Intra-operative measurement of applied forces during anterior scoliosis correction.
BACKGROUND
Spinal instrumentation and fusion for the treatment of scoliosis is primarily a mechanical intervention to correct the deformity and halt further progression. While implant-related complications remain a concern, little is known about the magnitudes of the forces applied to the spine during surgery, which may affect post-surgical outcomes. In this study, the compressive forces applied to each spinal segment during anterior instrumentation were measured in a series of patients with Adolescent Idiopathic Scoliosis.


METHODS
A force transducer was designed and retrofit to a routinely used surgical tool, and compressive forces applied to each segment during surgery were measured for 15 scoliosis patients. Cobb angle correction achieved by each force was measured on intra-operative fluoroscope images. Relative changes in orientation of the screw within the vertebra were also measured to detect intra-operative screw plough.


RESULTS
Intra-operative forces were measured for a total of 95 spinal segments. The mean applied compressive force was 540N (SD 230N, range 88N-1019N). There was a clear trend for higher forces to be applied at segments toward the apex of the scoliosis. Fluoroscopic evidence of screw plough was detected at 10 segments (10.5%).


CONCLUSIONS
The magnitude of forces applied during anterior scoliosis correction vary over a broad range. These forces do reach magnitudes capable of causing intra-operative vertebral body screw plough. Surgeons should be aware there is a risk for tissue overload during correction, however the clinical implications of intra-operative screw plough remain unclear. The dataset presented here is valuable for providing realistic input parameters for in silico surgical simulations.
Paediatric Spine Research Group, Institute of Health and Biomedical Innovation, Queensland University of Technology, Centre for Children's Health Research, Level 5, 62 Graham St, South Brisbane, Qld 4101, Australia. Electronic address: helenfairhurst84@hotmail.com.
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H
Fairhurst
Paediatric Spine Research Group, Institute of Health and Biomedical Innovation, Queensland University of Technology, Centre for Children's Health Research, Level 5, 62 Graham St, South Brisbane, Qld 4101, Australia. Electronic address: j2.little@qut.edu.au.
J P
JP
Little
Paediatric Spine Research Group, Institute of Health and Biomedical Innovation, Queensland University of Technology, Centre for Children's Health Research, Level 5, 62 Graham St, South Brisbane, Qld 4101, Australia. Electronic address: c.adam@qut.edu.au.
C J
CJ
Adam
D000293:Adolescent; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D008297:Male; D059035:Perioperative Period; D011183:Postoperative Complications / Q000517:prevention & control; D012600:Scoliosis / Q000503:physiopathology / Q000601:surgery*; D013123:Spinal Fusion / Q000009:adverse effects / Q000379:methods*; D013131:Spine / Q000503:physiopathology / Q000601:surgery; D013314:Stress, Mechanical; D013904:Thoracic Vertebrae / Q000601:surgery; D016474:Weight-Bearing / Q000502:physiology*
Anterior scoliosis correction; In vivo measurements; Scoliosis; Spinal deformity; Spine; Thoracic spine