Claes Lutz, Veeser Andreas, Göckelmann Melanie, Simon Ulrich, Ignatius Anita
Institute of Orthopaedic Research an Biomechanics, University of Ulm, Helmholtzstrasse 14, 89081, Ulm, Germany.
Arch Orthop Trauma Surg. 2009 Jul;129(7):923-8. doi: 10.1007/s00402-008-0692-9. Epub 2008 Jul 25.
Experimental studies on metaphyseal fractures are rare and do not control the biomechanical conditions in the healing zone. This study aimed to develop an improved experimental model, which characterizes and controls the biomechanical condition in the fracture gap of a metaphyseal fracture.
A partial osteotomy model in the distal femur of the sheep was developed. The osteotomy was located in the region of the trochlea groove. The osteotomy gap was 3 mm wide. The retro-patellar force acting on the joint in vivo causes a bending of the trochlea resulting in a narrowing of the osteotomy gap. To limit and control this interfragmentary movement, stainless steel plates of various thicknesses were implanted into the osteotomy gap. Forces acting on the trochlea were analyzed and a load-deflection curve of the model was determined in vitro. A pilot study on two sheep was performed using the new model with two different interfragmentary movements of 0.3 or 1 mm. Eight weeks, post-operatively, the sheep were sacrificed and undecalcified histology was performed.
The biomechanical analysis of the joint forces and the in vitro load-deflection behavior of the trochlea revealed that the forces acting on the trochlea were high enough to cause an interfragmentary movement of 1 mm in the osteotomy gap. This was confirmed by an X-ray of the sheep, which showed a closing of the proximal osteotomy gap under weight-bearing conditions. The histological section revealed no external callus formation. The sheep with the 0.3 mm interfragmentary movement showed almost complete bridging of the osteotomy gap with woven bone whereas the sheep with the 1 mm interfragmentary movement exhibited new bone formation only at the borderline of the osteotomy but larger areas with connective tissue or even fibrous cartilage in the center of the gap.
This metaphyseal bone-healing model provides defined and adjustable biomechanical conditions. The histological images demonstrated intramembranous and endochondral bone healing in the osteotomy gap without callus formation. The model therefore seems appropriate to study metaphyseal bone healing under differing mechanical conditions.
关于干骺端骨折的实验研究较少，且未对愈合区域的生物力学条件进行控制。本研究旨在开发一种改进的实验模型，该模型能够表征并控制干骺端骨折骨折间隙中的生物力学条件。
建立绵羊股骨远端的部分截骨模型。截骨位于滑车沟区域。截骨间隙宽3毫米。体内作用于关节的髌后力会导致滑车弯曲，从而使截骨间隙变窄。为了限制和控制这种骨折块间运动，将不同厚度的不锈钢板植入截骨间隙。分析作用于滑车的力，并在体外确定模型的载荷-挠度曲线。使用新模型对两只绵羊进行了初步研究，骨折块间运动分别为0.3毫米或1毫米。术后8周，处死绵羊并进行不脱钙组织学检查。
对关节力的生物力学分析以及滑车的体外载荷-挠度行为表明，作用于滑车的力足以在截骨间隙中引起1毫米的骨折块间运动。绵羊的X射线证实了这一点，其显示在负重条件下近端截骨间隙闭合。组织学切片显示无外骨痂形成。骨折块间运动为0.3毫米的绵羊，截骨间隙几乎完全被编织骨桥接，而骨折块间运动为1毫米的绵羊，仅在截骨边缘有新骨形成，间隙中央有较大面积的结缔组织甚至纤维软骨。
这种干骺端骨愈合模型提供了明确且可调节的生物力学条件。组织学图像显示截骨间隙内有膜内成骨和软骨内成骨，无骨痂形成。因此，该模型似乎适合研究不同力学条件下的干骺端骨愈合。
