2023, Vol. 27 ›› Issue (13): 1993-1998

Finite element analysis of hollow screw fixation for sacroiliac dislocation

Ye Haimin1, Zou Huachun2, Ding Linghua1, You Murong1   

Abstract: BACKGROUND: The sacroiliac joint plays an important role in stabilizing the pelvic ring, and its fracture or dislocation is challenging in surgery. Despite the continuous improvement of various screw placement methods, complications still exist such as screw misplacement and neurovascular injury. How to accurately place the screw into the sacrum, confirm the position of the screw, and ensure good stability is an urgent problem to be solved.
OBJECTIVE: To analyze biomechanical differences of two different combinations of screw fixation for sacroiliac dislocation by finite element analysis.
METHODS: Human corpse specimens were used as data. The three-dimensional finite element model of the whole pelvis was constructed by the ABAQUS finite element analysis system. Finite element models of sacroiliac dislocation were established, and two combinations of screw fixation were performed. One is that S1 was treated with 2 screws of 6.0 mm in diameter + S2 was treated with 1 screw of 6.0 mm in diameter (named as S12 + S21 group), and the other is that S1 was treated with a screw of 7.3 mm in diameter + S2 was treated with a screw of 6.0 mm in diameter (named as S11 + S21 group). A vertical force of 600 N was applied to the end plate on S1, and the maximum stress of the pelvis, the maximum stress of the screw (fatigue resistance), the overall displacement value of the model and the deformation of the screw were analyzed.
RESULTS AND CONCLUSION: (1) Pelvis fixation with screws in the two groups could effectively restore the conduction direction of pelvic biomechanics. The pelvic stress was less than the double-segment screw fixation stress, and the maximum stress was located on the cortical bone at the fracture end. (2) The maximum displacement of the normal pelvis was 0.080 9 mm and the maximum stress of the pelvis was 9.39 MPa. The maximum displacement of the pelvis was 0.097 8 mm and the maximum stress was 11.59 MPa in the S12+S21 group. The maximum displacement of the pelvis was 0.111 8 mm and the maximum stress was 13.51 MPa in the S11+S21 group. (3) The maximum stress was 12.35 MPa and the deformation was 0.081 11 mm in the S12+S21 group. The maximum stress was 14.53 MPa and the deformation was 0.088 2 mm in the S11+S21 group. (4) These results demonstrate that compared with the normal pelvis, there is no substantial change in the stability of the two fixation methods at two levels. The fatigue resistance of the screws with three screws is better than that with two screws in the two levels. Therefore, three-screw fixation is the first choice, but if the S1 double screw fixation is performed unconditionally, the best fixation method is to select one screw at both levels for fixation.
Key words: sacroiliac joint, sacroiliac dislocation, screw fixation, finite element analysis, pelvis