Introduction

Ankle sprains are common injuries [1,2] and muscle atrophy is common after immobilization [3]. This may contribute to poor recovery leading to long term ankle instabilities [2]. There is a limited understanding of the extent of muscle atrophy post-injury and a complete dearth of knowledge on how soft tissues like fascia respond to such injury. Here, we use advanced MRI to investigate skeletal muscle and fascia structural changes during recovery period of one patient.  

Method

Our participant (female, age: 33 years, mass 54 kg, height 1.69 m) volunteered for MRI scan as a part of a separate project. Three days after initial scan the participant suffered an ankle sprain suddenly and was put into an immobilization boot for 18 days. The participant agreed to an MRI scan 3 days after removing the boot.  MRI was conducted on 3T Siemens Skyra scanner over two-thirds of the right shank below the knee. Muscle imaging was done using a Proton Density sequence; fascia imaging used 2D stack of spirals non-Cartesian sequence [4]. Spatial resolution was 1x1x3 mm³. Muscles and fascia were segmented in images to determine volume and thickness, respectively.

Results

We observed atrophy of most shank muscles and hypertrophy of some muscles after injury and immobilization. Muscle loss ranged from no change in the lateral gastrocnemius to 19.5% in flexor hallucis longus. The soleus displayed a 12% loss of volume. Hypertrophy occurred in the hamstrings, quadriceps, tibialis anterior, and the adductor magnus. Fascia thickness increased from 2.37mm to 2.6mm post-injury.

Discussion

We demonstrate variable responses of muscles to immobilization after ankle sprain injury, implying some increased loading of muscles during recovery. We quantify changes to the deep fascia using novel imaging, demonstrating a significant thickening in response to sprain injury and immobilization [5,6].

Acknowledgement

Funding provided by RSNZ Marsden Fast-Start Grant.