Intra-operative measurement of applied forces during anterior scoliosis correction

• Published in: Clinical biomechanics (Bristol) Vol. 40; pp. 68 - 73
• Main Authors: Fairhurst, H., PhD, Little, J.P., PhD, Adam, C.J., PhD
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.12.2016
• Subjects: Adolescent; Anterior scoliosis correction; Biomechanical Phenomena; Female; Humans; In vivo measurements; Male; Perioperative Period; Physical Medicine and Rehabilitation; Postoperative Complications - prevention & control; Scoliosis; Scoliosis - physiopathology; Scoliosis - surgery; Spinal deformity; Spinal Fusion - adverse effects; Spinal Fusion - methods; Spine; Spine - physiopathology; Spine - surgery; Stress, Mechanical; Thoracic spine; Thoracic Vertebrae - surgery; Weight-Bearing - physiology; S pinal deformity; T horacic spine; S pine; Scoliosis; A nterior scoliosis correction; In vivo measurements; Anterior scoliosis correction; Thoracic spine; Spine; Spinal deformity
• ISSN: 0268-0033; 1879-1271
• DOI: 10.1016/j.clinbiomech.2016.10.014

Abstract 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. Findings Intra-operative forces were measured for a total of 95 spinal segments. The mean applied compressive force was 540 N (SD 230 N, range 88 N–1019 N). 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 %). Interpretation 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.