Resting Supine for 45 Minutes Yields Consistent Baseline Lumbar Intervertebral Disc Height in Asymptomatic...

Area of Science:

• Biomechanics
• Spinal Anatomy
• Medical Imaging

Background:

• Intervertebral disc (IVD) height exhibits diurnal fluctuations due to spinal loading variations.
• Accurate in vivo IVD height measurement requires accounting for prior loading history.
• Existing literature lacks consensus on the recovery time for in vivo lumbar IVD height under low loads.

Purpose of the Study:

• To determine if a 45-minute supine rest period establishes a consistent baseline for in vivo lumbar IVD height measurement.
• To assess the reliability of IVD height measurements across different times of day.

Main Methods:

• Nine healthy participants underwent magnetic resonance (MR) imaging after a 45-minute supine rest.
• Imaging sessions were conducted at two different times: morning (7:00 AM) and midday (10:30 AM-12:30 PM).
• Lumbar IVD heights (L1-L2 to L5-S1) were manually segmented and measured; segmentation repeatability was also assessed.

Main Results:

• High reliability was observed for IVD height measurements across different times of day (ICC: 0.96) and for segmentation repeatability (ICC: 0.97).
• Root mean squared errors (RMSE) were minimal (0.08 mm), representing less than 1% of total IVD height.

Conclusions:

• A 45-minute supine rest period is sufficient to establish a consistent and reliable baseline for measuring in vivo lumbar IVD height.
• These findings support the use of this protocol for accurate IVD mechanics research between 7:00 AM and 12:30 PM.