4 mm, long-term skeletal relapse of 1.6 ± 1.0 mm horizontal and 0.9 ± 0.7 mm vertical was found. Multivariate analysis identified age, preoperative mandibular plane angle (MPA), bimaxillary surgery, counterclockwise mandibular rotation, and the magnitude of mandibular advancement to be significantly associated with horizontal long-term skeletal relapse. Preoperative MPA, counterclockwise mandibular rotation, and the magnitude of mandibular advancement were significantly associated with vertical long-term skeletal relapse. Thus preoperative MPA, the magnitude of mandibular advancement, and counterclockwise mandibular rotation of the mandible were found to be independent risk factors for both horizontal and vertical long-term skeletal relapse. Although long-term skeletal relapse cannot be avoided entirely, understanding the independent risk factors and their contributions will optimize treatment planning and long-term stability.     

Skeletal relapse after mandibular advancement and setback in single-jaw surgery

PURPOSE: The aim of this study was to identify contributing factors to skeletal relapse by analyzing cephalometric changes after bilateral sagittal split ramus osteotomy. PATIENTS AND METHODS: This study included 60 consecutive patients who underwent either mandibular advancement (30 patients) or setback surgery (30 patients). There were 36 women and 24 men (mean age, 23 years). The radiographs of these patients taken immediately before operation, at 1 week, and 14 months postoperatively were studied. To analyze the influence of hyper- and hypodivergent facial patterns on the surgical outcome, the patients were divided into 3 groups according to the mandibulo-nasal plane angle. The position of the maxilla was also taken into account. RESULTS: Measured at B-point, skeletal relapse was 1.3 mm (30%) after mean advancement of 4.4 mm and 0.8 mm (12%) after setback of 6.0 mm. The magnitude of the surgical movement correlated with skeletal relapse. However, the correlation was not linear. Advancement of greater than 7 mm is associated with an increased tendency to relapse (r=0.52), but setback of more than 12 mm with a decreased tendency (r=-0.95). The retrognathic patients with a high mandibulo-nasal plane angle (hyperdivergence) had 30% higher relapse rate. Patients with hypodivergent facial patterns had less relapse in both advancement and setback surgery. CONCLUSION: Skeletal relapse was affected by magnitude of surgical movement and different facial patterns according to the mandibulo-nasal plane angle; however, influences of both factors were different between mandibular advancement and setback.     

Nature of relapse after surgical mandibular advancement

Pre-operative, post-operative and follow-up cephalometric records of 16 cases of mandibular retrognathia treated by surgical mandibular advancement were analysed retrospectively. The results showed good mean stability in the mandibular advancement with variable individual relapse. The pre-operative mandibular plane angle, magnitude of the advancement and post-operative increase in the posterior lower face height were the variables chiefly related to relapse. There appeared to be limited control over the posterior segment which was liable to distraction and rotation. The follow-up changes were time linked. Both mechanical and biological factors are postulated to explain the relapse.     

Interaction analysis of risk factors for long-term skeletal relapse following mandibular advancement with bilateral sagittal split osteotomy

The aim of this study was to identify interaction effects among risk factors for long-term skeletal relapse. The study sample consisted of 96 patients who underwent mandibular advancement with bilateral sagittal split osteotomy. Ten predictor variables were analyzed for an interaction effect: sex, age, preoperative temporomandibular joint symptoms, mandibular plane angle (MPA), single or double jaw surgery, clockwise or counterclockwise mandibular rotation, magnitude of mandibular advancement, concomitant genioplasty, type of fixation, and follow-up duration. Modeling interactions between pairs of covariates were applied to detect a significant interaction among these risk factors on horizontal and vertical long-term skeletal relapse, respectively. Stratification analyses and two-way full factorial interaction analyses were performed to demonstrate how the interaction influenced the associations between covariates and relapse. The interactions between sex and mandibular rotation (P = 0.006) and between MPA and mandibular rotation (P = 0.002) were statistically significant for horizontal long-term skeletal relapse. No significant interaction was identified for vertical relapse. This study showed that female patients and those with an MPA ≥30° undergoing counterclockwise mandibular rotation are predisposed to greater horizontal long-term skeletal relapse. Therefore, the judicious use of counterclockwise rotation is recommended in order to minimize the relapse, especially in female patients and those with a high MPA.     

