The benefit of cement-augmented pedicle screws for revision surgery in osteoporotic bone : a cadaveric study

Abstract

Purpose Increasing numbers of spine surgery cases and an aging society led to challenges during revision surgery with osteoporotic bone. Safe and stable operative techniques are required.

Methods In this ex vivo study, human lumbar vertebrae were prepared and then screened for assessing bone density. Eighteen donors (65 vertebrae) with osteoporotic conditions were included. Primary dorsal instrumentation was performed using either standard pedicle screws (6.35 mm diameter; Group A, n = 50) or vertebroplasty screws (VT, 6.35 mm; Group B, n = 15). This was followed by a standardized pull-out test cycle, after which the vertebrae of group A exhibited pedicle perforations replicating revision conditions. Subsequently, 50 vertebrae from Group A were reassigned to simulate revision conditions and divided into two subgroups (n = 25 each): Group A1 received conventional pedicle screws with an increased diameter (7.5 mm), while Group A2 was treated with cement-augmented pedicle screws (VT, 6.35 mm). A second pull-out test was performed, and statistical analysis was conducted.

Results The specimens with conventional screws had a lower mean pull-out strength compared to primarily cement-augmented screws during the first pull-out cycle 662.8 ± 365.1 N vs. 1066.1 ± 213.7 N. In the revision model, cement-augmented screws (Group A2) demonstrated a significant higher median pull-out strength compared to larger-diameter conventional screws (Group A1) (687.5 N [IQR: 448.8–1137.5 N]; vs. 486.5 N [IQR: 338.8–605.0 N]).

Conclusion In this ex vivo revision model of osteoporotic bone, increasing screw diameter alone resulted in reduced pull-out strength compared to primary instrumentation, whereas cement-augmented pedicle screws consistently demonstrated superior fixation in both test cycles. These findings highlight the limited effectiveness of increasing screw diameter under revision conditions and support cement augmentation as a biomechanically advantageous strategy in osteoporotic bone, while clinical validation remains necessary.