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Background/Purpose: Maximum mouth opening (MMO) is a useful parameter to identify common temporomandibular joint (TMJ) disorders. Up to now, a few studies addressed the issue on MMO normal values in pediatric population, according to age and/or presence of generalized joint hypermobility (GJH), therefore it is not widely used in general medical practice. Aim of the study was to evaluate the MMO in a cohort of healthy schoolchildren and to propose a new parameter, the three middle finger width (TMFW), the distance between 2nd and 4th fingers of the right hand at the level of the lowest nail bed, to evaluate the TMJ hypermobility in children. We also analyzed the relationship between GJH and TMJ hypermobility. Methods: We conducted a cross sectional study in a cohort of healthy schoolchildren, aged 8-13 years. Information on family history of GJH and history of TMJ involvement were collected. Physical examination included height, weight, body surface area (BSA), body mass index (BMI) and musculoskeletal evaluation focused on the presence of GJH according to the Beighton criteria (BS>=4/9). TMJ evaluation included a complete gnathological visit, aimed to investigate the presence of TMJ disorders and to measure the MMO. The evaluation of TMFW was also performed and the Mouth Opening Ratio (MOR) was then calculated by the formula [(MMO-TMFW)/ MMO]x100, adopting a 10% cut-off value to define the TMJ hypermobility. Results: Two hundred and eighty-eight schoolchildren, 143 females and 145 males, entered the study. Mean MMO was 45.57 mm (+/-5.12) for males and 44.87 mm (+/-4.98) for females. Mean TMFW was 43.03 mm (+/-4.09) for males and 41.71 mm (+/-3.84) for females. Both MMO and TMFW significantly correlated with all growth parameters (height, weight, BMI and BSA). 89 subjects (30.9%) showed TMJ hypermobility (MOR>10%). In these subjects and in those with normal MOR, MMO correlated with TMFW (r= 0.761, p<0.001 and r= 0.786, p<0.001 respectively) although in the first group MMO showed an higher level distribution. The prevalence of subjects with GJH was significantly higher in the group with TMJ hypermobility than in the other (44.8% vs 21.5% p<0.001). Conclusion: TMFW correlates with MMO in schoolchildren and may represent a simple and reliable method to evaluate TMJ abnormalities. MOR, as an index to identify TMJ hypermobility, correlates with the presence of GJH and could be reasonably included, as an adjunctive feature, to the Beighton Criteria.
Sperotto, F., La Falce, G., Vittadello, F., Balzarin, M., Favero, L., & Zulian, F. (2013). PReS-FINAL-2264: Three middle fingers width correlates with maximum mouth opening and is a reliable parameter to identify joint hypermobility in schoolchildren. Pediatric Rheumatology, 11(S2). https://doi.org/10.1186/1546-0096-11-s2-p254