Obstructive sleep apnea (OSA) is common in patients with bilateral temporomandibular joint ankylosis (TMJA). The purpose of this study was to compare the preoperative and postoperative apnea-hypopnea index (AHI) in patients with TMJA undergoing bilateral gap arthroplasty (BGA).
The investigators implemented a prospective cohort study on patients with bilateral TMJA treated with BGA. The primary predictor variable was time (before and after BGA). The primary outcome variable was AHI and secondary outcome variable included posterior airway space, skeletal changes, Epworth sleepiness scale, minimum oxygen , average oxygen saturation, and maximal incisal opening at preoperative time (T0), 1 month (T1), and at 6 months (T2). The statistical test used were Greenhouse-Geisser test, repeated measure ANOVA (1 way), followed by post hoc Bonferroni test. The P -value was taken significant when <0.05 at a confidence interval of 95%.
The study sample included 12 (m:f = 1:2) patients of bilateral TMJA with a mean age of 14.9 ± 4.8 years and mean follow-up of 6 months. Mean duration of ankylosis was 10.5 ± 6.9 years (median = 12). Trauma was the main etiological factor in 11 (91.7%) patients followed by infection in 1 (8.3%) patient. The mean increase in AHI was 8.6 (T0 to T1) with P -value = .002 and 23.4 (T1 to T2) and was statistically significant ( P = .001). The mean decrease in posterior airway space was 4.5 ± 1.0 to 3.5 ± 0.5 (T0 to T2) and was statistically significant ( P = .02). Mean difference in minimum oxygen was 6.8 ( P -value = .015). Skeletal changes are consistent with clockwise rotation of the mandible and statistically significant changes in horizontal and vertical dimension. The mean change in average oxygen was statistically insignificant ( P = 1.0).
The present study concludes that gap arthroplasty in patients with bilateral TMJA can lead to development or worsening of pre-existing mild to moderate OSA. Ramus-condyle reconstruction should be performed to prevent the retropositioning of mandible and worsening of OSA.
Temporomandibular joint ankylosis (TMJA) causes immobility of joint and inability to open mouth. Treatment of the condition includes arthroplasty with or without interposition of autogenous/alloplastic material and distraction osteogenesis. In case of patients with bilateral TMJA, obstructive sleep apnea (OSA) is the most important factor to be taken into account. The mandible in patients with bilateral TMJA may become retrognathic and posteriorly positioned depending on the age of onset and duration of ankylosis (DOA) that can create a decreased oropharyngeal airway space leading to obstruction in breathing. Oropharyngeal airway space is defined by a line parallel to the palatal plane vertically, epiglottis inferiorly, posterior pharyngeal wall, anteriorly by the soft palate, uvula and posterior border of the tongue, as well as the lateral pharyngeal areas. The space available for the tongue is diminished and along with that tonicity of suprahyoid muscles decreases during sleep. This can lead to fall back of the tongue thus further diminishing the airway resulting in episodes of apnea/hypopnea. Increased muscle tone during wakefulness compensates for the narrowed airway; however, these protective reflexes become blunted during sleep allowing the airway to collapse. Subsequently, resistance to airflow increases and the arousal breaks the cycle from sleep. Repetitive collapse of upper airway while sleeping is characteristic of retrognathic mandible. The result of such airway obstruction is OSA. This disorder is characterized by recurrent apnea during sleep despite persistent respiratory efforts. Frequent partial arousal occurs during sleep, resulting in relative sleep deprivation and daytime sleepiness.
