The Animal Experimental Study About The Impact Of The Implant Retention And Removal On The Degeneration Of Acetabulum Cartilage

Objective: To develop an animal model of acetabular fractures,then on the basis of the model,to explore the relationship between cartilage degeneration of acetabulum and long stay of implant after internal fixation of acetabulum fracture on the basis of the developed animal model,in order to provide experimental reference for clinical evaluation of the implant removed or not after the operation of acetabular fracture.Methods: Part One Development and validation of experimental animal models about posterior wall acetabular fracture of rabbits——A pilot study: Thirty mature New Zealand rabbits were used,in vivo extended non weight-bearing radiography of the rabbit hip joint was standardized(60 hips),obvious deformity and dislocation were excluded,the lateral center–edge angle(LCEA)and acetabular-head Index(AHI)were measured by picture archiving and communication systems(PACS)and results were compared with the value of normal adult.Another twenty-four mature New Zealand rabbits were used and were divided into three groups randomly and equally,the groups B and C subjected to surgery using heavy impact method simulation high-energy fracture of acetabulum.The load between the femoral head and acetabulum was measured by pressure transducer.Anteroposterior X-radiography of hip was implemented after 3 months,a semi-quantitative scoring system about OA was applied to each radiographic image.The cartilage tissue of posterior wall was bisected from acetabular after sacrificed,the sections were rated using the Mankin Histologic Rating System.Part Two The animal experimental study about the impact of the different time of retained implant on the degeneration of acetabulum cartilage: Fifty-seven mature New Zealand rabbits were used,obvious deformity and dislocation were excluded.Those rabbits were used and were divided into four groups randomly,group I is intact and as normal controls(N=12),the group S is sham operation(N=15),the group NFF is no fracture and fixed(N=15),the group FF is posterior wall fracture and fixed(N=15),the animal model of acetabular posterior wall fracture and internal fixation was produced as Previous mentioned.After 3 months with fracture healed,the first,second and fourth month are selected as the observation point respectively.Anteroposterior X-radiography of hip was implemented and blood was drawn from the rabbit ear marginal vein were collected.After that the acetabulum cartilage tissue were harvested following euthanization at the selected observation point(n = 4 per group I and n = 5 per group S,NFF,FF for each time point).At multiple time points after surgery,a semi-quantitative scoring system about OA was applied to each radiographic image.The CTX-II and COMP levels in the serum were analyzed by ELISA.The cartilage tissue of the undamaged areas was examined with H-E and Toluidine blue,and Mankin scores were assessed.Further with immunohistochemical technique and real-time quantitative reverse transcription PCR(Rt-PCR)detection of the change of cartilage cell metabolism balance related factors and protein expression level.Part Three The animal experimental study about the impact of implant removal on the degeneration of acetabulum cartilage: Another fifty-seven mature New Zealand rabbits were used,obvious deformity and dislocation were excluded.Those rabbits were used and were divided into four groups randomly,group A as intact and as normal controls(N=12),the group B as sham operation(N=15),the group C as implant retention(N=15),the group D as implant removal(N=15),the group C and D were carried out as the model of acetabular posterior wall fracture and internal fixation as previous mentioned.After 3 months with fracture healed,the implants were removed in the group D,at the same time the group B were executed the second sham operation.After that,the first,second and fourth month are selected as the observation point respectively.Anteroposterior X-radiography of hip was implemented and blood was drawn from the rabbit ear marginal vein were collected.After that the acetabulum cartilage tissue were harvested following euthanization at the selected observation point(n = 4 per group A and n = 5 per group B,C,D for each time point).At multiple time points after surgery,a semi-quantitative scoring system about OA was applied to each radiographic image.The CTX-II and COMP levels in the serum were analyzed by ELISA.The cartilage tissue of the undamaged areas was examined with H-E and Toluidine blue,and Mankin scores were assessed.Further with immunohistochemical technique and real-time quantitative reverse transcription PCR(Rt-PCR)detection of the change of cartilage cell metabolism balance related factors and protein expression level.Results: Part One Development and validation of experimental animal models about posterior wall acetabular fracture of rabbits——A pilot study: The mean LCEA of normal adult rabbit is(29.94 ± 3.63)°(95 % confidence interval is 29.12~30.75).and the mean AHI is(84.59 ± 1.57)%(95% confidence interval is 84.18~84.99).There are all in the normal reference value range of adult human.The contact stress delivered to the acetabulum was 45 MPa.The X-radiography and histology of hip joint exhibited obvious differences in change after three months.Compared with the control group,the group B showed hip joint with post-traumatic osteoarthritis combined subluxation,the cartilage has an irregular surface,fibrous tissue and osteophyte can be seen with collagen deposition in continuity with hypertrophic chondrocytes,calcifying cartilage;the group C identified overhydration,malalignment and proliferation of cartilaginous cells on the posterior wall of the acetabulum.The result of hip OA semi-quantitative scoring and