Singhealth-Duke NUS Musculoskeletal Sciences Academic Clinical Program, Singapore General Hospital, Singapore, Singapore.
Department of Orthopedic Surgery, Singapore General Hospital, Singapore, Singapore.
J Orthop Res. 2023 Jun;41(6):1139-1147. doi: 10.1002/jor.25456. Epub 2022 Oct 19.
The proximal humerus is the most common site of occurrence of primary bone tumors in the upper limb. Endoprosthetic replacement is deemed as the preferred reconstructive option following primary resection of bone tumors. However, it has been also associated with complications such as stress shielding and aseptic loosening compromising prosthetic survival. Our objective was to conduct a finite element (FE) study to investigate the effect of varying endoprosthesis length on bone stresses as well as to quantify the extent of stress shielding across the bone length (BL) in a humerus-prosthesis assembly for proximal humeral replacement after tumor excision thereby allowing us to identify the optimal implant length with best biomechanical performance. FE models of the intact humerus and humerus-prosthesis assemblies were established where they were loaded at the elbow joint under torsion with the glenohumeral joint fixed to represent twisting. After dividing the bone into individual slices consisting of 5% BL, the maximum cortical and cancellous principal, von Mises and shear bone stresses were calculated. To measure the level of stress shielding, the percentage stress change from the intact state was evaluated across each slice. Similar stress patterns were observed between the intact state and shorter endoprosthesis compared to the longer endoprostheses. Our findings illustrated the possibility of stress shielding occurring under torsional forces with its effect increasing with implant lengthening. To conclude, we believe that using a shorter prosthesis may substantially diminish the risk of potential implant failure due to stress shielding.
肱骨近端是上肢原发性骨肿瘤最常见的发生部位。在原发性骨肿瘤切除后，假体置换被认为是首选的重建方法。然而，它也与并发症有关，如应力屏蔽和无菌性松动，从而影响假体的存活率。我们的目的是进行有限元（FE）研究，以调查不同假体长度对骨应力的影响，并量化肱骨假体切除后肱骨-假体组件中骨长度（BL）上的应力屏蔽程度，从而确定具有最佳生物力学性能的最佳植入物长度。我们建立了完整肱骨和肱骨-假体组件的 FE 模型，在这些模型中，通过将盂肱关节固定以代表扭转来在肘关节处加载并进行扭转加载。在将骨分成由 5%BL 组成的单个切片后，计算最大皮质和松质主应力、von Mises 应力和剪切骨应力。为了测量应力屏蔽的程度，评估了每个切片中从完整状态的应力变化百分比。与较长的假体相比，在较短的假体和完整状态下观察到相似的应力模式。我们的发现表明，在扭转力下可能会发生应力屏蔽，并且随着植入物的延长，其影响会增加。总之，我们认为使用较短的假体可能会大大降低由于应力屏蔽而导致潜在植入物失效的风险。
