General Session: Spinal Innovation
Presented by: O. Tannous - View Audio/Video Presentation (Members Only)
O. Tannous(1), B. Nguyen(2), S. Garfin(2), R.T. Allen(2)
(1) Georgetown University, Orthopaedics, Washington, DC, United States
(2) UCSD, Orthopaedics, San Diego, CA, United States
Purpose: Proximal junctional kyphosis (PJK) is a multifactorial process that results in excessive kyphosis at the adjacent levels above a multilevel spinal fusion. Although not always clinically significant in its early stages, advanced PJK can lead to sagittal imbalance, construct failure (proximal junctional failure (PJF)), and require revision surgery. As such, spine surgeons have traditionally avoided ending fusion constructs at certain levels such as the thoracolumbar junction or the apex of a curve. The purpose of this study is to evaluate the effects of proximal level osteophytes on the development of PJK.
Methods: We performed a retrospective review of all thoracic and lumbar fusions involving 5 or more levels between January 2012 and September 2015. Patients with less than 6 months of follow-up, inadequate radiographic follow-up, and ankylosing spondylitis were excluded. We measured the horizontal and vertical extension of the osteophytes from the native corner of the vertebral body on the lateral radiograph. We calculated the vertical ratio (Vr) as the anterior vertical gap between interbody osteophytes divided by the height of the center of the disc on the lateral radiograph. We calculated the horizontal ratio (Hr) as the length of the horizontal osteophyte extension divided by horizontal length of the native vertebral body on the lateral radiograph. Preoperative, immediate postoperative, and latest postoperative radiographs were evaluated for the presence of PJK and PJF.
Results: Fourty-two patients met our inclusion criteria with an average age of 71 (16M, 26F). In patients with a Vr ≤ 0.5 (n=13), there were no cases of PJK and 1 case of PJF secondary to a fracture at the upper instrumented vertebra (UIV). In patients with a Vr >0.5 (n=29), there were 13 cases of PJK/PJF [4 cases of PJF due to fracture at the UIV and 1 due to infection at the adjacent disc space]. This association was statistically significant (p=0.018). There was no statistically significant association between Hr and PJK/PJF.
Conclusion: We found a statistically significant association between the vertical ratio of adjacent level osteophytes and the absence of PJK. In other words, adjacent level osteophytes with significant vertical extension appear to be protective against the development of PJK. To our knowledge, there are no previously published studies evaluating this association. This novel concept allows the spine surgeon another tool for preoperative radiographic evaluation and planning. In the presence of significant osteophyte formation (Vr ≤ 0.5), the surgeon may choose a less proximal extension of instrumented fusion then would otherwise be planned. The implications of this idea include lessening the proximal extent of the fusion while achieving the same result (i.e. avoidance of PJK) and reducing the cost of surgery.