Expansive pedicle screw feasible for osteoporotic spinal surgery
MedWire News: An expansive pedicle screw (EPS) may be an effective alternative to a polymethylmethacrylate-augmented pedicle screw (PMMA-PS) for use in spinal surgery in osteoporotic vertebrae, Chinese researchers report.
"Transpedicular fixation can be challenging in the osteoporotic spine," explain Wei Lei (Fourth Military Medical University, Xi'an, Shaanxi Province) and colleagues.
They add that this is because surgery in such patients can result in complications such as screw loosening, migration, or back-out, which compromise the surgical outcome.
EPSs - screws that expand at the screw tips to give greater bone contact area without a concurrent increase in the pedicle insertion diameter or screw length - and PMMA-PSs have both been used to increase screw stability in osteoporosis patients undergoing spinal surgery.
In the present study, Lei and team used osteoporotic vertebrae from human cadaveric spines to assess the stability of EPS and PMMA-PS in primary spinal surgery. They also tested conventional pedicle screws (CPSs) for comparison.
The researchers inserted either a CPS without augmentation, a CPS augmented by 2.5 ml PMMA (PMMA-PS group), or an EPS, into five vertebra each, then performed biomechanical tests 24 hours later to test screw stability.
As reported in the Archives of Orthopaedic and Trauma Surgery, maximal axial pullout strength and energy-to-failure level were a significant one and a half to two times higher in the PMMA-PS and EPS groups compared with those in CPS group, indicating enhanced screw stability in the former two groups compared with the latter group.
There was no significant difference in either parameter between the PMMA-PS and EPS groups, but there was a tendency for greater stability with PMMA-PS.
The researchers remark that EPS can enhance screw stability to a degree that is similar to the traditional method of screw augmentation with PMMA, without the added risk of pedicle fracture, leakage, and compression caused by larger screws and augmentation with PMMA.
They therefore conclude by proposing that "EPS is an effective, safe and easy method [that] has a great application potential in augmentation of screw stability in the osteoporosis clinic."
MedWire (www.medwire-news.md) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011
By Laura Dean