Unexplained falls in chronic back pain: A proposed neuromuscular physiologic explanation

Patients with chronic pain (CP) report unexplained falls. Few articles discuss chronic pain associated with increased risk of falling. In a private office based practice consisting of 600 patients age 25 to 70 with chronic low back and other types of pain, falls and consequential injuries have been documented. Over a 3-year span, pictures of superficial injuries were collected. Fifty-five patients had a total of 88 visible injuries, mostly contusions and abrasions. The injury location was 15 head, 15 trunk and 14.5 injuries per limb. In contrast to this random distribution, Census Bureau data in women ages 49 to 60 in 2000 through 2003 showed fractures predominantly in the radius and ulna, indicating the presence of protective reflex after loss of balance. The random distribution of injuries in patients with chronic pain cannot be explained by traditional concepts of environmental influence or osteoporosis.

Previously published studies about the physiology of the back and chronic pain can be used to support a new concept about the etiology of falls in CP. The supporting concepts include patient descriptions of events, physiology of motion and function of normal and abnormal discs, the abnormally brisk reflexes in chronic pain due to loss of supraspinal inhibitory signals that provide a blanketing effect on myotatic reflex signals.

In this proposed model, a noxious and/or mechanical stimulus in the trunk or periphery, in the presence of heightened reflexes and absence of normal inhibitory supraspinal reflexes, triggers a flexor withdrawal reflex causing loss of limb control.