Bishop Nicholas E, Burton Andrew, Maheson Marci, Morlock Michael M
Biomechanics Section, TUHH Hamburg University of Technology, Denickestrasse 15, Hamburg, Germany.
Clin Biomech (Bristol). 2010 Aug;25(7):666-74. doi: 10.1016/j.clinbiomech.2010.04.013. Epub 2010 Jun 9.
Short uncemented metaphyseally anchored femoral endoprostheses are becoming popular and are proposed to be less invasive than longer conventional implants. However, it is proposed here that shortening femoral endoprostheses can increase the risk of periprosthestic fracture.
A simple analytical model of a femoral hip implant was developed to estimate the risk of bone overload for varying implant size, implantation geometry, implantation force and bone quality. The load capacity of a particular short implant design in poor quality cadaveric bone specimens was also measured experimentally, to validate the model.
The model demonstrated a high risk of bone overload for a short endoprosthesis in poor quality bone. The experimental results and a clinical example of failure, to which the model was applied, supported this finding. Bone stresses increased with decreasing implant length and diameter, varus implantation, incomplete seating and high implantation forces, approaching the strength of good quality bone in extreme cases.
Correct implantation and patient selection is essential for short femoral endoprostheses.
短柄非骨水泥型经干骺端固定的股骨假体正逐渐流行，且被认为比传统的长柄植入物侵入性更小。然而，本文提出缩短股骨假体可能会增加假体周围骨折的风险。
建立了一个简单的股骨髋关节植入物分析模型，以估计不同植入物尺寸、植入几何形状、植入力和骨质情况下的骨过载风险。还通过实验测量了特定短柄植入物设计在质量较差的尸体骨标本中的承载能力，以验证该模型。
该模型表明，在质量较差的骨中使用短柄假体时骨过载风险较高。实验结果以及应用该模型的一个临床失败案例支持了这一发现。骨应力随着植入物长度和直径的减小、内翻植入、不完全就位以及高植入力而增加，在极端情况下接近优质骨的强度。
正确的植入和患者选择对于短柄股骨假体至关重要。
