**Cervical Disc Arthroplasty**

Bruce V. Darden

 *OrthoCarolina Spine Center, Charlotte USA* 

### **1. Introduction**

For more than 50 years, anterior cervical discectomy and fusion (ACDF) has been the workhorse procedure for cervical degenerative pathology. (Bailey & Badgely, 1960; Cloward, 1961; Robinson & Smith, 1955) The procedure has yielded successful results clinically in multiple large series. (Bohlman et al, 1993; Gore & Sepic, 1984) Advances in allograft and cage techniques as well as the use of anterior plating systems have diminished complications in ACDF. However, concerns about adjacent segment degeneration (ASD) have tempered some enthusiasm for the procedure. Gore et al (Gore & Sepic, 1998) reviewed a series of 50 ACDF patients followed long term. Almost universally, the patients developed ASD. One-third of the cohort developed recurrent pain with half of the symptomatic group requiring additional surgery. Hilibrand et al (Hilibrand et al, 1999) evaluated a group of 374 patients undergoing ACDF. They showed a 2.9% per year risk of development of symptomatic ASD, with two thirds of the symptomatic patients requiring additional surgery. Goffin et al (Goffin et al, 1995) prospectively followed a series of ACDF patients who underwent the procedure for either a degenerative or traumatic condition. Follow-up was for five to nine years. Sixty percent of the patients developed ASD, equally distributed between the older degenerative population and the younger traumatic population, providing evidence that fusion may accelerate degenerative changes. Goffin et al (Goffin et al, 2004) reviewed a larger series of ACDF patients followed for an average of 8.3 years. In this group, 92% of the patients developed ASD, though they had a much lower rate of additional surgical procedures, 6.1% for the entire length of follow-up, distinctly lower than Hilibrand et al. Numerous cadaveric biomechanical studies (Eck et al, 2002; Pospiech et al, 1999) evaluating adjacent level intradiscal pressures and range of motion in simulated fusion models have shown that both increase after fusion. These altered biomechanics may thus accelerate ASD.

Against this background, centers began experimenting with cervical disc arthroplasty in the 1980s. Cummins and collaborators at the Frenchay Hospital, Bristol, England developed a metal-on-metal ball and socket arthroplasty and implanted it on a small series of patients in the 1990s. (Cummins et al, 1998) The arthroplasty underwent a number of design changes and is now known as Prestige. Bryan, in the US, developed a one piece metal-on-polymer device called the Bryan Cervical Disc Replacement, initially evaluated clinically in Europe. (Goffin et al, 2002) ProDisc-C arthroplasty is a metal-on-polyethylene implant adopted from the ProDisc-L lumbar disc arthroplasty developed by Thierry Marnay. (Delamarter & Pradhan, 2004) Since

Cervical Disc Arthroplasty 501

Bryan Cervical Disc Prosthesis (Medtronic Sofamor Danek, Memphis, Tennessee) consists of a nucleus made of polyurethane between two titanium alloy endplates in a clamshell configuration. (Figure 2) There are two bearing surfaces in the arthroplasty at the interfaces between the nucleus and the endplates. A polyurethane sheath attaches to the endplates and surrounds the nucleus. Sterile saline is injected between the outer sheath and the nucleus as lubricant. The endplates have a titanium porous coating for bone ingrowth and a small

ProDisc-C Cervical Disc Prosthesis (Synthes, West Chester, Pennsylvania) has a ball and socket design, with endplates made of a cobalt-chrome alloy. The endplates have keels for immediate fixation and titanium plasma spray backing for bone ingrowth. The bearing surface has an articulating dome of ultra high molecular weight polyethylene (UHMWPE) attached to the inferior endplate and a concave polished socket integral to the superior

**2.2 Bryan Cervical Disc Prosthesis** 

flange anteriorly to prevent posterior migration.

(Courtesy of Medtronic Sofamor Danek, Memphis, Tennessee)

Fig. 2. Bryan Cervical Disc Prosthesis

(Courtesy of Synthes, West Chester, Pennsylvania)

Fig. 3. ProDisc-C Cervical Disc

**2.3 ProDisc-C** 

endplate. (Figure 3)

these first three devices have been developed, the number of cervical disc arthroplasties has proliferated. The literature in this nascent field is limited, but growing each year.
