RT Journal Article
SR Electronic
T1 Comparing the Upper Instrumented Vertebrae Tilt Angle vs Screw Angle in the Development of Proximal Junction Kyphosis After Adult Spinal Deformity Surgery: Which Matters More?
JF International Journal of Spine Surgery
JO Int J Spine Surg
FD International Society for the Advancement of Spine Surgery
SP 8607
DO 10.14444/8607
A1 Keyan Peterson
A1 Hani Chanbour
A1 Michael Longo
A1 Jeffrey W. Chen
A1 Soren Jonzzon
A1 Steven G. Roth
A1 Jacquelyn S. Pennings
A1 Amir M. Abtahi
A1 Byron F. Stephens
A1 Scott L. Zuckerman
YR 2024
UL https://www.ijssurgery.com/content/early/2024/06/13/8607.abstract
AB Background We sought to determine which aspect of the upper instrumented vertebrae (UIV)—tilt angle or screw angle—was more strongly associated with: (1) proximal junctional kyphosis/failure (PJK/F), (2) other mechanical complications and reoperations, and (3) patient-reported outcome measures (PROMs).Methods A single-institution, retrospective cohort study was undertaken for patients undergoing adult spinal deformity (ASD) surgery from 2011 to 2017. Only patients with UIV at T7 or below were included. The primary exposure variables were UIV tilt angle (the angle of the UIV inferior endplate and the horizontal) and UIV screw angle (the angle of the UIV screws and superior endplate). Multivariable logistic regression included age, body mass index, osteopenia/osteoporosis, postoperative sagittal vertical axis, postoperative pelvic-incidence lumbar lordosis mismatch, UIV tilt angle, and UIV screw angle.Results One hundred and seventeen patients underwent adult spinal deformity surgery with a minimum of 2-year follow-up. A total of 41 patients (35.0%) had PJK and 26 (22.2%) had PJF. (1) UIV tilt angle: 96 (82.1%) had lordotic UIV tilt angles, 6 (5.1%) were neutral, and 15 (12.8%) were kyphotic. (2) UIV screw angle: 38 (32.5%) had cranially directed screws, 4 (3.4%) were neutral, and 75 (64.1%) were caudally directed. Both lordotic-angled UIV endplate (OR = 1.06, 95% CI = 1.01–1.12, and P = 0.020) and cranially directed screws (OR = 1.19, 95% CI = 1.07–1.33, and P < 0.001) were associated with higher odds of PJK, with a more pronounced effect of UIV screw angle compared with UIV tilt angle (Wald test, 9.40 vs 4.42). Similar results were found for PJF. Neither parameter was associated with other mechanical complications, reoperations, or patient-reported outcome measures.Conclusions UIV screw angle was more strongly associated with development of PJK/F compared with tilt angle. Overall, these modifiable parameters are directly under the surgeon’s control and can mitigate the development of PJK/F.Clinical Relevance Surgeons may consider selecting a UIV with a neutral or kyphotically directed UIV tilt angle when performing ASD surgery with a UIV in the lower thoracic or lumbar region, as well as use UIV screw angles that are caudally directed, for the purprose of decreasing the risk of developing PJK/F.Level of Evidence 3.