General Session: Cervical Motion Preservation

Presented by: J. Zigler - View Audio/Video Presentation (Members Only)

Author(s):

J. Zigler(1)

(1) Texas Back Institute, Plano, TX, United States

Abstract

Background: Fusion for the treatment of lumbar degenerative disc disease (DDD) necessarily sacrifices motion at the treated level and places increased stresses on adjacent levels. Total disc replacement (TDR) is an alternative to fusion that preserves index level motion. A commonly heard misconception is that L5-S1 should be fused “because TDR implants do not move at this level”. This study aimed to compare ROM at L4-L5 vs. L5-S1 at five years following lumbar TDR, and to explore any differences between those implanted with a mobile core disc (MCD) versus a constrained core disc (CCD) device. Methods This post-hoc analysis of a multicenter, prospective, randomized, controlled, investigational device exemption trial included patients with symptomatic lumbar DDD at L4-L5 or L5-S1 who were treated with single level arthroplasty using either a MCD (n=217) or CCD (n=64) implant. Range of motion at the index level (L4-L5 or L5-S1) was assessed with flexion/extension radiographs preoperatively and post-operatively at 6 weeks, 24 months and 5 years post-operation.

Results: Baseline demographics were the same between patients treated at L4-L5 vs. L5-S1. Range of motion following treatment at L4-L5 was not different from baseline values with either MCD or CCD devices. At L5-S1 index procedures implanted with MCD, ROM initially decreased at 6 wks (from 6.5o to 4.5o, p< 0.001), but returned to baseline values at 24 mo (6.8o) and was maintained at 5 yrs (6.1o). Conversely, in L5-S1 patients with CCD implants, ROM decreased at 6 wks (from 6.4o to 4.7o, p=0.005), but did not return to baseline values by 24 mos (5.1o) or 5 yrs (3.5o). Range of motion for the overall treatment group was not different between L4-L5 and L5-S1 index procedures for either MCD or CCD implants.

Conclusions: Lumbar TDR shows similar improvements in ROM between L4-L5 and L5-S1 index level procedures up to 5 years following implantation. L5-S1 clearly continues to show motion after implantation with a TDR, but mobile core devices maintained better motion than constrained core devices. Furthermore, although there was a transient decrease in ROM following L5-S1 implantation at 6 weeks, ROM continued to improve, returned to baseline levels by 24 mos, and remained stable out to 5 years.