What are the recommendations for cervical fusion with hardware in terms of MRI compatibility and post-operative management?

MRI Compatibility and Post-Operative Management of Cervical Fusion with Hardware

CT is the most sensitive and specific modality for evaluating cervical fusion with hardware, while MRI has significant limitations due to metal artifacts but remains valuable for assessing soft tissue complications. 1

Imaging Modalities for Post-Operative Cervical Fusion Assessment

CT Scanning

• CT is considered the gold standard for assessment of spinal fusion and hardware integrity due to superior visualization of bony structures 1
• CT offers significant advantages over radiographs in detecting adjacent segment degenerative disease following anterior cervical discectomy and fusion (ACDF) 1
• Recent advances in CT technology including multiplanar reformats, metal artifact reduction techniques, and dose reduction protocols have enhanced evaluation capabilities 1
• In a study of 690 patients with ACDF, CT altered treatment in 60% of patients with abnormal imaging and persistent symptoms 1
• Dual-energy CT and photon counting CT show promise for decreasing metal artifact and increasing image sharpness in hardware evaluation 1

MRI Considerations

• Metal artifact significantly limits assessment of the fused level and hardware on MRI 1
• Despite limitations, MRI remains the most sensitive imaging test for detecting soft tissue abnormalities associated with neck pain 1
• MRI offers benefit in detecting adjacent level disease including disc herniations and nerve root impingement in post-surgical patients 1
• Emerging MRI techniques for metal artifact reduction are likely to increase the utility of MRI in postoperative cervical pain evaluation 1
• Contrast enhancement is not routinely needed for anterior approach surgeries since the epidural space is rarely transgressed 1

CT Myelography

• CT myelography provides an excellent alternative to MRI when assessing the spinal canal and neural foramina in cases where MRI is nondiagnostic due to extensive hardware artifact 1
• This technique has been largely supplanted by MRI but remains valuable in specific scenarios involving hardware 1

Hardware Types and Considerations

Fusion Materials

• Multiple strategies for interbody grafting have demonstrated success, with Class II evidence supporting the use of autograft, allograft, and titanium cages 1
• Autograft bone from iliac crest, allograft bone from cadaveric iliac crest or fibula, and titanium cages are all recommended options for creating arthrodesis after 1- or 2-level ACDF 1
• Alternative materials include polyetheretherketone (PEEK) cages and carbon fiber cages, which have shown fusion rates >50% 1
• Titanium mesh cages with anterior cervical plates have demonstrated effectiveness and safety for interbody fusion after anterior cervical corpectomy 2

Hardware Complications

• Hardware-related complications occur in approximately 16.5% of ACDF cases, including subsidence, plate loosening, screw loosening, and screw breakage 3
• The greater the number of fusion segments, the higher the incidence of complications, particularly in multilevel ACDF (>3 levels) 3
• Most hardware-related complications are not symptomatic and can be treated conservatively, with only a small percentage requiring revision surgery 3

Post-Operative Management

Imaging Protocol

• Initial post-operative assessment should include radiographs to evaluate hardware position 1
• For patients with persistent symptoms, CT is recommended as the primary modality to assess fusion status and hardware integrity 1
• MRI without contrast is appropriate for evaluating adjacent segment disease and soft tissue complications 1
• For suspected infection, MRI with and without contrast is the preferred imaging modality 1

Clinical Monitoring

• Documentation of significant symptoms that impact activities or sleep is essential for establishing medical necessity for any follow-up procedures 4
• Correlation of imaging findings with clinical signs/symptoms through physical examination is required for appropriate management 4
• Failed conservative treatment should be documented before considering additional surgical intervention 4

Common Pitfalls and Caveats

• Degenerative findings on MRI are commonly observed in asymptomatic patients, leading to potential false-positive interpretations 1
• Approximately 65% of asymptomatic patients 50-59 years of age will have radiographic evidence of significant cervical spine degeneration 1
• Recombinant human bone morphogenic protein-2 (rhBMP-2) carries a complication rate of up to 23-27% (especially local edema) compared with 3% for standard approaches and is not recommended for routine use 1
• Polymethyl-methacrylate (PMMA) is not recommended as a means to preserve interspace height after anterior discectomy as fusion generally does not occur 1
• Failing to document pre-operative physical examination findings that correlate with imaging is a common clinical assessment pitfall 4