Sakkers R J, Valkema R, de Wijn J R, Lentjes E G, van Blitterswijk C A, Rozing P M
Department of Orthopaedic Surgery, University Hospital Leiden, The Netherlands.
Clin Orthop Relat Res. 1995 Feb(311):183-9.
A new range of clinically used, biodegradable, bone-bonding copolymers has hydrogel properties. With intramedullary press fit, these polymers generate considerable pressure through swelling caused by water absorption. In total hip arthroplasty, high intramedullary pressures can be attained by insertion of the prosthesis into femora by using methylmethacrylate cement and a cement plug. Because the effects of such intramedullary pressures are not fully known, 10-cm-long segments of the proximal diaphysis of fresh femoral bones from 22 human cadavers were tested for their intramedullary pressure resistance. The intramedullary pressure resistance, calculated burst forces, and stress on the bone were correlated to age, gender, bone mineral content per unit length, and bone mineral density. In most bone segments, a burst fracture occurred just opposite the linea aspera. The hydraulic bursting pressures ranged from 2.3 to 13.4 MPa (age adjusted gender effect [male-female], 2.2 MPa [p = 0.05]). The forces at fracture were calculated to be between 265 and 1361 N (regression coefficient: 247/unit bone mineral content per unit length). The tangential stress appeared to be between 7.54 and 27.54 MPa (regression coefficient: 11.6/unit bone mineral density; bone mineral density adjusted gender difference [male-female], 4.5 MPa [p < 0.05]). Biochemical examination of the bones did not show any abnormalities. The results of this study show that the human femora can resist mechanically an intramedullary pressure of at least 2 MPa. From a mechanical point of view, intramedullary pressures generated by swelling polymers should remain below 2 MPa for safe use.
一系列临床上使用的新型可生物降解骨结合共聚物具有水凝胶特性。通过髓内压配，这些聚合物因吸水膨胀而产生相当大的压力。在全髋关节置换术中，使用甲基丙烯酸甲酯骨水泥和骨水泥塞将假体插入股骨时可获得较高的髓内压力。由于这种髓内压力的影响尚不完全清楚，对22具人类尸体新鲜股骨近端骨干10厘米长的节段进行了髓内压力耐受性测试。髓内压力耐受性、计算得出的破裂力和骨上的应力与年龄、性别、单位长度骨矿物质含量和骨矿物质密度相关。在大多数骨节段中，爆裂骨折恰好发生在粗线相对处。液压爆裂压力范围为2.3至13.4兆帕（年龄调整后的性别效应[男性-女性]，2.2兆帕[p = 0.05]）。计算得出骨折时的力在265至1361牛之间（回归系数：每单位长度骨矿物质含量247）。切向应力似乎在7.54至27.54兆帕之间（回归系数：每单位骨矿物质密度11.6；骨矿物质密度调整后的性别差异[男性-女性]，4.5兆帕[p < 0.05]）。对骨骼的生化检查未显示任何异常。本研究结果表明，人类股骨在机械上能够抵抗至少2兆帕的髓内压力。从力学角度来看，为安全使用，由膨胀聚合物产生的髓内压力应保持在2兆帕以下。
