Study design:

Retrospective observational study.

Objectives:

The purpose of this study was to evaluate bone mineral density using Hounsfield unit (HU) values at the upper instrumented vertebrae (UIV), UIV+1, and UIV+2, and to investigate the association with proximal junctional failure (PJF) in female patients with adult spinal deformity (ASD). We also evaluated the relationship between the Global Alignment and Proportion (GAP) score and the HU value of patients after ASD surgery.

Methods:

Fifty-two patients (52 female, mean age 70.2 years) who underwent multiple-level lateral lumbar interbody fusion combined with posterior instrumentation for ASD were included. The patients were divided into two groups, PJF and non-PJF. The demographic, surgical characteristics, and radiographic parameters were compared. Vertebral HU values at UIV, UIV+1 and UIV+2 using preoperative CT scans and immediate postoperative GAP scores were also compared.

Results:

PJF was found in 13 of 52 patients (25.0%). Pre and postoperative thoracic kyphosis were large in PJF patients. Based on the total GAP score, there was no significant difference among the categories of GAP scores (P = 0.514). The statistically significant difference in mean HU values (116.6 ± 28.1 vs. 141.8 ± 41.8, P = 0.049) at UIV. Further correlation analysis showed that the mean HU values in UIV and UIV+1 showed a significantly negative correlation coefficient with the total GAP score.

Conclusion:

Our study suggests that preoperative HU values at UIV may affect the development of PJF for female ASD patients. HU evaluation by preoperative CT may help reduce the incidence of PJF.