| ObjectiveThe knee joint is the largest, most complicated and injured joint in the body. There is a high incidence rate of knee joint on account of its complex anatomic structure and axial mode of exercise. Diagnosis of knee joint's disease is in view of eikonic imagings. Because of the complex structure of knee joint, X-ray or CT or MRI imaging have there own dominances. But there are few research papers and anatomical informations of sectional anantomy of the knee joint. It is significant for knee joint to reconstruct and visualize in anatomy and clinical diagnosis and treatment. The finite element model of knee joint is established by finite element method, endued with different material properties and exerted conditions on it. It is helpful to research the biomechanical characteristics of knee joint by being enduing with different material properties, analyzing by finite element software and simulating distribution and changes of stress force of different fractions of knee joint. In order to provide macroscopic and real morph data to clinical diagnosis and treatment of knee joint diseases, this research surveyed the interrelated morphosis of knee joint like meniscuses and cruciate ligaments using the sectioned specimen on sagittal, coronal and cross-sectional planes and MRI images. To explore the methods for reconstruction and visualization of three-dimensional(3D) finite element models of knee joint, the digital model of knee joint were reconstructed based on the MRI images by using three-dimensional renconstructive software and then the finite element model were also reconstructed successfully and it also could establish the basis for the finite element analysis and virtual hepatic surgery.Materials and methods1. 27 sectioned anatomical specimen of knee joint were collected, the morphologic characteristics and regularities were surveyed on sagittal, coronal and cross-sectional planes, and the correlated data were collected and analyzed statistically.2. The MRI images of 100 normal adult vital knee joint were collected, the morphologic characteristics and regularities were surveyed on sagittal, coronal and cross-sectional planes, and the correlated data were collected and analyzed statistically.3. The MRI thin layer scanning dates set of a donor's right knee joint were used, two-dimensional images data were collected. The 3D models of knee joint were reconstructed by using Mimics(Materialise's Interactive Medical Image Control System) 10.0 software. Then introduct the 3D models into the ANSYS finite element analysis software and the finite element models were established successfully.ResultsThe first part Sectional Imaging Anatomic Study of Knee JointOn sagittal plane of sectioned collections, the sagittal diameter of medial meniscus(MM) was (40.36±4.73)mm, the height of anterior horn was (4.98±1.83)mm and the height of posterior horn was (4.45±1.44)mm while those of lateral meniscus(LM) were (34.51±2.18)mm, (3.54±1.24)mm, (6.15±1.43)mm respectively. The sagittal diameter of medial tibial plateau was (46.78±3.19)mm and the sagittal diameter of lateral tibial plateau was (43.59±1.78)mm. The sagittal diameter of MM accounted for (86.61±11.06)% of the medial tibial plateau and the sagittal diameter of LM accounted for (69.08±28.04)% of the lateral tibial plateau. The sagittal diameter of MM was larger than LM, the height of posterior horn was larger than MM and homolateral anterior horn. The length of anterior cruciate ligament(ACL) was (29.66±4.21)mm, the thickness was (10.03±1.97)mm, the length of femur's attachment region was (13.84±6.11)mm, the length of tibia's attachment region was (28.08±6.90)mm while those of posterior cruciate ligament(PCL) were (40.26±6.81)mm, (11.24±3.50)mm, (24.00±10.13)mm, (14.28±5.52)mm respectively. The length and the length of femur's attachment region of ACL were less than PCL, and the length of tibia's attachment region was larger than PCL. There was no obvious difference compared to the thickness of ACL and PCL.On sagittal plane of images, the sagittal diameters of masculine and feminine MM were (41.55±2.44)mm and (36.84±2.37)mm, the heights of anterior horns were (6.85±1.15)mm and ( 6.24±1.08)mm, the heights of posterior horns were (6.53±1.28)mm and (5.47±0.89)mm. The sagittal diameters of masculine and feminine LM were (33.91±2.57)mm and (31.01±2.51)mm, the heights of anterior horns were (4.74±0.89)mm and (4.69±1.26)mm, the heights of posterior horns were (6.61±0.64)mm and (6.42±0.90)mm. The sagittal diameters of masculine and feminine