Is It Necessary to Free the Inferior Alveolar Nerve From the Proximal Segment in the Sagittal Split Osteotomy?

Surgical outcomes of the surgical techniques following management of iatrogenic trigeminal nerve injuries: A systematic review

Objective

To investigate the effectiveness of the microsurgical treatment in restoring full sensory recovery following trigeminal nerve injuries caused by iatrogenic oral and maxillofacial surgical interventions.

Methods

A detailed search was conducted on the Cochrane central register of controlled trials, Medline and Embase. Clinical studies with at least twelve months of follow up were included and assessment of risks of bias was made using the Robbin I assessment tool.

Results

Six studies were identified in the searches which include 227 patients. The lingual nerve was the most common injured nerve, followed by the inferior alveolar nerve. Third molar removal was the most frequent cause of nerve injury, followed by root canal treatment, pathology excision, coronectomy, orthognathic surgery, dental implants and then local anaesthetic injections. Overall, surgical interventions for nerve injuries showed neurosensory improvement postoperatively in the majority of patients.

Conclusion

Direct neurorrhaphy is still the gold-standard technique when the tension at the surgical site is minimal. Promising results have been noted on conduit applications following traditional repair or grafting. Further research is needed on the efficacy of allografting and conduit applications in nerve repair.

Relationship of the Degree of Nerve Exposure and Surgical Manipulation and Short-Term Neurosensory Disturbance Following Sagittal Split Ramus Osteotomy: A Prospective Study

BACKGROUND

Neurosensory disturbance (NSD) is a common complication after sagittal split ramus osteotomy (SSRO) due to inferior alveolar nerve (IAN) injury. The impact of intraoperative nerve manipulation on NSD remains debated.

PURPOSE

The purpose of this study was to evaluate the influence of IAN exposure and manipulation during SSRO on functional sensory recovery (FSR).

STUDY DESIGN

This was a single-center, prospective cohort study of 40 patients undergoing SSRO at Mahidol University from December 2020 to December 2021. The inclusion criteria were patients aged 20-34, ASA Class I-II. The exclusion criteria were patients with systemic bone disease, history of head and neck or neurological pathology, previous SSRO, or incomplete data collection.

PREDICTOR VARIABLE

Degree of intraoperative nerve manipulation was divided by the attending surgeon as follows; 1) Nerve fully encased in distal segment and not visible (NS); 2) Nerve encased in distal segment but partially visible (DS); and 3) Nerve partially encased in proximal segment and fully dissected free (PS).

OUTCOME VARIABLES

The area of interest was divided into the lip and chin. The primary outcome was time to FSR. The secondary outcome was subjective patient report, using a visual analogue scale, compared to FSR.

COVARIATES

The covariates were sex, age, skeletal diagnosis, degree of movement, and concomitant genioplasty/subapical procedure.

ANALYSES

Kaplan-Meier survival analysis, Cox proportional hazards regression, and Mcnemar test were utilized. P-value < .05 was significant.

RESULTS

In the lip, the median times to FSR were NS, 2 days; DS, 45 days; PS, 102 days. (Interquartile range: 77,127, 114, respectively) In the chin, the median times to FSR were NS, 23 days; DS, 92 days; PS, 87 days. (Interquartile range: 77, 161, 101, respectively.) Nerve manipulation significantly affected FSR in the lip and chin (P = .001, <0.001, respectively. Cox hazard ratios for DS and PS were lower compared to NS. Patients consistently reported more NSD compared to FSR as per Mcnemar test.

CONCLUSION AND RELEVANCE

After SSRO, FSR in the lip is prolonged when the IAN is partially encased in the proximal segment and released. This raises the question of the efficacy of surgically releasing a partially encased IAN.

The effect of mandibular advancement for mandibular deficiency dentofacial deformities on laryngeal grade and intubation difficulty: a preliminary study

OBJECTIVE

The purpose of this study was to evaluate mandibular advancement for cases of mandibular deficiency with changes in vocal cord grade and intubation difficulty at subsequent surgery requiring intubation.

STUDY DESIGN

This retrospective case series included patients with a diagnosis of mandibular deficiency (Class II skeletal dentofacial deformity) who underwent mandibular advancement surgery (T1) followed by a subsequent surgery (T2) which required intubation. The primary predictor variable was mandibular advancement. The primary outcome variable was the change in laryngeal grade-Cormack and Lehane-after mandibular advancement. A secondary outcome was intubation difficulty after mandibular advancement.

