Fred H. Geisler, MD PhD,1 Paul C. McAfee, MD,2 Robert J. Banco, MD,3 Scott L. Blumenthal, MD,4 Richard D. Guyer, MD,4 Richard T. Holt, MD,5 Mohamed E. Majd, MD5
1Illinois Neuro-Spine Center, Aurora, IL 2Spine and Scoliosis Center, Towson, MD 3Boston Spine Group, Boston, MA 4Texas Back Institute, Plano, TX 5Spine Surgery, Louisville, KY
Candidates for spinal arthrodesis or arthroplasty often present with a history of prior surgery such as laminectomy, laminotomy or discectomy. In this study, lumbar arthroplasty patients with prior surgery, and in particular patients with prior discectomy, were evaluated for their clinical outcomes at the 5-year time point.
Randomized patients from the 5-year CHARITÉ investigational device exemption (IDE) study were divided as follows: 1) fusion prior surgery (excluding prior decompression with fusion) group (FSG); 2) fusion prior discectomy group (FDG); 3) fusion no prior surgery group (FNG); 4) arthroplasty prior surgery group (ASG); 5) arthroplasty prior discectomy group (ADG); and 6) arthroplasty no prior surgery group (ANG). The 5-year clinical outcomes included visual analog scale (VAS), Oswestry Disability Index 2.0 (ODI), patient satisfaction, and work status.
In the arthroplasty group, all subgroups had statistically significant VAS improvements from baseline (VAS change from baseline: ASG=-36.6±29.6, P0.0001; ADG=-40.2±30.9, P=0.0002; ANG=-36.5±34.6, P0.0001). There was no statistical difference between subgroups (P=0.5587). In the fusion group, VAS changes from baseline were statistically significant for the FNG and FSG subgroups, but not for the FDG patients (FNG=-46.3±28.8, P0.0001; FSG=-24.2±36.4, P=0.0444; FDG=-26.7±38.7, P=0.2188). A trend of decreased VAS improvements was observed for FSG versus FNG (P=0.0703) subgroups. Similar findings and trends were observed in ODI scores (Changes in ODI from baseline: ASG=-20.4±23.8, P0.0001; ANG=-26.6±21.1, P0.0001; ADG= -17.6±28.6, P=0.0116; FSG=-14.5±21.2, P=0.0303; FNG= -32.5±22.6, P0.0001; FDG=-10.7±9.4, P=0.0938). The greatest improvement in work status from preoperative to postoperative was seen in the ADG subgroup (28% increase in part- and full-time employment), while the FDG subgroup showed the greatest reduction in work status (17% decrease).
Arthroplasty patients with prior surgery or prior discectomy had similar clinical outcomes as arthroplasty patients without prior surgery, while fusion patients with prior surgery or prior discectomy showed trends of lowered clinical outcomes compared to fusion patients without prior surgery or discectomy.
The development of new spinal arthroplasty devices has prompted multiple level I randomized controlled trials to evaluate the clinical impact of arthroplasty versus fusion in controlled patient populations.1., 2., 3., 4. While these studies are creating a wealth of information on the safety and effectiveness of various devices for the treatment of degenerative disc disease (DDD), their indication is usually restricted to a very narrowly defined patient population and, as such, they provide only limited information on the critical issue of patient selection for either fusion or arthroplasty.
A prior CHARITÉ (DePuy Spine, Raynham, Massachusetts) investigational device exemption (IDE) study, which was designed to evaluate the Artificial Disc versus BAK (Zimmer Spine, Minneapolis, Minnesota) interbody fusion with iliac crest autograft for the treatment of degenerative disc disease at 1 level from L4 to S1, also included strict inclusion and exclusion criteria that ensured a homogeneous patient population.1,3 However, the study design allowed inclusion of patients with prior laminectomies, foraminotomies or discectomies. At the 2-year time point, all the patients were analyzed and it was found that those who had undergone a prior surgery experienced similar benefits from their spinal surgery as those who had not had a prior surgery.5 No information exists, however, on the long-term benefits of fusion and arthroplasty on this specific (prior surgery) patient population.
The long-term clinical benefits of spinal fusion have been discussed in multiple reports.6,7 Long-term arthroplasty results have also been the subject of several publications8,9; however, the information included in these reports represents level IV data as none of the studies were based on multicenter, randomized controlled cases. Recently, the 5-year results from the artificial disc versus interbody fusion study were compiled, providing long-term efficacy data—for both fusion and arthroplasty—from a multicenter, randomized controlled trial. Our study of the 5-year results provides a unique opportunity to understand the long-term impact of both fusion and arthroplasty on specific patient populations, such as patients with prior surgery as well as patients with prior discectomy.
In this study, both the arthroplasty and fusion patient populations were subdivided based on the patients’ history of prior surgery or prior discectomy. The prior surgery patient subgroups were compared to the subgroups without prior surgery or discectomy.
