Jeffrey Watts, DO
Richard D. Guyer, MD
Texas Back Institute and Texas Back Institute Research Foundation
- The gold standard for symptomatic cervical degenerative disease is fusion. Cervical total disc replacement (CTDR) is intended to remove the degenerated tissues and replace them with motion-preserving implants.
- Many studies have found CTDR to be non-inferior or superior to anterior discectomy and fusion( ACDF).
- CTDR may provide more benefit over fusion surgery if motion at the operative level is preserved, and adjacent-level degeneration lessened or prevented.
Goals of CTDR
- Reduce pain
- Preserve motion and improve function
- Possibly lessen the incidence of adjacent segment degeneration
- Designs currently approved range from two metal endplates with a polyethylene insert between them (ProDisc-C), (Mobi-C), to a ball-and-trough articulation (Prestige), to a polyurethane nucleus and a poly urethane sheath contained by porous coated titanium endplates (Bryan).
- These devices are implanted via a standard Smith Robinson anterior cervical approach, similar to ACDF. Discectomy and preparation of the disc space are similar between the two procedures as well.
Primary Indications for CTDR
- Symptomatic one- or two-level cervical degenerative disc disease that has failed non-operative care including pain medications, activity modification, physical therapy, and injections. Symptoms include neck pain and arm pain. Some clinicians would also include myelopathy from soft disc herniation. Only the Mobi-C has 2 level approval by the FDA.
Primary Contra-indications for CTDR
- Osteoporosis, fracture, instability, infection, tumor. Advanced cervical spondylosis with significant facet disease would preclude arthroplasty
Clinical Outcome CTDR
- Hisey, et al. in the trial comparing Mobi-C TDR to ACDF, reported that TDR is a safe and effective treatment for single-level disc degeneration with less adjacent segment degeneration.
- Davis, et al. found the Mobi-C to be as safe and effective as ACDF for the treatment of degenerative disc disease at 2 contiguous cervical levels.
- Janssen, et al. noted both ProDisc-C and ACDF were effective in reducing neck pain and arm pain and improving and maintaining function and health-related quality of life in patients with single-level cervical degenerative disc disease. They also found no significant differences in the rates of device-related adverse events between the two groups.
- For both CTDR and ACDF, Coric, et al. reported the mean neck disability index( NDI) and VAS pain scores improved significantly in both groups at 6 weeks and remained significantly improved at 24 month after surgery. The ROM in the CTDR group decreased at 3 months but was significantly greater than the preoperative mean at 12 and 24 month follow up. The overall success rate was significantly greater in CTDR compared to ACDF.
- Hisey, et al. found the success rate was similar between CTDR and ACDF at 48 months. The NDI, VAS, and SF-12 scores were significantly improved in early follow up in both groups, and maintained throughout 48 months. Subsequent surgery rate and adjacent-level degeneration were statistically higher for ACDF compared with TDR.
- Vaccaro, et al. reported superiority in overall success of TDR (SECURE) compared to ACDF at 24 months. TDR showed significant improvement in pain and function in terms of NDI, VAS, and SF-36 at 24 months, and the percentage of patients experiencing secondary surgical interventions at the index level were lower for the TDR group compared to the ACDF group.
- Phillips, et al. found, clinical measures including neck and arm VAS, NDI, SF-36, and neurological status, were significantly improved from preoperative baselines in both TDR and ACDF groups at 2 years. They found NDI at 2 years was lower for TDR, and there were no statistical differences between groups in rates of surgery-related adverse events or secondary surgical procedures. TDR patients reported lower dysphasia scores and higher patient satisfaction.
- Heller, et al. showed improvement in all clinical outcome measures at 12- and 24 months postoperatively for both TDR (BRYAN) and ACDF. The TDR group had statistically greater improvement in the primary outcome variables including NDI and a lower percentage of adverse events. There was no statistical difference between the groups with regard to the rate of secondary surgical procedures.
- Mummaneni, et al. compared TDR (PRESTIGE ST) with ACDF. They found greater improvement in NDI with TDR. TDR also had a statistically significant higher rate of neurological success as well as a lower rate of secondary revision surgery and supplemental fixation. TDR had greater improvement in SF-36 physical component as well as relief of neck pain. The TDR group returned to work 16 days earlier than the ACDF group and had a significantly lower rate of adjacent-segment reoperation. There were no cases of TDR implant failure or migration.
- Murrey, et al. compared TDR (ProDisc-C) to ACDF and reported that NDI and SF-36 post-op scores were lower compared to preoperative scores for both groups. VAS neck pain and arm pain scores were also lower for both groups. TDR had higher neurologic success. They found ACDF had a statistically significant higher rate of secondary surgeries. They found that the TDR group had a lower percentage of patients on narcotics and muscle relaxants at 24 months.
Radiographic Outcome (Figs. 1 and 2):
- Studies have shown that most patients retain ROM of 4 degrees or more in flexion/extension at the operative level after CTDR.
- Heterotopic ossification is a known possibility, affecting less than 5% of CTDR. This can affect the ROM of the CTDR, but the clinical significance seems negligible—the result being similar to fusion in ACDF.
Fig. 1. AP and Lateral radiograhs in flexion and extension of Mobi C TDR at C5-C6
Fig. 2. Lateral and AP radiographs of Pro Disc-CTDR
Complications and Re-operations
- The approach-related complications for CTDR are the same as anterior cervical discectomy and fusion. It includes injury to local neurovascular structures (recurrent laryngeal nerve) and esophageal injury.
- Blumenthal, et al. found that the reoperation rate and time to reoperation for TDR was significantly less than ACDF. They reported that reoperations for adjacent segment changes were less frequent and occurred later in TDR compared with ACDF.
- Coric, et al. found no significant differences between CTDR and ACDF groups when comparing operative time, blood loss, length of hospital stay, or the reoperation rate. They also looked at adjacent-level degeneration between CTDR and ACDF and found more ACDF patients with severe adjacent-level degeneration at 2 years.
- Delamarter, et al. found significantly higher probability of no secondary surgery at the index or adjacent levels at 5 years for CTDR (ProDisc-C) compared to ACDF. They found no ProDisc-C reoperations for implant breakages or device failures. For patients who underwent ACDF, the most common reason for reoperation at the index level was pseudarthrosis. For both ACDF and CTDR, the most common reason for adjacent-level surgery was recurrent neck and/or arm pain.
- Postoperative care includes preoperative antibiotic coverage and rehabilitation similar to ACDF surgery with the exception of no concern for fusion in CTDR. Postoperative rehabilitation is left mostly to the surgeon’s discretion but generally may include a soft collar for wound healing for the first 2 weeks. Others may recommend 2 weeks of empiric anti-inflammatories to hypothetically lessen heterotopic bone formation.
- Cost is always a concern with new treatments.
- Studies have shown both ACDF and CTDR to be cost-effective treatments for cervical DDD.
- Some studies show CTDR to be significantly more cost effective than ACDF which may involve the use of a plate, cage, and biologic substitutes.
- A benefit to CTDR is less cost variability compared to ACDF.
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