Key Findings

Figure 1. Two-level Mobi-C


Mobi-C continues to be a safe and effective treatment for 1- and 2-level cervical degeneration.

  • At 10 years, all patient-reported outcomes were equivalent to or improved from 7 years.
  • Between 7-year and 10-year follow-up:
    • C2-C7 range of motion (ROM) and sagittal alignment were maintained.
    • Segmental ROM in flexion/extension and lateral bending was maintained in both 1-level and 2-level constructs.
    • Clinically relevant radiographic adjacent segment pathology (rASP) did not differ significantly in either 1-or 2-level patients.
    • Incidence of motion-restricting heterotopic ossification (HO) did not differ significantly in either 1-level or 2-level patients.
    • No subsequent surgery at an adjacent level after 7 years.

Radiographic Outcomes

From 7-year to 10-year follow-up:

  • Segmental and global ROM and sagittal balance were maintained (Table 1);
  • Clinically relevant (grade 3/4) rASP was not significantly different (Fig. 2), with a 10-year incidence of 21.3% in 1-level patients and 10.2% in 2-level patients;
  • The incidence of motion-restricting HO at 10 years was not significantly different from that at 7 years for 1-level (30.7% vs. 29.6%) or 2-level (41.7% vs. 39.2%) patients.

Table 1. Segmental and global ROM (degrees) in Mobi-C patients through 10 years.

  Flexion/Extension Lateral Bending Global ROM (C2-C6 flexion/extension)
  2-Level Superior 2-Level Inferior 1-Level 2-Level Superior 2-Level Inferior 1-Level 2-Level 1-Level
Prop 8.9 6.8 7.8 5.6 4.9 5.0 37.0 38.8
7 Years 9.4 6.8 9.7 5.1 4.7 5.2 37.9 42.7
10 Years 9.5 6.9 9.3 4.9 4.5 5.1 38.2 41.6
P-value* 0.91 0.97 0.59 0.99 0.99 0.90 0.99 0.19

*10 years vs. 7 years

Figure 2. Progression of clinically relevant rASP throughout folllow-up. ACDF reporting ends at 7 years to completion of the FDA IDE study.

1-Level Mobi-C
2-Level Mobi-C
1-Level ACDF
2-Level ACDF
 

Safety Outcomes

Between 7-year and 10-year follow-up:

  • There were two index level surgeries and no adjacent level surgeries reported after 7 years.
  • The cumulative incidence of subsequent surgery at 10-year follow-up was 4.3% (11/257) at an adjacent level and 5.1% (13/257) at the index level.
  • Seven (7) device-related adverse events (AEs) were reported in five (5) patients (HO = 5, subsidence = 2), but none were classified as serious (i.e., requiring hospitalization or reoperation). Only one patient required an intervention (facet joint injections) due to a device-related AE.

Clinical Outcomes

There was no significant difference (p>0.05) between 1- and 2-level outcomes at 10 years. Therefore, the following refer to analysis of 1- and 2-level patients combined (Table 2):

  • At 10 years, Mobi-C patients continued to have significant improvement in neck disability index (NDI), neck and arm pain, and neurologic function compared to baseline.
  • Furthermore, NDI and pain outcomes at 10 years were significantly improved from 7 years, although these improvements were less than the minimum clinically important difference (MCID) for NDI (15/100) and pain (10/100).
  • Maintenance or improvement of neurologic function from baseline did not differ significantly between 7-year (86%) and 10-year (86.3%) follow-up (p=0.60).
  • Overall patient satisfaction remained very high at 10 years, with the majority of Mobi-C patients reporting they were “very satisfied” (10 years: 88.8% vs. 7 years: 88.0%; p=0.26).

Table 2. Clinical outcomes of 1- & 2-level Mobi-C implants.

Outcome Baseline 7 Years 10 Years Baseline vs. 10-Year
p-value		 7-Year vs. 10-Year
p-value
NDI 54.4 19.3 15.1 <0.0001* 0.003*
Neck Pain 72.1 20.3 13.3 <0.0001* 0.002*
Arm Pain 69.9 15.5 11.3 <0.0001* 0.037*
SF-12 Physical 32.9 45.7 47.5 <0.0001* 0.13
SF-12 Mental 41.6 51.0 51.5 <0.0001* 0.91

*Denotes a statistically significant difference.

Conclusion

Two key advantages of CDA over ACDF are preservation of segmental ROM and reduced incidence of ASP following surgery. Due to the elimination of motion at the treated segment(s), and subsequently increased load and stress on untreated adjacent levels, ACDF can lead to the onset or acceleration of pathologies in adjacent segments. CDA with Mobi-C, on the other hand, has been shown to preserve motion while providing mechanical stability and relief of pain.

Given the emphasis on motion preservation when deciding between CDA and ACDF, two of the biggest concerns following CDA are postoperative development of rASP and motion-restricting HO. In this study, progression of both rASP and HO was minimal between 7- and 10-year follow-up in both 1- and 2-level Mobi-C patients, and no adjacent level surgeries were reported after 7 years. ROM and sagittal alignment were also maintained at 10 years when compared to early postoperative baseline, and patients continued to have significant improvement in clinical and patient-reported outcomes compared to pre-op. Overall results through 10 years were comparable to 7-year outcomes, demonstrating that CDA with Mobi-C continues to be a safe and effective surgical treatment for patients with 1- or 2-level cervical degenerative disc disease.

References

  1. Kim KD, Hoffman GA, Bae H, et al. Ten-Year Outcomes of One and Two Level Cervical Disc Arthroplasty from the Mobi- C IDE Clinical Trial. Neurosurgery 2020;[Online ahead of print]. doi: 10.1093/neuros/nyaa459.
  2. Radcliff K, Davis RJ, Hisey MS, et al. Long-term evaluation of cervical disc arthroplasty with the Mobi-C Cervical Disc: a randomized, prospective, multicenter clinical trial with seven-year follow-up. Int J Spine Surg 2017;11(4):244-262.