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. 2022 Jun;142(6):1055-1061.
doi: 10.1007/s00402-021-03782-7. Epub 2021 Feb 15.

Local bone quality measure and construct failure prediction: a biomechanical study on distal femur fractures

Dominic Gehweiler  1 , Ursula Styger  1 , Boyko Gueorguiev  1 , Christian Colcuc  2 , Thomas Vordemvenne #  2 , Dirk Wähnert #  3
Affiliations

Local bone quality measure and construct failure prediction: a biomechanical study on distal femur fractures

Dominic Gehweiler et al. Arch Orthop Trauma Surg. 2022 Jun.

Abstract

Introduction: The aim of this investigation was to better understand the differences in local bone quality at the distal femur and their correlation with biomechanical construct failure, with the intention to identify regions of importance to optimize implant anchorage.

Materials and methods: Seven fresh-frozen female femurs underwent high-resolution peripheral quantitative computed tomography (HR-pQCT) to determine bone mineral density (BMD) within three different regions of interest (distal, intermedium, and proximal) at the distal femur. In addition, local bone quality was assessed by measuring the peak torque necessary to break out the trabecular bone along each separate hole of a locking compression plate (LCP) during its instrumentation. Finally, biomechanical testing was performed using cyclic axial loading until failure in an AO/OTA 33 A3 fracture model.

Results: Local BMD was highest in the distal region. This was confirmed by the measurement of local bone quality using DensiProbe™. The most distal holes represented locations with the highest breakaway torque resistance, with the holes on the posterior side of the plate indicating higher values than those on its anterior side. We demonstrated strong correlation between the cycles to failure and local bone strength (measured with DensiProbe™) in the most distal posterior screw hole, having the highest peak torque.

Conclusion: The local bone quality at the distal femur indicates that in plated distal femur fractures the distal posterior screw holes seem to be the key ones and should be occupied. Measurement of the local bone strength with DensiProbe™ is one possibility to determine the risk of construct failure, therefore, thresholds need to be defined.

Keywords: Biomechanics; DensiProbe; Distal femur fracture; Local bone quality; Osteoporosis.

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Conflict of interest statement

The authors declare that they have no conflict of interest.

Figures

Fig. 1
Fig. 1
Slices of a CT scan of a right femur in the coronal, sagittal, and axial planes. The six different regions of interest (ROI) for local BMD evaluation via HR-pQCT are marked in the different planes
Fig. 2
Fig. 2
DensiProbe™ measurement: a after plate positioning and temporary fixation, the distance between both cortices is measured using a custom-made caliper. b The used screw length represents the next available shorter screw to the measured distance. c Following screw length determination, the screw hole is predrilled to a certain depth, and DensiProbe™ is hammered in to measure the peak torque. d screw hole configuration of the locking compression plate
Fig. 3
Fig. 3
Biomechanical test setup. Specimen attached to the machine actuator via a ball-and-socket joint and placed on a seesaw table allowing medio-lateral tilting
Fig. 4
Fig. 4
Local bone mineral density (BMD) determined from HR-pQCT scans for the different anatomical locations (regions of interest) in terms of mean value and standard deviation
Fig. 5
Fig. 5
DensiProbe™ (peak torque) for the different regions (grouped screw holes) compared to the medial BMD (from HR-pQCT) in terms of mean value and standard deviation
See this image and copyright information in PMC

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