Cervical Disc Arthroplasty for the Extra-Mobile Discs

Introduction: Cervical disc arthroplasty (CDA) plays a pivotal role in preserving segmental motion at the index level to mitigate adjacent segment degeneration. The long-term results of US Investigational Device Exemption (IDE) trials spanning a decade have consistently shown positive clinical outcomes and notable motion preservation. However, it remains uncertain whether patients with greater postoperative range of motion (ROM) experience distinct outcomes compared to those with normal postoperative ROM.

Methods: In this retrospective study, we conducted a comprehensive analysis of consecutive patients who underwent CDA at the C5/6 level. The surgical indication for CDA was medically refractory cervical radiculopathy and/or myelopathy, primarily attributed to cervical degenerative disc disease or spondylosis. Patients were categorized into two groups based on their postoperative segmental ROM: individuals with ROM equal to or exceeding 15 degrees were placed in the "extra-mobile" group, while those with ROM less than 15 degrees were classified as the "normal mobile" group. Clinical outcomes were assessed using various metrics, including visual analog scales, the Neck Disability Index, and Japanese Orthopaedic Association Scales. Radiological outcomes, such as heterotopic ossification and adjacent segment disease, were meticulously compared.

Results: The analysis incorporated 114 patients with a follow-up period exceeding 2 years. The "extra-mobile" group comprised 29 patients (mean post-operative ROM= 17.79±2.14°), while the "normal mobile" group included 85 patients (mean ROM= 9.26±4.00°). Demographically, the two groups exhibited similarities, with the exception of the "extra-mobile" group displaying a slightly younger age profile. Notably, both groups demonstrated significant improvements in clinical outcomes, with no statistically significant differences observed between them. The rates of complications were similar in both groups, with no instances of device dislodgement.

Conclusion : This study's findings suggest that postoperative segmental extra-mobility does not compromise the clinical outcomes of CDA. Moreover, the complication profile in "extra-mobile" segments closely aligns with that of "normal mobile" discs, without any device dislodgement events in either group. These results contribute to the growing body of evidence supporting the effectiveness and safety of CDA, regardless of postoperative segmental ROM.