# New Model of Disuse-Induced Bone Density Loss in Horses

## TL;DR

This study introduces a new, less restrictive model to induce bone density loss in horses by using stall confinement and heel elevation, offering a practical alternative to traditional cast immobilization.

## Contribution

The study presents a novel equine model for disuse-induced bone loss that avoids the complications of cast immobilization.

## Key findings

- Computed tomography showed significant bone density loss in the limb with elevated heels after two months.
- The model is practical and reproducible for studying pharmacological interventions in equine bone demineralization.

## Abstract

Bone loss due to reduced mechanical loading is a well-recognized phenomenon in both human and veterinary medicine. Experimental models of disuse-induced bone density in horses typically rely on cast immobilization, which can be associated with complications. In this study, we investigated an alternative approach based on stall confinement combined with unilateral heel elevation to induce skeletal unloading in the forelimb. Using computed tomography (CT) imaging, we observed significant bone loss over a two-month period, particularly in the limb with elevated heels. These findings support the use of this model as a practical alternative for developing new pharmacological targets in horses.

Disuse-induced bone loss during stall confinement and immobilization is a major concern in horses because it impairs recovery and increases susceptibility to further injury. Experimental models are needed to evaluate therapeutic options, but most available equine models rely on cast immobilization, which is technically demanding and may be associated with complications. This study aimed to assess a simpler and less restrictive model to induce a quantifiable decrease in bone density in horses. Six French Standardbred horses underwent eight weeks of stall confinement, with a wooden wedge fitted to one front foot to elevate the heels during the last four weeks. Bone density was assessed using computed tomography (CT) examinations of both forelimbs performed at the beginning (M0) and after the confinement period (M2). Serum markers of bone metabolism (CTX-I, osteocalcin, bone-specific alkaline phosphatase, and hydroxyproline) were analyzed monthly from baseline to 2 months post confinement. Statistical analysis used Wilcoxon signed-rank tests and mixed models as appropriate. Computed tomography revealed a significant decrease in bone density after confinement (p < 0.05), more pronounced distally in the wedge limb. CTX-I levels varied with physical activity. This model provides a practical and reproducible alternative to cast immobilization for inducing equine bone demineralization.