The Significance Of Medial Femoral Notch On Medial Unicompartmental Knee Arthroplasty

Background: Knee osteoarthritis is one of the most commonly occurred diseases in the department of orthopedic.It is characterized by articular cartilage abrasion and degeneration,with further bone hyperplasia causing the formation of osteophyte.Patients with osteoarthritis can have pains while walking and pressing pain in the space of joints,which would result great influence on their life and work.In patients with knee osteoarthritis,there are approximately 30% of them whose conditions can be identified as knee joint anteromedial osteoarthritis.Treatments for such patients are not scarce,among them,knee medial single room replacement surgery is proved to be an effective and reliable operation after long-term clinical follow-up.But some postoperative patients are encountering with problem of the impingement between patella and femoral component.Meanwhile,the progress of the patellofemoral joint degeneration can also be seen.The reason for such problem,as research shows,may lie in the misjudgement of medial femoral notch in femoral condyle during the process of operation.This may result in wrongly choosing the type of large femoral component,which further leads to the impingement against femoral component and patella after operation.Long-term complications include knee unicompartmental displacement of the lateral compartment osteoarthritis progression and prosthetic aseptic loosening.Some scholars have put forward that the ideal angle of knee varus should be controlled at about 1° to 7° for the backward.Currently,there is a large amount of literature on medial unicompartmental knee arthroplasty.However,little research has been done on the effect of medial femoral notch on medial unicompartmental knee arthroplasty.The current research takes fulluse of the three-dimensional reconstruction imaging technology to simulate models of femoral prosthesis operation.Not only is this aimed to achieve individual customized osteotomy for each patient,but to achieve accurate selection of prosthesis type and place the prosthesis position,thus reduce the incidence of complications of patellar impingement.Purpose: This experiment involves choosing patients identified as knee joint anterior medial compartment osteoarthritis.Preoperative routine includes double knee joint CT scan,3D reconstruction and lateral radiographs of the knee.By using unicompartmental knee prosthesis template,the appropriate types and sizes of the prosthesis are selected.Besides,the researcher takes advantage of the measurement results before operation to provide further insights for selecting accurate operative techniques and optimizing surgical skills for unicompartmental arthroplasty.Materials and Methods: Patients with medial unicompartmental arthroplasty were selected from Third Affiliated Hospital of Hebei Medical University from September 2014 to the early of May 2016.Such patients were included in the current study.There were a total number of 102 cases,102knees(female 67 cases and male 35 cases,aging 50~73).The patients were randomly divided into two groups: the regular operation group and the patient-specific group(CT group).The operation was performed by the same physician,patient-specific group before operation by Radi Ant DICOM software in CT measurement and 3D reconstruction,prosthesis type may be used to determine the exact operation plan and evaluate osteotomy during operation;the regular operation group went without preoperative measurement.All patients had gone through preoperative routine knee joint CT scan,and then three-dimensional reconstruction of the femur in CT right sagittal plane,determine the distal femoral bone landmarks,determine the medial femoral condyle notch of the lowest point(A point),posterior condyle of the farthest point(B point),to determine the axis of femur in the long axis(f)after A and B respectively,two parallel lines are defined as A line and B line.The shortest distance between A line and B line is defined as H.Before and after theimplant will be used per patient size(AP value)were subtracted from the measured values of H,corresponding to the definition of the numerical value of h,h < 0 of the data is not included in the statistical analysis,h ? 0 for statistical analysis.h?0,mean the front of the femoral component beyond the medial femoral notch,may cause patellar impingement following unicompartmental arthroplasty.The femoral component was simulated with three dimensional reconstruction images to evaluate the position of the component.The two groups of all cases before and after surgery were taken with full weight-bearing lower limbs and lateral radiographs of the knee,which were followed by measurement of X-ray of posterior slope of the tibial plateau and varus angle.The range of motion(ROM)of the knee under weight-bearing condition,the KSS score as well as the VAS score of the two groups were evaluated after the operation for 8 weeks.Results: Among all of the unicompartmental arthroplasty patients,5cases had the patellar impingement and in the regular operation group,and the h values of five patients were all greater than or equal to 3mm.A total of 15 cases indicated patellofemoral joint symptoms(including patellar impingement,anterior knee pain and up and down stairs pain,table 1 and 2).h? 0,a sum of 7 cases of patellofemoral joint symptoms in the regular operation group,and 2 cases in the patient-specific group;h < 0,and there were 6 cases(3 cases in the regular operation group,3 cases in the patient-specific group,respectively)which can be identified as patellofemoral joint symptoms.There was no statistically significant difference in average of posterior slope of the tibial plateau and varus angle between the regular operation group and patient-specific group.However,There was statistically significant difference in average of the range of motion(ROM)of the knee,the KSS score and the VAS score between the two groups.Conclusions: The front of femoral component beyond the medial femoral notch 3mm will produces patellar impingement.The 3D reconstruction were performed before operation.It was found that thecombination use of prosthesis template was helpful for accurate placement of femoral component.This method can effectively avoid the patellar inpingement caused by larger selected size femoral component,the forward rotation position and the excessive of posterior condyle osteotomy.To effectively avoid the impingement between patella and femoral component by smaller selected size femoral component and the backward rotation position.Therefore,it is of great importance to simulate the osteotomy scheme under CT and 3D reconstruction images.The medial femoral condylar notch is of great significance for the location of the prosthesis in the unicompartmental arthroplasty.