蘑菇状股骨头表面置换假体对股骨颈的生物力学影响

BIOMECHANICAL EFFECT OF MUSHROOM SHAPED SURFACE PROSTHESIS ON FEMORAL NECK AFTER REPLACEMENT

目的探讨自行设计的蘑菇状股骨头表面置换假体植入后对股骨颈的生物力学影响是否在安全范围内。方法取自愿捐赠55岁以下新鲜成人股骨上段标本4个,模拟测量股骨在站立位压力作用下,正常股骨、假体植入后初期(假体空隙内仅填充松质骨骨泥或碎骨,主要依靠螺纹和压配关系与骨骼接合)和远期(假体空隙内填充骨水泥,使其和周围骨组织完全接合)3种状态时,股骨颈狭窄处A(外侧)、B(内侧)两个测试点的应变,并采用Excel行回归分析和可信度分析。结果测试点A、B在股骨头假体植入前后的应变值经线性回归分析显示,相关系数r值均>99%,股骨颈皮质骨应变与股骨头所受载荷成正比,实验载荷未使股骨颈发生塑性变形。测试点A应变的趋势线斜率植入前为0.6719,植入后初期为0.6192,应变变化率为—7.8%;植入后远期为0.6627,应变变化率为—1.4%。测试点B应变的趋势线斜率植入前为—1.0561,植入后初期为—1.1292,应变变化率为6.9%;植入后远期为—1.0851,应变变化率为2.7%。结论蘑菇状股骨头表面置换假体植入后,股骨颈应变在安全范围内,远期应变变化率较初期小。

Objective To investigate whether the biomechanical effect of mushroom shaped surface prosthesis on femoral neck is in the scope of safety after the replacement. Methods Four donated fresh-adult specimens of upper femur under the age of 55 years old were used. The strains of detecting points A （lateral） and B （medial） on the narrow place of femoral neck in the standing position were simulated for three stages before or after the prosthesis replacement,namely the pre-replacement,the initial stage during which the interspace of the prosthesis was filled with cancellous bone,and later stage during which the interspace of the prosthesis was filled with bone cement. Then they were compared by using linear regression analysis in Excel and reliability analysis. Results The regression analysis showed that the values of correlation coefficient r were all more than 99% at the different stages,indicating the strain of femoral neck＇s cortical bone was proportional to the load and there was no occurrence of the plastic deformation of the femoral neck. For point A,the slope of the trend line of strain was 0.671 9 at the pre-replacement stage. The value of the initial stage after replacement was 0.619 2 and its change rate was —7.8%; while corresponding value was 0.662 7 and —1.4% at the later stage after replacement. For point B,the slope of the trend line of strain was —1.056 1 at the pre-replacement stage. The value of the initial stage after replacement was — 1.129 2 and its change rate was 6.9%; while corresponding value was —1.085 1 and 2.7% at the later stage after replacement. Conclusion The mechanical strength of femoral neck is in the scope of safety after surface replacement of the femoral head. The change rate of strain at the later stage is smaller than the initial stage.