Zhang Min, Junaid Sarah, Gregory Thomas, Hansen Ulrich, Cheng Cheng-Kung
Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100083, China; Key Laboratory of Biomechanics and Mechanobiology (Beihang University), Ministry of Education, China; Mechanical Engineering Department, Imperial College London, UK.
Mechanical Engineering Department, Imperial College London, UK; Engineering and Applied Sciences, Aston University, Birmingham, UK.
Clin Biomech (Bristol). 2019 Feb;62:15-22. doi: 10.1016/j.clinbiomech.2018.12.021. Epub 2018 Dec 29.
The glenoid component in reverse total shoulder arthroplasty is recommended to be positioned inferiorly or with a downward tilt with the intention of reducing scapular notching. However, it is still unclear whether modifying the position of the glenoid prosthesis affects implant stability. The aim of this study was to determine the association between implant positioning and glenoid prosthesis fixation using Grammont reverse total shoulder arthroplasty.
Four positions for the glenoid prosthesis were studied using the finite element method. The glenosphere was positioned as follows: 1) in the middle of the glenoid fossa, 2) flush with the inferior glenoid rim, 3) with an inferior overhang, 4) with a 15° inferior inclination. Bone-prosthesis micromotions and strain-induced bone adaptations were quantified during five daily activities.
When the glenoid component was tilted inferiorly, the activities producing anterior-posterior shear forces (e.g. standing up from an armchair) caused an increase in peak micromotions. In the lateral-middle glenoid, inferior positioning caused a 64.6% reduction in bone apparent density. In the lateral-inferior glenoid, central positioning led to the most severe bone resorption, reaching 43.9%.
Reducing activities which generate anterior-posterior shear forces on the shoulder joint will increase bone formation and may improve the primary stability of the implant when fixed in the position with an inferior tilt. Postoperative bone resorption is highly dependent on implant positioning. Understanding the relationship between bone resorption and implant positioning will help surgeons improve the long-term stability of reverse total shoulder arthroplasty.
在反式全肩关节置换术中，推荐将关节盂组件置于下方或向下倾斜，目的是减少肩胛切迹。然而，改变关节盂假体的位置是否会影响植入物稳定性仍不清楚。本研究的目的是使用Grammont反式全肩关节置换术确定植入物位置与关节盂假体固定之间的关联。
使用有限元方法研究关节盂假体的四个位置。关节球的位置如下：1）位于关节盂窝中部，2）与关节盂下缘齐平，3）有向下悬垂，4）有15°向下倾斜。在五项日常活动中对骨-假体微动和应变诱导的骨适应性进行量化。
当关节盂组件向下倾斜时，产生前后剪切力的活动（如从扶手椅上站起来）会导致峰值微动增加。在关节盂外侧中部，向下定位导致骨表观密度降低64.6%。在关节盂外侧下部，中央定位导致最严重的骨吸收，达到43.9%。
减少在肩关节上产生前后剪切力的活动将增加骨形成，并可能在以向下倾斜的位置固定时提高植入物的初始稳定性。术后骨吸收高度依赖于植入物位置。了解骨吸收与植入物位置之间的关系将有助于外科医生提高反式全肩关节置换术的长期稳定性。
