Clayton Adam

Biomechanical testing of a sheep spine with a scoliosis implant attached

Spine biomechanics is the study of motions and forces in the human spine, investigated in order to gain a better understanding of various spinal disorders and to develop optimal treatments. Assoc Prof Adam’s team use both experimental testing and computer simulation to explore the deformations and stresses in spinal tissues during physiological loading, and to understand how various diseases affect the mechanics of spinal tissues.

CT scan of a scoliosis patient showing the rotation of the spinal column

Scoliosis is a type of spinal deformity in which the spine develops a sideways S-shaped curve and an unnatural rotation of the ribcage (rib hump). Although not usually life threatening, scoliosis cases which progress can result in a disfiguring deformity of the spine and ribcage. Through the Paediatric Spine Research Group, Assoc Prof Adam’s team are developing improved predictive methods for deciding which scoliosis cases are most likely to progress (and therefore require treatment), as well as advanced biomechanical models to simulate how a particular patient’s spine will respond to corrective surgery.

Confocal microscope image of trabecular bone showing a microscopic crack. The lamellar (layered) structure of the bone is also visible

Bone is a livingmaterial that constantly replaces old tissue with new in a process called remodeling. The main function of remodeling is to repair microscopic cracks formed in bone during physical activity. These cracks affect the strength and stiffness of bone, and certain types of cracks can trigger rapid bone loss, yet surprisingly little is known about how they form and grow during physical loading. This project will combine mechanical testing, high resolution imaging, and computer modeling to quantify the mechanics of microdamage in trabecular bone, the porous bone most susceptible to osteoporosis. The project will provide new understanding of the role of microcracks in osteoporosis and other skeletal disorders.

Computer (Finite Element) model of the spine and ribcage of a scoliosis patient

Chief Investigators: Prof Mark Pearcy, Aspro Clayton Adam, Prof John Evans, Dr Geoff Askin
Funding Source: Australian Research Council Discovery Projects scheme (2006-08)

Spinal deformities are debilitating and disfiguring conditions which strike the young and otherwise healthy, especially girls. In Australia there are over 50,000 adolescents with idiopathic scoliosis, a deformity for which neither cause nor cure has been discovered. Modern spinal implants apply targeted corrective forces, however excessive force can overload spinal joints and vertebrae leading to tissue damage, implant breakage and loss of correction after surgery. Predicting the limits of correction achievable in a particular patient requires biomechanical models of spinal tissues and implants. This project will develop new modelling techniques to optimise deformity correction and avoid implant-related complications.

3D reconstruction of the spine and ribcage of a scoliosis patient from a CT scan

Chief Investigators: Assoc Prof Clayton Adam
Funding Source: Golden Casket Foundation

The natural history of idiopathic scoliosis varies from patient to patient. Some patients develop a small curve which either remains stable or resolves during subsequent growth, whilst in other patients subsequent growth causes rapid progression of the deformity requiring surgical treatment.

Because of the relatively high prevalence of scoliosis in the population, assessment and observation of small curves can place significant demands on the resources of hospital spinal clinics. Due to the high number of ‘false positives’ (small curves which do not progress), school screening programs for scoliosis have been discontinued in many areas. The solution to this problem lies in improved assessment of progression risk for small curves. Knowing which curves are very likely to progress would allow resources to be allocated more effectively toward these patients.

The aim of this project is to improve the prediction of progression risk in scoliosis by considering new (and biomechanically valid) measures of curve size and shape, and to develop and apply a new progression risk factor based on scoliosis patients at the Mater Spinal Clinic.

Results of a computer simulation of an osteoporotic vertebra. The outer shell of cortical bone and inner core of spongy trabecular bone are both visible. The colours represent the levels of stress in the bone, blue is low stress, red is high stress

Name: Katrina McDonald
Course: PhD

Synopsis: The NIH estimate that 30-50% of women and 20-30% of men will develop a vertebral fracture in their lifetime. 700,000 vertebral fractures occur each year in the United States alone, 85% of which are associated with osteoporosis. Osteoporosis is a disease which compromises bone mineral density and trabecular micro-architecture, resulting in an increased fragility and susceptibility to fracture.   The microarchitectural changes which result due to osteoporosis have been well documented, however it has been difficult to quantify the effects of these changes.

This research will develop experimental and numerical simulation techniques to study the mechanisms of vertebral compression fracture, in particular the effects of trabecular bone architecture on fracture risk and severity.  The numerical models will be validated by comparison with experimental data using both synthetically manufactured vertebral bodies and in vitro specimens.  The numerical and experimental models will then be used to investigate the biomechanics of current fracture repair techniques (vertebroplasty and kyphoplasty).  Using these newly developed analysis tools, innovative, augmentation methods for vertebral compression fracture repair (which do not have detrimental effects on adjacent vertebrae) can be investigated.

 

An experimental and finite element investigation of the biomechanics of scoliosis correction surgery

 

An experimental investigation of the mechanics of vertebral body screws used in spinal deformity surgery

 

Biomechanics of shape memory alloy staples used for minimally invasive scoliosis correction

 

The mechanics of microdamage and microfracture in trabecular bone

 

Current Postgraduate Students (Associate supervisor)

Periosteum tissue engineering and Its in vivo application in bone defect healing

Name: Wei Fan
Course: PhD

 

The feasibility of vibration analysis as a technique to detect osseointegration of transfemoral implants

Name: Nicola Cairns
Course: PhD

 

Previous Postgraduate Students (Principal supervisor)

Abrasive waterjet cutting of polycrystalline alumina ceramics – modeling, process optimization and finite element analysis

Name: Prasad Gudimetla
Year: Completed 2001
Course: PhD

 

Previous Postgraduate Students (Associate supervisor)

A finite element and experimental investigation of the femoral component mechanics in a total hip arthoplasty

 

Finite element modeling of annular lesions in the lumbar intervertebral disc

 

Modelling of articular cartilage load-carriage biomechanics

Name: Sigbjorn Olsen
Year: 2002
Course: PhD