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Domagoj Coric, Richard D. Guyer, Pierce D. Nunley, David Musante, Cameron Carmody, Charles Gordon, Carl Lauryssen, Margaret O. Boltes and Donna D. Ohnmeiss

OBJECTIVE

Seven cervical total disc replacement (TDR) devices have received FDA approval since 2006. These devices represent a heterogeneous assortment of implants made from various biomaterials with different biomechanical properties. The majority of these devices are composed of metallic endplates with a polymer core. In this prospective, randomized multicenter study, the authors evaluate the safety and efficacy of a metal-on-metal (MoM) TDR (Kineflex|C) versus anterior cervical discectomy and fusion (ACDF) in the treatment of single-level spondylosis with radiculopathy through a long-term (5-year) follow-up.

METHODS

An FDA-regulated investigational device exemption (IDE) pivotal trial was conducted at 21 centers across the United States. Standard validated outcome measures including the Neck Disability Index (NDI) and visual analog scale (VAS) for assessing pain were used. Patients were randomized to undergo TDR using the Kineflex|C cervical artificial disc or anterior cervical fusion using structural allograft and an anterior plate. Patients were evaluated preoperatively and at 6 weeks and 3, 6, 12, 24, 36, 48, and 60 months after surgery. Serum ion analysis was performed on a subset of patients randomized to receive the MoM TDR.

RESULTS

A total of 269 patients were enrolled and randomly assigned to undergo either TDR (136 patients) or ACDF (133 patients). There were no significant differences between the TDR and ACDF groups in terms of operative time, blood loss, or length of hospital stay. In both groups, the mean NDI scores improved significantly by 6 weeks after surgery and remained significantly improved throughout the 60-month follow-up (both p < 0.01). Similarly, VAS pain scores improved significantly by 6 weeks and remained significantly improved through the 60-month follow-up (both p < 0.01). There were no significant changes in outcomes between the 24- and 60-month follow-ups in either group. Range of motion in the TDR group decreased at 3 months but was significantly greater than the preoperative mean value at the 12- and 24-month follow-ups and remained significantly improved through the 60-month period. There were no significant differences between the 2 groups in terms of reoperation/revision surgery or device-/surgery-related adverse events. The serum ion analysis revealed cobalt and chromium levels significantly lower than the levels that merit monitoring.

CONCLUSIONS

Cervical TDR with an MoM device is safe and efficacious at the 5-year follow-up. These results from a prospective randomized study support that Kineflex|C TDR as a viable alternative to ACDF in appropriately selected patients with cervical radiculopathy.

Clinical trial registration no.: NCT00374413 (clinicaltrials.gov)

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Mark N. Hadley

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Domagoj Coric, Pierce D. Nunley, Richard D. Guyer, David Musante, Cameron N. Carmody, Charles R. Gordon, Carl Lauryssen, Donna D. Ohnmeiss and Margaret O. Boltes

Object

Cervical total disc replacement (CTDR) represents a relatively novel procedure intended to address some of the shortcomings associated with anterior cervical discectomy and fusion (ACDF) by preserving motion at the treated level. This prospective, randomized, multicenter study evaluates the safety and efficacy of a new metal-on-metal CTDR implant (Kineflex|C) by comparing it with ACDF in the treatment of single-level spondylosis with radiculopathy.

Methods

The study was a prospective, randomized US FDA Investigational Device Exemption (IDE) pivotal trial conducted at 21 centers across the US. The primary clinical outcome measures included the Neck Disability Index (NDI), visual analog scale (VAS) scores, and a composite measure of clinical success. Patients were randomized to CTDR using the Kineflex|C (SpinalMotion, Inc.) cervical artificial disc or ACDF using structural allograft and an anterior plate.

Results

A total of 269 patients were enrolled and randomly assigned to either CTDR (136 patients) or to ACDF (133 patients). There were no significant differences between the CTDR and ACDF groups when comparing operative time, blood loss, length of hospital stay, or the reoperation rate at the index level. The overall success rate was significantly greater in the CTDR group (85%) compared with the ACDF group (71%) (p = 0.05). In both groups, the mean NDI scores improved significantly by 6 weeks after surgery and remained significantly improved throughout the 24-month follow-up (p < 0.0001). Similarly, the VAS pain scores improved significantly by 6 weeks and remained significantly improved through the 24-month follow-up (p < 0.0001). The range of motion (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 ROM in the ACDF group was significantly reduced by 3 months and remained so throughout the follow-up. Adjacent-level degeneration was also evaluated in both groups from preoperatively to 2-year follow-up and was classified as none, mild, moderate, or severe. Preoperatively, there were no significant differences between groups when evaluating the different levels of adjacent-level degeneration. At the 2-year follow-up, there were significantly more patients in the ACDF group with severe adjacent-level radiographic changes (p < 0.0001). However, there were no significant differences between groups in adjacent-level reoperation rate (7.6% for the Kineflex|C group and 6.1% for the ACDF group).

