Comparative Study Of The Morphology Of The Trochlear Groove Between Chinese Knee Joint And Artificial Prosthesis

Purpose: This study aimed to investigate the natural morphology of the femoral trochlear groove tracking based on quantitative measurement,and discuss the relationship between the trochlear groove tracking and femoral condylar size,geometrical shape,and anatomical alignment,and analyze whether imported prostheses were designed with physiological trochlear grooves.Methods: Femur models of fifty males and fifty females of healthy Chinese adults were recruited for analyzing the natural trochlear groove morphology using three-dimensional software.Firstly,coaxial cutting planes(15° increments)rotating about the trochlear groove axis were created from the proximal to distal end,followed by the deepest point of the trochlear groove marked at each cross section,then analyzing the shape,position,and orientation of the trochlear groove.Secondly,the femoral condylar size(anteroposterior and mediolateral dimensions;trochlear groove radius,R),geometrical shape(aspect ratio,trochlear groove extension angle),and anatomical alignment(knee valgus physiologic angle,KVPA;mechanical medial distal femoral angle,m MDFA;surgical transepicondylar axis angle,s TEAA)in femoral condyles were measured and analysis between these parameters and groove morphology were performed.Third,the differences of trochlear groove morphology between forty-two selected femoral models and five different imported prostheses were analyzed after virtual TKAs.Results: The arc-shaped trochlear groove tracking was divided into the laterally oriented proximal part and the medially oriented distal part by turning point,and located laterally to the mechanical axis.Based on the turning point,the tracking was classified into the following four types: type 45°,60°,75°,and 90° from the lateral to medial side.Distally,they extended along a similar path.The orientation of the four types were relatively consistent,and orientated medially from the proximal to distal end,with approximately 1° at each groove point and 10° at the turning point.The average value of AP,ML,R,and arc angle showed no significant difference between types.The average distal extension angle(the part beyond 90°)and aspect ratio in type 45°,60°,75°,and 90° were 16.0° and 0.9,18.6° and 1.0,18.5° and 1.0,20.0° and 1.0,respectively,there was significant difference in between type 45° and other types(p < 0.05).The average KVPA were 5.1°,5.1°,5.1°,4.4°,respectively,there was significant difference in type 45° vs.60°,45° vs.75°,and type 45° vs.90°.The average m MDFA and s TEAA were 94.0° and 4.0°,93.3° and 3.4°,94.3° and 3.0°,95.0° and 2.0°,respectively,there was significant difference between type 90° and other types(p < 0.05).The prosthetic trochlear groove tracking showed a proximal-lateral to distal-medial orientation.The prosthetic trackings intersected with proximal part of the natural tracking and the orientation was opposite.Distally,the orientation of prosthetic and natural trackings were similar while the prosthetic tracking located medially compared to the natural one.Furthermore,the intersection areas and mediolateral positions were different between the prosthetic and different types of natural trackings.Conclusion: Individual variation exists in natural morphology of the trochlear groove tracking which is classified into different types based on the turning point.With the location of turning point shifts distally,the condylar geometry inclines to change from wide-flat to long-narrow,the tracking length increase,with the tendency of valgus alignment and decrease in external rotation of the transepicondylar axis.Current prostheses are designed with non-physiological morphology in trochlear groove trackings,and the natural trochlear could not be reproduced ideally after TKA.This study is helpful to a better understanding of the natural and prosthetic morphology of trochlear groove trackings,and improvement of prosthetic design used in TKA.