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ABSTRACT: The aim of this study was to verify possible relationships between global body posture and temporomandibular joint internal derangement (TMJ-id), by comparing 30 subjects presenting typical TMJ-id signs to 20 healthy subjects. Body posture was assessed using the analysis of muscle chains on several photographs. Results show a higher frequency of lifted shoulders (p=0.04) and of changes in the antero-internal hip chain (p=0.02) in the test group, but no further differences were found significant between the control and test groups. The test group was then divided into three subgroups according to the Helkimo index of temporomandibular disorder severity. Again, no significant differences were found between the subgroups. However, there was a trend noticed in the group with the most severe dysfunction, to present a forward head and shoulders posture. Results are discussed in light of previous studies using the same sample.
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The stomatognathic system comprises a complex set of orofacial structures, linked by a broad network of sensomotor neural connections peripheral to the central nervous system, which are related to masticatory, phonation, and deglutition functions.
A temporomandibular system may be conceived of as part of the stomatognathic system, including temporomandibular joints (TMJ), masticatory muscles and associated ligaments, plus the aforementioned neural structures. Its functions are mandible positioning and moving, as well as maintaining its rest posture. Whether of morphologic or functional origin, failure of these musculoskeletal structures bring about diverse clinical conditions which have been generic ally defined as temp oromandibular dysfunctions (TMD).
Though traditionally both physiology and treatment of the stomatognathic system have been conceived of as apart from the system that manages global body posture, there is clinical evidence of mutual interdependence between both. Such interrelations are manifested by morphologic or functional alterations in the stomatognathic system structures, brought about by acute (1-16) or chronic (17,18) changes in body posture or vice-versa. (19-26)
The physiology involved in these interrelations has broadly been explained by biomechanical theories, (8,27,28) i.e., that changes of tissue tension-compression in one region are generated by changes in another--and by neuromuscular-grounded theories, (9,10,12,15) i.e., changes in the electromyographic activity of muscles in one region might be due to position changes in the other.
According to a major physical therapy current, muscle groups responsible for posture maintenance are organized and operate following a pattern known as muscle chains. (29-32) Posture changes in a muscle segment could lead to the elongating or shortening of adjacent muscles, which can interfere in the physiology of the masticatory muscles. Muscle chains are the fundamentals of a body posture rehabilitation technique called global posture reeducation (GPR). (29-34)
In view of the available evidence of functional interrelation between body posture and mandible operation, some authors suggest that changes in body posture may be closely linked to TMD. (35-37)
Several studies have reported a higher frequency of body posture alterations in subjects with TMD when compared to healthy subjects, (38-48) while others found no relationship between body posture and TMD. (49-51)
Similarly, a previous study (52) under the same authorship analyzed the body posture of subjects with TMJ internal derangement using a quantitative analysis of photograph tracings and comparing them to those of a group with healthy temporomandibular system. No significant differences in body posture could be found between the two groups. The same subject sample had their body posture analyzed by means of cervical spine radiography in another study, (48) where a higher frequency of hyperlordosis was found in individuals with TMJ-id than in healthy subjects.
The present study aims at assessing body posture by the analysis of muscle chains in the same sample of individuals with TMJ-id analysed in those previous studies, searching for possible relations between TMD severity and changes in body posture.
Materials and Methods
The subjects who took part in the study were 50 individuals aged 16 to 35, who were divided into test and control groups. The former was made up of 30 subjects with TMJ-id (three male, 27 female, mean age 21.7 [+ or -] 3.6 yrs). The control group had 20 subjects (six male, 14 female, mean age 22.9 [+ or -] 5.3 yrs). Groups were homogenous as to gender, age and ethnicity (Table 1).
The test group subjects were randomly selected among outpatients at the Orofacial Pain and TMJ Clinic at the Hospital das Clinicas of the University of Sao Paulo (USP) School of Medicine; all subjects presented symptoms compatible with TMJ-id, with or without an associated myogenous component.
The control group consisted exclusively of individuals with fully healthy temporomandibular system, assessed by the anamnestic and dysfunctional indexes proposed by Helkimo, (53) with no previous or current history of TMD.
A detailed account on selection criteria for these groups has been previously published. (47,48,52) All subjects gave their explicit consent to take part in the study, which was approved by the Bioethics Committee of the USP Hospital das Clinicas.
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