The Study Of The TKA Related Morphology Of Posterior Condyle Of People In South Of China

BackgroundKnee osteoarthritis(O A)is the most prevalence degenerative disease in the elderly.It is important for the diagnosis and treatment of OA to understand its pathogenesis.The abnormal morphology and kinematics of femoral condyle will lead to abnormal distribution of contact stress on the articular surface,which account for the degenerative changes of the knee joint.The posterior condyle is one of the main components of the femoral condyle,but there is little knowledge about the relation between OA etiology and the morphology of the posterior condyle,due to the difficulties in studying this part.Total knee arthroplasty(TKA)is the ultimate method for the treatment of knee osteoarthritis(OA),and the successful operation requires appropriate and matching prosthesis.But at present,the design of the posterior condyle of the prosthesis is insufficient:For one thing,the symmetrical design of the posterior condyle leads to the suspension of the lateral posterior condyle;In addition,the medial pivot movement of the knee is restored by the asymmetric design of the insert but not posterior condyle,which is inconsistent with the anatomical and physiological of the normal knee.ObjectiveThe three-dimensional reconstruction and virtual surgery technologies would be used to compare the anatomical parameters related to the posterior condyle.By analyzing the results,we further investigate the relationship between etiology of the OA and the morphology of the femoral posterior condyle.Besides,based on the anatomical features of the posterior condyle,advice for the deficiencies of the posterior condyle design of the prothesis would be given.Method60 patients with knee OA and 60 healthy persons were included in current study.The full-length CT images of their lower limbs were collected for the reconstruction of the three-dimensional model.The coordinate system of the femur was established based on the mechanical axis of the lower limb,rotation axis of the femur and the axis of the femoral anterior cortex.The radius and inclination of the posterior condyle were measured based on the standard reference plane set by coordinate system.Then,TKA bone cut of the distal and posterior condyle were performed,and the width,height and inclination angle of the posterior condyle were measured.t-test was used to compare the anatomical parameters’differences between normal and OA subjects,medial and lateral of the posterior condyle,male and female.Pearson correlation coefficient was use to analyze the relationship between the anatomical parameters of the posterior condyle and the subjects’ height.Covariance statistical method was used to was applied to eliminate interference factor of the height of the subjects.P values less than 0.05 were considered significant.Result(1)There are significant differences between OA and normal people in the PC A angle,the inclination of the medial and lateral posterior condyles,and the height and width of the medial and lateral posterior condyles.The significant differences between normal and OA knees were different between male and female,with PCA angle and the width of the medial and posterior condyles differences were observed in female subjects while the angle of inclination of the medial and posterior condyles,the width of the medial and posterior condyles,and the height of the medial and posterior condyles were observed in male subjects;(2)All anatomical parameters were significantly different between medial and lateral posterior condyle before TKA bone cut;(3)here is significantly different in the radius of posterior between male and female,even eliminate the interference factor of the height of the subjects between genders;(4)There is no significant difference in all anatomical parameters of posterior condyle after TKA bone cut but the inclination angle;(5)The turning point of the resected surface of the lateral posterior condyle was about 3/4 from the distal end of the posterior,and the inclination of the resected surface proximal to the turning point was outward while the distal part was inward.(6)Although there were no significant gender differences in the inclination angle,significant differences were observed between gender in width and height of the osteotomy surface,even eliminate the interference of the height of the subjects;(7)Different races studies showed that the medial posterior condyles were relatively vertical and the lateral posterior condyles were medially inclined,but the angle of the inclination was different among races.(8)The differences of the average radius of posterior condyles among current study and other Chinese population studies were less then 1mm,but were beyond 2 to 3mm among current study and other foreigners’ studies.;(9)There is no significant differences between width and height of the resected posterior condyles in both Chinese and other races;(10)The width ratio of the medial and lateral posterior condyles of OA patients was different from normal,with medial posterior condyle was wider than lateral in OA patients,while normal knee exhibited the opposite results.ConclusionAs for the recommendation for the design of the prosthesis:(1)At present,the symmetry design of prosthesis lead to the suspension of the lateral posterior condyle of the prothesis,and the inclination of the lateral posterior condyle should be considered in the design of prothesis;(2)there are morphological differences between normal and OA knees.If the prosthesis is designed according to the shape of the normal knee,the prothesis design form normal knee may be suspension or uncoverage for being applied on OA knees;(3)The width,height and radius of the posterior condyles are larger in male than female,which should be considered in the design for sex specific prosthesis.(4)There are obvious racial differences in the anatomical parameters of the posterior condyle,which should be considered in the design of prosthesis,and further comparative studies among different races are needed in the future.As for the etiology of OA:(1)The size of the posterior condyle of OA patients is larger than normal,and it may be caused by the abnormal knee kinematics or the abnormal contact pressure distribution of the tibiofemoral joint surface.(2)The asymmetric inclination of the posterior condyle in OA patients is different from normal,which may cause the abnormal pivot movement in OA patients compare to normal;(3)The differences of the width of the posterior condyle between male and female indicate that the abnormal flexion movement of the etiology and development of OA may varied between genders.