How is pelvic position assessed and managed in a patient with L5‑S1 far‑out syndrome associated with a Bertolotti pseudo‑joint?

Pelvic Position Assessment and Management in L5-S1 Far-Out Syndrome with Bertolotti Pseudo-Joint

In patients with L5-S1 far-out syndrome associated with a Bertolotti pseudo-joint, pelvic position must be evaluated using standing lateral radiographs measuring pelvic incidence, sacral slope, and pelvic tilt, as these parameters directly influence the biomechanical stress on the pseudo-joint and guide surgical decision-making between resection versus fusion. 1, 2

Critical Role of Pelvic Position in Bertolotti Syndrome

Pelvic morphology fundamentally determines the biomechanical environment that creates and perpetuates symptoms in Bertolotti syndrome:

• Pelvic incidence (PI) quantifies the fixed pelvic shape and is significantly elevated in patients with lumbosacral pathology, directly influencing sacral slope and the degree of stress placed on the L5-S1 pseudo-joint 2
• Sacral slope determines the position of the sacral endplate, which the spine must accommodate through compensatory lumbar lordosis to maintain upright balance 2
• Pelvic tilt reflects pelvic orientation (balanced versus retroverted/unbalanced), which is critical for surgical planning 1, 2

Radiographic Assessment Protocol

Essential Measurements on Standing Lateral Radiographs

Obtain standing lateral radiographs of the entire spine and pelvis (not supine films, which miss functional alignment) and measure the following parameters 1, 2:

• Pelvic incidence angle: The angle between a line perpendicular to the sacral plate at its midpoint and a line connecting this point to the femoral head axis 2
• Sacral slope: The angle between the horizontal and the sacral plate 2
• Pelvic tilt: The angle between the vertical and the line connecting the midpoint of the sacral plate to the femoral head axis 2
• L5 incidence angle: Quantifies L5 positioning relative to the sacrum 1, 2
• Lumbosacral angle: Measures the angle at the L5-S1 junction 1, 2
• Lumbar lordosis and thoracic kyphosis: To assess compensatory spinal alignment 2

Advanced Imaging for Pseudo-Joint Characterization

• CT imaging is essential to define the Castellvi classification (Type IIA or IIB pseudo-articulation) and assess the structural anatomy of the transitional vertebra 3, 4
• MRI may be needed to exclude masses, disc pathology, or nerve root compression contributing to far-out syndrome 3

Biomechanical Significance in Treatment Planning

How Pelvic Position Influences Symptoms

The pseudo-joint experiences maximum loading forces during ipsilateral lateral bending with or without ipsilateral axial rotation 5:

• The LSTV significantly reduces motion at L5-S1, particularly in lateral bending and axial rotation 5
• This hypomobility increases adjacent segment motion at superior levels (especially L2-L3), potentially causing activity restriction and accelerated degeneration 5
• Patients with unbalanced (retroverted) pelvis have abnormal pelvic tilt and sacral slope, creating greater mechanical stress on the pseudo-joint 1, 2

Classification for Surgical Decision-Making

Divide patients into balanced versus unbalanced pelvis groups based on pelvic tilt measurements 1:

• Balanced pelvis: Normal pelvic tilt and sacral slope alignment
• Unbalanced pelvis: Retroverted pelvis with abnormally high pelvic tilt and vertical sacral orientation 1, 2

Treatment Algorithm Based on Pelvic Position

Initial Diagnostic Confirmation

Before any surgical intervention, perform diagnostic injection of the pseudo-articulation with steroid and local anesthetic 3, 4:

• Patients responding to pseudo-articulation injection demonstrate significantly greater symptomatic improvement compared to all other injection types (p = 0.002) 4
• Positive response to injection confirms the pseudo-joint as the pain generator and predicts surgical success 3, 4

Surgical Strategy Based on Pelvic Alignment

For patients with balanced pelvis and isolated pseudo-joint pain 5, 4:

• Minimally invasive resection of the pseudo-articulation (pseudoarthrectomy) is the preferred treatment if superior levels show no instability preoperatively 3, 5
• Resection avoids the increased adjacent segment motion seen with fusion 5
• Patients undergoing pseudoarthrectomy after positive injection response show significantly better outcomes than continued injections alone (p < 0.001) 4

For patients with unbalanced (retroverted) pelvis 1, 2:

• Reduction techniques with fusion may be indicated to restore proper pelvic balance and decrease abnormal lumbar lordosis 1
• L5-S1 fusion significantly reduces LSTV joint forces, particularly during ipsilateral lateral bending 5
• However, L5-S1 fusion alone significantly increases L3-L4 adjacent segment motion compared to LSTV alone 5

For patients with pre-existing adjacent level degeneration 5:

• L4-S1 fusion may be necessary, though this significantly increases adjacent segment motion at all levels except L5-S1 5
• This represents a trade-off between treating the pseudo-joint and creating new biomechanical stress 5

Critical Clinical Pitfalls

Failure to identify the LSTV leads to dramatically worse outcomes 4:

• 33% of patients with Bertolotti syndrome have an unidentified LSTV by their provider 4
• Undiagnosed patients undergo significantly more injections (p = 0.031) at locations less likely to provide relief 4
• Without LSTV identification, patients cannot receive targeted pseudo-articulation injections or pseudoarthrectomy, condemning them to failed conservative management 4

Pelvic incidence is unaffected by surgery 1, 2:

• This fixed anatomic parameter cannot be changed, only accommodated through proper surgical planning 2
• Postoperative improvement in L5 incidence angle and lumbosacral angle correlates with better outcomes 2

Ipsilateral lateral bending with or without ipsilateral axial rotation produces the greatest discomfort 5:

• Counsel patients on activity modification to avoid these specific motion patterns 5
• This biomechanical understanding helps predict which patients will benefit most from surgical intervention 5