Stability of the hard and soft tissue profile after mandibular advancement in sagittal split osteotomies: a longitudinal and long-term follow-up study

The aim of the study was to conduct a long-term follow-up investigation of the stability of hard and soft tissues after bilateral sagittal split osteotomy (BSSO) with rigid internal (RIF) fixation to advance the mandible. Sixteen consecutive patients (12 females and 4 males, mean age 21.4 years) were available for re-examination 12.7 years (T5) after surgery. The preceding follow-ups were before (T1), and 5 days (T2), 7.3 months (T3), and 13.9 months (T4) after surgery. Lateral cephalograms were traced by hand, digitized, and evaluated with the Dentofacial Planner program. The x-axis for the system of co-ordinates ran through sella (point zero) and the line NSL -7 degrees. Thus, the program determined the x- and y-values of each variable and the usual angles and distances. Statistical analysis was carried out using Wilcoxon's matched-pair signed-ranks test with Bonferroni adjustments. The relationships between the examined variables were analysed by Spearman rank correlation coefficients. The backward relapse at point B (T5) was 2.42 mm, or 50 per cent, and at pogonion 3.21 mm, or 60 per cent of the initial advancement. The mean net effect at T5 on the labial fold (soft tissue point B) was 94 per cent of the advancement at point B. For the soft tissue chin (soft tissue pogonion), it was 119 per cent of the advancement at pogonion. The net effect on the lower lip (labrale inferior) was 55 per cent of the advancement at incision inferior. The amount of the surgical advancement of the mandible was correlated with the long-term relapse in point B. Among possible reasons for this relapse are the initial soft tissue profile, the initial growth direction, and the remodelling processes of the hard tissue.     

Neurosensory and functional impairment in sagittal split osteotomies: a longitudinal and long-term follow-up study

The aim was to conduct a long-term follow-up study on the function and sensitivity of the mandible in advancement and setback patients after bilateral sagittal split osteotomy (BSSO) with rigid internal fixation. The advancement and setback groups consisted of 16 (12 females and 4 males, mean age: 21.4 and 21.3 years, respectively) and 17 (11 females and 6 males, mean age: 27.1 and 27.7 years, respectively). The final follow-up was a mean of 12.7 years (T4) post-operatively. The other follow-up examinations were before surgery (T1) and 7.3/6.6 (T2) and 13.9/14.4 (T3) months after surgery. To evaluate craniomandibular function, mouth-opening capacity, laterotrusion, protrusion, deviations during opening, pain and clicking of the temporomandibular joint (TMJ), muscular pain, and the retruded contact position-intercuspal position (RC-IP) distance were examined. A questionnaire was used to record subjective reports. The neurosensory status was determined with two-point discrimination (2-pd), the pointed, blunt, and light-touch tests. Statistical analysis included the following tests: Wilcoxon signed ranked matched pairs, Mann-Whitney U, paired t, and Fisher's exact test. Bonferroni's adjustments were made for evaluation of the questionnaire and Spearman's rank correlation coefficients to determine the interdependence of selected variables. Craniomandibular function showed restitution at T4 after 12.7 years. The 2-pd at the lip and chin had largely normalized in the two groups at T3. At T4, there was a significant increase of 2-pd at the lip and chin in both groups. The discrimination between sharp and blunt was limited in both groups in 25 per cent of patients at T4. Dysfunctions such as TMJ clicking, bruxism, and pain in the TMJ and muscles were neither increased nor decreased after BSSO. The initial post-surgical neurosensory impairment was barely detectable 1 year post-surgery. The new neurosensory impairment manifested at T4 was probably due to the normal human process of ageing. Neither age, gender, surgical advancement, nor setback showed any significant correlations.     

