外弓股骨膝内翻患者固有内翻力线的术前计划

Preoperative planning of constitutional varus alignment in patients with varus knees and coronal femoral lateral bowing

目的比较股骨带有冠状面外弓(FLB)的膝内翻患者与直形股骨(SFS)健康膝志愿者股骨轴线,探寻FLB患者的术前固有内翻力线(CA),指导全膝关节置换(TKA)时股骨远端外翻纠正角(VCA)的选取。方法2018年1至12月于新桥医院测量45例(90例膝)FLB及膝内翻患者的股骨近端解剖轴内侧角(MPFA)及远端解剖轴外侧角(a-LDFA),并与25名(50膝)SFS健康膝志愿者的数据进行比较。测量患者基于股骨远端机械轴(DMA)的VCA—DMA和股骨远端解剖轴(DAA)形成的夹角,并与志愿者基于中立位机械轴(NMA)的VCA进行比较。测量FLB患者的股骨外弓角(α)度数,并与患者基于NMA的VCA进行Pearson相关性检测。组间计量资料比较采用t检验。结果患者平均股骨外弓角α为7.8°±2.7°。FLB患者MPFA和a-LDFA与SFS志愿者间差异均无统计学意义(分别为84.9°±3.7°比85.6°±1.8°和81.7°±1.7°比81.2°±1.6°,t=1.26、1.70,均P>0.05)。SFS志愿者基于NMA的VCA为5.5°±0.6°(4.5°~7.4°),FLB患者组DAA-DMA角为5.3°±0.7°(4.3°~7.8°),组间差异无统计学意义(t=1.70,P=0.09)。FLB患者组基于NMA的VCA为8.4°±1.5°(5°~10°),与股骨外弓角α呈强正相关(R=0.607,P<0.01)。结论FLB患者不仅股骨远近端不存在显著畸形,而且股骨外翻截骨角(DMA-DAA)不随外弓程度发生变化,TKA时基于DMA行股骨远端截骨,可保留股骨外弓,恢复患者下肢力线至术前的固有内翻状态。

Objective To investigate the preoperative constitutional varus alignment(CA)inpatients withvarus osteoarthritic knees and coronal femoral lateral bowing(FLB)by comparing the femoral axis of the patients and volunteers′with straight femoral shaft(SFS)and healthy knees,which would be used to guide the selection of valgus correction angle(VCA)of distal femur in total knee anthroplasty(TKA).Methods From January 2018 to December 2018,45 nonconsecutive patients(90 knees)with varus osteoarthritic knees and obvious FLB(>5°)received primary TKA,and 50 limbs with healthy knees and SFS in 25 volunteers were studied at Xinqiao Hospital.The medial proximal femoral angle(MPFA)and anatomic lateral distal femoral angle(a-LDFA)were measured and compared between the two groups.The VCA formed by distal femoral mechanical axis(DMA)and distal femoral anatomic axis(DAA)in patients and the VCA based on neutral mechanical axis(NMA)in volunteers were also compared.The Pearson′s correlation analysis was performed between the angle of bowing(α)and the VCA based on NMA in patients.The measurement data was compared with t test between the two groups.Results The results showed that the MPFA and the a-LDFA were not significantly different between the volunteers with SFS and patients with FLB(MPFA:84.9°±3.7°vs 85.6°±1.8°and a-LDFA:81.7°±1.7°vs 81.2°±1.6°,t=1.26,1.70,both P>0.05).The VCA based on NMA in volunteers with SFS was 5.5°±0.6°(4.5°-7.4°),the preoperative DAA-DMA angle was 5.3°±0.7°(4.3°-7.8°)in patients with FLB,there was no significant difference between the two groups(t=1.70,P=0.09).The angle of bowing(α)was 7.9°±2.9°(6°-16°),the VCA based on NMA was 8.4°±1.5°(5°-10°),there was a significantly positive correlation between VCA andα(R=0.607,P<0.01).Conclusion There is no significantly proximal or distal femoral deformity in patients with varus osteoarthritic knee and FLB(>5°),the degree of the DMA-DAAangle based on the DMA doesn′t change with the increasing angular deformity of the bowing,then the bowing would be reserved if the distal femur is cut based on DMA in TKA and the preoperative CA should be restored successfully.