Neurosensory disturbances one year after bilateral sagittal split mandibular ramus osteotomy performed with separators

Examination of the Safe Zone in Mandibular Ramus Osteotomies

ABSTRACT

In the surgical procedures such as osteotomy to be applied to ramus of the mandible, care should be taken not to damage the inferior alveolar nerve (IAN). The safe zone, which is the area above and behind the mandibular foramen (MF), is the ramus of mandible area, where these surgeries can be performed without damaging the inferior alveolar neurovascular bundle. It was aimed to determine the safe zone in the ramus of mandible in the cone-beam computed tomography (CBCT) images of individuals. The CBCT images of 300 Turkish individuals between the ages of 18 to 65 were bilaterally and retrospectively evaluated. Three parameters on the sagittal and two parameters on the axial plane were measured. Additionally, two ratios were calculated which determined the superior and posterior part of the safe zone through the measured parameters. In this study, the safe zone was determined as the area where 55% of the upper part and 49% of the posterior part of the mandibular ramus. Determining the safe zone in surgical procedures to be applied to the ramus of mandible will help protect the neurovascular structures passing through the MF, reduce complications and increase the success rate of the surgical procedure. However, it is seen that there are few studies on this subject in the literature and there are some differences between these studies. The authors think that preoperative CBCT screening will be safer for each patient in the mandibular ramus osteotomies and more studies should be done on different populations to determine standard values.

Long-term neurosensory disturbances after modified sagittal split osteotomy

We have investigated the long-term incidence of neurosensory disturbances after modified bilateral sagittal split osteotomy, and identified associated risk factors. We prospectively studied 376 patients, and their self-reported neurosensory disturbances were evaluated six months, and one, two, and three years postoperatively. The correlations between the following risk factors and neurosensory disturbances were investigated using univariate analysis and stepwise multivariate analysis: age at operation, sex, type of movement (advancement, setback, or rotation), concurrent genioplasty, type of detachment, iliac crest bone graft, and use of dicalcium phosphate synthetic bone graft. Probabilities of less than 0.05 were accepted as significant. Three years postoperatively, 57 patients (15%) reported altered sensation of the lower lip or chin. Older age correlated significantly with neurosensory disturbances (p<0.0001). Greater mandibular advancement correlated with postoperative "positive" neurosensory phenomena (right side p=0.08; left side p=0.03). Intraoperative surgical manipulation of the left inferior alveolar nerve was significantly associated with postoperative hypoaesthesia (p=0.014). Older age at surgery, extensive mandibular advancement, and surgical manipulation of the left inferior alveolar nerve, were associated with long-term neurosensory disturbances after modified bilateral sagittal split osteotomy. The modified operation seems to safeguard the inferior alveolar nerve from transection, without causing damage to other nerves.

The Impact of the Use of Kinesio Taping Method on the Reduction of Swelling in Patients After Orthognathic Surgery: A Pilot Study

BACKGROUND Orthognathic surgery (OGS) is associated with extensive surgical intervention within the soft and hard tissues of the facial region of the skull leading to inflammatory reactions. The presence of postoperative swelling indicates the accumulation of exudate or transudate; both these fluids occur in surgery. Massive swelling is a significant problem, because the tension of tissues intensifies pain sensations. The aim of the study was to evaluate the effectiveness of the kinesio taping method (KT) in patients after orthognathic surgery in the area of the facial skull in terms of eliminating postoperative swelling. MATERIAL AND METHODS The study of the impact of kinesiology tape applied after orthognathic surgery to the craniofacial area on the elimination of swelling was performed in sixteen patients who suffered from this complication after bilateral sagittal split osteotomy. RESULTS The swelling was shown to be reduced after KT; within the same study the differences were statistically significant between the left and right sides and for the same side (p<0.05). The application of the lymphatic kinesio taping method led to the reduction of tension in the affected area and restoration of proper lymphatic circulation in the region covered by swelling. This allows for the improvement of the blood and lymph microcirculation and activation of self-healing processes. CONCLUSIONS The analysis of the impact of the practical use of the lymphatic KT on complications after orthognathic surgery revealed that it had a beneficial effect on the reduction of swelling. The use of the KT method seems promising because it is simple to carry out, not traumatic, economical and rarely causes undesirable allergies.

Comparison of the Effects of Ultrasonic and Conventional Surgery on the Neurosensory Disturbance After Bilateral Sagittal Split Osteotomy

PURPOSE

According to the literature, ultrasonic surgery reduces the incidence of neurosensory disturbance (NSD) of the inferior alveolar nerve (IFAN) after bilateral sagittal split osteotomy (BSSO). The purpose of this study was to evaluate the effects of ultrasonic surgery and the anatomic position of the IFAN canal on NSD after BSSO.

