Cervical instability following artificial disc replacement.

BACKGROUND: Although there has been increased interest in utilizing artificial disc replacement (ADR) techniques to treat cervical degenerative disease, few reports have focused on their postoperative complication and reoperation rates. CASE DESCRIPTION: A 52-year-old male underwent the uneventful placement of a C5-C6 cervical ADR for disc disease and foraminal stenosis. One year later, he experienced the onset of severe neck pain attributed to instability of the ADR construct. This required removal of the C5-6 ADR and subsequent fusion.
CONCLUSION: Strict adherence to appropriate criteria is critical for choosing when to place a cervical ADR. This requires documenting; adequate surgical indications, careful selection of the appropriate ADR device, meticulous surgical technique, proper preservation of the supporting structures, and sufficient neural decompression. Copyright:

INTRODUCTION

Anterior cervical discectomy and fusion (ACDF) is typically utilized to treat degenerative cervical disease but carries an approximately 5% risk of adjacent segment disease. Artificial disc replacement (ADR) was developed to preserve motion and avoid this complication of ACDF.[1] Nevertheless, few reports focus on the unique post-ADR risks, complications, and reoperation rates.[2,5] Here, 1 year following an initial C5-C6 ADR, the patient developed postoperative pain and instability warranting a C5-C6 ACDF.

CASE DESCRIPTION

A 52-year-old male underwent an uneventful C5-C6 ADR for an MR documented herniated disc with foraminal stenosis [Figure 1a-d]. One year later, he developed severe neck pain and instability documented on dynamic X-rays. This required removal of the ADR and performance of a C5-C6 ACDF [Figure 2a-g]. At surgery, it was difficult to pull out the ADR. As this required excessive widening of the interbody space, a secondary C5-C6 ACDF was necessitated. One-year postoperatively, the patient was radiographically stable and asymptomatic [Figure 2g].

Figure 1:

(a) The magnetic resonance imaging showed a herniated intervertebral disc (arrow), foraminal stenosis at C5-6 left. (b) The computed tomography showed a foraminal stenosis (arrow) at C5-6 left. (c) The flexion view, (d) The extension view showed disc space narrowing and bony spur at C5-6.

Figure 2:

(a) Postoperative – 1 week, (b) Postoperative – 1 week, (c) Postoperative – 2 months, (d) Postoperative – 2 months, (e) Postoperative – 14 months, (f) Postoperative - 14 months showed an aggravation of cervical instability at C5-6. Cervical instability at C5-6, the ADR site, aggravated in the temporal order of (a-f). (g) Radiograph obtained after a revision operation, in which the ADR implant was removed and ACDF was performed.

DISCUSSION

The success of ADR is attributed to; proper patient selection, operating for the right surgical indications, utilizing meticulous technique, and careful implant device selection.[3,4,6] When patients present with symptomatic postoperative cervical instability following ADR placement, extensive removal of tissue surrounding the ADR device may be warranted, leading to the requirement for ACDF placement.[2,7] In our case, wide removal of the uncovertebral joint was necessary to achieve adequate neural decompression, likely contributed to the instability warranting the secondary ACDF.

CONCLUSION

With the increased use of the ADR, more revision surgery is anticipated. To prevent cervical instability following ADR, one must carefully choose appropriate patients and strictly follow surgical techniques that preserve supporting structures while achieving sufficient neural decompression.