Plausinis D, Greaves C, Regan W D, Oxland T R
Department of Orthopaedics, University of British Columbia, 910 West 10th Ave., Vancouver, BC, Canada V5Z 4E3.
Clin Biomech (Bristol). 2005 Dec;20(10):1055-63. doi: 10.1016/j.clinbiomech.2005.06.012. Epub 2005 Aug 10.
Ipsilateral shoulder and elbow replacements may leave only a short segment of bone bridging the two implants in the humerus. The potential for high stress concentrations as a result of this geometry has been a concern with regard to periprosthetic fracture, especially with osteoporotic bone. The study aims to determine the optimum length of the bone-bridge between shoulder and elbow humeral implants, and to assess the effect of filling the canal with cement.
A three-dimensional finite element model was used to compare the stresses between a humerus with a solitary prosthesis and a humerus with both proximal and distal cemented prostheses. The length of the bone-bridge and the effect of filling the canal with cement were studied under bending and torsion.
Gradual load transfer from prosthesis to bone was observed for all cases, and no stress concentration was evident. The length of the bone-bridge had no deleterious effect on stresses in the humerus, and filling the canal with cement did not appreciably decrease the loads carried by the humerus.
The length of the bone-bridge between stem tips has little effect on the resultant stresses in the humerus. Filling the canal with cement adds little benefit to the structural integrity of the humerus. Ipsilateral shoulder and elbow prostheses may be considered independent of one another in terms of risk of periprosthetic fracture.
同侧肩关节和肘关节置换术后，肱骨中连接两个植入物的骨段可能很短。这种几何形状导致的高应力集中可能性一直是假体周围骨折的一个关注点，尤其是在骨质疏松性骨中。本研究旨在确定肩关节和肘关节肱骨植入物之间骨桥的最佳长度，并评估用骨水泥填充髓腔的效果。
使用三维有限元模型比较单假体肱骨与近端和远端骨水泥固定假体肱骨之间的应力。在弯曲和扭转情况下研究骨桥长度以及用骨水泥填充髓腔的效果。
所有病例均观察到从假体到骨的逐渐载荷传递，且无明显应力集中。骨桥长度对肱骨应力无有害影响，用骨水泥填充髓腔并未显著降低肱骨所承受的载荷。
柄端之间骨桥的长度对肱骨中的合成应力影响很小。用骨水泥填充髓腔对肱骨的结构完整性益处不大。就假体周围骨折风险而言，同侧肩关节和肘关节假体可被视为相互独立。
