Reduced ASD incidence seen at 5 years with maintained lumbar TDR motion
LOS ANGELES — The evolution of total disc replacement prostheses over time from devices with constrained cores to ones with more mobile cores may ultimately help mitigate adjacent segment disease in patients, according to results of a post hoc analysis presented at the North American Spine Society Annual Meeting.
At 5-year follow-up, Scott L. Blumenthal, MD, and colleagues studied changes in range of motion (ROM) using radiographs for the ProDisc-L (DePuy Synthes) and activL (Aesculap Implant Systems LLC) lumbar total disc replacement (TDR) devices, which have a constrained and mobile core, respectively. In addition, in their study of the FDA investigational device exemption trial data for the two devices, the researchers compared any differences in rates of adjacent segment disease (ASD) with the two prosthesis designs.
Patients with both devices had similar baseline ROM of about 6°, according to Blumenthal.
“At 5 years, the constrained device had a greater decrease in ROM compared to the mobile core [device] and this was statistically significant. The percent of patients with ASD at 5 years also was correlated with this, with the rate of progression lower in the patients with the mobile core device compared with the fixed core device. Again, statistically significant in this analysis,” he said.
The investigators then looked at the percent of patients with increased ASD calculated for each minimum degree of motion at the level of interest.
“It’s the first study I know that has shown this: That with each incremental range of motion, the rate of adjacent segment became less and less to the point, at 6° or more, there was no adjacent segment in either group. So, one of the biomechanical considerations of motion was to hopefully decrease the incidence of adjacent segment and indeed, with threshold range of motion, this does appear to be the case,” Blumenthal said.
On average, activL TDR patients maintained their preoperative range of motion (6.6° vs. 6.1°, P = 0.4) while ProDisc-L TDR patients did not (6.2° vs. 4.2°, P =.02). This drop-off in ROM has been correlated to increased progression of ASD (8.8% vs. 19%, P = .05), according to an Aesculap Implant Systems press release about the findings. – by Susan M. Rapp
Blumenthal SD, et al. Paper 140. Presented at: North American Spine Society Annual Meeting; Sept. 26-29, 2018; Los Angeles.
Disclosure: Blumenthal reports he has stock ownership in FzioMed (<1%), VertiFlex (<1%), Centinel Spine, (<1%) and Spinal Kinetics (<1%); has speaking and/or teaching arrangements with Aesculap and VertiFlex; and is on the scientific advisory board for Aesculap and VertiFlex.