Musculoskeletal Translational Innovation Initiative, Carl J. Shapiro Department of Orthopaedic Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA; Mechanical Engineering Department, Boston University, Boston, USA.
Musculoskeletal Translational Innovation Initiative, Carl J. Shapiro Department of Orthopaedic Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
Clin Biomech (Bristol). 2024 Dec;120:106346. doi: 10.1016/j.clinbiomech.2024.106346. Epub 2024 Sep 13.
Stemless shoulder arthroplasty offers several advantages, such as preserving bone stock and reducing periprosthetic fracture risk. However, implant motion can deter osteointegration and increase bone resorption, where micromotion less than 0.150 mm is crucial for bony ingrowth and vital to the success of the implant. The interaction between the implant and the metaphyseal bone and its effects on stability remains unclear. Therefore, this cadaveric study aims to assess the immediate stability of two stemless prostheses in low bone density specimens.
Twenty cadaveric shoulders were used to compare the stability of two stemless shoulder implants by Zimmer-Biomet (model A) and Exactech (model B), subjected to loads of 220 N, 520 N, and 820 N to assess strain and micromotion.
Micromotion at 220 N load was 0.061 ± 0.080 mm and 0.053 ± 0.050 mm, and at 520 N load, 0.279 ± 0.37 mm and 0.311 ± 0.35 mm for models A and B, respectively. The estimated mean force required to achieve a 150 μm micromotion was 356 ± 116 N and 315 ± 61 N for models A and B, respectively. Motion analysis revealed distinct movement patterns for each implant, with model B demonstrating better force distribution on the bone despite no significance.
Forces over 520 N (high postoperative rehabilitation force) could hinder bone integration with prostheses due to excessive micromotion. Conversely, forces around 220 N (preconditioning loading force) are considered safe for prosthesis stability even with low bone density. These insights may caution against using stemless implants when bone density is low, and help guide clinical decisions on the duration of rehabilitation and sling use after stemless arthroplasty.
无柄肩关节置换术具有保留骨量和降低假体周围骨折风险等优点。然而，假体的运动可能会阻碍骨整合并增加骨吸收，其中小于 0.150 毫米的微动对于骨长入至关重要，也是假体成功的关键。假体与干骺端骨的相互作用及其对稳定性的影响尚不清楚。因此，这项尸体研究旨在评估两种无柄假体在低骨密度标本中的即刻稳定性。
使用 20 个尸体肩关节来比较 Zimmer-Biomet（模型 A）和 Exactech（模型 B）两种无柄肩关节假体的稳定性，施加 220N、520N 和 820N 的载荷以评估应变和微动。
在 220N 载荷下，模型 A 和模型 B 的微动分别为 0.061±0.080 毫米和 0.053±0.050 毫米，在 520N 载荷下，分别为 0.279±0.37 毫米和 0.311±0.35 毫米。估计达到 150 微米微动所需的平均力分别为 356±116N 和 315±61N。运动分析显示，每种假体都有独特的运动模式，尽管没有统计学意义，但模型 B 显示出更好的骨分布力。
超过 520N（高术后康复力）的力可能会因过度微动而阻碍假体与骨的整合。相反，220N 左右的力（预处理加载力）被认为对假体稳定性是安全的，即使在骨密度较低的情况下也是如此。这些见解可能会提醒人们在骨密度较低时避免使用无柄植入物，并有助于指导无柄关节置换术后康复和吊带使用时间的临床决策。
