Fenestration in Dachshunds: New MRI Study Questions Benefit and Cost-Effectiveness

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

Daniel Low, Vasileios Vallios, Tomas Basto, Marios Charalambous

Background

Thoracolumbar intervertebral disc extrusion (IVDE) is a major cause of pelvic limb neurological dysfunction in dogs, particularly in chondrodystrophic breeds such as Dachshunds. Prophylactic fenestration (PF) has been proposed to reduce the risk of recurrent IVDE, but previous evidence is limited and of low quality. Earlier studies often lacked systematic imaging follow-up and cost–benefit evaluation, leading to uncertainty about PF’s true protective effect and economic value. This study aimed to investigate the relationship between PF and disc survival using MRI and to conduct the first cost–benefit analysis of PF.

Methods

A retrospective cohort study was conducted across two UK referral hospitals (2019–2025). Eighty chondrodystrophic dogs with recurrent IVDE and MRI documentation of both the first and second episodes were included. A total of 633 intervertebral discs (IVDs) between T11–L7 were analyzed, excluding discs already extruded at first IVDE. Fenestration status, Pfirrmann grade (disc degeneration score), and other variables were recorded. Survival analysis of IVDs was performed using an accelerated failure time (AFT) model. Cost–benefit simulations considered three scenarios (worst-, base-, best-case) based on the effect size of PF, and incorporated surgical costs from 17 UK centers.

Results

Of the 31 fenestrated IVDs, 4 (12.9%) later extruded, compared with 76/602 (12.6%) non-fenestrated IVDs. PF showed no significant association with IVD survival (time ratio: 1.17; 95% CI: 0.49–2.76; p = 0.72). In contrast, Pfirrmann grade strongly predicted survival: higher degeneration grades were associated with markedly reduced disc survival (TR: 0.34; 95% CI: 0.26–0.46; p < 0.001). No effect of fenestration on adjacent discs was observed. Cost–benefit analysis showed that universal PF was not cost-effective under most conditions. Targeted PF of Pfirrmann grade 3 discs yielded net savings in base- and best-case scenarios, whereas PF of grade 4 discs was only cost-effective under limited best-case assumptions. PF was not cost-effective in simulated lower-risk populations.

Limitations

The retrospective design and non-standardized use of PF introduce potential bias. Only a minority of discs were fenestrated, leading to wide confidence intervals. MRI protocols varied between hospitals. The study included only dogs that experienced recurrent IVDE, a high-risk subgroup, limiting generalizability. Cost–benefit modeling used estimated surgical costs and assumed linear increases in PF-related costs, without accounting for consumables, welfare impacts, or rare adverse PF events.

Conclusions

This study found no evidence that PF prolongs intervertebral disc survival or prevents recurrence under the examined conditions. Disc degeneration severity (Pfirrmann grade) was the strongest predictor of recurrence risk. Universal PF is unlikely to be cost-effective, but targeted PF of moderately degenerated discs (grade 3) may offer economic and clinical benefits. The findings highlight the need for prospective studies with systematic imaging to define the true role of PF in managing IVDE in chondrodystrophic dogs.

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