Influence of preparation techniques to the strength of the bone-cement interface behind the flange in total knee arthroplasty.

Abstract

Recent clinical studies show an increased risk of femoral loosening in high-flexion TKA. Loosening seems to occur behind the anterior flange, which is covering both cancellous bone and cortical bone. It is important to optimize the interface strength between cement and both bone types to increase femoral component fixation. This study was performed to determine the cement-cortical bone interface strength for different preparation techniques. A pure tensile and shear force was applied to interface specimens. The cortical surface area was prepared in three different ways: (1) Unprepared cortical bone with periosteum; (2) Periosteum removed and cortical bone roughened with a rasp; (3) Periosteum removed and three Ø 3.2mm holes drilled through the cortex. A reference group was added with a cancellous bone surface. The interface tensile strength of Group 1 was 0.06 MPa and the shear strength was 0.05 MPa. For Group 2, respectively 0.22 MPa and 1.12 MPa. For Group 3, respectively 1.15 MPa and 1.77 MPa. For cancellous bone a tensile strength of 1.79 MPa and a shear strength of 3.85 MPa were measured. The strength of the cement-cancellous bone interface is superior to the cement-cortical bone interface. The preferred preparation technique of the cortical bone is to remove all the periosteum and drill holes through the cortex within the footprint of the anterior flange, to prevent cortical weakening. Ultimately, the proposed preparation technique will lead to longer implant survival, particularly for prostheses which are used in the high-flexion range.