Stability of intraoral vertical ramus osteotomies for mandibular setback: a longitudinal study

This study aimed to investigate the postoperative longitudinal skeletal changes and stability following intraoral vertical ramus osteotomies (IVRO) for orthognathic mandibular setback, and the possible risk factors that might affect the stability. A retrospective cohort study was conducted. Lateral cephalograms were analyzed for the predictor (magnitude of setback and adjunctive procedures) and outcome (stability of vertical and horizontal dimensions) variables at six time points. A total of 152 patients (mean age 24.2 years) were included in the study. Following IVRO, the mandible measured at B-point had moved a mean 0.50 mm posteriorly at 1 week after the removal of intermaxillary fixation (7 weeks postoperative); this was followed by progressive small anterior relapse. At 2 years postoperative, the mean relapse of the mandible after IVRO measured at B-point was 0.05 mm (standard deviation 1.14 mm), representing 0.7% of the mean surgical movement. Large setback (>8 mm) showed significantly higher relapse compared to small setback (<4 mm) at 2 years after surgery (P = 0.021). Patients who underwent adjunctive mandibular surgeries other than IVRO showed no significant differences in relapse compared to those who underwent IVRO alone. In conclusion, IVRO for mandibular setback is a stable procedure in the long term, with small relapse of 0.05 mm after 2 years.     

Long-term stability of mandibular setback surgery: a follow-up of 80 bilateral sagittal split osteotomy patients

The objective of this cephalometric study was to evaluate skeletal stability and time course of postoperative changes in 80 consecutive mandibular prognathism patients operated with bilateral sagittal split osteotomy (BSSO) and rigid fixation. Lateral cephalograms were taken on 6 occasions: immediately preoperative, immediately postoperative, 2 and 6 months postoperative, and 1 and 3 years postoperative. The results indicate that BSSO with rigid fixation for mandibular setback is a fairly stable clinical procedure. Three years after surgery, mean relapse at pogonion represented 26% of the surgical setback (19% at point B). Most of the relapse (72%) took place during the first 6 months after surgery. Clockwise rotation of the ascending ramus at surgery with lengthening of the elevator muscles, though evident in this study and apparently responsible for the early horizontal postoperative changes, does not seem to be associated with marked relapse. Changes occurring in some of the younger patients between 1 and 3 years postoperatively are likely to be manifestations of late mandibular growth.     

Comparative study of mandibular stability after sagittal split osteotomies: biocortical versus monocortical osteosynthesis.

OBJECTIVE: A comparative study of clinical mandibular stability following bilateral sagittal split osteotomies by means of monocortical versus bicortical osteosynthesis was undertaken. DESIGN: This retrospective study utilized cephalometric radiographs, which were taken at 1 week and 6 months postoperatively. SETTING: The research was carried out at the Department of Plastic and Reconstructive Surgery of the Nagasaki University School of Medicine. PATIENTS: A total of 32 patients who underwent only sagittal split osteotomies and mandibular set back in our unit was included in this study. Of these patients, 17 patients were osteosynthesized monocortically, and 15 patients were osteosynthesized bicortically. Main Outcome Measures: Four measurements--gonial angle (GA), mandibular plane (MP), SNB, and percentage of upper face to total face height (percent upper to total face)--were completed to evaluate postoperative mandibular movement. RESULT: Statistical analyses of cephalometric measurements (GA, MP, SNB, and percent upper face to total face height) showed that monocortical fixed mandibles were more changeable postoperatively on the GA and percent upper face to total face height, but MP and SNB showed no significant differences among the groups. CONCLUSION: These findings suggested that the postoperative excessive shear force stress, produced by the compressive action of the masseter muscle, transformed the mandibular shape as the distal segment rotated clockwise and proximal segment rotated counterclockwise. Consequently, the mandible was bent at the miniplate. It was concluded that bicortical osteosynthesis was more rigid against this shearing stress than monocortical osteosynthesis.     

Long-term airway space changes after mandibular setback using bilateral sagittal split osteotomy

Eleven patients were evaluated retrospectively for their long-term changes in hypopharyngeal airway space after surgical correction of mandibular hyperplasia. All patients had undergone mandibular setbacks by way of bilateral sagittal split osteotomies using rigid fixation. The cephalometric evaluation of hypopharyngeal airway space was based on stable craniofacial landmarks. The results of this study indicate that mandibular setback procedures create relative narrowing of the hypopharyngeal airway space, as seen on lateral cephalometric radiographs, which in isolated cases might contribute to the development of an obstructive sleep apnea syndrome. The 2-dimensional evaluation of hypopharyngeal airway space and the clinical implications of the results are discussed.     

Stability of transient, semirigid pin fixation of sagittal split mandibular osteotomies.

Cephalometric records of 16 patients who underwent mandibular lengthening, stabilized with noncompressive pin fixation, were examined retrospectively. Digitization and computer analyses of the cephalometric changes for various time intervals were performed. All linear changes were stable for 13 of the 16 patients over the follow-up period of 2 years. No significant correlation was found between postoperative horizontal relapse and amount of advancement. A high degree of postfixation stability was obtained with very short fixation periods. While further study of this pin fixation technique is indicated, these preliminary results are favorable.     

Skeletal stability after mandibular advancement in bilateral sagittal split osteotomies during adolescence

Bilateral sagittal split osteotomy (BSSO) is the most frequently performed surgery for correcting mandibular retrognathia. Few studies have reported the use of BSSO in young patients, as growth may cause relapse. The aim of the present study was to determine the amount of relapse after performing BSSO in patients aged less than 18 years. Patients who had a mandibular advancement by BSSO surgery between January 2003 and June 2008 were evaluated. Eighteen patients were treated before the age of 18 years and compared with patients treated at 20–24 years of age. Cephalometric radiographs were used to determine the amount of relapse. For patients aged less than 18 years, the mean horizontal relapse after 1 year was 0.5 mm, (10.9% of perioperative advancement). For patients aged 20–24 years, the mean relapse was 0.9 mm, (16.4% of perioperative advancement). There were no significant differences between the age groups (p > 0.05). In conclusion, the BSSO procedure is a relatively stable procedure, even during adolescence.     

Mandibular setback by sagittal split ramus osteotomy: a 12-year follow-up

Short- and long-term skeletal changes after mandibular setback were analyzed using bilateral sagittal split ramus osteotomy. Twelve patients who had undergone mandibular setback surgery between 1986 and 1990 were available for long-term cephalography on average 12 years after primary surgery. The mean amount of surgical setback had been 6.4 mm. After the first postoperative year, there was skeletal relapse of 1 mm at the B-point and pogonion (Pg), amounting to 14% of the initial skeletal setback. In contrast to condylar displacement and proximal segment rotation, osteotomy slippage was associated with positional changes at the B-point and Pg. From 1 to 12 years postoperatively, the B-point and Pg remained stable. Mandibular ramus and corpus length decreased 2.1 mm and 1.3 mm, respectively, indicating remodeling at the osteotomy sites and probably condylar resorption.     

双侧升支矢状劈开截骨后退下颌术后骨的稳定性的研究

目的：探讨双侧升支矢状劈开截骨术（BSSRO）后退下颌骨以钢丝结扎固定两骨段加颌间固定术后骨的稳定性，了解导致复发的有关因素。方法：双侧下颌升支矢状劈开截骨手术后退下颌的患者14例，于手术前1周，手术后1周，术后6个月分别拍摄定位头颅侧位片及许勒位X线片，用于测量下颌移动的距离及确定下颌骨髁状突的位置。结果：双侧下颌升支矢状劈开截骨后退术后，6个月的复发率为27.2%，多元逐步回归分析示下颌后退的距离与复发相关。结论：BSSRO后退下颌骨的距离越大，术后下颌骨向前移位的可能越大。     

Physiological positioning strategy alters condylar position after mandibular ramus sagittal split osteotomies for mandibular prognathism

Objective: The aim of this study was to elucidate the physiological position of the proximal segment for postoperative jaw movement in patients with mandibular prognathism.

Methods: Twenty-two patients with mandibular prognathism were treated by orthognathic surgery using bilateral mandibular sagittal split ramus osteotomies (SSRO) with a physiological positioning strategy. The skeletal stability was assessed, and the movement of the proximal segment was evaluated by cephalography and computed tomography performed preoperatively, immediately postoperatively, and one year postoperatively.

Results: The patients were divided into two groups: the stable group (SNB relapse <1.5°) and the relapse group (SNB relapse ≥1.5°). In the stable group at one year postoperatively, the average SNB relapse was only 0.29° (7%), the condylar head had moved posteriorly by 0.75 mm, and the proximal segment had rotated counterclockwise by 1.2°.

Conclusion: This new physiological positioning strategy improves the position of the condyle compared with the preoperative position in patients with mandibular prognathism.     

Resorbable PLLA-PGA screw fixation of mandibular sagittal split osteotomies.

The purpose of this study was to evaluate the intraoperative placement and clinical effectiveness of resorbable copolymeric screws for mandibular sagittal split ramus osteotomies. Thirty-seven patients who underwent bilateral sagittal split osteotomies of the mandible were fixated with three 2.5-mm copolymeric poly-L-lactic-polyglycolic (PLLA-PGA) screws on each side. No postoperative maxillomandibular fixation was applied. Twenty-five patients experienced mandibular advancement and 12 patients had setbacks. The average advancement was 6.5 mm (range, 3-17 mm) and the average set-back was 5.2 mm (range, 3-8 mm). Intraoperative placement was uncomplicated and no screws were stripped during placement. No problems in immediate postoperative stability were encountered and relapse was not evident in any patient. Follow-up ranged from 3 to 17 months. The screw holes remained evident radiographically after 1 year. Two and one-half-millimeter copolymeric PLLA-PGA resorbable screws for mandibular ramus osteotomies appear to offer clinical results comparable with metallic screw fixation.     

Control of the condylar-proximal mandibular segments after sagittal split osteotomies to advance the mandible

Maintenance of the normal or presurgical anatomic position of the mandibular condyles and contiguous proximal mandibular ramus segments after sagittal split ramus osteotomies is important, not only to enhance the stability of results but also to avoid iatrogenic temporomandibular joint complications. Accordingly, during the past few years, we have attempted to improve the surgical control of condyle and proximal segment position while using the sagittal split ramus osteotomy to advance the mandible. After several modifications, the device reported herein was used and the results evaluated in ten consecutive patients who underwent bilateral sagittal split ramus osteotomies with symmetric advancement of the mandible. This device enables the surgeon to obtain very precise reproduction of the "normal" proximal segment and condyle position at the time of surgery. The use of the device and documentation of its efficiency are presented.     

A retrospective analysis of the stability and relapse of soft and hard tissue change after bilateral sagittal split osteotomy for mandibular setback of 64 Taiwanese patients.

PURPOSE: This study was an analysis of the soft and hard tissue changes of the facial profile after bilateral sagittal splitting osteotomy for mandibular setback of Taiwanese patients. PATIENTS AND METHODS: We collected pre- and postsurgical lateral cephalographs of 64 patients (28 males, 36 females) with skeletal Class III malocclusion who received combined orthodontic-surgical treatment with bilateral sagittal splitting osteotomy mandibular setback at Taipei Veterans General Hospital between 1994 and 2000. Nineteen cephalometric parameters of (14 linear, 4 angular, and the BS index) soft and hard tissues were measured at 1 week before treatment, and 2 months and 1 year after surgery, and analyzed by paired t test. RESULTS: Mean patient age was 20.0 +/- 1.6 years. The patients underwent an average of 7 mm mandibular setback at the osseous pogonion (Pog). Average setbacks at Pog and soft tissue pogonion (pog) were 5.54 mm and 4.85 mm, respectively, at 1 year after surgery. The setback ratio of Pog/pog was 1:0.88. The hard tissue relapse at Pog was 21% at 1 year after surgery. Improvement in prognathic profile was demonstrated by significant changes in the positions of Pog and pog, ANB angle, the distance from lower lip to esthetic line (E-L lip), and the BS index after surgery. However, compared with parameters obtained from a normal Taiwanese population, the cephalometric data of Pog, pog, and BS index still indicated mild prognathism. CONCLUSION: Although mandibular prognathism could be grossly improved by bilateral sagittal splitting osteotomy mandibular setback, a significant amount of relapse occurred within 1 year after surgery. The extent of the postoperatively preserved features showing mandibular prognathism should be a concern for both patients and physicians.     

