Low pelvic incidence is associated with proximal junctional kyphosis in patients treated with growing rods

Study Design. Retrospective review of a prospectively collected pediatric orthopedic spine database. Objective. To investigate whether pelvic incidence (PI) changes during growing rod treatment and to report the effects of PI, if any, on complications during treatment. Summary of Background Data. Growing rods have been demonstrated to correct spinal deformity in early onset scoliosis while allowing for spinal growth. There has been little investigation into the potential effects, if any, of abnormal PI on complications, especially proximal junctional kyphosis (PJK). Methods. We retrospectively reviewed clinical and surgical data from our prospectively collected pediatric orthopedic spine database. Our final cohort of 48 patients had at least one lateral radiograph throughout the course of treatment containing the femoral heads and sacral endplate, and a minimum follow-up of 2 years. Defined failures were identified prospectively. Radiographs were measured for PI and development of PJK. Results. Mean age at initial treatment was 6.9 years (range 2.8-10.8 yr), with 35 females and 13 males. The mean length of follow-up was 8.1 years (range 2.0-22.1 yr). No statistical change in PI was observed throughout this study (P=0.655). Development of any failure as well as total number of failures was associated with younger age at initial treatment (P<0.0005 for both). Development of PJK was associated with younger age at initial treatment (P=0.030), female sex (P=0.002), and lower mean PI (P=0.042). Conclusion. PI remains constant throughout growth and the course of treatment with growing rods. Low PI was associated with increased PJK. When using growing rods in early onset scoliosis patients with decreased PI, increased attention should be paid to sagittal plane balance in an attempt to avoid PJK.