Revisiting disc degeneration, “migration” & stress shielding

Through 3.5 million years of development we humans find ourselves with lordotic curves intra-uterine. Clearly someone wanted our lower backs and necks “curved” i.e. extended. Numerous published studies suggest extension is the most common directional-preference in HNP conditions and McGill and others show how extension “shuts off” the LE activity thus reducing the crushing-effect of the hyperactive/hyper-tonic posterior muscles endemic in so many with cLBP (Janda’s lower cross syndrome). Further at least 2 recently published studies (Mustafa) show HNP can be effectively treated using extension traction methods. Magnusson, Pope et al (1995)also demonstrated that prone extension postures restore height and have an “unloading” effect on discs equal to or better than flexion postures.

Both a ‘stress-shielding’ (neural arch impaction reducing posterior disc compression) and nuclear “migration” (an intact, hydrophilic nucleus that moves as an isotropic mechanism under pressure) can explain extensions benefit…. but neither is definitive in all cases. It’s not surprising however that extension appears most immediately beneficial in cases of moderate disc degeneration (the arches are already approximating).

So we try to exploit this with our decompression positions…when an extension benefit is apparent prone traction becomes a necessity…when it’s not apparent (or neural stress signs/stenosis or an “anterior disc” manifests) supine is probably the best call.