Ageing and BMI in Focus: Rethinking Risk Assessment for Vertebral Fragility and Pedicle Screw Loosening in Older...

Area of Science:

• Orthopedics
• Geriatrics
• Radiology

Background:

• Pathological vertebral fragility (path-VF) elevates risks of osteoporotic fractures and pedicle screw loosening (PSL) post-spinal fusion.
• Existing WHO BMI classifications may not adequately assess path-VF risks in elderly individuals, particularly those within the normal-weight range.

Purpose of the Study:

• To investigate the adequacy of current BMI classifications in identifying path-VF risks among elderly patients undergoing spinal surgery.
• To identify specific BMI and age thresholds associated with increased path-VF risk in this demographic.

Main Methods:

• Retrospective analysis of 225 patients undergoing kyphoplasty or posterior instrumented spinal fusion (PISF).
• Path-VF defined by non-tumorous fractures, screw reinforcement, or PSL within six months.
• Analysis included Hounsfield units (HU), BMI, odds ratios (ORs), age trends, and logistic regression.

Main Results:

• Path-VF group exhibited significantly lower mean HU values (71.37 ± 30.50) compared to controls (130.35 ± 52.53).
• Normal-weight females showed a borderline risk (OR 2.03, p=0.0495); obesity and being overweight (males) were protective.
• Logistic regression identified BMI < 22.5 kg/m² and age > 67.5 years as significant risk thresholds, with 20.2% of path-VF patients over 67.5 having normal weight.

Conclusions:

• The standard WHO lower normal BMI limit (18.5 kg/m²) may underestimate path-VF risk in patients over 67.5 years, potentially missing 24.7% of cases.
• Clinicians should exercise caution when interpreting lower normal BMI values (<22.5 kg/m²) in elderly patients undergoing spinal surgery.