Morphology, motion, and mechanics of vertebral joints in fish

We depend on healthy joints to stay active, independent and productive. Disorders of the joints of our spine (intervertebral joints) are particularly disruptive, with back pain and disorders impacting millions of people. Finding better ways to protect and restore the joints of our spine remains a major challenge.

Fish have become valuable models for studying disorders of spinal joints and bones, however our knowledge of normal spine mechanics in fish is limited. Most studies so far have focused on zebrafish, whose small size and relatively homogenous spine make it difficult to study the interaction of spine shape on motion and joint function.

This project uses a new fish species, like the frogfish, as models to examine the role of soft joint tissues and vertebral bones in spinal motion. Compared to zebrafish, frogfish have larger vertebrae that vary in shape across the spine and bend three-dimensionally. You will use a combination of 3D biological imaging, computer animation, and mechanical modelling to uncover the mechanics of intervertebral joints in this species.

Hypothesis: The interaction of both the soft tissues within the joints and bony vertebrae determine how the spine bends and responds to muscle forces. If so, then the changes in joint anatomy across the spine should lead to changes the joint’s mobility.

Objectives: You will study the three-dimensional (3D) shape and motion of intervertebral joints, using fish as a model.

1. Reconstruct detailed morphology of intervertebral joints. You will use biological imaging such as computed tomography (CT) and magnetic resonance imaging (MRI) to create 3D, digital models of the bones and soft tissues of the intervertebral joints. You will compare the 3D anatomy of the joints to discover how joint morphology changes across the spine from head to tail.
2. Measure the maximum possible mobility of the intervertebral joints. You will manipulate physical specimens or digital models to determine the greatest range of 3D motion allowed by the bony and soft tissue of each intervertebral joint. This range of motion sets the maximum theoretical spine postures that could be achieved during natural behaviours. You will document how the magnitude and direction of joint mobility varies, and test whether this corresponds to changes in joint shape.
3. Test how the intervertebral joints of fish respond to bending forces. You will create a finite-element model of the spine—including the intervertebral joints—and simulate the muscle forces these joints might experience during natural behaviours. This will reveal how joints resist or permit spine bending in certain directions and highlight areas of the spine that may be vulnerable to injury.

Significance: Together this work will improve our understanding of how the shape of intervertebral joints determine the 3D motions of the spine. Establishing the structure-motion relationship of the spine in a healthy fish will be a first step towards building better models of human back pain and disease.