# Retrospective Analysis of Clinical Management Strategies for Cage Retropulsion Following Posterior Lumbar Interbody Fusion

## TL;DR

This study compares conservative treatment and revision surgery for cage retropulsion after spinal fusion surgery, finding both approaches can be equally effective in certain cases.

## Contribution

The study provides evidence that conservative treatment can be as effective as surgery for mild cage retropulsion cases.

## Key findings

- Conservative treatment and revision surgery showed similar fusion rates and outcomes for lower back pain.
- Revision surgery was more effective for leg pain improvement compared to conservative treatment.
- Cage retropulsion distance of ≥ 8.8 mm was associated with better outcomes following revision surgery.

## Abstract

Cage retropulsion (CR) is a common complication following posterior lumbar interbody fusion (PLIF). Symptomatic patients with CR often require revision surgery. However, there is a lack of literature supporting the effectiveness of conservative treatment for CR. This study compares clinical and radiographic outcomes between conservative treatment and revision surgery in patients with CR after PLIF.

A total of 55 patients with CR after PLIF treated at our institution between 2016 and 2023 were retrospectively reviewed; postoperative radiographic data of follow‐up were used to diagnose CR. Clinical outcomes were assessed before therapy and at the final follow‐up using the visual analog scale (VAS) for lower back pain and leg pain, Oswestry Disability Index (ODI) scores, and Japanese Orthopedic Association 29 (JOA‐29) scores. The treatment effectiveness was evaluated based on whether the score change reached the minimally clinically important difference (MCID). Radiographic indicators included the fusion rates, the extent of CR into the spinal canal, and the total displacement distance. Continuous variables were compared using independent samples t‐tests or Mann–Whitney U tests, while categorical variables were analyzed using Chi‐square or Fisher's exact tests, as appropriate. A p‐value < 0.05 was considered statistically significant.

The fusion rates at the final follow‐up for the conservative treatment group and the revision surgery group were 87.5% and 84.6%, respectively. There were no significant differences in final follow‐up fusion rates, lower back pain VAS scores, leg pain VAS scores, JOA scores, or ODI scores between the two groups (all p > 0.05). Additionally, there was no difference in the proportion of patients whose lower back pain VAS, ODI, and JOA scores achieved MCID between groups (all p > 0.05). However, in the revision surgery group, the proportion of patients whose leg VAS scores reached MCID was significantly higher than in the conservative group (p = 0.001). In the revision surgery subgroup analysis, patients who did not achieve leg VAS MCID demonstrated significantly more severe cage retropulsion distance compared to MCID achievers (p = 0.03).

Conservative treatment yields satisfactory outcomes in mild, symptomatic CR patients, particularly for low back pain. For patients with a CR distance less than 8.8 mm, conservative treatment and revision surgery showed comparable outcomes, whereas when the CR distance is ≥ 8.8 mm, revision surgery was recommended to improve clinical results. Both conservative treatment and revision surgery can yield favorable outcomes when appropriately indicated.

Conservative treatment achieved comparable outcomes to revision surgery in select cage retropulsion cases, with equivalent fusion rates, back pain visual analog scale (VAS), Japanese Orthopaedic Association (JOA), and ODI MCID attainment.