Risk factors for breakage of biodegradable plate systems after bilateral sagittal split mandibular setback surgery

The aim of this retrospective study was to evaluate the risk factors associated with breakage of biodegradable plate systems after bilateral sagittal split mandibular setback. We studied 169 Japanese adults (62 men, 107 women; age range 16–53 years) with deformities of the jaw diagnosed as mandibular prognathism. All patients were treated by bilateral sagittal split osteotomy (BSSO) with 2 biodegradable fixation plates and screws at the anterior mandibular ramus. We collected the following data from the medical records and radiological findings: sex; age; degree of setback; presence of asymmetry; presence of open bite; operation; design of the plate; operating time; and blood loss. Multiple logistic regression analysis was used to find the factors that were independently associated with the dependent variable: breakage of the biodegradable plate system. In 10 of the 169 patients (6%) the biodegradable plate system for the BSSO broke. Factors that influenced whether or not the biodegradable plate system fractured were if they were asymmetrical (odds ratio (OR) 5.35; P = 0.02) and had an open bite (OR 5.20; P = 0.02). Asymmetry or open bite was significantly associated with breaks in the biodegradable plate system. Biodegradable plates should be used only when loading is minimal.     

Biomechanical testing of resorbable screws used for mandibular sagittal split osteotomies

PURPOSE: The object of the study was to determine the suitability of specific resorbable screws for fixation of mandibular sagittal split osteotomies by in vitro biomechanical strength testing. MATERIALS AND METHODS: Resorbable screws (2.5 mm diameter) composed of a polylactic acidpolyglycolic acid copolymer were placed in an inverted L-pattern in overlapping urethane blocks representative of sagittal split mandibular surgery. In an in vitro model at room temperature, the test specimens were statically loaded until tensile failure occurred. On a different set of test specimens, dynamic testing was done in an in vitro water bath at body temperature through cyclic loads representative of mastication until failure. RESULTS: In static testing, three 2.5-mm resorbable screws sustained an average peak load of 131 Kiloponds (Kp) (standard deviation, 5.2 Kp) with 5.5% strain at yield. In dynamic testing, the resorbable screws tolerated a 45.3-Kp load for an average of 340,675 cycles (22,783 standard deviation). Several of these test specimens did not ultimately fail and were further evaluated by static testing with an average load of 77.4 Kp until fixation failure occurred. CONCLUSIONS: These laboratory results indicate a relatively high resistance to biomechanical loads representative of mastication and suggest that 2.5-mm resorbable screws of this particular polylactic acid-polyglycolic acid copolymer may be effective in fixation of the postoperative unrestrained sagittal split mandibular osteotomy.     

Transverse stability of the proximal segment after bilateral sagittal split ramus osteotomy for mandibular setback surgery

This study aimed to evaluate the correlation between the transverse displacement of the proximal segment after bilateral sagittal osteotomy for mandibular setback and the amount and design of the mandibular setback. Patients who underwent either bilateral sagittal split ramus osteotomy (BSSRO) alone or two-jaw surgery were selected, and cephalographic postero-anterior (PA) measurements were taken pre-operatively (T1), immediately post-operatively (T2), and at follow-up (T3). The inter-gonal (IG) and inter-ramal (IR) width increased immediately after surgery, but decreased to the initial value during follow-up (P = 0.002; IR, P = 0.046). Only the immediate IG changes after surgery correlated with the amount of mandibular setback (P = 0.009). The IG changes were significant in the symmetric group, but not in the asymmetric group. There was no difference in the IG and IR changes between the symmetric group and the asymmetric group. The immediate IG change in two-jaw patients with symmetric setback showed correlation with the setback amount. The gonial width of the deviated group showed more significant changes than that of the non-deviated group. There was no difference in the unilateral gonial width between the deviated and the non-deviated group, but the difference was significant for the unilateral ramal angle between the two groups. These correlations will be helpful in predicting post-surgical results for patients.