MRI Compatibility of Spine Screws and Cages from 2004
Spine screws and cages from 2004 are generally MRI compatible and safe for scanning at 1.5T and 3T field strengths, though they will produce significant metal artifacts that may limit diagnostic visualization of the immediately adjacent spinal structures. 1, 2
Safety Profile
The primary safety concerns with MRI and spinal hardware are magnetically induced displacement, torque, and RF-induced heating:
Titanium alloy implants (the predominant material used in 2004) show minimal deflection angles averaging 4.3°, well below the 45° safety threshold, indicating magnetically induced forces are less than the weight of the implant itself 1
Temperature changes during MRI scanning are negligible, with titanium alloy implants showing average temperature increases of only 0.48°C above background (0.24°C), which poses no thermal injury risk 1
Stainless steel implants (also used in 2004) demonstrate slightly higher but still safe deflection angles of 7.7° and temperature changes of 0.74°C 1
Long pedicle screw-rod constructs (130-430mm) show maximum heating of only 1.3K even in worst-case scenarios, with negligible magnetically induced torque and displacement forces 2
Artifact Considerations
While safe, these implants create substantial imaging artifacts:
Fast spin echo (FSE) sequences produce the smallest artifacts, while diffusion-weighted imaging (DWI) produces the largest 1
Artifact size increases with higher field strength: titanium rods with CoCr alloy screws produce artifacts of 14.77-17.49mm at 1.5T versus 23.67-27.77mm at 3T 2
STIR sequences produce smaller artifacts than T2-weighted fat saturation sequences and should be preferentially used 1
Optimization strategies include using larger bandwidth, smaller field of view, and appropriate echo train length to minimize artifacts 1
Clinical Implications
Imaging other spinal regions remains feasible despite local artifacts from hardware 2
Direct visualization of fusion status is severely limited by metal artifacts, with CT remaining superior for evaluating screw loosening (64.8% sensitivity) compared to MRI (43.9% sensitivity) even with modern metal artifact reduction sequences 3
Radiography remains the primary modality for routine postoperative assessment of spinal instrumentation, with CT and MRI as useful alternatives for specific indications 4
Practical Recommendation
Proceed with MRI scanning in patients with 2004-era spine hardware when clinically indicated, using 1.5T field strength when possible, FSE or STIR sequences, and optimized parameters (high bandwidth, small FOV). 1, 2 The examination is safe but expect limited visualization of structures immediately adjacent to the hardware. For evaluation of hardware integrity or fusion status specifically, CT remains the preferred modality. 3, 4