Retrospective review of a prospective multicenter database.
To develop a method to analyze sagittal alignment
, free of the influence of proximal junctional kyphosis
), and then compare PJK
patients using this method.
Summary of Background Data. PJK
after adult spinal deformity
) surgery remains problematic as it alters sagittal alignment
. The present study proposes a novel virtual modeling technique that attempts to eliminate the confounding effects of PJK
on postoperative spinal alignment.
A virtual spinal modeling technique was developed on a retrospective ASD
cohort of patients with multilevel spinal fusions to the pelvis with at least 2-year postoperative follow-up. The virtual postoperative alignment (VIRTUAL) was created from the postoperative alignment of the instrumented segments and the preoperative alignment of the unfused segments. VIRTUAL was validated by comparisons to actual 2-year postoperative alignment (REAL) in non-PJK
patients. Patients were then divided into two groups: PJK
based on the presence/absence of PJK
at 2 years postoperatively. PJK
patients were compared using VIRTUAL and REAL.
A total of 458 patients (78F, mean 57.9 yr) were analyzed. The validation of VIRTUAL versus
REAL demonstrated correlation coefficients greater than 0.7 for all measures except sagittal vertical axis (SVA; r
= 0.604). At 2 years, REAL alignment in PJK
patients demonstrated a smaller pelvic incidence minus lumbar lordosis and a larger thoracic kyphosis than non-PJK
patients, but similar SVA, T1 pelvic angle, and pelvic tilt. An analysis of VIRTUAL demonstrated that patients with PJK
had a smaller pelvic incidence minus lumbar lordosis, pelvic tilt, SVA, and T1 pelvic angle than non-PJK
This technique demonstrated strong correlations with actual postoperative alignment. Comparisons between REAL and VIRTUAL alignments revealed that postoperative PJK
may develop partially as a compensatory mechanism
to the overcorrection of sagittal deformities. Future research will evaluate the appropriate thresholds for deformity correction according to age and ASD
Level of Evidence: 3