Abstract
BACKGROUND: Low bone mineral density (BMD) on dual energy x-ray absorptiometry (DXA) is likely a risk factor for proximal junctional kyphosis (PJK) and proximal junctional failure (PJF). However, prior instrumentation and degenerative changes can preclude a lumbar BMD measurement. Hounsfield units (HU) represent an alternative method to estimate BMD via targeted measurements at the intended operative levels. OBJECTIVE: To determine if patients with lower HU at the upper instrumented vertebrae (UIV) and vertebral body superior to the UIV (UIV + 1) are at greater risk for PJK and PJF. METHODS: A retrospective chart review identified patients at least 50 yr of age who underwent instrumented lumbar fusion with pelvic fixation, a UIV from T10 to L2, and a preoperative computed tomography (CT) encompassing the UIV. HU were measured at the UIV, UIV + 1, and the L3-L4 vertebral bodies. RESULTS: A total of 150 patients (80 women and 70 men) were included with an average age of 66 yr and average follow-up of 32 mo. Multivariable logistic regression analysis with an area under the curve (AUC) of 0.89 demonstrated HU at the UIV/UIV + 1 as the only independent predictor of PJK/PJF with an odds ratio of 0.94 (P-value =. 031) for a change in a single HU. Patients with HU at UIV/UIV + 1 of <110 (n = 35), 110 to 160 (n = 73), and >160 (n = 42) had a rate of PJK/PJF of 63%, 27%, and 12%, respectively (P-value <. 001). CONCLUSION: Patients with lower HU at the UIV and UIV + 1 were significantly associated with PJK and PJF, with an optimal cutoff of 122 HU that maximizes sensitivity and specificity.
Original language | English (US) |
---|---|
Pages (from-to) | 270-275 |
Number of pages | 6 |
Journal | Operative Neurosurgery |
Volume | 21 |
Issue number | 4 |
DOIs | |
State | Published - Oct 1 2021 |
Keywords
- Bone mineral density
- Fusion
- Hounsfield units
- Lumbar
- Proximal junctional failure
- Proximal junctional kyphosis
- Spine
ASJC Scopus subject areas
- Surgery
- Clinical Neurology