Summary
The purpose of the study was to evaluate trabecular bone score (TBS) technology for orthopedic application
(TBS Ortho) as a predictor of a screw pull-out strength in a cadaveric model. This study finds that TBS Ortho correlates more
strongly with the screw pull-out strength compared to cortical density, computed tomography (CT) Hounsfield units (HU),
and dual-energy X-ray absorptiometry (DXA) bone mineral density (BMD)
Purpose
Patient bone quality impacts the mechanical strength of surgical fixation constructs. Preoperative assessments
of bone quality and the potential for a screw pull-out are important for surgical planning as well as postoperative rehabilitation protocols. Previous work has correlated the screw pull-out strength with the screw insertional torque, cortical thickness,
and CT HU. TBS is a gray-level textural metric that can be extracted from a two-dimensional DXA scan, improves fracture
prediction, and may evaluate the mechanical competence of both the cortical and trabecular bones. The purpose of the study
was to evaluate TBS technology for TBS Ortho as a predictor of the screw pull-out strength in a cadaveric model.
Methods
Twenty paired, fresh-frozen cadaver femurs stripped of soft tissue were obtained (5 M, 5F specimens, age range
of 56–96 years). Standard clinical femur CT were performed to obtain HU, cortical thickness, and cortical density. DXA was
also performed using a novel analysis technique as distal femur DXA is not routinely acquired clinically. DXA data were
used to generate TBS Ortho values in two distal femur regions of interest. All femurs then underwent a screw pull-out testing
with five lateral distal femoral 5-mm locking screws (n= 100 screws total). The correlation coefficient from Spearman tests
and R-squared of the fixed effects from the linear mixed effects models were calculated.
Conclusion
This study finds that TBS Ortho correlates more strongly with the screw pull out strength in a cadaveric distal
femur model compared to cortical density, CT HU, and DXA BMD. These preliminary results suggest that TBS Ortho may
be a valuable tool to model mechanical integrity of bone preoperatively.