PATIENTS AND METHODS

This retrospective cohort study included skeletal mandibular prognathism cases operated on with an ultrasonic bone scalpel or a reciprocating saw. The primary predictor variable was osteotomy technique (ultrasonic or conventional surgery). The primary outcome variable was NSD. Other variables included age, gender, operator, degree of setback, surgical duration, blood loss, and IFAN position. Comparisons of 2 variables were performed by use of the Student t test or Fisher exact test. A regression model was used to examine the relationship between the presence or absence of NSD and other variables. The level of significance was set at P < .05 for all statistical tests.

RESULTS

The ultrasonic group was composed of 35 patients, whereas the conventional group was composed of 32. Three months after surgery, NSD was observed on 16 of 70 sides (22.9%) in the ultrasonic group and 28 of 64 sides (43.8%) in the conventional group; this difference was significant. Furthermore, recovery from NSD at 3 months after BSSO was significantly more common in the ultrasonic group than in the conventional group. In the ultrasonic group, even when the distance from the buccal aspect of the IFAN canal to the outer buccal cortical margin was shorter, NSD of the IFAN was less frequent.

CONCLUSIONS

Ultrasonic surgery may be an effective technique to reduce the incidence of NSD after BSSO, and it contributed to recovery from NSD. The use of an ultrasonic device for BSSO is recommended when the distance from the buccal aspect of the IFAN canal to the outer buccal cortical margin is shorter on computed tomography.

Hypoesthesia associated with mandibular movement after sagittal split ramus osteotomy

PURPOSE

This retrospective study investigated the relationship between the degree of neurosensory disturbance (NSD) and mandibular movement distance after sagittal split ramus osteotomy (SSRO) and assessed sensory recovery.

METHODS

Lower lip hypoesthesia was evaluated at 1 week, 1 month, and 2 months after SSRO in 38 patients categorized according to the distance of mandibular movement: S group (0-7 mm; n = 17, 4 males and 13 females) and L group (7-14 mm; n = 21, 7 males, 14 females). Symptoms were evaluated by visual analog scale (VAS), tactile-threshold (SW) test, static 2-point discrimination (s-2PD) test, and current perception threshold (CPT) test.

RESULTS

The two groups did not differ significantly in gender and age. The Aβ fiber results of the CPT test differed significantly between the groups at 1 week and 1 month postsurgery (P < 0.05). There were no significant differences between the groups throughout the period in terms of VAS, SW, s-2PD, Aδ fiber, and C fiber of CPT.

CONCLUSIONS

Post-SSRO, the incidence of NSD in terms of tactile sensation may be greater in the L group early postoperatively. This may assist surgeons in explaining postoperative hypoesthesia to patients preoperatively.

Are there risk factors for osseous mandibular inferior border defects after bilateral sagittal split osteotomy?

PURPOSE

Bone defects of the inferior mandibular border (osseous inferior border defects) can cause unesthetic postoperative outcomes after bilateral sagittal split osteotomy (BSSO). The aim of this study was to estimate the frequency of osseous inferior border defects after BSSO and to identify risk factors for this complication.

MATERIALS AND METHODS

This retrospective study included consecutive patients who underwent BSSO for mandibular retrognathia. The primary outcome was the presence/absence of osseous inferior border defects. Predictors included the mandibular movement, rotation of the occlusal plane, postoperative proximal segment position, pattern of lingual fracture, occurrence of bad split, and presence of third molars.

RESULTS

The study sample consisted of 200 patients and had a mean follow-up of 13 months. The mean mandibular advancement and rotation was respectively 5.8 mm and 5.4° clockwise. Osseous inferior border defects were present in 7.0% of splits and in 12.5% of patients. Significant risk factors for inferior border defects included increased advancement, increased clockwise rotation, cranial rotation of the proximal segment, and a split originating in the lingual cortex.

CONCLUSION

In conclusion, osseous inferior border defects occur significantly more often in cases with large mandibular advancement, increased clockwise rotation of the occlusal plane, malpositioning of the proximal segment, and a split originating in the lingual cortex.