Between May 2000 and April 2002, 375 patients were randomized for treatment by either anterior lumbar fusion with the interbody fusion system and iliac crest autograft or total disc replacement with the artificial disc as part of a prospective, randomized, non-blinded, FDA-approved IDE study conducted at 14 investigational sites across the United States. At the completion of the 2-year study, a new investigation was initiated to further collect data from this study, up to the 5-year time point. All 14 sites were invited to participate; however, 6 sites declined continuation, reducing the number of available patients by 90. A total of 160 patients presented for their 5-year follow-up: 43 interbody fusion patients, 90 randomized arthroplasty cases, and 27 non-randomized (training) arthroplasty cases. Randomized cases only are included in this analysis. Patients were subdivided by prior surgery history as shown in Table 1. Prior surgery was not an exclusion criterion for the IDE study, as long as it was defined as prior decompressions via discectomy or laminotomy/foraminotomy without fusion. Prior decompression with fusion, on the other hand, was listed as an exclusion criterion. Patients in this study, therefore, do not include cases with prior fusion surgery. Of the 90 arthroplasty patients, 37 had prior surgery of which 21 had prior discectomy. Of the 43 fusion patients, 12 had prior surgery of which 6 had prior discectomy. The groups are defined as arthroplasty prior surgery group (ASG) and fusion prior surgery (excluding prior fusion) group (FSG); arthroplasty prior discectomy group (ADG) and fusion prior discectomy group (FDG); and arthroplasty no prior surgery group (ANG) and fusion no prior surgery group (FNG).
|Demographics||Prior Surgery||Discectomy||No Prior Surgery||Prior Surgery||Discectomy||No Prior Surgery|
|Number of Subjects||37||21||53||12||6||31|
|Female||14 (38%)||9 (43%)||29 (55%)||6 (50%)||3 (50%)||13 (42%)|
|Male||23 (62%)||12 (57%)||24 (45%)||6 (50%)||3 (50%)||18 (58%)|
|Mean (Std)||38.4 (8.48)||40.1 (8.64)||41.0 (8.57)||35.3 (5.89)||37.8 (5.56)||40.2 (9.28)|
|Min, Max||19, 55||20, 55||21, 60||25, 43||28, 43||25, 55|
|Mean (Std)||175.4 (8.72)||174.5 (9.09)||172.5 (9.86)||172.5 (9.71)||173.1 (10.46)||173.8 (8.77)|
|Min, Max||157, 193||157, 191||150, 191||155, 185||155, 185||157, 191|
|Mean (Std)||80.8 (17.73)||79.3 (17.59)||79.4 (14.97)||83.1 (14.04)||80.8 (19.31)||81.0 (16.71)|
|Min, Max||51, 120||51, 120||52, 111||54, 109||54, 109||54, 118|
|Body Mass Index|
|Mean (Std)||26.1 (4.45)||25.9 (4.71)||26.6 (3.92)||28.1 (5.13)||27.0 (6.31)||26.7 (4.69)|
|Min, Max||19, 34||19, 33||17, 37||19, 36||19, 36||19, 40|
|L4-5||10 (27%)||4 (19%)||16 (30%)||5 (42%)||3 (50%)||5 (16%)|
|L5-S1||27 (73%)||17 (81%)||37 (70%)||7 (58%)||3 (50%)||26 (84%)|
Comparisons of clinical outcomes between patients with prior surgery, prior discectomy or no prior surgery were performed using VAS (0–100) and ODI scores preoperatively, at 6 weeks, and at 3-, 6-, 12-, 24- and 60-months postoperative. At 12-, 24-and 60-months postoperative, additional analyses were conducted to compare patient satisfaction and return to work status between groups.
Data were analyzed using the SAS v8.2 statistical software package (SAS Institute, Cary, North Carolina). For categorical variables, P values were generated using Fisher's exact test. A t test was used to test means.
Demographic information was compiled and compared for all groups, as shown in Table 1. No statistical difference was observed between groups. In the arthroplasty group, a majority of females had prior surgery or prior discectomy. This trend was not observed in the fusion group. Average age, height, weight, and BMI were also not statistically different between groups. A majority of patients were treated at L5-S1 in all groups except the FDG, where the same number of procedures was performed at both L4-L5 and L5-S1.
