Lapner Michael, Willing Ryan, Johnson James A, King Graham J W
Division of Orthopedic Surgery, Sturgeon Hospital, University of Alberta, 201 Boudreau Rd, St. Albert, Alberta T8N 6C4, Canada.
Mechanical Engineering Department, Thomas J. Watson School of Engineering & Applied Science, Binghamton University - SUNY, P.O. Box 6000, Binghamton, NY 13902-6000, USA.
Clin Biomech (Bristol). 2014 May;29(5):537-44. doi: 10.1016/j.clinbiomech.2014.03.010. Epub 2014 Apr 2.
Hemiarthroplasty is a treatment option for selected distal humerus fractures. The purpose of this study was to determine the effect of distal humeral hemiarthroplasty and implant size on elbow articular contact. We hypothesized that implants of varying sizes produce different contact patterns compared with the native elbow.
Eight cadaveric arms were tested in an elbow simulator and the kinematics recorded. Three-dimensional reconstructions of bones and cartilage were generated from computed-tomography images to determine contact patterns. The native articulation was compared to optimal, oversized, and undersized implants (Latitude Anatomic Hemiarthroplasty). Changes in contact patterns relative to the native articulation were measured using total contact area and contact patch agreement scores, defined as the sum of distance between contact patches×area, indicating how well contact patches agree with the native contact pattern.
The native articulation had significantly lower ulnohumeral contact patch agreement scores compared to all tested implants (P<0.05). Mean ulnohumeral and radiocapitellar contact area decreased an average 44% (P=0.03) and 4% (P=0.07) following placement of an optimally sized implant. There was no effect of implant size on contact area or contact patch agreement score (P>0.05).
Shape differences of elbow implants relative to the native joint may be responsible for altered contact patterns and could be improved with design modifications. These changes may predispose the elbow to arthritis. The lack of influence of implant size suggests that implant shape and materials may be more important than implant sizing during surgery.
半关节成形术是特定肱骨远端骨折的一种治疗选择。本研究的目的是确定肱骨远端半关节成形术及植入物尺寸对肘关节面接触的影响。我们假设与天然肘关节相比，不同尺寸的植入物会产生不同的接触模式。
在肘关节模拟器中对8具尸体手臂进行测试并记录运动学数据。通过计算机断层扫描图像生成骨骼和软骨的三维重建，以确定接触模式。将天然关节与最佳尺寸、过大尺寸和过小尺寸的植入物（Latitude解剖型半关节成形术）进行比较。使用总接触面积和接触斑一致性评分来测量相对于天然关节的接触模式变化，接触斑一致性评分定义为接触斑之间距离×面积的总和，表明接触斑与天然接触模式的吻合程度。
与所有测试的植入物相比，天然关节的尺肱接触斑一致性评分显著更低（P<0.05）。放置最佳尺寸的植入物后，平均尺肱接触面积和桡骨头小头接触面积分别平均减少了44%（P=0.03）和4%（P=0.07）。植入物尺寸对接触面积或接触斑一致性评分没有影响（P>0.05）。
肘关节植入物相对于天然关节的形状差异可能导致接触模式改变，通过设计改进可能会得到改善。这些变化可能使肘关节易患关节炎。植入物尺寸缺乏影响表明，手术过程中植入物的形状和材料可能比尺寸更重要。
