Long-Term Outcomes of Posterior Lumbar Interbody Fusion Using Stand-Alone Ray Threaded Cage for Degenerative Disk Disease: A 20-Year Follow-Up

Abstract

Study design: Retrospective study.

Purpose: To analyze outcomes of posterior lumbar interbody fusion (PLIF) stand-alone cages.

Overview of literature: PLIF for degenerative disk disease using stand-alone cages has lost its popularity owing to implant-related complications and pseudoarthrosis.

Methods: We analyzed the records of 45 patients (18 women, 27 men), operated between January 1994 and December 1996, with a mean follow-up of 18 years 3 months (20 years 3 months-22 years 3 months). Clinical outcomes were measured using visual analogue score (VAS), Oswestry disability index (ODI), Odom's criteria, and radiological measurements of fusion rate, Cobb angle, and implant-related complications conducted at the preoperative evaluation, hospital discharge, 12-month follow-up, and final follow-up.

Results: Preoperative mean VAS (back) was 6.9 and VAS (radicular) was 7.2, with mean improvements (p <0.05) of 2.9 and 3.1, respectively, at the final follow-up. Median preoperative ODI was 64.5, with a mean improvement to 34 and 42 at the 12-month and final follow-ups, respectively (p <0.05). Odom's criteria at the 12-month follow-up were excellent in 11.2% patients, good in 57.7%, fair in 31.1%, and poor in none of the patients; at the final follow-up, no patient was classified as excellent, 71.1% as good, 22.2% as fair, and 6.7% as poor (p <0.05). Pseudoarthrosis was observed in five patients (11.1%), of whom, three (6.6%) required re-operation. Preoperative disk height was 9.23 mm, which increased to 13.33 mm in the immediate postoperative evaluation and was maintained at 10.0 mm at the final follow-up (p <0.05). The preoperative mean L1-S1 Cobb angle was 34.7°, which changed to 44.7° in the immediate postoperative evaluation and dropped to 39.7° at the final follow-up (p <0.005).

Conclusions: PLIF stand-alone cages were associated with good clinical outcomes. Although the fusion rate was excellent, maintenance of disk heights and a lordotic alignment were not achieved in the long term.

Keywords: Degenerative intervertebral disks; Spinal fusion; Stand-alone implants; Treatment outcome.

Fig. 1. Postoperative lateral (A) and anteroposterior (B) radiographs at 19-year follow-up. Follow-up of a 72-year-old female patient following L4–L5 posterior lumbar interbody fusion for degenerative lumbar spondylolisthesis. Postoperative standard radiographs show good lumbar lordosis as well as fusion without cage subsidence.

Fig. 2. Visual analog scale (VAS) (back) assessment at preoperative and postoperative follow-ups.

Fig. 3. Oswestry disability index (ODI) scores during preoperative and postoperative follow-ups.

Fig. 4. Results of disk height measurements (mm) during preoperative and postoperative follow-ups.