Animal Experimental Study On The Influence Of Kirschner Wire's Angle On The Growth Of Epiphyseal Plate

Objective:In children fractures,epiphysis and epiphyseal plate are the common sites of bone damage.Due to the lack of blood supply and the poor capacity of regeneration,epiphyseal and epiphyseal plate injury often cause serious consequences,such as the formation of bone bridge,epiphyseal plate closed early,thus resulting in limb shortening and(or)angular deformities and other serious complications.At present,there is no consensus on the standardized treatment of epiphyseal injury.With the rapid development of material science,cell and genetic engineering in recent decades,absorbable materials and bioengineering treatment has made great progress to the treatment of epiphyseal injury.Despite this,these new approaches have not been widely used and endorsed due to the high expend,high technical requirements,longer treatment cycles and so on.And the traditional smooth Kirschner wire plus plaster immobilization is still the main treatment.Our experiment aims to explore whether the different angle formed by the needle and the epiphyseal plate will cause different impact on the growth of epiphysis when we treat epiphyseal injury using Kirschner wire.Methods:1.Animal model: The experimental animals were 60 male New Zealand white rabbits,aged 4 to 6 weeks,weighing 0.5~0.9 kg.Young rabbits were randomly divided into three groups and numbered A,B,and C.In above three group,the right distal femoral epiphysis plate is selected as the experimental site,and the left as the control group.Anesthesia was performed by using 3% sodium 1.0/kg in the ear marginal vein.After the success of anesthesia,the immature position of the young rabbit fixed on the rabbit stage,electric felting device to remove the young rabbit knee joint rabbit hair,conventional iodophor disinfection three times,paved a one-time sterile hole towel.The right knee of each group was cut in the middle of the knee,the patella was pulled to the outside and the joint capsule was cut to expose the distal articular surface of the femur.A,B,C three experimental groups were used 2.0 mm kirschner wire.Femur longitudinal axis of 30°,45°,60° angle through the femoral condylar fossa at once through the distal femoral epiphyseal plate to reach the metaphysis.Absorbable thread suture incision.Disinfect the wound dressing to prevent infection.Intramuscular injection of penicillin 400,000 unites / day for one week to prevent infection.Left lower limb surgery only exposed articular surface without damage the epiphyseal plate by kirschner wire.Three groups of young rabbits were placed in the clean environment sub-cage feeding,free activity.2.Imaging examination: X-ray examination was used to measure the lower limbs femoral condyle/valgus angle.CT was used to observe the development of femoral condyle and bone bridge.3.Specimen measurements : All New Zealand white rabbits were sacrificed by air embolism.Then we dissect out bilateral femoral specimens.The femur length of each rabbit was measured with a 0.02 mm vernier caliper and the bilateral femoral intercondylar transverse diameter of each group.4.Histological examination: The distal part of the femur was intercepted.After rinsing with 0.9% sodium chloride solution,the specimens were immediately placed into 4% paraformaldehyde(pH=7.4),4 ?fixed for 48 h,then 20% of EDTA decalcified was used to decalcificate for 4 weeks,then replace the decalcifying fluid every 3 days.After the decalcification,with graded ethanol dehydrated,transparent in xylene,longitudinal paraffin embedded,made of thick layer 6 micron longitudinal tissue sections,HE staining was used to observe the pathological changes of epiphyseal plate injury.Results:1 Observation of specimens: One rabbit of A group died of nailing infection in the second week after surgery.One in B group died of diarrhea in the 5th week after operation.All the young rabbits survived in group C.All deaths were excluded during the experiment.Observing the femoral specimen we found that there was no obvious shortening deformity and distal femoral development is normal in A and B group.But in group C,Some specimens were visually recognizable shortening deformity,Right femoral distal developmental delay.Data from the length of the measured femur are consistent with the normal distribution.All the measured data by paired t test,A,B two groups of femur length difference was meaningless,C group differences were significant.Results from distal femoral intercondylar transverse diameter measurements were shown that only C group differences were significant.Comparison between the groups.Not only length,but also the transverse diameter,the difference between A and B is not significant,while both of A and B compared with C,the difference were significant.2 Imaging examination: X-ray examination revealed that the three groups of control group in the femur there are about 6 ° valgus angle.A and B groups of angle measurement results by paired t test,the difference was not statistically significant.C group differences were significant.In CT,only in the small scan layer to see the bone bridge image.In the C group,the experimental side development slower than the control side.Comparison between groups,the difference between A and B is not significant,while both of A and B compared with C,the difference were significant.3 Histological examination: Observing the tissue sections found that three groups of young rabbits experimental side can be seen early bone bridge formation,but the formation of 30° group of bone bridge is more coarse,obvious.In the Kirschner wire through the bone tunnel caused by the distribution of fat cells,fibroblasts,trabecular bone.In the bone tunnel distribution of fat cells,fibroblasts,trabecular bone,three groups of epiphyseal plate to varying degrees to the metaphyseal bending.Conclusion:Different angles across the epiphyseal plate can cause different effects.When the angle between piphyseal plate and kirschner wire is more than 45°,the impact on the epiphyseal plate longitudinal and lateral growth capacity is not obvious.But while the angle is less than 30°,both vertical and lateral growth capacity will be significantly affected.