Department of Orthopaedic Surgery, The Medical College of Wisconsin Inc., 8701 W. Watertown Plank Road, Box 26509, Milwaukee, WI, 53226-0509, USA.
Orthopaedic & Rehabilitation Engineering Center and Graduate Program in Dental Biomaterials, Marquette University, Milwaukee, WI, USA.
Eur Spine J. 2022 Sep;31(9):2301-2310. doi: 10.1007/s00586-022-07271-2. Epub 2022 Jun 13.
The SHILLA™ Growth Guidance system is a stainless-steel rod and screw system used for Early Onset Scoliosis which incorporates a unique flanged set screw designed to capture the rod, while allowing it to slide as the patient grows. Concomitant with this design is the potential for generation of wear debris and for an inflammatory host response. We hypothesized that the magnitude of the host response adjacent to the unlocked screws and rods would be greater than the host response to the locked rod/screws.
Seven tissue samples adjacent to locked (3) and unlocked screws (4) from three SHILLA patients (mean implantation time of 19 post-operative months) with infantile idiopathic scoliosis were obtained as part of an explant analysis protocol during a PMDA-approved clinical trial in Japan. Gross appearance, high-resolution radiographs, and histology were assessed. ISO Standard 10993 Part 6 was used to assess the host response.
All three locked screw had no metallosis. In contrast, metallosis for unlocked screw tissue samples were rated as "ubiquitous" (2/4), "focal" (1/4), or "absent" (1/4). Microscopic metallic debris was found intracellularly and within interstices of fibrous connective tissues more frequently adjacent to unlocked screws compared to locked screws. Cell type and population scoring consistently showed a modestly larger inflammatory response (macrophages) in the unlocked tissue samples.
The peri-prosthetic tissue response to the unlocked rods/screws had a higher reactivity grade (slight reaction, Δ = 4.0) per ISO 10993 Part 6 compared to the locked screws in three patients with the SHILLA™ Growth Guidance scoliosis system.
SHILLA™ 生长引导系统是一种用于早发性脊柱侧凸的不锈钢棒和螺钉系统，它包含一个独特的带法兰的固定螺钉，旨在固定棒，同时允许其随患者生长而滑动。与这种设计相伴的是产生磨损碎片和炎症宿主反应的潜力。我们假设未锁定螺钉和棒附近宿主反应的幅度将大于对锁定杆/螺钉的宿主反应。
从三名患有婴儿特发性脊柱侧凸的 SHILLA 患者（平均术后 19 个月）的三个锁定（3 个）和未锁定螺钉（4 个）中获得了七个相邻组织样本，这是日本 PMDA 批准的临床试验中进行的一项剖析分析协议的一部分。评估了大体外观、高分辨率射线照相和组织学。使用 ISO 10993 第 6 部分评估宿主反应。
所有三个锁定螺钉均无金属病。相比之下，未锁定螺钉组织样本的金属病被评为“普遍”（2/4）、“局灶”（1/4）或“无”（1/4）。与锁定螺钉相比，未锁定螺钉周围的纤维结缔组织间隙中更频繁地发现细胞内和细胞间隙内的微观金属碎片。细胞类型和群体评分一致显示，未锁定组织样本的炎症反应（巨噬细胞）略大。
根据 ISO 10993 第 6 部分，与三个患有 SHILLA™ 生长引导脊柱侧凸系统的患者的锁定螺钉相比，未锁定杆/螺钉的周围假体组织反应的反应性等级（轻微反应，Δ=4.0）更高。
