Pelvic antropometric measurement in 3D CT for placement of two unilateral iliosacral S1 - 7.3 mm screws

Comparison of the operation safety and biomechanical stability of sacral alar-iliac vs. sacroiliac screws in the fixation of sacroiliac joint in simulated models of low bone density

BACKGROUND

Sacral alar-iliac screws (SAISs) have been used for sacroiliac joint and are superiority to traditional sacroiliac screws (SISs) in patients with low bone density. The aim of this study was to investigate the operation safety and biomechanical stability of the SIS, transsacral-transiliac screw (TSTIS), S1AIS and S2AIS in the treatment of sacroiliac joint in simulated models of low bone density.

METHODS

CT data from 80 normal pelvic structures were employed to measure the anatomical parameters, including the safety zones of the S1AIS and S2AIS at the insertion point and the trajectory lengths of the SIS, TSTIS, S1AIS and S2AIS. Sixteen synthetic pelvises with simulated osteoporotic bone structure were used to simulate type C Tile lesions and divided into 4 groups with an anterior plate and posterior fixation using one of the following: 1) one SIS on each side, 2) one TSTIS fixing both sides, 3) one S1AIS on each side, or 4) one S2AIS on each side. The stiffness and maximum load of the specimens were analyzed using a biomechanical machine under vertical loading.

RESULTS

The safety zone of S1AIS was larger than that of S2AIS (p < 0.05). The TSTIS had the largest trajectory length, followed by the S1AIS and S2AIS, and the SIS had the smallest trajectory length (p < 0.05). However, the lengths of the TSTIS (26.1 ± 1.7 mm) and SIS (27.8 ± 1.8 mm) trajectories on the short side (the iliac side) were smaller than those of S1AIS (40.4 ± 3.8 mm) and S2AIS (39.1 ± 3.8 mm), thus indicating significant differences (p < 0.05). The stiffness and maximum load of S1AIS and S2AIS were similar and the greatest, followed by TSTIS and SIS (p < 0.05).

CONCLUSION

The stability of S1AIS and S2AIS is similar, both stronger than that of SIS and TSTIS, which have shorter lengths of the screw trajectories on the ilium side. However, the safety zone of S2AIS at the insertion point is smaller than that of S1AIS. Therefore, considering both safety and stability, S1AIS is the preferred choice for fixation of sacroiliac joint dislocation in simulated models of low bone density.

Bony Sacral Volume after Sacro-Iliac Screw Fixation of Pelvic Fractures Is Dependent on Reduction of the Anterior Pelvic Ring

Pelvic ring injuries are uncommon but serious injuries. Percutaneous sacro-iliac screw fixation (SSF) is the standard treatment for posterior stabilization of pelvic fractures. Compression forces of the SSF might cause deformity of the sacrum and the pelvic ring. The aim of this radio-volumetric study is to evaluate the morphometry of the sacrum and pelvic ring in SSF for posterior pelvic fractures. (1) Methods: We conducted a radio-volumetric study measuring the bony sacral volume before and after SSF for a pelvic fracture based on a three-dimensional reconstruction of the pre- and postoperative computed tomography scan of 19 patients with a C-type pelvic fracture. In addition to the bony sacral volume, we assessed the pelvic deformity and the load bearing axis. We compared the results of patients without anterior stabilization (Group A) to patients who had additional ORIF of the anterior pelvic ring. (2) Results: Median age of the patients was 41.2 years (±17.8). All patients received percutaneous SSF with partially threaded 7.3 mm screws. The sacral volume decreased from 202.9 to 194.3 cm3 in group A (non-operative treatment anterior, n = 10) and an increase of sacral volume from 229.8 to 250.4 cm3 in group B (anterior ORIF; n = 9). Evaluation of the pelvic deformity also reflected this trend by a decrease of the ipsilateral load-bearing angle in group A (37.0° to 36.4°) and an increase of this angle in group B (36.3 to 39.9°). (3) Conclusions: Bony sacral volume and pelvic deformity after sacro-iliac screw fixation in pelvic fractures depend on treatment of the anterior pelvic ring. Reduction and fixation of the anterior fracture shows an increase of the bony sacral volume and the load bearing angle leading to a closer to normal reconstruction of the pelvic anatomy.

Percutaneous two unilateral iliosacral S1 screw fixation for pelvic ring injuries: a retrospective review of 38 patients

Purpose

Percutaneous iliosacral (IS) screw fixation for pelvic ring injuries is a minimally invasive technique that reduces the amount of blood loss and shortens the procedure time. Moreover, two unilateral IS S1 screws exhibit superior stability to a single IS screw and are also safer for neurological injuries than an S2 screw. Therefore, this study aimed to evaluate fixation using percutaneous two unilateral IS S1 screws for pelvic ring injuries and its subsequent clinical outcomes.

Methods

We retrospectively reviewed 38 patients who underwent percutaneous two unilateral IS S1 screw fixation for pelvic ring injuries. The procedure time, blood loss, achievement of bone union, radiological outcomes (Matta and Tornetta grade), and postoperative complications were evaluated.

Results

The mean procedure time, hemoglobin loss, bone union rate, and time to union were 40.1 minutes (range, 18-102 minutes), 0.6 g/dL (range, 0.3-1.0 g/dL), 100%, and 153.2 days (range, 61-327 days), respectively. The Matta and Tornetta grades were excellent, good, and fair in 24 (63.1%), 11 (28.9%), and three patients (7.9%), respectively, and the postoperative complications were S1 screw loosening, widening of the symphysis pubis (2.3 and 2.5 mm), lumbosacral plexopathy, and S1 radiculopathy in one (2.6%), two (5.3%), one (2.6%), and one patient (2.6%), respectively. However, all neurological complications recovered spontaneously.

Conclusions

Percutaneous two unilateral IS S1 screw fixation was useful for treating pelvic ring injuries. In particular, it involved a short procedure time with little blood loss and also led to 100% bone union and good radiological outcomes.