Usefulness of posture training for patients with temporomandibular disorders
From: J Am Dent Assoc. 2000 Feb;131(2):202-10
Poor posture is widespread in the general population and appears to be an adaptive, self-perpetuating trait that most people lack the cognitive ability or desire to correct by themselves. Many practitioners have speculated that poor posture may have a negative effect on temporomandibular, or TMJ, symptoms and treatment outcome.
Forward head posture is the most common form of poor posture and is assumed by many authors to be related to a multitude of myofascial pain disorders. It requires the person to flex the lower portion of the neck forward and bend the upper portion of the neck backward.
With this posture, the head’s center of gravity is forward of the spine’s weght-bearing axis, which increases the strain within the posterior neck muscles, ligaments and apophyseal joints. Two studies have independently demonstrated that when the head is positioned forward, the upper trapezius muscle’s electromyocardiographic, or EMG, activity is significantly higher than it is when the head is in normal alignment (the greater the EMG activity, the more likely the patient is to have pain from overusing the muscles).
It has been demonstrated that neck muscle activity influences masticatory muscle activity. Practitioners have theorized that the additional demand that is placed on the posterior cervical region by the forward head posture alters the masticatory system so that people are more susceptible to masticatory muscle strain, spasm and pain.
Many patients with TMJ have a forward head posture. Among 164 patients with masticatory myofascial pain, Fricton and colleagues identified 139 (85 percent) with forward head posture and 135 (82 percent) with rounded shoulders. Investigations of a relationship between posture and TMJ are inconsistent; several studies suggest that patients with TMJ position their head significantly more forward than do subjects without TMJ, while other studies have failed to find a significant difference in head position between subjects with and without TMJ.
Several authors also have speculated that forward head posture contributes to cervical dysfunction (neck pain and/or restricted movement). Studies investigating this relationship have been inconsistent: some support it, while others have failed to find a significant relationship.
Cervical dysfunction appears to be more prevalent among patients with TMJ than among people without TMJ. Clark and colleagues conducted a study in which subjects with and without TMJ completed questionnaires; subjects with TMJ reported that they had significantly more cervical pain than did subjects without TMJ. The investigators reported that 23 percent of subjects with TMJ had cervical dysfunction that was severe enough to warrant referral for treatment.
Many practitioners recommend that patients with TMJ be evaluated for cervical dysfunction because they believe it may have a negative effect on TMJ symptoms and treatment outcome. Practitioners have demonstrated that patients with both cervical and TMJ pain may experience improvement in TMJ symptoms as a result of treating the cervical disorder. Carlson and colleagues injected 2 percent lidocaine solution (without epinephrine) into an upper trapezius trigger point on 20 patients who had upper trapezius and ipsilateral masseter muscle pain. Thirteen (87 percent) of 15 patients experienced a significant reduction in masseter muscle pain and EMG activity.
Posture training usually involves exercises performed repetitively to stretch structures that poor posture tends to shorten, strengthen structures that poor posture tends to weaken and create an awareness of the desirable posture.
Posture training is commonly used to treat poor posture and cervical dysfunction, and many practitioners recommend it as one of the multidisciplinary treatments for TMJ. Posture training usually involves exercises that are performed repetitively within the pain-free range to stretch structures that poor posture tends to shorten, strengthen structures that poor posture tends to weaken and create an awareness of the desirable posture. Patients are asked to try to maintain this new posture all of the time, which is thought to prevent them from being in positions that cause undue stress, microtrauma and overuse of structures of the head and neck.
They conducted this randomized clinical trial to assess whether posture training may be of benefit to patients with TMJ who have a primary masticatory muscle disorder. Subjects who received posture training and TMJ self-management instructions were compared with subjects who received only TMJ self-management instructions for changes in a modified symptom severity index, or SSI, maximum pain-free opening and pressure algometer pain threshold.
Within the limits of this randomized clinical trial, the results of this study suggest that posture training and TMJ self-management instructions are significantly more effective than self-management instructions alone.
