Biomechanical Study of Posterior Pelvic Fixations in Vertically Unstable Sacral Fractures: An Alternative to Triangular Osteosynthesis

Abstract

Study DesignBiomechanical study.PurposeTo investigate the relative stiffness of a new posterior pelvic fixation for unstable vertical fractures of the sacrum.Overview of LiteratureThe reported operative fixation techniques for vertical sacral fractures include iliosacral screw, sacral bar fixations, transiliac plating, and local plate osteosynthesis. Clinical as well as biomechanical studies have demonstrated that these conventional techniques are insufficient to stabilize the vertically unstable sacral fractures.MethodsTo simulate a vertically unstable fractured sacrum, 12 synthetic pelvic models were prepared. In each model, a 5-mm gap was created through the left transforaminal zone (Denis zone II). The pubic symphysis was completely separated and then stabilized using a 3.5-mm reconstruction plate. Four each of the unstable pelvic models were then fixed with two iliosacral screws, a tension band plate, or a transiliac fixation plus one iliosacral screw. The left hemipelvis of these specimens was docked to a rigid base plate and loaded on an S1 endplate by using the Zwick Roell z010 material testing machine. Then, the vertical displacement and coronal tilt of the right hemipelves and the applied force were measured.ResultsThe transiliac fixation plus one iliosacral screw constructions could withstand a force at 5 mm of vertical displacement greater than the two iliosacral screw constructions (p=0.012) and the tension band plate constructions (p=0.003). The tension band plate constructions could withstand a force at 5° of coronal tilt less than the two iliosacral screw constructions (p=0.027) and the transiliac fixation plus one iliosacral screw constructions (p=0.049).ConclusionsThis study proposes the use of transiliac fixation in addition to an iliosacral screw to stabilize vertically unstable sacral fractures. Our biomechanical data demonstrated the superiority of adding transiliac fixation to withstand vertical displacement forces.

S2 Alar Iliac Screw and S1 Pedicle Screw Fixation for the Treatment of Sacral Fractures : A Finite Element Study

“…According to the mean RD values, the overall stability of the ve internal xation methods in the FE models, in descending order are: S2AI-S1, S2AI-CS1, SIS, LPF, and TIFI. Considering that unilateral LPF and TIFI are insu cient for stability of the posterior pelvic ring, it is considered necessary to add a sacroiliac screw to unilateral LPF or TIFI to enhance stability, as demonstrated in previous studies [29,34]. The RD of different points reveals that a fracture is more stable the closer it is to a screw (S2AI screw/Sacroiliac screw).…”

A systematic review of the transiliac internal fixator (TIFI) for posterior pelvic injuries

“…Therefore, the authors did not recommend TIFI for the treatment of IS dislocation. The most recent test series was conducted by Chaiyamongkol et al [ 33 ]. The 12 synthetic pelvic models had unilateral 5 mm gaps at the left transforaminal zone, and the pubic symphyses were separated and stabilized with plates.…”

“… Authors Test models Type of sacral fracture Vertical load Summary/Conclusion Dienstknecht et al [ 29 ] 6 freshly frozen human pelvis 6 unilateral transforaminal 3 cycles of 70% of the former body mass were performed max load not reported TIFI compared to two IS screws were tested TIFI was not inferior compared to IS screws Salasek et al [ 30 ] Computed image finite element Unilateral transforaminal 250–500 N TIFI has enough stiffness for unstable transforaminal fractures TIFI is superior compared to two IS screws Shinohara et al [ 31 ] 8 synthetic pelvic models 8 unilateral transforaminal Max. load 1057 N Mean load for a 5 mm gap: 438 N Double (dual) TIFI with crosslinks were used TIFI was superior compared to plate Vigdorchik et al [ 32 ] 6 synthetic pelvic models 3 unilateral transforaminal 3 IS joint dislocation 5 cycles; static load 10 mm/sec Mean load for a 7 mm gap: 81 N (sacral fracture) Mean load for a 7 mm gap: 71 N (IS dislocation) Sacral fracture: TIFI was inferior compared to TIFI plus IS screw Sacral fracture: TIFI was equal to IS screw alone IS dislocation: TIFI was the weakest construct Chaiyamongkol et al [ 33 ] 12 synthetic pelvic models …”

S2-alar-iliac screw and S1 pedicle screw fixation for the treatment of non-osteoporotic sacral fractures: a finite element study

“…According to the mean RD values, the overall stability of the five internal fixation methods in the FE models in descending order was: S2AI-S1, S2AI-CS1, SIS, LPF and TIFI. Considering that unilateral LPF and TIFI are insufficient for stability of the posterior pelvic ring, the addition of a sacroiliac screw to unilateral LFP or TIFI to enhance stability is considered necessary, as demonstrated in previous studies [ 3 , 33 ]. The RD of different points reveals that a fracture is stabler the closer it is to a screw (S2AI screw/Sacroiliac screw).…”