Intradiscal pressure in vivo

Wilke HJ et al Clinical biomech 16; 2001.

Intradiscal pressure measurements were taken in a variety of postures and activities many replicating the earlier work of Nachemson. Prone-lying: 0.1 Mpa, Side-lying: 0.12, relaxed-standing: 0.5, flexed-standing: 1.1, flexion-sitting: 0.83. Lifting 40lbs with a rounded back: 2.3, with flexed knees: 1.7, with weight close to the body: 1.1. Interestingly pressure during the night increased from 0.1 to 0.24, a near two and a half increase which helps explain the pain & stiffness in many in the AM as well as the severe pain noted by those with active annular tears. While exercising pressure curves were similar; 0.43-0.50. The greatest change in pressure was with flexion, changing nearly linearly with flexion angle: 1.08 at 36 degrees. Extension there was a linear increase but the highest pressure only reached 0.6 at a 20 degree angle. Again a pressure-mitigation with extension is observed which further reinforces the value of positional-prone-extension during traction. Lateral bending showed symmetrical behavior, with an increase up to .60 at an angle approx. 20 degrees. Beyond those ranges pressure decreased to .38 by 30 degrees. The assumption is that muscular contraction accounts for the pressure increase in the initial bending however at a certain angle gravity creates muscular release as the passive system takes over.

Studies like this one can help us greatly in ADL and exercise prescription.