Background An autologous bone-cage made from the spinous process and laminae might provide a stability in posterior lumbar interbody fusion (PLIF) close that of the traditional-cage made of polyetheretherketone (PEEK) or titanium. The biomechanical effect of autologous bone-cages on cage stability, stress, and strains, and on the facet contact force has not been fully described. This study aimed to verify whether autologous bone-cages can achieve similar performance as that of PEEK cages in PLIF by using a finite element analysis. Methods The finite element models of PLIF with an autologous bone-cage, a titanium cage, and a PEEK cage were constructed. The autologous bone-cage was compared with the titanium and PEEK cages. The mechanical properties of the autologous bone-cage were obtained through mechanical tests. The four motion modes were simulated. The range of motion (ROM), the stress in the cage-end plate interface, and the facet joint force (FJF) were compared. Results The ROM was increased at adjacent levels but decreased over 97% at the treated levels, and the intradiscal pressure at adjacent levels was increased under all conditions in all models. The FJF disappeared at treated levels and increased under extension, lateral bending, and lateral rotation in all models. The maximum stress of the cage-endplate interface was much lower in the autologous bone-cage model than those in the PEEK and titanium cage models. Conclusions In a finite model of PLIF, the autologous bone-cage model could achieve stability close that of traditional titanium or PEEK cages, reducing the risk of subsidence.

Objectives: This study compared the stability and clinical outcomes of modified pedicle screw-rod fixation (MPSRF) and anterior subcutaneous internal pelvic fixation (INFIX) for the treatment of anterior pelvic ring fractures using Tornetta and Matta grading system and finite element analyses.Methods: In a retrospective review of a consecutive patient series, 63 patients with Orthopaedic Trauma Association (OTA)/Arbeitsgemeinschaft für Osteosynthesefragen (AO) type B or C pelvic ring fractures were treated by MPRSF (n=30) or INFIX (n=33). The main outcome measure were Majeed score, incidence of complications and adverse outcomes, and fixation stability was evaluated by finite element analysis (FEA).Results: two groups did not differ in terms of injury severity score, OTA classification, cause of injury, and time to pelvic surgery. However, the MPSRF group had a higher satisfactory rate according to the Tornetta and Matta grading system than the INFIX group (73.33% vs 63.63%) as well as a higher Majeed score (81.5±10.4 vs 76.3±11.2), which was statistically significant at 6 months’ post-surgery. FEA showed that MPRSF was stiffer and more stable than INFIX and had a lower risk of implant failure.Conclusions: Both MPSRF and INFIX have acceptable biomechanical stability for the treatment of unstable pelvic anterior ring fractures. However, MPRSF has better fixation stability and lower risk of implant failure, which can lead to better clinical outcomes.

Objectives: This study compared the stability and clinical outcomes of modified pedicle screw-rod fixation (MPSRF) and anterior subcutaneous internal pelvic fixation (INFIX) for the treatment of anterior pelvic ring fractures. Methods: In a retrospective review of a consecutive patient series conducted in a level 1 trauma university hospital, 63 patients with Orthopaedic Trauma Association (OTA)/Arbeitsgemeinschaft für Osteosynthesefragen (AO) type B or C pelvic ring fractures were treated by MPRSF (n=30) or INFIX (n=33). The mean follow-up was 20 months. The main outcome measure was the incidence of complications and adverse outcomes, and fixation stability was evaluated by finite element analysis (FEA). Results: The 2 groups did not differ in terms of injury severity score, OTA classification, cause of injury, and time to pelvic surgery (P>0.05). However, the MPSRF group had a higher satisfactory rate according to the Tornetta and Matta grading system than the INFIX group (73.33% vs 63.63%) as well as a higher Majeed score (81.5±10.4 vs 76.3±11.2), which was statistically significant at 6 months’ post-surgery (P<0.001). FEA showed that MPRSF was stiffer and more stable than INFIX and had a lower risk of implant failure. Conclusions: Both MPSRF and INFIX have acceptable biomechanical stability for the treatment of unstable pelvic anterior ring fractures. However, MPRSF has better fixation stability and lower risk of implant failure, which can lead to better clinical outcomes.