Sandmann Gunther, Ateschrang Atesch, Freude Thomas, Stöckle Ulrich, Schmölz Werner, Konrads Christian, Döbele Stefan
Sportsclinic Ravensburg, Ravensburg, Germany.
Department of Trauma and Reconstructive Surgery, BG Klinik, University of Tübingen, Schnarrenbergstr. 95, 72076, Tübingen, Germany.
J Exp Orthop. 2020 Oct 12;7(1):82. doi: 10.1186/s40634-020-00293-z.
Angular stable implants reduced the complication rate in the treatment of humeral head fractures. But the failure rate is still high. To further reduce the risk of cut-out, cement augmentation of screws was introduced. A reason for failure of plate osteosynthesis might be the extremely high stiffness of the screw-plate interface leading to a loss of reduction and cut-out of screws. A more homogeneous distribution of the forces on all screws may avoid secondary dislocation. We hypothesize that dynamic osteosynthesis minimizes screw loosening and results in a higher load to failure than standard locking screws.
Twelve paired human humerus specimens were analysed. A standardized three-part fracture model with a metaphyseal defect was simulated. Within each pair of humeri, one was fixed with a Philos plate and standard locking screws (LS), whereas the other humerus was fixed with a Philos plate and dynamic locking screws (DLS). A cyclic varus-bending test or a rotation test with increasing loading force was performed until failure of the screw-bone-fixation.
In the varus bending test, pairs failed by screw loosening in the humeral head. The LS-group reached 2901 (601-5201) load cycles until failure, while the DLS-group failed after 3731 (2001-5601) cycles. This corresponds to a median loading of 195 N for the LS-group and 235 N for the DLS-group (p = 0.028). In the rotation test the LS-group reached a median of 1101 (501-1501) load cycles until failure of fixation occurred, while the DLS-group failed after 1401 (401-2201) cycles (p = 0.225).
Plate fixation using dynamic locking screws for the treatment of proximal humerus fractures demonstrated more load cycles until failure compared to standard locking plate osteosynthesis.
角度稳定型植入物降低了肱骨头骨折治疗中的并发症发生率。但失败率仍然很高。为了进一步降低螺钉穿出的风险，引入了螺钉骨水泥强化技术。钢板接骨术失败的一个原因可能是螺钉-钢板界面的刚度极高，导致复位丢失和螺钉穿出。使所有螺钉上的力分布更均匀可避免继发移位。我们假设动态接骨术可最大限度减少螺钉松动，并导致比标准锁定螺钉更高的破坏载荷。
分析12对人肱骨标本。模拟具有干骺端缺损的标准化三部分骨折模型。在每对肱骨中，一个用Philos钢板和标准锁定螺钉（LS）固定，而另一个肱骨用Philos钢板和动态锁定螺钉（DLS）固定。进行循环内翻弯曲试验或加载力增加的旋转试验，直至螺钉-骨固定失效。
在内翻弯曲试验中，各组均因肱骨头螺钉松动而失败。LS组在2901（601 - 5201）个加载循环后失败，而DLS组在3731（2001 - 5601）个循环后失败。这对应于LS组的中位加载力为195 N，DLS组为235 N（p = 0.028）。在旋转试验中，LS组在固定失效前达到中位1101（501 - 1501）个加载循环，而DLS组在1401（401 - 2201）个循环后失败（p = 0.225）。
与标准锁定钢板接骨术相比，使用动态锁定螺钉进行钢板固定治疗肱骨近端骨折在失效前显示出更多的加载循环。
