A protrusion is distinguished from a disc bulge in that it involves less than 25% of the circumference of the disc. Conversely it is distinguished from a disc extrusion in that its base is wider than its 'dome' and it does not extend above or below the disc level.
It may also be described in terms of its axial position, into central, subarticular, foraminal, extraforaminal or anterior locations.
Additionally the terms contained (outer annulus fibrosus laminae are intact) and non-contained (all laminae are deficient) are also sometimes used.
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