An early experience of lumbopelvic fixation techniques at Alexandria University
Authors: Sorour Islam , Elbary Mohamed Abd , Rabie Ahmed , Elhabashy Abdelrahman Magdy 
Published: June 2021

Abstract
Background
The aim of lumbopelvic fixation is to obtain a solid fusion across the lumbosacral junction. There are many indications for lumbopelvic fixation, namely, spinal deformity in cases requiring long segment fusion, pelvic obliquity, pseudarthrosis at the lumbosacral junction, infection or osteolytic tumors, and pathologic fractures. The classical iliac screws should be contained within the iliac bone but have some disadvantages: excessive soft tissue dissection needed for accurate insertion, screw prominence with patient discomfort, and usually, a side connector is needed to connect the iliac screws to the rest of the construct. Lumbopelvic fixation by insertion of S2 alar-iliac (S2AI) screws was recently described to overcome these disadvantages. In this study, the authors present the initial results for the evaluation of lumbopelvic fixation through the insertion of S2AI screws in 19 consecutive patients operated in the neurosurgery department at Alexandria University.

Objective
The aim of the study was to evaluate the efficacy and complications of lumbopelvic fixation through the use of S2 alar-iliac screws.

Methods
The authors conducted a retrospective cohort study of data collected from the database of patients who underwent lumbopelvic fixation through the insertion of S2AI screws from 2016 to 2019 at a single institution.

Results
There were 19 patients indicated for lumbopelvic fixation, operated by modern instrumentation systems using lumbar pedicle screws and S2 alar-iliac screws. There were 14 females and 5 males. The mean age at the time of the operation was 38.6 ± 19.4 years with a range from 11 to 65 years. There was a total of 37 S2AI screws, screw diameter was 7mm in all cases regardless of age, and the length of the screws ranged from 50 mm in a young female patient (11 years) to 90 mm in an old male patient (60 years). Two screws were inserted per patient except in one case with congenital scoliosis due to the bad bone quality and the multiple iatrogenic wrong paths. Postoperative VAS score for back pain was greatly improved in all patients after the first 6 months of follow-up from 8 ± 1.5 to 3.5 ± 1.2 (paired t-test = 11.182, P<0.001). All patients had a good spinal range of motion to maintain normal daily activities without any significant restrictions after the first 3 months of follow-up. Immediate postoperative radiological follow-up had revealed 2 cases of posterior pelvic breaches and one case with anterior pelvic breach but without clinical manifestations with no need for revision. Two cases of unilateral screw breakout were observed after the first 6 months of follow-up. Removal of screws after the first 6 months was done in one patient with spondylodiscitis due to the unresolved infection and screw pullout.

Conclusion
The insertion of S2AI screws is an effective technique for lumbopelvic fixation with a relatively low rate of complications. Pelvic breaches are the commonest complications encountered during the insertion of S2AI screws, although no significant clinical morbidities were reported.