Comparison of low back pain sites identified by patient's finger versus hand: prospective randomized controlled clinical trial.

Background: Accurate diagnosis and appropriate therapy for low back pain are based on knowledge of the site of the patient's pain. In clinical settings, patients generally indicate the site of low back pain using the hand, but Chapman and Syrjala as well as Macnab recommended that the patient should indicate the site with the finger. Whether any differences emerge from these methods is an important fundamental question. The purpose of this study was to compare low back pain sites identified by the patient's finger versus the hand. Specifically, we conducted a prospective randomized controlled comparison and investigated the surface area and the accuracy of the sites indicated by the two identifications.
Methods: Subjects were 137 low back pain patients meeting the following criteria: (1) age 18-65 years; (2) low back pain induced by lumbar flexion, extension, or lateral bending while standing; (3) absence of leg pain; and (4) pain at only one site. Subjects indicated the site of pain by hand and by index finger immediately after provocation of pain. A demonstrably reproducible site was outlined on the skin. The outlines of the sites were recorded and verified by digital images. The body surface area of the sites was determined using NIH Image Version 1.61. Sites identified by hand versus index finger were compared on the surface area. Additionally, to compare the accuracy of the two identifications, patients were asked which of two sites more accurately represented the pain site in outline form after the two identification procedures.
Results: The surface area of sites identified by the finger was significantly smaller than that of sites identified by the hand (P < 0.05). Furthermore, a considerably higher proportion, approximately 80%, of patients answered that the site of the pain was identified more accurately by finger than by hand.
Conclusions: The indication by a finger resulted in more accurate, localized identification of the site of low back pain than the indication by a hand. The identification of the pain site with a patients' finger indication does not directly clarify the etiology of low back pain, but it has the potential to provide important information useful for making an accurate diagnosis and for determining the appropriate therapy.