髋臼覆盖率对股骨头软骨下骨微结构影响的实验研究

Experimental study on the effect of acetabular coverage on subchondral bone microstructure of femoral head

目的:髋臼覆盖率等髋关节参数在一定程度上可以反映股骨头应力分布,通过使用微型计算机断层扫描(Micro-CT)股骨颈骨折(头下型)病人行髋关节置换术后股骨头标本,研究髋臼覆盖率等髋关节参数与股骨头软骨下骨体积分数(BV/TV)的关系,进一步探究局部生物力学改变诱导的软骨下骨微结构改变,为术前计划及生物假体设计提供理论依据。方法:收集因股骨颈骨折行髋关节置换术后股骨头标本30例,对患者行术前常规CT平扫及骨盆正位片拍摄,在骨盆正位片上测量CE角、Sharp角、颈干角、髋臼前倾角等髋关节参数,对患者平扫CT进行三维重建,使用美国国立卫生研究院官方软件Image J测量股骨头髋臼覆盖面积并计算髋臼覆盖率。以股骨头凹为定位标志,分别取张力侧和应力侧软骨下圆柱状松质骨柱。将制作好的组织标本寄送至上海市第六人民医院进行Micro-CT扫描、重建并分析ROI骨体积分数(BV/TV)等参数。对髋关节参数等和软骨下骨微结构参数之间进行单因素分析、多因素线性回归等统计学分析。结果:BMI、髋臼覆盖率、CE角与因变量BV/TV(%)之间以及髋臼覆盖率(%)与CE角之间呈正相关性(P<0.05);髋臼覆盖率及BMI为股骨头张力侧与应力侧软骨下骨体积分数比值(BV/TV%)的独立危险因素(P<0.05)。结论:股骨头软骨下骨体积分数的绝对变化值与髋臼覆盖率呈正相关,股骨头覆盖不足引起的无序关节应力负荷可能导致骨小梁体积明显减少,对生物力学特性和关节软骨有害;BMI过高导致股骨头应力侧局部软骨下骨体积分数增大,可能会导致软骨下骨硬化,进而使软骨失去了应力缓冲,加重软骨损害。

Objective:Hip parameters such as acetabular coverage could reflect the stress distribution of femoral head.To study the relationship between hip parameters such as acetabular coverage and subchondral bone volume fraction(BV/TV)of femoral head by using micro-computed tomography(Micro-CT)after hip joint replacement in patients with femoral neck fracture(subcephalic type).By further exploring the changes of subchondral bone microstructure induced by local biomechanical changes,so as to provide theoretical basis for preoperative planning and design of biological prostheses.Methods:Thirty cases of femoral head specimens after hip replacement due to femoral neck fracture were collected.Preoperative conventional CT plain scan and anteroposterior pelvic radiographs were taken.Hip parameters such as CE angle,sharp angle,neck trunk angle and acetabular inclination angle were measured on anteroposterior pelvic radiographs,and three-dimensional reconstruction was performed on anteroposterior CT scan.ImageJ,the official software of the National Institutes of Health,was used to measure acetabular coverage and calculate acetabular coverage.Subchondral cylindrical cancellous bone columns on the tension side and the stress side were selected with the concave of femoral head as the location marker.The prepared tissue specimens were sent to the Shanghai Sixth People’s Hospital for Micro-CT scanning,reconstruction,and analysis of parameters such as ROI bone volume fraction(BV/TV).The relationship between hip joint parameters and subchondral bone microstructure parameters was analyzed by univariate analysis and multivariate linear regression analysis.Results:Subchondral bone volume fraction(BV/TV)on the stress side of the femoral head was significantly larger than that on the tension side,and the ratio of subchondral bone volume fraction on the stress side of the femoral head to the tension side was significantly correlated with acetabulum coverage and BMI.The greater the acetabulum coverage and BMI,the greater the ratio of subchondral bone volume fraction on the stress side of the femoral head to the tension side.Conclusion:The absolute change value of subchondral bone volume fraction of the femoral head is positively correlated with the coverage of the acetabulum.The disordered joint stress load caused by inadequate coverage of the femoral head may lead to a significant reduction in the volume of the bone trabeculae,which is harmful to the biomechanical properties and articular cartilage.Excessive BMI may lead to an increase in the local subchondral bone volume fraction on the stress side of the femoral head,which may cause subchondral bone sclerosis,it may further contribute to the loss of stress buffer of cartilage and aggravate cartilage damage.