Abstract:
Study Design. Prospective clinical study enrolled in 2 centers (Munich and Liberec) as part of a prospective European multicenter study with ProDisc C (Synthes Inc., Paoli, PA).

Objectives. The first goal of the study was to evaluate the rate of heterotopic ossifications identified with plain radiograph following total cervical disc replacement (TCDR). The second goal was to show whether segmental motion can be preserved, and whether TCDR can provide improvement of the patient’s ability to perform activities of daily living as well as a decrease of pain.

Summary of Background Data. Only a few reports about the radiologic outcome after TCDR are published so far. Heterotopic ossification is a well-known phenomenon after total hip arthroplasty. The rate of heterotopic ossification following TCDR is unclear.

Methods. The radiographs of 54 patients (in total, 77 implanted prostheses) were analyzed 1 year after TCDR with a ProDisc C prosthesis. We classified the heterotopic ossification in 5 grades according to a recently published classification system for lumbar total disc replacement. For clinical parameters, the visual analog scale and the Neck Disability Index were evaluated preoperatively and 1 year postoperatively. The Student t test and Wilcoxon test were used for statistical analysis.

Results. In 26 treated segments (33.8%), no heterotopic ossification was detectable. Grade 1 ossifications were present in 6 levels (7.8%). A total of 30 segments (39.0%) showed grade 2 ossifications. Heterotopic ossifications that led to restrictions of the range of motion were present in 8 cases (10.4%). One year postoperatively, 7 cases (9.1%) had a spontaneous fusion of the treated segment. The clinical parameters improved significantly and were similar to previous reports about TCDR.

Conclusions. Only 33.8% of the patients did not show any signs of heterotopic ossification, and the rate of spontaneous fusion after TCDR 1 year after surgery was unexpectedly high. There were 49.4% of the patients with grade 2-3 ossification, which lets us suspect an even higher rate of spontaneous fusion after long-term follow-ups. Motion preservation after TCDR is only guaranteed if spontaneous fusion can be prevented. Thus, mobility of the implanted segments needs to be further studied.

(C) 2006 Lippincott Williams & Wilkins, Inc.

April 20, 2005 (New Orleans) — With two-year follow-up data on just under 100 patients, it appears that multiple-level arthroplasty with the Porous Coated Motion (PCM) cervical disc is as effective at reducing pain and preserving spine function as single-level arthroplasty with the device, the lead investigator reports.

Luiz Pimenta, MD, a neurosurgeon at the Clinica Mattos Pimenta in Sao Paolo, Brazil, presented the data here at the American Association of Neurological Surgeons annual meeting on behalf of the multiple centers participating in the PCM study. Dr. Pimenta has served as a consultant to PCM’s developer and manufacturer, Cervitech, Inc.

That company is based in the U.K. and the U.S., with headquarters in Rockaway, New Jersey.

According to Cervitech, the PCM disc is designed to allow “translational motion in an arc consistent with the natural motion of the cervical spine segment.” The disc has an ultra-high molecular weight polyethylene bearing surface attached to the lower endplate. Both of the endplates are made of cobalt chrome.

In the trial presented by Dr. Pimenta, 41 patients had a single-level replacement, 34 patients had a two-level replacement, eight had three-level replacement, and four had four-level replacement.

For single-level replacement patients, mean scores for the neck disability index (NDI) and the visual analog scale (VAS) score decreased by 38.7% and 38.6%, respectively, compared with 65% and 61.4% for the bilevel group. For the multiple-level replacement patients, the NDI decreased by 95.3% and the VAS by 86.6%.

Dr. Pimenta also reported on Odom scores at two years. Almost 13% of single-level replacement patients had excellent Odom scores compared with 16.3% of bilevel patients and 20.8% of multiple-level replacement patients.

In patients with multiple-level replacements, the clinical outcomes were generally better, and range of motion was much improved also, said Dr. Pimenta. Clinical studies of single-level arthroplasty might be underestimating the true benefit of the procedure, he said, but added that a large-scale randomized study was necessary.

Edward Benzel, MD, director of spinal disorders at the Cleveland Clinic Foundation in Ohio, said it appeared that the PCM disc is helping to establish and maintain lordosis. Fusion, he said, is well known for leading to decreased range of motion and degenerative changes at adjacent levels.

With the PCM disc study, it seemed that restoration of sagittal alignment was a key to the success seen with the multiple-level replacement patients, Dr. Benzel said. The maintenance of sagittal alignment may, in fact, be one of the most important variables, he said.

Total disc arthroplasty is likely to be much more costly than fusion, but “if there is greater quality, we may be willing to accept a greater cost,” Dr. Benzel said. He called the PCM disc study a “seminal work.” I am republishing here because it is one of the few articles explaining the potential benefits of Cervical ADR at multiple levels.

AANS 2005 Annual Meeting: Abstract 755. April 19, 2005.

Reviewed by Gary D. Vogin, MD