Biomechanical Basis And Clinical Research Of Patellofemoral Arthritis Due To The Femoral Trochlear Dysplasia

Femoral trochlear dysplasia is the abnormal anatomy of the geometrical morphology and depth at femoral trochlear groove.Femoral trochlea is a critical part of the patellofemoral arthrosis.Patellofemoral anatomy anomalies can affect the stability of the knee,induced acute injury or chronic strain of patella and femoral articular cartilage and subchondral bone that will cause pathological changes of the articular cartilage,even the patellofemoral arthritis.With the high morbidity,patellofemoral arthritis is a common disease with knee pain and dysfunction in clinics.As the population aging,the risk of patellofemoral arthritis is rising gradually,while the prevention and treatment of patellofemoral arthritis will be a long process with higher social and economic burden.Therefore,how to solve the occurrence of patellofemoral arthritis fundamentally is the hot topic and should be studied at present.The purpose of this study was to consider the femoral trochlear dysplasia as an independent factor that causes patellofemoral arthritis.On the basis of the three-dimensional finite element model,we explained the biomechanical basis and pathogenesis of femoral trochlear dysplasia.According to the conclusion,we simulated and explored the surgery of treating patellofemoral arthritis mechanically.Finally,we explored the morbidity of patellofemoral arthritis caused by trochlear dysplasia,classification and some therapeutic methods by analyzing the present clinical data.Section 1,The biomechanical basis of femoral trochlear dysplasia.In the present study,we established the finite element model of femoral trochlear dysplasia and analyzed the stress situation of joint bone and cartilage when it was loaded.Then,a virtual surgery was carried out to treat the dysplasia on the model.In order to find the biomechanical basis,we compared the stress and stain around the knee joint pre-or postoperatively.After the MRI and CT scanning,a finite element model of a knee with femoral trochlear dysplasia was established in the MIMICS software.This three-dimensional model was optimized and decorated by Geomagic Studio software.The model was loaded after material properties were given to each part.The stress and strain around the knee,including femoral and tibia bone or cartilage,were tested and analyzed when the joint flexed at 30°,60°,90°and 120°.The procedure was repeated after a virtual surgery-medial patellofemoral ligament reconstruction.As a result,no stress concentration was observed when the knee flexed at 30°.With the gradual flexion,the stress concentration was more obvious at the contact surface between the femoral condyle and patella which is a high risk of patellofeomoral arthritis.After the virtual surgery,the maximum stress contribution decreased obviously at the femoral lateral condyle in a stable mechanical environment,while the no dislocation of patella existed in loading.Section 2,The clinical research of patellofemoral arthritis was caused by the femoral trochlear dysplasia.The patients with knee chronic pain were subjected to MRI scanning were analyzed from January 1st to December 30 th in 2015.The angle of femoral groove,ratio of medial to lateral surface,depth of groove,lateral incline angle or bony prominent above tibial-femoral joint were tested in the present study.We analyzed the constituent ration,incidence age,classification and radiology according to these data.The incidence of femoral trochlear dysplasia is 36.31%,which is significantly higher than the incidence reported abroad(16.5%).Three hundred cases with femoral trochlear dysplasia were analyzed.According to the references,five parameters in MRI were analyzed for the diagnosis or categories of this knee disorder.By analyzing the three dimensional finite element model and the effect of virtual surgery,we found that the stable mechanics environment and the uniform stress distribution were shown around the knee.Therefore,we hypothesized several kinds of surgery may reduce the patients suffering from the knee disorder according to the results of the present virtual surgery,epiphyseal closure,cartilage injury and arthritis severity,such as osteotomy,elimination of the prominent,ligament reconstruction and so on.The uniform mechanical distribution may be shown after the correction of trochlear geography,bone structure or the repair of ligament.Conclusions: a,the change of biomechanical stability in patellofemoral joint,caused by femoral trochlear dysplasia,could induce acute or chronic injury of cartilage or subchondral bone in patella or femur.This pathological change of joint subchondral bone often leads to severe patellofemoral arthritis.b,the mortality of femoral trochlear dysplasia in the present study was significantly higher than that reported in references.c,the finite element analysis showed an significant improvement of mechanical environment and unobvious stress concentration in the knee with FTD after ligament reconstruction.d,in accordance with the classical measurement,the parameters chosen in the present study showed an advantage in the diagnosis and classification of femoral trochlear dysplasia.