Immersion in Raloxifene does not significantly improve bone toughness or screw pull-out strength in multiple in vitro models

Michael R Eby,Jaimo Ahn,Matthew Counihan,Danielle M Cristino,Michael W Hast,Kendall M Masada

doi:10.1186/s12891-021-04342-1

Michael R Eby, Jaimo Ahn + Show 4 more

Open Access

https://doi.org/10.1186/s12891-021-04342-1

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Abstract

BackgroundFailure of surgical fixation in orthopaedic fractures occurs at a significantly higher rate in osteoporotic patients due to weakened osteoporotic bone. A therapy to acutely improve the mechanical properties of bone during fracture repair would have profound clinical impact. A previous study has demonstrated an increase in mechanical properties of acellular cortical canine bone after immersion in raloxifene. The goal of this study was to determine if similar treatment yields the same results in cancellous fetal bovine bone and whether this translates into a difference in screw pull-out strength in human cadaveric tissue.MethodsCancellous bone from fetal bovine distal femora underwent quasi-static four-point bending tests after being immersed in either raloxifene (20 μM) or phosphate-buffered saline as a control for 7 days (n = 10). Separately, 5 matched pairs of human osteoporotic cadaveric humeral heads underwent the same procedure. Five 3.5 mm unicortical cancellous screws were then inserted at standard surgical fixation locations to a depth of 30 mm and quasi-static screw pull-out tests were performed.ResultsIn the four-point bending tests, there were no significant differences between the raloxifene and control groups for any of the mechanical properties - including stiffness (p = 0.333) and toughness (p = 0.546). In the screw pull-out tests, the raloxifene soaked samples and control samples had pullout strengths of 122 ± 74.3 N and 89.5 ± 63.8 N, respectively.ConclusionsResults from this study indicate that cancellous fetal bovine samples did not demonstrate an increase in toughness with raloxifene treatment, which is in contrast to previously published data that studied canine cortical bone. In vivo experiments are likely required to determine whether raloxifene will improve implant fixation.

Highlights

Failure of surgical fixation in orthopaedic fractures occurs at a significantly higher rate in osteoporotic patients due to weakened osteoporotic bone
In the fetal bovine experiment, there were no significant differences between the raloxifene and control groups for any of the mechanical properties determined from four-point bending
Ultimate screw pull-out loads were 89.5 ± 63.8 N and 122 ± 74.3 N for the pooled control and raloxifene groups, where each screw was treated as a unique data point (Fig. 5)

Summary

Introduction

Failure of surgical fixation in orthopaedic fractures occurs at a significantly higher rate in osteoporotic patients due to weakened osteoporotic bone. The total population facility-related hospital cost of osteoporotic fractures in the United States from the year 2000–2011 averaged $5.1 billion per year, higher than the respective facility-related costs of myocardial infarction ($4.3 billion) or stroke ($3.0 billion) [6]. In addition to these costs, we must consider morbidity from loss of function, mortality from associated complications, and the socioeconomic impact of lost work productivity and strain on caretakers among other downstream effects [7]

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