Introduction
This study aimed to investigate the incidence and recovery of neurosensory deficit (NSD) after LeFort I osteotomy over 12 months and identify any association between age, gender, and extent of surgical movement on recovery. Furthermore, the study explored the relationship between objective and subjective outcome measures.
Methods
A prospective cohort study consisting of 31 patients. Subjects were assessed at baseline, 1 week (T1), 1 month, 3 months, 6 months, and 12 months (T5) after LeFort I osteotomy. Objective assessment measures included pinprick (PP), static light touch (SLT), static 2-point discrimination (STPD), and electric pulp testing (EPT). Subjective reporting was undertaken using a visual analog scale. Patients rated the impact of NSD on intraoral and extraoral sites at the same time points as for objective measures.
Results
Twenty-eight patients (16 females and 12 males) with a mean age of 24.5 years (standard deviation, 7.4) completed the study. There was a notable reduction in NSD from T1 (85.7%) to T5 (17.9%). No significant differences were found with respect to the influence of gender; PP ( P = 0.06), SLT ( P = 0.10), STPD ( P = 0.65) and EPT ( P = 0.19) or extent of surgical movement; PP ( P = 0.50), SLT ( P = 0.72), STPD ( P = 0.06) and EPT ( P = 0.74) on NSD. Age is a significant factor for intraoral NSD in the immediate postoperative period; PP ( P < 0.0001) and SLT ( P < 0.0001). Subjectively, patients reported a high degree of concern associated with NSD immediately after surgery with a gradual reduction from T1 to T5. There is a significant difference in subjective reporting between those with intraoral NSD than those with no intraoral NSD at 12 months ( P = 0.031).
Conclusions
NSD is high after LeFort I surgery, particularly intraorally in the palate. At 12 months, the incidence of NSD is 17.9%. Recovery of NSD to a nonsignificant value from baseline takes up to 3 months for extraoral sites and between 3 and 6 months for intraoral soft tissues. The maxillary dentition continues to recover from NSD up to 12 months postsurgery. Age, gender, and extent of the surgical movement do not influence the extent of NSD at 12 months. Increasing age is associated with increased NSD at intraoral sites immediately after surgery. Intraoral NSD is more of a concern to patients than extraoral NSD. Patients’ concerns associated with NSD reduced over time, demonstrating a degree of adaptation in the longer term.
Highlights
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A prospective cohort study assessed neurosensory recovery after LeFort I osteotomy.
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Patients were followed postoperatively for 12 months with subjective and objective assessments.
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The impact of age, gender, and extent of surgical movement were evaluated.
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At 12 months, the incidence of neurosensory deficit is 17.9%.
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Patients’ concern associated with neurosensory deficit reduced over time.
Neurosensory deficit (NSD) is a commonly reported complication after a LeFort I osteotomy (LF1O), with a highly variable incidence reported in the literature ranging from 9% to 85%. The long-term outcomes have not been comprehensively reported, especially relating to objective and subjective outcomes. , It is essential we have sufficient information on material risks to offer our patients as part of the informed consent process.
Previous studies have added to the evidence base in this field but suffer from shortcomings related to brief follow-up periods, , , limited sample size, absent anatomic sites, , , lack of baseline assessment, variabilities in assessment protocols, and only including either objective or subjective outcomes. , , In addition, no consensus exists on somatosensory protocol capturing infraorbital changes. Furthermore, most research in orofacial NSD reports on inferior alveolar nerve recovery.
New approaches in orthognathic surgery, including the use of piezoelectric instrumentation, have been reported to improve outcomes for NSD. Fundamentally, the piezoelectric saws using low-frequency vibrations to aid cutting of bone with more precision and safety. Originally introduced to help reduce the shortcomings of traditional bone instrumentation with maxillary sinus surgery its use has widened to include orthognathic surgery. Among its major advantages, piezoelectric surgery has been shown to reduce soft-tissue trauma. This, in turn, has a positive impact on the reduction of blood loss with a better field of view during surgery, improved osteotomy segmentation, reduced postoperative swelling and a reduction in NSD incidence. , ,
However, most of the studies carried out with piezoelectric surgery have been on mandibular surgical procedures, and they have shown positive improvements in the reduction of inferior dental nerve injuries. , Although there are few clinical trials with sufficiently high-quality evidence to systematically review; a recent meta-analysis has shown a pooled difference of severe NSD in favor of using piezoelectric over conventional instrumentation.
