title: The Influence of Local Bone Density on the Outcome of One Hundred and Fifty Proximal Humeral Fractures Treated with a Locking Plate.
abstract: BACKGROUND
  There is biomechanical evidence that bone density predicts the mechanical failure of implants. The aim of this prospective study was to evaluate the influence of local bone mineral density on the rate of mechanical failure after locking plate fixation of proximal humeral fractures.
  
  
  METHODS
  We enrolled 150 patients who were from fifty to ninety years old with a closed, displaced proximal humeral fracture fixed with use of a locking plate from July 2007 to April 2010. There were 118 women and thirty-two men who had a mean age of sixty-nine years. Preoperative computed tomography (CT) scans were done to assess bone mineral density of the contralateral humerus, and dual x-ray absorptiometry of the distal end of the radius of the unaffected arm was conducted within the first six weeks postoperatively. At follow-up evaluations at six weeks, three months, and one year postoperatively, pain, shoulder mobility, strength, and multiple functional and quality-of-life outcome measures (Disabilities of the Arm, Shoulder and Hand [DASH] questionnaire; Shoulder Pain and Disability Index [SPADI]; Constant score; and EuroQuol-5D [EQ-5D]) were done and standard radiographs were made. We defined mechanical failure as all complications related to bone quality experienced within one year.
  
  
  RESULTS
  After locking plate fixation, fifty-three (35%) of 150 patients had mechanical failure; loss of reduction and secondary screw loosening with perforation were common. CT assessments of local bone mineral density showed no difference between patients with and without mechanical failure (89.82 versus 91.51 mg/cm3, respectively; p = 0.670). One-year DASH, SPADI, and Constant scores were significantly better for patients without mechanical failure (p ≤ 0.05).
  
  
  CONCLUSIONS
  We did not find evidence of an association between bone mineral density and the rate of mechanical failures, which may suggest that patients with normal bone mineral density are less prone to sustain a proximal humeral fracture. Future studies should target other discriminating factors between patients with and without mechanical failure.
  
  
  METHODS
  Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Trauma Surgery and Sports Traumatology, Medical University Innsbruck, Anichstrasse 35, A-6020 Innsbruck, Austria. E-mail address for F. Kralinger: franz.kralinger@uki.at.
authors.forename: Franz
authors.initials: F
authors.lastname: Kralinger
authors.affiliation: Department of Trauma Surgery and Sports Traumatology, Medical University Innsbruck, Anichstrasse 35, A-6020 Innsbruck, Austria. E-mail address for F. Kralinger: franz.kralinger@uki.at.
authors.forename: Michael
authors.initials: M
authors.lastname: Blauth
authors.affiliation: Institute for Biomechanics, ETH Zurich, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland.
authors.forename: Jörg
authors.initials: J
authors.lastname: Goldhahn
authors.affiliation: Department of Trauma Surgery, Kantonsspital Winterthur, Brauerstr. 15, CH-8401 Winterthur, Switzerland.
authors.forename: Kurt
authors.initials: K
authors.lastname: Käch
authors.affiliation: Department of Trauma and Reconstructive Surgery, Friederikenstift, Humboldstr. 5, D-30169 Hannover, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Voigt
authors.affiliation: Department of General, Hand, and Trauma Surgery, Stadtspital Triemli, Birmensdorferstr. 497, CH-8063 Zürich, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Platz
authors.affiliation: AO Clinical Investigation and Documentation, AO Foundation, Stettbachstrasse 6, CH-8600 Duebendorf, Switzerland.
authors.forename: Beate
authors.initials: B
authors.lastname: Hanson
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density / Q000502:physiology*; D001860:Bone Plates; D004185:Disability Evaluation; D005260:Female; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D005596:Fractures, Closed / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D011446:Prospective Studies; D011788:Quality of Life; D016059:Range of Motion, Articular / Q000502:physiology; D012784:Shoulder Fractures / Q000000981:diagnostic imaging / Q000601:surgery*; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome