Introduction: A prospective randomized study of artifical disc replacement vs. lumbar fusion for one-level disc pathology with 2 year minimum follow-up was completed in compliance with a U.S. FDA protocol.

Methods: A total of 15 investigational sites enrolled 375 subjects with a randomization in a 2:1 ratio. Of the 375, 205 were randomized to receive the Charité artificial disc, and 99 were randomized to receive anterior lumbar interbody fusion with BAK cages. An additional group of 71 patients received the Charité disc as “training cases” prior to beginning randomization. Clinical outcome measures included VAS, Oswestry Disability Index, and SF-36 Healthy Surveys. A total of 6,900 radiographs were digitized throughout the 24 month treatment interval. The 276 disc replacement patients were allocated into one of three groups based on radiographic technical paramenters-- Group I – Ideal, defined as Charité disc placement within 3 mm of ideal in both planes. Coronal plane = AP radiograph = midline or within 3 mm of midline. Mid-Sagittal plane = Lateral radiograph = 2mm posterior to middle of vertebral body or within 3mm of this axis. Group II —Suboptimal (not ideal) and Group III – Poor.

Results: The Charité prosthesis was significantly more effective than BAK in restoring the height of the collapsed disk space (p < 0.001). In Charité cases, the mean initial disc space height at the L5-S1 operative level was 5.2 mm +/− 1.44 (Std Dev) and increased to a mean of 13.5 mm +/− 1.18 (Std Dev). For BAK, the initial disc space height was 5.9.mm +/− 1.74 and increased to an immediate post-operative disk space height of 11.9 mm +/− 2.07. There was less subsidence with the Charite disk replacement than the BAK control at 2 years (p < 0.001). Of the 276 subject radiographs analysed with Charité disc replacement, 83% were classified as Group I, 11% as Group II, and 6% as Group III.

The mean Oswestry Disability Index scores at 2 years correlated with technical accuracy in placement of the prosthesis: Group I – 24.1; Group II – 30.3; and Group III – 36.3 (p < .05). The Mean VAS scores at 2 years correlated with technical accuracy in placement of the prosthesis: Group I – 28.3; Group II – 35.4; and Group III – 48.4 (p = 0.016). The mean flexion/extension range of motion and prosthesis function also correlated with device placement: Group I – 7.12 +/− 4.06 degrees; Group II – 7.47 +/− 4.41 degrees; and Group III – 3.15 +/− 3.51 degrees (p = 0.003).

Discussion: The surgical technical accuracy of Charité artificial disc placement correlated with clinical outcome, range of motion, and device functionality at 2 years. The Charité Lumbar Disk replacement proved to be a successful alternative to traditional lumbar fusion in every parameter. The results from this U.S. Investigational study confirm that proper placement of the Charité artificial disc improves clinical and radiological outcomes.