Effect of the use of combination uridine triphosphate, cytidine monophosphate, and hydroxycobalamin on the recovery of neurosensory disturbance after bilateral sagittal split osteotomy: a randomized, double-blind trial

The change in neurosensory lesions that develop after bilateral sagittal split osteotomy (BSSO) was explored, and the influence of the application of combination uridine triphosphate (UTP), cytidine monophosphate (CMP), and hydroxycobalamin (vitamin B12) on patient outcomes was assessed. This was a randomized, controlled, double-blind trial. The study sample comprised 12 patients, each evaluated on both sides (thus 24 sides). All patients fulfilled defined selection criteria. Changes in the lesions were measured both subjectively and objectively. The sample was divided into two patient groups: an experimental group receiving medication and a control group receiving placebo. The statistical analysis was performed using SPSS software. Lesions in both groups improved and no statistically significant difference between the groups was observed at any time. 'Severe' injuries in the experimental group were more likely to exhibit a significant improvement after 6 months. Based on the results of the present study, it is concluded that the combination UTP, CMP, and hydroxycobalamin did not influence recovery from neurosensory disorders.

The Role of Microfat Grafting in Facial Contouring

BACKGROUND

Congenital hypoplasia of facial bones has traditionally been treated by orthognathic surgery. However, the inherent invasiveness of orthognathic surgery often leads to a high complication rate. Facial fat grafting could be a less invasive method to correct facial deformities.

OBJECTIVES

The aim of this study was to evaluate the results of microfat grafting for facial contouring.

METHODS

This retrospective chart review evaluated 166 patients who were treated with microfat grafting for maxillary and/or mandibular hypoplasia. Pretreatment and posttreatment photographs were compared regarding improvement of facial contour, and complications were recorded.

RESULTS

The follow-up period ranged from 4 months to 10 years (mean, 2 years 7 months). Thirty-eight percent of the patients had a refill procedure 6 or more months after the first procedure. A majority of the evaluated patients stated that they benefited from the microfat grafting, with ratings of excellent (50%), sufficient (48%), and poor (2%). Complications included visible fat lobules under the lower eyelid skin (7%), which was seen during the first 4 years and was resolved by changing the injection cannulae and technique, and fat resorption, which was seen in all patients, with a clinical range from ±15% in the immobile malar area and chin region to ±50% in the mobile lip area.

CONCLUSIONS

Facial microfat grafting is a valuable alternative to more complicated advancement osetotomies being performed in patients solely for aesthetic reasons. The low morbidity and rapid recovery make facial microfat grafting a welcome tool in the armamentarium of the modern facial aesthetic surgeon.

Morphological features of the mandible as predictors for neurosensory disturbances after bilateral sagittal split osteotomy

This retrospective study aimed to identify anatomical predictors of neurosensory disturbance (NSD) after bilateral sagittal split ramus osteotomy (BSSO) by evaluating the morphology of the mandible on lateral cephalograms (LCs) and orthopantomograms (OPTs). The LCs and OPTs of 142 patients who underwent BSSO were reviewed. The influence of the mandibular angle was assessed on LCs, while the following morphological landmarks and subsequent measurements were analysed on OPTs: vertical and horizontal positions of the lingula, ramus width, mandibular body height, mandibular canal position and mandibular angle length. Post-operative NSD (hypoaesthesia) was considered permanent when objective tests or subjective evaluations indicated altered sensation one year after BSSO. Generalised linear mixed models were used to take into account the repeated measurement design (left and right measurements within one patient). Hypoaesthesia was present in 10.6% of the patients (5.6% of sites). After adjusting for age, a small mandibular body height was found to significantly increase the risk of hypoaesthesia. The other measurements showed no significant association with hypoaesthesia. These findings show a relationship between mandibular morphology and hypoaesthesia after BSSO and can aid surgeons in pre-operative assessments of the risk of NSD. Further research is needed to identify risk factors for NSD based on mandibular morphology.

Evaluation of neurosensory disturbance following orthognathic surgery: a prospective study

AIM AND OBJECTIVES

The prospective study was to evaluate the incidence, type of neurosensory disturbance (NSD), grade its severity and monitor its recovery occurring in the lower lip and chin due to damage to inferior alveolar nerve following orthognathic surgery involving mandible.

MATERIALS AND METHODS

The study included 10 patients who have undergone sagittal split osteotomy, genioplasty, and anterior subapical osteotomy (ASO). All the patients examined preoperatively and post operatively 1 week, 1 and 6 months according to standardized test to clarify the subjective and objective neurosensory status of the injured nerve. Pin prick test, blunt test, two-point discrimator test, brush stoke direction, light touch test, warm and cold test were used bilaterally to lower lip and chin area.

RESULTS

Seven patients underwent bilateral sagittal split osteotomy (BSSO) (70 %), one patient had BSSO with genioplasty (10 %), two patients had BSSO with ASO (20 %). During the operation none of the nerves were transectioned, in 60 % of patients nerve was not visible and in 40 % of patients nerve was seen in distal segment. 70 % of patients underwent setback, 30 % of patients underwent advancement. The subjective evaluation of the patients revealed the incidence of 90 % at 1 week, 30 % at 1 month, 20 % at 6 months and 10 % at 1 year post operatively. The altered sensation reported subjectively was hypoesthesia in 50 % of the patients, anaesthesia in 40 % of the patients. There was 100 % recovery in advancement cases and 93.5 % recovery in setback cases.

