Steinhauser E, Bader R, Simnacher M, Scholz R, Gradinger R
Klinik für Orthopädie und Unfallchirurgie, Technische Universität München.
Biomed Tech (Berl). 2005 Oct;50(10):314-9. doi: 10.1515/BMT.2005.044.
Dislocation is a severe complication after total hip replacement which may cause revision surgery in some cases. The use of constraint inserts that are coupled to the femoral head by a snapping mechanism provides an opportunity for treatment of recurrent dislocations. This study was aimed to investigate the assembling and retention forces of a specific constraint liner. Using a universal testing machine the assembling forces were determined for head sizes of 28 and 32 mm and the clinically mostly used as well as the maximum cup size. Subsequently, under variation of load direction and pull-out velocity the retention forces were investigated. For primary assembly of the head the required compressive forces were in a range from 197 N and 283 N depending on head and cup size (each size n = 3). Repeated assembly led to a decrease of these forces up to 29%. The retention forces always were slightly below the assembling forces, i. e. forces to remove the heads from the inserts were between 183 N and 230 N (each size n = 3). Repeated disconnection caused a decrease of the retention forces up to 16%. An increase of load velocity as well as an oblique load direction resulted in an enhancement of the retention forces. For all investigated implant sizes the retention force for the femoral head was approximately ten-times less than the interface strength between the insert and the metal-back. In case of correct implant handling the risk of disconnection between the tested constraint insert and the corresponding metal-back has not to be considered in clinical practice.
脱位是全髋关节置换术后的一种严重并发症，在某些情况下可能需要进行翻修手术。使用通过卡扣机制与股骨头相连的限制性衬垫为复发性脱位的治疗提供了一种机会。本研究旨在调查一种特定限制性衬垫的组装力和保持力。使用万能试验机测定了28毫米和32毫米股骨头尺寸以及临床上最常用的和最大髋臼尺寸的组装力。随后，在改变加载方向和拔出速度的情况下研究了保持力。对于股骨头的初次组装，所需的压缩力在197牛至283牛的范围内，具体取决于股骨头和髋臼的尺寸（每种尺寸n = 3）。重复组装导致这些力降低了29%。保持力始终略低于组装力，即从衬垫中取出股骨头所需的力在183牛至230牛之间（每种尺寸n = 3）。重复拆卸导致保持力降低了16%。加载速度的增加以及倾斜的加载方向导致保持力增强。对于所有研究的植入物尺寸，股骨头的保持力大约比衬垫与金属背板之间的界面强度小十倍。在正确处理植入物的情况下，在临床实践中无需考虑测试的限制性衬垫与相应金属背板之间断开连接的风险。
