Spinal Angulation: A Limitation of the Fetal Lamb Model of Myelomeningocele.

INTRODUCTION: The surgically induced fetal lamb model is the most commonly used large animal model of myelomeningocele (MMC) but is subject to variation due to surgical technique during defect creation.

MATERIAL AND METHODS: Thirty-one fetal lambs underwent creation of the MMC defect, followed by defect repair with either an extracellular matrix (ECM) patch (n = 10) or ECM seeded with placental mesenchymal stromal cells (n = 21). Postnatal hindlimb function was assessed using the Sheep Locomotor Rating (SLR) scale. Postmortem magnetic resonance imaging of the lumbar spine was used to measure the level and degree of spinal angulation, as well as cross-sectional area of remaining vertebral bone.

RESULTS: Median level of angulation was between the 2nd and 3rd lumbar vertebrae, with a median angle of 24.3 degrees (interquartile range 16.2-35.3). There was a negative correlation between angulation degree and SLR (r = -0.44, p = 0.013). Degree of angulation also negatively correlated with the normalized cross-sectional area of remaining vertebral bone (r = -0.75, p < 0.0001).

DISCUSSION: Surgical creation of fetal MMC leads to varying severity of spinal angulation in the ovine model, which affects postnatal functional outcomes. Postnatal assessment of spinal angulation aids in standardization of the surgical model of fetal MMC repair.