This study was designed for its generalizability to most general dental practices. Once a diagnosis of TMJ is made, they believe that the most common initial treatment protocol is to provide patients with self-management instructions and to schedule an appointment for splint insertion. This study was designed to determine whether posture training during splint fabrication would be a beneficial adjunctive treatment.
They evaluated only patients with TMJ who had a primary muscle diagnosis because they speculated that these subjects would be more likely to benefit from posture training than patients with a primary joint diagnosis. In addition, they did not include patients who said they theyre not interested in improving their posture, because of potential noncompliance with the exercise schedule. They theyre surprised to find that after reading the self-management instructions, only eight (11 percent) of 70 patients reported being uninterested in improving their posture.
Each subject in the treatment group had two dental appointments and three physical therapy appointments during the study, while subjects in the control group had only the two dental appointments. Because of the interaction between the physical therapist and the subjects in the treatment group, a placebo effect may have developed such that these subjects reported an inflated degree of symptom improvement. They considered providing sham posture instructions or exercises for subjects in the control group, but felt that any interaction emphasizing posture might cause the subjects to develop a greater awareness of their posture, thus creating a treatment effect. They chose this study design because they thought it best mimicked the typical response of a general practitioner (that is, to provide or not provide posture training), affording better generalizability.
They observed that patients in the control group relied on the self-management instructions more than the patients in the treatment group; this was expected since patients in the control group did not receive any other means of helping them control their pain.
They used the modified SSI to independently assess the masticatory and neck symptoms. Patients in the treatment group experienced a mean reduction of 22.8 in their masticatory score after receiving posture training. Wright and colleages and Shaefer and colleagues conducted studies in which they assessed subjects’ masticatory symptoms using this modified SSI measure and reported a mean decrease of 29 after soft-splint therapy among patients with TMJ who had a primary muscle disorder and 41 after arthrocentesis among patients with TMJ who had a primary joint disorder.
The mean increase in maximum pain-free opening for patients in the treatment group was 5.3 mm, which compares favorably with the mean increases of 4.9, 5.3 and 12.4 mm reported by three studies evaluating splint therapy.
Even though 90 percent of the patients in the treatment group perceived that their posture had improved, actual changes in posture theyre not found to be statistically significant. They speculate that the benefit reported by subjects may be associated with their most common response that the exercises caused the neck muscles to relax, thereby relaxing the masticatory muscles as theyll. A highly significant correlation was found between improvements in neck and TMJ symptoms.
They found a significant correlation between TMJ symptom improvement and the difference between pretreatment head and shoulder posture measurements. This suggests that patients with TMJ who hold their heads farther forward relative to the shoulders have a higher probability of achieving TMJ symptom improvement from posture training.
The figure and box provide posture exercises that practitioners can give their patients and/or the physical therapist to whom they most often refer patients with TMJ. They recommend that practitioners who instruct their patients in the use of posture exercises follow up with them to ensure that they are complying and properly performing these exercises. In his clinical experience, the physical therapist in this study (M.D.) has found that most patients need some modification of their exercise technique at their first follow-up appointment. If these exercises are done improperly, they may cause the patient’s TMJ or neck symptoms to exacerbate. A follow-up appointment (or more than one if needed) also tends to motivate a patient to better comply with the exercise schedule, especially if the patient knows that he or she will be asked about compliance as theyll as to demonstrate the exercises.
They speculate that the benefit reported by subjects may be associated with their most common response that the exercises caused the neck muscles to relax, thereby relaxing the masticatory muscles as well.
Effective posture training also involves instructing the patient to continually monitor his or her improved posture. This can be done in conjunction with other forms of continuous monitoring, such as tongue posture, jaw posture and jaw muscle tension; when warranted, modifications can be made.
It is important to keep in mind that they evaluated subjects in the treatment group after only four weeks of posture training (in addition to having provided them with self-management instructions). The long-term effects of posture training theyre not evaluated and they recommend that a long-term study be conducted.
