Schmidhammer Robert, Zandieh Shahin, Mittermayr Rainer, Pelinka Linda E, Leixnering Martin, Hopf Rudolf, Kroepfl Albert, Redl Heinz
Ludwig Boltzmann Institute for Experimental and Clinical Traumatology and Research Center for Traumatology, Austrian Workers' Compensation Board, Vienna, Austria.
J Trauma. 2006 Jul;61(1):199-205. doi: 10.1097/01.ta.0000195987.57939.7e.
High-resolution microcomputed tomography (microCT) is one of the most recent technical developments to visualize and quantify primarily cancellous bone. Regarding bone formation, microCT is becoming increasingly important, although its reliability has not yet been evaluated. Our study had two goals: to develop a reproducible nonunion model and to determine the efficacy of microCT for the assessment of bone healing in this model.
The designed fracture model in the rat simulates secondary fracture healing. After plate fixation to the femur, diaphysis transverse middiaphyseal osteotomy was performed with a reciprocating saw, resulting in a 0.38-mm gap with a defect of bone and periosteum corresponding to the thickness of the blade. Proximally and distally to this gap, the periosteum was preserved. Thus, three separate zones were defined: proximal femur diaphysis with periosteum, gap, and distal femur diaphysis with periosteum. In the nonunion group (NM group), a model of impaired bone healing (nonunion), silicone foil was wrapped around the femur diaphysis to block any influence from surrounding tissue. Coverage of the bone repair site by thigh muscles was designed for a model of bone union (M group). Four weeks postoperatively, callus formation was determined by conventional anterior-posterior and lateral plain radiographs. Ten weeks later, a second x-ray series was done as the clinical standard evaluation method. Afterward, specimens were harvested for microCT examination (two-dimensional and three-dimensional [3D]). Biomechanical testing was carried out to determine fracture healing.
Our model is highly reproducible and results in bone nonunion in five out of six cases (83.3%). In determining fracture site, plain radiographs the least reliable method in comparison to the biomechanical testing which is the most accurate reference method. In contrast, microCT (the 3D reconstruction) showed significant correlation (r = 1) to the results assessed by biomechanical testing, whereas microCT was correct in 100%. We found bone healing in five out of six animals in the M group verified by microCT (in accordance to biomechanical data). In the M group, significantly enhanced bone formation (50%) (p = 0.008) was observed within the osteotomy site (i.e. within the gap), but there was no difference in periosteal bone formation between the groups proximally and distally to the gap. Interestingly, we did not find statistically significant differences in mineralization.
We conclude that microCT with 3D reconstruction is the optimal method diagnostic tool in fracture healing, especially in nonunion. Furthermore, direct coverage of the fracture site by muscle flaps results in a mineralized enhanced bone formation within the osteotomy site (i.e. within the gap). Skeletal muscle coverage hypothetically might have osteogenic augmentation potential, thus being able to prevent pseudoarthrosis.
高分辨率微型计算机断层扫描（microCT）是可视化和量化主要为松质骨的最新技术发展之一。关于骨形成，microCT变得越来越重要，尽管其可靠性尚未得到评估。我们的研究有两个目标：建立一个可重复的骨不连模型，并确定microCT在评估该模型中骨愈合的有效性。
在大鼠中设计的骨折模型模拟二期骨折愈合。在将钢板固定到股骨后，用往复锯进行骨干中段横行截骨，形成一个0.38毫米的间隙，伴有与锯片厚度相应的骨和骨膜缺损。在这个间隙的近端和远端，骨膜被保留。因此，定义了三个不同的区域：带骨膜的近端股骨干、间隙和带骨膜的远端股骨干。在骨不连组（NM组），建立一个骨愈合受损（骨不连）的模型，用硅箔包裹股骨干以阻断周围组织的任何影响。大腿肌肉对骨修复部位的覆盖设计用于骨愈合模型（M组）。术后四周，通过常规前后位和侧位平片确定骨痂形成。十周后，进行第二次X线检查作为临床标准评估方法。之后，采集标本进行microCT检查（二维和三维[3D]）。进行生物力学测试以确定骨折愈合情况。
我们的模型具有高度可重复性，六例中有五例（83.3%）导致骨不连。在确定骨折部位时，与最准确的参考方法生物力学测试相比，平片是最不可靠的方法。相比之下，microCT（三维重建）与生物力学测试评估的结果显示出显著相关性（r = 1），而microCT的正确率为100%。我们发现M组六只动物中有五只经microCT证实有骨愈合（与生物力学数据一致）。在M组中，截骨部位（即间隙内）观察到骨形成显著增强（50%）（p = 0.008），但间隙近端和远端组之间的骨膜骨形成没有差异。有趣的是，我们没有发现矿化方面的统计学显著差异。
我们得出结论，三维重建的microCT是骨折愈合尤其是骨不连的最佳诊断工具。此外，肌瓣直接覆盖骨折部位会导致截骨部位（即间隙内）矿化增强的骨形成。假设骨骼肌覆盖可能具有成骨增强潜力，从而能够预防假关节形成。
