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The extent of osteolysis can be accurately determined from his radiographs
9%
225/2556
Urine N-telopeptide levels would be expected to be decreased in this patient
2%
63/2556
TNF-alpha activity would be expected to be decreased in this patient
3%
72/2556
RANK activity would be expected to be increased in this patient
78%
1984/2556
CRP and ESR levels would be expected to be increased in this patient
7%
182/2556
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The patient's radiograph demonstrates evidence of osteolysis, which is mediated by macrophages that indirectly increase RANK activity. Osteolysis represents a histiocytic response to wear debris. Specifically, particulate debris formation leads to macrophage activation. Activated macrophages release cytokines such as TNF-alpha, which indirectly promotes osteolysis by increasing RANK (a receptor found on osteoclast-precursor cells). Indications for revision THA secondary to osteolysis include pain, with conservative treatment reserved for those who are asymptomatic. Although osteolysis may be detected on radiographs, the extent of osteolysis is often underestimated, so CT is the preferred method of imaging. Holt et al. performed a literature review on the biology of aseptic osteolysis. They reported that the most important mediators of osteolysis were TNF-alpha and IL-1. These mediators produce a pro-osteoclastogenic effect in response to implant-derived wear particles. Bitar et al. published a review focusing on the biological response to prosthetic debris. They reported that RANKL and osteoprotegerin (OPG) have been shown to play a major role in the initiation and progression of osteolytic lesions. More specifically, RANKL is an osteoblast receptor which activates osteoclasts by binding Receptor Activator of NF-κB (RANK). The RANK pathway is the chief regulator of bone turnover (osteolysis) whereas osteoprotegerin is the antagonist of this pathway, and thus the RANK/RANKL/OPG pathway is considered crucial for the occurrence of osteolysis. Figure A is a radiograph of the left hip demonstrating eccentric poly wear (this is generating the debris) and osteolysis around the cement mantle surrounding the femoral component. Incorrect Answers: Answer 1: Radiographs typically underestimate the extent of osteolysis. Answer 2: In the setting of osteolysis, urine N-telopeptide levels would be expected to be elevated as they are a marker of bone turnover. Answer 3: TNF-alpha activity would also be expected to increase. Answer 5: CRP and ESR levels would be expected to be normal in a patient with aseptic osteolysis.
4.3
(3)
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