Reliability of magnetic resonance imaging in predicting disc material posterior to the posterior longitudinal ligament in the cervical spine. A prospective study.

STUDY DESIGN

This was a prospective study to evaluate the accuracy of magnetic resonance imaging in predicting the presence of disc material posterior to the posterior longitudinal ligament (PLL), compared with the accuracy of intraoperative visual and tactile examination of the PLL.

OBJECTIVES

To determine the accuracy of magnetic resonance imaging in predicting the presence of disc material posterior to the PLL.

SUMMARY OF BACKGROUND DATA

Whether removal of the disc to the PLL is sufficient when performing an anterior cervical discectomy and fusion or it is necessary to explore the spinal canal by taking down the PLL is controversial.

METHODS

Fifty-four cervical levels were examined by magnetic resonance imaging before surgery to determine whether there was disc material posterior to the PLL. During surgery, the PLL was examined and probed for disruption. The ligament was taken down, and free fragments were identified and removed.

RESULTS

Of 54 levels, 12 were correctly identified by magnetic resonance imaging as having disc material posterior to the PLL, and 26 were correctly identified as not having disc material posterior to the PLL. Surgery confirmed that at 26 levels there was disc material posterior to the PLL. Of these 26, 23 (88.5%) had visual or palpable disruption of the PLL. Magnetic resonance imaging failed to predict disc material posterior to the PLL in 14 of the cases in which its presence was confirmed during surgery. Magnetic resonance imaging had 46.2% sensitivity and 92.9% specificity rates.

CONCLUSIONS

Because of low sensitivity, magnetic resonance imaging should be used cautiously for predicting free disc material posterior to the PLL. Visual or palpable examination of the PLL during surgery is more accurate for this prediction.