Skeletal stability after mandibular advancement with rigid versus wire fixation.

PURPOSE: This study examined the stability of skeletal changes after mandibular advancement surgery with rigid or wire fixation up to 2 years postoperatively. PATIENTS AND METHODS: Subjects for this multisite, prospective, clinical trial received rigid (n = 78) or wire (n = 49) fixation. The rigid cases were fixed with three 2-mm bicortical position screws and 1 to 2 weeks of skeletal maxillomandibular fixation with elastics, and the wire fixation subjects were fixed with inferior border wires and had 6 weeks of skeletal maxillomandibular fixation with 24-gauge wires. Cephalometric radiographs were obtained before orthodontics, immediately before surgery, and at 1 week, 8 weeks, 6 months, 1 year, and 2 years after surgery. Linear cephalometric changes were referenced to a cranial base coordinate system. RESULTS: Before surgery, both groups were balanced with respect to linear and angular measurements of craniofacial morphology. Mean anterior sagittal advancement of the mandibular symphysis was 4.92 +/3.01 mm in the rigid group and 5.11 +/- 3.09 mm in the wire group, and the inferior vertical displacement was 3.37 +/- 2.44 in the rigid group and 2.85 +/- 1.78 in the wire group. The vertical changes were similar in both groups. Two years postsurgery, the wire group had 30% sagittal relapse of the mandibular symphysis, whereas there was no change in the rigid group (P < .001). Both groups experienced changes in the orientation and configuration of the mandible. CONCLUSIONS: Rigid fixation is a more stable method than wire fixation for maintaining mandibular advancement after sagittal split ramus osteotomy.     

A 3-year evaluation of skeletal stability of mandibular advancement with rigid fixation

The postsurgical changes associated with mandibular advancements using the sagittal ramus osteotomy and rigid fixation were evaluated. This retrospective study was based on examination of lateral cephalometric radiographs of 19 individuals (16 females and 3 males) with a mean age of 26.6 years. These radiographs were evaluated presurgically, immediately postsurgery, and 3 years postsurgically (2 years, 9 months to 4 years, 5 months). The mean amount of sagittal surgical advancement was 6.7 +/- 2.3 mm, and the mean amount of postsurgical relapse was 1.3 +/- 2.0 mm, representing a 14% relapse of the original surgical advancement. However, individual variation in the amount and direction of movement of the mandible was found during the follow-up period. Postsurgical relapse was found to be related to the amount of surgical advancement. Linear-regression analysis between these two variables resulted in an R2 value of 0.448. Fourteen of the subjects relapsed in the posterior direction, with 2 relapsing more than 50% of the surgical advancement. Five of the subjects moved further anteriorly, with 1 advancing as much as 50% more than the original advancement. The findings of this study suggest that mandibular advancement with the sagittal ramus osteotomy and rigid fixation does not provide consistently stable postsurgical results. However, when compared with previously reported relapse studies using nonrigid fixation techniques, rigid fixation yielded superior results.     

Skeletal stability following mandibular advancement and rigid fixation

Twenty non-growing subjects underwent sagittal ramus osteotomies and rigid fixation. Cephalograms were analyzed before surgery, immediately after surgery and at least six months following surgery to evaluate skeletal stability. A mean horizontal relapse of 0.42 mm (8%) and a mean vertical increase in lower face height of 0.2 mm were found six months after surgery. Both were statistically insignificant. The mean backward rotation of the mandible of 0.55 degrees found six months after surgery was statistically significant (P less than 0.015), but was considered to be clinically insignificant. The results of this study show that surgical mandibular advancement with rigid fixation is a very reliable and stable procedure.     

Relapse following mandibular advancement with dental plus skeletal maxillomandibular fixation

This study examines the short-term stability of the mandible following mandibular advancement surgery in which skeletal suspension wires were used in addition to dental maxillomandibular fixation. Twenty adults underwent sagittal ramus osteotomies. No concomitant surgical procedures were performed. Maxillomandibular fixation consisted of wiring between the upper and lower orthodontic brackets and circummandibular wires connected to the piriform aperture or anterior nasal spine wires for eight weeks. Cephalograms were analyzed during this period to evaluate skeletal stability. A statistically insignificant mean horizontal relapse of 8.9% was found at pogonion during the period of fixation. Significant vertical intrusion of the anterior mandible occurred, however, with a mean superior movement of pogonion of 0.83 mm (P less than or equal to 0.05). Dental changes noted were uprighting of the maxillary incisors and flaring of the mandibular incisors. In comparison with the results of other studies in which dental maxillomandibular fixation was used alone, the results of this study indicate that the use of skeletal suspension wires is advantageous in the prevention of horizontal 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.     

