Supplemental S1 fixation for type C pelvic ring injuries: biomechanical study of a long iliosacral versus a transsacral screw

Abstract

BackgroundA single iliosacral screw placed into the S1 vertebral body has been shown to be clinically unreliable for certain type C pelvic ring injuries. Insertion of a second supplemental iliosacral screw into the S1 or S2 vertebral body has been widely used. However, clinical fixation failures have been reported using this technique, and a supplemental long iliosacral or transsacral screw has been used. The purpose of this study was to compare the biomechanical effect of a supplemental S1 long iliosacral screw versus a transsacral screw in an unstable type C vertically oriented sacral fracture model.Materials and methodsA type C pelvic ring injury was created in ten osteopenic/osteoporotic cadaver pelves by performing vertical osteotomies through zone 2 of the sacrum and the ipsilateral pubic rami. The sacrum was reduced maintaining a 2-mm fracture gap to simulate a closed-reduction model. All specimens were fixed using one 7.0-mm iliosacral screw into the S1 body. A supplemental long iliosacral screw was placed into the S1 body in five specimens. A supplemental transsacral S1 screw was placed in the other five. Each pelvis underwent 100,000 cycles at 250 N, followed by loading to failure. Vertical displacements at 25,000, 50,000, 75,000, and 100,000 cycles and failure force were recorded.ResultsVertical displacement increased significantly (p < 0.05) within each group with each increase in the number of cycles. However, there was no statistically significant difference between groups in displacement or load to failure.ConclusionsAlthough intuitively a transsacral screw may seem to be better than a long iliosacral screw in conveying additional stability to an unstable sacral fracture fixation construct, we were not able to identify any biomechanical advantage of one method over the other.Level of evidenceDoes not apply—biomechanical study.

The three-dimensional bone mass distribution of the posterior pelvic ring and its key role in transsacral screw placement

“…SD = standard deviation; HU = Hounsfield Units; y = years. www.nature.com/scientificreports www.nature.com/scientificreports/ biomechanical study seems to support our conclusion that there is a wide zone of sufficient bone quality in the vertebral bodies, which provides purchase similar to that of the cortex of the contralateral sacrum 27 . Some surgeons avoid fixation of the contralateral, uninjured sacroiliac joint in order to prevent pain, stiffness and delays in rehabilitation.…”

“…In a biomechanical cadaver study, the combination of a locked transsacral screw and one iliosacral screw showed better results than two "standard" iliosacral screws 26 , suggesting that the highest stability can be achieved when the thread passes through the contralateral sacroiliac joint and the os ilium cortex. However, in their biomechanical cadaver study, Salari et al 27 found no significant difference in stability between transsacral fixation and a long iliosacral screw, where this long screw did not perforate the contralateral sacroiliac joint. The latter Table 1.…”

Percutaneous Sacroiliac Screw Placement

“…Currently, the conventional freehand fluoroscopy technique is very common for intraoperative visualization realized via image intensifier, which is possible in only one plane at a time, meanwhile requiring complex hand-eye coordination. [ 10 11 12 ] As such, it is a highly demanding and challenging operative technique. Recently, computer-assisted orthopedic surgery, which potentially increases the accuracy and efficiency of percutaneous targeting, has utilized image navigation systems and purpose-built robots.…”

Feasibility Study of Transfacet Sacroiliac Screw Fixation Based on Mimics

“…Sacroiliac screw (SIS) has become an effective internal xation method for sacral fracture and sacroiliac joint dislocation [1,2]. The classic SIS internal xation is placed percutaneously, which passes from the posterolateral side of the ilium through the sacroiliac joint into the vertebral body of the sacrum [3,4].…”