Goldhahn J, Neuhoff D, Schaeren S, Steiner B, Linke B, Aebi M, Schneider E
AO Research Institute Davos, Davos, Switzerland.
Arch Orthop Trauma Surg. 2006 Oct;126(8):554-61. doi: 10.1007/s00402-006-0185-7. Epub 2006 Jul 25.
Osteoporosis is not only responsible for an increased number of metaphyseal and spinal fractures but it also complicates their treatment. To prevent the initial loosening, we developed a new implant with an enlarged implant/bone interface based on the concept of perforated, hollow cylinders. We evaluated whether osseointegration of a hollow cylinder based implant takes place in normal or osteoporotic bone of sheep under functional loading conditions during anterior stabilization of the lumbar spine.
Osseointegration of the cylinders and status of the fused segments (ventral corpectomy, replacement with iliac strut, and fixation with testing implant) were investigated in six osteoporotic (age 6.9 +/- 0.8 years, mean body weight 61.1 +/- 5.2 kg) and seven control sheep (age 6.1 +/- 0.2 years, mean body weight 64.9 +/- 5.7 kg). Osteoporosis was introduced using a combination protocol of ovariectomy, high-dose prednisone, calcium and phosphor reduced diet and movement restriction. Osseointegration was quantified using fluorescence and conventional histology; fusion status was determined using biomechanical testing of the stabilized segment in a six-degree-of-freedom loading device as well as with radiological and histological staging.
Intact bone trabeculae were found in 70% of all perforations without differences between the two groups (P = 0.26). Inside the cylinders, bone volume/total volume was significantly higher than in the control vertebra (50 +/- 16 vs. 28 +/- 13%) of the same animal (P<0.01), but significantly less (P<0.01) than in the near surrounding (60 +/- 21%). After biomechanical testing as described in Sect. "Materials and methods", seven spines (three healthy and four osteoporotic) were classified as completely fused and six (four healthy and two osteoporotic) as not fused after a 4-month observation time. All endplates were bridged with intact trabeculae in the histological slices.
The high number of perforations, filled with intact trabeculae, indicates an adequate fixation; bridging trabeculae between adjacent endplates and tricortical iliac struts in all vertebrae indicates that the anchorage is adequate to promote fusion in this animal model, even in the osteoporotic sheep.
骨质疏松不仅会导致干骺端和脊柱骨折数量增加，还会使骨折治疗变得复杂。为防止初始松动，我们基于多孔空心圆柱体的概念开发了一种具有扩大种植体/骨界面的新型植入物。我们评估了在腰椎前路稳定手术中，基于空心圆柱体的植入物在绵羊正常或骨质疏松骨中，在功能负荷条件下是否会发生骨整合。
在六只骨质疏松绵羊（年龄6.9±0.8岁，平均体重61.1±5.2千克）和七只对照绵羊（年龄6.1±0.2岁，平均体重64.9±5.7千克）中，研究了圆柱体的骨整合情况以及融合节段的状态（椎体次全切除、髂骨支撑物置换和用测试植入物固定）。通过卵巢切除术、高剂量泼尼松、减少钙和磷的饮食以及限制活动的联合方案诱导骨质疏松。使用荧光和传统组织学对骨整合进行定量；通过在六自由度加载装置中对稳定节段进行生物力学测试以及放射学和组织学分期来确定融合状态。
在所有穿孔中，70%发现有完整的骨小梁，两组之间无差异（P = 0.26）。在圆柱体内部，骨体积/总体积显著高于同一动物的对照椎体（50±16%对28±13%）（P<0.01），但显著低于周围区域（60±21%）（P<0.01）。按照“材料与方法”部分所述进行生物力学测试后，经过4个月的观察期，七例脊柱（三例健康和四例骨质疏松）被分类为完全融合，六例（四例健康和两例骨质疏松）未融合。在组织学切片中，所有终板均由完整的骨小梁桥接。
大量充满完整骨小梁的穿孔表明固定充分；所有椎体中相邻终板和三皮质髂骨支撑物之间的桥接骨小梁表明，即使在骨质疏松绵羊中，这种固定方式也足以促进该动物模型中的融合。