Neurosensory differences after wire and rigid fixation in patients with mandibular advancement.

PURPOSE: The purpose of this analysis was to compare the frequency and severity of nerve damage with rigid and wire fixation in patients participating in a prospective, randomized clinical trial. PATIENTS AND METHODS: One hundred twenty-six patients who required a bilateral sagittal split osteotomy and mandibular advancement were randomly assigned to receive either rigid or wire fixation. Tactile sensation in the mental nerve region bilaterally was determined presurgically and throughout the subsequent 2 years by using monofilament detection and brush stroke direction. Neurosensory levels were compared between the types of fixation over time. RESULTS: Evaluation with monofilament detection showed no significant difference between types of fixation throughout the 2-year follow-up. However, brush stroke determination showed significantly greater hypesthesia with rigid compared with wire fixation from 8 weeks through 2 years postoperatively. CONCLUSION: Rigid fixation resulted in more anesthesia in the mental nerve distribution than wire fixation when tested with brush stroke direction. However, increased anesthesia was not present when measured with monofilament determination.     

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.     

A comparison of skeletal and dental changesbetween rigid and wire fixation for bilateral sagittal split osteotomy

For two years, this multisite prospective clinical trial examined longitudinalskeletal and dental changes after bilateral sagittal split osteotomy for mandibular advancement in which either rigid or wire fixation was used. Subjects in the rigid fixation group (n = 78) received 2-mm bicortical position screws, while the subjects in the wire fixation group (n = 49) received inferior border wires. Skeletal and dental changes were measured from cephalometric films taken immediately before surgery, one week after surgery, and at eight weeks, six months, one year, and two years after surgery. In both groups, the overbite and overjet increase with time, but were not different from each other. The B-point in the wire group progressively moved posteriorly, and at two years, it had relapsed 28%. In the rigid fixation group, there was a transient anterior movement of the B-point during the first six months and by two years after surgery, the B-point was unchanged from immediate post surgery. Dental changes occurred in both groups. These changes, however, were not able to accommodate the skeletal changes, resulting in similar increases in both overbite and overjet in both groups of patients. These results have implications for the orthodontists in management of the postmandibular advancement occlusion.     

Rigid versus wire fixation for mandibular advancement: Skeletal and dental changes after 5 years

The bilateral sagittal split osteotomy (BSSO) is the most common surgical procedure for the correction of mandibular retrognathism. Commonly, the proximal and distal segments are fixated together with either wire or rigid screws or plates. The purpose of this study was to compare long-term (5 years) skeletal and dental changes between wire and rigid fixation after BSSO. In this multisite, prospective, randomized clinical trial, the rigid fixation group received three 2-mm bicortical position screws, and the wire fixation group received inferior border wires and 6 weeks of skeletal maxillomandibular fixation with 24-gauge wires. Cephalometric films were obtained 2 weeks before surgery and at 1 week, 8 weeks, 6 months, 1 year, 2 years, and 5 years after surgery. Linear cephalometric changes were referenced to a cranial base coordinate system. Before surgery, both groups were comparable with respect to linear and angular measurements of craniofacial morphology. Both groups underwent similar surgical changes. Skeletal and dental movements occurred in both groups throughout the study period. Five years after surgery, the wire group had 2.2 mm (42%) of sagittal skeletal relapse, while the rigid group remained unchanged from immediately postsurgery. Surprisingly, at 5 years, both groups had similar changes in overbite and overjet. This was attributed to dental changes in the maxillary and mandibular incisors. Although rigid fixation is more stable than wire fixation for maintaining the skeletal advancement after a BSSO, the incisor changes made the resultant occlusions of the 2 groups indistinguishable.     

