Single-Level Total Disc Replacement: Index-Level and Adjacent-Level Revision Surgery Incidence, Characteristics, and Outcomes

Abstract

Background: The literature reports that index level (IL) revision spine surgery (RSS) and adjacent level (AL) RSS are diminished in lumbar TDR compared with fusion procedures. There is a paucity of PROMs reported after RSS.

Objective: To present the incidence of RSS at the IL and AL following single-level lumbar total disc replacement (TDR) and to document patient-related outcome measures (PROMs) associated with RSS.

Methods: PROMs and timelines were analyzed for 32 RSS patients from a prospective cohort study of 401 patients treated with TDR for single-level degenerative disc disease. The data collected prospectively are analyzed from baseline (prior to index surgery) to latest follow-up following RSS. PROMs, including visual analog scales for back and leg, Oswestry Disability Index, and Roland-Morris Disability Questionnaire, were collected preoperatively; postoperatively at 3, 6, and 12 months; and annually thereafter until RSS. The time to RSS was recorded, and PROMs for RSS (IL, AL, or both) were documented, analyzed, and compared.

Results: The median time to RSS in the IL cohort was 35 months (interquartile range [IQR] = 9-51 months). The median time to RSS cohort was 70 months (IQR = 41.3-105.3 months). Timepoints facilitate PROM discussion for RSS. Patients in both groups achieved thresholds for the minimum clinically important difference for pain and disability scores. The small sample size in each group contributed to the variability demonstrated by the 95% CIs, thereby cautioning definitive conclusions.

Conclusions: This study reveals that statistically significant and modest clinical improvements in PROMs can be achieved in RSS for lumbar TDR at IL and AL. The surgical approach and technique are reflective of the pathology and suggest that anterior RSS for AL degeneration and posterior RSS for IL pathology yield similar results.

Clinical relevance: Statistical and clinical improvements can be achieved in IL-RSS and AL-RSS following single level TDR. It is essential for clinicians to understand and verify the underlying IL and/or AL pathology to select an appropriate management strategy and to facilitate balanced informed discussions with patients.

Keywords: adjacent segment; arthroplasty; artificial disc; back pain; degenerative disc disease; index level; long-term results; lumbar spine; motion preservation; revision; total disc replacement.

Figure 1

(A) Preoperative magnetic resonance images, (B) preoperative postdiscography computed tomographic image, (C) postoperative radiograph, (D) 6-mo postoperative radiograph with spondylolisthesis, and (E) postoperative radiograph of index level revision, circumferential fusion.

Figure 2

(A) Postoperative radiograph of index level L5-S1 total disc replacement (TDR) and (B) revision at adjacent level, L4-L5, with insertion of a TDR.

Figure 3

Time to index level revision spine surgery and final reported outcome score for each patient (n = 16). Patients 11 and 16 also had adjacent-level revision spine surgery. Patient 13 underwent revision surgery at another clinic.

Figure 4

Time to adjacent level revision spine surgery for clinical adjacent segment pathology, and final reported outcome score for each patient (n = 18). Patients 11 and 16 also had index-level revision spine surgery.

Figure 5

Mean change from baseline and 95% CI for visual analog scale (VAS) (0 = no pain to 100 = worst pain) back and leg pain scores at follow-up times after surgery. ASD = adjacent segment disease; T1 = first year after primary surgery; T2 = final year after primary surgery; T3 = first year after revision surgery; T4 = final year after revision surgery with reported outcome. Most mean scores were above the minimum clinically important difference (MCID).

Figure 6

Mean change from baseline and 95% CI for Oswestry Disability Index (ODI) (0 = no disability to = 100 worst disability) and Roland-Morris Disability Questionnaire (RMDQ) (0 = no disability to 24 = worst disability) at follow-up times after surgery. ASD = adjacent segment disease; T1 = first year after primary surgery; T2 = final year after primary surgery; T3 = first year after revision surgery; T4 = final year after revision surgery with reported outcome. Most mean scores were above the minimum clinically important difference (MCID).