Cause of early skeletal relapse after mandibular setback

The present study was undertaken to examine the factors that might be responsible for the skeletal relapse occurring during the period of intermaxillary fixation after mandibular setback osteotomy. Fifteen patients, treated for absolute mandibular prognathism by modified sagittal split ramus osteotomy and fixation by skeletal suspension wiring, were evaluated cephalometrically by reference to the degree of postsurgical superior shift of the gonial region of the distal segment as a parameter of relapse since such a shift was evident despite the use of wiring. It was found that the degree of inadvertent anteroposterior rotation of the proximal segment at surgery, rather than the extent and pattern of surgical repositioning of the distal segment, was significantly correlated with the degree of shift. This result emphasizes the justification of preserving the proximal segment in its exact original anatomic site, in addition to the use of skeletal fixation, to ensure predictable stability after mandibular setback osteotomy.     

The contributing role of condylar resorption to skeletal relapse following mandibular advancement surgery: report of five cases

The contribution of condylar resorption to relapse following mandibular advancement surgery has not been fully evaluated, yet may contribute substantially to postoperative occlusal and skeletal changes too often considered simply as "relapse." Five cases showing a typical relapse pattern are presented, illustrating the role of condylar resorption. Preoperative factors that may contribute to the development of condylar resorption (age, sex, high preoperative mandibular plane angle, and the presence of preoperative temporomandibular joint disease), as well as intraoperative and postoperative factors, are discussed. A target group is defined in which special considerations should be made with regard to preoperative and postoperative management.     

The short-term and long-term soft-tissue profile changes accompanying mandibular advancement surgery

To provide an improved data base for predicting the soft-tissue changes that accompany mandibular advancement surgery, short- and long-term serial cephalograms from the records of eighteen patients were analyzed. Hard- and soft-tissue landmarks were located on serial tracings and later were reduced to rectangular X-Y coordinates for computer-generated measurement data and statistical analyses. The interpretation of mean value, ratio, and regression equation data showed that the lower lip, inferior labial sulcus, and chin tissues moved forward and downward. The mandibular short-term (mean = 3.7 months postsurgery) horizontal change means were greater than the long-term (mean = 18 months postsurgery) horizontal change means. The posteriorly directed long-term means may result from functional adaptations that follow the short-term surgery-related spatial changes. These data also show the need for long-term prediction data to supplement the short-term data base.     

The quantitative correlation between condylar resorption and skeletal relapse following mandibular advancement in skeletal class II malocclusion patients

ObjectiveThe purpose of this study was to analyze the quantitative correlation between condylar resorption and skeletal relapse after mandibular advancement surgery.Materials and methodsSkeletal Class II malocclusion patients who underwent bilateral sagittal split ramus osteotomy (BSSRO) were included. Three-dimensional reconstruction was based on one-week and one-year post-operative CT scans. The condylar morphological alterations were assessed by anterior-posterior, medial-lateral diameter and condylar height. The mandibular relapse was calculated by the positional changes of pogonion, menton, gonions, gnathion and mental foramens. All data were measured by MIMICS and analyzed by SPSS software; significance was set at p<0.05.Results31 patients (62 condyles) were enrolled into this study. 28 of 62 condyles showed resorption beyond 1 mm on condylar height and 15 were beyond 2 mm. Positional changes of chin, mental foramens and gonion were respectively 1.57 ± 2.36 mm, 1.31 ± 1.23 mm and 1.42 ± 1.02 mm. 21 of 31 patients experienced mandibular relapse less than 1 mm but additional 4 patients showing relapse more than 2 mm. Correlation with moderate intensity could be observed between condylar height alteration and post-operative mandibular displacement more than 1 mm (p = 0.035).ConclusionThe resorption degree of condylar height can be regarded as a useful parameter for evaluating post-operative skeletal relapse.     

