title: X-treme CT analysis of cancellous bone at the rotator cuff insertion in human individuals with osteoporosis: superficial versus deep quality.
abstract: OBJECTIVE
  Rotator cuff (RC) repair-especially in the elderly population-is problematic since the patients suffer to a high extent from bone mineral density loss at the reattachment site. Therefore, the study was primarily driven by the question whether it is possible to reach more or qualitatively better cancellous bone and thus a more stable postoperative result if anchors with greater length are used for RC repair and/or the conventional anchors are screwed deeper into the bone. In anatomical terms, the question is raised whether cancellous bone is of better quality close to or far off the RC enthesis.
  
  
  METHODS
  Axial HRqCT scans (X-tremeCT, Scanco Medical) of 36 human cadaveric humeral heads (75 ± 11 years) were performed to determine the ratio of bone volume to total volume (BV/TV), trabecular thickness (Trab Th), number of trabecles (Trab N), trabecular separation (Trab Sp) as well as non-metric indices such as connectivity density (Conn Dens) and structure model index (SMI). Within the greater tuberosity (GT), 6 volumes of interest (VOI) (A1, B1, C1, A2, B2, C2), in the lesser tuberosity (LT) 2 VOIs (D1, D2) and one control VOI in the subchondral bone were set. The analyzed bone cylinder of each VOI was divided into a superficial and a deep portion.
  
  
  RESULTS
  The parameters BV/TV, Trab N, Trab Th and Conn Dens in all volumes of the GT and LT revealed higher values in the superficial portion reaching different levels of significance (p < 0.001/<0.05). The only parameter presenting a higher value in the deep portion was Trab Sp, but this was the case for all GT and LT regions. Interestingly, the difference between the superficial and deep portion reached significance for the non-metric parameter SMI in no volume of the GT/LT, although the higher values were found superficially.
  
  
  CONCLUSIONS
  Our data show that cancellous bone presents with decreasing bone quality when analyzing increasingly deeper portions of the bone cylinders of the GT and LT starting at the articular surface. This information seems to be crucial for shoulder surgeons, especially when treating elderly patients. Our results clearly prove that screwing in anchors to a deeper extent will not improve stability, since the deeper bone stock is of worse quality.
authors.affiliation: Department of Trauma Surgery, Klinikum Rechts der Isar, Technische Universitaet, Munich, Ismaningerstrasse 22, Munich, Germany. kirchhoff@lrz.tu-muenchen.de
authors.forename: Chlodwig
authors.initials: C
authors.lastname: Kirchhoff
authors.forename: Sonja
authors.initials: S
authors.lastname: Kirchhoff
authors.forename: Christoph M
authors.initials: CM
authors.lastname: Sprecher
authors.forename: Philipp
authors.initials: P
authors.lastname: Ahrens
authors.forename: Andreas B
authors.initials: AB
authors.lastname: Imhoff
authors.forename: Stefan
authors.initials: S
authors.lastname: Hinterwimmer
authors.forename: Stefan
authors.initials: S
authors.lastname: Milz
authors.forename: Volker
authors.initials: V
authors.lastname: Braunstein
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D002102:Cadaver; D005260:Female; D006801:Humans; D006811:Humerus / Q000000981:diagnostic imaging* / Q000601:surgery; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000000981:diagnostic imaging* / Q000601:surgery; D017006:Rotator Cuff / Q000601:surgery*; D000070636:Rotator Cuff Injuries; D014057:Tomography, X-Ray Computed