CONCLUSION

There is a high incidence of NSD of the lower lip and chin after BSSO related to advancement, setback, intraoperative nerve encounter and surgical skill. However, recovery of sensation occurs with increasing frequency during the follow-up period. The clinical neurosensory tests are effective guides to study the neurosensory deficit.

Low-level laser effect in patients with neurosensory impairment of mandibular nerve after sagittal split ramus osteotomy. Randomized clinical trial, controlled by placebo

Objectives: Evaluate the effect on the application of low level laser therapy, in patients that have been previously intervened with a sagittal ramus split osteotomy and present neurosensory impairment due to this surgery, compared with placebo. Study Design: This preliminary study is a randomized clinical trial, with an experimental group (n=17) which received laser light and a control group (n=14), placebo. All participants received laser applications, divided after surgery in days 1, 2, 3, 5, 10, 14, 21 and 28. Neurosensory impairment was evaluated clinically with 5 tests; visual analog scale (VAS) for pain and sensitivity, directional and 2 point discrimination, thermal discrimination, each one of them performed before and after surgery on day 1, and 1, 2 and 6 months. Participants and results evaluator were blinded to intervention. Variables were described with absolute frequencies, percentages and medians. Ordinal and dichotomous variables were compared with Mann Whitney’s and Fisher’s test respectively. Results: Results demonstrate clinical improvement in time, as well as in magnitude of neurosensory return for laser group; VAS for sensitivity reached 5 (normal), 10 participants recovered initial values for 2 point discrimination (62,5%) and 87,5% recovered directional discrimination at 6 months after surgery. General VAS for sensitivity showed 68,75% for laser group, compared with placebo 21,43% (p-value = (0.0095). Left side sensitivity (VAS) showed 3.25 and 4 medians for placebo and laser at 2 months, respectively (p-value = (0.004). Conclusions: Low-level laser therapy was beneficial for this group of patients on recovery of neurosensory impairment of mandibular nerve, compared to a placebo.

Key words:Laser Therapy, low-level, LLLP, osteotomy, sagittal split ramus, paresthesia, mandibular nerve.

Removal of bicortical screws and other osteosynthesis material that caused symptoms after bilateral sagittal split osteotomy: a retrospective study of 251 patients, and review of published papers

Rigid fixation with either bicortical screws or miniplates is the current standard way to stabilise the mandibular segments after bilateral sagittal split osteotomy (BSSO). Both techniques are widely used and the superiority of one or other method is still debatable. One complication of rigid fixation is the need to remove the osteosynthesis material because of associated complaints. The main aim of this retrospective study was to analyse how often we needed to remove bicortical screws because they caused symptoms after BSSO in our clinic. Review of other published papers also enabled us to investigate the reported rates of removal of screws and miniplates at other centres. The mean (SD) duration of follow-up of 251 patients (502 sites) was 432 (172) days, and the number of bicortical screws removed in our clinic was 14/486 sites (3%). Other methods of fixation were used at 16 sites. We found no significant association between removal of bicortical screws and age, sex, presence of third molars, or bad splits. Published rates of removal of bicortical screws and miniplates are 3.1%-7.2% and 6.6%-22.2% per site, respectively. These findings show that fixation with bicortical screws after BSSO is associated with a low rate of removal of osteosynthesis material. Reported incidences imply a lower rate of removal for screws than for miniplates.

The use of sensory action potential to evaluate inferior alveolar nerve damage after orthognathic surgery

To assess and monitor the common event of neurosensory disturbance to the inferior alveolar nerve (IAN) after bilateral sagittal split osteotomy, we used clinical sensory tests and neurophysiologic test sensory action potentials. The diagnostic value of these tests was evaluated by comparing them with the degree of nerve damage reported by patients. Fourteen patients undergoing bilateral sagittal split osteotomy were analyzed preoperatively and 2 years postoperatively. Patients were evaluated bilaterally for positive and negative symptoms: light touch sensation, paraesthesia, hyperesthesia, and dysaesthesia; a "sensation score" was then calculated for each patient. Patients were also asked if they would be willing to repeat the procedure knowing the sensation loss they had now. Next, the right and left IAN were evaluated using sensory action potential and correlated with the other results. Before surgery, the medium latency difference between left and right was lower compared with postsurgery, with all patients having some deficit. The reduction in medium amplitude of 67% after the intervention was statistically significant. The frequency of abnormal findings in the electrophysiologic tests indicating IAN injury correlated with subjective sensory alteration. All patients said that they would repeat the surgery. Electrophysiologic testing is recommended for the evaluation of nerve dysfunction and seems a sensitive method for accurately assessing postsurgical nerve conduction.

