C6-C7 Unilateral Facet Dislocation with Right C7 Radiculopathy
20-year-old Male PMVA
The patient is a 20-year-old male who presents after a rollover MVA. He struck his head on the car roof in rotation. He complains of right arm pain, numbness, and mild weakness.
Right triceps, wrist extensor 4/5
Decreased pinprick right C7
Figure 1: Lateral x-ray showing dislocation at C6-C7
Figures 2A, 2B, and 2C: CT scans
Figure 3: Lateral MRI
C6-C7 unilateral facet dislocation with right C7 radiculopathy
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A C6-C7 ACDF with plate and allograft was performed. Reduction was achieved intra-operatively following discectomy.
Figure 6: Post-operative lateral CT scan
The patient had resolution of the radiculopathy, and he showed solid fusion at 3-year follow-up.
This is one of the most common traumatic cervical injuries that a spine surgeon encounters. Dr. Fehlings chose to treat this by reducing the dislocation after an anterior discectomy rather than pre-operatively with tong traction. Given that the patient had mild symptoms with only 4/5 weakness and numbness, and he was being taken to the operating room in short order, I concur with the treatment. Had the patient presented with more profound neurological deficits, I know from having discussed similar cases with him that Dr. Fehlings would have reduced the patient emergently in the ER to decompress the cord.He chose to treat the patient with an anterior approach. I also prefer this approach in similar cases, for the following reasons. First, if there is a disc herniation associated with the dislocation, as there appears to be in this case, it is preferable to remove it anteriorly. In practice, it is often difficult to determine on pre-reduction MRIs if there is a disc herniation or just elevation of the PLL. Had the patient been reduced pre-operatively with traction, followed by a repeat MRI, it is often easier to discern the presence of a herniated disc. However, if one is planning on taking the patient to the OR in short order, it is much simpler to just go anteriorly and remove any herniated fragments that one encounters.
A second reason for the anterior approach preference is that, with the posterior approach, one often encounters muscle and ligamentous disruption. Added to the soft tissue disruption from surgery, some patients develop kyphosis at the adjacent cranial segment. In order to help prevent this, one has to limit the dissection to only the injured level. Further, if the fracture fragment is large, there is occasionally insufficient room to place a lateral mass screw. In such a situation, one can place screws on the opposite side and then utilize spinous process cables or a cable from the C6 spinous process to a C7 lateral mass or pedicle screw. Finally, the anterior approach is less painful and results in a more cosmetically pleasing incision.
The disadvantage of anterior reduction and fixation is that biomechanically, it is less stable, since the posterior tension band is disrupted. However, there is ample clinical literature that demonstrates the safety and efficacy of this approach. As long as the patient is properly immobilized and is trustworthy, the anterior approach works well.
Another disadvantage is that, with posterior soft tissue disruption, it is quite easy to over-distract the segment and place a graft that is too tall. In this case, the disc height has been perfectly reduced and one can see that the interspinous process distance at the C6-C7 level is minimally distracted. By utilizing a graft that is no more than 8mm tall, after standard endplate preparation, one can minimize the potential for over-distraction. Obviously, if the pre-injury disc height was less than normal, a shorter graft should be utilized. Occasionally, it is not possible to get a perfect reduction anteriorly. Soft tissues or a small fracture fragment may interpose itself in the joint and keep it distracted. Hyperextending the neck after the reduction may result in an acceptable position but rarely, one has to open the posterior side to achieve a perfect reduction, if that is felt to be necessary.
In summary, Dr. Fehlings presents a case of C6-C7 unilateral fracture-dislocation that has been treated expertly with anterior decompression, reduction and fixation. The case resolution demonstrates an exemplary approach to a common traumatic injury.