title: Mechanical quantification of local bone quality in the humeral head: a feasibility study.
abstract: OBJECTIVE
  Surgical treatment of proximal humerus fractures can be challenging due to osteoporosis. The weak bone stock makes stable implant anchorage difficult, which can result in low primary stability. Accordingly, significant failure rates, even with modern locking plates, are reported in the literature. Intraoperative knowledge of local bone quality could be helpful in improving results. This study evaluates the feasibility of local bone quality quantification using breakaway torque measurements.
  
  
  METHODS
  A torque measurement tool (DensiProbe™) was developed to determine local resistance to breakaway offered by the cancellous bone in the humeral head to quantify local bone quality. The tool was adapted to a standard locking plate (PHILOS, Synthes), allowing measurement in the positions of the six humeral head screws, as provided by the aiming device of the plate. Two hundred and seventy measurements were performed in 44 fresh cadaveric human humeri.
  
  
  RESULTS
  Handling of the tool was straight forward and provided reproducible results for the six different positions. The method allows discrimination between the respective positions with statistical significance, and thus provides reliable information on the local distribution of bone quality within the humeral head.
  
  
  CONCLUSIONS
  This study introduces a new method using breakaway torque to determine local bone quality within the humeral head in real time. Because DensiProbe is adapted to a standard locking plate, there is the potential for intraoperative application. The information provided could enable the surgeon to improve fixation of osteoporotic proximal humerus fractures.
authors.affiliation: Department of Orthopaedic Trauma, Ulm University, Ulm, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Scola
authors.forename: Florian
authors.initials: F
authors.lastname: Gebhard
authors.forename: Sebastian
authors.initials: S
authors.lastname: Weckbach
authors.forename: Christoph
authors.initials: C
authors.lastname: Dehner
authors.forename: Ronald
authors.initials: R
authors.lastname: Schwyn
authors.forename: Ladina
authors.initials: L
authors.lastname: Fliri
authors.forename: Götz
authors.initials: G
authors.lastname: Röderer
keywords: Bone quality; DensiProbe; fracture; osteoporosis; proximal humerus.