What is the best approach to manage bilateral pseudoarthrosis (false joint) formation at the lumbosacral junction in an adult patient with a history of spinal issues or trauma?

Management of Bilateral Pseudoarthrosis at the Lumbosacral Junction

Immediate Diagnostic Approach

Bilateral pseudoarthrosis at the lumbosacral junction requires revision surgery with circumferential fusion using rigid instrumentation, advanced sacropelvic fixation, and biologics to achieve solid arthrodesis and prevent recurrent failure.

Confirming the Diagnosis

• Obtain thin-cut CT imaging with fine axial cuts and multiplanar reconstructions as this is the most sensitive method for assessing fusion status following instrumented lumbar fusion 1
• When bilateral posterolateral intertransverse bridging bone is absent on CT, this strongly suggests pseudarthrosis 1
• Bilateral absence of facet fusion is more predictive of pseudarthrosis (5.19 likelihood ratio) than bilateral absence of posterolateral fusion (2.90 likelihood ratio) 1
• Obtain flexion-extension radiographs to assess for motion at the treated levels, though motion does not definitively confirm pseudarthrosis 1
• Static radiographs alone are not recommended as a stand-alone method (Grade A recommendation) 1

Clinical Presentation to Assess

• Persistent or recurrent axial back pain at the lumbosacral junction 2
• Radicular symptoms suggesting nerve root compression 2
• Signs of instability such as positional symptoms or mechanical pain patterns 3
• Duration of symptoms and response to conservative measures 4

Surgical Management Strategy

Primary Surgical Approach

Perform revision surgery with circumferential (360-degree) fusion combining anterior interbody fusion and posterior instrumented fusion 4, 5, 6

Anterior Component

• Anterior lumbar interbody fusion (ALIF) at L5-S1 is strongly preferred over other interbody techniques for lumbosacral junction fusion 5
• ALIF achieves greater segmental lordosis restoration and has lower pseudarthrosis rates compared to alternative approaches 5
• Use structural interbody grafts (fibular strut allograft or cage) to restore disc height and lordosis 6
• All patients in one series achieved solid fusion at L5-S1 using anterior fibular strut grafting combined with posterior instrumentation 6

Posterior Component

• Replace any loose instrumentation and extend fixation into the pelvis using advanced sacropelvic fixation 4
• Use bilateral multiple S2-alar-iliac (S2AI) screws combined with multirod construct (MS-MR) for optimal biomechanical stability 7
• The MS-MR construct provides the most significant reduction in range of motion and stress on instrumentation, cages, S1 superior endplate, and sacrum 7
• This configuration most adequately reduces risk of recurrent pseudarthrosis, implant failure, and sacrum fracture 7
• Perform bilateral facetectomies if needed for adequate exposure and decompression 8

Biologics Enhancement

• Use autogenous bone graft harvested from iliac crest as the gold standard biologic 2, 4
• Consider supplementation with allograft morsel to extend graft volume 3
• More potent biologics may be considered though evidence is limited in the lumbar spine literature 4
• Rigid instrumentation combined with biologics enhances success rates for pseudarthrosis treatment 4

Critical Technical Considerations

Biomechanical Principles

• The lumbosacral junction experiences the highest mechanical stress in long spinal constructs 7
• Multiple pelvic screws increase mechanical stability and reduce stress on all components of the construct 7
• Multirod constructs further decrease stress in extension and axial rotation compared to single rod constructs 7
• Combining both multiple pelvic screws AND multirod construct provides synergistic benefit 7

Common Pitfalls to Avoid

• Do not rely on static radiographs alone for diagnosis - they have Grade A recommendation against use as stand-alone method 1
• Do not perform isolated posterior revision without addressing anterior column - circumferential fusion has higher success rates 4, 6
• Do not use inadequate sacropelvic fixation - single S2AI screws with single rod construct have higher failure rates than advanced constructs 7
• Do not underestimate the importance of rigid instrumentation - success rates are significantly enhanced with rigid fixation 4

Expected Outcomes

• Solid fusion achievement approaches 100% with circumferential fusion and rigid instrumentation 6
• Clinical improvement in back pain and radicular symptoms occurs in the majority of successfully fused patients 2, 6
• Long-term follow-up is essential as complications can occur years after initial fusion 2
• Even after achieving union, the repaired segment may remain biologically and mechanically inferior 2

When Advanced Techniques Are Insufficient

• If revision surgery fails or patient has significant comorbidities precluding extensive surgery, consider prosthesis resection with arthrodesis (though this sacrifices joint function) 1
• Amputation is reserved only for recalcitrant cases with intractable infection or pain 1