Deep muscle pain, tender points and recovery in acute whiplash patients: a 1-year follow-up study.

Local sensitization to noxious stimuli has been previously described in acute whiplash injury and has been suggested to be a risk factor for chronic sequelae following acute whiplash injury. In this study, we prospectively examined the development of tender points and mechano-sensitivity in 157 acute whiplash injured patients, who fulfilled criteria for WAD grade 2 (n=153) or grade 3 (n=4) seen about 5 days after injury (4.8+/-2.3) and who subsequently had or had not recovered 1 year after a cervical sprain. Tender point scores and stimulus-response function for mechanical pressure were determined in injured and non-injured body regions at specific time-points after injury. Thirty-six of 157 WAD grade 2 patients (22.9%) had not recovered, defined as reduced work capacity after 1 year. Non-recovered patients had higher total tender point scores after 12 (p<0.05), 107 (p<0.05) and 384 days (p<0.05) relative to those who recovered. Tenderness was found in the neck region and in remote areas in non-recovered patients. The stimulus-response curves for recovered and non-recovered patients were similar after 12 days and 107 days after the injury, but non-recovered patients had steeper stimulus-response curves for the masseter (p<0.02) and trapezius muscles (p<0.04) after 384 days. This study shows early mechano-sensitization after an acute whiplash injury and the development of further sensitization in patients with long-term disability.