Idiopathic scoliosis is a deformity of the spine which typically develops in adolescence. For some, the best possible treatment is surgery. A new technique aims to use the patient’s own growth to correct the deformity while preserving post-operative spine motion through use of a flexible implant.
The new technique is called vertebral body tethering (VBT) and involves screws securing a flexible polyethylene-terephthalate (PET) tether that can be tailored to a patient’s anatomy. Before securing the tether to the spine, it is tensioned between the screw heads along the spine to correct the deformity.
IHBI’s Biomechanics and Spine Research Group senior research fellow Dr Paige Little says the technique shows much promise, but there are still various biomechanical aspects of the surgery that would benefit from further investigation. The aspects include improved knowledge of the forces that should be applied to a patient’s spine to optimise their deformity correction.
There are no clear guidelines regarding the force required for optimal correction and surgical results may depend on a surgeon’s expertise.
Dr Little conducts research at the Centre for Children’s Health Research, enabling collaboration with Dr Geoffrey Askin and Dr Robert Labrom, senior spinal consultants at the adjacent Queensland Children’s Hospital.
Dr Little is using patient-specific spine modelling software to simulate the proposed surgery and predict deformity correction as part of planning for VBT.
A recent study used the software to reconstruct the spine and ribcage of an unidentified 10-year-old patient. The software was used to investigate different combinations of tether tension forces.
‘Drawing on these preliminary results, further investigations of different tether tension magnitudes, different screw configurations and screw orientations will be investigated to optimise the post-operative deformity correction,’ Dr Little says.
‘Our studies will consider the balance between providing a favourable environment for correcting growth asymmetry while not risking bone overload at the screw-bone interface.
‘We are taking great strides in understanding how best to plan for surgery and aiding surgeons in providing their patients with the best outcomes.’
Dr Little says VBT suits younger adolescents who are still growing because the PET tether is flexible and can move with the patient, letting the body aid the spinal correction.
‘One of the key benefits of VBT surgery is that it allows for continued growth and mobility of the spinal joints after surgery, which is favourable when considering the implant system will remain in place permanently.’
Advantages of the surgery also include reduced blood loss and faster recovery time than existing posterior fusion surgery.
In comparison, spinal fusion uses inflexible metal rods, hooks and wires to correct the spinal curve and secure the spine in a straightened position, making it suitable only for older adolescents.
Idiopathic scoliosis is the most common type of scoliosis and has no definite cause. It tends to run in families but the origins are multi-factorial, with idiopathic scoliosis being 10 times more common in girls than boys. Although idiopathic scoliosis can occur at any age, it frequently becomes an issue during pre-adolescence and adolescence when children are growing rapidly.
During a growth spurt, signs of idiopathic scoliosis often become more noticeable, such as uneven shoulders, one shoulder blade protruding more than the other, ribs more prominent on one side, an uneven waistline or a difference in hip height.
Idiopathic scoliosis is often diagnosed at a paediatric check-up or following a school screening, particularly in children who wear loose-fitting clothes that might cover up the symptoms.
Dr Little is part of IHBI’s Centre for Biomedical Technologies, aiming to improve treatment of complex medical cases stemming from injuries, infection and age-related issues. Centre researchers use approaches of regenerative medicine, robotics, artificial intelligence and advanced manufacturing to expand surgical possibilities and reduce complications.
Many of the centre’s researchers also collaborate with orthopaedic surgeons and industry as part of the Queensland Unit for Advanced Shoulder Research to improve knowledge of the shoulder’s biomechanical functions and anatomy using computer modelling, virtual and augmented reality and biofabrication.
Senior research fellow Dr Paige Little