Abstract
Introduction: Proximal junctional kyphosis (PJK) is a common mechanical complication which has a potential risk of revision surgery in adult spinal deformity (ASD) surgery. Three different types of upper instrumented vertebra (UIV) anchors were changed to prevent PJK and proximal junctional vertebral fractures (PJVF). The purpose of this study was to compare the incidence of PJVF in ASD surgery among the three types of UIV anchors.
Methods: Sixty ASD patients with minimum 2-year follow-up were recruited in this study. We divided the patients into three groups according to UIV instruments; pedicle screw (PS) group (n = 15 patients; mean age at surgery, 69.4 years; mean follow-up duration, 78 months), hook group (n = 25, 71.5 years, 59.0 months), and hook-short PS (sPS) group (n = 20, 69.1 years, 13.9 months). We evaluated the radiographic parameters before surgery, one week after surgery, and final follow-up (FFU), and also assessed surgical outcomes using Japanese version SRS-22 questionnaire (SRS-22). We compared the parameters and incidence of PJVF among the three groups. PJVF was defined as the presence of UIV or UIV±1 fracture in this study.
Results: The incidence of PJVF was 40% (6/15) in the PS grp, 24% (7/25) in the Hook group, and 10% (2/20) in the hook-sPS group. The statistical analysis did not show any significant difference in incidence of PJVF between the three groups (P = 0.1). Comparative analysis of the radiographic parameters among the three groups demonstrated that preoperative pelvic incidence-lumbar lordosis, Pelvic tilt, and thoracolumbar kyphosis (TLK) at FFU differ significantly (P < 0.05); proximal junctional angle (PJA) and TLK in the hook-sPS group at FFU were significantly lower than the hook group (P < 0.05).
Conclusions: Our study shows that hooks at UIV and short PS at UIV+1 as UIV anchor may prevent PJVF. This UIV construct is considered to match the concept of soft-landing for thoraco-pelvic fixation in the ASD patients. Further biomechanical study is necessary to clarify our results.
