Analysis of Measures Against Mechanical Complications in Circumferential Minimally Invasive Surgery for Adult Spinal Deformity

Aim: We evaluated the reduction of mechanical complications (MCs) in circumferential minimally invasive spinal surgery (c-MIS) to treat adult spinal deformity (ASD) using lateral lumbar interbody fusion and a percutaneous pedicle screw. Methods: Patients with ASD who underwent c-MIS with a follow-up period of > 24 months were enrolled. Groups were as follows: c-MIS using 5.5 mm rods (P group), c-MIS using a 5.5 mm single rod with cement augmentations in the upper instrumented vertebra (UIV)/UIV + 1 (B group), c-MIS using 6 mm rods (6P group), and multi-rod c-MIS (M group). Terminal rod contour was optimized to prevent proximal junctional kyphosis (PJK) in the P, 6P, and M groups. Patients were divided into an MC group, consisting of 68 patients with MCs, and a non-MC group, consisting of 78 patients without MCs. We examined various spinopelvic- and implant-related parameters between the groups. Results: Overall, 146 patients with ASD who underwent c-MIS were included. The incidence of PJK was significantly lower in the P and M groups than in the B group, and rod fracture was significantly lower in the M group than in the B and P groups. In the MC group, preoperative PT, postoperative PI-LL, and PSA were significantly larger than those in the non-MC group. Use of the 5.5 mm single rod and postoperative PI-LL were significant risk factors for MCs. Conclusion: The complication incidence decreased with improvements in surgical techniques and measures. Use of the 5.5 mm single rod and postoperative PI-LL were significant risk factors for MCs.