Digital Morphology Study Of Proximal Tibia Osteotomy For TKA Application

BackgroundIncreasing number of Chinese patients with osteoarthritis accept the total knee arthroplasty(TKA).Most prosthesis used in China come from Western countries,the size and shape of which are mainly for foreigner and not for Chinese.It's known that Asian ofen grow shorter and smaller than Westerner.It is necessary for us to take the measurement of Chinese knees in order to design and select the right size of knee prosthesis.The measurement methods include traditional anatomical measurement and image measurement.Traditional measurement focus on measurement through surgery or by anatomy.But it may be hard to get specimens for us.Experts have been carrying out researches on knee measurement and protheies design by X-ray.As X-ray images showing two-dimensional construction only,scientists start to take their studies with technology of CT and MRI.But neither of them could show 3D construction.Few study about section of proximal tibia is reported,which seems to ignore the fact that prosthesis is just fixed to the section of bone.Three-dimensional reconstruction can be got by section images with its orginal freqency.As two-dimenional images translated into three-dimensional,much message about the object could be received.And the three-dimensional object can be observed in any direction.In a sum,digital technique may supply a new method for precisitive measurement of knee.Based on research of other scholars,we utilize CT images of normal Chinese knee to reconstruct three-dimensional images.The knee digital model can be cut and measured by the software Mimics10.0.With the study we explore the possibility of three-dimensional reconstruction and measurement technique for TKA application.Objective1.To create a new method to measure the bone-cutting section of knee.2.To identify the difference of proximal tibia between male and female in order to provide experimental base for prosthesis design for male/female.3.To identify the difference of bone section among different cutting height and provide the experimental basis for the right height of tibial bone cutting for TKA.4.To compare Chinese bone section with other nation and provide accurate and full-scale applied anatomical basis for the Chinese knee prosthesis design.Methods1.Subjects and collection of images1.1 Between Sep,2007 and Sep,2008.CT scanning of thirty-six normal knees in adults:with 18 left male knees and 18 left female knees,aged from 18 to 55 years old,height from 158 to 185cm,without diseases or injury in knees by physical examination.1.2 Device:GE Medical systems/light speed1.3 CT scanning of the 36 knees.The ambit was 20cm in centrage of the joint space. Scanning condition:120kV,300mAs.Scanning parameters:the width of collimating device was 0.75mm;thickness was 0.75mm;slice thickness was 0.625mm;the pitch was 0.75mm.The time of scanning one slice was 200ms;the total time of scanning was 10-12s.The data of scanning images was conserved into PC by DICOM.2.Three dimensional reconstruction of kneeThe transition from CT images of knee to three-dimendional model of knee could be achieved in PC by the software of Mimics10.03.Imitated proximal tibia osteotomy for TKA application Three-dimension coordinate system was set up by software of Mimics10.0 and the best-fitting plane of tibial plateau was definited.Transparencing the knee model and translating the best-fitting plane along the Z axis with 5mm,7mm and 9mm,the cutting plane came into being.With the tool of"cut" in "simulation" of Mimics10.0, the sections of proximal tibia was formed.4.Measurement of proximal tibia sections4.1 The index of measurement included Parameters of mediolateral(ML),medial and lateral anteroposteriordimensions(MAP/LAP) of the section of proximal tibia 4.2 ML,MAP and LAP of the section were measured by the tool of Mimics10.05.Statistics AnalysisThe experimental data was analyzed by the software of SPSS13.0.Independent -Samples T Test and One-Way ANOVA were used,and an associated probability of 5%(P＜0.05) was considered significant.ResultsThe three-dimentional model of knee with satisfactory morphous and darity boundary was obtained.By the tool of "region growing",proximal tibia could be shown in isolation.The bony landmarks determining the dimenion parameters of proximal tibia were drawed and the measurement result were got by Mmics10.0.1.All data including ML,MAP and LAP of the section of proximal tibia was Gaussian distribution(P＞0.05)2.Parameters of ML of the proximal tibia section were obtained.The mean was 70.91±5.28mm,ranging from 64.30 to 79.31mm in section 1.The mean was 71.40±5.30mm,ranging from 64.60 to 79.75mm in section 2.The mean was 71.89±5.33mm,ranging from 64.90 to 80.51mm in section 3.Statistical significant difference existed between section 1 and section 3(P＜0.05)3.Parameters of MAP of the proximal tibia section were obtained.The mean was 48.30±3.20mm,ranging from 42.73 to 54.37mm in section 1.The mean was 49.66±3.25mm,ranging from 44.25 to 56.08mm in section 2.The mean was 51.02±3.38mm,ranging from 44.80 to 57.93mm in section 3.Statistical significant difference existed between section 1 and section 3(P＜0.05)4.Parameters of LAP of the proximal tibia section were obtained.The mean was 45.00±3.05mm,ranging from 39.67 to 52.31mm in section 1.The mean was 46.09±3.04mm,ranging from 40.70 to 53.27mm in section 2.The mean was 47.17±3.10mm,ranging from 41.30 to 54.22mm in section 3.Statistical significant difference existed between section 1 and section 3(P＜0.05)5.There was statistical significant difference between the data of male and female(P＜0.05)Conclusions1.It is feasible to make three-dimensional reconstruction of knee on the basis of CT images.The model is with satisfactory morphous and darity boundary without distortion.It also have a good stereoacuity and could be observed from any angle or direction.We could remove the dodge part and show the part we need by lucidification.2.The digital model could be cut and measured.With the help of 3D model,we could get accurate data of the lined-parameter of knee,which is the base of prosthese design and could reduce the complications of TKA such as prosthesis loosening.3.Significant different existed in sections between sex and among diferrent bone cutting height.Sex and resection levels should be taken into account when we design tibia prosthesis and or choose the imported prosthesis in the total knee arthroplasty. The geometry and anatomy of knee in Chinese people have significant differences from the Western people.Care should be taken when we use the prosthesis designed by Western people.