Risk Analysis Of The Femoral Cortical Notch In Total Knee Arthroplasty Assisted By The Patient-specific Instrumentation

Objectives:To analysis the risk and the causes of anterior femoral cortical notch when operating total knee arthroplasty(TKA)assisted by the patient-specific instrumentation(PSI).Methods:From January,2017 to December,2018,131 patients diagnosed with knee osteoarthritis(KOA)who were to undergo TKA were enrolled in this study.Patients were randomly divided into conventional instrumentation(CI)group and PSI group according to2:1.The computed tomography(CT)data of 262 entire lower extremities of the patients was collected and imported to the Mimics software to reconstruct the three dimensional(3D)bone image of the femur preoperatively.The coordinate figure of the anatomical landmarks were recorded and imported into Creo 2.0.We describe sagittal bowing of the distal femur by the angel between distal femoral anatomic axis(DFAA)and femoral mechanical axis(FMA)on the sagittal plane.This angel was measured and defined as distal femoral sagittal anteverted angle(DFSAA)in Creo.The number of intraoperative notch and postoperative notch on the lateral radiograph of knee joint were recorded.We calculated the incidence of the notch and analyzed its relationship with the DFSAA.The hospital for special surgery knee score(HSS)at 6 months after operation was evaluated and statistically analyzed.Results:The average DFSAA was 2.5°±1.5°.When DFSAA?3°,the incidence of notch was 7.10%in CI group and 33.30%in PSI group,which shows significant different in two groups(?~2=5.775,P=0.016<0.05).When DFSAA<3°,the incidence of notch was 6.5%in CI group and 5.30%in PSI group,which shows no significant different in two groups(Fisher's accurate test P=0.667>0.05).The average HSS score of the patients in CI group was 80.82±5.30(range 71-91)points at the 6th month preoperatively;the average HSS score of the patients in PSI group was 79.19±6.43(range 66-91)points at the 6th month preoperatively,with no significant difference between the two groups(P=0.126>0.05).Conclusion:DFSAA could be a risk factor of anterior cortex notch in PSI assisted TKA.Especially when the DFSAA,the risk of notching could be markedly increased.And we don't recommend surgeons to use PSI in TKA when patient's DFSAA?3°.