172. Seven-year progression and 10-year prediction of adjacent level degeneration and disease after lumbar total disc replacement: A post hoc analysis of a prospective clinical trial with 7-year follow-up

Abstract

<h3>PURPOSE</h3> To understand the progression of radiographic adjacent-level degeneration (ALDeg) seven years after lumbar total disc replacement (TDR) and the relationship of these changes with range of motion (ROM) and symptomatic adjacent-level disease (ALDis) using the seven-year follow-up data from a prospective, multicenter activL Food and Drugs Administration (FDA) Investigational Device Exemption (IDE) randomized controlled trial. <h3>METHODS</h3> Patients with single-level, symptomatic lumbar disc degeneration who were unresponsive to 6 months of nonoperative care, received activL or ProDisc-L, and had radiographs available were analyzed for the incidence for ALDeg and progression of ALDeg (ΔALDeg). ALDeg presence was determined using a modified, four-point, Kellgren-Lawrence scale. Incidence of ALDis was identified in patients who received activL or ProDisc-L with or without available radiographs. ALDis was defined as the need for reoperation at the segment adjacent to the index segment. The possible relationship between ROM and ΔALDeg was also investigated. Logistic regression modeling was used to predict ALDeg and ALDis outcomes to 10 years. <h3>RESULTS</h3> At baseline, 25% of patients had ALDeg. By seven-year follow-up, 33% of patients had ALDeg and 80% of these patients showed no ΔALDeg. Only a small percentage (3.4%) of patients had severe ΔALDeg by seven-year follow-up; the majority of patients had mild (75.9%) or moderate (20.7%) ΔALDeg by seven years. Incidence of ALDis was identified in 4 patients through seven-year follow-up (2.4%). Three patients received fusion at an adjacent level and one patient underwent fusion at the index and adjacent levels to treat stenosis at both levels along with symptomatic disc degeneration at the adjacent level. Improvement in ROM from baseline ranged from 0°to 16.4° at seven-year follow-up. For each degree in ROM gained at the TDR level, there was a consistent decrease in the percent of patients with ΔALDeg. Of patients having any improvement in ROM from baseline at the TDR level, only 16.9% had ΔALDeg; of patients having a 10°improvement in ROM, 0% of patients had ΔALDeg. The predicted probability of ALDeg after lumbar TDR was 53.9% by 10 years. In contrast, the predicted probability of clinical ALDis was only 2.8% by 10 years. <h3>CONCLUSIONS</h3> Post hoc analysis of seven-year data from a prospective trial confirm relatively low rates of ALDeg, ALDeg progression, and clinical ALDis after TDR over the long-term, with predicted rates being low through to 10 years. Improvement in ROM may be associated with reduced ΔALDeg. <h3>FDA DEVICE/DRUG STATUS</h3> activL total disc replacement (Approved for this indication), prodisc-L total disc replacement (Approved for this indication).