The Effect Of Patella Baja Induced By Infrapatellar Fat Pad Resection On The Femoral Condyle

Objectives To explore the feasibility of removaling Infrapatellar fat pad in adult NEW Zealand rabbits,eventually inducing the animal model of patella baja.To study the effect of patella baja caused by removaling Infrapatellar fat pad on femoral condyle from the aspects of cartilage and subchondral bone.Methods Twenty-four 24-week-old NEW Zealand rabbits were randomly divided into three groups:IR group,Sham group and Control group.The Infrapatellar fat pad resection was performed in IR group,no substantial artificial intervention was performed in Control group,open the knee joint and one incision was performed on the patellar tendon in Sham group..From the model date,3% pentobarbital sodium solution(1.5mg/kg)was injected through ear vein 2 months later,took X-ray of the left lower extremity,applied to Insall Salvati index and Blackburne-Peel index method to evaluate the rabbit patellar position,and measure the patellar tendon length and leading edge to the patellar tendon,which is to detect the length of the patellar ligament and to determine the patellar fat removal,then executed by injecting air through ear vein,fixed specimens.Determination of all samples of distal left femoral condylar bone tissue morphology by Micro-CT,all rabbits left knee were decalcified for 8 weeks,gross morphological observation of femoral condyle articular surface,followed by paraffin embedded and sliced,then underwent toluidine blue staining and histological observation.The general morphology were analyzed according to OARSI morphological score,Toluidine blue stained sections were analyzed according to OARSI histological score.The expression level of COL-II and Caspase-3 were assessed respectively by immunoradioactive score.SPSS20.0 statistical analysis software was used for statistical analysis of all data,and P < 0.05 indicates statistical difference.Results 1 In the X-ray,IR group compared with Sham group and Control group,the position of patella in IR group was significantly decreased,and all patellar height parameters were decreased.The difference was statistically significant(P< 0.05).Control group and Sham group had no obvious abnormal difference was not statistically significant(P>0.05).2 The OARSI histological scores were no significant difference in IR group,Sham group and Control group.There were no significant articular cartilage surface coarse and fibrosis,color change is not obvious,also does not appear obvious cartilage wear and erosion,and the difference has no statistically significant(P>0.05).3 The OARSI histological scores were no significant difference in IR group,Sham group and Control group.There were no obvious articular cartilage surface crack and defects,hyaline cartilage not wear,chondrocyte morphology,cartilage cell density is not obvious change,did not appear chondrocytes cluster proliferation significantly.The difference has no statistically significant(P>0.05).4 Compared with Control group?Sham group,IR group had an increase of medial joint capsule repair score,but it did not reach statistical significance(P>0.05).Compared with Control group and Sham group,there was no statistical difference(P>0.05).Compared with Control group?Sham group,IR group was no significant difference on the expression of COL-II,it did not reach statistical significance(P>0.05).Compared with Control group and Sham group,there was no statistical difference(P>0.05).5 Micro-CT analysis found that compared with IR group,Control group and Sham group,BMD?BV/TV?Tb.pf?SMI?Tb.Th were no significantly change,and the difference has no statistically significant(P>0.05).Conclusions 1 It is proved that the NEW Zealand rabbit with the Infrapatellar fat pad resection can successfully induce the development of patella baja.It is an ideal animal model of the patella baja.2 In this experiment,patella baja caused by removing the Infrapatellar fat pad has almost no effect on femoral condyle in the early stage.