Induced pressures on the epiphyseal growth plate with non segmental anterior spine tethering.

Study Design: Experimental biomechanical study of pressures exerted on the epiphyseal growth plates (GP) in tethered porcine cadaveric spines.

Objectives: To experimentally measure the pressure exerted on the vertebral end plates of a tethered porcine spine model. Flexible spine tethering is a novel fusionless surgical technique that aims to correct scoliotic deformities based on growth modulation due to the pressure exerted on vertebral body epiphyseal GP. The applied pressure resulting from spine tethering remains not well documented.

Methods: The ligamentous thoracic segment (T1-T14) of four 3-months old Duroc Landrace pigs (female; 22 kg, range: 18-27 kg) was positioned in lateral decubitus in a custom-made stand. Vertebra T14 was clamped but the remaining spine was free to slide horizontally. For every specimen, six configurations were tested: three or five instrumented motion segments (T5-T10 or T7-T10) with applied compression of 22, 44 or 66 N. The pressure generated on the GPs in the tethered side was measured with a thin force sensor slid either at the proximal, apex or distal levels. The data were analyzed with an ANOVA.

Results: The pressure was significantly different between three and five instrumented motion segments (averages of 0.76 MPa ± 0.03 and 0.60 MPa ± 0.03, respectively; p < 0.05), but the pressure exerted on each GP along the instrumented spine was not significantly different for a given number of instrumented levels. The pressure was linearly correlated to the tether tension.

Conclusions: Non segmental anterior spine tethering induced similar pressures on every instrumented level regardless of the number of instrumented levels, with 21% lesser pressures with 5 motion segments.

Level Of Evidence: Level IV.