Changes of the Upper Airway Volume After Orthognathic Surgery
Condition: OSA; Malocclusion; Dentofacial Deformities
MeSH terms: Dentofacial Deformities; Malocclusion
Study type: Observational

Summary: 
      The aim of the present project is to analyze the impact from orthognathic surgery on the
      upper airway respiratory volume.

      The primary objective is comparison of differences in the in the airway changes due to
      maxillary movements and mandibular movements.

      Secondary objectives are the analysis of any correlation between the magnitude of the
      movement and the airway volume, correlation between the direction of the movements and the
      changes in airway volume and correlation with Health-Related Quality of Life (HRQoL).
      Expected confounding factors like smoking habits and Body Mass Index (BMI) will be analyzed.
    

Detailed description: 
      Background Orthognathic surgery affects the position of the teeth and jaws. The upper airway
      compartment is in close approximation to these tissues. Consequently, changes of the
      respiratory volume after surgical treatment in this region is expected.

      Orthognathic surgery The correction of severe malocclusions and dentofacial deformities has
      since the beginning of 20th century been treated with orthodontic and surgical methods.
      Epidemiologic surveys reveal that about 5 % of the western population has dentofacial
      disproportions of a magnitude that affect both function and facial aesthetics.

      Respiratory disability Obstructive sleep apnea, estimated to occur in between 5% and 10% of
      the western countries' population. Disabilities in the upper airway may affect the patient's
      general health and quality of life. Breathing incapability often lead to impaired sleep and
      consequently decrease the individual's overall capacity and performance. Known predisposing
      factors are obesity, smoking and age.

      Treatment of respiratory disabilities Medical, behavioral and surgical treatment options are
      prospected methods and the treatment is individually planned in detail. The complex nature of
      obstructive sleep apnea may require multidisciplinary assessment.

      Orthognathic surgery as treatment for obstructive sleep apnea syndrome (OSAS) Correction of
      anatomical abnormalities may cure obstructive sleep apnea or improve compliance with positive
      airway pressure treatment. Orthognathic surgery with an anterior movement of the jaws can
      increase the airway volume and facilitate breathing.

      Measurements and evaluation of the upper airway volume Different methods of measuring the
      upper airway, like physio metric and radiological are present.

      Project plan Subjects The study is performed retrospectively on a prospective material.
      Sixty-two consecutive patients aged between 18 to 30 years with Angle class III occlusion
      were included in the study.

      Patients with systemic diseases in the musculoskeletal apparatus, drug abuse, poor psychic
      status or disease in the temporomandibular joint were excluded from the study.

      Methods The study is performed retrospectively on a prospective material. Examination with
      clinical examination, BMI, HRQoL questionnaire, dental casts, photography and two- and
      three-dimensional radiographs and cephalometric measures was performed prior to surgery.

      The patient's data (x-ray and photographs) were linked together in computer software programs
      and used for cephalometric analysis and simulation of the orthodontic and surgical movements
      (Fasad® and Simplant® PRO 12.00 OMS). The treatment was performed in accordance with this
      plan.

      The last follow up was performed 12 months after surgery including identical registrations as
      prior to surgery, described above. HRQoL questionnaires consisted of Oral Health Impact
      Profile (OHIP-S), Jaw Functional Limitation Scale (JFLS-20) and Orofacial Aesthetic Scale
      (OAS-S). The results from the presurgical questionnaire will be compared with the
      postsurgical results. Twenty subjects were asked to fill in the follow-up questionnaire twice
      with two weeks interval for a reliability test of the method.

      The pre- and postoperative CT will be compared in a software for measurements of upper airway
      volume with the software Philips IntelliSpace® Portal, version 11. Measures will be performed
      with an divided analysis of the upper airway according to the method described by Kim. Thus,
      the upper airway segmented into four compartments. The measurements will be performed on the
      sole segment volume and the total airway volume. A comparison of jaw movements, changes in
      airway volume, BMI and HRQoL will be performed.

      Statistical methods The sample size, 62 patients, was based on numbers included in previous
      similar studies from other centers.

      Simple statistics, mean and standard deviation (SD), for all variables will be used.
      Differences in airway volume and movements, preoperatively and postoperatively will be
      compared with McNemar's-test. Wilcoxon's paired-sample test will be used for analyzing airway
      volume before and after surgery as a numeric variable. The reliability test, performed as a
      test-retest, will be analyzed with the intraclass correlation coefficient, Fisher's test for
      pair comparisons and Pearson's correlation coefficient. Mann-Whitney-test will be performed
      to detect differences between questionnaire responses and clinical findings, i.e. BMI, and
      volumetric findings. The data will be assessed by using Spearman correlation analysis and
      simple linear regression analysis. Two-sided tests and alpha level 0.05 will be used.
      Confidence interval (CI) will be calculated. For all computations IBM® SPSS® statistical
      software will be used.
    

Intervention name(s): Orthognathic Surgery
Intervention type(s): Procedure
Intervention description(s): Surgical corrections of dentofacial deformities and malocclusions.
Observational model: Cohort
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        Consecutive patients, aged between 18 to 30 years, with diagnosed maxillary retrognatism
        and Angle class III occlusion deviating at least 5 mm in sagittal and/or vertical aspects
        from normal occlusion