Intra-operative measurement of applied forces during anterior scoliosis correction

Clin Biomech (Bristol, Avon). 2016 Dec;40:68-73. doi: 10.1016/j.clinbiomech.2016.10.014. Epub 2016 Oct 30.

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 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%).

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.

Keywords: Anterior scoliosis correction; In vivo measurements; Scoliosis; Spinal deformity; Spine; Thoracic spine.

MeSH terms

  • Adolescent
  • Biomechanical Phenomena
  • Female
  • Humans
  • Male
  • Perioperative Period
  • Postoperative Complications / prevention & control
  • Scoliosis / physiopathology
  • Scoliosis / surgery*
  • Spinal Fusion / adverse effects
  • Spinal Fusion / methods*
  • Spine / physiopathology
  • Spine / surgery
  • Stress, Mechanical*
  • Thoracic Vertebrae / surgery
  • Weight-Bearing / physiology*