Long-term Follow-Up Results of Dynamic Cervical Implant in Patients with Cervical Disc Diseases: Compared with Prestige LP

Background and Study Aims: Prestige LP arthroplasty has been proven to be a safe and effective treatment for patients with cervical disc degenerative disease (DDD). Dynamic Cervical Implant (DCI) has emerged as a novel implantation device for cervical DDD. This study aimed to compare the outcomes of these procedures after 5 years of follow-up in the DCI and Prestige LP groups. Key words: cervical disc degenerative disease; cervical disc replacement; Dynamic Cervical Implant; Prestige LP Materials and Methods: This study retrospectively enrolled 79 consecutive cervical DDD patients with 41 DCI and 47 Prestige LP prostheses implanted. Radiographs were analyzed for intervertebral height and range of motion (ROM). Neural function of the participants was assessed using the Neck Disability Index score, Visual Analog Scale, Japanese Orthopaedic Association score and 36-Item Short Form Survey. Results: The DCI group had statistically lesser flexion/extension and bilateral bending ROM than the Prestige LP group at the operated level(s) (p<0.05). The DCI group showed improved lordotic alignment of C2–C7 and operated functional spinal unit than the Prestige LP group (p<0.05). No statistical difference was observed in the neural function of the two groups. Heterotopic ossification was found in 7 and 14 patients in the DCI and Prestige LP groups, respectively. Conclusion: The 5 years follow-up results were comparable between the two groups. We believe that DCI implantation is a safe and effective procedure and could possibly become an alternative treatment for cervical DDD.

BIOMECHANICAL PERFORMANCE OF A MODIFIED DESIGN OF DYNAMIC CERVICAL IMPLANT COMPARED TO CONVENTIONAL BALL AND SOCKET DESIGN OF AN ARTIFICIAL INTERVERTEBRAL DISC IMPLANT: A FINITE ELEMENT STUDY

Most of the implants used for total disc replacement (TDR) surgery are designed as a ball and socket pair aimed at providing a three-dimensional unconstrained motion. However, one of the major concerns with ball and socket design is the wear of the implant which limits its life. In this study the biomechanical performance of two types of implant designs is compared — a conventional ball and socket type (Prodisc-C) and a modified design of dynamic cervical implant (DCI) using FE analysis. A 3-dimensional geometrical model of cervical spine (C1–T1) was developed using CT scan data of a middle-aged healthy male. Subsequently, using FE analysis, the ROM values were validated with the existing literature using a compressive load in combination with different physiological motions of the neck. Furthermore, FE analysis on the two implants, fitted at C5–C6 segment, showed a significant increase in the ROM of implanted segment using Prodisc and decrease in the ROM of inferior segment, but modified-DCI restored the motion of the implanted and adjacent segments. Analysis of average bone strains adjacent to the implant showed a possibility of stress shielding for Prodisc. However, higher stress distribution on the modified-DCI limited its clinical use.