Is the lingual fracture line influenced by the mandibular canal or the mylohyoid groove during a bilateral sagittal split osteotomy? A human cadaveric study

PURPOSE

Although the bilateral sagittal split osteotomy (BSSO) is a routinely performed procedure, exact control of the lingual fracture line remains problematic. The purpose of this study was to determine the various lingual splitting patterns in cadaveric human mandibles after a BSSO and the possible influence of the mandibular canal and mylohyoid groove on the lingual fracture line.

MATERIALS AND METHODS

The investigators designed and implemented a case series to compare different lingual fracture lines. A standardized SSO was performed on 40 cadaveric hemimandibles using elevators and splitting forceps. The primary outcome variable during this study was the lingual fracture pattern possibly influenced by independent variables: the mandibular canal, the mylohyoid groove, and dental status. Descriptive and analytic statistics were computed for each study variable.

RESULTS

Most lingual fractures (72.5%) ended in the mandibular foramen. Only 25% of fractures were "true" Hunsuck fractures, and no "bad splits" occurred. In addition, 35% of lingual fractures ran more than halfway or entirely through the mandibular canal, whereas only 30% of fractures ran along the mylohyoid groove. However, when the lingual fracture ran along this groove, it had a 6-fold greater chance of ending in the mandibular foramen.

CONCLUSIONS

The hypothesis that the mandibular canal or mylohyoid groove would function as the path of least resistance was only partly confirmed. The use of splitters and separators did not increase the incidence of bad splits compared with the literature.

Bilateral sagittal split osteotomy in a mandible previously reconstructed with a non-vascularized bone graft

We report a bilateral sagittal split osteotomy (BSSO) in a reconstructed mandible. A 28-year-old woman underwent a segmental mandibulectomy due to a multicystic ameloblastoma in the left jaw. After primary plate reconstruction, final reconstruction was performed with a left posterior iliac crest cortico-cancellous autograft. Due to a pre-existing Class II malocclusion, the patient was analyzed for combined orthodontic-surgical treatment. Subsequently, after 1 year of orthodontic treatment, the BSSO was planned. The sagittal split was performed in the remaining right mandible and on the left side in the iliac crest cortico-cancellous autograft. Ten months later, oral rehabilitation was completed with implant placement in the neomandible. Follow-up showed a Class I occlusion, with good function. The patient was very satisfied with the functional and aesthetic results. This case shows that a BSSO can be performed in a reconstructed mandible, without side effects and with good functional and aesthetic results.

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.

Risk factors for neurosensory disturbance after bilateral sagittal split osteotomy based on position of mandibular canal and morphology of mandibular angle

PURPOSE

The aim of the present study was to evaluate the potential morphologic risk factors for postoperative neurosensory disturbance (NSD) after bilateral sagittal split osteotomy.

PATIENTS AND METHODS

The study subjects were 30 skeletal Class III patients (9 males and 21 females), with a mean age of 22.0 years (range, 16-39 years). All patients underwent bilateral sagittal split osteotomy for setback to correct mandibular prognathism. The bone marrow space between the outer mandibular canal and the lateral cortex of the ramus was measured on transaxial computed tomography images, and the length at the mandibular angle between the retromolar and gonion was measured on the lateral cephalograms. The NSD was tested bilaterally using discrimination to touch with the sharp head of a mechanical probe. Each patient was evaluated at 1, 3, and 6 months postoperatively.

RESULTS

The median bone marrow space was 1.96 mm (range, 0-4.5 mm), and median length of the mandibular angle was 30.93 mm (range, 23-37 mm). Neurosensory disturbance was present on 15 sides (25.0%) at 1 month postoperatively, 9 sides (15.0%) at 3 months postoperatively, and 7 sides (11.7%) at 6 months postoperatively. The difference in the incidence of NSD with a small bone marrow space and a long mandibular angle from that with a large bone marrow space and short mandibular angle was highly statistically significant (P = .006 and P < .01, respectively).

CONCLUSIONS

The frequency of NSD after bilateral sagittal split osteotomy in Class III cases was dependent not only on the position of mandibular canal, but also on the length of the mandibular angle. A lateral course of the mandibular canal and a long mandibular angle appeared to result in a high risk of injury to the inferior alveolar nerve, resulting in NSD owing to a compromised splitting procedure.