Еffectiveness of Four-Rod Fixation for Pedicle Subtraction Spinal Osteotomy

Abstract

Introduction.Pedicle subtraction osteotomy (PSO) provides for significant segmental correction of the sagittalbalance of the spine. At the same time, the technique is associated with a high risk of complications, with rod fracture at the osteotomy site being the most common. The purposeof this study — to assess the effectiveness of four-rod fixation compared to literature data on standardtwo-rod fixation in patients undergoing PSO. Materials and Methods.The study is a retrospective analysis of 47 consecutive patients with rigid spinaldeformities, who underwent pedicle subtraction osteotomy at the lumbar level. The average age of the patients (33 females and 14 males) was 59.7 years. In all cases spinal fixation carried out using a four-rod construct with additional short rods at the osteotomy site. The minimal postoperative follow-up was 2 years. A detailed analysis of the radiographic data was carried out with calculation of the global sagittal balance and spinopelvic parameters. A detailed assessment of complications in the early and late postoperative periods was also performed. After an exhaustive review of literature, a comparative analysis was made of the four-rod fixation technique with current literature data on the frequency of complications (in particular, rod fractures in the osteotomy zone) after two-rod fixation. Results.In all cases the osteotomy was performed at one level, most often at L3 (49%). The average length offixation was 9.8 segments. The average angle of segmental correction was 27.1°. In most cases, it was possible to achieve adequate correction of spinopelvic parameters. Among complications, bone resorption around screws was most prevalent (23.4% of cases). Proximal junctional kyphosis occurred in 12.8% of cases, neurologic deficit — in 14.9% of cases, infectious complications — in 10.6% cases. Asymptomatic pseudarthrosis, confirmed by CT data, was observed in 12.8% of patients. Rod fracture at the PSO site and adjacent segments was not observed in any of the cases. Rod fractures of other localization were observed in 10.6% of patients. Conclusion. According to the literature, the frequency of rod fractures at the osteotomy site is the most frequentcomplication of PSO. The results of this study showed that four-rod fixation in PSO significantly reduces the incidence of pseudarthrosis and rod fracture rate in the long-term follow-up and provides greater control over the process of osteotomy closure.