1. Jacek Chowaniec 1, Pawel Jarmuzek 4
Long term functional outcomes in total disc arthroplasty (TDA) and anterior cervical disc fusion (ACDF) cohorts - single centre prospective observational study
Dariusz Latka 1, Grzegorz Miekisiak 1,2, Kajetan Latka 1, Tomasz Olbrycht 1,
Jacek Chowaniec 1, Pawel Jarmuzek 4
1 Department of Neurosurgery, University Hospital in Opole, Poland
2 Department of Neurosurgery, Specialist Medical Center in Polanica-Zdroj, Poland
3 Specialist District Neurological Centre, Opole, Poland
4 Department of Neurosurgery, University Hospital in Zielona Gora, Poland

2. Department of Neurosurgery
University Hospital
in Opole, Poland

3. Disclosure
We have nothing to disclose

4. Introduction Degenerative changes of cervical spine
pathologies of spine
intervertebral discs
intervertebral joints
Degenerative changes of the cervical spine (cervical spondylosis) include pathologies of the spine, intervertebral discs and the intervertebral joints. These changes lead to the compression of neural structures which may eventually manifest with radiculopathy. The most common symptoms of spondylosis are neck pain usually associated with shoulder pain.

5. Disc disease is the main cause of radiculopathy
Incidence of neck pain in population is 15%
Incidence of radiculopathy in population is 0,8%
C6 and C7 levels are most often involved
Degenerative disc disease is one of the main causes of cervical radiculopathy. It is a result of annulus fibrousus degeneration related to aging, which leads to its perforations and tears. The disease primarily affects patients in their 4th and 5th decade of life.
The incidence of neck pain in population is about 15% [1, 25] and radiculopathy about 0,8% [2]. Most often levels of C6 and C7 are involved.
The indications for surgery are: adequate with the diagnostic imaging symptoms persistent for 6-12 weeks and resistant to conservative treatment and progressive motor deficit affecting the normal functions [1].

6. Surgery indications adequate with the diagnostic imaging symptoms
persistent for 6-12 weeks
resistant to conservative treatment
progressive motor deficit affecting the normal functions
The indications for surgery are: adequate with the diagnostic imaging symptoms persistent for 6-12 weeks and resistant to conservative treatment and progressive motor deficit affecting the normal functions [1].

7. Surgery options Anterior cervical discectomy with fusion
Total cervical arthroplasty
Anterior cervical discectomy with fusion was first described 1955 by Robinson and Smith [3, 22], and with few modifications it has become a standard technique used widely in surgical treatment of symptomatic degenerative disc disease. The efficacy of treatment reaches 70-90% [4]. Like any surgery, however, it involves complications. The most problematic seems to be adjacent segment disease (ASD). It is a degeneration of segment adjacent to operated level probably due to changes in distribution of biomechanical forces after fusion [6, 7]. The incidence of ASD ranges from 2-4% per year [8].
An alternative to ACDF may be total cervical arthroplasty, which allows to keep mobility of the operated segment [9, 20].
In order to compare the results of treatment after using both techniques, we conducted a single center, prospective, observational cohort study.

8. Adjacent Segment Disease
PRE-OP
1,5yrs POST-OP
The most problematic seems to be adjacent segment disease (ASD). It is a degeneration of segment adjacent to operated level probably due to changes in distribution of biomechanical forces after fusion [6, 7]. The incidence of ASD ranges from 2-4% per year [8].

9. Solis resorbable cage Prestige LP
Interesting modification of classical ACDF is the resorbable cage application. It is often filled with bone graft substitutes (such as calcium phosphate and/or hydroxyapatite). The purpose of cages is to support the segment while bony fusion is promoted through the central void filled with grafting material.

10. Material and Method single centre prospective observational study
period between November 2004 and March 2009
two cohorts
Shapiro-Wilk test, Mann-Whitney test
This is a prospective outcome analysis of patients who underwent surgery in the Department of Neurosurgery in Opole, Poland in the period between November 2004 and March 2009.
There were two groups of patients. The first group was made of patients who received total disc arthroplasty with Prestige LP implant , and the second was treated with anterior cervical discetomy and fusion using Solis resorbable cage. The treatment method was chosen on surgeons’ discretion.
Data were tested with the Shapiro-Wilk test, which showed that the distribution of data is not normal. Further analysis was performed using Mann-Whitney test.

