Abhari Roxanna E, Willing Ryan, King Graham J W, Johnson James A
Bioengineering Research Laboratory, Roth McFarlane Hand and Upper Limb Center, St. Joseph's Health Care, University of Western Ontario, London, Ontario, Canada.
Bioengineering Research Laboratory, Roth McFarlane Hand and Upper Limb Center, St. Joseph's Health Care, University of Western Ontario, London, Ontario, Canada; Department of Mechanical Engineering, Binghamton University, Binghamton, NY.
J Hand Surg Am. 2017 Aug;42(8):602-609. doi: 10.1016/j.jhsa.2017.03.034. Epub 2017 Apr 25.
To investigate the effect of implant positioning on ulnohumeral contact using patient-specific distal humeral (DH) implants.
Seven reverse-engineered DH implants were manufactured based on computed tomography scans of their osseous geometry. Native ulnae were paired with corresponding native humeri and custom DH implants in a loading apparatus. The ulna was set at 90° of flexion and the humeral component (either native bone or reverse-engineered implant) was positioned from 5° varus to 5° valgus in 2.5° increments under a 100-N compressive load. Contact with the ulna was measured with both the native distal humerus and the reverse-engineered DH implant at all varus-valgus (VV) angles, using a joint casting method. Contact patches were digitized and analyzed in 4 ulnar quadrants. Output variables were contact area and contact pattern.
Mean contact area of the native articulation was significantly greater than with the distal humeral hemiarthroplasty (DHH) implants across all VV positions. Within the native condition, contact area did not significantly change owing to VV angulation. Within the DHH condition, contact area also did not significantly change owing to VV angulation. Conversely, in the DHH condition, contact pattern did significantly change. Medial ulnar contact pattern was significantly affected by VV angulation. Lateral ulnar contact was variably affected, but generally decreased as well.
Ulnar contact patterns were changed as a result of VV implant positioning using reverse-engineered DH implants, most notably on the medial aspect of the joint. Implant positioning plays a crucial role in producing contact patterns more like those observed in the native joint.
Recent clinical evidence reports nonsymmetrical ulnar wear after DHH. This work suggests that implant positioning is likely a contributing factor and that more exact implant positioning may lead to better clinical outcomes.
使用定制的肱骨远端（DH）植入物，研究植入物位置对尺肱关节接触的影响。
基于对骨几何结构的计算机断层扫描，制造了七个逆向工程的DH植入物。将天然尺骨与相应的天然肱骨以及定制的DH植入物配对，置于加载装置中。尺骨设置为屈曲90°，在100 N压缩载荷下，肱骨组件（天然骨或逆向工程植入物）以2.5°的增量从5°内翻位调整到5°外翻位。使用关节铸型法，在所有内翻-外翻（VV）角度下，测量天然肱骨远端和逆向工程的DH植入物与尺骨的接触情况。在四个尺骨象限对接触斑进行数字化处理并分析。输出变量为接触面积和接触模式。
在所有VV位置，天然关节的平均接触面积显著大于肱骨半关节置换术（DHH）植入物的接触面积。在天然状态下，接触面积不会因VV角度变化而显著改变。在DHH状态下，接触面积也不会因VV角度变化而显著改变。相反，在DHH状态下，接触模式有显著变化。尺骨内侧的接触模式受VV角度的显著影响。尺骨外侧的接触受到不同程度的影响，但通常也会减少。
使用逆向工程的DH植入物时，VV植入物位置的改变会导致尺骨接触模式发生变化，最明显的是在关节内侧。植入物位置在产生更类似于天然关节观察到的接触模式方面起着关键作用。
最近的临床证据报告了DHH后尺骨不对称磨损的情况。这项研究表明，植入物位置可能是一个促成因素，更精确的植入物位置可能会带来更好的临床结果。