A comparative study of stability after mandibular advancement surgery

The postsurgical stability of two groups of patients treated with different fixation techniques after mandibular advancement was evaluated retrospectively. Sixteen patients (group 1) underwent rigid osseous fixation, and another group of 16 patients (group 2) underwent intraosseous wiring fixation. Our findings suggested that skeletal and dental changes occurred in both groups as a result of adaptation to the altered functional equilibrium. Relapse resulting in a percentage loss of the initial advancement occurred primarily 6 to 8 weeks postsurgically. No statistically significant difference was found to exist in the short-term and long-term rates between the two groups. For the population studied, relative stability after mandibular advancement surgery was affected more by individual variability than by the fixation technique.     

Three-dimensional evaluation of long-term skeletal relapse following Le Fort I maxillary advancement surgery: a 2-year follow-up study

The aim of this study was to assess relapse following Le Fort I (LFI) maxillary advancement with superior or inferior repositioning at 2 years of follow-up. A total of 50 patients (26 female, 24 male; age range 15–56 years) with skeletal class II or III, who underwent bimaxillary surgery with LFI maxillary advancement in combination with either superior or inferior repositioning and also mandibular advancement/setback, were recruited. Preoperative (T0), immediate postoperative (T1), and 2-year postoperative (T2) cone beam computed tomography scans were acquired. Data were imported into a validated module to assess the skeletal movement (T0–T1) and relapse (T1–T2). Overall, the majority of the translational and rotational movements showed a relapse of <1 mm and <1°. Patients undergoing maxillary advancement with inferior repositioning in combination with mandibular advancement showed the highest amount of translational relapse in a superior (0.86 ± 0.85 mm, P < 0.0001) and posterior direction (?0.65 ± 1.11 mm, P < 0.0001). In relation to patients who received a bone graft, inferior repositioning with mandibular setback showed the highest maxillary relapse in a superior direction (1.20 ± 1.56 mm, P = 0.0719) with counterclockwise pitch rotation (2.15 ± 0.64°, P = 0.3759). Amongst the non-grafted procedures, superior repositioning with mandibular setback exhibited the highest relapse in a medial direction (1.38 ± 2.78 mm, P = 0.3981). Maxillary advancement was found to be a highly stable procedure with a lack of superoinferior stability in patients undergoing inferior repositioning.     

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).     

Analysis of soft tissue profile changes after mandibular advancement surgery

The aim of this study was to analyze changes in soft tissue profile after mandibular advancement surgery, with special emphasis on the effect of skeletal relapse and different Class II facial patterns. The cephalometric radiographs of 30 consecutive patients (24 women and 6 men, mean age 23 years) who underwent sagittal split osteotomy were studied. The radiographs were taken immediately before operation, at one week and 14 months postoperatively. To analyze the possible influence of hyper- and hypodivergent facial patterns, the patients were classified into low- (4 patients), medium- (16 patients) and high-angle (10 patients) groups according to the magnitude of the mandibulonasal plane angle. The main movement occurred in the horizontal plane. Soft tissue pogonion and mentolabial fold were found to follow the underlying skeletal structures in a nearly 1:1 ratio. On final follow-up, skeletal relapse of 1.3 mm was measured at B-point and of 1.5 mm at pogonion. Taking the skeletal relapses into account, the ratios of both corresponding soft tissue references (alternative ratios) dropped to 60%. Soft tissue pogonion is the most reliable reference for the planning of mandibular advancement. The ratio of soft tissue movement to final skeletal position at the chin amounts to 60% for a realistic prediction. However, the low-angle group differed from other groups by showing a markedly low soft-to-hard tissue ratio of only 14% at pogonion and a high ratio of 109% at the mentolabial fold. However, these differences in ratios between the groups were statistically not significant.     

Factors contributing to skeletal relapse after surgical correlation of mandibular prognathism

Postoperative follow-up and multiple regression analysis of skeletal relapse following mandibular setback were carried out to clarify the timing and causes of the relapse. The subjects were 24 mandibular prognathism patients. All patients underwent intraoral oblique sagittal splitting osteotomy with circumferential wiring and intermaxillary fixation for 8 weeks. Occlusal splints were not used. Postoperative positional changes of segments were evaluated by lateral cephalograms taken at appropriate intervals. Horizontal relapse was most evident within six months after surgery; vertical relapse seldom occurred. Multiple regression analysis revealed little association between preoperative morphological patterns and postoperative relapse. Although spatial changes of the proximal segment at operation and age of the patient were the best predictors for postoperative horizontal relapse, analysis indicated unsatisfactory prediction of vertical relapse because of its rare occurrence. Based on these results, the aetiology of relapse is discussed and two proposals are suggested for its prevention.     

