Messer-Hannemann Philipp, Bätz Johanna, Lampe Frank, Klein Anke, Püschel Klaus, Campbell Graeme M, Morlock Michael
TUHH, Hamburg University of Technology, Institute of Biomechanics, Denickestrasse 15, 21073 Hamburg, Germany.
TUHH, Hamburg University of Technology, Institute of Biomechanics, Denickestrasse 15, 21073 Hamburg, Germany.
Clin Biomech (Bristol). 2019 Mar;63:185-192. doi: 10.1016/j.clinbiomech.2019.03.006. Epub 2019 Mar 20.
Reaming of the acetabular cavity and cup implantation directly influence the hip rotation center and contact area between implant and bone. Previous studies have reported on an altered rotation center after total hip arthroplasty, but have not studied the influence of reaming and cup implantation separately. Aim of this study was therefore to analyze the individual influence of acetabular reaming and subsequent cup implantation on the rotation center and how this influences the contact conditions at the bone-implant interface.
Acetabular press-fit cups were implanted into the left and right hips of three full cadavers (n = 6). CT scans were performed to calculate the change in hip rotation center after reaming and prior to liner insertion. 3D models of the cups were used to determine the polar gap, the contact conditions and the effective press-fit.
Reaming the acetabular cavity shifted the rotation center medially (median 5.8 mm, range 4.8-9.1), superiorly (5.3 mm, 3.0-7.0) and posteriorly (2.9 mm, 1.0-5.3). With cup implantation, the rotation center shifted back towards the native position, but no full restoration was observed. The degree of shift increased with the size of polar gap (r = 0.829, P = .042), which inversely reduced the contact area (r = 0.886, P = .019).
This study reveals that the dominant factor in hip rotation center restoration is the reaming process, while the cup implantation for a given nominal press-fit has only a small influence. Increasing the press-fit would improve the restoration but bares the danger of insufficient bone coverage and periprosthetic fractures due to the high forces needed.
髋臼腔扩髓及髋臼杯植入直接影响髋关节旋转中心以及植入物与骨之间的接触面积。既往研究报道了全髋关节置换术后旋转中心的改变，但未分别研究扩髓和髋臼杯植入的影响。因此，本研究的目的是分析髋臼扩髓及随后的髋臼杯植入对旋转中心的个体影响，以及这如何影响骨-植入物界面的接触情况。
将髋臼压配式髋臼杯植入三具完整尸体（n = 6）的左右髋关节。进行CT扫描以计算扩髓后及内衬插入前髋关节旋转中心的变化。使用髋臼杯的三维模型确定极距、接触情况和有效压配。
髋臼腔扩髓使旋转中心向内侧（中位数5.8毫米，范围4.8 - 9.1）、上方（5.3毫米，3.0 - 7.0）和后方（2.9毫米，1.0 - 5.3）移位。植入髋臼杯后，旋转中心向原始位置回移，但未观察到完全恢复。移位程度随极距大小增加（r = 0.829，P = 0.042），这反过来减少了接触面积（r = 0.886，P = .019）。
本研究表明，髋关节旋转中心恢复的主要因素是扩髓过程，而对于给定标称压配的髋臼杯植入影响较小。增加压配会改善恢复，但由于所需的高压力，存在骨覆盖不足和假体周围骨折的风险。
