Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 12: pedicle screw fixation as an adjunct to posterolateral fusion for low-back pain

Abstract

This review focused on an examination of the literature on the surgical treatment of low-back pain in patients with DDD or low-grade degenerative spondylolisthesis treated with PLF, with or without the use of pedicle screw fixation. All Class I and the majority of Class II and Class III medical evidence on this topic indicates that the addition of pedicle screw fixation to PLF increases fusion success rates when assessed based on plain x-ray films with dynamic imaging. Although there does appear to be a positive relationship between radiographic fusion and clinical outcome, no convincing correlation has been demonstrated. Although several reports suggest that clinical outcomes are improved with the addition of pedicle screw fixation, there are conflicting findings from similarly classified evidence sources (primarily Class II and III). Furthermore, the largest contemporary randomized controlled study on this topic failed to demonstrate a significant beneficial effect for the use of pedicle screw fixation in patients treated with PLF for chronic low-back pain. This absence of proof should not, however, be interpreted as a proof of absence. For example, in this same study, patient satisfaction scores improved from approximately 60% to approximately 70% with the addition of pedicle screw fixation. This difference in outcome may be clinically relevant. Similarly, the improvement in ODI scores was 40% greater in the group of patients treated with pedicle screw fixation compared with those treated with PLF alone. If an analysis to determine the sample size necessary to ensure a power of 0.8 (or an 80% chance of detecting a significant effect) in a study in which the good outcome rate is 60% in the control group and 70% in the treatment group is performed, approximately 355 patients would be needed in each treatment group (http://department.obg.cuhk.edu.hk). Alternatively, if a similar analysis is performed using the differential scores obtained in the ODI measurements reported in the paper by Fritzell, et al., approximately 225 patients would be needed per treatment group (http://calculators.stat.ucla.edu/powercalc). Although Fritzell, et al., did not detect a significant benefit associated with the use of pedicle screw fixation as an adjunct to PLF, their sample size severely limited the power of their study to detect such a benefit. All studies reviewed suffer from similar lack of power. Therefore, no definitive statement regarding the efficacy of pedicle screw fixation as a means to improve functional outcomes in patients undergoing PLF for chronic low-back pain can be made. There appears to be consistent evidence suggesting that pedicle screw fixation increases the costs and complication rate of PLF. It is recommended, therefore, that the use of pedicle screw fixation as a supplement to PLF be reserved for those patients in whom there is an increased risk of nonunion when treated with PLF. High-risk patients include, but are not limited to patients who smoke, who are undergoing revision surgery, or who suffer systemic diseases known to be associated with poor bone healing.