Conclusions

Cervical total disc replacement allows for neural decompression and clinical results comparable to ACDF. Kineflex|C was associated with a significantly greater overall success rate than fusion while maintaining motion at the index level. Furthermore, there were significantly fewer Kineflex|C patients showing severe adjacent-level radiographic changes at the 2-year follow-up. These results from a prospective, randomized study support that Kineflex|C CTDR is a viable alternative to ACDF in select patients with cervical radiculopathy.

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Richard D. Guyer, Fred H. Geisler, Scott L. Blumenthal, Paul C. McAfee and Bradford B. Mullin

Object

Lumbar arthroplasty is approved in the US for the treatment of degenerative disc disease at 1 level in skeletally mature patients. However, a bias toward older patients (> 45 years of age) who are otherwise indicated for the procedure may exist. In this study, the clinical outcomes of patients from the Charité Investigational Device Exemption (IDE) study were analyzed on the basis of patient age.

Methods

There were 276 patients enrolled in the IDE study of the Charité Artificial Disc who underwent 1-level arthroplasty at either L4–5 or L5–S1, including 71 nonrandomized and 205 randomized individuals. Patient data were analyzed based on age (18–45 years [217 patients, Group 1] compared with 46–60 years [59 patients, Group 2]). Statistical analyses were performed based on 2-year postoperative improvements in Oswestry Disability Index (ODI), 36-item Short Form Health Survey (SF-36), and visual analog scale (VAS) scores (clinical outcome), as well as range of motion (radiographic outcome), and adverse events.

Results

There was no significant difference between the groups with respect to level implanted, operative time, blood loss, changes in ODI and VAS scores or any of the 8 component scores of the SF-36, compared with baseline, at all time points throughout the 24-month follow-up period (p > 0.10). Patient satisfaction was equivalent at 24 months, with 87% satisfaction in Group 1 and 85% satisfaction in Group 2 (no statistical difference). In addition, no significant differences were identified with respect to adverse events including approach related, neurological, technique related, or reoperation.

Conclusions

Although patients > 45 years of age may have comorbidities or contraindications for arthroplasty for a number of reasons, particularly osteopenia, this analysis demonstrates that patients who are indicated for 1-level arthroplasty experience similar clinical outcome, satisfaction, or adverse events compared with their younger counterparts.

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Fred H. Geisler, Richard D. Guyer, Scott L. Blumenthal, Paul C. McAfee, Andrew Cappuccino, Fabien Bitan and John J. Regan

Object

A secondary lumbar surgery at a previously surgically treated level is believed to result in minimal clinical improvement. The clinical results of the CHARITÉ Investigational Device Exemption (IDE) study were analyzed to assess the effect of previous surgery on clinical outcomes following either total disc replacement with the CHARITÉ device or anterior lumbar interbody fusion with a BAK cage and iliac crest autograft.

Methods

Patients with prior microdiscectomy, laminectomy, or minimal medial facetectomy were not excluded from enrollment in the CHARITÉ IDE study. Thus, the following 3 groups were analyzed: all patients treated with the CHARITÉ Artificial Disc, whether randomized or nonrandomized; only patients treated with CHARITÉ devices randomized against patients with BAK devices; and control patients with BAK devices. Each group was further subdivided based on the patients' medical history, whether they had undergone prior surgery (prior surgery group) or had not (no prior surgery group). For all groups, baseline demographics were collected and compared for any potential recruitment bias. Postoperative improvements based on Oswestry Disability Index (ODI), visual analog scale (VAS), and patient satisfaction scores were further collected and statistically analyzed.

Results

For all 3 groups, there were no statistical differences in clinical improvement from 3 months to 2 years postoperatively as measured using ODI and VAS scores between the subgroups (those who had prior surgery and those who did not).

