Luo Chu-An, Hwa Su-Yang, Lin Shang-Chih, Chen Chun-Ming, Tseng Ching-Shiow
Graduate Institute of Biomedical Engineering, National Taiwan University of Science and Technology, 43 Keelung Road, Section 4, Taipei, 10607, Taiwan.
Department of Orthopedic Surgery, Tri-Service General Hospital, Taipei, Taiwan.
BMC Musculoskelet Disord. 2015 Sep 4;16:235. doi: 10.1186/s12891-015-0630-2.
High tibial osteotomy (HTO) with a medially opening wedge has been used to treat osteoarthritic knees. However, the osteotomized tibia becomes a highly unstable structure and necessitates the use of plate and screws to stabilize the medial opening and enhance bone healing. A T-shaped plate (e.g. TomoFix) with locking screws has been extensively used as a stabilizer of the HTO wedge. From the biomechanical viewpoint, however, the different plate sites and support bases of the HTO plate should affect the load-transferring path and wedge-stabilizing ability of the HTO construct. This study uses biomechanical tests and finite-element analyses to evaluate the placement- and base-induced effects of the HTO plates on construct performance.
Test-grade synthetic tibiae are chosen as the standard specimens of the static tests. A medial wedge is created for each specimen and stabilized by three plate variations: hybrid use of T- and I-shaped plates (TIP), anteriorly placed TomoFix (APT), and medially placed TomoFix (MPT). There are five tests for each variation. The failure loads of the three constructs are measured and used as the load references of the fatigue finite-element analysis. The residual life after two hundred thousand cycles is predicted for all variations.
The testing results show no occurrence of implant back-out and breakage under all variations. However, the wedge fracture consistently occurs at the opening tip for the APT and MPT and the medially resected plateau for the TIP, respectively. The testing results reveal that both failure load and wedge stiffness of the TIP are the highest, followed by the MPT, while those of the APT are the least (P < 0.05). The fatigue analyses predict comparable values of residual life for the TIP and MPT and the highest value of damage accumulation for the APT. Both experimental and numerical tests show the biomechanical disadvantage of the APT than their counterparts. However, the TIP construct without locking screws shows the highest stress at the plate-screw interfaces.
This study demonstrates the significant effect of placement site and support base on the construct behaviors. The TIP provides a wider base for supporting the HTO wedge even without the use of locking screws, thus significantly enhancing construct stiffness and suppressing wedge fracture. Compared to the APT, the MPT shows performance more comparable to that of the TIP. If a single plate and a smaller incision are considered, the MPT is recommended as the better alternative for stabilizing the medial HTO wedge.
内侧张开楔形高位胫骨截骨术（HTO）已被用于治疗膝骨关节炎。然而，截骨后的胫骨成为一个高度不稳定的结构，需要使用钢板和螺钉来稳定内侧开口并促进骨愈合。带有锁定螺钉的T形钢板（如TomoFix）已被广泛用作HTO楔形截骨的稳定器。然而，从生物力学角度来看，HTO钢板的不同放置位置和支撑基础应会影响HTO结构的载荷传递路径和楔形稳定能力。本研究采用生物力学测试和有限元分析来评估HTO钢板的放置位置和支撑基础对结构性能的影响。
选用测试级合成胫骨作为静态测试的标准标本。为每个标本制作一个内侧楔形截骨，并通过三种钢板变体进行稳定：T形和I形钢板混合使用（TIP）、TomoFix钢板前置（APT）和TomoFix钢板内侧放置（MPT）。每种变体进行五项测试。测量三种结构的失效载荷，并将其用作疲劳有限元分析的载荷参考。预测所有变体在二十万次循环后的剩余寿命。
测试结果表明，在所有变体下均未出现植入物松动和断裂。然而，APT和MPT的楔形骨折分别始终发生在开口尖端和TIP的内侧切除平台处。测试结果显示，TIP的失效载荷和楔形刚度均最高，其次是MPT，而APT的最低（P＜0.05）。疲劳分析预测TIP和MPT的剩余寿命值相当，而APT的损伤累积值最高。实验和数值测试均表明APT在生物力学方面比其他变体更具劣势。然而，未使用锁定螺钉的TIP结构在钢板 - 螺钉界面处显示出最高应力。
本研究证明了放置位置和支撑基础对结构行为有显著影响。即使不使用锁定螺钉，TIP也为支撑HTO楔形截骨提供了更宽的基础，从而显著提高结构刚度并抑制楔形骨折。与APT相比，MPT的性能与TIP更具可比性。如果考虑使用单块钢板和较小的切口，推荐MPT作为稳定内侧HTO楔形截骨的更好选择。
