Spine imaging after lumbar disc replacement: pitfalls and current recommendations

Abstract

Background: Most lumbar artificial discs are still composed of stainless steel alloys, which prevents adequate postoperative diagnostic imaging of the operated region when using magnetic resonance imaging (MRI). Thus patients with postoperative radicular symptoms or claudication after stainless steel implants often require alternative diagnostic procedures.

Methods: Possible complications of lumbar total disc replacement (TDR) are reviewed from the available literature and imaging recommendations given with regard to implant type. Two illustrative cases are presented in figures.

Results: Access-related complications, infections, implant wear, loosening or fracture, polyethylene inlay dislodgement, facet joint hypertrophy, central stenosis, and ankylosis of the operated segment can be visualised both in titanium and stainless steel implants, but require different imaging modalities due to magnetic artifacts in MRI.

Conclusion: Alternative radiographic procedures should be considered when evaluating patients following TDR. Postoperative complications following lumbar TDR including spinal stenosis causing radiculopathy and implant loosening can be visualised by myelography and radionucleotide techniques as an adjunct to plain film radiographs. Even in the presence of massive stainless steel TDR implants lumbar radicular stenosis and implant loosening can be visualised if myelography and radionuclide techniques are applied.

Figure 1

A 42-year old female patient with degenerative disc disease received implantation of an artificial disc at L5-S1 (Prodisc, Synthes). Postoperative acute bilateral S1-pain without motor deficit could be explained by posterior dislocation of the inferior plate and a subsidence of the cranial plate of the disc prosthesis (a, b). This could clearly be visualised on plain radiographs. No dislocation of the PE inlay occurred which can be seen in the radiographic marker, being still in place. This patient was treated with a conversion into anterior fusion at L5-S1 with pain relief at the 1 year follow-up.

Figure 2

46-year old male patient with increasing bilateral sensomotor deficit at L5 one year postoperatively after implantation of a metal-on-metal stainless steel artificial disc (Maverick, Medtronic) at L4–L5 (a, b) presented major artifacts on MR imaging in T1 (c, d) and T2 (e, f). Neurophysiological investigations revealed acute bilateral L5-compression. Leading diagnostic procedure that could visualise a bilateral compression of L5 was plain myelography, which revealed an anterior compression of the thecal sac (g, h) and compression of the right (i) and left (j) L5-root. Therefore a posterior decompression and instrumented posterolateral fusion was performed while keeping the implant in situ (k, l). Intraoperatively facet hypertrophy and posterior bulging of remaining annulus was seen. The sensomotor deficit resolved completely. The patient regained function and returned to work.