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Patient-reported Outcomes and Revision Rates at a Mean Follow-up of 10 Years After Lumbar Total Disc Replacement

Laugesen, Line A. MSc*,†; Paulsen, Rune T. MD*,†; Carreon, Leah MD, MSc*,†; Ernst, Carsten MD*; Andersen, Mikkel Ø. MD*,†

doi: 10.1097/BRS.0000000000002174
Outcomes
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Study Design. Prospective observational cohort study.

Objective. The aim of this study was to determine the long-term clinical results and prosthesis survival in patients treated with lumbar total disc replacement (TDR).

Summary of Background Data. Fusion has become the current standard surgical treatment for lumbar degenerative disease. TDR is an alternative treatment that seeks to avoid fusion-related adverse events, specifically adjacent segment disease.

Methods. Sixty-eight consecutive patients treated with TDR from 2003 to 2008 were invited to follow-up and complete a Visual Analog Scale (VAS) for back and leg pain, the Dallas Pain Questionnaire (DPQ), and the Short Form-36. These surveys were also administered to the subjects before their index TDRs. Data on reoperation were collected from the patients’ medical records.

Results. Fifty-seven (84%) patients were available for follow-up at a mean 10.6 years post-operatively (range 8.1–12.6 years). There was a significant improvement from preop to latest follow-up in VAS (6.8 vs. 3.2, P < 0.000) and DPQ (63.2 vs. 45.6, P = 0.000) in the entire cohort. Nineteen patients (33%) had a revision fusion surgery after their index TDR. Patients who had revision surgery had statistically significant worse outcome scores at last follow-up than patients who had no revision. Thirty patients (52.6%) would choose the same treatment again if they were faced with the same problem.

Conclusion. This study demonstrated significant improvement in long-term clinical outcomes, similar to previously published studies, and two-thirds of the discus prostheses were still functioning at follow-up. However, there is still a lack of well-designed long-term studies, thus requiring further investigation.

Level of Evidence: 3

*Center for Spine Surgery & Research, Region of Southern Denmark, Middelfart, Denmark

Department of Clinical Research and Institute of Regional Health Research, University of Southern Denmark, Odense C, Denmark.

Address correspondence and reprint requests to Line A. Laugesen, MSc, Center for Spine Surgery and Research Østre Hougvej 55, 5500 Middelfart, Denmark; E-mail: line.adsboll.laugesen@rsyd.dk

Received 25 August, 2016

Revised 14 December, 2016

Accepted 6 March, 2017

The manuscript submitted does not contain information about medical device(s)/drug(s).

No funds were received in support of this work.

Relevant financial activities outside the submitted work: board membership, consultancy, grants, employment, travel/accommodations/meeting expenses.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Website (www.spinejournal.com).

Chronic low back pain (CLBP) owing to degenerative disc disease (DDD), unresponsive to nonoperative care, is treated with fusion as the surgical criterion standard.1–10 This approach rests on the hypothesis that the back pain is motion-related. The aim of fusion is to reduce pain by reducing motion and load on the degenerative segmental level.1,5,9,11 However, a potential consequence of fusion is return of symptoms owing to adjacent segment disease (ASD).1,2,4,6–8,10–17 Other adverse events have also been reported, such as considerable complication and reoperation rates, facet and iliosacral joint complaints, narrowing of the spinal canal owing to facet hypertrophy, negatively altered sagittal alignment, and graft site morbidity among others.4,8,10,14,17 An alternative to fusion is total disc replacement (TDR),1–5,7–10,12–15,17–20 based on the hypothesis that CLBP originating from DDD is because of leve-specific pain in the disc.5,20 This approach aims to reduce pain and maintain intervertebral movement in the lumbar spine, consequently reducing the risk of ASD by putting less stress on the adjacent segments.1–6,12,13,15–17,19 Nevertheless, TDR has also been associated with complications such as malposition, subsidence, spontaneous fusion, and excessive loads to the surrounding ligamentous structures and facet joints.1,4,8 For these reasons, there has been much debate regarding the use and effectiveness of TDR, not only regarding the above-mentioned issues, but also regarding the survival of the prosthesis.

To date, the efficacy of lumbar TDR has not been investigated sufficiently. There are many reports on short-term clinical outcomes and motion analysis after lumbar TDR.19 Previously published long-term follow-ups on lumbar TDR are scarce.1,2,8,17 The purpose of this study was to perform a long-term follow-up of patients treated with TDR owing to DDD, by examining pre- and postoperative health-related questionnaires, and assess the survival of the prostheses.

