Biomechanics of TMJ Injury from Whiplash
The issue of temporomandibular joint (TMJ) pain after whiplash injuries is a complex and controversial issue. Heise1 reported TMJ pain rates after whiplash from 12 to 15%, indicating that TMJ pain is not uncommon to whiplash patients. Indeed, a number of studies in the last few years have attempted to determine how these types of injuries occur and how whiplash TMJ pain differs from ordinary TMJ pain (see following study).
A current report from the researchers at the Biodynamic Research Corporation2 examined the problem of TMJ injury by studying the fourteen test collisions with live human subjects. Their goal was to detail the motions of the spine and TMJ, and try to determine a possible injury mechanism.
The researchers performed the tests at ranges of 2.4-6.8 mph. None of the test subjects reported TMJ symptoms immediately after the test or at a three year follow-up.
The authors found no evidence of abnormal TMJ motion during the test collisions. "There is no basis for TMJ ligament stretch since there is no distraction. The compressive forces, moreover, were only fractions of compressive forces imposed physiologically at the TMJ."
From this study, and others, it seems that the TMJ is not injured directly in low speed collisions. If this is so, what is the source of TMJ pain?
Krogstad et al3, reported elsewhere in this issue, offer some potential suggestions. They found that there were differences between patients with ordinary TMJ pain and those with whiplash-related TMJ pain.
First, they cite other studies that show that TMJ pain after whiplash may not be caused by actual joint dysfunction:
"The incidence of clicking and TMJ pain in whiplash patients was found to be extremely low by Heise et al.1 Garcia and Arrington4 found in an MRI study, however, that 72% of 87 whiplash patients demonstrated anterior disc displacement with reduction and that 15% demonstrated disc displacement without reduction. In another study, internal derangements were seen arthrographically in 22 of 25 whiplash patients. However, disc displacement has been found in asymptomatic volunteers as well, which indicates that the whiplash patients could have had an asymptomatic disc displacement before the accident." 3
There is some speculation by the authors that general muscle dysfunction may play a role in TMJ symptoms in whiplash patients. "Their general muscle problems may affect posture, respiration pattern, and general body function, increasing their whiplash-associated symptoms."3 These physical reactions to whiplash may have some impact on TMJ symptoms.
Stress, a well-recognized issue that is closely related to TMJ pain, may also play some part. Stress may encompass "worry, ruminations, disturbing thoughts about illness symptoms, and a change in lifestyle..."3
Another possibility is the fact that TMJ pain and other conditions overlap each other, and may be confused. One recent study by Cimino et al5 compared a group of women with jaw pain to a group of women with fibromyalgia. After examining both groups for jaw clicking, masticatory muscle pain, headache, and jaw opening, the researchers concluded that they could detect no statistical differences between the two groups. This study suggests that a more widespread pain condition—like whiplash or fibromyalgia—may exhibit some of the same symptoms as TMJ pain.
- Heise AP, Laskin DM, Gervin AS. Incidence of temporomandibular joint symptoms following whiplash injury. Journal of Oral Maxillofacial Surgery 1992;50:825-828.
- Howard RP, Bowles AP, Guzman HM, Krenrich SW. Head, neck, and mandible dynamics generated by 'whiplash.' Accident Analysis and Prevention 1998;30(4):525-534.
- Krogstad BS, Jokstad A, Dahl BL, et al. Somatic complaints, psychologic distress, and treatment outcome in two groups of TMD patients, one previously subjected to whiplash injury. Journal of Orofacial Pain 1998;12(2):136-144.
- Garcia R, Arrington JA. The relationship between cervical whiplash and temporomandibular joint injuries: an MRI study. Journal of Craniomandibular Practice 1996;14:233-239.
- Cimino R, Michelotti A, Stradi R, Farinaro C. Comparison of clinical and psychologic features of fibromyalgia and masticatory myofascial pain. Journal of Orofacial Pain 1998;12(1):35-41.