Introduction
Currently anterior cervical discectomy and fusion (ACDF) is a widely accepted surgical treatment for patients with radiculopathy and myelopathy caused by degenerative disc disease (DDD). ACDF results in high patient satisfaction and high fusion rates and is a well accepted procedure. However, longer follow-up indicates that up to 25% of the patients develop recurrent radicular symptoms from adjacent level degeneration requiring surgical intervention within 10 years after the initial ACDF procedure. This adjacent level degeneration may be caused by the natural course of degenerative disc disease, but it is generally believed that fusion can significantly change the normal loading and mobility at adjacent levels which might attribute to the development of adjacent level disease.
More recently, cervical arthroplasty has gained more acceptance as potential alternative to ACDF. Disc arthroplasty aims to restore function and flexibility, reducing the chance to develop adjacent level disease. Short-term clinical results have shown that cervical arthroplasty has similar or better pain relief and maintains the motion of the index level , but long-term follow up has to show that cervical arthroplasty will reduce the incidence of adjacent level disease and accompanying need for surgical intervention.
NuNec™ Cervical Disc Arthroplasty System
The NuNec cervical arthroplasty system (Pioneer Surgical Technology BV) is a cervical arthroplasty device that is made of PEEK-OPTIMA and uses a unique CAM interference screw locking mechanism for endplate fixation (Figure 1).
CAM fixation provides for the ease of insertion and a low risk of vertebral body splitting in multi-level cases. The CAM fixation also has the advantage of easy reversibility either during surgery or later, if needed, over the keel design which is difficult to remove without the risk of damaging the vertebrae. Benefits of the PEEK-on-PEEK design include its biocompatibility, biostability, superb wear resistance and radiolucency. Most cervical artificial discs are manufactured in part from ferromagnetic materials, resulting in strong artifact on CT and MRI images (Figure 2). The outer surfaces of the NuNec device are coated with hydroxyapatite (HA) to enhance both the short- and long-term fixation to the vertebrae. A pilot clinical study was initiated to assess the safety and effectiveness of this device.
Preclinical Results
The NuNec has an HA coating that fulfills both applicable ISO and ASTM standards for coating of medical devices and it has been shown that the application of the HA coating does not affect the chemical and mechanical properties of the PEEK substrate.Figure 1. NuNec with unique CAM interference locking mechanism
Figure 2. MRI of N