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MATERIALS AND METHODS

This study is a longitudinal cohort study with a 10.6 years’ (8.1–12.6 years) clinical follow-up, including general and disease-specific measure of health-related quality of life questionnaires and assessment of disc survival. The postoperative data were analyzed and compared to corresponding preoperative data.

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Patients

After receiving approval from The Ethical Committee, Denmark, a consecutive series of 71 patients treated with ProDisc II TDR (Synthes, Paoli, PA) in the lumbar spine at Esbjerg Hospital by 2 surgeons from 2003 to 2008 were identified. Indication of TDR was DDD diagnosed on MRI, showing “black disc,” annulus rupture, or Modic changes. Patients with spondylolisthesis or spondylolysis were excluded.

Of the 71 patients, three patients died because of unrelated causes, leaving 68 patients available for follow-up. Four patients declined to participate and two were lost to follow-up. The remaining 62 patients agreed to participate and were enrolled. Five patients did not return the questionnaires and were subsequently lost to follow-up. This left 57 patients available for follow-up.

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Questionnaires (Visual Analog Scale, Dallas Pain Questionnaire, and 36-Item Short Form Health Survey)

Visual Analog Scale

The Visual Analog Scale (VAS) (scored from 0% to 100%)21 was administered to the subjects before surgery and at latest follow-up. Six variables were analyzed: VAS back pain now (VAS BPN), VAS worst back pain during the last 14 days (VAS BPW), VAS average back pain during the last 14 days (VAS BPA), VAS leg pain now (VAS LPN), VAS worst leg pain during the last 14 days (VAS LPW), and VAS average leg pain during the last 14 days (VAS LPA).

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Dallas Pain Questionnaire

The Dallas Pain Questionnaire (DPQ) was used to assess the functional status of low back pain of the patients. DPQ is a 16-item visual analog tool consisting of 16 visual analog scales, assessing the percentage effects (0% to 100%) of chronic pain on four aspects of a patient's life: daily activities (DPQ D), profession (DPQ P), anxiety and depression (DPQ AD), and sociability (DPQ S).22,23

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36-Item Short Form Health Survey

Evaluation of the health-related quality of life after lumbar TDR was carried out using the 36-Item Short Form Health Survey version 1 (SF-36). SF-36 is a 36-item questionnaire assessing eight health domains (physical functioning, bodily pain, role limitations owing to physical health, role limitations owing to personal or emotional problems, emotional well-being, social functioning, energy/fatigue, and general health perception). These eight domains can be summarized into two summary scores: the physical component summary (PCS) and the mental component summary (MCS).24,25

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Additional Questions

Additionally, the patients were asked whether they would choose the same treatment again if they were faced with the same problems. The answers were measured at a 5-point scale (definitely yes, probably yes, not sure, probably not, and definitely not).

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Disc Survival

Survival of the prosthesis was defined as no need for reoperation (fusion revision surgery). To assess the disc survival, reoperation rates and date of reoperation were collected.

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Statistical Analysis

Data were analyzed using STATA/IC 14.1 with P set at 0.05. Paired student t test was used to examine the differences in continuous variables between baseline and follow-up scores within each group. Baseline and follow-up data for the subgroups (nonfusion and fusion group) were compared by using unpaired student t test. Chi-square test was used to test for differences in categorical variables.

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RESULTS

Out of 68 available patients, 57 patients were enrolled in the study, resulting in a follow-up rate of 84%. Mean patient age at the final follow-up was 49.6 years (34.5–79.0), and the follow-up was conducted at mean 10.6 years (8.1–12.6 years) postoperatively. The majority of patients had single-level TDR (36, 63%) followed by two-level TDR (20, 35%) (Table 1). For the entire cohort, there was a statistically significant improvement in all outcome scores, except for DPQ-AD, DPQ-S and SF-36 MCS. The DPQ-S remained statistically unchanged, whereas the DPQ-AD and SF-36 MCS score was worse (Table 2).

TABLE 1

TABLE 1

TABLE 2

TABLE 2

Of 57 patients, 19 patients (33%) had revision surgery at follow-up. Mean time from TDR to reoperation was 3.5 years (0.5–8.8 years), with a total of 23 segments revised (Table 3). There were no differences seen between the revision versus no revision groups in terms of demographics, surgical data (Table 3), and baseline clinical outcome measures (Table 4), except for VAS BP, which was significantly lesser for the no revision group than the revision group. Patients who did not have a fusion procedure after their TDR had better clinical outcomes at latest follow-up, except for DPQ-AD, which was similar between the groups and SF-36 MCS, which were worse for the no revision group than for the revision group.

