Preclinical and clinical experience with a viscoelastic total disc replacement

Abstract

BackgroundThe purpose of this study is to describe the mechanical durability and the clinical and radiographic outcomes of a viscoelastic total disc replacement (VTDR). The human intervertebral disc is a complex, viscoelastic structure, permitting and constraining motion in 3 axes, thus providing stability. The ideal disc replacement should be viscoelastic and deformable in all directions, and it should restore disc height and angle.MethodsMechanical testing was conducted to validate the durability of the VTDR, and a clinical study was conducted to evaluate safety and performance. Fifty patients with single-level, symptomatic lumbar degenerative disc disease at L4-5 or L5-S1 were enrolled in a clinical trial at 3 European sites. Patients were assessed clinically and radiographically for 2 years by the Oswestry Disability Index (ODI), a visual analog scale (VAS), and independent radiographic analyses.ResultsThe VTDR showed a fatigue life in excess of 50 million cycles (50-year equivalent) and a physiologically appropriate level of stiffness, motion, geometry, and viscoelasticity. We enrolled 28 men and 22 women in the clinical study, with a mean age of 40 years. Independent quantitative radiographic assessment indicated that the VTDR restored and maintained disc height and lordosis while providing physiologic motion. Mean ODI scores decreased from 48% preoperatively to 23% at 2 years’ follow-up. Mean VAS low-back pain scores decreased from 7.1 cm to 2.9 cm. Median scores indicated that half of the patient population had ODI scores below 10% and VAS low-back pain scores below 0.95 cm at 2 years.ConclusionsThe VTDR has excellent durability and performs clinically and radiographically as intended for the treatment of symptomatic lumbar degenerative disc disease.Clinical RelevanceThe VTDR is intended to restore healthy anatomic properties and stability characteristics to the spinal segment. This study is the first to evaluate a VTDR in a 50-patient, multicenter European study.

Indications for Lumbar Total Disc Replacement: Selecting the Right Patient with the Right Indication for the Right Total Disc

“…Many contraindications are related to personal and medical characteristics ( Table 1 ). Age ranges in different studies included: 18-60 years; 9 , 16 , 18 , 21 , 26 , 28 – 35 18-70 years; 36 , 37 20-55 years; 38 20-60 years; 19 and, 30-55 years. 13 One study investigated a population over 60 years old and recommended TDR for patients with adequate bone quality and without circumferential spinal stenosis.…”

“…TDRs were implanted after failed nonoperative therapy for a minimum of 6 months, 8 , 9 , 13 , 16 , 18 , 19 , 25 , 26 , 28 , 29 , 32 – 37 , 40 – 42 although nonoperative therapy duration varied from 338 to 9 months. 30 …”

“…For potential TDR patients, indications have been described as preoperative VAS back pain scores of at least 40 9 , 18 , 34 , 35 , 37 or 50 38 of 100. Preoperative ODI score >30% 9 , 18 , 19 , 33 , 35 , 36 , 38 or 40% 29 , 32 , 37 have been required.…”

“…Designs with one or more components implanted as one piece can potentially provide performance characteristics most like those of a healthy disc because they are viscoelastic. 77 They can simulate a disc to a large extent, but with equal and reduced 19 , 77 ROM in every direction due to the homogeneous material. The natural intervertebral disc needs dampening properties for producing motion, because it does not have typical joint surfaces.…”

Viscoelastic Disc Arthroplasty Provides Superior Back and Leg Pain Relief in Patients with Lumbar Disc Degeneration Compared to Anterior Lumbar Interbody Fusion

“…They have been developed and introduced into clinical practice in recent years. 5 Comparative effectiveness studies of different fusion types and TDRs are extremely rare today. 4 Randomized clinical trials (RCT) comparing fusion and TDR are rare and have a high administrative burden.…”