19. Radiographic progression of lumbar degenerative spondylolisthesis: natural history and associated risk factors

Abstract

BACKGROUND CONTEXT

The natural history of degenerative spondylolisthesis (DS) remains poorly understood, particularly regarding its progression and related factors.

PURPOSE

To evaluate the radiographic progression rate of DS and its associated risk factors over a long-term follow-up period.

STUDY DESIGN/SETTING

Retrospective comparative study.

PATIENT SAMPLE

We enrolled patients with DS (at L3-4, L4-5, or L5-S1) who underwent at least 5 years of follow-up. We retrospectively analyzed 76 patients with DS (80 levels) with a mean age at diagnosis of 60.2 years. The mean follow-up period was 104.8 months (range, 60.7-239.4 months).

OUTCOME MEASURES

We evaluated the demographics, comorbidities, smoking history, follow-up duration, and the presence of surgery (after at least 5 years of nonsurgical follow-up). The degree of DS was measured using the slippage distance (mm) and Taillard method (%) on the standing plain radiographs. Patients with a slippage increase of at least 3 mm during follow-up compared to the initial status were classified as having progression of DS.

METHODS

The variables were compared between two groups (progression vs nonprogression). Statistical analysis identified factors associated with progression, including age, follow-up duration, and initial spondylolisthesis severity. In addition, we performed logistic regression analyses and survival analysis to evaluate the related factors associated with DS progression.

RESULTS

Initial slippage distance averaged 3.9 mm (9.6% of the Taillard method), increasing to 6.7 mm (16.6% of the Taillard method) at the final follow-up. The DS progression (=3 mm increased slippage distance) occurred in 41.3% (33/80) during follow-up. When comparing the two groups, the progression group exhibited younger age at diagnosis (57.6 vs 62.1 years, p=0.009), longer follow-up (117.9 vs 95.6 months, p=0.043), and milder initial slippage (2.3 mm vs 5.0 mm, p< 0.001). Multiple logistic regression analysis identified an initial degree of DS (slippage distance) as the determinant factor, with a cutoff of < 4 mm indicating higher progression risk (AUC: 0.751, sensitivity: 81.8%, specificity: 61.7%). Patients with =4 mm initial slippage distance exhibited significantly reduced DS progression. Kaplan-Meier survivorship curve showed DS progression rates were 15% at 5 years and 54% at 10 years. Cox proportional hazards modeling confirmed significantly higher progression rates for initial slippage < 4 mm (p=0.011).

CONCLUSIONS

The overall rate of DS progression (=3 mm increased slippage distance compared to initial diagnosis) was 41.3% (33/80). DS progression predominantly occurred in patients with mild initial degree (< 4 mm of slippage distance), younger age at diagnosis, and longer follow-up periods. Survival analysis showed a clear distinction in DS progression risk based on the 4 mm threshold of initial slippage distance.

FDA Device/Drug Status

This abstract does not discuss or include any applicable devices or drugs.