Mineral content and strength of lumbar vertebrae. A cadaver study

Fifty-two cadaveric spine-motion segments were tested in compression alone and in combined compression-flexion to determine whether the compressive strength of lumbar vertebrae varied with the direction of the applied load, that is, whether similar relationships existed between the compressive strength and the amount of bone mineral depending on the direction of the loading. The bone mineral content (BMC) ranged between 1.6 and 5.8 g/cm and the ultimate strength between 810 and 10,090 N. The BMC of the motion segments was correlated with their strength irrespective of degree of flexion during testing (0-15 degrees). For compression-flexion within physiologic limits, the first part of the motion segment to fail was, with few exceptions, the end plate and the adjacent spongy bone.