TABLE 3

TABLE 3

TABLE 4

TABLE 4

Thirty patients (52.6%) stated that they would choose the same treatment again if they were faced with the same problem. Seven patients (12.3%) would probably choose the same treatment again, seven patients (12.3%) would probably or definitely not choose the same treatment again, and 13 patients (22.8%) were indecisive (SDC Table 6, http://links.lww.com/BRS/B268). The distribution of responses between the revision and no revision groups was not statistically significantly different (P = 0.730).

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DISCUSSION

Several publications on clinical outcomes after lumbar TDR have been reported2,6–10,14,16–18,20 including results from randomized controlled trials comparing TDR to fusion1,3,13 and systematic reviews and meta-analyses on the topic.26–29 However, the number of studies on the long-term efficacy of TDR are still limited. This study aims at assessing the long-term clinical outcomes after TDR with ProDisc II.

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Clinical Outcomes

Several short-term and mid-term studies on TDR have reported statistically significant improvement in clinical outcomes after TDR.2,6,7,9,10,14,18,19 Scott-Young et al18 reported statistically significant improvements in VAS, Oswestry Disability Index (ODI), and SF-36 PCS. Park et al2 also reported significant improvement in VAS, ODI, and SF-36 at all follow-up stages compared to baseline. However, they observed a maximal effect at 2 years’ follow-up and a slight decline in outcome at the last follow-up compared to 2 years’ follow-up. In addition, Lazennec et al14 found an early significant improvement of VAS at 3 months and at 6 months for ODI. VAS and ODI remained stable hereafter.

A number of randomized controlled trials have reported similar result after TDR compared to fusion at short-term follow-up.1,3,13 Clinical outcomes improved significantly at follow-up compared to baseline for both groups, suggesting either TDR or fusion as treatment option for patients with DDD.1,3 Berg et al13 found a better outcome at 1-year follow-up for patients treated with TDR, whereas patients treated with fusion improved during the second year postoperatively, although TDR had a larger number of pain-free patients at all follow-up stages. Furthermore, the majority of systematic reviews and meta-analyses reported superior or equal improvement in clinical outcomes after TDR compared with fusion.26,28,29 However, Hiratzka et al27 were unable to make a clear recommendation of TDR over fusion, owing to an inadequate and high variation in reporting of adverse events following TDR and fusion.

In a long-term study, Siepe et al17 found a highly significant improvement of VAS and ODI at all follow-up stages after TDR compared to baseline scores. ODI remained stable throughout the entire follow-up period, but a slight deterioration of VAS at the last follow-up was reported, although VAS was still well below baseline level. Other long-term studies have reported similar results with significant improvement in VAS and ODI and overall excellent clinical outcomes.8,16,20

The overall data from this study also reveal highly satisfactory clinical results at follow-up compared to baseline. VAS back pain and leg pain and SF-36 PCS improved significantly at follow-up compared to baseline. The improvement of DPQ D, DPQ P, and DPQ AD was also statistically significant, but DPQ S was not different at follow-up compared to baseline. The SF-36 MCS was worse at follow-up compared to baseline.

Comparing the patients who had a revision with those who did not have a revision, all variables at follow-up, except DPQ AD and SF-36 MCS, were significantly better in the nonfusion group compared to the fusion group (P < 0.05) (Table 5). According to Park et al20 and Siepe et al,17 long-term follow-up is more likely to compromise clinical results. This might explain the less improvement of the variables of the fusion group in relation to its slightly longer follow-up period compared to the nonfusion group. Although the difference in mean follow-up rates between the two groups was little over a year, this was statistically significant. The differences in outcomes between the subgroups might also be because of patient selection before TDR, as patient selection criteria has been clarified since the first TDR in this study was implanted—the patients in the fusion group might not have been appropriate candidates for TDR because of current knowledge.

TABLE 5

TABLE 5

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Additional Outcomes

Our patients’ attitude toward TDR was less positive than reported by Siepe et al17 and Lu et al8 (SDC Table 6, http://links.lww.com/BRS/B268). In Siepe et al's study,17 79.3% of the patients would have the same surgery again if faced with the same condition, 13.0% were unsure, and 7.7% refused. In Lu et al's study,8 78.1% answered “yes,” 15.6% “probably yes,” and 6.3% “definitely not.” The difference might be explained by our revision surgery rate that was higher than reported by Siepe et al.17

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Disc Prostheses Survival

Siepe et al17 reported an overall reoperation rate of 16.0% (2.2% owing to adjacent level disc degeneration). However, no data on the level of reoperation are available. David16 reported a reoperation rate of 7.5% for index-level arthrodesis. These rates are similar to that of Sköld et al’ study.1

In this study, 19 patients (33%) had arthrodesis at index level at mean duration 3.5 years (0.5–8.8 years) after index surgery (Table 2). The relatively higher reoperation rate might be because of patient selection criteria for index surgery; thus, many studies highlight that careful patient selection is essential to ensure best possible outcomes after surgery. Improvements in the use of TDR will be further discussed later in the article.