Conclusions

Patients indicated for 1-level lumbar arthroplasty with previous lumbar decompressive surgery can be expected to have similar clinical outcomes to patients undergoing arthroplasty without prior lumbar decompressive surgery. Similarly, candidates for anterior lumbar fusion with prior decompressive surgery may experience similar benefits from the surgical procedure as those without.

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Bryan W. Cunningham, Paul C. McAfee, Fred H. Geisler, Gwen Holsapple, Karen Adams, Scott L. Blumenthal, Richard D. Guyer, Andrew Cappuccino, John J. Regan, Ira L. Fedder and P. Justin Tortolani

Object

One of the goals of lumbar arthroplasty is to restore and maintain range of motion (ROM) and to protect adjacent levels from abnormal motion, which may be a factor in transition syndrome following arthrodesis. In this study, in vitro ROM results were compared with in vivo, 2-year postoperative radiographic ROM evaluations.

Methods

Radiographs of patients enrolled in the CHARITÉ investigational device exemption study were analyzed at baseline and at 2 years postoperatively. The ROM in flexion/extension at the implanted and adjacent levels was measured, normalized, and compared with ROM results obtained using cadaver (in vitro) evaluations.

Results

Preoperative ROM distributions in patients enrolled for arthroplasty or fusion at the L4–5 level was as follows: 28% motion was observed at L3–4, 35% at L4–5 and 37% at L5–S1. Following a one-level arthroplasty at L4–5, the in vivo ROM distribution from L-3 to S-1 at the 2-year time point was 36% at L3–4, 30% at L4–5 and 35% at L5–S1. Following a one-level fusion with BAK and pedicle screws at L4–5, the in vivo ROM distribution from L-3 to S-1 at the 2-year time point was 45% at L3–4, 9% at L4–5 and 46% at L5–S1.

Conclusions

The baseline as well as the 2-year in vivo data confirmed previously published in vitro data. One-level arthroplasty was shown herein to replicate the normal distribution of motion of the intact spine.

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Paul C. McCormick

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Fred H. Geisler, Richard D. Guyer, Scott L. Blumenthal, Paul C. McAfee, Andrew Cappuccino, Fabien Bitan and John J. Regan

Object

Patient selection is perhaps the most important factor in successful lumbar surgery. In this study, the authors analyzed the clinical outcomes of patients enrolled in the CHARITÉ investigational device exemption (IDE) trial who underwent revision surgery after primary total disc replacement with CHARITÉ or an anterior lumbar interbody fusion (ALIF) with placement of a BAK cage and iliac crest autograft. This revision surgery was either a supplemental posterior lumbar fixation or a 360° fusion. Statistical analysis was conducted to compare clinical success in patients who underwent revision surgery with those who did not.

Methods

The patients enrolled in the CHARITÉ IDE study were divided into 6 groups according to treatment and repeated operation status, and their Oswestry Disability Index (ODI) and visual analog scale (VAS) scores at the 2-year follow-up and at baseline were compared. The patients had received the following treatments by group: A) ALIF without reoperation; B) ALIF with conversion to 360° fusion; C) arthroplasty (randomized) without repeated operation; D) arthroplasty with supplemental posterior lumbar fixation; E) arthroplasty (nonrandomized) without repeated operation; and F) arthroplasty (nonrandomized) with supplemental posterior lumbar fixation. Outcome scores in the groups of patients who required revision surgeries (Groups B, D, and F; 23 patients) were compared with the groups that did not require revision surgery (Groups A, C, and E; 299 patients).

Results

Patients who required revision surgery had a significantly lower level of clinical improvement than those who did not. The mean change in ODI score was −53.0% in Groups A, C, and E, but just −12.7% in Groups B, D, and F (p < 0.0001). The mean change in VAS score was −59.1% in Groups A, C, and E, compared to −23.4% in Groups B, D, and F (p < 0.0001). No significant differences were identified in analyzing absolute change in scores and the percentage change. A comparison of outcomes in patients who had undergone arthroplasty without reoperation (Groups C and E) with all patients who had undergone revision surgery (Groups B, D, and F) demonstrated similar results (p < 0.0001).

Conclusions

The 7.1% of patients who underwent a secondary stabilization procedure had poor clinical improvement. This finding may indicate that if the alternative treatment had been the initial treatment, these patients would not have benefited, and further implies a 7.1% rate of imprecision in preoperative evaluation.