Drill holes decrease cancellous bone strength: A comparative study of 33 paired osteoporotic human and 9 paired artificial bone samples.

This study was designed to compare compressive strength of cancellous bone retrieved from the femoral head in a specimen with and without guide wire hole, with comparison to synthetic bone samples. Femoral heads retrieved from 33 patients who sustained femoral neck fractures and underwent hip arthroplasty were cut into cuboids leaving two matching samples from the same femoral head. Similar samples were prepared from synthetic femurs. One of the matching samples was chosen at random and was drilled with a guide wire for cancellous screws. The uniaxial compression tests of bone blocks were carried out using the Zwick-Roell Z020 strength testing machine. The mean loss of sample cross section area due to drilling was 24%. The force at failure in drilled specimens was significantly smaller by 18% in human (median: 26%) and by 25% in synthetic bone (median 27%). The strength of human specimens was almost 2 times greater, and their stiffness nearly 4 times greater than in synthetic samples. The study shows that the weakening of the bone after drilling is roughly proportional to the loss of sample cross section area. The percentage decrease in strength was similar in human and artificial bone, but human samples were stronger and stiffer. The comparison shows that forces measured in biomechanical studies on artificial bone cannot be directly attributed to humans, but the relative differences in mechanical properties of synthetic samples after some damage may be accurate and resemble that of human bones

The cement-bone bond is weaker than cement-cement bond in cement-in-cement revision arthroplasty. A comparative biomechanical study.

This study compares the strength of the native bone-cement bond and the old-new cement bond under cyclic loading, using third generation cementing technique, rasping and contamination of the surface of the old cement with biological tissue. The possible advantages of additional drilling of the cement surface is also taken into account. Femoral heads from 21 patients who underwent a total hip arthroplasty performed for hip arthritis were used to prepare bone-cement samples. The following groups of samples were prepared. A bone-cement sample and a composite sample of a 6 weeks old cement part attached to new cement were tested 24 hours after preparation to avoid bone decay. Additionally, a uniform cement sample was prepared as control (6 weeks polymerization time) and 2 groups of cement-cement samples with and without anchoring drill hole on its surface, where the old cement polymerized for 6 weeks before preparing composite samples and then another 6 weeks after preparation. The uniaxial cyclic tension-compression tests were carried out using the Zwick-Roell Z020 testing machine. The uniform cement sample had the highest ultimate force of all specimens (n = 15; Rm = 3149 N). The composite cement sample (n = 15; Rm = 902 N) had higher ultimate force as the bone-cement sample (n = 31; Rm = 284 N; p <0.001). There were no significant differences between composite samples with 24 hours (n = 15; Rm = 902 N) and 6 weeks polymerization periods (n = 22; Rm = 890 N; p = 0.93). The composite cement samples with drill hole (n = 16; Rm = 607 N) were weaker than those without it (n = 22; Rm = 890 N; p < 0.001). This study shows that the bond between the old and new cement was stronger than the bond between cement and bone. This suggests that it is better to leave the cement that is not loosened from the bone and perform cement in cement revision, than compromising bone stock by removal of the old cement with the resulting weaker cement-bone interface. The results support performing cement-in-cement revision arthroplasty The drill holes in the old cement mantle decrease cement binding strength and are not recommended in this type of surgery