Postoperative decrease in Hounsfield unit values at adjacent vertebrae after thoraco-pelvic fusion as a risk factor...

Area of Science:

• Orthopedics
• Spinal Surgery
• Radiology

Background:

• Proximal junctional kyphosis and failure (PJKF) is a common complication following adult spinal deformity surgery.
• Osteoporosis is a known risk factor for PJKF.
• The impact of long thoracolumbar fusion with pelvic fixation on regional bone density and its association with PJKF is not fully understood.

Purpose of the Study:

• To investigate the influence of long thoracolumbar fusion with pelvic fixation on the regional bone density of adjacent vertebrae.
• To evaluate the association between postoperative bone loss and the incidence of proximal junctional kyphosis and failure.

Main Methods:

• Retrospective study of 127 adult patients undergoing either long thoracolumbar fusion (pelvis to T10 or above) or single-level posterior lumbar interbody fusion (control).
• Computed tomography (CT) scans were analyzed preoperatively and within 1-2 weeks postoperatively to assess bone density (Hounsfield units) at vertebrae adjacent to the uppermost instrumented level (UIV+1 and UIV+2).
• Comparison of bone density changes and incidence of PJKF between the long fusion and control groups.

Main Results:

• Both long fusion and PJKF negatively affected regional bone density (Hounsfield units) at adjacent vertebral levels immediately after surgery.
• A significant decrease in Hounsfield units was observed at the UIV+2 level in both groups postoperatively.
• Patients who developed PJKF (within 18 months) showed significantly lower Hounsfield unit values at UIV+1 and UIV+2 compared to those without PJKF, indicating greater postoperative bone loss.

Conclusions:

• Long thoraco-pelvic fusion and proximal junctional kyphosis and failure are associated with reduced regional bone density in adjacent vertebrae.
• Greater postoperative bone loss at adjacent levels is observed in patients who subsequently develop proximal junctional kyphosis and failure.
• These findings highlight the detrimental effect of extensive fusion and subsequent complications on local bone quality.