Radiofrequency-activated PMMA-augmentation through cannulated pedicle screws: A cadaver study to determine the biomechanical benefits in the osteoporotic spine
Affiliations: [a] Department of Orthopaedics and Trauma Surgery, University Hospital Bonn, Bonn, Germany | [b] Department of Orthopaedics and Trauma Surgery, Hospital Wermelskirchen, Wermelskirchen, Germany | [c] Institute of Anatomy, University Hospital RWTH Aachen, Aachen, Germany | [d] Department of Orthopaedics, University Hospital Marburg, Marburg, Germany
Correspondence:
[*]
Corresponding author: Hans Goost, Department of Orthopaedics and Trauma Surgery, Hospital Wermelskirchen, Königstraße 100, 42929 Wermelskirchen, Germany. Tel.: +49 2196 98 361; Fax: +49 2196 98 306; E-mail:Goost@krankenhaus-wermelskirchen.de
Note: [1] Both authors equally contributed to this paper.
Abstract: INTRODUCTION: PMMA-augmentation of pedicle screws strengthens the
bone-screw-interface reducing cut-out risk. Injection of fluid cement bears
a higher risk of extravasation, with difficulty of application because of
inconsistent viscosity and limited injection time. OBJECTIVE: To test a new method of cement augmentation of pedicle
screws using radiofrequency-activated PMMA, which is suspected to be easier
to apply and have less extravasations. METHODS: Twenty-seven fresh-frozen human cadaver lumbar spines were
divided into 18 osteoporotic (BMD ≤ 0.8 g/cm2) and
9 non-osteoporotic (BMD > 0.8 g/cm2) vertebral bodies. Bipedicular
cannulated pedicle screws were implanted into the vertebral bodies; right
screws were augmented with ultra-high viscosity PMMA, whereas un-cemented
left pedicle screws served as negative controls. Cement distribution was
controlled with fluoroscopy and CT scans. Axial pullout forces of
the screws were measured with a material testing machine, and results were
analyzed statistically. RESULTS: Fluoroscopy and CT scans showed that in all cases
an adequately big cement depot with homogenous form and no signs of
extravasation was injected. Pullout forces showed significant
differences (p < 0.001) between the augmented and non-augmented pedicle screws
for bone densities below 0.8 g/cm2 (661.9 N ± 439) and over
0.8 g/cm2 (744.9 N ± 415). CONCLUSIONS: Pullout-forces were significantly increased in
osteoporotic as well as in non-osteoporotic vertebral bodies without a
significant difference between these groups using this standardized, simple
procedure with increased control and less complications like extravasation.
