Artificial disc replacement emerged as a motion-sparing alternative to spinal fusion several years ago.
Most spine surgeons approached initial disc replacement technology with necessary skepticism, but now armed with evidence-based research studies and improved technology it's difficult to question the validity of disc replacement in the appropriate patient performed by experienced hands.
Short-term studies comparing cervical disc replacement to anterior cervical discectomy and fusion showed artificial discs could have some benefit — or were at least as effective — as fusion. A study comparing sagittal alignment of one-level total disc replacement using LDR's Mobi-C and anterior cervical discectomy and fusion patients. The study was a randomized, prospective clinical trial examining patients for 24 months. The researchers found no significant difference between outcomes of C2-C7 lordotic and kyphotic Mobi-C patients at the 24-month follow-up.
However, until recently there wasn't strong data examining the long term impact of disc replacement and whether it continued to benefit patients after five years when compared with ACDF.
A 2013 study published in Spine examining the ProDisc-C at 13 different treatment sites compared cervical disc replacement with spinal fusion. The researchers found:
• After five years, patients who underwent TDR had a 97.1 percent probability of no secondary procedures, compared with 85.5 percent for ACDF patients.
• No reoperations in TDR patients were due to implant breakage or device failure.
• Pseudarthrosis was the most common reason for reoperation at the index level among ACDF patients.
• Recurrent neck pain and/or arm pain was the most common reason for reoperation at the adjacent level for both groups.
• Only 2.9 percent of TDR patients had reoperations within five years of the initial surgery, compared with 14.5 percent of the ACDF patients.
One of the biggest issues with spinal fusion is adjacent segment disease; some artificial disc replacement researchers and developers hoped the discs would reduce the risk of ASD. A June 2013 study published in Spine examining 136 patients found the reoperation rate was significantly lower among patients undergoing cervical disc replacement than fusion; reoperation for ASD in patients undergoing TDR was 8.3 percent, compared with 21.2 percent for anterior cervical fusion.
An earlier study published in a 2011 issue of Spine examined 187 patients for adjacent segment disease who either underwent cervical disc replacement or ACDF for one-level cervical disc disease. At two years after surgery, the researchers found the cervical disc replacement group had greater improvement in range of motion and significantly elevated contribution from caudal adjacent level, as well as first, second and third adjacent level.
In 2011, several other studies were published examining spinal fusion alone. The Spine Journal published multiple studies critical of rhBMP-2 use to promote fusion, finding the material more likely to cause retrograde ejaculation than originally reported. In 2012, another study was published showing the number of spinal fusions jumped 137 percent from 1998 to 2008 using data from the Healthcare Cost and Utilization Project Nationwide Inpatient Sample. While the reasons for this significant increase were multifactoral, the report drew increased scrutiny on an expensive procedure such as spinal fusion.
As a result of several converging factors—including stronger evidence, better technology and desire for non-fusion solutions to spinal disorders—disc replacement has become more commonplace. But is it more than a "passing trend" in spinal treatment? Could it revolutionize treatment to make fusion nearly obsolete, as knee and hip replacements have done?
While spinal fusion still dominates the market, several recent developments suggest disc replacement technology is here to stay:
• FDA clearance of LDR's two-level Mobi-C cervical artificial disc
• AMA panel granting two-level cervical disc replacement a Category I CPT code
• North American Spine Society and International Society for the Advancement of Spine Surgery recently released separate coverage statements supporting cervical disc arthroplasty
"All discs approved now have ranges of motion most compatible with flexion/extension, lateral bending," said Todd Albert, MD, in a recent Becker's Spine Review report. "Future approved discs will hopefully have compliance/cushioning to more closely recapitulate the normal disc."
Surgeons are also beginning to perform disc replacements in the outpatient ambulatory surgery center setting at a significant cost reduction when compared with the hospital setting. A study published in 2010 by Richard Wohns, MD, founder of NeoSpine in the Puget Sound Area, Wash., showed cervical disc arthroplasty in the outpatient setting cost 62 percent less than outpatient single-level anterior cervical discectomy and fusion, and 84 percent less than the same procedure in the hospital. Some surgeons are also seeing payers come on board with arthroplasty in ASCs.
"A lot of times — especially for cervical disc replacement — the commercial insurers aren't approving surgeries for inpatient stays, but if you put them as outpatient procedures a lot of primary insurers are approving it," said Bobby Bhatti, MD, of Atlanta Orthopaedic Institute, in a report. "For us, that makes a big difference because if we are able to do it safely in the ASC, and make sure patients are able to go home safely. A lot of surgeons are going to start performing these outpatient procedures."
Two-level artificial disc replacement with Mobi-C also showed success over ACDF in a prospective, randomized clinical trial. At 48 months, the two-level Mobi-C overall study success was 66 percent, compared with 36 percent for two-level ACDF. Safety and efficacy were also significantly better with the artificial disc.
While cervical disc replacement has experienced some success, lumbar disc replacement is much less prevalent and surgeons report difficulty obtaining reimbursement for the procedure. Additionally, new non-fusion technologies in the biologics arena are becoming a popular draw in research and innovation. Only time will tell how cervical disc replacement impacts the field and future innovation.
More Articles on Spine Surgery:
Dr. Gunnar Andersson Becomes 2014 ISASS President
Looking Ahead to ICD-10: Are Spine Surgeons Prepared?
5 Findings on Inconsistency in Spine Literature: Abstract vs. Manuscript