Cervical Degenerative Changes with Segmental Kyphosis
The patient is a 44-year-old female who presented with a 6-month history of left-sided neck, periscapular, and arm pain. She also noted paresthesias in her left arm toward the radial forearm, thumb and index finger. She is a nonsmoker.
Electromyography and nerve conduction studies were consistent with C6 radiculopathy. A C5-C6 selective nerve root block was diagnostic for C6 radiculopathy.
Despite treatment with medications, 6-weeks of physical therapy, and chiropractic care, her symptoms persist.
Cervical spine radiographs revealed degenerative changes and loss of disc space height at C4-C5 and C5-C6 with segmental kyphosis C4-C5. (Figures 1, 2)
MRI of the cervical spine revealed similar findings with the addition of C4-C5 and C5-C6 neuroforaminal compromise as a result of disc/osteophyte complex seen on axial imaging. (Figures 3-5)
Figure 3. Axial MRI C4-C5
Figure 4. Axial MRI C5-C6
Figure 5. Axial MRI C6-C7
Cervical degenerative changes causing loss of disc space height at C4-C5 and C5-C6, and segmental kyphosis at C4-C5.
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After 6-months of nonoperative treatment failed to adequately relieve her pain, the patient elected to undergo a 2-level anterior cervical discectomy and arthrodesis.
The patient is a nonsmoker and it was decided to use machined allograft and dynamic cervical plating. The surgical procedure was uneventful.
Anterior-posterior and lateral radiographs (Figures 6, 7), taken 3-months postop, demonstrate the Life Spine Kinetic® dynamic anterior cervical plate system used in this case.
Figure 6. Anterior-posterior x-ray, 3-months postop
Figure 7. Lateral x-ray, 3-months postop
The patient experienced complete relief of her radicular pain prior to hospital discharge. A hard cervical collar was discontinued after 2-weeks. Radiographic evidence of fusion was noted at the 3-month postoperative office visit.
This case demonstrates a classic case of cervical radiculopathy with kyphosis well treated with a 2-level arthrodesis. In the face of cervical spondylosis and kyphosis, a motion sparing device may allow recurrence or retention of spondylosis and clinical failure. Dr. Weinstein points out many of the theoretical advantages of a dynamized plate in this gold standard treatment. We have also demonstrated the fusion advantages of dynamization in this approach. (1) The message here is to retain all these options and to pick the right option for the right patient.
1. Goldberg G, Albert TJ, Vaccaro AR, Hilibrand AS, Anderson DG, Wharton N. Short Term Comparison of Cervical Fusion with Static and Dynamic Plating Using Computerized Motion Analysis. Spine, Volume 32, No. 13, E371 - June 1, 2007.
The use of dynamic cervical plates has its roots in basic bone biology. Bone heals best under compressive loads as first described by Wolff. Static anterior plates shield the bone graft and absorb much of the stress across the disc space. Dynamic plates allow the stress to be transferred and shared by the interbody graft and provide the optimal biomechanical environment for successful spinal fusion.
Initial osteoclastic reaction results in early graft resorption prior to osteoblastic response allowing for fusion. It is this initial resorption that causes increased plate stress in the static plate. Historically, early static plates had a higher rate of failure due to screw and plate breakage and screw pullout which often led to pseudarthosis.
Dynamic plates may be advantageous as they allow for compression across the interspace particularly during the initial osteoclastic response. This may lead to a high fusion rate (particularly with multilevel surgery) and less instrumentation complications.
There are currently three categories of dynamic plate design. Translational or sliding plates, rotationally dynamic, and internally dynamic plates each have advantages and disadvantages. The translational plates typically are designed with oval holes in which the screws are initially seated toward the edge of the plate and allow for compression through the plate hole. The plates may have one or more pairs of oval holes.
The advantages are simple design and good fixation of screw to bone. A major disadvantage is that the position of the plate in relation to the adjacent disc changes with compression of the intervertebral graft. As compression occurs the ends of the plate get closer to the adjacent disc. Recent studies have shown a greater incidence of adjacent level disease when the plate is less than 5-mm from the adjacent disc space. (1)
Rotationally dynamic plates are typical of many plates in current use. The screws are seated in the bone but may change angle to allow dynamization. The advantages of these plates are that the instrumentation and implantation techniques are familiar to most surgeons and off-axis placement has little effect on the ability of the device to allow compression. The disadvantage of this type of plate is that as the plate-screw angle is altered the screws must loosen at least some degree to allow for dynamization to occur. This is because a change in the plate-screw angle must result in some lifting of the plate off the vertebrae or toggle of the bone-screw interface.
Internally dynamized plates may provide the best option for cervical graft compression and load-sharing. These plates are designed to allow compression through a unique mechanism with the plate itself. This allows the screws and the plate to be fixed in position on the anterior cervical spine before, during and after graft compression. While these plates are slightly more technically demanding to apply, the end result is a load-sharing device design that allows a prespecified amount of settling (typically 2mm) without any migration of the plate toward the adjacent healthy disc. The screws are also securely fixed to bone with less risk of loosening compared to the rotationally dynamic plates.
1. Park JB, Cho YS, Riew KD. Development of Adjacent-Level Ossification in Patients with an Anterior Cervical Plate. J. Bone Joint Surg. Am., Mar 2005;87:558-563.