medial tibial plateau were (43.79±2.90)mm and (39.75±2.73)mm while the sagittal diameters of lateral tibial plateaus were (43.93±3.40)mm and (40.20±2.61)mm. The sagittal diameter of masculine MM accounted for (95.09±5.78)% of the medial tibial plateau and the feminine was (77.57±7.52)%. The sagittal diameter of masculine LM accounted for (92.82±4.92)% of the lateral tibial plateau and the feminine was (77.33±6.47)%. The indexes of masculine were larger that of feminine except the heights of anterior and posterior horns of LM. The sagittal diameter and the heights of anterior horn of MM were larger than LM, the feminine height of posterior horn of LM was larger than MM but there was no differences between masculine MM and LM. The height of posterior horn of feminine MM was less than anterior horn. While the height of posterior horn of masculine LM was larger than anterior horn. Respectively, the lengths of masculine and feminine ACL were (36.97±4.01)mm and (32.83±4.16)mm, the thicknesses were (8.94±2.33)mm and (7.97±2.20)mm, the lenths of femur's attachment region were (11.91±2.68)mm and (10.37±1.97)mm, the lenths of tibia's attachment region were (13.27±3.33)mm and (11.88±2.97)mm. The lengths of masculine and feminine ACL were (39.07±3.78)mm and (34.11±3.72)mm, the thicknesses were (5.31±1.06)mm and (5.07±1.22)mm, the lenths of femur's attachment region were (9.32±2.00)mm and (9.07±1.75)mm, the lenths of tibia's attachment region were (13.04±4.03)mm and (12.53±3.40)mm. The length, thickness, length of attachment region of masculine ACL were larger than that of feminine and the difference was statistically significant (P<0.05). The length of masculine PCL was larger than feminine and other indicators were no obvious difference. The length of ACL was less than PCL but the thickness and the lenths of femur's attachment region was larger. There was no obvious difference between the lenths of tibia's attachment region of ACL and PCL.On coronal plane of sectioned collections, the width and transverse diameter of anterior horn of MM were (17.72±4.00) mm and (30.46±3.09) mm; the height, width and transverse diameter of caudomedial part were (5.59±0.89) mm, (8.45±1.59) mm and (33.81±1.76) mm; the width and transverse diameter of posterior horn were (20.54±3.77) mm and (32.05±2.19) mm. While those of LM were (20.11±1.74)mm, (29.43±3.24)mm; (6.67±1.01)mm, (11.03±1.78)mm, (35.58±2.71)mm; (19.20±5.24)mm, and (30.92±2.12)mm respectively. The width of tibial plateau was (70.00±3.46) mm. The width of caudomedial part of MM accounted for (12.07±2.16)% of tibial plateau while that of LM accounted for (15.77±2.57)%. The height and width of LM caudomedial part and the transverse diameter were larger than MM but others were no difference. The height and width of MM posterior horn were larger than anterior horn while the height of LM posterior horn was larger than anterior horn. The frequency of meniscofemoral ligament was 75.00%. The long diameter of ACL on coronal plane was (15.18±3.25)mm, the short diameter was (6.37±1.32)mm, the width of femur's attachment region was (8.13±1.55)mm and the width of tibia's attachment region was (16.06±5.51)mm, while that of PCL were (18.79±3.35)mm, (8.03±1.46)mm, (21.09±6.05)mm, (11.79±6.23)mm. The width of PCL and femur's attachment region were larger than ACL, but the width of tibia's attachment region was less.On coronal plane of images, the widths of anterior horn of masculine and feminine MM were (13.83±6.31)mm and (12.91±6.56)mm, the transverse diameters were (23.46±10.35)mm and ( 21.63±10.73)mm; the heights of caudomedial part were (6.22±1.18)mm and (5.72±0.92)mm, the widths were (8.56±1.89)mm and (7.58±1.61)mm, the transverse diameters were (36.03±2.57)mm and (33.29±2.15)mm; the widths of posterior horn were (22.01±2.62)mm and (19.22±2.56)mm, the transverse diameters were (31.54±2.82)mm and (28.43±2.62)mm. While the widths of anterior horn of masculine and feminine LM were (20.11±1.74)mm and (18.86±2.70)mm, the transverse diameters were (29.43±3.24)mm and (29.90±2.90)mm; the heights of caudomedial part were (7.22±1.01)mm and (6.81±1.31)mm, the widths were (11.03±1.78)mm and (11.31±3.00)mm, the transverse diameters were (36.86±2.85)mm and (32.69±1.92)mm; the widths of posterior horn were (21.96±3.27)mm and (20.04±2.69)mm, the transverse diameters were (32.38±3.39)mm and (28.84±2.83)mm. The widths of tibial plateau were (74.34±3.88)mm and (66.57±3.11)mm. The widths of caudomedial part of male and female MM respectively accounted for (11.49±2.31)% and (11.39±2.43)% of tibial plateau while that of LM accounted for (15.21±3.87)% and (15.48±2.96)%. There were obvious differences between male and female measurements about MM except the widths and transverse diameters of anterior horn. The widths and transverse diameters of LM had sex differences(P<0.05). The widths and transverse diameters of anterior horn, the heights and widths of caudomedial part of LM were larger than that of MM. The tranverse diameters of caudomedial part of masculine LM was larger than MM but that of feminine was no difference. The posterior horn's widths and tranverse diameters of LM and MM were larger than its own anterior horn. The frequency of meniscofemoral ligament was 70.00%. The long diameters of male and female ACL on coronal plane were (7.42±1.70)mm and (7.04±1.21)mm, the widths of femur's attachment region were (17.29±2.69)mm and (15.61±2.29)mm and the widths of tibia's attachment region were (12.96±1.85)mm and (12.24±1.78)mm, while that of PCL were (8.52±1.00)mm and (7.92±1.14)mm, (8.93±1.77)mm and (9.09±1.79)mm, (10.74±1.12)mm and (10.34±1.01)mm. The lengths of male and female tibial collateral ligament(TCL) were (103.22±8.28)mm and (92.91±6.71)mm, the thicknesses were (3.11±0.62)mm and (2.69±0.50)mm. While that of fibular collateral ligament(FCL) were (47.43±4.10)mm, (43.53±3.21)mm and (3.26±0.66)mm, (3.19±0.61)mm. The width of femur's attachment region of ACL, the width of PCL, the length and width of TCL, the length of FCL had obvious sex differences(P<0.05), male were larger than female. The width of PCL were larger than ACL but the widths of attachment region were less.There were few informations of meniscus on cross-sectional plane. Universally meniscus display merely on one plane and it is difficult to show anterior horn, posterior horn and caudomedial part concurrently. On the cross-sectional plane of intercondylar eminence, the long diameter of ACL was (23.60±11.97)mm, the short diameter was (7.53±2.83)mm; while the long and short diameter of PCL were (15.23±3.84)mm and (11.08±4.65)mm. The length and thickness of TCL were (21.98±11.95)mm and (2.03±0.59)mm, the length and thickness of FCL were (5.25±1.93)mm and (2.87±0.64)mm.The second part Construction of the Three-dimensional Digital and Finite Element Model of Knee JointThree-dimensional digital model of knee joint was established successfully on the basis of MRI images, the morph of which was vivid and the anatomy signal was transpsrent. The meniscus, ligaments and other structures could be displayed simultaneously through adjusting the transparency of bones. The models could be displayed by different colors and combined randomly and it also could be viewed at any directions by amplified, zoomed down, rotated and so on. The image of three-dimensional model could be preserved by BMP or JPEG form, or be recorded by AVI form to export for displaying dynamically. The film picture was clear and fluent. The finite element model of knee joint could be established after introdueing the digital model in finite element software and it also could be analyzed further.Conclusions1. This study described characters and adjoining relationships of meniscus and ligaments of knee joint on sagittal, coronal and cross-sectional planes through observing sectioned anatomical specimens and MRI images, while investigated the best displayed plane and morphological changed regularity.2. Because of the reasons of measurements, individual differences and so on, there were a little differences between eikonic and sectioned measurements of meniscus. Through surveying and analyzing meniscuses, it revealed the morphological basis of meniscus injuries, identification of discoid meniscus and small meniscus and selection of meniscus transplants.3. Because of the reasons of measurements, individual differences and so on, there also were a little differences between measurements of cruciate ligament and collateral ligaments. The data which studied through surveying sectioned specimen and eikonic images were helpful for diagnosis, treatment, reconstruction of ligament injuries.4. The structures like bones, meniscus, ligaments could be obtained to reconstruct the three-dimensional model on the basis of MRI images. The 3D model was helpful for anatomical research and operative institution and it could be import in the finite element software to establish finite element model of knee joint. Deeply, it could also set up the basis for the biomechanical analysis of knee joint.
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