Stability of mandibular advancement after sagittal osteotomy with screw or wire fixation: a comparative study

Stability and clinical results in 70 patients who underwent bilateral sagittal ramus osteotomy for mandibular advancement were studied. The patients were grouped by the method of fixation (screws vs. wire) and matched for the amount of advancement. There were 35 patients in each group, and the age, sex, and presurgical mandibular plane angle distributions were similar for the two groups. Although the pattern of skeletal and dental changes during the first postsurgical year were quite different for the groups, stability, incisal opening, and clinical results were equivalent at 1 year following surgery. In the first 6 weeks postsurgery, the screw fixation group was more stable horizontally and vertically than the wire group, but between 6 weeks and 1 year, the wire group showed recovery, and the mean differences all but disappeared.     

A comparative study of temporomandibular symptoms following mandibular advancement by bilateral sagittal split osteotomies: rigid versus nonrigid fixation

Rigid fixation to attach proximal and distal segments during bony healing of osteotomy sites has become increasingly popular. The effects of rigid fixation on the temporomandibular joints have been questioned. The purpose of this study was to evaluate the effects of rigid fixation after bilateral sagittal split osteotomies on temporomandibular dysfunction symptoms. Forty patients who had mandibular advancement surgery were evaluated for temporomandibular joint dysfunction. Twenty had received rigid fixation, and twenty had received nonrigid fixation. It was determined that there was no statistically significant difference in temporomandibular signs or symptoms between patients who were treated with rigid internal fixation for bilateral sagittal split osteotomies for mandibular advancement and those patients who were treated with nonrigid wire fixation.     

Maintenance of soft tissue changes after rigid versus wire fixation for mandibular advancement, with and without genioplasty

OBJECTIVE: This multisite prospective randomized clinical trial examined 2-year longitudinal soft tissue profile changes after bilateral sagittal split osteotomy for mandibular advancement by using rigid or wire fixation, with and without genioplasty. STUDY DESIGN: The study sample consisted of 127 subjects. The rigid-fixation group (n = 78) received 2-mm bicortical position screws, whereas the wire-fixation group (n = 49) received inferior border wires. In the rigid-fixation group, 35 subjects underwent genioplasty, whereas 24 subjects underwent genioplasty in the wire-fixation group. Soft tissue profile changes of labrale inferius, B-point, and pogonion were obtained from digitized cephalometric films taken immediately before surgery and up to 2 years after surgery. RESULTS: Regardless of fixation technique, subjects who had genioplasty in conjunction with the mandibular advancement had the largest surgical movement and the largest postsurgical change (P <.05). When all variables were constant, fixation technique was associated with maintenance of soft tissue change. Subjects who underwent rigid fixation maintained more soft tissue change than patients who underwent wire fixation. CONCLUSIONS: These findings suggest that subjects undergoing rigid fixation and genioplasty maintained the most soft tissue advancement.     

Stability of mandibular advancement osteotomy using rigid internal fixation

Forty-three patients who underwent surgical lengthening of the mandible using an inverted L osteotomy, bone grafting, and rigid internal fixation between the mandibular segments were evaluated by retrospective cephalometric analysis for longitudinal skeletal and dental changes. Postoperative response (means = 1 year 9 months) was found to demonstrate a high level of stability with some individual variability. No propensity for relapse was observed in any postoperative time interval. Condylar repositioning postoperatively appeared to be an important factor in those patients who exhibited any relapse tendency. Overall postoperative stability of this surgical/fixation technique appears to be significantly improved compared with previously documented techniques.     

The influence of functional orthodontics and mandibular sagittal split advancement osteotomy on dental and skeletal variables--a comparative cephalometric study

