髋臼骨折不同台阶状移位及程度对髋关节接触特性的影响

目的模拟累及关节面负重区的髋臼骨折,分别对不同方向旋转所形成的台阶状移位进行生物力学研究,以了解应力分布及接触面积等的改变情况。方法分别测量10个完整髋臼(I组)、解剖复位(K组)、不同台阶移位(A组:1mm;B组:2mm;C组:3mm;D组:4mm;a组:-1mm;b组:-2mm;c组:-3mm;d组:-4mm)时髋臼与股骨头之间的接触特性。所获数据经统计学分析软件进行分析比较差异。结果完整髋臼负重时接触面积总面积为(7.59±4.42)cm2;K组髋臼以及A组移位髋臼保持了髋臼的解剖形态,未引起髋臼接触面积显著变化。其余类型移位均造成髋臼骨折总接触面积减小(P0.05)。负重区的接触面积在完整髋臼时为(3.72±0.04)cm2,骨折后也使之减小。解剖复位组负重区接触面积为(3.64±0.87)cm2(与完整髋臼负重区面积相比P0.05),当内旋使台阶移位达到3mm或更大,外旋移位台阶移位到3mm或更大时,负重区接触面积显著减小。结论髋臼骨折产生的台阶状移位改变了正常髋关节的生物力学特性,使髋关节的接触面积发生了重新分布。

Biomechanical consequences of different step-off displacement and degree of acetabular fractures

Objective To study biomechanical effect of different direction of the step-off caused by rotational displacement involving in the weight-bearing articular area of acetabular fracture, and to reveal the distribution and variation of stress and contact area. Methods Ten acetabular specimens were included in the study. The image information of the pressure-sensitive film after loading was scanned into the computer and analyzed by a contact pressure measurement software to calculate the area of contact. Intact（group I）, anatomical（group K）and different level of step-off (group A: 1mm; group B: 2mm; group C: 3mm; D group: 4mm; Group a:-1mm; group b:-2mm, group c: -3mm, group d: -4mm) acetabular frature were measured for contact characteristics between the acetabulum and femoral head. The data were analyzed by SPSS19.0 statistical analysis software. Results The contact area of intact acetabulum was （7.59±4.42）cm². Anatomical reduction group and group A generally had the normal structure of acetabulum and did not change the contact area significantly. The other groups caused significantly decrease of the contact area (P<0.05). The contact area of superior region in intact acetabulum was (3.72±0.04) cm², which was decreased after fracture. The pronation step-off reached 3mm or greater and supination step-off 3mm or more, superior region contact area significantly reduced. Conclusion Step-off displacement caused by acetabular fractures changes the biomechanical properties of normal hip joint and significantly alters the distribution the contact area.