Surgical times, blood loss and hospitalization days are shown in Table 2. There were no statistical differences for these variables between the prior surgery/prior discectomy subgroups and the no prior surgery patients in both the fusion and arthroplasty groups. In the arthroplasty group, patients with prior surgery or discectomy showed trends of reduced surgical time and blood loss compared to patients with no history of prior surgery. No difference in hospitalization days was found between the 3 arthroplasty subgroups. In the fusion group, a similar trend of reduced surgical time was observed between prior surgery/prior discectomy patients and those patients without prior surgery. However, this trend was reversed with regard to blood loss. There were no differences in hospitalization days among all 3 fusion subgroups.
|Demographics||Prior Surgery||Discectomy||No Prior Surgery||Prior Surgery||Discectomy||No Prior Surgery|
|Total Surgery Time (Min)|
|Mean (Std)||97.5 (29.44)||95.6 (29.42)||115.6 (53.69)||106.3 (66.58)||81.8 (29.14)||128.2 (66.23)|
|Min, Max||56, 175||56, 175||45, 250||55, 248||62, 137||60, 355|
|Estimated Blood Loss (cc)|
|Mean (Std)||158.3 (143.3)||145.2 (124.65)||248.7 (277.81)||251.6 (440.72)||341.5 (618.46)||186.0 (169.19)|
|Min, Max||50, 600||50, 500||25, 1500||50, 1600||50, 1600||20, 700|
|Duration of Hospital Stay|
|Mean (Std)||3.7 (0.97)||3.8(1.22)||3.7(.86)||4.3(2.50)||3.5(0.55)||4.3(1.47)|
|Min, Max||1, 6||1, 6||2, 6||3, 12||3, 4||2, 8|
VAS scores for both arthroplasty and fusion patients are shown in Figures 1A and 1B. In the arthroplasty group, all subgroups showed similar changes in VAS at all time points. In all arthroplasty subgroups, changes from baseline to 5 years were statistically significant (change from baseline: ASG< =< -36.6< ±< 29.6, P< << 0.0001; ADG< =< -40.2< ±< 30.9, P< =< 0.0002; ANG< =< -36.5< ±< 34.6, P< << 0.0001). In addition, the difference in VAS changes from baseline between the ASG and the ANG subgroups was not statistically significant (P< =< 0.5587). In the fusion group, changes from baseline were also statistically significant for the FNG subgroup (VAS change from baseline: FNG= -46.3< ±< 28.8, P< << 0.0001). However, the VAS improvements from baseline were not statistically significant in the FDG subgroup, and they were barely significant in the FSG subgroup (change from baseline: FSG= -24.2< ±< 36.4, P< =< 0.0444; FDG= -26.7< ±< 38.7, P< =< 0.2188). In addition, the difference in VAS changes from baseline between the FSG and FNG subgroups showed a trend of decreased VAS improvements for FSG (P< =< 0.0703).
Changes in VAS scores for arthroplasty (A) and fusion (B) patients, by time point. The “*” indicates statistical significance compared to the no prior surgery subgroups (ANG or FNG).
VAS improvements were also compared between ANG and FNG, ASG and FSG, as well as ADG and FDG. Despite the fairly large differences in mean scores between the arthroplasty and fusion subgroups, none were statistically significant.
ODI scores for both arthroplasty and fusion patients are shown in Figures 2A and 2B. In the arthroplasty group, all subgroups showed statistical improvements from baseline to 5 years. In addition, there was no statistical difference in ODI improvements between the ANG and ASG subgroups (P< =< 0.2245), and between the ANG and ADG subgroups (P< =< 0.1406). (Changes in ODI from baseline: ASG< =< -20.4< ±< 23.8, P< << 0.0001; ANG< =< -26.6< ±< 21.1, P< << 0.0001; ADG< =< -17.6< ±< 28.6, P< =< 0.0116). In the fusion group, changes from baseline were statistically significant for the FNG subgroup (Changes in ODI: FNG= -32.5±22.6, P< << 0.0001); however, improvements in ODI were not statistically significant in the FDG subgroup and were barely significant for the FSG subgroup (FDG< =< -10.7< ±< 9.4, P< =< 0.0938; FSG= -14.5< ±< 21.2, P< =< 0.0303). In addition, there was a statistically significant difference between ODI improvements for the FNG subgroup versus the FSG (P< =< 0.0356), and for the FNG versus the FDG (P< =< 0.0273) subgroup.
Changes in ODI scores for arthroplasty (A) and fusion (B) patients, by time point. The “*” indicates statistical significance compared to the no prior surgery subgroups (ANG or FNG)
ODI improvements were also compared between the subgroups ANG and FNG, ASG and FSG, as well as ADG and FDG. Again, despite fairly large differences in mean scores, none were statistically significant.
The return to work status by treatment group and time point is shown in Figure 3. The greatest improvement in work status from preoperative to postoperative was seen in the ADG subgroup: Improvement in work status reached 7%, 25% and 28% in the ANG, ASG and ADG subgroups, respectively. In the fusion group, improvement in work status from preoperative to 5-year postoperative was observed only in the FSG subgroup (42% to 50%); it declined in the FNG (62% to 61%) and FDG subgroups (67% to 50%).