The physiological consequences of these episodes are decreased oxygen saturation, nocturnal hypoxia, hypercapnia, respiratory acidosis, repetitive bursts of sympathetic activity, and cardiac arrhythmias. The individual with OSA also has higher predisposition to development of atherosclerotic plaques in the carotid arteries, making a thromboembolic event a possibility. , In-laboratory nocturnal polysomnography (PSG) has been the gold standard for diagnosis of OSA. A typical 8-hour nocturnal laboratory PSG involves measurement of multiple channels of physiological parameters including electroencephalogram, electro-oculography, chin movements, leg movements via electromyography, electrocardiograph, heart rate, respiratory efforts, chest wall movements, abdominal wall movements, airflow, and oxygen saturation. The apnea-hypopnea index (AHI) is the primary measure used to determine the severity of OSA and effectiveness of treatment. OSA is classified as mild (AHI: 5-15), moderate (AHI: 15-30), and severe (AHI>30). There are studies reporting worsening of or development of sleep-related breathing disorder after maxillomandibular setback surgery. This may be true in the patients who had presurgery compromised airway. In contrary to this, some authors reported no evidence of OSA after mandibular setback. With a normal positioned maxilla, an increased oropharyngeal airway dimension commonly accompanies in purely mandibular prognathic patients, so the setback should not create an OSA situation unless the patients are significantly obese.
Evidence-based literature on the effects of arthroplasty for patients with bilateral TMJA is nonexistent. The purpose of the study was to evaluate the changes in the status of OSA after bilateral gap arthroplasty (BGA) in patients with TMJA by PSG and cephalometric parameters. The investigators hypothesized that the BGA would worsen the AHI and posterior airway space (PAS). The specific aim of the study was to evaluate AHI, PAS, average oxygen (AvgO 2 ), and minimum oxygen (MinO 2 ) saturation level before and after BGA.
Patients and Methods
To address the research question, the investigators designed and implemented a prospective cohort study on patients with bilateral TMJA. The study was approved by the institute ethical committee. The study sample was composed of all the patients presenting for management of TMJA between July 2014 and November 2015. Patients with bilateral TMJA with mild to moderate OSA were included in the study as OSA may be magnified in cases of severe OSA secondary to TMJA. Patients were excluded as study subjects if they had a previous history of distraction osteogenesis, severe OSA which might need tracheostomy, or continuous positive airway pressure (a form of positive airway pressure ventilation in which a constant level of pressure above atmospheric pressure is continuously applied) as primary treatment and OSA secondary to central causes.
Patients with a minimum follow-up of 6 months were included in the study. The primary predictor variable was time (before and after BGA). AHI was the primary outcome variable and secondary outcome variable included PAS, skeletal changes, ESS score, MinO 2 , AvgO 2 saturation, and maximal incisal opening (MIO). Other variables such as age, sex, etiology, and DOA were also recorded. MIO was measured using a straight millimeter ruler from the upper incisor tip to the lower incisor tip, without any assistance. If the patients had open bite in the follow-up period, it was subtracted from the measured MIO.
Data Collection Methods
Baseline data, lateral cephalogram, and PSG were performed preoperatively (T0), at 1 month (T1) and 6 months (T2) follow-up. All the patients were counseled and encouraged for active postoperative mouth-opening exercise using a tapered threaded acrylic trismus screw. Patients were followed for a minimum of 6 months for PSG. Patients were followed beyond 6 months for any sign and symptoms of reankylosis and adverse effects of OSA.
Cephalograms were taken with the head in standardized natural head position. No instruction was given to the patients regarding swallowing during the procedure. All the cephalograms were hand traced on acetate paper. The following landmarks and measurements were localized to obtain respective PAS measurements ( Table 1 ), ( Fig 1 ). In addition to this, skeletal changes were also evaluated. For skeletal changes, the points and measurements used are described in Table 2 .
