Multi-Rod Constructs Can Increase the Incidence of Iliac Screw Loosening after Surgery for Adult Spinal Deformity

Abstract

Study Design A retrospective study. Purpose To investigate the incidence of iliac screw loosening with a two-rod vs. multi-rod construct and the effect on clinical and radiographic outcomes after surgery for adult spinal deformity (ASD). Overview of Literature Multi-rod construct is useful for preventing rod fracture in ASD surgery. However, limited information is available regarding the incidence of iliac screw loosening after corrective fusion surgery using a multi-rod construct. Methods Total 106 patients with ASD (24 men and 82 women; mean age, 68 years) who underwent corrective fusion surgery using bilateral iliac screws and were followed up for at least 1 year were reviewed. The following variables were compared between patients who underwent surgery with a two-rod and multi-rod construct: age, sex, bone mineral density (BMD), fusion level, high-grade osteotomy, L5/S interbody fusion, screw loosening (upper instrumented vertebra [UIV], S1, and iliac), rod fracture, proximal junctional kyphosis, spinopelvic parameters, and Oswestry Disability Index (ODI) score. We also compared patients with and without iliac screw loosening in the multi-rod construct group. Results Of the 106 patients, 55 underwent surgery with a conventional two-rod construct and 51 with a multi-rod construct (three rods in 16, four rods in 35). Iliac and UIV screw loosening was observed in 24 patients (21%) and 35 patients (33%), respectively. The multi-rod group showed significantly higher incidence of iliac and UIV screw loosening and lower incidence of rod fracture. Patients with iliac screw loosening had a lower BMD than those without screw loosening; however, no significant differences were observed in the spinopelvic parameters or the ODI score. Conclusions The use of multi-rod constructs led to a higher incidence of junctional screw loosening than the use of conventional two-rod constructs, especially in patients with osteoporosis. Iliac screw loosening did not affect sagittal alignment or clinical outcome in the short term.

Characteristics and Risk Factors of Rod Fracture Following Adult Spinal Deformity Surgery: A Systematic Review and Meta-Analysis

“…Several papers have proposed methods to reduce RF. [18][19][20][21] Gupta et al 19 recommended the 4-rod technique for the PSO site. The point of maximum stress on the body is at its apex, where the spine becomes unstable by osteotomy.…”

“…This technique also helps to significantly reduce the potential for premature RF due to biomechanical damage of the rod. 20 Banno et al 18 reported that multirod structure use improved stability compared to use of the standard 2-rod structure, which was effective in preventing implant failure and symptomatic pseudarthrosis.…”

A Systematic Review of Treatment Strategies for the Prevention of Junctional Complications After Long-Segment Fusions in the Osteoporotic Spine

“…Banno et al 24 compared multirod constructs versus standard 2-rod constructs in an elderly, osteopenic population undergoing ASD surgery. Patients with multirod constructs did have a higher incidence of iliac and UIV screw loosening, but a significantly lower incidence of rod fracture.…”

Influence of double rods and interbody cages on quasistatic range of motion of the spine after lumbopelvic instrumentation

“…Combining lumbosacral and pelvic instrumentation with interbody cages represents an additional strategy to prevent mechanical complications [25,26]. Furthermore, Banno et al [27] investigated the incidence of proximal pedicle and iliac screw loosening with 2-rod versus 4-rod constructs. A radiologic halo developed around screws in 21% of patients with 2-rod versus 33% after 4-rod instrumentation.…”