Exponent Inc., Philadelphia, PA, USA.
Spine (Phila Pa 1976). 2010 Nov 1;35(23):E1310-6. doi: 10.1097/BRS.0b013e3181d6f84f.
Retrospective retrieval analysis.
To evaluate wear, deformation and biodegradation within retrieved polycarbonate urethane (PCU) components of Dynesys systems.
The Dynesys Dynamic Stabilization System (Zimmer Spine) consists of pedicle screws (Ti alloy), polycarbonate urethane (PCU) spacers, and a polyethylene-terephthalate cord.
Seventeen retrieved (mean implantation: 2.5 years, range: 0.7-7.0 years) and 2 exemplar implant systems were available. Reasons for revision were persistent pain (16/17), infection (1/17), and/or screw loosening (11/17), with 1/17 case of implant migration. Optical microscopy, microCT, and scanning electron microscopy were conducted to evaluate PCU spacer wear and deformation. Attenuated total reflectance Fourier transform infrared spectroscopy was used to assess spacer surface chemical composition.
Retrieved spacer components exhibited permanent bending deformation (mean: 4.3°, range: 0.0°-15.8°). We observed evidence of PCU spacer contact with pedicle screws, cords, and surrounding bony structures (74/75, 69/75, and 51/75 spacers, respectively). Relatively infrequent damage modes included PCU fracture (1/75 spacers) or cracking (2/75 spacers), as well as pedicle screw fracture (3/103 screws). PCU degradation products were identified in 10/75 spacers, which represented retrievals having significantly longer implantation times (mean: 4.3 years, range: 1.0-7.0 years). Of these spacers, 8/10 had degradation peaks identified along the side of the spacer where the material would have been in contact with bodily fluid.
PCU spacers from retrieved Dynesys systems exhibited permanent deformation, focal regions of in vivo wear and surface damage. Chemical changes associated with PCU biodegradation were associated with longer-term retrievals. The most frequently observed complication was pedicle screw loosening, with 3 incidences of screw breakage in 2 patients. These retrieval data provide a crucial basis for developing in vitro tests to simulate in vivo damage and degradation of posterior dynamic motion preservation implants. Longer-term retrievals, as well as retrievals that include more recent design features (e.g., HA coating), will be useful to provide a greater context for the clinical implications of our short-term observations.
回顾性检索分析。
评估 Dynsys 系统中聚碳酸酯聚氨酯（PCU）部件的磨损、变形和生物降解情况。
Dynsys 动态稳定系统（Zimmer 脊柱）由椎弓根螺钉（钛合金）、聚碳酸酯聚氨酯（PCU）间隔物和聚对苯二甲酸乙二醇酯绳组成。
共有 17 个（平均植入时间：2.5 年，范围：0.7-7.0 年）和 2 个典型植入系统可用于检索。翻修的原因是持续性疼痛（16/17）、感染（1/17）和/或螺钉松动（11/17），1/17 例发生了植入物迁移。采用光学显微镜、微 CT 和扫描电子显微镜观察 PCU 间隔物的磨损和变形。采用衰减全反射傅里叶变换红外光谱法评估间隔物表面化学成分。
回收的间隔物组件表现出永久性弯曲变形（平均：4.3°，范围：0.0°-15.8°）。我们观察到 PCU 间隔物与椎弓根螺钉、绳索和周围骨结构接触的证据（分别为 75 个中的 74 个、75 个中的 69 个和 75 个中的 51 个）。相对较少发生的损伤模式包括 PCU 断裂（1/75 个间隔物）或开裂（2/75 个间隔物），以及椎弓根螺钉断裂（103 个螺钉中的 3 个）。在 10/75 个间隔物中发现了 PCU 降解产物，这些间隔物的植入时间明显较长（平均：4.3 年，范围：1.0-7.0 年）。其中 8/10 个间隔物在与体液接触的一侧出现了降解峰。
从 Dynsys 系统中回收的 PCU 间隔物表现出永久性变形、体内磨损和表面损伤的局灶区域。与 PCU 生物降解相关的化学变化与长期回收有关。最常见的并发症是椎弓根螺钉松动，2 例中有 3 例螺钉断裂。这些回收数据为开发体外试验提供了重要依据，以模拟后路动态运动保护植入物的体内损伤和降解。对更长时间的回收，以及包括最近设计特点（如 HA 涂层）的回收，将有助于为我们短期观察的临床意义提供更大的背景。