Mankin scores were B>C>A,there was a statistical differences(P <0.05)between the three groups respectively.Part Two The animal experimental study about the impact of the different time of retained implant on the degeneration of acetabulum cartilage : There was none of the rabbits in the observation period does appear obvious complications or deaths.Significant differences were observed at the IP-1、IP-2、IP-4 months after surgery between the the experimental group and the control groups.NFF group and FF group were observed early mild degeneration performance in the IP-4 month after surgery.The result of hip OA semi-quantitative scoring were higher than the control group and the sham operation group,there was a statistical differences(P <0.05)between the groups respectively.The serum CTX-II and COMP levels were increased gradually at various times after surgery,there were significant differences(P <0.05)between the two groups and controls were observed.The NFF group and FF group identified overhydration,malalignment and proliferation of cartilaginous cells on the the acetabulum cartilage tissue,the result of Mankin scores were increased gradually with time extensions and were FF>NFF>I,there was a statistical differences(P <0.05)between the three groups respectively.The Aggrecan and Collagen-Ⅱ expression level show obvious decreased trend with time extensions gradually in the NFF group and FFgroup,on the contrary,the MMP-13 expression levels were increased gradually at various times after surgery,there were significant differences(P <0.05)between the two groups and controls.Further through real rt-pcr test results show that there was no obvious factor and protein expression changes involved cartilage metabolism balance in group I and group S.In the NFF group and FF group,the signaling pathways ALK-5 —PAI-1—Collagen-Ⅱinvolved cartilage anabolism and repair were observed low gene expression level at the beginning of the study and shows decreased trend gradually.Contrarily,the signaling pathways ALK-1—Id-1—MMP-13 involved cartilage catabolism were observed low high expression levels at the beginning of the study and were increased gradually at various times after surgery.The rate of ALK-1/ALK-5 shows rising trend gradually,there were significant differences(P <0.05)between the two groups and controls.Part Three The animal experimental study about the impact of implant removal on the degeneration of acetabulum cartilage:There was none of the rabbits in the observation period does appear obvious complications or deaths too.Significant differences were observed at the IP-1、IP-2、IP-4 months after surgery between the the experimental group and the control groups.Group A and B were observed early mild degeneration performance in the IR-4 month after surgery,The result of hip OA semi-quantitative scoring were higher than the control group and the sham operation group,there was a statistical differences(P <0.05)between the groups respectively.We found that the serum CTX-II and COMP peak levels appeared in the first month after the second surgery,then after that the levels were decreased until the end,the group B drop to normal levels gradually and the group D still higher than the control group.On the contrary,the group C levels were increased gradually until the end.Interestingly,the levels of group B and D arrived at the same level in the IR-4 month.The group C and D identified overhydration,malalignment and proliferation of cartilaginous cells on the the acetabulum cartilage tissue,the result of Mankin scores showed obvious rising trend with time extensions gradually and were D>C>B>A,there was a statistical differences(P <0.05)between the groups C,D and A,B respectively.The Aggrecan and Collagen-Ⅱ expression levels were decreased gradually at various times after surgery in groups C and D.On the contrary,the MMP-13 expression levels were increased at various times after surgery,there were significant differences(P <0.05)between the two groups and controls.Further through real rt-pcr test results show that there were no obvious factors and protein expression changes involved cartilage metabolism balance in group A.In the group B,C and D,the gene expression levels of signaling pathways ALK-5—PAI-1—Collagen-Ⅱ involved cartilage anabolism and repair were decreased gradually at various times after surgery.In addition,the expression levels of signaling pathways ALK-1—Id-1—MMP-13 involved cartilage catabolism were increased gradually at various times after surgery.It was worth noting that there was not significant differences(P >0.05)between the groups B and controls,but there were significant differences(P <0.05)between the groups C,D and controls.The rate of ALK-1/ALK-5 shows increased trend gradually,there were significant differences(P <0.05)between the two groups and controls.Conclusion: The rabbit model of acetabular fractures was developed in our study,which can simulate human posterior wall acetabular fracture effectively,and the model is suitable for animal experiment research about the disease associated with acetabular fractures.The retained implants around the acetabulum could break cartilage metabolism balance,which increased the cartilage catabolism and deteriorated cartilage degeneration,more over,the cartilage degeneration would deteriorate gradually with the increased time of implants retention.It is interesting to note,compared to continue to maintain the implants retention after internal fixation of acetabulum fracture,the implants removal does not reduce or alleviate the progress of cartilage catabolism,the progress of cartilage degeneration is stii going on.The implants removal will not alleviate the progress of cartilage degeneration of hip joint after postoperation of acetabulum fracture,but the improvement of function and subject feeling need be further researched.