Abstract
The aim of the study was to compare the thickness and cross-sectional area (CSA) of masseter and medial pterygoid muscles in young patients with long-standing bilateral temporomandibular joint ankylosis (bTMJA) in relation to controls. Axial sections of computed tomography scans of patients with bTMJA from two tertiary care university hospitals were reviewed from 1995 to 2010 and compared to age- and sex-matched controls. The outlines of masseter and medial pterygoid muscles corresponding to a predefined reference plane were traced onto acetate paper. The thickness and CSA of the muscles were calculated using an image-analyzing software and calibrated according to the scale provided in the CT scan slides. Out of a total of 167 cases of temporomandibular joint ankylosis (TMJA), 15 fulfilled the inclusion criteria. The mean thickness and CSA of masseter and medial pterygoid muscles in cases of bTMJA were 19.4 mm (SD 2.3), 734.9 mm(2) (SD 156.7), 11.53 mm (SD 1.35), and 267.4 mm(2) (SD 65.35), respectively. For the control group, respective values were 10.5 mm (SD 1.8), 430.1 mm(2) (SD 66.8), 9.2 mm (SD 1.2), and 254.6 mm(2) (SD 45.7). There was a statistically significant increased thickness and CSA of the muscles in cases of bTMJA as compared to control as evaluated by Mann-Whitney U test. The results show that thickness and CSA of masseter and medial pterygoid muscles in patients with bTMJA were larger as compared to controls. This may suggest that, muscular hyperactivity, may be a cofactor in the pathogenesis of TMJA. Although temporomandibular joint ankylosis is one of the most restrictive musculoskeletal disorder in the maxillofacial region, there is little information on the form and function of jaw muscles in this condition. This study evaluates thickness and cross-sectional areas of jaw elevator muscles and indicates that muscle hyperactivity might be associated with ankylosis, thereby providing a probable hypothesis on the etiopathogenesis of this condition.
Published Version
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