title: Mechanical assessment of local bone quality to predict failure of locked plating in a proximal humerus fracture model.
abstract: The importance of osteoporosis in proximal humerus fractures is well recognized. However, the local distribution of bone quality in the humeral head may also have a significant effect because it remains unclear in what quality of bone screws of standard implants purchase. The goal of this study was to investigate whether the failure of proximal humerus locked plating can be predicted by the DensiProbe (ARI, Davos, Switzerland). A 2-part fracture with metaphyseal impaction was simulated in 12 fresh-frozen human cadaveric humeri. Using the DensiProbe, local bone quality was determined in the humeral head in the course of 6 proximal screws of a standard locking plate (Philos; Synthes GmbH, Solothurn, Switzerland). Cyclic mechanical testing with increasing axial loading until failure was performed. Bone mineral density (BMD) significantly correlated with cycles until failure. Head migration significantly increased between 1000 and 2000 loading cycles and significantly correlated with BMD after 3000 cycles. DensiProbe peak torque in all screw positions and their respective mean torque correlated significantly with the BMD values. In 3 positions, the peak torque significantly correlated with cycles to failure; here BMD significantly influenced mechanical stability. The validity of the DensiProbe was proven by the correlation between its peak torque measurements and BMD. The correlation between the peak torque and cycles to failure revealed the potential of the DensiProbe to predict the failure of locked plating in vitro. This method provides information about local bone quality, potentially making it suitable for intraoperative use by allowing the surgeon to take measures to improve stability.
authors.forename: Götz
authors.initials: G
authors.lastname: Röderer
authors.forename: Stefano
authors.initials: S
authors.lastname: Brianza
authors.forename: Damiano
authors.initials: D
authors.lastname: Schiuma
authors.forename: Ronald
authors.initials: R
authors.lastname: Schwyn
authors.forename: Alexander
authors.initials: A
authors.lastname: Scola
authors.forename: Boyko
authors.initials: B
authors.lastname: Gueorguiev
authors.forename: Florian
authors.initials: F
authors.lastname: Gebhard
authors.forename: Andrea
authors.initials: A
authors.lastname: Tami
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D015519:Bone Density; D001860:Bone Plates; D005260:Female; D005593:Fracture Fixation, Internal / Q000379:methods*; D006801:Humans; D006810:Humeral Fractures / Q000503:physiopathology / Q000601:surgery*; D058430:Humeral Head / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D008297:Male; D008422:Materials Testing / Q000379:methods; D008875:Middle Aged; D008954:Models, Biological; D011475:Prosthesis Failure; D011859:Radiography; D013314:Stress, Mechanical