股骨远端前皮质平面在全膝关节置换术中判断股骨假体外旋角度的参考意义

Plane of distal femur anterior cortex is useful index for femoral component rotation in total knee arthroplasty

目的研究全膝关节置换术(TKA)中股骨远端前皮质平面对判断股骨假体外旋角度的参考作用。方法采集2011年1月至2013年12月在中山大学附属第一医院放射科行膝关节CT检查的数据资料27例,其中1例右下肢曾行骨科手术致术后畸形被排除,共53侧下肢CT资料。病例纳入标准:(1)无明显先天性下肢骨骼畸形;(2)无明显膝关节化脓性感染变形;(3)下肢无严重骨科术后改变。排除标准:(1)膝关节化脓性感染变形者;(2)伴膝关节外下肢畸形者;(3)下肢有骨科手术史致畸形者。利用Mimics 16.0软件对扫描数据进行分析,将CT扫描资料三维重建后,计算股骨远端前皮质平面分别与股骨后髁连线(PCL)及通髁线(CEA)在股骨远端内外髁间解剖横截面上的夹角(分别定义为前皮质角及前皮质通髁角),和CEA与PCL构成的髁扭转角(CTA)。最后采用Kolmogorov-Smirnov检验法,单独t检验等方法统计数据。结果前皮质角总体平均数为-(4.7±3.8)°;CTA总体平均数为+(5.2±2.5)°;前皮质通髁角总体平均数为-(9.2±5.8)°,前皮质角、髁扭转角、前皮质通髁角分别在性别间均无统计学差异(P>0.05)。(其中正值代表股骨外旋方向,负值代表股骨内旋方向)。结论股骨远端前皮质平面与CEA之间的夹角约为内旋9°,在TKA中可通过前皮质平面掌握CEA方向进而调整股骨假体外旋角度,对提高股骨假体安装精确度具有实际意义。

Objective To investigate the effect of the plane of the distal femur anterior cortex on the femoral rotation determination in total knee arthroplasty（ TKA）. Methods Between January 2012 and December 2013,CT scan data of 53 knees of 27 adults（ 19 males,eight females） were collected by radiological department of the First Affiliated Hospital of Sun Yat-sen University. Only one case was excluded due to the post-operative deformity caused by the previous orthopedic surgery on the right leg. The inclusion criteria were as follows： no obvious congenital bone deformity on the lower limbs,no knee purulent infection,and no severe postoperative knee deformity. Exclusion criteria： knee joint deformation with pyogenic infection; other deformity of the lower limbs; limb deformation after orthopedic surgery. The scanned images of the lower limb were imported into Mimics 16. 0 software,and the femur models were constructed through extraction and segmentation of bone CT values; the anatomical axes and the planes of the distal femur anterior cortex were positioned. The angle between the posterior condylar line（ PCL） and clinical epicondylar axis（ CEA）,known as condylar twist angle（ CTA）,the angle between the plane of distal femur anterior cortex and PCL,and the angle between the plane of distal femur anterior cortex and CEA（ defined as ACA） were all measured in three dimentions（ 3D）. Kolmogorov-Smirnov test and Student＇s t test were used to analyze the measured value. Results The average of the angle between the plane of distal femur anterior cortex and PCL is-（ 4. 7 ± 3. 8） °. The mean of CTA was ＋（ 5. 2 ± 2. 5） ° and the average of ACA was-（ 9. 2 ± 5. 8） °. Each angle measured above showed no significant difference in the gender（ P〉0. 05）.（ Positive value represents the external rotation of the femur and negative value represents the internal rotation of the femur）. Conclusion The angle between the plane of distal femur anterior cortex and CEA is about 9°of endorotation,which indicates that the plane of distal femur anterior cortex can help accurately determine CEA and position the rotation angle of femoral component,so as to achieve the ideal installation position of femur prosthesis.