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. 2022 Jun 9:11:100130.
doi: 10.1016/j.xnsj.2022.100130. eCollection 2022 Sep.

CT based bone mineral density as a predictor of proximal junctional fractures

Swamy Kurra  1   2 , H Francis Farhadi  3   4 , Umesh Metkar  1   5 , Vibhu Krishnan Viswanathan  3   6 , Amy J Minnema  3 , Richard A Tallarico  1 , William F Lavelle  1
Affiliations

CT based bone mineral density as a predictor of proximal junctional fractures

Swamy Kurra et al. N Am Spine Soc J. .

Abstract

Background: Proximal junctional fractures (PJFr) can be a catastrophic complication associated with adult spinal deformity surgery. Osteoporosis can be a major risk factor for the cause of PJFr. Recent studies suggest using surrogate computed tomography (CT) scans in place of spinal dual-energy x-ray absorptiometry (DEXA) scores for bone mineral density (BMD). Investigate the feasibility of using preoperative CT based bone mineral density at upper instrumented vertebrae (UIV) and one level proximally (UIV+1) and distally (UIV-1) to predict the possibility of PJFr risk.

Methods: Retrospective two-academic center case-controlled study, reviewed consecutive adult spinal deformity surgeries; included constructs encompassing at least five fusion levels and fusions to pelvis. Examined demographic, surgical, and radiographic data preoperatively, postoperatively, and final follow-up. Formed groups based on type of proximal junctional deformity (PJD): Control (no PJD), proximal junctional kyphosis (PJK) and PJFr. Preoperative CT BMD values measured in Hounsfield units (HU) for sagittal and axial planes at UIV, UIV+1, and UIV-1 and compared between groups.

Results: N=92 patients. Preoperative CT scan BMD values were significantly lower in PJFr vs. control at: UIV+1 in sagittal (p=0.007), axial (p=0.02) planes; UIV sagittal (p=0.04) and axial (p=0.03) planes; and UIV-1 sagittal (p=0.05) plane. Similarly, lower CT scan BMD values noted in PJFr vs. PJK at: UIV+1 in sagittal (p=0.04) and axial (p=0.03) planes. Trend seen with lower CT scan BMD values at UIV+1 level in PJFr vs. PJK in sagittal (p=0.12) and axial (p=0.10) planes. Preoperative global sagittal imbalance measurements significantly lower in control, but comparable between PJK and PJFr.

Conclusions: Higher preoperative global sagittal imbalance with lower preoperative CT BMD values at UIV and UIV+1 vertebral body may increase the risk of proximal junctional fractures after adult spine deformity surgery. Proximal junctional hooks may supplement the pathogenesis. Readers should note the small sample size.Level of Evidence: 3.

Keywords: Bone mineral density (BMD); Computed tomography (CT) scans; Dual-energy x-ray absorptiometry (DEXA) scans; Proximal junctional fracture (PJFr); Proximal junctional kyphosis (PJK); Spine deformity surgery.

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Conflict of interest statement

This study was performed with the approval of SUNY Upstate Medical University IRB and The Ohio State University Wexner Medical Center IRB and in accordance with the boards’ regulations. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig 1
Fig. 1
In preoperative CT scans, BMD values (HUs) were measured at mid-sagittal and axial cross sections of the vertebrae by drawing an elliptical region of interest (ROI) with the aid of image tools.
Fig 2
Fig. 2
Illustration of measuring the proximal junctional kyphotic angle.
Fig 3
Fig. 3
Postoperative lateral standing radiograph showing proximal junctional kyphosis.
Fig 4
Fig. 4
Postoperative lateral standing x-ray showing vertebral body fracture one level distal to the upper instrumented vertebrae with hooks appearingly disengaged.
See this image and copyright information in PMC

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