X线诊断股骨颈骨折闭合复位后轴向旋转移位的实验研究

The experimental study of X-ray diagnosis of closed reduction rotational displacement of femoral neck fractures

目的通过制作股骨颈骨折复位后轴向旋转移位模型并依据X线投照探讨评估股骨颈骨折旋转移位的最佳指标。方法取6具干燥成人完整股骨标本,男2具、女4具。设计并制作股骨近端正侧位和斜位X线投照卡具和支架。对股骨标本进行股骨颈骨折造模,根据Pauwells分型制作成Pauwells 30°、50°和70°模型(各2具),手法复位并残留旋前20°、40°和60°轴向旋转移位。对每种骨折模型进行不同角度(足侧40°、足侧20°、垂直0°、头侧20°、头侧40°)的投照,测量模型的骨小梁夹角和Garden对线指数,观察内斜位和外斜位X线片骨折线的影像特点。结果股骨颈骨折复位后存在旋前20°和40°轴向旋转移位时,在不同投照体位下旋转移位组的骨小梁夹角与解剖复位组相比差异较小。残留旋转移位为60°时,在Pauwells 30°和50°骨折模型中大部分投照角度下骨小梁模糊不清,未能测量出骨小梁夹角;Pauwells 70°骨折模型中旋转移位组的骨小梁夹角与解剖复位组相比差异较大。正位X线片中,当Pauwells 70°组旋前移位为60°时,Garden对线指数显示复位不满意(150°,142°);而Pauwells 30°组和Pauwells 50°组的所有旋转移位模型正位X线片的Garden对线指数>155°,达到可接受的复位。侧位X线片中,所有旋转移位模型的Garden对线指数>180°,均未达到可接受的复位,且在相同旋转移位下Pauwells角越大Garden对线指数越大。内斜位投照时,当投照角度偏向足侧时,股骨头与股骨干部分影像重叠,无法判断复位质量,而偏头侧投照时股骨颈显影逐渐变长,在偏头侧40°投照时股骨颈最长,可清晰观察到骨折线以及股骨近端解剖结构。外斜位投照时骨小梁走行显示不清。结论应用骨小梁夹角评估股骨颈骨折复位后股骨头的轴向旋转移位存在局限性。Pauwells 70°股骨颈骨折残留旋前移位为60°时,正位X线片Garden对线指数才能发现股骨头的轴向旋转移位。侧位X线片的Garden对线指数对判断股骨头轴向旋转移位的可靠性更好。

Objective To explore the optimal index of rotational displacement of femoral neck fractures by modeling the axial rotational displacement of femoral neck fractures after reduction and based on X-ray projections.Methods Six dry human femur specimens,comprising 2 males and 4 females,were utilized in the study.Design and manufacture a proximal femur ortholateral and oblique X-ray casting jigs and mounts.The femoral neck fracture was modeled on the femoral specimen,with Pauwells 30°,50°,and 70°models(2 each)made according to Pauwells typing.The fractures were manually repositioned with residual anterior 20°,40°and 60°axial rotational displacements.Each fracture model was projected at different angles(pedicled 40°,pedicled 20°,vertical 0°,cephalad 20°,and cephalad 40°),and the trabecular angle and Garden's alignment index of the model were measured to observe the imaging characteristics of the fracture line on the medial oblique and lateral oblique radiographs.Results In the presence of a 20°and 40°anterior rotational displacement following reduction of a femoral neck fracture,the trabecular angle in the rotationally displaced group was not significantly different from that of the anatomically repositioned group in various projection positions.However,when a residual rotational displacement of 60°was present,the trabeculae appeared blurred at most projection angles in the Pauwells 30°and 50°models,failing to measure trabecular angles.In the Pauwells 70°fracture model,the trabecular angle in the rotational displacement group was significantly different from that in the anatomical reduction group.In anteroposterior radiographs,when the anterior rotation displacement was 60°in the Pauwells 70°group,Garden's contralateral index showed an unsatisfactory restoration(150°,142°),whereas all rotationally displaced models in the Pauwells 30°and Pauwells 50°groups had a Garden's contralateral index of>155°,which achieved an acceptable restoration.In lateral radiographs,all rotational displacement models with Garden's alignment index>180°failed to achieve acceptable repositioning,and the larger the Pauwells angle the greater the Garden's alignment index at the same rotational displacement.In the internal oblique position with a bias towards the foot side,the image showed partial overlap between the femoral head and the shaft,making it difficult to assess the quality of the reduction.Conversely,when projected cephalad,the femoral neck appeared longer,particularly at a projection angle of 40°cephalad,allowing for clear observation of the fracture line and the anatomy of the proximal femur.The trabeculae were not well visualized in the external oblique position.Conclusion There are limitations in applying the trabecular angle to assess the axial rotational displacement of the femoral head after reduction of femoral neck fractures.The Pauwells 70°with residual rotational anterior displacement of 60°was the only way to detect axial rotational displacement of the femoral head on anteroposterior radiographs Garden's alignment index.For the determination of axial rotational displacement of the femoral head,the Garden's alignment index on lateral radiographs provides higher reliability.