Baba Kazuyoshi, Mori Yu, Tanaka Hidetatsu, Kanabuchi Ryuichi, Kuriyama Yasuaki, Kurishima Hiroaki, Ito Kentaro, Kamimura Masayuki, Chiba Daisuke, Aizawa Toshimi
Department of Orthopaedic Surgery, Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan.
Med Sci (Basel). 2025 May 1;13(2):51. doi: 10.3390/medsci13020051.
Stress shielding (SS) after total hip arthroplasty (THA) leads to proximal femoral bone loss and increases the risk of complications such as implant loosening and periprosthetic fracture. While various low-stiffness stems have been developed to prevent SS, they often compromise mechanical stability. A novel femoral stem composed of Ti-33.6Nb-4Sn (TNS) alloy offers a gradually decreasing Young's modulus from proximal to distal regions, potentially improving load distribution and reducing SS. This study aimed to evaluate the mid-term clinical and radiographic outcomes of the TNS stem, with a particular focus on its effectiveness in suppressing SS.
A prospective clinical study was conducted involving 35 patients who underwent THA using the TNS stem, with a minimum follow-up of 7 years. Twenty-one patients with Ti6Al4V metaphyseal-filling stems served as controls. Clinical outcomes were assessed using Japanese Orthopaedic Association (JOA) scores, and radiographic SS was graded using Engh's classification and analyzed in Gruen zones. Inter-examiner reliability and statistical comparisons between groups were performed using appropriate tests.
The TNS group showed significantly higher preoperative JOA scores than the control group, but no significant difference in final scores. Both groups demonstrated significant improvement postoperatively. Third-degree SS occurred in the TNS group, although the overall SS grade distribution was significantly lower than in the control group ( = 0.03). SS frequency was significantly reduced in Gruen Zones 2, 3, and 6 in the TNS group.
The TNS stem demonstrated a significant reduction in SS progression compared to conventional titanium stems over a 7-year period, with comparable clinical outcomes. However, the occurrence of third-degree SS indicates that material optimization alone may be insufficient, highlighting the need for further design improvements.
全髋关节置换术（THA）后应力遮挡（SS）会导致股骨近端骨质流失，并增加植入物松动和假体周围骨折等并发症的风险。虽然已经开发出各种低刚度柄来预防SS，但它们往往会损害机械稳定性。一种由Ti-33.6Nb-4Sn（TNS）合金制成的新型股骨干，其杨氏模量从近端到远端区域逐渐降低，可能会改善载荷分布并减少SS。本研究旨在评估TNS柄的中期临床和影像学结果，特别关注其在抑制SS方面的有效性。
进行了一项前瞻性临床研究，纳入35例行TNS柄THA的患者，随访至少7年。21例使用Ti6Al4V干骺端填充柄的患者作为对照。使用日本骨科协会（JOA）评分评估临床结果，并使用Engh分类对影像学SS进行分级，并在Gruen分区进行分析。使用适当的测试进行组间的检查者间信度和统计比较。
TNS组术前JOA评分显著高于对照组，但最终评分无显著差异。两组术后均有显著改善。TNS组出现了三度SS，尽管总体SS分级分布显著低于对照组（P = 0.03）。TNS组Gruen分区2、3和6的SS发生率显著降低。
与传统钛柄相比，TNS柄在7年期间的SS进展显著降低，临床结果相当。然而，三度SS的发生表明仅材料优化可能不足，突出了进一步改进设计的必要性。
