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Loading capacity of the transverse process

The objective of our study was to examine the load-bearing capacity of the transverse processes of human cadaveric thoracic vertebrae to vertical loads and sagittal moments. The reason for our study is that we wanted to demonstrate that the transverse process of the thoracic vertebrae is durable enough to support the CAB hook - a complimentary hook to the CD system - placed onto it and is able to handle the vertical load or sagittal moment during correction of scoliosis.

We used 107 thoracic vertebrae removed from 10 cadavers. We prepared them in vertebral pairs, and they were fixed into a material testing apparatus. Supero-inferior vertical loads and axial sagittal moments were applied to the transverse process using the CAB hooks at a rate of 30 mm/min load and 8.5 deg/sec moment until it fractured. We recorded 142 measurements, 99 were for vertical load and 43 for sagittal moment. The average vertical load required for mechanical insufficiency was 337 N (SD=128 N) and the average sagittal moment was 14.4 Nm (SD=4.5 Nm).

The setup for the sagittal moment measurements with the rib stump attached The setup for the sagittal moment measurements with the rib stump attached

The setup for the axial force measurements with the rib stump attached The setup for the axial force measurements with the rib stump attached

Our results were that both the vertical and sagittal loading capability of the transverse process is large enough to withstand significant correctional forces, without fracture, through the CAB hooks. Based on these results we have used the CAB hooks in over 30 scoliosis operations with success.

Csernátony Z, Molnár Sz, Hunya Zs, Manó S, Kiss L. Biomechanical examination of the thoracic spine – the axial rotation moment and vertical loading capacity of the transverse process. Journal of Orthopaedic Research 2011;29(12):1904-9.

General information

Parent department:
Department of Orthopaedic Surgery, University of Debrecen

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H-4032 Nagyerdei krt. 98, Debrecen, Hungary

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biomech@med.unideb.hu

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