Comparative Analysis Of Femoral Stem Alignment Between Direct Anterior Approach And Traditional Posterolateral Approach In Total Hip Arthroplasty In Lateral Decubitus Position

Background:Direct anterior approach(DAA)total hip arthroplasty(THA)as a true neuromuscular gap approach has been used by more and more surgeons.Besides the long learning curve of DAA,the difficulty of lifting the proximal femur during the DAA operation leads to the wrong insertion direction and the poor placement of the femoral stem prosthesis,which is considered to be the main reason for the femoral split,postoperative dislocation,and accelerated wear of the prosthesis.Especially for patients with coxa vara,iliac wing protrusion,and strong muscle strength,dissatisfaction is more likely to occur after femoral stem prosthesis implantation.It has been reported that there are differences in the alignment of the femoral stem component between the supine DAA THA and the traditional posterolateral approach(PL)THA.However,some articles have suggested that the alignment of the femoral stem component of DAA in the lateral decubitus position is not significantly different from that of PL-THA.In our clinical work,we found that there was no significant difference in the alignment of the femoral stem prosthesis in the coronal position between the DR Of the pelvic plain film reexamined after DAA and PL in the lateral position.However,so far,there is no comparative analysis study on the alignment of DAA and PL femoral prosthesis in the lateral decubitus position at the level of postoperative CT three-dimensional reconstruction.Objective:The alignment of the femoral stem in the coronal,sagittal,and axial positions 5 days after the operation was compared between the lateral decumulation DAA-THA and PL-THA using 3D CT reconstruction without artifacts.Methods:A total of 112 primary THAs(88 patients,including 62 DAA and 50PL-THA)underwent artifact removal CT scans on the fifth postoperative day,The scanning thickness was 0.64 mm and the scanning range was from the pelvis to the proximal tibia.Mimics(v.19.0,Materialise,Leuven,Belgium)was used for 3D reconstruction of the whole femur and the stem component,respectively.The femoral anatomical axis,proximal femoral axis and prosthesis axis were constructed according to the methods of previous literature.The surgical transepicondylar line of the femoral condyle was marked on two-dimensional CT images,and the anteversion Angle of the femoral stem prosthesis in the axial position was measured.In the 3D reconstruction model,the standard posterior condylar plane was constructed and the coronal and sagittal planes were established.The alignment differences between the two groups of femoral stem components in the coronal and sagittal planes were measured.The lateral bows of the femoral stem axis and the proximal femoral axis relative to the femoral anatomical axis was defined as positive values,and the medial bows were defined as negative values.We defined the Angle between the axis of the femoral stem and the axis of the proximal femur on the coronal plane as a value of-3° to 3° for neutral implantation,greater than 3° for varus implantation,and less than-3° for valgus implantation.The Angle between the axis of the femoral stem and the axis of the proximal femur on the sagittal plane was-3° to 3°,which was defined as neutral implantation,more than 3° as extension implantation,and less than-3° as flexion implantation.Results:There was no significant difference in the axial femoral anteversion Angle between the DAA group and PL group(22.9°±12.9°vs24.3°±14.2°,p=0.567).There was a significant difference in coronal alignment between the two groups(-1°±1°vs-1.4°±1.2°,p=0.02),while there was no significant difference in the incidence of varus and valgus between the two groups(p=0.104).There was no varus implantation in the two groups.There was 1 case(1.6%)of valgus implantation in the DAA group and 4 cases(8.0%)of valgus implantation in the PL group.There was also a significant difference in sagittal alignment between the two groups(-0.4°±1.2°vs0.1°±1.6°,p=0.032).There was also no significant difference in the incidence of insertion in flexion and extension positions between the two groups(p=0.801 and p=437).There were 2 cases(3.2%)of flexion implantation in the DAA group,2 cases(4.0%)of flexion implantation in the PL group,1 case(1.6%)of extension implantation in the DAA group,and 2 cases(4.0%)of extension implantation in the PL group.The implantation rate of the DAA group in the neutral position in the coronal and sagittal planes was 98.4% and 95.2%,respectively.In the PL group,the implantation rate in the neutral position was 92% in both coronal and sagittal views.Conclusions:There was no significant difference between DAA and PL in the axial position,but there was a significant difference in the coronal and sagittal implantation,but the difference was within the neutral implantation range.We believe that the lateral decubitus DAA-THA can obtain good 3D alignment of the femoral stem.