Different Risk Factors of Rod Fracture between L5-S1 and ≥ L4-5 Levels in Adult Spinal Deformity Surgery.

Area of Science:

• Spine surgery
• Orthopedic surgery
• Biomedical engineering

Background:

• Biomechanical properties and surgical techniques vary between L5-S1 and higher lumbar fusion levels (≥ L4-5).
• These differences may lead to distinct risk factors for rod fracture (RF).
• Identifying segment-specific RF risk factors is crucial for surgical planning in adult spinal deformity.

Purpose of the Study:

• To analyze and compare risk factors for rod fracture (RF) at the L5-S1 level versus ≥ L4-5 levels.
• To inform tailored preventive strategies for adult spinal deformity surgery.

Main Methods:

• Retrospective analysis of patients undergoing ≥ 5-level fusion including sacrum/pelvis with ≥ 2 years follow-up.
• Assessment of RF at the segment level (L1-2 to L5-S1).
• Multivariate logistic regression to identify independent risk factors for RF, stratified by L5-S1 and ≥ L4-5 levels.

Main Results:

• Increased fusion length and inadequate pelvic tilt (PT) correction were significant RF risk factors at L5-S1.
• Non-use of teriparatide, anterior column realignment (ACR), posterior fusion (PF), pedicle subtraction osteotomy (PSO), and dual rod constructs were significant RF risk factors at ≥ L4-5.
• A total of 1,329 segments from 318 patients were evaluated.

Conclusions:

• Rod fracture risk factors are segment-specific in adult spinal deformity surgery.
• L5-S1 RF is associated with fusion length and PT correction.
• ≥ L4-5 RF is associated with specific surgical techniques (ACR, PF, PSO), construct type (dual rod), and teriparatide use.