|Posterior nasal spine (PNS)||The most posterior point on the sagittal plane of the bony hard palate on the mid-sagittal plane|
|Uvula (U)||The most posteroinferior point of the uvula|
|Vallecula (V)||The intersection of epiglottis and the base of the tongue|
|Basion (Ba)||The most caudal point on the base of the sphenoid makes the anterior boundary of the foramen magnum which makes the point basion|
|Upper pharyngeal wall (UPW)||PNS-Ba (basion) line and posterior pharyngeal wall|
|Middle pharyngeal wall (MPW)||Intersection of a perpendicular line from U with the posterior pharyngeal wall|
|Lower pharyngeal wall (LPW)||Intersection of a perpendicular line from point V with the posterior pharyngeal wall|
|U-MPW||The distance between U and MPW represent the upper oropharyngeal airway space|
|PAS min||The minimum distance between the base of tongue and the posterior pharyngeal wall, which represent the minimal pharyngeal airway space (middle oropharyngeal airway)|
|V-LPW||The distance between V and LPW represent the hypopharyngeal airway space|
|Sella (S)||The geometric center of the pituitary fossa located by visual inspection|
|Nasion (N)||The most anterior point of the frontonasal suture in the midsagittal plane|
|Articulare (Ar)||A point at the intersection of the posterior border of the ramus and inferior border of the cranial base|
|Gonion (Go)||Using 2 lines, 1 tangent to the inferior border of the mandible and the other tangent to the posterior border of the ramus, locate gonion on the curvature of the mandibular angle by bisecting the angle formed by the 2 lines|
|Gnathion (Gn)||A point midway between pogonion and menton on the outline of the symphysis|
|Pogonion (Po)||The most anterior point of the bony chin in the midsagittal plane|
|Menton (Me)||The most inferior point of the outline of the symphysis in the midsagittal plane|
|Point A||(Subnasale; the deepest midline point on the anterior outer contour of maxillary alveolar process)|
|Point B||(Supramentale; the deepest point on the outer contour of mandible)|
|Porion (Po)||Most superior and outermost point on bony external auditory meatus|
|Orbitale (Or)||Most inferior point on orbital margin|
|Frankfort-horizontal plane (FH)||Line from point porion to orbitale|
|H-point||Anterior-superior point of hyoid bone|
|L1 tip||lower incisor tip|
|U1 tip||Upper incisor tip|
|U6||Mesial cusp of upper first molar|
|L6||Mesial cusp of lower first molar|
|Ramal height||Distance between Ar to Go|
|Anterior facial height||Distance between N to Me|
|Posterior facial height||Distance between S-Go|
|Mandibular plane||Gonion to gnathion|
|Incisor-mandibular plane angle||Angle formed by intersection of mandibular plane with line passing through long axis of lower incisors|
|Mandibular plane angle||Angle formed by intersection of the FH plane and the mandibular plane|
|Facial angle (FH to N-Po)||It is inferior inside angle formed between line from N-Po and FH plane|
|Hyoid-mandibular plane distance||Perpendicular distance between mandibular plane to hyoid (H)|
For presurgical and postsurgical vertical changes in the mandible position, Frankfort-horizontal (FH) plane was drawn (from porion to orbitale); perpendicular distance was measured from the FH plane to point B and pogonion. For horizontal distance, a perpendicular line was drawn from nasion (N-Per) and from point B and pogonion to the FH plane. The linear horizontal distance was measured between 2 lines (N-Per and perpendicular from pogonion and point B). This horizontal linear distance was measured and this will indicate horizontal positional change in the mandible ( Fig 1 ).
Standard surgical technique osteoarthrectomy surgical procedure was followed. Preauricular with extended temporal surgical incision was used for osteoarthrectomy. As per departmental protocol, a piezoelectric saw was used for osteoarthrectomy and the ankylotic mass was removed at maximum and minimum diameter. A gap of approximately 1.5 to 2 cm was in accordance with the dimension of ankylotic created. We used piece meal technique instead of removing ankylotic mass in 1 piece. Buccal fat pad was readily mobilized from the same surgical incision to fill the dead space to prevent heterotopic bone formation. Intermaxillary fixation was not used in any patient. All the patients followed a rigorous postoperative mouth-opening exercise protocol ( Table 3 ).
|S.no||Postoperative Period||Exercise Regimen|
|1||8 to 36 hours||10 to 15 insertions per try, and 5 or 6 tries daily (or as per pain threshold)|
|2||48 to 96 hours||20 to 25 insertions per try and 8 to 10 tries daily|
|3||7 th to 10 th day||>50 insertions per try and 10 to 12 tries daily|
|3||3 rd to 4 th week||>50 insertions per try and 10 to 12 tries daily|
|4||If MIO stable for 6 months||20 to 25 insertions thrice daily|
|5||After 6 months if MIO smooth, stable, and no morning tightness in mouth opening||As per patient preference|