PUPU

作者：Emma Hitt, PhD  
出處：WebMD醫學新聞

　　May 13, 2010 — 根據新研究，測量骨質密度可能低估了皮質骨多孔性（porosity）。
　　
　　來自澳洲墨爾本大學醫學與內分泌學部門的Roger M. D. Zebaze醫師與其同事們，在5月15日的Lancet期刊上報告他們的發現。
　　
　　根據研究者表示，骨小樑比皮質骨流失地更快。他們寫到，骨小樑骨流失以及脊椎骨的骨折已經主導了思考與研究方向至骨脆度的結構基礎將近70年。他們附帶表示，皮質位置的非脊椎骨折佔了所有骨折的80%，以及老年病患大部分骨折相關發病與死亡率。
　　
　　為了定量與比較皮質骨與骨小樑骨質流失程度，研究團隊使用高解析度週邊斷層掃描來測量122位白人女性死亡後的遠端尺骨。他們也以掃描式電子顯微鏡測量多孔性。
　　
　　這些女性介於50~80歲，68%遠端尺骨位置有羥基磷灰石的骨質流失，而32%位於骨小樑。除此之外，16%的整體骨質流失發生在50~64歲之間，而84%發生在65歲以後。骨髓附近的皮質重塑佔了骨質流失的47%。
　　
　　年齡在50~64歲與80歲以上，皮質骨密度降低了15%（P<0.0001），但是當納入皮質多孔性骨小樑轉化後，估計降低了43%。同樣的，在排除皮質殘餘前，骨小樑密度下降了14%，但是在排除皮質殘餘後，下降了52%（P<0.0001），代表皮質殘餘可能被錯認為骨小樑骨質流失。
　　
　　在一篇相關的主編評論中，印第安納波里斯印第安納大學醫學院細胞生物與解剖學部門的David B Burr博士指出，這些發現，大部分骨折發生在65歲以上，且可能與更多的皮質骨流失，而非骨小樑流失有關，對於確認以及治療骨質疏鬆都有很重要的應用。
　　
　　根據Burr博士表示，來自於這項研究，對治療的一個建議是，應該使用針對皮質骨的藥物來治療與年齡相關的骨質流失。
　　
　　這項研究由澳洲國家健康與醫學研究局贊助。試驗作者們表示沒有相關資金上的往來。Burr博士接受經費贊助，以及/或是擔任禮來、Amgen、Procter與Gamble藥廠的顧問、發言人、以及/或是顧問團成員。


Evaluation of Cortical Bone May More Accurately Identify Fracture Risk

By Emma Hitt, PhD
Medscape Medical News

May 13, 2010 — Standard methods for measuring bone mineral density may underestimate cortical bone porosity, according to new research.

Roger M. D. Zebaze, MD, from the departments of Medicine and Endocrinology at the University of Melbourne, Australia, and colleagues reported their findings in the May 15 issue of The Lancet.

According to the researchers, trabecular bone is lost more rapidly than cortical bone. "For this reason, trabecular bone loss and fractures of the vertebral body...have dominated thinking and research into the structural basis of bone fragility for almost 70 years," they write. They add that "non-vertebral fractures at predominantly cortical sites account for 80% of all fractures and most fracture-related morbidity and mortality in old age."

To quantify and compare cortical and trabecular bone loss, the researchers used high-resolution peripheral computed tomography to measure, postmortem, the distal radius of 122 white women. They also measured porosity using scanning electron microscopy. The researchers used a series of calculations to estimate loss in total, cortical, and trabecular bone mass across age groups.

From age 50 to 80 years, 68% of the hydroxyapatite of bone lost at the distal radius was cortical and 32% was trabecular. In addition, 16% of total bone loss occurred between ages 50 and 64 years, whereas 84% occurred after age 65 years. Remodeling within the cortex adjacent to the marrow accounted for 47% of bone loss.

Between ages 50 to 64 years and 80 years and older, cortical density decreased by 15% (P < .0001), but when porosity trabecularizing to the cortex was included, the decrease was estimated at 43%. Likewise, trabecular density decreased by 14% (P = .06) before cortical remnants were excluded, but by 52% (P < .0001) after cortical remnants were excluded, suggesting that cortical remnants may be mistakenly regarded as trabecular bone loss.

In a related editorial, David B Burr, PhD, from Department of Anatomy and Cell Biology, Indiana University School of Medicine, in Indianapolis, points out that these findings, "that most fractures occur after age 65 years and are attributable to greater loss of cortical than of trabecular bone — have important implications for both identification and treatment of osteoporosis."

According to Dr. Burr, one recommendation for treatment that stems from this work is that drugs targeting cortical bone should be used to treat age-related bone loss late in life.

The study was supported by the Australia National Health and Medical Research Council. The study authors have disclosed no relevant financial relationships. Dr. Burr has received grant support and/or served as a consultant, speaker, and/or advisor board member from Eli Lilly and Company, Amgen, and Procter and Gamble Pharmaceuticals.

Lancet. 2010;375:1729-1736.