Spine
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A retrospective review. ⋯ 3.
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Medical textbooks present the pelvis and the spine as distinct entities-an unfortunate practice that does not reflect the crucial and critical role that the pelvis plays in regulating spino-pelvic alignment. Researchers are working to delineate this role. ⋯ To quantify pelvic morphology, Legaye introduced the pelvic incidence angle (PI) and espoused the theory that this angle regulates sagittal curvature of the spine. The PI is formed from 2 lines: line 1, perpendicular to the sacrum from the midline of the sacral plate, aims to quantify spatial orientation and dictate the lumbar curve; line 2, extending from the midline of the sacrum to the midpoint between femoral heads, illustrates the importance of sacral position inside the pelvis (SDC Figure 1, http://links.lww.com/BRS/B99).
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Almost 20% of joint replacement implants fail at 15 to 20 years. Reports suggest that systemic effects of metal-on-metal implants and local effects of total joint arthroplasty implants contributing to implant failure are immune system based. Sometimes implant wear debris can cause implant failure resulting from bone fracture, infection, or implant fracture/failure; most often, aseptic osteolysis or loosening leads to wear debris. ⋯ Corrosion-chemical oxidation comprising reduction reactions involving electron transport-produces electrochemical degradation. Metallic implant degradation occurs when electrochemical dissolution and mechanical/physical wear are combined (i.e., tribocorrosion). With metal-on-metal implants, even with relatively low levels of wear and particle release, pathology caused by metal debris such as pseudotumor/fibrous tissue growth can lead to early implant failure.