RESULTS

Eight patients were included in the study. At T1, the average laryngeal grade was 1.6. There was 1 difficult intubation. The average time to T2 was 9 months. At T2, all patients were intubated on their first attempt, and all had a Cormack-Lehane Grade I view of the vocal cords. There were no difficult intubations at T2. Analysis showed a significant association between mandibular advancement and laryngeal grade at T2 (P = .03; 95% CI 0.07-1.13).

CONCLUSIONS

This preliminary investigation found an association between mandibular advancement for cases of mandibular and improved laryngeal grade at subsequent intubation without any difficult intubations.

Gender-Affirming Surgery of the Mandible: Lower Jaw Feminization and Masculinization

For patients with gender dysphoria, gender-affirming surgery of the face has been shown to vastly improve quality of life. The mandible is one area of the face that has distinct feminine and masculine presentations. This article will review gender-affirming surgery of the lower jaw, both for feminization and masculinization. Techniques for bony contouring and soft tissue manipulation will be discussed.

Infralingular Versus Supralingular Medial Osteotomy in Sagittal Split Osteotomy of the Mandible: A Randomized Control Study

PURPOSE

A recently proposed modification of the sagittal split osteotomy (SSO) of the mandible places the horizontal medial cut 'low and short' of the lingula. The purpose of the study was to answer the following clinical question: Among patients undergoing mandibular setback procedures (≤ 8 mm) via SSO, does the placement of the medial horizontal osteotomy below the lingula (infralingular), when compared to placement above the lingula (supralingular), results in different neurosensory, bite force, and range of motion outcomes?

MATERIALS AND METHODS

This was a single-center, double-blind, parallel-group study among patients undergoing mandibular setback by SSO (≤ 8 mm), between January 2021 and September 2022. Patients were randomly allocated in a ratio of 1:1 to the supralingular (control) and the infralingular (study) group. Primary outcome variables included neurosensory disturbance of the inferior alveolar nerve based on clinical neurosensory testing and severity graded using Zuniga and Essick's protocol, bite force, and maximum mouth opening evaluated postoperatively during the first week (T1), first month (T2), and third month (T3) of follow-up. Secondary outcome measures included the incidence of a bad split and distal segment interferences intraoperatively. Association between the variables was assessed using Pearson chi-squared test or Fisher's exact test based on the expected observations. A P value of ≤.05 was considered statistically significant.

RESULTS

A total of 29 patients (58 osteotomies) were included in the study. Group 1 consisted of 15 patients (9 females and 6 males) with a mean age of 26.4 years. Group 2 consisted of 14 patients (8 females and 6 males) with a mean age of 25.9 years. Patients with severe neurosensory disturbance of the inferior alveolar nerve were more common in group 2 (n = 15, 53.6%) than group 1 (n = 4, 13.3%) at T1 (P value = .0001) and insignificant between the two groups at T2 (P value = .63) and T3 (P value = .99). Comparison of maximum mouth opening between the two groups at T1 (P value = .535), T2 (P value = .934), and T3 (P value = .703) and bite force at T1 (P = .324), T2 (P = .113), and T3 (P = .811) was not significant.

CONCLUSION

Both SSO techniques have similar clinical outcomes among patients having mandibular setbacks (≤ 8 mm) for the variables studied.

Are There Differences in Fracture Patterns in Mandibular Ramus Sagittal Osteotomies Between Hunsuck/Epker, Wolford, and Posnick Modifications?

PURPOSE

Despite decades of study, the best technique for mandibular ramus sagittal osteotomy has not been definitively determined. The purpose of the present study was to compare fracture patterns, inferior alveolar nerve (IAN) visualization, and torque required for mandibular sagittal splitting using the Hunsuck/Epker, Wolford, and Posnick techniques.

