A Prognostic Evaluation of Back Pain Resolution Following Total Disc Replacement

Abstract

Background: Spinal fusion is the traditional surgical treatment for chronic low back pain (CLBP), but loss of segmental motion may redistribute stress to adjacent levels and accelerate degenerative changes (adjacent segment disease (ASD)). Total disc replacement (TDR) was developed as a motion-sparing alternative, yet long-term evidence comparing surgical goal attainment with clinical outcome remains limited.

Objective: To evaluate the relationship between achievement of the surgical goal and clinical outcome following TDR versus instrumented fusion, and to characterize segmental and adjacent-level kinematic changes over time.

Methods: One hundred fifty consecutive patients (80 female, 70 male; mean age 42 years; range 22 - 60) with symptomatic degenerative disc disease at one or two segments between L1 and S1 and CLBP were randomized to TDR (n = 85) or instrumented fusion (n = 65). Outcomes were assessed using a visual analog scale (VAS) and a global assessment (GA) score for back pain. Segmental mobility was evaluated by means of dynamic conventional radiography (DCRA) preoperatively and at 2- and 5-year follow-up.

Results: The surgical goal was achieved in 72% of TDR patients (restored and sustained mobility) and 64% of fusion patients (complete absence of motion) (p = 0.31). 72% of TDR and 64% of fusion patients reported being pain-free or much improved; complete pain relief was reported by 37% versus 13%, respectively. A significant association between surgical goal achievement and clinical outcome was observed in the TDR group (p < 0.02), but not in the fusion group (p = 0.46). TDR patients meeting the surgical goal achieved significantly superior results across all outcome measures compared with fusion patients who attained arthrodesis. Fusion was associated with significantly greater anteroposterior displacement at the adjacent L4 - L5 segment (p < 0.05). Fourteen fusion patients required reoperation for implant removal, and seven TDR patients underwent secondary fusion for facet joint pain.

Conclusions: At 5-year follow-up, both surgical goal attainment and clinical outcomes were superior following TDR compared with fusion. These findings appear interrelated, as patients with mobile prostheses reported better results. Given the time-dependent nature of segmental mobility and ASD, a 10-year follow-up is planned.