At the 5-year postoperative time point, there were 26% more ASG patients with full- or part-time work versus FSG patients, and there were 16% more patients with full- or part-time work in the ADG subgroup versus the FDG. In the no prior surgery subgroups, there was only a 9% difference between arthroplasty and fusion subjects in terms of work status.
Patient satisfaction with the procedure at 12-, 24- and 60-months is shown in Figure 4. At the 5-year time point, patient satisfaction ranged from 81% (ADG) to 97% (ANG). There were no statistical differences in patient satisfaction at that time point.
Percentage of patients who were “satisfied” or “somewhat satisfied” with the procedure at the various time points and by subgroups.
The purpose of this study was to analyze the clinical outcomes of arthroplasty and fusion patients with and without prior surgery or prior discectomy. Only randomized cases were included herein. Overall, arthroplasty patients with prior surgery or prior discectomy experienced clinical outcomes that were similar to those experienced by arthroplasty patients without prior surgery or prior discectomy. However, fusion patients who had undergone prior surgery or prior discectomy experienced smaller pain and disability improvements (as measured by VAS and ODI) compared to fusion patients without prior surgery or prior discectomy.
In all subgroups, average differences in outcomes at the 5-year time point exceeded the minimum clinically important differences (MCID) established for VAS (18–19mm) and ODI (10 points).10 In the arthroplasty group, VAS improvements were twice the MCID for all subgroups, while ODI improvements were twice the MCID for the ANG and ASG subgroups but not the ADG. In the fusion group, VAS and ODI improvements were twice the MCID for the FNG but not for the FSG and FDG subgroups, in which VAS and ODI improvements barely reached the MCID threshold.
The return to work percentage was also greater in the arthroplasty group than in the fusion group. This finding was already apparent in the overall IDE 5-year follow-up,11 which showed a statistically greater percentage of arthroplasty patients returning to work versus fusion patients. In our current analyses, while statistical significances were not shown, fusion patients with prior discectomy and prior surgery experienced the lowest rates of return to work. In comparison, arthroplasty patients with prior surgery had the greatest rate of return to work.
Despite the small sample size in the fusion prior surgery and fusion prior discectomy group, these results may further question whether such procedures (eg, decompressions with laminotomy/foraminotomy or discectomy) should be considered contraindications for subsequent fusion procedures with BAK and iliac crest autograft.
Limitations of this study include the unequal distribution of patients across the groups analyzed, the loss of patients to follow-up and the subsequent small sample sizes at the 5-year time point. It is possible that among the loss to follow-up patients are patients who have brought legal claims for personal injuries rather than continuing in the study. Due to lack of information and other constraints, we are not presently able to determine the significance of these patients’ outcomes to the study. This is in part due to the fact that the IDE study was initially designed for a 2-year follow-up. Thus, while all of the 14 sites involved in the initial 2-year IDE trial were invited to participate in the 5-year follow-up, 6 declined continuation. Since all sites initially signed up for a 2-year study, they were under no obligation to pursue the investigation beyond the 2-year time point. The resulting small patient samples, especially in the prior discectomy subgroups, prevented in-depth statistical analyses.
Arthroplasty patients with or without prior surgery or prior discectomy experienced, on average, significant clinical improvements from their surgery. All subgroups exceeded MCID values for mean VAS and ODI improvements, and in most cases, they showed a clinical improvement equal to twice the MCID values.
Similarly, all fusion patients met, on average, the MCID values for VAS and ODI. However, the prior surgery and prior discectomy subgroups showed trends of reduced clinical outcomes as compared to fusion patients without prior surgery or discectomy. Fusion patients with prior discectomy and prior surgery had the lowest rate of return to work.
The authors thank Brian Hetzell and George DeMuth from Stat-Tech Services for statistical analyses, and Dr. Chantal Holy, Director of Scientific Affairs for DePuy Spine, Inc., for editorial support.
Fred Geisler, PhD, MD, consults for DePuy Spine, Inc., Aesculap, Inc., Abbott Spine, K2M, and Spinal Motion; receives royalties from DePuy and Aesculap; and owns stock in Disc Motion and Impliant, Inc. Paul McAfee, MD, owns stock in, consults for, and has received research support from DePuy Spine, Inc., Cervitech, Inc., and Globus Medical, Inc. Robert Banco, MD, is a consultant for DePuy Spine, Inc., Stryker Corporation, Medtronic, Inc., and Impliant, Inc. Richard Guyer, MD, is a consultant to and receives royalties from DePuy Spine, Inc.Scott Blumenthal, MD, is a consultant to DePuy Spine, Inc. Mohamed E. Majd, MD is a member of the faculty with Stryker Corporation, Alphatec Spine, Inc., and DePuy Spine, Inc.
IRB approval was obtained at each of the participating study sites
Address correspondence to Dr. Fred H. Geisler, Illinois Neuro-Spine Center, 2020 Ogden Avenue, Suite 335, Aurora, IL 60504.