METHODS

This was a laboratory (ex vivo), randomized, a single-blind study performed to evaluate sagittal split osteotomies in porcine mandibles using a specifically designed test system. The study's predictor variable was the osteotomy technique, which was divided into 3 groups: Group Hunsuck/Epker (GHE), group Wolford (GW), and group Posnick (GP). The outcome variables were lingual fracture pattern, torque in newtons (N) required to separate the mandible, and IAN visualization. The covariates were mandibular radiodensity and time between dejection and the experiment. The Kolmogorov-Smirnov normality statistics and analysis of variance with Tukey post test statistics were performed. P value <.05 was considered statistically significant.

RESULTS

The sample was composed of 120 equally divided porcine hemimandibles in each group. The torque forces were significantly lower (P < .001) when using the Posnick technique (2.07 ± 0.22 N) than when using the Hunsuck/Epker technique (4.45 ± 0.32 N) and Wolford (3.00 ± 0.21 N). GW (93.3%) and GHE (56.7%) showed a higher prevalence of lingual fracture in the posterior region of the mandibular canal (P < .001), while the GP (90%) had a higher frequency of lingual fracture pattern on the mylohyoid sulcus (P < .001). In more than 90% (P < .001) of the mandibles in GW and GHE, the IAN visualization was higher than 50%. In the GP, 90% (P < .001) of patients had IAN visualization of less than 50%.

CONCLUSIONS

The Posnick technique required less torque to perform the sagittal osteotomy in a pig mandible and had good predictability (90%) for the less preferred lingual fracture pattern and minimal visualization of the nerve. The Wolford technique provided the best predictability (93%) for the preferred lingual fracture pattern and the best nerve visualization. Caution must be exercised when extrapolating the results from animal models to human applications.

Influence of Inferior Alveolar Nerve Exposure During Sagittal Split Osteotomy on the Rate and Timing of Baseline Sensory Recovery

PURPOSE

Neurosensory disturbance is the most common consequence of sagittal split osteotomy (SSO). The purpose of this study is to quantitatively assess neurosensory deficiency and recovery to the preoperative status when the inferior alveolar nerve (IAN) was exposed versus unexposed during SSO.

METHODS

This is a single-center, prospective, cohort study of all patients undergoing bilateral SSO between August 2018 and July 2019. Patients were included in the study sample if they underwent bilateral SSO with an intact intraoperative IAN and were received follow-up assessment for at least a year. The predictor variable was the intraoperative IAN status (exposed vs unexposed). The outcomes of interest were the rate and timing of recovery to the preoperative status. The covariates were age, sex, and the magnitude and direction of surgical movements. Neurosensory function was quantitatively evaluated using the Semmes-Weinstein monofilament test at follow-up intervals of 1, 3, 6, and 12 months. Descriptive statistics, bivariate statistics, Cox proportional hazards regression, and Kaplan-Meier analyses were performed. P value <.05 was considered statistically significant.

RESULTS

Of 90 patients, 86 patients who underwent 172 SSOs were included in this study. The mean age was 22.95 ± 3.34 years (range, 17 to 30), 65 were women, and the range of surgical movements was 3 to 8.3 mm of advancement and 2 to 12 mm of setback. Eighty-five nerves (49.4%) were allocated to the unexposed group, and 87 (50.6%) to the exposed group, with statistically significant differences in the rate and timing of recovery (hazard ratio = 2.368; 95% confidence interval, 1.662 to 3.376; P < .001). Among those with recovered nerves, the median time to recovery was 90 days in the unexposed group and 364 days in the exposed group (P < .0001).

CONCLUSIONS

IAN exposure during SSO is associated with an increased risk of neurosensory deficiency and an increased time of sensory recovery to the baseline threshold in patients aged 17 to 30 years. When the IAN remained fully enclosed in the canal of the distal segment, only 11% of patients had a measurable sensory deficit 1 year after surgery. In those patients with any degree of IAN exposure, 36% had a residual sensory deficit 1 year after surgery.

Systematic mapping review of orthognathic surgery

STUDY DESIGN

Systematic mapping review AIM AND SCOPE: The objective of this mapping review was to identify, describe, and organize clinical research currently available from systematic reviews and primary studies regarding co-interventions and different surgical modalities used in orthognathic surgery (OS) and their outcomes.

METHODS

Systematic reviews (SRs), randomized controlled trials, and observational studies that evaluated perioperative OS co-interventions and surgical modalities were identified in an exhaustive search of MEDLINE, EMBASE, Epistemonikos, Lilacs, Web of Science, and CENTRAL. Grey literature was also screened.

