Cervical arthroplasty with Discover prosthesis: clinical outcomes and analysis of factors that may influence postoperative range of motion.

Purpose: The aim of this current study was to analyze the clinical outcomes after Discover cervical disc replacement and its effects on maintaining cervical lordosis and range of motion (ROM). The possible factors influencing postoperative ROM were analyzed.

Method: 27 men and 28 women with a mean age of 46.4 ± 8.7 years were prospectively followed up for 2 years. Clinical outcomes were assessed using Japanese Orthopedic Association (JOA), Neck Disability Index (NDI), visual analog scale (VAS) and Odom's criteria. Radiographic information including segment and overall alignment, functional spinal unit (FSU) and overall ROM, and disc heights were prospectively collected during the follow-up. The correlations between the postoperative FSU ROM at last follow-up and influencing factors were analyzed.

Results: Mean NDI, JOA and VAS scores showed statistical improvements at last follow-up. Anterior migration of the prosthesis was detected in six cases. Heterotopic ossification was observed in ten patients. Mean FSU angle, endplate angle of the treated level and mean overall cervical alignment were all improved significantly at last follow-up (P < 0.001). However, mean FSU ROM of the treated segment significantly decreased postoperatively (P = 0.008), while mean overall ROM showed no significant differences. A significant correlation was found between preoperative FSU ROM and postoperative FSU ROM by the Pearson correlation coefficient (r = 0.325, P = 0.034). Multiple linear regression analysis confirmed that preoperative FSU ROM contributed independently to a model with a coefficient of determination of 0.37 (P = 0.034).

Conclusions: In the 2 years follow-up, the Discover cervical disc arthroplasty has provided satisfactory clinical outcomes. It was able to substantially restore segment and overall cervical alignment while partially maintaining segment and overall cervical ROM. Additionally, we found that postoperative FSU ROM positively correlated with preoperative FSU ROM.