Five-Year Follow-Up of a Prospective, Randomized Trial Comparing Two Lumbar Total Disc Replacements.
METHODS
This was a prospective, randomized, controlled, multicenter study.


OBJECTIVE
The purpose of this study was to compare outcomes of two lumbar total disc replacements (TDRs) at 5-year follow-up and report results of serum ion level analysis in a subgroup of patients receiving a metal-on-metal implant.


BACKGROUND
Lumbar TDR has been compared with fusion in several randomized studies, finding TDR noninferior to fusion and superior on some measures. Receiving less attention has been comparing TDR devices. Additionally, there is concern about metal-on-metal implants, with little data available for spine devices.


METHODS
The study included 204 patients receiving Kineflex-L (investigational) and 190 receiving CHARITÉ (control). Outcome measure included Oswestry Disability Index, visual analog pain scales (VAS), patient satisfaction, neurological status, complications, reoperations, and a composite success score. Radiographic assessment included range of motion, subsidence, and heterotrophic ossification. In 32 investigational patients, serum ion analysis was performed for cobalt and chromium. These values were compared with Medicines and Healthcare Products Regulatory Agency values to merit monitoring total hip replacement patients for potential wear problems.


RESULTS
Mean Oswestry and VAS scores in both groups improved significantly by 6 weeks and remained improved during 5-year follow-up (Oswestry Disability Index, scores in both groups were approximately 60 preoperatively vs. 20 at 2- and 5-year follow-up; P < 0.01; VAS scores improved >50% by 6 weeks and remained significantly improved; P < 0.05). Approximately 11% of both groups underwent reoperation. Radiographic analysis found segmental range of motion decreased at 3 month, then increased through 24 months, and was maintained thereafter. Serum ion level analysis found the greatest mean value at any follow-up point was less than 20% of Medicines and Healthcare Products Regulatory Agency recommended minimum value to merit monitoring hip replacement patients.


CONCLUSIONS
This prospective, randomized study comparing two TDRs found no significant differences in outcomes during 5-year follow-up. Both provided statistically significant improvements by 6 weeks that were maintained. This results support other studies. Serum ion levels in TDR patients were well below the recommended threshold levels to merit monitoring.
*Texas Back Institute, Plano, TX †Loveland Orthopedic Clinic, Loveland, CO ‡Proliance Surgeons, Seattle, WA §Triangle Orthopaedic Associates, Durham, NC ¶Carolina Neurosurgery and Spine Associates, Charlotte, NC ||Towson Orthopaedic Associates, Scoliosis and Spine Center, Towson, MD #Texas Back Institute Research Foundation, Plano, TX.
Richard D
RD
Guyer
Kenneth
K
Pettine
Jeffrey S
JS
Roh
Thomas A
TA
Dimmig
Domagoj
D
Coric
Paul C
PC
McAfee
Donna D
DD
Ohnmeiss
D000328:Adult; D002857:Chromium / Q000097:blood; D003035:Cobalt / Q000097:blood; D005500:Follow-Up Studies; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D019736:Prostheses and Implants / Q000009:adverse effects / Q000706:statistics & numerical data*; D011859:Radiography; D016059:Range of Motion, Articular; D059145:Total Disc Replacement / Q000009:adverse effects* / Q000295:instrumentation / Q000706:statistics & numerical data*; D016896:Treatment Outcome
D002857:Chromium; D003035:Cobalt