11. exclusion criteria for TDA group
lack of intraoperative mobility of the operated segment
not fully randomised

12. Surgical Techinique Smith-Robinson anterior approach
microscope magnification
Solis resorbable cage (Stryker)
Prestige LP (Medtronic)
All patients were operated at the Department of Neurosurgery in Opole. The surgical procedures were performed via a Smith-Robinson anterior approach. For discectomy the microscope was used in all cases. Each patient received either the Solis resorbable cage implant (Stryker) (ACDF group) or Prestige LP (Medtronic) cervical disc prosthesis (TDA group) were implanted.

13. ACDF group n=90 36 male 54 female av. age 51,2 level C3/C4 3 C4/C5 1255
C6/C7 38
In ACDF group were 36 male and 54 female patients, the average age was 51,2 (SD 5,8). In 72 patients one level was treated, in 18 two levels. 55 patients were operated on C5/C6 level, 38 on C6/C7, 12 on C4/C5 and 3 on C3/C4.

14. TDA group n=88 19 male 69 female av. age 41,9 level C3/C4 2 C4/C5 662
C6/C7 27
19 male
69 female
av. age 41,9
There were 19 male and 69 female patients in the TDA group, the average age was 41,9 (SD 7,2). In 79 patients one level was treated, in 9 two levels. 62 patients were operated on C5/C6 level, 27 on C6/C7, 6 on C4/C5 and 2 on C3/C4.

15. followed and compared after 3, 6, 12, 48 and long-term
long-term av. 8yrs
functional evaluation:
Neck Disability Index (NDI)
Visual Analog Scale (VAS) for neck and arm pain
EuroQol questionnaire
Both cohorts were clinically followed and compared at 3, 6, 12, 48 and long-term (average 8yrs). Functional evaluation included the Neck Disability Index (NDI), visual analog scale (VAS) scores for neck and arm pain and EuroQol questionnaire (both EQ-VAS and EQ-5D3L).

16. Follow up
ACDF 49,89%
TDA 44,31%
In the TDA group long-term attrition was 44,31% while in the ACDF group 51,11% of patients were lost to follow-up for undetermined reasons.

17. Adjacent Segment Disease
17 reoperations
ACDF group- 13 cases
TDA group- 4 cases
av. interval 82,5 months
RR (95%CI   to 0.9280)
Over the course of follow up there were 17 reoperations caused by the adjacent segment disease. Fourteen cases belonged to the ACDF group and the average interval between operations was 24 months. In the TDA group, three patients underwent subsequent surgeries and the average interval was 82.5 months.

18. Results
The patient-reported outcomes were similar in both cohorts particularly in regard to the EQ-VAS as well as neck/arm-VAS scores. All patients showed statistically significant improvement on all follow-up evaluations performed routinely at 3, 6, 12 ,24 months and at the long term follow-up. The favorable outcome was observed with the EQ-5D index, EQ-VAS and NDI

19. The only noteworthy difference in functional outcome in TDA and ACDF groups is EQ-5D index at 6 months: 0.79 for TDA in compare to 0.85 for ACDF group, nut the difference was not statistically significant (p>0.05). This is also true with the difference in mean value of VAS neck pain intensity and frequency scores at the same evaluation period: 7.1 and 5.6 respectively. Again, the difference was not statistically significant (p>0.05).

20. better results after using TDA: better functional outcomes, fewer adverse events and fewer secondary surgical procedures
Jiang H, Zhu Z, Qiu Y, et al. Cervical disc arthroplasty versus fusion for single-level symptomatic cervical disc disease: a meta-analysis of randomized controlled trials. Arch Orthop Trauma Surg. 2012;132:141–151
Jiaquan Luo, Ming Gong, Sheng Huang, Ting Yu, and Xuenong Zou Incidence of adjacent segment degeneration in cervical disc arthroplasty versus anterior cervical decompression and fusion meta-analysis of prospective studies Arch Orthop Trauma Surg. 2015; 135: 155–160
Yujie Zhang, Chengzhen Liang, Yiqing Tao, Xiaopeng Zhou, Hao Li, Fangcai Li, Qixin Chen Cervical Total Disc Replacement is Superior to Anterior Cervical Decompression and Fusion: A Meta-Analysis of Prospective Randomized Controlled Trials PLOS ONE | DOI: /journal.pone March 30, 2015
Si Yin MD, Xiao Yu MD, Shuangli Zhou MD, Zhanhai Yin PhD, Yusheng Qiu PhD Is Cervical Disc Arthroplasty Superior to Fusion for Treatment of Symptomatic Cervical Disc Disease? A Meta-Analysis Clin Orthop Relat Res (2013) 471:1904–1919
The superiority of TDA vs. ACDF has been an issue of great controversy for years. Recently, in fact, a number of studies have suggested better results after using TDA in some aspects [15, 17, 23, 24] such as: better functional outcomes, fewer adverse events and fewer secondary surgical procedures. It should be noted that the differences were very small, and the follow-up was up to 5 yrs.

