Differences of knee anthropometry between Chinese and white men and women

Morphometrical measurement of resected surface of medial and lateral proximal tibia for Chinese population

PURPOSE

The objective of this study was to analyze the morphology of the medial tibial plateau and lateral tibial plateau in Chinese knees and compared these measurements and features with those of commercial unicondylar tibial baseplates.

METHODS

Three-dimensional knee models were reconstructed from computed tomography slices of 81 subjects. Among the series, 27 knees were from male subjects and 54 knees from female subjects. The dimensions and shape of the medial and lateral tibial plateaus were measured and compared with six commercially available unicondylar tibial baseplates.

RESULTS

The results showed significant differences between the shapes of the medial and lateral tibial plateaus. For the lateral tibial plateau, the shape was symmetric about the mediolateral axis. The medial plateaus presented their widest mediolateral width in an obviously more posterior position than the lateral compartment. Additionally, the plateau aspect ratio decreased with increasing mediolateral dimensions, in contrast to the constant aspect ratio shown by conventional unicondylar knee prostheses.

CONCLUSION

Compartment-specific designs may optimize coverage between the prosthesis and resected tibial surface. The morphometrical measurements presented may allow manufacturers to design tibial baseplates that accommodate the structural variability between different ethnic groups.

LEVEL OF EVIDENCE

Prospective comparative study, Level II.

Classification of gender and race in the distal femur using self organising maps

In this study gender and race differences in distal femoral morphology were investigated. Reliable anatomic knee measurements were obtained for 60 knees via MRI and direct scanning of cadaver specimens. The MRI data comprised of 20 White males and 22 White females while the cadaver specimens comprised of 18 Black males. Possible differences were investigated using a type of artificial neural network to classify the data, namely the self-organising map (SOM). The SOM suggested that clear differences are present between genders when absolute measurements are used. Male knees tended to be larger over all the measurements considered. However, when data were normalised for size, the clear differences were diminished and definite clusters were difficult to define. Black male knees tended to have larger condyle radius to anterior-posterior length ratios compared to White males. White male knees tended to be wider than White female knees. It is however suggested than when corrected for size, there exists a large variation among individual knees regardless of gender or race. It is argued that with the large variation in populations it can become advantageous not to think about gender-specific or race-specific knee replacement designs, but rather patient-specific.

The 3D analysis of the sagittal curvature of the femoral trochlea in the Chinese population

PURPOSE

An unnatural design of the sagittal geometry of the femoral trochlea may cause abnormal patellofemoral kinematics and complications after knee arthroplasty. Most previous studies examined the sagittal curvature of the femoral trochlea on 2D parasagittal planes, which may not represent the true sagittal curvature of the complex 3D femoral trochlea.

METHODS

The current study evaluated the sagittal geometry of the femoral trochlea of 100 healthy Chinese subjects (50 women and 50 men) with 3D analysis. A close-fit sphere was generated on the surface of the medial and lateral trochlear articular surface, respectively. The radii of the spheres represented the sagittal radii of the femoral trochlear sagittal curvature. A cylinder was then established and its radius was adjusted to allow the deepest points of the curved trochlear groove touching the cylindrical surface. The radius of the cylinder represented the sagittal radius of the trochlear groove.

RESULTS

In the men, the average radii of the curvature of the femoral trochlea were 18.8 ± 2.5 mm and 25.5 ± 2.8 mm for the medial and lateral femoral trochleas, respectively. In the women, the average radii of the curvature of the femoral trochlea were 20.2 ± 3.0 mm and 26.6 ± 2.7 mm for the medial and lateral femoral trochleas, respectively. The average radius of the cylinder of the trochlea groove was 19.6 ± 2.0 mm with a circular arc of 123.2° ± 13.0° in the men. In the women, the radius was 20.2 ± 1.7 mm with a circular arc of 127.9° ± 11.7°.

CONCLUSION

The present study provided a reliable and consistent assessment of the sagittal geometry of the femoral trochlea in the Chinese population. The results of the current study may be helpful to improve the understanding of the knee kinematics and develop the physiological knee prostheses.

Three-dimensional morphology of the knee reveals ethnic differences

BACKGROUND

Studies have demonstrated sex differences in femoral shape and quadriceps angle raising a question of whether implant design should be sex-specific. Much of this research has addressed shape differences within the Caucasian population and little is known about differences among ethnic groups.

QUESTIONS/PURPOSES

We therefore asked: Do shape differences in the distal femur and proximal tibia exist among different ethnic groups and between the sexes in each ethnic population? And if ethnic differences exist, do they have a clinical impact on current TKA design?

SUBJECTS AND METHODS

We analyzed 1000 normal adult knees (80 African American, 80 East Asian, and 860 Caucasian). Three-dimensional surface models were created for each bone and added to three-dimensional statistical bone atlases. Statistical shape analysis was conducted with a process combining principal components and multiple discriminate analyses. Eleven femoral and nine tibial measurements were calculated.

RESULTS

We found differences in mean measurements between the sexes and ethnicities. Males had larger knees, with a mean 5-mm-larger anteroposterior dimension than females in all ethnicities. African American females had a 7.4-mm-deeper patellar groove, 2.3-mm-smaller tibial mediolateral dimension, and 2.5-mm-larger tibial anteroposterior dimension than Caucasian females. African American males had a 4.3-mm-larger femoral anteroposterior dimension, 10.1-mm-larger tibial mediolateral dimension, and 6-mm-larger tibial anteroposterior dimension than Asian males.

CONCLUSIONS

We identified differences in three-dimensional knee morphology among Caucasian, African American, and East Asian populations. Clinical studies will be required to determine whether these differences are important for implant design.

Gender differences in the knees of Chinese population

The goal of this study was to characterize the geometry of the distal femur and proximal tibia in the Chinese population. Three-dimensional models of twenty female and twenty male knees were constructed using CT images. The morphologic measurements of the distal femur included mediolateral (ML) and anteroposterior dimension of medial and lateral condyles (MAP, LAP), femoral aspect ratio (ML/LAP), medial and lateral condylar width, intercondylar notch width, notch width index (NWI), and trochlear groove orientation. The sagittal profiles of the medial and lateral femoral condyles and tibial plateaus were also characterized. The results showed that the size of the distal femur of the females was significantly smaller than that of the males. Furthermore, when normalized by LAP, the females had a significantly narrower distal femur (ML), and a shorter MAP compared to the males. In the sagittal plane, the radius of the lateral distal circle of the femur was significantly smaller than that of the medial condyle in both genders. There were no significant gender differences in the proximal tibial geometry. The data of the present study may enable suitable modification of total knee prosthesis sizing/geometry for Asia-Pacific patients.