RESULTS

Included were 35 SRs and 253 primary studies, 103 from SRs, and another 150 identified in our search. Overall, SR quality was rated as critically low, with only two SRs rated as of high quality. 19 questions on population, interventions, comparisons, and outcomes (PICO) extracted from the SRs focused on osteosynthesis methods, surgical cutting devices, and use of antibiotics, corticosteroids, and induced hypotension. Also identified were 15 research gaps. Evidence bubble maps were created to graphically depict the available evidence.

CONCLUSION

Future high-quality research, both primary and secondary, is needed to address the knowledge gaps identified in this systematic mapping review.

Does the use of a piezoelectric saw improve neurosensory recovery following sagittal split osteotomy?

Neurosensory disturbance of the inferior alveolar nerve (IAN) is an adverse effect associated with sagittal split osteotomies (SSO). The purpose of this work was to evaluate neurosensory recovery of the IAN when SSOs were performed with piezoelectric (PZ) versus reciprocating (RP) saws. This was a prospective split-mouth study of patients undergoing bilateral SSO using a PZ saw on one side and an RP saw on the other. The primary outcome of interest was neurosensory recovery, as assessed using the functional sensory recovery (FSR) scale defined by the UK Medical Research Council. Descriptive, bivariate, and regression statistics were computed. Twenty patients (40 SSOs) with a mean age of 19.9 ± 3.2 years were included. The mean mandibular movement did not differ significantly (P = 0.50) between the PZ and RP groups. All patients achieved FSR within 1 year of surgery (range 34-249 days). The median time to FSR overall was comparable between the PZ and RP groups (94.5 days and 101.5 days, respectively; P = 0.20). However, at the time FSR was achieved, PZ SSO sites were more likely to have higher neurosensory scores when compared to RP SSO sites (hazard ratio 2.3, 95% confidence interval 1.1-4.9, P = 0.04).

Use of a 'low and short' medial cut limits sagittal ramus osteotomy interferences

The traditional 'high and short' medial cut of the sagittal ramus osteotomy (Hunsuck modification) is a frequent cause of lingual plate interferences in patients undergoing mandibular yaw or cant corrections. We describe how the modified 'low and short' medial cut of the sagittal ramus osteotomy reduces lingual plate interferences with improved passive alignment of the osteotomy segments.

What are the Effects of Age and Presence of Third Molars on the Occurrence of Unfavorable Splits During Sagittal Split Osteotomy?

PURPOSE

Several studies have investigated risk factors of unfavorable splits associated with sagittal split osteotomies but yielded conflicting information. The purpose of this study is to estimate the frequency of and identify factors associated with unfavorable splits during sagittal split osteotomies (SSOs).

MATERIAL AND METHODS

A retrospective cohort study was conducted on patients who underwent orthognathic surgery, including SSOs at our institution from January 2010 to October 2016. The independent variables were mandibular third molar (M3) status, age, gender, and preoperative dentofacial diagnosis. The outcome variable was the effectiveness of the sagittal split resulting in either favorable or an unfavorable split. Data analyses were performed using logistic regression models except in the case of small sample sizes of preoperative dentofacial diagnoses for which the Fisher's exact test was used.

RESULTS

A total of 888 patients with an average age of 24.97 ± 5.09 years underwent 1,776 SSOs. Sixteen (0.90%) unilateral unfavorable splits occurred. Unfavorable splits were less common in patients with an M3 present than in patients with the M3 absent. Having an M3 present reduced the chance of an unfavorable split by 69%, adjusted for age and gender; OR (95% CI) = 0.308 (0.103, 0.919); P = .035. The odds of having an unfavorable split were increased by 8.8% for every year of age increase; adjusted OR (95% CI) = 1.088 (1.004, 1.178); P = .038. Based on this estimation, a 45-year-old is 2.3 times more likely to have an unfavorable split compared to a 35-year-old (95% CI:1.041, 5.146), and is 5.4 times more likely to have an unfavorable split compared to a 25-year-old (95% CI:1.083, 26.48).

CONCLUSIONS

The presence of a mandibular third molar (M3) was associated with a decreased risk of an unfavorable split, independent of age and gender. There was a significant association between increased age and the incidence of an unfavorable split.