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Limitations and Forces

SDC Table 7, http://links.lww.com/BRS/B268 summarizes the essentials of four previously published studies (Park et al's, Siepe et al's, Lu et al's, David's16), addressing the long-term clinical outcomes after TDR. The four studies have some limitations in contrary to the current study with regard to study design, patients enrolled, and follow-up duration.

The number of patients enrolled in a study has a vital influence on the outcome. A larger cohort is therefore preferable in terms of whether the cohort is representative or not. In this study, we had a total of 57 patients, similar to that of Park et al's study20 (54 patients). Our patient cohort was larger than that of Lu et al's8 (32 patients), but smaller than that of Siepe et al's17 (181 patients) and David's16 (106 patients). Although Siepe et al's cohort17 had a larger number of patients, our cohort might be more representative in relation to assessment of long-term follow-up given the mean follow-up period. Our study has a mean follow-up period of 10.6 years (8.1–12.6 years), whereas the follow-up period of Siepe et al's study17 was widely spread, including patients with mid-term follow-up (7.4 years [5.0–10.8 years]). Park et al's study20 also had a widespread follow-up duration, although to a lesser extent (mean 10.0 years [5.1–12.0 years]).

Looking at the study design, Park et al's20 and David's studies16 both have a retrospective design, whereas the current study, Siepe et al's17 and Lu et al's studies8 are prospective cohort studies. The lack of control group and randomization can be prescribed to all the studies, including the current study.

The majority of the studies are expressing clinical outcomes in form of VAS and ODI8,17,20. The current study makes use of VAS, DPQ, and SF-36. Preoperative ODI was not available. In the study of David,16 clinical data on functional status were collected using the Stauffer-Coventry Scale. Given the age of the article, VAS, ODI, and SF-36 were neither validated nor in widespread use at the time of these surgical events.

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TDR Improvement

Many improvements have been made in the use of TDR, since the introduction of arthroplasty in the 1980s16,17. Instruments for implanting the prosthesis and imaging of the spine have improved considerably, as well as patient selection criteria have been assessed.16,17 Indications and contraindications for TDR have been outlined, and some outcome-determining factors have been identified.16,17,20 Also tools for assessment of, for example, clinical outcomes have been developed and validated. This given might explain the tendency of older studies to report less favorable outcomes than that of newer studies.17 Siepe et al17 proposed that the current data of long-term follow-ups have to be interpreted as a “worst case scenario” that includes the initial clinical and technical learning curve during the last 2 decades. Therefore application and comparison of current data to future data should only be made carefully and with the current knowledge in mind.17

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CONCLUSION

Encountering the overall improvement in clinical outcomes of this study and other long-term studies, long-term results of TDR are encouraging and indicate that TDR may be an effective alternative in management of lumbar DDD. Thus, proper patient selection is mandatory. To data, there is still a lack of well-designed, long-term evidence, requiring further investigations addressing both clinical and radiological outcomes. In a future study, we will assess radiologic material collected alongside the clinical data in this study.

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Key Points

  • TDR is an alternative surgical treatment for patients with CLBP owing to DDD in the lumbar spine.
  • The study revealed overall satisfactory clinical results with statistically significant improvement in VAS and DPQ (except sociability).
  • Thirty-three percent of the patients had fusion revision surgery at index level at follow-up.
  • The lack of well-designed long-term studies is scarce, thus requiring further studies assessing both clinical and radiological outcomes.
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References

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2. Park CK, Ryu KS, Lee KY, et al. Clinical outcome of lumbar total disc replacement using ProDisc-L in degenerative disc disease: minimum 5-year follow-up results at a single institute. Spine (Phila Pa 1976) 2012; 37:672–677.
3. Zigler JE, Delamarter RB. Five-year results of the prospective, randomized, multicenter, Food and Drug Administration investigational device exemption study of the ProDisc-L total disc replacement versus circumferential arthrodesis for the treatment of single-level degenerative disc disease. J Neurosurg Spine 2012; 17:493–501.
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5. Berg S, Fritzell P, Tropp H. Sex life and sexual function in men and women before and after total disc replacement compared with posterior lumbar fusion. Spine J 2009; 9:987–994.
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Keywords:

alternative surgical treatment; arthrodesis; chronic low back pain; degenerative disc disease; clinical follow-up; disc survival; fusion; lumbar spine; spine arthroplasty; surgical intervention; total disc replacement

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