Ulm University, Department of Orthopaedic Trauma, Ulm, Germany.
Injury. 2013 Oct;44(10):1327-32. doi: 10.1016/j.injury.2013.05.008. Epub 2013 Jun 12.
Proximal humerus fracture fixation can be difficult because of osteoporosis making it difficult to achieve stable implant anchorage in the weak bone stock even when using locking plates. This may cause implant failure requiring revision surgery. Cement augmentation has, in principle, been shown to improve stability. The aim of this study was to investigate whether augmentation of particular screws of a locking plate aimed at a region of low bone quality is effective in improving stability in a proximal humerus fracture model.
Twelve paired human humerus specimens were included. Quantitative computed tomography was performed to determine bone mineral density (BMD). Local bone quality in the direction of the six proximal screws of a standard locking plate (PHILOS, Synthes) was assessed using mechanical means (DensiProbe™). A three-part fracture model with a metaphyseal defect was simulated and fixed with the plate. Within each pair of humeri the two screws aimed at the region of the lowest bone quality according to the DensiProbe™ were augmented in a randomised manner. For augmentation, 0.5 ml of bone cement was injected in a screw with multiple outlets at its tip under fluoroscopic control. A cyclic varus-bending test with increasing upper load magnitude was performed until failure of the screw-bone fixation.
The augmented group withstood significantly more load cycles. The correlation of BMD with load cycles until failure and BMD with paired difference in load cycles to failure showed that augmentation could compensate for a low BMD.
The results demonstrate that augmentation of screws in locked plating in a proximal humerus fracture model is effective in improving primary stability in a cyclic varus-bending test. The augmentation of two particular screws aimed at a region of low bone quality within the humeral head was almost as effective as four screws with twice the amount of bone cement. Screw augmentation combined with a knowledge of the local bone quality could be more effective in enhancing the primary stability of a proximal humerus locking plate because the effect of augmentation can be exploited more effectively limiting it to the degree required.
由于骨质疏松症，肱骨近端骨折的固定较为困难，即使使用锁定板，也很难在脆弱的骨质上实现稳定的植入物锚固。这可能导致植入物失败，需要进行翻修手术。骨水泥强化在原则上已被证明可以提高稳定性。本研究旨在探讨针对骨质量较低区域的锁定板的特定螺钉进行强化是否能有效提高肱骨近端骨折模型中的稳定性。
纳入了 12 对配对的人肱骨标本。通过定量计算机断层扫描（quantitative computed tomography，QCT）测定骨密度（bone mineral density，BMD）。使用机械手段（DensiProbe™）评估标准锁定板（PHILOS，Synthes）的六个近端螺钉方向的局部骨质量。通过模拟干骺端缺损的三部分骨折模型并用板固定。在每对肱骨中，根据 DensiProbe™，随机对两个指向最低骨质量区域的螺钉进行强化。在透视控制下，通过在其尖端带有多个出口的螺钉注入 0.5ml 骨水泥进行强化。在发生螺钉-骨固定失败之前，进行增加上加载量的周期性内翻弯曲测试。
强化组承受了更多的循环加载。骨密度与失效前的循环加载次数的相关性以及骨密度与失效前的配对循环加载次数差异的相关性表明，强化可以补偿低骨密度。
结果表明，在肱骨近端骨折模型中，锁定板螺钉的强化在周期性内翻弯曲测试中可有效提高初始稳定性。强化两个特定螺钉（针对肱骨头内骨质量较低的区域）的效果几乎与强化四个螺钉（使用双倍骨水泥）的效果一样好。螺钉强化结合对局部骨质量的了解可以更有效地增强肱骨近端锁定板的初始稳定性，因为可以更有效地利用强化效果，使其仅限于所需的程度。
