Landis W J, Librizzi J J, Dunn M G, Silver F H
Department of Orthopedic Surgery, Harvard Medical School, Boston, Massachusetts, USA.
J Bone Miner Res. 1995 Jun;10(6):859-67. doi: 10.1002/jbmr.5650100606.
The vertebrate skeletal system undergoes adaptation in response to external forces, but the relation between the skeletal changes and such forces is not understood. In this context, the variation in the amount and location of calcification has been compared with changes in mechanical properties of the normally mineralizing turkey gastrocnemius tendon using ash weight measurements, X-ray radiography, and mechanical testing. Radiographic evidence from 12- to 17-week-old birds showed calcification in only portions of gastrocnemius tendons proximal to the tarsometatarsal joint. Mechanical testing of these dissected proximal regions demonstrated an increased ultimate stress and modulus and a decreased maximum strain that appeared to parallel calcification. Further, stress-strain curves of portions of uncalcified turkey gastrocnemius tendon were shaped similar to those of other typical unmineralized tendon curves while highly calcified tendons yielded curves resembling those of bone. The proximal portions of the gastrocnemius where mineralization begins were observed to have a decreased tendon cross-sectional area compared with distal portions which do not mineralize. Based on the resultant measures of mineral content and location and mechanical properties, it is hypothesized that increased calcification is a result of increased stresses at certain locations of the tendon, perhaps the consequence of the natural forces exerted by the large leg muscles of the bird into which the gastrocnemius inserts. More specifically, tendon calcification may be the result of stress-induced exposure of charged sites on the surfaces of collagen molecules, fibrils, or fibers so that deposition of mineral and subsequent mechanical reinforcement occur in the tissue.(ABSTRACT TRUNCATED AT 250 WORDS)
脊椎动物的骨骼系统会对外力做出适应性变化，但骨骼变化与这些外力之间的关系尚不清楚。在此背景下，通过灰分重量测量、X射线摄影和力学测试，将钙化量和位置的变化与正常矿化的火鸡腓肠肌腱力学性能的变化进行了比较。12至17周龄鸟类的X射线摄影证据显示，仅在跗跖关节近端的部分腓肠肌腱中有钙化。对这些解剖后的近端区域进行力学测试表明，极限应力和模量增加，最大应变减小，这似乎与钙化情况平行。此外，未钙化的火鸡腓肠肌腱部分的应力-应变曲线形状与其他典型的未矿化肌腱曲线相似，而高度钙化的肌腱产生的曲线类似于骨骼的曲线。与未矿化的远端部分相比，观察到矿化开始的腓肠肌近端部分的肌腱横截面积减小。根据所得的矿物质含量、位置和力学性能测量结果，推测钙化增加是肌腱某些位置应力增加的结果，这可能是腓肠肌插入的大腿大肌肉施加的自然力的结果。更具体地说，肌腱钙化可能是应力诱导胶原分子、原纤维或纤维表面带电位点暴露的结果，从而使矿物质沉积和随后的组织机械强化得以发生。（摘要截断于250字）