Another interesting aspect of NSD is the subjective analysis of patient perceptions. Objective assessment is an effective method of identifying the extent of NSD. However, research has identified that the context of such results should be assessed alongside subjective reporting by the patient. In medical literature, subjective and objective assessments have been shown to correlate with each other in the assessment of trigeminal nerve repair. Accordingly, subjective outcomes are more conclusive when analyzed in conjunction with objective outcomes. , However, the link between objective and subjective reporting is complicated with the literature reporting differences among which objective testing methods correlate best with subjective reporting. This study intends to bridge the gap by undertaking a comprehensive subjective and objective assessment of NSD, including both intraoral and extraoral sites with a prolonged follow-up period.
The primary objectives of the study were to assess the incidence and pattern of recovery of NSD after LF1O. Secondary objectives were to investigate the relationship between age, gender, and extent of surgical movement on NSD and explore the relationship between subjective and objective outcome measures of NSD.
Material and methods
This study was a prospective longitudinal cohort study. Ethical approval was obtained from the National Research Ethics Service, Queens Square London (14/LO/1605) and the Joint Research Management Office for Barts and the London School of Medicine and Dentistry.
Participants were recruited at the Institute of Dentistry, Barts and The London School of Medicine and Dentistry, London, United Kingdom from July 2014 to October 2016. Data collection was undertaken by 2 postgraduate orthodontic trainees (A.R.D and N.B).
The inclusion criteria were as follows: (1) patients undergoing an LF1O as part of their treatment at Barts Health NHS Trust, United Kingdom; and (2) adult male and female patients (aged 18 years or older).
The exclusion criteria were as follows: (1) patients who present with preexisting medical conditions affecting neurosensory function or NSD; (2) patients who have had previous orthognathic treatment, treatment for facial deformity, or any other form of facial surgery; (3) administration of medications that affect neurosensory perception and recovery; and (4) patients from vulnerable groups (given the nature of the intervention and concerns over the ability to understand, consent and/or partake in the research study).
All patients meeting the criteria were invited to participate. An expected sample size of 30 patients was identified from previous studies. A convenient consecutive sample of 31 patients was recruited.
Subjects were consented to participate in the study. Two experienced oral and maxillo-facial surgeons carried out the surgical interventions involving the use of a reciprocating saw and miniplate fixation. A standardized surgical protocol, in keeping with the department’s normal procedure, was adopted for the surgical phase, including the preoperative workup and postoperative surgical care. No surgical complications necessitating repeat surgery were encountered.
Patients were assessed in a supine position with eyes closed, limiting the use of nonspatial information to minimize bias. Objective and subjective assessment was carried out at the following time points: baseline readings before surgery (T0) and at 1-week (T1), 1-month (T2), 3-months (T3), 6-months (T4), and 12-months (T5) postsurgery. The assessment methods were standardized to limit intraoperator and interoperator variability.
Extraoral sites assessed included the skin overlying the infraorbital region under the lower eyelid (marked red ), over the alar cartilage (marked blue ), above the upper lip vermillion border (marked black ), and overlying the cheeks (marked yellow ) ( Fig 1 ). Intraoral sites assessed included the vestibular and palatal mucosa adjacent to the first permanent molar, the first premolar, and the central incisor ( Fig 2 ). Teeth sensibility testing was conducted in the maxillary dentition from the first permanent molar to the permanent central incisor ( Fig 2 ). All missing, root treated, or prosthetically restored teeth were omitted without substitution.
Objective assessments included pinprick (PP), static light touch (SLT), static 2-point discrimination (STPD), and electric pulp testing (EPT) ( Fig 3 ). Nociception was assessed with PP using a dental probe placed perpendicular to the surface until blanching was detected , ( Fig 3 ). A verbal response was recorded from the patient to a positive or negative sensation. SLT was assessed using a calibrated filament (NeuroPen; Owen Mumford, Woodstock, United Kingdom) placed perpendicular to the site of interest. The filament bowed once to provide an accurate, 10 g of reliable force and was left for 1-2 seconds ; the patient responded verbally whether a positive or negative stimulation was felt. The use of both PP and SLT allowed for the assessment of both sharp painful stimuli and blunt stimuli.
