The Biomechanical Properties of Cement-Augmented Pedicle Screws for Osteoporotic Spines

Abstract

Study Design: This is a broad, narrative review of the literature. Objective: In this review, we describe recent biomechanics studies on cement-augmented pedicle screws for osteoporotic spines to determine which factors influence the effect of cement augmentation. Methods: A search of Medline was performed, combining the search terms “pedicle screw” and (“augmentation” OR “cement”). Articles published in the past 5 years dealing with biomechanical testing were included. Results: Several factors have been identified to impact the effect of cement augmentation in osteoporotic spines. These include the type of augmentation material, the volume of injected cement, the timing of augmentation, the severity of osteoporosis, the design of the pedicle screw, and the specific augmenting technique, among others. Conclusions: This review elaborates the biomechanics of cement-augmented pedicle screws, determines which factors influence the augmentation effect, and identifies the risk factors of cement leakage in osteoporotic bone, which might offer some guidance when using this technique in clinical practice. Further, we provide information about newly designed screws and recently developed augmentation materials that provide higher screw stability as well as fewer cement-related complications.

Increased stability due to symmetric cement volume in augmented pedicle screws? A biomechanical study

“…This confirms previous findings. 15,19,20,22,39 In our study particularly a balanced distribution of 1.5 mL PMMA per pedicle screw achieved most increase in pull-out strength. While there was a negative correlation of holding force to lower unilateral volume of PMMA (1.5 mL >0.75 mL >0 mL), interestingly non-augmented pedicle screws tended to be even more stable than pedicle screws with maximum unbalanced volume of PMMA (1.5 mL/0 mL).…”

“…As improving the osseous integrity around inserted pedicle screws is regarded as a key factor, augmentation of pedicle screw instrumentation with PMMA is used as a gold standard in osteoporotic spinal surgery. 10,15,18,20,22 Considering this approach, a maximum increase of mechanical strength by applicate maximum volume of PMMA into the bone should be stated as the best method. On the other hand, each application of PMMA into the vertebral body should be well considered due to fulminant risks associated to cement leakage.…”

“…However, it is generally accepted that a volume of 1.5 mL per pedicle screw achieves a maximum stability without significant improvements at higher volumes, but evidence is missing, weather symmetrical or asymmetrical cement application affects the construct stability. [22][23][24] Furthermore, it must be noted that there is additional risk of complications related to cement application, that is, cement leakage, pulmonary cement embolism (PCE) and difficulty in revision surgery. [25][26][27][28] Therefore, the stability of the screw-rod construct under a deviating distribution of PMMA applied to the instrumentation was the subject of this biomechanical study.…”

Limitierte Zementierung bei langstreckiger dorsaler Versorgung

“…Basierend auf zahlreichen biomechanischen Versagenslasttestungen sorgt eine zusätzliche Zementaugmentation der Pedikelschrauben für eine weitere signifikante und relevante Verbesserung des Schraubenhalts [5,6]. Viele Autoren führen deshalb standardisiert eine Zementaugmentation der Pedikelschrauben bei der Versorgung von instabilen thorakolumbalen Wirbelkörperfrakturen bei osteoporotischer Knochensubstanz durch [7,8,9].…”

“…Jedoch sollte die Zementaugmentation unter Berücksichtigung der potenziellen zementassoziierten Komplikationen so zurückhaltend wie möglich durchgeführt werden. In Bezug auf die Zementmenge gibt es gute Daten, dass eine Zementmenge von 1,0 bis 1,5 ml Zement pro Schraube optimal zu sein scheint [5]. Basierend auf den oben aufgeführten Überlegungen ist es jedoch wichtig, die Vor-und Nachteile der Zementaugmentation einer jeden einzelnen Schraube zu beurteilen, um die Indikation dafür zu stellen.…”