| Objective:1. To investigate relationship of the reference axes related with rotational alignment of the distal femur, and provide theoretical basis for the position of femoral prosthesis rotational alignment during the total knee arthroplasty.2.To investigate the accuracy of the lower extremity alignment and distal femur rotational alignment in the cadaveric total knee arthroplasty(TKA) assisted by individual navigation templates.3.To investigate the accuracy of the lower extremity alignment and position of the femoral and tibial prosthesis acquired in the total knee arthroplasty(TKA) assisted by patient-specific navigation templates.Method:1.Eighty healthy adults (male, female each40cases) were involved and the distal femurs were scanned by CT. Positioning each anatomical landmark in the continuous section images using MIMICS software and selecting8images around the image in which femoral epicondyle groove located. Measuring the following angles: The posterior condylar angle(PCA),which is formed by the posterior condylar line and the surgical transepicondylar axis; The condylar twist angle(CTA),whcin is formed by the posterior condylar line and the clinical transepicondylar axis;the angle between the perpendicular line of anteroposterior line and the posterior condylar line(APA). Reconstructing the distal femur based on the continuous section images coordinate automatic generate the reference axes related with rotational alignment of the distal femur.Measuring the angle of PCA, APA, CTA in the three-dimensional image and investigating relationship of them.2.Twenty whole adult cadavers were randomly divided into two groups, each group has20specimens. In group1, individual navigation templates were used for TKA. The lower limb was scaned preoperatively by CT. The computer generates a model of the lower extremity by using the reverse-engineering software to process the CT data, then a navigational template was constructed as the inverse of the distal femur and proximal tibia surface with some navigational holes to define the osteotomy position in the computer. The navigational templates produced an accurate model using a rapid prototyping (RP) technique to assist cadaveric TKA. In group2, conventional method for cadaveric TKA was performed according to routine operation. CT scans were performed postoperatively to evaluate the angles of the osteotomies of the distal femur and proximal tibia campare to the mechanical alignment. And osteotomies of the posterior condylar surface to the surgical transepicondylar axis of the two TKA methods.3.Selected40cases of knee osteoarthritis patients to our hospital,18cases (20) of male, female,22cases (26), and randomly divided into the navigation template group and the traditional method. In the navigation group patient-specific navigation templates were used for TKA and in the traditional group conventional methods were performed. The lower limbs of the group two were scaned preoperatively by CT. The computer generates a model of the lower extremity by using the reverse-engineering software to process the CT data, then a navigational template was constructed as the inverse of the distal femur and proximal tibia surface with some navigational holes to define the osteotomy position in the computer. The navigational templates produced an accurate model using a rapid prototyping (RP) technique to assist cadaveric TKA. In group two, conventional method for cadaveric TKA were performed according to routine operation. Post-operative leg alignment and component orientation was determined on long-leg coronal and lateral X-rays.Results:1. The angles in the continuous section images were as follows:PCA:1.92°(-0.92°～4.2);APA:2.55°(0.2°～5.8°);CTA:5.33°(2.1°～8.03°).The angles in the three-dimensional reconstruction images were as follows:PCA:male3.54°±0.61°, the female3.61°±0.39°; APA:male3.39°±0.42°, the female3.66°±0.53°; CTA:male6.21°±0.65°, the female6.02°±0.43°. There were no statistically differences between male and female for the angle of PCA and APA (P>0.05), the same between left and right legs.2.The individual-specific navigation templates fit tightly with the femur condyle and tibia plateau. In group1,twenty knee osteotomies of the distal femur and proximal tibia were angled88.5°～91.4°(mean90.2°) to the femur mechanical alignment,mean90.2°. and the osteotomies of proximal tibia were angled89.5°～91.0°(mean90.4°) to the tibia mechanical alignment.Seventeen knee osteotomies of the posterior condylar surface were parallel to the surgical transepicondylar axis,three knee joints have an angle less than1°. In group2,all twenty knee joints show genu varum or genu valgum deformity;five knee joints of these deformities were more than5°. All twenty knee osteotomies of the posterior condylar surface have an included angle with the the surgical transepicondylar axis;ten knee joints of these were more than3°.3.All the patient-specific navigation templates fit perfectly with the femur condyle and tibia plateau. The median value of all mechanical axis values was180.3°±1.9°. Only two cases exceeded the ideal value of180°by3°。 A good overall alignment was observed regarding the positioning of both femoral and tibial prosthesis on the frontal and sagittal plane.In frontal plane, The median value of the femeral prosthesis angle was90.7°±1.5°. whereas the median tibial prosthesis angle was89.9°±1.7°. in the sagittal plane, The median value of the femeral prosthesis angle was90.5°±3.6°. Whereas, the median tibial prosthesis angle was85.3°±2.8°.Conclusions:1. The reference axes related with rotational alignment of the distal femur measured in continuous section images ranged greatly, which is unfavorable to position the rotational alignment. The three dimensional reconstruction technique can accurately detect reference axes related with rotational alignment of the distal femur based on the CT, be easy for reconstructing distal femeral rotational alignment.2. Patient-specific navigation templates in total knee arthroplasty can acquire an accurate the lower extremity alignment and distal femur rotational alignment.3.Patient-specific navigation templates in total knee arthroplasty can acquire an accurate lower extremity alignment and position of the femoral and tibial prosthesis, it also has an advantage over the conventional method. |
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