2021 Volume 12 Issue 9 Pages 1135-1142
Introduction: Circumferential minimally invasive surgery (c-MIS) that employs lateral interbody fusion (LIF) and percutaneous pedicle screw (PPS) for adult spinal deformity (ASD) is becoming increasingly popular. However, studies that have thoroughly evaluated bone fusion rate and morphology, including those of the thoracic spine without bone grafting, are few. We examined the bone fusion process at the thoracic and lumbosacral levels of patients with ASD who underwent c-MIS using LIF and PPS.
Methods: This retrospective study included 60 patients with ASD who underwent corrective surgery using LIF and PPS and were followed up for >24 months after surgery. Patients with anterior longitudinal ligament rupture were excluded. The average age and follow-up period of the patients were 73.5 years and 35.5 months, respectively. The fixation range was from the lower thoracic spine to the pelvis in all cases. Bone grafting was not performed in the thoracic spine. The bone fusion rate and morphology were examined for 191 thoracic, 240 lumbar, and 60 lumbosacral vertebrae. Moreover, implant-associated complications in the thoracic spine without bone grafting were examined and compared between the union and nonunion groups. The bone fusion morphology was classified into the bridging (type B), interbody fusion (type I), and posterior fusion (type P) types. The conditions of the preoperative disc/vertebral body were classified as follows: no degeneration (type N), diffuse idiopathic skeletal hyperostosis (DISH) (type D), and pre-DISH (type pre-D), which tends to form bridging.
Results: The bone fusion rate at the thoracic level 2 years postoperatively was 52%; 17% of these patients had bone union preoperatively. The bone fusion rate at the lumbar and lumbosacral levels was 85%. Type B was the most common type of bone fusion. The preoperative disc/vertebral body conditions were type N in 36 cases, type D in 15 cases, and type pre-D in 9 cases, and the bone fusion rates were 27%, 93%, and 78%, respectively. The incidence of implant-associated complications in the thoracic spine was 38%. The proportion of male patients and type D cases were significantly higher and the proportion of type N cases was significantly lower in patients with union in the thoracic spine than in those without. Screw loosening was significantly more common in the nonunion group; however, no significant difference was observed in the incidence rate of postoperative implant-related complications between the two groups.
Conclusions: Even without bone grafting, postoperative incidence of implant-related complications remains unaffected.