21. no superiority of either of the techniques
Verma K, Gandhi SD, Maltenfort M, et al. Rate of adjacent segment disease in cervical disc arthroplasty versus single-level fusion: meta-analysis of prospective studies. Spine. 2013;38(26):2253–2257
Rahul Basho, Kenneth A. Hood, Cervical Total Disc Arthroplasty Global Spine J 2012;2:105–108
Rishi D. S., Nandoe Tewarie, Ronald H. M. A. Bartels Wilco C. Peul Long-term outcome after anterior cervical discectomy without fusion Eur Spine J (2007) 16:1411–1416
In our study we were unable to demonstrate superiority of either of the techniques.This observation is consistent with previous publications [16, 20, 21].

22. hypermobility of the operated segment which can lead to an increased neck pain in early follow up ??
The only difference between groups was noted in the functional outcome expressed as the EQ-5D index at 6 months (FIG. 1) in favor of ACDF. Analogously same is valid for the VAS neck pain intensity and frequency scores at 6 months (FIG. 4). A plausible explanation would be a relative hypermobility of the operated segment which can lead to an increased neck pain. As the operated segment heals over time worse outcome is not observed at longer follow-ups. We have to admit that we did not find a similar thesis in the literature review.

23. ASD reoperations 1.9%/level/yrs in ACDF group
2.9%/level/yrs* *Hilibrand AS, Carlson GD, Palumbo MA, et al. Radiculopathy and myelopathy at segments adjacent to the site of a previous anterior cervical arthrodesis. J Bone Joint Surg Am. 1999;81:519–28
0.6%/level/yrs in TDA group
The frequency of re-operation related to appearance of ASD in our study was 1.9% / level / yr in the ACDF group. It is slightly lower than in the classic study of Hilbrand - 2.9% / level / yr [13]. This is probably due to the evolution of surgical techniques and imaging methods over the past 20 years. In the case of TDA we achieved a significantly lower score - 0.6% / level / yr. A lower incidence of ASD after using TDA has also been demonstrated in a meta-analysis of Jiang et al. [15], but the author himself points out that the quality of included studies were of low quality. To similar conclusions came Luo et al. in their meta-analysis of eight prospective studies[17]. He showed that the frequency of ASD in ACDF group was 1.31% /year and 0.49% / year in TDA group. However, the follow-up time was only 24 months. In a recent meta-analysis of six prospective studies Verma et al. [16] showed that the occurrence of ASD after ACDF is 2.4% / year (st. dev. 1.7), and TDA 1.1% / per year (st. dev. 1.5). The time of follow-up was 5 years. This difference was statistically insignificant, which indicates that frequency of the ASD in both groups is the same.

24. Conclusion
Our study reveals that the use of resorbable cage (Solis) in anterior cervical discetomy and fusion can be as effective as the total disc arthroplasty for the treatment of symptomatic cervical disc disease in terms of either early or long term functional outcomes
TDA provides the decrease of the incidence of adjacent segment degeneration requiring further surgery compared to ACDF
Our study reveals that the use of resorbable cage (Solis) in anterior cervical discetomy and fusion can be as effective as the total disc arthroplasty for the treatment of symptomatic cervical disc disease in terms of either early or long term functional outcomes. What is more interesting in mid-term evaluation we have even observed slightly better functional results in ACDF cohort. This is probably due to the presence of increased axial pain related to neck hypermobility in TDA group. However, in our study TDA provides the decrease of the incidence of adjacent segment degeneration requiring further surgery compared to ACDF, what remains still unclear in other literature reports.

25. Department of Neurosurgery
University Hospital
in Opole, Poland