Triadyme-C, a Polycrystalline Diamond Compact Cervical Disc Replacement (cTDR): Evaluation of Clinical and Radiographic Outcome

Approximately fifty percent of the population has evidence of degenerative changes in their cervical spine by the age of fifty. As part of the aging process, the intervertebral discs wear out. They lose their flexibility and elasticity and begin to collapse or even herniate. This process may result in a pathological condition called cervical Degenerative Disc Diseases (cDDD). cDDD can either be asymptomatic or symptomatic, showing different symptoms such as neck, shoulder, head, arm or leg pain, possibly associated with numbness, tingling or weakness in the upper extremity. In most cases symptomatic cDDD is initially treated conservatively with rest, immobilization, physical therapy, chiropractic manipulation and pain medication. For those cases not responding to conservative therapy, anterior cervical discectomy and fusion (ACDF) is a standard technique. The primary purpose of ACDF is to excise any disc material (discectomy), which compresses the spinal nerve or cord causing pain, sensory disturbance or weakness at the affected level, followed by interbody fusion of the adjacent vertebrae using grafts or intersomatic devices to compensate the instability and the loss of disc height resulting from discectomy. Despite the success of this common procedure, some disadvantages are to be mentioned including donor site morbidity when autografts are used, graft or device subsidence or pseudarthrosis of the segment to be fused. Besides this, physiological motion of successfully fused segments is no longer possible. This alters the loading and kinematics of adjacent spine segments which is believed by some authors to lead to adjacent segment overload as reported by several clinical and biomechanical studies. To address the disadvantages of ACDF, cervical total disc replacement (cTDR) has been developed in the 1990s, with the aim to carry the load and restore the normal disc height while preserving almost physiological segmental motion.

Today, several different cTRD designs are on the market, some of them with mid- to long-term results. A number of randomized controlled trials indicate clinical equivalence or even superiority of cTDR in some aspects compared to ACDF.

The Dymicron Triadyme-C cTDR is a two-piece articulating artificial disc prosthesis. Its patented tri-lobe articulation mechanism consists of three spherical lobes mating to three non-congruent, spherical pockets. The motion of these three lobes within their associated pockets emulates and controls natural motion of the cervical spine motion segment in all degrees of freedom.Triadyme-C is a self-centering device. This is achieved by the implant growing in height as it moves away from its center. The further away from center, the tighter the ligaments will be stretched. Each half of the Triadyme-C is a sintered monobloc, consisting of a polycrystalline diamond (PCD) bearing surface with a base of titanium-titanium carbide (Ti-TiC) composite. PCD is a sintered material composed of fused diamond crystals (typically more than 90%) and a small amount of catalyst sintering metal. The polycrystalline structure of diamond, together with the small amount of residual metal alloy, contributes significantly to the extraordinary toughness and abrasion-resistance of the material. PCD retains many of the phenomenal properties of natural diamond, including hardness, but in an isotropic form that is far more resistant to fracture.

This Post Market Clinical Follow-up (PMCF) is conducted to collect clinical and radiographic outcome information on patients suffering from intractable symptomatic cervical disc disease requiring 1- or 2-level reconstruction of the disc from C3-C7, after being treated with the Triadyme-C polycrystalline diamond compact cervical disc replacement.