MRI-findings after uncomplicated anterior cervical discectomy.

Background: The anterior approach for cervical discectomy with methacrylate-implant involves manipulations on vertebral bodies and ligaments. Foreign materials like methacrylate and fibrin sponge are inserted. On postoperative MRI it may be difficult to differentiate pathological from "normal" findings caused by routine manipulations.

Method: In this study 14 patients free of symptoms after anterior discectomy with methacrylate-implant were examined clinically and a MRI was performed on the 7th day after surgery and again after a 6 month follow-up. All patients had an uneventful recovery and no signs of inflammation after surgery.

Findings: Independent of the underlying pathology (e.g. soft or hard disc) 73% of the patients had a signal reduction within the vertebral bodies adjacent to the operated disc on T1-weighted spin-echo images on the 7th postoperative day. Signal intensities were normal after 6 months in all patients. Remarkable metal artifacts were present in one patient only. The methacrylate-implant could be identified as a hypo-intense structure on all sequences at any time without artifacts. In 80% of the cases a hyperintensity was found on T2-weighted images between the methacrylate-implant and the dura on the 7th postoperative day. A protrusion of the posterior ligament was present at the level of the operated disc on day 7 after surgery, which had resolved completely 6 months later. This may mimic residual disc tissue or osteophytes early after surgery.

Interpretation: It is very important to know this "normal" postoperative appearance of the cervical spine in order to avoid misinterpretations.