Prediction and trend of tactile acuity, pain and disability in acute LBP: a six-month prospective cohort study

BACKGROUND: Chronic back pain is known to be associated with altered tactile acuity. Tactile acuity is measured using the Two-Point Discrimination (TPD) test in both clinical and research settings. In subjects with chronic low back pain, the TPD threshold (TPDT) is increased and is associated with persistent pain. It remains unknown, however, whether TPDT is also altered in cases of clinical acute pain, or whether it could be used as a predictor of future pain and disability at an early stage of LBP. The main objective of this study was to investigate the predictive value of baseline TPDT for pain and disability at 3 and 6 months after the onset of acute LBP. The TPDT in acute low back pain (LBP) and the development of TPDT over 6 months has also been assessed. METHODS: LBP participants (n = 124) with acute LBP (< 4 weeks) were included. Subjects were examined within 4 weeks of pain onset and followed-up after 3 and 6 months of pain onset. Horizontal and vertical TPDTs of the lower back were collected. Linear mixed models were subsequently used to evaluate the association of TPDT with pain and disability over time. RESULTS: The vertical TPDT showed a mean (SD) of 4.9 cm (1.6) and the horizontal TPDT a mean (SD) of 6.0 cm (1.5) at baseline. The vertical TPDT altered from baseline up to 6 months from 4.9 to 4.6 cm and the horizontal TPDT from 6.0 to 5.4 cm. The association between the TPDT and the Oswestry Disability Index (ODI) after 6 months was moderate. Linear mixed models revealed no association between TPDT, pain and disability over the progression of LBP. CONCLUSION: TPDTs appear to be raised in subjects with acute LBP. However, our study revealed no predictive capability of the TPDT for disability and pain. No comparisons are possible in the absence of similar studies, indicating the need for further research is in this area.