# Degenerative Gastrocnemius Muscle Changes in a Goat Tibial Ostectomy Model Persist 10 Months After Splint Removal

## TL;DR

This study shows that goats experience long-lasting muscle changes after tibial surgery and splinting, with incomplete recovery even 10 months later.

## Contribution

The study provides longitudinal data on muscle recovery in a goat model after orthopedic surgery and external coaptation.

## Key findings

- Operated-side muscles showed significant decreases in mass, length, optimal fiber length, and CSA.
- Muscle CSA remained 20–30% lower on the operated side at 12 months post-surgery.
- Muscle CSA correlated with bone mineral density and ground reaction forces during recovery.

## Abstract

Major orthopedic limb surgery is often accompanied by external coaptation; the combined effect of these interventions can lead to muscle atrophy and functional impairment. Large animal models, including goats, are commonly used to study orthopedic interventions, yet longitudinal data on muscle changes after such interventions are limited. This study quantified gastrocnemius muscle adaptations in adult Boer-cross goats undergoing a clinically representative unilateral tibial segmental ostectomy and external coaptation protocol. Muscles on the operated side exhibited statistically significant decreases in mass, length, optimal fiber length, and CSA, and increases in nucleus density compared to muscles on the contralateral, non-operated side (p < 0.05). Although muscle properties showed partial recovery over time, mass and CSA remained 20–30% lower on the operated side than on the non-operated side at 12 months post-surgery despite cast removal at about 2 months post-surgery. Muscle CSA was positively correlated with bone mineral density and peak vertical ground reaction forces measured during the in vivo study. The extent of muscle recovery in the goat model was less than that observed for other mammalian models of hindlimb remobilization. More research is needed to understand the complex interaction between surgery, external coaptation, and muscle properties in the goat model.