Editorial: Skipped pedicle screws

Abstract

Hwang et al.2 introduce a topic of interest that is potentially relevant for all surgeons who perform surgery in patients with spinal deformity. Their investigation is essentially a proof-of-concept study of a technique for reducing the number of pedicle screws used in deformity surgery by skipping every other level on the concave side and using only a few screws on the convex side of the curve. While interesting, any conclusions drawn must be limited to the study of patients with adolescent idiopathic scoliosis (AIS) because of the superior bone quality and flexible curves in that population. Other patients with spinal deformity, such as those with degenerative scoliosis, a population with poor bone quality,3,6 may not respond as well. This shortcoming is acknowledged by the authors, who defer the use of this technique in patients with large deformities or stiff curves, in which more force will be necessary to achieve and hold correction. Quan and Gibson4 quantified the correction of Lenke Type 1 curves based on pedicle screw density, which they defined as the average number of pedicle screws/ level across the construct (that is, density = 1 signifies 1 pedicle screw/level on average). They found no difference in preoperative or postoperative curve magnitude regardless of whether screws were placed at every pedicle (density 1.75–2) or alternate pedicles (density 1–1.25). The strengths of this study were the inclusion of a control group and a more homogeneous patient population with solely Lenke Type 1 curves. However, the number of patients was smaller, with 49 patients divided among 4 groups based on pedicle screw density. Deviren et al.1 investigated the placement of pedicle screws in alternate pedicles versus every pedicle in a human cadaveric model. Increasing the number of pedicle screws resulted in incrementally greater stiffness in flexion/extension, lateral bending, and rotational moments, but the differences between the alternate and every pedicle strategy were not significant. Findings in this study, along with the limited clinical results from the studies of Quan and Gibson4 and Hwang et al.,2 suggest that although this construct trends toward inferior biomechanics, the difference is not clinically significant for achieving curve correction and fusion in patients with moderate AIS. The potential for cost savings has become and will continue to be an important topic in spinal surgery, and the authors should be commended in this regard. Given the high cost of spinal instrumentation, the field of spine surgery faces a particular challenge in a health care environment that is increasingly focused on demonstrating incremental cost-effectiveness. Roach et al.5 recently documented a 100% increase in the inflation-adjusted cost of treating AIS over a 10-year period, which was due almost entirely to the cost of pedicle screws. In comparison, the cost of treating a femur fracture over the same time period increased only 7%. Surgical strategies such as those described by Hwang et al.2 highlight one aspect of treatment cost that might be controlled by the surgeon. The surgical technique discussed may prove to be a useful strategy for patients with good bone quality, and the potential benefits of reduced costs, operative times, and blood loss warrant further investigation. To be more widely applicable to deformity surgery, this technique will first have to be vetted in other patient populations in which fewer fixation points and weaker bone may present greater challenges than in the AIS population.