1、SURGICAL TREATMENT OF SPINE OSTEOPOROSISConcept of Osteoporosis A systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility and a susceptibility to fracture.“ the above definition developedin Hong Kong i
2、n 1993 Pathophysiology of OPBone Remodeling Imbalance of bone remodeling, In pathologic situations, bone mass may be sacrificed to satisfy the bodys intra- and extracellular calcium needs. A specific quantity of bone is resorbed from the remodeling site and then a reversal occurs and the cavity is o
3、ccupied by osteoblasts which refill that cavity with boneThe Progression of Bone RemodelingMechanisms of Bone LossAn increased number of bone remodeling units can be activated which, when combined with either of the above two processes, may result in increased bone loss. bone loss is equal to bone f
4、ormation and the amount of bone tissue present represents normal bone mass increased number of remodeling sites increased porosity of the bone, ie the remodeling space, and this gives decreased bone mas Bone Loss: Cancellous vs. Cortical BoneAlthough cancellous bone may account for less than 25% of
5、the total bone mass in healthy adults, its surface area far exceeds thatof cortical bone. Bone Loss: Cancellous vs. Cortical BoneCancellous bone is more metabolically active than cortical bone. If bone remodeling becomes uncoupled, with osteoclastic activity exceeding osteoblastic activity, the mass
6、 and structural integrity of cancellous bone is more severely affected than cortical bone. Bone Loss: Cancellous vs. Cortical BoneDuring the accelerated period of bone loss occurring immediately post-menopause, cancellous bone loss is increased 3-fold, while rates of cortical bone loss are slower. Therefore, fractures related to osteoporosis most commonly occur in areas rich in cancellous bone (ie, the vertebrae and wrist), and BMD measurements have focused on these critical anatomic siteshigh turnover with either increased formation or increased resorption or both