Lateral head films of 200 Class II patients (106 females, 94 males) with a mean pre-treatment age range of 9.9-10.25 years successfully treated with functional orthodontics were analysed before (T1) and after (T2) treatment. The resulting data and findings were compared with lateral head films (T1, T2) of 20 patients (15 females, five males) with a mean pre-treatment age of 25.75 years whose Class II malocclusion and antero-posterior jaw discrepancy had been corrected by a mandibular sagittal split advancement osteotomy. The median and interquartile distances were calculated for every variable, at T1 and T2. The difference between the medians (T2-T1) was analysed using a signed rank test. The changes in scattering (T2-T1) were assessed by means of a F-test. Significant differences regarding the therapeutic influence on skeletal [ANB, Wits, Index, mandibular line-nasal line (ML-NL)], functional (beta', mu), and dental (1-NA degrees , 1-NB degrees ) variables were found. In the group initially treated with functional appliances in order to enhance mandibular prognathism, the antero-posterior (A-P) jaw discrepancy was reduced (ANB, Wits). The vertical skeletal pattern (Index) changed towards a more skeletal open relationship, whereas the ML-NL angle was reduced, which indicates a deepening of the bite. The comparison between biomechanical incisor position analysis (beta', mu) and dental variables (1-NA degrees , 1-NB degrees ) revealed different changes in incisor inclination depending on the type of analysis used. The findings for the dental variables (1-NA degrees , 1-NB degrees ) showed a protrusion of both upper and lower incisors after therapy. The results for the functional variables (beta', mu) showed a retrusion of the upper and a protrusion of the lower incisors. This change in incisor inclination is a dental compensation of the remaining sagittal jaw discrepancy. This effect is most clearly reflected by the functional analysis and the changes of the biomechanical variables beta' and mu. For the orthognathic surgery group, a clear improvement in the dental and skeletal relationship was observed: the skeletal discrepancies in the A-P plane were completely corrected (ANB, Wits) and the inclination of the incisors according to biomechanical and functional aspects was optimized (beta', mu).The alteration in both the Index and ML-NL angle in this group indicated an increase of the open bite components.     

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.     

Comparison of postoperative stability of three rigid internal fixation techniques after sagittal split ramus osteotomy for mandibular advancement

IntroductionThe aim of this investigation was to compare the skeletal stability of three different rigid fixation methods after mandibular advancement.Material and methodsFifty-five class II malocclusion patients treated with the use of bilateral sagittal split ramus osteotomy and mandibular advancement were selected for this retrospective study. Group 1 (n = 17) had miniplates with monocortical screws, Group 2 (n = 16) had bicortical screws and Group 3 (n = 22) had the osteotomy fixed by means of the hybrid technique. Cephalograms were taken preoperatively, 1 week within the postoperative care period, and 6 months after the orthognathic surgery. Linear and angular changes of the cephalometric landmarks of the chin region were measured at each period, and the changes at each cephalometric landmark were determined for the time gaps. Postoperative changes in the mandibular shape were analyzed to determine the stability of fixation methods.ResultsThere was minimum difference in the relapse of the mandibular advancement among the three groups. Statistical analysis showed no significant difference in postoperative stability. However, a positive correlation between the amount of advancement and the amount of postoperative relapse was demonstrated by the linear multiple regression test (p < 0.05).ConclusionIt can be concluded that all techniques can be used to obtain stable postoperative results in mandibular advancement after 6 months.     

Technical factors accounting for stability of a bilateral sagittal split osteotomy advancement: wire osteosynthesis versus rigid fixation

OBJECTIVE: Relapse after bilateral sagittal split osteotomy has been attributed to various technical factors that are inherent in the surgical procedure. The purpose of this article was to analyze technical factors that predispose to relapse when wire or rigid fixation is used. STUDY DESIGN: Patients were randomized to either rigid or wire osteosynthesis. Cephalometric radiographs were obtained and digitized at multiple time periods before and after surgery. Data were analyzed through use of 2-sample t tests and stepwise regression analyses. RESULTS: Multivariate analysis indicated that the following factors correlated with relapse: initial advancement, change in ramus in inclination, change in the mandibular plane, and fixation type. CONCLUSIONS: Relapse increased with the amount of initial advancement and, to a lesser extent, with control of the proximal segment and change in the mandibular plane. These factors are similar for wire osteosynthesis and rigid fixation.     

A comparison of stimulated bite force after mandibular advancement using rigid and nonrigid fixation

This study evaluated maximum stimulated molar bite force following advancement of the mandible in 17 adult Macaca mulatta using rigid and nonrigid fixation techniques. Cephalometric analysis was also performed to determine the amount of proximal segment rotation. Analysis of the bite force showed the animals whose mandibles were advanced using rigid fixation to have significantly greater bite force at six weeks postsurgery when compared to those animals who underwent mandibular advancement and six weeks of maxillomandibular fixation. By the ninth postoperative week, there was no longer any significant difference between the two groups, indicating a rapid recovery of muscle function in the animals whose mandibles were immobilized following advancement. Both groups, however, had significant decreases in bite force at 12 weeks postsurgery when compared to preoperative values. Neither group had a significant amount of proximal segment rotation from the surgery.