Basic SciencePrimary stability of three different iliosacral screw fixation techniques in osteoporotic cadaver specimens—a biomechanical investigation
Introduction
Pelvic ring fractures are comparatively rare [1], with an incidence of 0.3–8%, and typically result from high-energy trauma [2]. Because of increasing life expectancy, the incidence of osteoporotic and insufficiency fractures of the pelvic ring is increasing [3], [4], [5], [6]. Osteoporotic fractures of the pelvic ring differ substantially from high energy fractures regarding symptoms as well as treatment. Even the patient's own body weight can be sufficient to produce such a fracture [7]. An extreme reduction of bone mass and overstressing of the already weakened bone lead to insufficiency fractures [8]. Insufficiency fractures of the sacrum are already described by Lourie et al. in 1982 [9]. Closed reduction and percutaneous fixation with cannulated sacroiliac screws is a well-established therapy in the operative treatment of osteoporotic posterior pelvic ring fractures [10], [11], [12]. If elderly patients with sacral insufficiency fractures suffer from a high pain level, this minimal invasive procedure can help to both reduce pain and to recover mobility [13]. Even in unstable sacral fractures, iliosacral screw fixation is used and can be combined with lumbopelvic fixation to achieve a high biomechanical stability [14], [15], [16]. To attain even greater stability for the transverse component, lumbopelvic distraction osteosynthesis is combined with iliosacral screw osteosynthesis, resulting in a clinically sufficient multiplanar stability [16]. However, osteoporotic bone quality might lead to the risk of screw loosening [7]. For this reason, cement augmentation of the iliosacral screws is more frequently performed and recommended [11], [17], [18]. Cement augmentation is often performed before screw placement [3]. Wähnert et al. developed a new method with perforated screws, which allows the application of cement after screw placement [19] to reduce possible complications such as cement displacement resulting in nerve compression or embolization [13].
Section snippets
Aim of the study
The aim of the present biomechanical cadaver study was to evaluate the primary stability of three methods of iliosacral screw fixation in human osteoporotic sacrum specimens. Our goal was to compare axial pull-out failure in the following three techniques: screw fixation without cement application, screw fixation with cement application before screw insertion, and screw fixation with a modified, perforated screw and cement application after screw positioning.
Specimens
A total of 15 fresh frozen human cadaveric specimens were used (os sacrum). Only women donors (mean age 81.47±9.04 years) were selected, and bone density was measured in all specimens separately, which showed substantial osteoporosis (mean T-score −4.45±1.73). Osteoporosis was defined according to the World Health Organization (WHO) criteria—bone mineral density of more than 2.5 standard deviations below the mean of a young healthy reference population of the same gender (T-score). A
Pull-out force
The mean maximum pull-out force was 618.1 N±390.7 in Group A, 912.39 N±471.5 in Group B, and 959.7 N±453.2 in Group C (see Fig. 3).
The following pull-out forces were measured in subgroups that compared two different techniques in the same specimens with respect to bone quality:
Discussion
Increasing life expectancy in the last decades is leading to a higher incidence of osteoporotic as well as insufficiency fractures of the pelvic ring [3], [4]. Trauma mechanisms as well as the resulting treatment differ from other types of pelvic ring fractures. The most common mechanism of those fractures is a low impact trauma [2], leading to severe pain and dysfunction [20]. Whereas many elderly patients are still active and have high functional demands, other elderly patients already suffer
Conclusions
Our conclusions to screw stability in fixation techniques are based on a biomechanical evaluation. Regarding iliosacral screw fixation in osteoporotic bone, the primary stability of techniques using cement augmentation is significantly higher compared with screw fixation without cement augmentation. Perforated screws with the same primary stability as that of conventional screw fixation in combination with cement augmentation might be a promising alternative in reducing complications of cement
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Cited by (40)
Pull-out strength evaluation of cement augmented iliac screws in osteoporotic spino-pelvic fixation
2021, Orthopaedics and Traumatology: Surgery and ResearchCitation Excerpt :Aim of the present study is to compare iliac screw fixation without cement fixation and two cement application options in a biomechanical testing with the hypothesis that cement augmentation of iliac screws leads to superior pull-out strength. Methods and group generation as well as cementing treatment followed a pre-existing protocol, which was established in our laboratory [22]. All procedures performed with human cadaver specimens were in accordance with the ethical standards of the institutional national research committee (Approval of the ethics committee of the University of Marburg, AZ 153/16).
Cement augmentation of sacroiliac screws in fragility fractures of the pelvic ring—A synopsis and systematic review of the current literature
2019, InjuryCitation Excerpt :König et al had to remove SI screws in three patients within one year because of screw migration and screw-disturbance [24]. Within the six biomechanical studies, Grechening et al [27] and Oberkircher et al [28] replicated no fracture; Hack et al reproduced in their pelvises FFP Type IIb [29]; Höch et al [30], Osterhoff et al [31] and Grüneweller et al [32] generated FFP Type IIIc. All authors used polymethylmethacrylate bone cement (PMMA).
Bone augmentation: Is it really needed?
2018, InjuryCement-augmented sacroiliac screw fixation with cannulated versus perforated screws – A biomechanical study in an osteoporotic hemipelvis model
2018, InjuryCitation Excerpt :The only biomechanical investigation comparing cement augmentation using cannulated versus perforated screws is the study by Oberkircher et al., who evaluated the pull-out stability of sacroiliac screws, comparing screw fixation without cement augmentation, cement augmentation with conventional cannulated screws and cement augmentation with perforated screws. A significantly higher stability of the techniques involving cement augmentation could be demonstrated, but no significant difference in stability was found when comparing cement augmentation with cannulated and perforated screws [10]. However, pull-out forces do not simulate biomechanical load in vivo.
FDA device/drug status: Investigational (modified [six 2.0 mm perforations over the first 1/2 of the thread] self-cutting lag screws made of titanium [aap Biomatterials, Dieburg, GmbH]).
Author disclosures: LO: Consulting (Vexim, B), Consulting (DFine, A). AM: Nothing to disclose. CB: Nothing to disclose. FD: Nothing to disclose. SR: Nothing to disclose. AK: Consulting (Vexim, B), Consulting (DFine, A).
The disclosure key can be found on the Table of Contents and at www.TheSpineJournalOnline.com.