Longitudinal Assessment and Cost–Benefit Analysis of Prophylactic Fenestration in Chondrodystrophic Dogs With Follow-Up Magnetic Resonance Imaging

Abstract

Background: Prophylactic fenestration (PF) has been reported to protect against recurrent intervertebral disc extrusion (IVDE), but recurrence is not always confirmed. No published studies address the cost–benefit of PF. Objectives: Observe the association between PF and intervertebral disc (IVD) survival and conduct cost–benefit analysis. Animals: Eighty chondrodystrophic dogs with recurrent IVDE. Methods: Longitudinal assessment with follow-up magnetic resonance imaging (MRI) was performed to retrospectively observe the survival of in situ IVDs. The association between PF and IVD survival was analyzed using a multivariable survival model, which included Pfirrmann grade as a covariate. Worst-case, base-case, and best-case cost–benefit simulations were conducted, corresponding to the lower 95% confidence interval (CI), point estimate, and upper 95% CI of the effect size of PF. Results: For IVDs treated with PF, 4/31 (12.9%) IVDs were documented to subsequently extrude on follow-up MRI. For IVDs not treated with PF, 76/602 (12.6%) were documented to subsequently extrude on follow-up MRI. There was no association between the use of PF and IVD survival (time ratio: 1.17; 95% CI: 0.49–2.76; p = 0.72). An increase in Pfirrmann grade was associated with a decrease in IVD survival (time ratio: 0.34; 95% CI: 0.26–0.46; p < 0.001). Prophylactic fenestration was only cost-effective under a limited range of conditions. Conclusions and Clinical Importance: There was no evidence that PF prevented IVDE under study conditions. Pfirrmann grade was the strongest predictor of IVD survival. Universal use of PF was not cost-effective in multiple simulations. Targeted PF of high-risk IVDs may be considered the most cost-effective approach.