Assessment of peripheral nerve density was undertaken using STPD, a caliper with a set distance determined at T0 for specific patients ( Fig 3 ). Once set, the caliper was placed on the test sites, with both points touching equally and perpendicular to the skin surface. Enough pressure was applied until the surface skin blanched. If the patient did not believe the 2 points separately, at the minimum distance, this was recorded as a negative reading.
Pulp sensibility testing in the maxillary dentition was conducted using an EPT machine because of its documented reliability. , The tip was placed on the surface with the closest proximity to the pulp chamber using a conducting medium ( Fig 3 ). Patients responded verbally at the onset of warming or tingling sensation. A negative response was tested twice to ensure true negatives. To limit crosstalk, no conducting medium nor the EPT tip touched any of the metallic brackets.
Visual analog scales (VAS) were used for subjective assessment. Patients rated how much the numbness “bothered” them from not at all (0 mm) to extremely (100 mm); extraoral and intraoral scores were recorded separately. Patients were not given access to their previous scores at the assessments.
The primary outcome measures were the incidence and the recovery of NSD after LF1O over the study duration from baseline to 12 months. Secondary outcomes included the relationship between age, gender, the extent of surgical movement on the incidence of NSD, and the relationship between subjective and objective outcome measures of NSD.
Statistical analysis
Data were analyzed with a combination of descriptive and analytical statistics using JMP Pro statistical software (version 14; SAS, Cary, NC). Data for PP, SLT, STPD, and vitality was structured such that the unit of analysis was a measurement nested within a person repeated over time. Therefore, a mixed-effects repeated-measures analysis of covariance (ANCOVA) was chosen. Using the random coefficients, this approach allowed for multiple error structures to represent the nested nature of the data without violating the independence assumption. Implementing the restricted maximum likelihood approach better balances the weight of the observations with respect to variance across the hierarchical structure. For detailed comparisons between categories, the Šidák correction for multiple post-hoc t tests was used. Subjective outcomes were calculated as a percentage mean measurement from the VAS using Wilcoxon tests. Cohen’s kappa statistics were used to assess the reliability of the 2 assessors. For the categorical outcome, maxillary dentition NSD, a multiple mixed logistic regression was used. The level of significance was set at P < 0.05.
Results
Of the 31 patients recruited, 3 were lost during follow-up. One patient moved abroad, and the other 2 patients chose not to continue citing complexity in organizing suitable appointments. Therefore, data for 28 patients that completed the study are presented.
The total sample consisted of 28 participants with a mean age of 24.5 years (standard deviation [SD], 7.4) comprised 12 males (mean [M], 23.3; SD, 5.1) and 16 females (M, 25.4; SD, 8.8). Seventeen patients (60.7%) underwent a maxillary advancement only, 4 patients (14.3%) had a maxillary impaction only, and 7 patients (25.0%) underwent a combination of the movements mentioned above.
The mean minimum distance perceptible by patients at T0 for the STPD assessment was 11.4 mm (SD, 2.5). No patient reported any preexisting NSD at T0. All teeth included in the analysis responded positively to sensibility testing at T0.
Tables I and II illustrate the number of patients with NSD at any given time point and the results of objective testing by the site over 12 months. At T1, the highest incidence of NSD was reported in 24 patients (85.7%). At T4, the incidence was at its lowest level, with 5 patients (17.9%) assessed as positive for NSD. At T5, the overall incidence is the same as at T4, with 5 patients (17.9%) presenting with NSD. Subjects exhibited 100% recovery with the PP test, whereas the SLT and STPD elicited NSD in 1 (3.6%) and 4 (14.3%) subjects, respectively ( Table I ). The pattern of recovery of NSD is illustrated in Figure 4 . There is a reduction in NSD from 85.7% at T1 to 17.9% at T5, with the majority of recovery in terms of overall incidence of NSD occurring between 1 (T2) and 6 (T4) months after surgery.