Three-dimensional evaluation of distal and proximal segment skeletal relapse following isolated mandibular advancement surgery in 100 consecutive patients: A one-year follow-up study

The aim of this study was to perform a three-dimensional evaluation of the skeletal relapse of the proximal and distal mandibular segments following isolated bilateral sagittal split osteotomy advancement surgery. One hundred consecutive patients (mean age 25.8 ± 11.7 years), comprising 65 female patients (mean age 26.4 ± 12.1 years) and 35 male patients (mean age 24.6 ± 11.0 years) requiring mandibular advancement without genioplasty, were enrolled prospectively in the study. Cone beam computed tomography scans were acquired for each patient at three time-points: preoperatively, immediately (1–6 weeks) after surgery, and 1 year after surgery. A validated tool was utilized to assess the surgical movement and relapse. Based on percentage, the majority of the distal and proximal translational and rotational movements relapsed within the range of ≤2 mm and ≤2°. The distal segment revealed a significant relapse in a posterior, inferior, and clockwise pitch direction. Both left and right proximal segments showed a significant translational relapse in the medial, posterior, and superior direction. Amongst the rotational parameters, proximal segments relapsed significantly in clockwise pitch, clockwise roll, and counterclockwise yaw direction. Overall, both distal and proximal bone segments showed a clinically acceptable translational and rotational stability. The proximal segments torqued towards their original position with a reduction of flaring.     

Nomogram model to predict postoperative relapse after mandibular osteoradionecrosis surgery

Purpose

Osteoradionecrosis of the mandible (ORNM) is one of the most devastating complications following radiotherapy. Postoperative relapse (POR) occurs with high incidence even if a radical resection is performed. The current investigation was designed to identify prognostic factors for POR and to establish a nomogram model to estimate the risk for the onset of POR of ORNM.

Soft tissue profile changes following mandibular advancement surgery: predictability and long-term outcome.

The objectives of this cephalometric study were to assess long-term changes in the soft tissue profile following mandibular advancement surgery and to investigate the relationship between soft tissue and hard tissue movements. The sample consisted of 61 patients treated consecutively for mandibular retrognathism with orthodontic therapy combined with bilateral sagittal split osteotomy and rigid fixation. Lateral cephalograms were taken on 6 occasions: immediately before surgery, immediately after surgery, 2 and 6 months after surgery, and 1 and 3 years after surgery. Postsurgical changes in the upper and the lower lips and the mentolabial fold were more pronounced among low-angle cases compared with high-angle cases. In accordance with other studies, the soft tissue chin and the mentolabial fold were generally found to follow their underlying skeletal structures in a 1:1 ratio. Because of the strong influence skeletal relapse has on soft tissue profile changes, alternative ratios of soft tissue-to-hard tissue movement that accounted for mean relapse were also generated. It is suggested that if a more realistic long-term prediction of the postsurgical soft tissue profile is desirable, then ratios incorporating mean relapse should be used rather than estimates based on a 1:1 relationship.     

Characteristics of mandibular advancement surgery dependent on lower facial height differences in study of skeletal Class II patients with long-term stability

We studied patients who underwent mandibular advancement surgery and showed a stabilized occlusal condition at 5 years after surgery. The patients were classified into 2 groups [long face type (LF group: 16 cases), short face type (SF group: 10 cases)] according to immediate presurgery face type. To clarify the characteristics of the operative method formulated based on lower facial height, morphological changes during the 5-year postoperative period were compared between the groups.There was no statistically significant difference in amount of advancement between the two groups, though lower facial height showed a tendency to increase in group SF. The proximal segment was advanced to the anterosuperior position in both groups.To determine postoperative stability, in the LF group, there were no statistically significant differences for lower face height. In the SF group, the condylar axis increased in the period from immediately after to 6 months after surgery. Correlation analysis revealed that the backward rotation of the proximal segment was greater during the first 6 months, as the amount of surgical advancement of the chin was larger. As a result, the chin was advanced during surgery and the proximal segment was advanced toward the anterosuperior position in both groups. In the SF group, the characteristics of the operative design increased the lower facial height.