Biomechanical Study Of Complicated Acetabular Fracture Treated With Internal Fixation Methods

Background: The hip joint became one of the main weight-bearing joints in the process of human being development from crawling to walk upright. Acetabular fractures are one of those injuries in which even the best efforts of the treating surgeon may not bring back the patient to his pre injury level. Our study was done to evaluate the operative results of acetabular fractures and done some biomechanical research in the complicated fracture.The first part: Clinical effect observation of complicated acetabular fracture treated with internal fixation methods. (18 cases)Objective: To observe the clinical effect of complicated acetabular fracture treated with internal fixation.Documents and Methods: 18 cases of acetabular fractures which had been treated by operating were selected from 2003 to 2007 in the First Hospital of Jinlin Universicity. All the cases were examined with X ray or spiral CT, and we have 1 cases of both column fracture, 6 cases of posterior wall fracture, 2 cases of"T"type fracture, 1 cases of posterior column and posterior wall fracture, 4 cases of transverse fracture, 2 cases of anterior column fracture,2 cases of transverse and posterior wall fracture. The surgical lag is 13casesof 0-3 days, 1cases of 4-5 days, 2 cases of 6-7 days,2 cases exceed 10 days. All the patients are treated with internal fixation and followed up successfully. All are assessed by Matta standard after surgery and are assessed by modified Merle d'Aubigne criteria.Results: As assessed by Matta standard, there was anatomical reduction in 6(33.33%), satisfied reduction in 10(55.56%), unsatisfied reduction in 2(11.11%). Of the posterior wall fracture, there was anatomical reduction in 3(50%), satisfied reduction in 3(50%); of the transverse fracture, there was anatomical reduction in 2(50%), satisfied reduction in 2(50%); the posterior column and posterior wall fracture was unsatisfied reduction in 1(100%); the transverse and posterior wall fracture was unsatisfied reduction in 1(50%). The cases treated in 7 days are all satisfied, and which treated exceed 10 days are all unsatisfied. The final functional outcome as assessed by modified Merle d'Aubigne criteria, was excellent in 4 (22.22%), good in 7(38.89%), fair in 4 (22.22%) and poor in 3 (16.67%). In the anatomical reduction cases, 83.33%(5) cases'hip joint functional outcome was reached excellent or good; in the satisfied reduction cases, 40%(4) was reached fair or poor; the 2 cases which was unsatisfied reduction were all poor in the function.Conclusion: The acetabular fracture has the characteristic with a specific age, gender distribution, and so in the classification of fracture, the posterior wall fracture and the transverse fracture has the largest proportion; the satisfaction of the reduction closely related with the classification of fracture, the simple fracture significantly higher than the complicated ones; The surgical lag have some impact with the satisfaction of the reduction; The relationship between the satisfaction of the reduction and the final hip joint function was so close, more close to the anatomical reduction, more joint function there was.The second part: Biomechanical Study of Complicated Acetabular Fracture Treated With Internal Fixation Methods.Objective: In our research we built an acetabular fracture model which got transverse and posterior wall fracture. Our purpose of this study was to evaluate the stability of three kinds of internal fixation methods with biomechanical process.Materials and Methods: Five embalmed pelves which including the proximal femora were prepared for this study. Each of the five pelves was visually examined and then X-ray and CT scan and bone density determination to exclude the presence of hip pathology, then we got three pelves (six hemipelves). All muscles and ligaments including the hip joint capsule were dissected. Named the six hip joint specimen: 1L,1R,3L,3R,5L,5R. Then the 3L specimen was selected random to do the preliminary experiment. The acetabular fracture model was built with the medial roof arc less than 30 degree in the transverse fracture and a 50% defect of the articular surface of the posterior wall with the 50-degree arc in the posterior wall fracture. Firstly, we pasted the strain gages; then the data of the normal acetabulum(normal group, NG) was determined; at last, the fracture model was created and the data was determined also. The points which was determined were named A,B,C,D,A',B',C',D'. The different kinds of internal fixation methods were divided three groups: anterior wall with screw and posterior with plate group(SPG), both wall with plate group (PPG), anterior wall with plate and posterior wall with screw group(PSG). The test sequence was SPG-PPG-PSG. All the specimen simulated the single leg stance phase of gait in our study. The proportion that the data of the three fracture groups contrast with the normal group was used in the statistics. The specimen was loaded by 500N which was 5/6 of the weight. The loading velocity was 2mm/min.Results: Proportion of the strain value of each testing points in different internal fixation named SPG/NG,PPG/NG and PSG/NG,the SPG/NG: 2.70,1.47,2.18,1.59,1.67; the PPG/NG: 0.94,0.89,0.75,0.76,0.92; the PSG/NG: 1.06,1.05,1.32,1.52,1.22. Statistics showed a significant difference (P<0.05) between SPG/NG and PPG/NG, PPG/NG and PSG/NG, SPG/NG and PSG/NG.Conclusion: Through this study, we concluded that surgical treatment for transverse and posterior wall fracture of acetabulum was necessary. In the different kinds of internal fixation methods, the anterior wall with screw and posterior with plate group was worse than the other two groups, the anterior wall with plate and posterior wall with screw group was little better than the both wall with plate group.