Assessment of Rod Material Types in Spine Surgery Outcomes: A Systematic Review

Lumbar spine fusion surgery is traditionally performed with rigid fixation. Because the rigidity is often supraphysiologic, semirigid rods were developed. To the best of our knowledge, a comprehensive evaluation of rod material type on surgical outcomes has yet to be conducted.

A systematic review based on PRISMA guidelines was conducted across 3 electronic databases. After examination for inclusion and exclusion criteria, data were extracted from the studies.

Seventeen studies, including 1399 patients, were included in this review. The mean rigid rod fusion rate is 92.2% and 95.5% for semirigid rods (P = 0.129). The mean improvement in back pain was 60.6% in rigid rods and 71.6% in semirigid rods. The improvement in leg pain was 81.9% and 77.2%, respectively. There were no differences in visual analog scale back pain score (P = 0.098), visual analog scale leg pain score (P = 0.136), or in functional improvement between rigid and semirigid rods (P = 0.143). There was no difference (P = 0.209) in the reoperation rate between rigid rods (13.1%) and semirigid rods (6.5%). There was a comparable incidence of adjacent segment disease (3%), screw fracture (1.7%), and wound infection (1.9%) between rod material types.

There is a moderate level of evidence supporting that surgical intervention results in high fusion rates regardless of rod material type. Surgical intervention improves back pain, leg pain, and function, with neither material type showing clear superiority. There are comparable rates of reoperation, development of adjacent segment disease, development of mechanical complications, and incidence of infection in both rigid and semirigid rods. Further studies regarding rod material type are warranted.