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


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


BACKGROUND
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.
Humphreys
S C
SC
Chattanooga Orthopaedic Group, Foundation for Research, Tennessee, USA.
Hodges
S D
SD
Fisher
D L
DL
Eck
J C
JC
Covington
L A
LA
D002574:Cervical Vertebrae / Q000601:surgery*; D017586:Diskectomy; D006801:Humans; D007403:Intervertebral Disc / Q000473:pathology*; D007405:Intervertebral Disc Displacement / Q000473:pathology* / Q000601:surgery; D017846:Longitudinal Ligaments / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data; D011237:Predictive Value of Tests; D011300:Preoperative Care; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013123:Spinal Fusion