Efficacy of Acute Pain Management on Chronic Pain Following Lower Extremity Trauma

Abstract

Background: Many patients with traumatic injuries report chronic pain, with injuries to the lower extremity resulting in higher rates than other sites. High pain intensity at the time of injury is a risk factor for chronic pain, but it is not clear what specific acute pain patterns following injury influence the development of chronic pain. In addition, it is not known whether chronic pain in this patient population includes symptoms of heightened sensitivity to innocuous and noxious stimuli, which have been reported in other chronic pain conditions. Purpose: To examine the relationship between post-trauma acute pain status and the incidence of chronic pain, and to test for hypo- or hypersensitivity to innocuous and noxious thermal and mechanical stimuli in patients with lower extremity traumatic injuries. Methods: This was a descriptive retrospective cohort study with a cross-sectional component. Patients were contacted by telephone and their pain related to the injury site was assessed. This was followed by a retrospective medical chart review. A sub-sample of patients and healthy controls also underwent sensory testing. Results: In this study 54% of patients experienced no improvement in pain during hospitalization. The mean pain score was higher for patients with chronic pain (78%) compared to patients with no chronic pain (5.1 vs. 4.2), but there were no significant difference between the group based on the pain trajectory. Patients with injuries had higher warmth detection threshold (36.5 vs. 33.2), and current perception threshold (CPT) stimulus-response at 2000 Hz (292 vs. 122) and 250 Hz (76 vs. 35) compared to healthy controls. Conclusion: Consistent with other studies, high pain intensity at the time of injury was associated with chronic pain. The increased warmth perception threshold and increased CPT stimulus-response in cases suggest hypoesthetic nerve function. This is the first study to conduct an in-depth analysis of acute pain intensity patterns and sensory function in patients with traumatic lower extremity injuries and will guide the design of a future longitudinal study.