Injury threshold: Whiplash associated disorders

Objectives: To review current knowledge and recent concepts of the causes o f injuries after minor impact automobile collisions and to acquaint those w ho treat these types of injuries with possible injury thresholds and mechan isms that may contribute to symptoms. Data Sources: A review of literature involving mechanisms of injury, tissue tensile threshold, and neurologic considerations was undertaken. A hand-se arch of relevant engineering, medical/chiropractic, and computer Index Medi cus sources in disciplines that cover the variety of symptoms was gathered. Results: Soft-tissue injuries are difficult to diagnose or quantify. There is not one specific injury mechanism or threshold of injury. With physical variations of tissue tensile strength, anatomic differences, and neurophysi ologic considerations, such threshold designation is not possible. Conclusions: To make a competent assessment of injury, it is important to e valuate each patient individually. The same collision may cause injury to s ome individuals and leave others unaffected. With the variability of human postures, tensile strength of the ligaments between individuals, body posit ions in the vehicle, collagen fibers in the same specimen segment, the amou nt of muscle activation and inhibition of muscles, the size of the spinal c anals, and the excitability of the nervous system, one specific threshold i s not possible. How individuals react to a stimulus varies widely, and it i s evident peripheral stimulation has effects on the central nervous system. It is also clear that the somatosensory system of the neck, in addition to signaling nociception, may influence the control of neck, eyes, limbs, res piratory muscles, and some preganglionic sympathetic nerves.