title: Pedicle screw cement augmentation. A mechanical pullout study on different cement augmentation techniques.
abstract: Pedicle screws with polymethyl methacrylate (PMMA) cement augmentation have been shown to significantly improve the fixation strength in a severely osteoporotic spine. However, the efficacy of screw fixation for different cement augmentation techniques remains unknown. This study aimed to determine the difference in pullout strength between different cement augmentation techniques. Uniform synthetic bones simulating severe osteoporosis were used to provide a platform for each augmentation technique. In all cases a polyaxial screw and acrylic cement (PMMA) at medium viscosity were used. Five groups were analyzed: I) only screw without PMMA (control group); II) retrograde cement pre-filling of the tapped area; III) cannulated and fenestrate screw with cement injection through perforation; IV) injection using a standard trocar of PMMA (vertebroplasty) and retrograde pre-filling of the tapped area; V) injection through a fenestrated trocar and retrograde pre-filling of the tapped area. Standard X-rays were taken in order to visualize cement distribution in each group. Pedicle screws at full insertion were then tested for axial pullout failure using a mechanical testing machine. A total of 30 screws were tested. The results of pullout analysis revealed better results of all groups with respect to the control group. In particular the statistical analysis showed a difference of Group V (p = 0.001) with respect to all other groups. These results confirm that the cement augmentation grants better results in pullout axial forces. Moreover they suggest better load resistance to axial forces when the distribution of the PMMA is along all the screw combining fenestration and pre-filling augmentation technique.
authors.affiliation: Neurosurgery Department, Humanitas Clinical and Research Hospital, via A. Manzoni 56, 20089 Rozzano (Milan)- Italy. Electronic address: f.costa@outlook.it.
authors.forename: Francesco
authors.initials: F
authors.lastname: Costa
authors.affiliation: Neurosurgery Department, Humanitas Clinical and Research Hospital, via A. Manzoni 56, 20089 Rozzano (Milan)- Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Ortolina
authors.affiliation: IRCCS Galeazzi Orthopedic Institute, Milan, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Galbusera
authors.affiliation: Neurosurgery Department, Humanitas Clinical and Research Hospital, via A. Manzoni 56, 20089 Rozzano (Milan)- Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Cardia
authors.affiliation: Department or Aerospace Sciences and Technologies, Politecnico di Milano, Milan, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Sala
authors.affiliation: Sintea Plustek, Assago, Italy.
authors.forename: Franco
authors.initials: F
authors.lastname: Ronchi
authors.affiliation: Sintea Plustek, Assago, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Uccelli
authors.affiliation: Sintea Plustek, Assago, Italy.
authors.forename: Rossella
authors.initials: R
authors.lastname: Grosso
authors.affiliation: Neurosurgery Department, Humanitas Clinical and Research Hospital, via A. Manzoni 56, 20089 Rozzano (Milan)- Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Fornari
mesh_terms: D001843:Bone Cements; D008422:Materials Testing; D055595:Mechanical Phenomena; D065289:Pedicle Screws; D019904:Polymethyl Methacrylate; D011474:Prosthesis Design
chemical_list: D001843:Bone Cements; D019904:Polymethyl Methacrylate
keywords: Augmentation; Cement; Implant failure; PMMA; Pull-out test; Screw loosening