| Category | NSD SLT | NSD PP | NSD STPD | NSD overall |
|---|---|---|---|---|
| T0 | 0 (0) | 0 (0) | 0 (0) | 0 (0) |
| T1 | 21 (75) | 20 (71.4) | 9 (32.1) | 24 (85.7) |
| T2 | 16 (57.1) | 13 (46.4) | 9 (32.1) | 20 (71.4) |
| T3 | 8 (28.6) | 3 (10.7) | 4 (14.3) | 12 (42.9) |
| T4 | 3 (10.7) | 0 (0) | 3 (10.7) | 5 (17.9) |
| T5 | 1 (3.6) | 0 (0) | 4 (14.3) | 5 (17.9) |
| Site | T0 | T1 | T2 | T3 | T4 | T5 | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| M | SD | M | SD | M | SD | M | SD | M | SD | M | SD | |
| PP | ||||||||||||
| Alar | 3.00 | 0.00 | 2.96 | 0.27 | 2.98 | 0.13 | 3.00 | 0.00 | 3.00 | 0.00 | 3.00 | 0.00 |
| Cheek | 3.00 | 0.00 | 2.88 | 0.54 | 2.95 | 0.30 | 3.00 | 0.00 | 3.00 | 0.00 | 3.00 | 0.00 |
| Upper lip | 3.00 | 0.00 | 2.88 | 0.51 | 2.91 | 0.48 | 3.00 | 0.00 | 2.98 | 0.13 | 3.00 | 0.00 |
| Infraorbital | 3.00 | 0.00 | 2.84 | 0.63 | 2.93 | 0.26 | 3.00 | 0.00 | 3.00 | 0.00 | 3.00 | 0.00 |
| Vestibular | 3.00 | 0.00 | 2.30 | 1.06 | 2.80 | 0.59 | 2.93 | 0.32 | 3.00 | 0.00 | 2.98 | 0.13 |
| Palatal | 3.00 | 0.00 | 1.46 | 1.33 | 2.39 | 1.00 | 2.80 | 0.64 | 2.98 | 0.13 | 3.00 | 0.00 |
| SLT | ||||||||||||
| Alar | 3.00 | 0.00 | 2.98 | 0.13 | 2.98 | 0.13 | 3.00 | 0.00 | 3.00 | 0.00 | 3.00 | 0.00 |
| Cheek | 3.00 | 0.00 | 2.88 | 0.51 | 2.96 | 0.27 | 3.00 | 0.00 | 3.00 | 0.00 | 3.00 | 0.00 |
| Upper lip | 3.00 | 0.00 | 2.86 | 0.62 | 2.93 | 0.42 | 3.00 | 0.00 | 2.98 | 0.13 | 3.00 | 0.00 |
| Infraorbital | 3.00 | 0.00 | 2.95 | 0.30 | 2.98 | 0.13 | 3.00 | 0.00 | 3.00 | 0.00 | 3.00 | 0.00 |
| Vestibular | 3.00 | 0.00 | 2.27 | 1.02 | 2.82 | 0.54 | 2.88 | 0.38 | 2.91 | 0.44 | 2.91 | 0.44 |
| Palatal | 3.00 | 0.00 | 1.34 | 1.34 | 2.25 | 1.01 | 2.64 | 0.84 | 2.80 | 0.72 | 2.93 | 0.37 |
| STPD | ||||||||||||
| Alar | 3.00 | 0.00 | 2.88 | 0.51 | 2.96 | 0.27 | 2.98 | 0.13 | 2.96 | 0.27 | 2.96 | 0.27 |
| Upper lip | 3.00 | 0.00 | 2.80 | 0.64 | 2.91 | 0.39 | 3.00 | 0.00 | 2.98 | 0.13 | 2.98 | 0.13 |
| Cheek | 3.00 | 0.00 | 2.61 | 0.89 | 2.80 | 0.64 | 2.84 | 0.53 | 2.91 | 0.35 | 2.93 | 0.26 |
| Infraorbital | 3.00 | 0.00 | 2.57 | 0.85 | 2.63 | 0.84 | 2.77 | 0.71 | 2.96 | 0.19 | 2.80 | 0.59 |
| EPT | ||||||||||||
| Maxillary, % | 99.40 | 0.08 | 48.20 | 0.50 | 54.00 | 0.50 | 71.90 | 0.45 | 85.00 | 0.36 | 97.10 | 0.17 |
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