Messer-Hannemann Philipp, Campbell Graeme M, Morlock Michael M
Institute of Biomechanics, Hamburg University of Technology, Hamburg, Germany.
Institute of Biomechanics, Hamburg University of Technology, Hamburg, Germany.
Clin Biomech (Bristol). 2019 Oct;69:96-103. doi: 10.1016/j.clinbiomech.2019.07.014. Epub 2019 Jul 13.
Deformation of acetabular cups when press-fitted into an undersized cavity is inevitable due to the inhomogeneous stiffness of acetabular bone. Thinner cups or screw holes might increase the risk of high cup deformation. The aim of this study was to examine the influence of cup design and liner assembly on the deformation response during cup implantation.
Acetabular cups with different designs were implanted into polyurethane foam models simulating the anatomical situation with nominal press-fits of 1mm and without nominal press-fits (line-to-line). Deformations were determined using a tactile coordinate measuring machine. A 3D laser scanner was used to determine the contact conditions at the cup-cavity interface. Polyethylene and ceramic liners were assembled to the implanted cups and the influence of the insertion on the deformation response evaluated. Fixation strength of the cups was determined by push-out testing.
Cup deformation increased with smaller wall thickness (P < 0.037) and screw holes (P < 0.001). Insertion of ceramic liners reduced the deformation (P < 0.001), whereas polyethylene liners adapted to the deformation of the implanted cups (P > 0.999). Thin-walled cups exhibited a higher fixation strength for similar implantation forces (P = 0.011).
Thin-walled cups achieved higher fixation strengths and might be more bone-preserving. However, in combination with screw holes and high press-fit levels, wall thickness should be considered carefully to avoid excessive cup deformations leading to potential complications during liner assembly. Line-to-line insertion of thin-walled cups should be accompanied with a rough surface coating to minimize the loss of fixation strength due to the low press-fit fixation.
由于髋臼骨刚度不均匀，压配到尺寸过小的髋臼腔时髋臼杯变形不可避免。较薄的髋臼杯或螺钉孔可能会增加髋臼杯高度变形的风险。本研究的目的是研究髋臼杯设计和衬垫组装对髋臼杯植入过程中变形反应的影响。
将不同设计的髋臼杯植入模拟解剖情况的聚氨酯泡沫模型中，名义压配量为1mm，以及无名义压配（线对线）。使用触觉坐标测量机确定变形情况。使用三维激光扫描仪确定髋臼杯与髋臼腔界面处的接触情况。将聚乙烯和陶瓷衬垫组装到植入的髋臼杯上，并评估插入对变形反应的影响。通过推出试验确定髋臼杯的固定强度。
髋臼杯变形随壁厚减小（P < 0.037）和螺钉孔（P < 0.001）而增加。插入陶瓷衬垫可减少变形（P < 0.001），而聚乙烯衬垫适应植入髋臼杯的变形（P > 0.999）。对于相似的植入力，薄壁髋臼杯表现出更高的固定强度（P = 0.011）。
薄壁髋臼杯获得了更高的固定强度，可能更有利于保留骨质。然而，结合螺钉孔和高的压配水平时，应仔细考虑壁厚，以避免髋臼杯过度变形导致衬垫组装过程中出现潜在并发症。薄壁髋臼杯线对线插入时应伴有粗糙表面涂层，以尽量减少由于低的压配固定导致的固定强度损失。
