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.