A biomechanical analysis of the annular groove on the bone - cement interface

SHEN Guo-qi; ZHANG Chun-lin

doi:10.3969/j.issn.2095-252X.2017.09.009

Abstract：Objective To identify whether the strength of bone-cement interface could be increased by changing the morphology of inner wall of bone medullary canal with grooves. Methods Self-developed new reamer was used to process fresh pig reamed femoral canal, resulting in two cortical grooves in the canal wall of the experimental group. We used the Micro-CT to scan all the models, and observed the infiltration of cement and to determin the differencs between the new bone-cement interface and the traditional interface. We used the biomechanical testing instrument to test the new and traditional bone-cement-prosthesis model ( tensile testing and rotation testing ), until the model failed. The biomechanical strength of both models was compared. We analyzed the correlation between the results of microscopic detection and biomechanical testing. Results The contact area of the bone-cement interface was greater for the experimental group ( 5470 ± 265 ) mm2 when compared to the specimens of the control group ( 5289 ± 299 ) mm2. However, the porosity for the experimental group ( 1.50 ± 0.382 ) ％ was similar to that of the control group ( 1.59 ± 0.496 ) ％. In addition, biomechanical responses to tensile loading ( 7337 ± 1825 ) N vs. ( 5564 ± 1359 ) N and anti-rotation capability ( 65.70 ± 4.83 ) N · m vs. ( 60.60 ± 4.43 ) N · m showed that the specimens of the experimental group had stronger strains at the bone-cement interface compared to the control group. In the tensile testing, the contact area of bone-cement interface and the tensile force of models had strongly significant positive correlation ( R2 = 0.85 ). In the rotational testing, the contact area of bone-cement interface and the maximal torsion had a strong correlation ( R2 = 0.77 ). The relationships between the tensile force and the porosity and the maximal torsion and the porosity were observed. ( R2 = 0.57 and R2 = 0.43 ). The FEA results compared favorably to the tensile and torsion relationships determined experimentally. Conclusions Converting the standard reaming process from a smooth boring cortical tube to one with grooves permits the cement to interlock with the reamed bony wall. This would increase the strength of the bone-cement interface. We believe that the addition of such grooves has the potential to enhance cement fixation to the bone, provide better initial fixation and extend longevity of the bone-cement-implant composite.