Modified Polymethylmethacrylate Cervical Plate and Screw Augmentation Technique for Intraoperative Screw Loosening

Abstract

Case report including technical note. We describe 2 cases of intraoperative cervical plate screw loosening treated by modified screw augmentation using polymethylmethacrylate (PMMA), which used the anchoring effect of hardened PMMA. Intraoperative screw loosening during cervical plating is not rare. PMMA augmentation for a damaged pilot hole is one of the rescue techniques in such a case. A 52-year-old man who had complained of posterior neck pain and left arm pain underwent anterior cervical discectomy and plating with cage at the level of C6/7. An 82-year-old woman presenting bilateral arm weakness and radiating pain after trauma underwent the same operation at C5/6/7. Both of them showed intraoperative screw loosening, which was rectified by modified screw augmentation with PMMA. The difference between this technique and conventional PMMA augmentation is the anchoring effect of hardened PMMA. This technique does not need a new screw trajectory, but uses the existing dead space around the loosened screw. After filling the dead space with about 0.5 mL of PMMA, we inserted a small-sized screw. Once the PMMA hardened, we could remove the small screw and insert a thicker screw along the existing screw thread to increase the screws' pullout strength and achieve rigid fixation of plate. The condition of both patients improved without any instrument failure. In the first case, the visual analog scale and Neck Disability Index improved from 10 to 1 and from 64% to 2%, respectively. In the other patient, the visual analog scale and Neck Disability Index improved from 10 to 4 and from 66% to 40%, respectively. X-ray at 6-month follow-up showed no evidence of screw loosening. This modified PMMA augmentation is a simple, safe, and promising surgical technique to correct intraoperative screw loosening during cervical plating.