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Clin Spine Surg. 2016 Jun 3. [Epub ahead of print]

Generation and Development of Paravertebral Ossification in Cervical Artificial Disc Replacement: A Detailed Analytic Report Using Coronal Reconstruction CT.

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*Department of Spine Surgery, Beijing Jishuitan Hospital, Fourth Clinical Medical College of Peking University, Beijing, China 100035†Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, New Haven, CT.



A retrospective follow-up study and review of images in published papers.


To determine whether true heterotopic ossification (HO) occurs in artificial disc replacement (ADR); to evaluate the incidence of paravertebral ossification (PO) and its influence on ADR.


HO is typically defined as the abnormal formation of true bone within extra-skeletal soft tissues. However, HO in ADR does not fit this definition precisely, since it originates from vertebral body, making it hard to distinguish radiologically from pre-existing osteophytes. In this study, the term used for bone formation around ADR is PO.


First, all images in the published papers were evaluated as to whether the presented PO in ADR fit the classic definition of HO or osteophytes. Second, we studied 37 consecutive patients who underwent ADR and follow-up for minimum 24 months. The preoperative and follow-up incidence of PO and its influence on range of motion (ROM) were evaluated using X-ray and computed tomography.


All 52 images of PO were found adjacent to the disc in one segment rather than entire cervical spine. 50 (96.2%) of PO was found originate from the vertebral body rather than in the soft tissue. 31 patients were collected in the follow-up study. No significant difference was found in the incidence of PO between the follow-up and preoperation (61.29% vs. 48.39%, P>0.05). The ROM of the ADR segment in patients with progressed PO (7.44°±4.64°) was significantly lower than that of patients with stable PO grade (12.13°±4.42°, P<0.01) at last follow-up.


A proportion of HO might in fact be the natural development of preoperative osteophytes, which is unrelated to ADR; the remaining HO might be due to changes in biomechanical environment after surgery, which promotes the grade of osteophytes and affects the segment motion.

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