Introduction: Many reports have unanimously demonstrated that cervical disc arthroplasty (CDA) can preserve range of motion after one- or two-level discectomy. However, little data addressed the amount of changes in segmental mobility after CDA or its clinical correlations.
Methods: Consecutive patients who underwent one-level CDA were retrospectively reviewed. Indications of surgery were medical-intractable degenerative disc disease and spondylosis. Clinical outcomes, including visual analog scale (VAS) of neck and arm pain, neck disability index (NDI), Japanese Orthopedic Association (JOA) scores, were analyzed. Radiographic outcomes, including C2-7 Cobb angle, ?C2-7 Cobb angle (the difference between pre- and post-operative C2-7 Cobb angle), sagittal vertical axis (SVA), ?SVA, segmental range of motion (ROM), and ?ROM, were accessed for the association with clinical outcomes. All patients had computed tomography (CT), by which the presence and severity of heterotopic ossification (HO) were thus determined, during the follow up.
Results: A total of 50 patients (mean age 45.6±9.33 year-old) of one-level CDA (Prestige LP disc) were analyzed with a mean follow-up of 27.7±8.76 months. All clinical outcomes, including VAS, NDI, and JOA scores, improved significantly after surgery. Pre- and post-operative ROM were similar (9.5° vs 9.0°, p>0.05) at each indexed level. The mean changes of segmental mobility (?ROM) were -0.5 ± 6.13 degrees. Patients with increased segmental mobility after surgery (?ROM >0°) had less incidences and severity of HO (p=0.048) than those whose ?ROM <0°. Segmental mobility (ROM) was significantly smaller in patients with higher HO grade (p=0.012), but it did not affect the clinical outcomes. The pre- and post-operative C2-7 Cobb angles and SVA remained similar. The post-operative C2-7 Cobb angles, SVA, ?C2-7 Cobb angles, and ?SVA all had no correlation to clinical outcomes after CDA.
Conclusions: Segmental mobility (mean ROM) and overall cervical alignment (SVA and C2-7 Cobb angle) had no significant differences after one-level CDA. Patients who had increased segmental mobility (?ROM >0°) had significantly less HO and similarly improved clinical outcomes than those who had decreased segmental mobility (?ROM <0°).
Patient Care: By our research, we demonstrated a better understanding of HO formation after cervical arthroplasty and provide a measure to minimized HO.
Learning Objectives: By the conclusion of this session, participant should be able to: (1) realize the proper indication of cervical arthroplasty, (2) understand the importance of kinematics and radiographic parameters to cervical disc arthroplasty