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Development of Adjacent-Level Ossification in Patients with an Anterior Cervical Plate
Jong-Beom Park, MD, PhD1; Yong-Sun Cho, MD1; K. Daniel Riew, MD1
1 Department of Orthopaedic Surgery, Barnes-Jewish Hospital at Washington University School of Medicine, One Barnes-Jewish Hospital Plaza, Suite 11300 West Pavilion, St. Louis, MO 63110. E-mail address for K.D. Riew: riewd@wustl.edu
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The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
Investigation performed at the Cervical Spine Service, Department of Orthopaedic Surgery, Barnes-Jewish Hospital at Washington University School of Medicine, St. Louis, Missouri

The Journal of Bone and Joint Surgery, Incorporated
J Bone Joint Surg Am, 2005 Mar 01;87(3):558-563. doi: 10.2106/JBJS.C.01555
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Abstract

Background: It has been our experience that ossification occurs adjacent to anterior cervical plates. Our hypothesis was that the closer the plate is to the adjacent disc space, the greater the ossification.

Methods: We retrospectively reviewed the lateral radiographs of the cervical spine of 118 patients who had a solid fusion following an anterior cervical arthrodesis with a plate for the treatment of a degenerative cervical condition; none of the patients had had cervical spine surgery prior to the index arthrodesis. The plate-to-disc distance was measured on the postoperative lateral radiograph and was used to divide the patients into two groups for each of the two adjacent disc spaces. In group A the plate-to-disc distance was <5 mm, and in group B it was =5 mm. The mean duration of follow-up was 25.7 months. The severity of the ossification at the two adjacent disc spaces was classified on a scale ranging from grade 0 (no ossification) to grade 3 (complete bridging). Eighteen patients were excluded from the measurement of the severity of the caudal ossification because overlapping by the bone of the shoulder precluded adequate visualization of the caudal level.

Results: Ossification developed in seventy (59%) of the 118 cephalad adjacent disc spaces and twenty-nine (29%) of the 100 caudal adjacent disc spaces (p < 0.001). The mean cephalad plate-to-disc distance was shorter than the mean caudal plate-to-disc distance (p < 0.001). The rate of ossification was higher in group A than in group B, both at the cephalad adjacent disc spaces (67% compared with 24%) and at the caudal adjacent disc spaces (45% compared with 5%) (both p < 0.001). In addition, 93% (twenty-six) of the twenty-eight cases of moderate-to-severe ossification developed in group A.

Conclusions: We found a positive association between adjacent-level ossification following anterior cervical plate procedures and the plate-to-disc distance. We now strive to place anterior cervical plates at least 5 mm away from the adjacent disc spaces in order to decrease the likelihood of moderate-to-severe adjacent-level ossification.

Level of Evidence: Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.

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    Accreditation Statement
    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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    Rajkumar S. Amaravati
    Posted on March 18, 2005
    Indications for Anterior Cervical Plating and Fusion
    assistant professor,department of orthopaedics,st.john's medical college and hospital,bangalore-

    To the Editor:

    I commend the authors on their efforts to classify and propose a probable cause of adjacent level ossificationfollowing arthrodesis with an anterior cervical plate. The prevalence of ossification in their series was rather high-- about 59% of 118 cephalad and 29% of 100 caudal adjacent disc spaces. It would have been helpful if they had assesed the clinical outcomes as well. I have a few questions for the authors.

    Degenerative changes occur as part of the natural history of cervical spondylosis. After arhtrodesis, the unfused adjacent segments have more stress. It is also seen that new symptoms that develop after fusion in the adjacent disc levels resolve after Anterior cervical plating and fusion (1). As the disease can progress either way, what is the rationale for performing surgery?

    There is a chance of developing adjacent level ossification after open surgery or after microscopic surgery. Are they an indication of imminent disc lesion?

    It has been found in the literature that at 2-years follow up non- operative treatment gave good to excellent results for symptoms of cervical radiculopathy (2).Also a conflicting report found no difference in the rate of new radiculopathy that develops at adjacent level in patients who had Anterior cervical discectomy or Anterior cervical plating[ACP] with fusion (3).So we are at cross roads as what to tell our patients and how much to tell.Whether to go for conservative treatment or operative.

    Finally, I would like to know whether the authors feel there a need to remove the posterior longitudinal ligament in all cases while doing ACP with fusion.If yes,then what are the do's and and dont's and how much does this influence the adjacent level ossification?

    REFERENCES:

    1.Hillbrand AS,Carlson GD,Palumbo MA,Jones PK, Bohlman HH. Radiculopathy and myelopathy at segments adjacent to the site of a previous anterior cervical arthrodesis.J. Bone Joint Surg Am 1999;81:519- 528.

    2.Saal JS, Saal JA,Yurth EF.Nonoperative management of herniated cervicalintervertebral disc with radiculopathy. Spine 1996;21:1877-1883.

    3.Lunsford LD,Bissonette D,Janetta PJ,Sheptaak PE,Zorub DS.Anterior surgery for Cervical disc disease Part 1:Treatment of lateral cervical disc herniation in 253 cases.J Neurosurg 1980;53 :1-11.

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