Hao Dingjun, MD, Xi'an Jiaotong University, Xi'an, China, presented the results of a prospective comparative study—Effect of Superior Adjacent Segment Degeneration after Lumbar Posterolateral Fusion Using Two Different Pedicle Screw Insertion Positions With Nine-Year Minimum Follow-Up [Yan L et al. Spine. 2014]—of patients with low-grade isthmic spondylolisthesis (IS), which assessed the effect of different pedicle screw insertion positions on adjacent segment degeneration (ASD).

From January 1999 to December 2003, 210 patients who underwent posterolateral fusion for low-grade IS were randomized to 2 groups according to different pedicle screw insertion positions. In group A (n = 102), the method by Du and Zhao [Chin J Spine Spinal Cord. 2001] was used to place the pedicle screw insertion. In group B (n = 108), the method by Magerl and colleagues [Clin Orthop Relat Res. 1984] was used, which needs more lateral and steeper angles for insertion.

Inclusion criteria included patients who were aged 18 to 55 years and had single-level IS (grade 1 or 2), persistent low back pain for > 6 months, and loss of quality of life with neurologic claudication. The follow-up period was at least 108 months. Patients were excluded from the study if they had undergone revision surgery, had ≥ grade 3 spondylolisthesis or concomitant scoliosis of > 15°, or had an implant removed during the follow-up period.

Of the 210 patients, 178 (84.7%) were available for at least a 9-year clinical and radiologic follow-up. Of these, 87 (85.3%) were patients in group A, and 91 (84.3%) were in group B.

Patient characteristics between the 2 groups were comparable. The majority of the patients were women in both groups (about 53%), with an average age of 46 years, a mean body mass index of about 24.3 kg/m², and a fusion level at L5-S1 (about 78%).

The study found significant differences (all P < .001) between the pre- and postoperative measures for all patients, using the Oswestry Disability Index (ODI) and the visual analog scale (VAS) for back and leg pain. In terms of postoperative ODI and VAS scores, no differences were found between the ASD and non-ASD groups nor between group A and group B. However, when the ODI scores were compared in terms of ASD, significantly more patients in group A had ASD compared with group B (28.6% vs 15.7%; P < .001).

According to Dr Dingjun, these findings show that the position of the pedicle screws during lumbar fusion surgery is closely related to superior ASD and that reducing the superior ASD can be done by inserting the pedicle screw in a position farther from the facet joint surface.