Diurnal variation in stature: Do those with chronic low-back pain differ from asymptomatic controls?

Background: Stature loss is a commonly used measure of spinal load. The aim of this study was to investigate the pattern of diurnal stature change in those with and without chronic low-back pain, over a 24-h period. Methods: Eight participants with chronic low-back pain (age 24.6 (SD 4.3) years, height 1.76 (SD 0.08) m, body mass 72.8 (SD 11.1) kg) and eight controls (age 21.8 (SD 2.0) years, height 1.75 (SD 0.10) m, body mass 71.8 (SD 11.6) kg) participated in this investigation. Twenty-four stature measurements were performed over a 24-h period. Findings: The trough to peak variation in stature of 17.9 mm (low-back pain group) and 17.6 mm (control group) did not differ between groups (P > 0.05). Both groups experienced greatest stature change in the 1st hour after rising (31.3% [low-back pain] and 44.6% [control] of total stature change). At approximately 18:00 h the LBP group reached a plateau whilst the control group continued to lose stature. Between 14:00 and 18:00 h both groups demonstrated a previously unreported recovery of stature. A significant correlation was found between low-back discomfort and stature change in the low-back pain group only. Interpretation: No significant difference existed between groups in relation to total stature loss; however the low-back pain group appeared to reach their nadir earlier, possibly exposing other spinal structures to loading for a greater duration. This is supported by the relationship found between stature loss and discomfort. The reversal in stature loss in the afternoon may be of clinical significance and warrants further investigation. (C) 2010 Elsevier Ltd. All rights reserved.