Finite Element Analysis and Transiliac‐Transsacral Screw Fixation for Posterior Pelvic Ring with Sacrum Dysplasia

Abstract

Objective Posterior pelvic ring sacroiliac screws are preferred by clinicians for their good biomechanical performance. However, there are few studies on mechanical analysis and intraoperative screw insertion of the dysplastic sacrum and sacroiliac screw. This study investigated the biomechanical performance of oblique sacroiliac screws (OSS) in S1 combined with transiliac‐transsacral screws (TTSs) in S2 for pelvic fracture or sacroiliac dislocation with dysplastic sacrum and evaluated the safety of screw placement assisted by the navigation template. Methods Six models were established, including one OSS fixation in the S2 segment, one transverse sacroiliac screw (TSS) fixation in the S2 segment, one TTS fixation in the S2 segment, one OSS fixation in the S1 and S2 segments, one OSS fixation in the S1 segment and one TSS fixation in the S2 segment, one OSS fixation in the S1 segment and one TTS fixation in the S2 segment. Then, finite element analysis (FEA) was performed. Twelve dysplastic sacrum patients with pelvis fracture or sacroiliac dislocation underwent OSS insertion in the S1 combined with TTS insertion in the S2 under the assistance of the patient‐specific locked navigation template. Grading and Matta scores were evaluated after surgery. Results In the one‐screw fixation group, the vertical displacements of the sacrum surface of S2 OSS, S2 TSS and S2 TTS were 1.23, 1.42, and 1.22 mm, respectively, and the maximum stress of screw were 139.45 MPa, 144.81 MPa, 126.14 MPa, respectively. In the two‐screw fixation group, the vertical displacements of the sacrum surface of the S1 OSS + S2 OSS, S1 OSS + S2 TSS and S1 OSS + S2 TTS were 0.91, 1.06, and 0.75 mm, respectively, and the maximum stress of screw were 149.26 MPa, 167.13 Pa, 136.76 MPa, respectively. Clinically, a total of 12 TTS and OSS were inserted under the assistance of navigation templates, with a surgical time of 55 ± 7.69 min, bleeding of 57.5 ± 18.15 ml and radiation times of 14.5 ± 4.95. One of the TTS and one of the OSS were grade 1, and the other screws were grade 0. The Matta scores of nine patients were excellent, and three patents were good. Conclusion OSS in the S1 combined with TTS in the S2 had the best mechanical stability in six models, and it is safe for screw insertion assisted by the patient‐specific locked navigation template.

Numerical study of pedicle screw construction and locking compression plate fixation in posterior pelvic ring injuries: Analyzed by finite element method

“…Various internal fixation methods have been described previously. [5][6][7][8] However, each technique has advantages and disadvantages, and no consensus has been reached regarding the optimal method for these injuries. The introduction of percutaneous minimal insertion of sacroiliac screws with limited soft tissue exposure is probably the most common method; however, this technique is technically demanding and limited by potential vascular and neural injuries.…”

“…A great variety of management methods have been investigated for posterior pelvic ring fixation, including external fixation, anterior sacroiliac joint plates, locking compression plates (LCP), transiliac sacral bars, percutaneous sacroiliac screws, and minimally invasive pedicle screw-rod fixators. [5][6][7][8] Currently, open-reduction internal fixation is associated with a high rate of wound complications. Close reduction with percutaneous sacroiliac screw fixation is one of the most popular techniques, [8] it has been regarded as a standard method for the definitive treatment of unstable posterior pelvic ring injuries.…”

A retrospective analysis of minimally invasive internal fixation versus nonoperative conservative management of pelvic ring fragility fractures and the elderly

“…Sacroiliac screw implantation assisted by robot and 3D-printed templates can significantly shorten operation time, reduce patient radiation exposure, and improve safety and accuracy [ 38 ]. Chao et al [ 39 ] used a patient-specific locked navigation template to treat pelvic fracture or sacroiliac dislocation with dysplastic sacrum. They demonstrated that the method was clinically safe using finite element analysis.…”