gms | German Medical Science

Deutscher Kongress für Orthopädie und Unfallchirurgie
73. Jahrestagung der Deutschen Gesellschaft für Unfallchirurgie
95. Tagung der Deutschen Gesellschaft für Orthopädie und Orthopädische Chirurgie
50. Tagung des Berufsverbandes der Fachärzte für Orthopädie und Unfallchirurgie

21. - 24.10.2009, Berlin

Effect of varying screw configuration and bone density on reverse shoulder glenoid fixation following cyclic loading

Meeting Abstract

  • P.-H. Flurin - Clinique du Sport de Bordeaux-Mérignac, Mérignac, France
  • C. Roche - Exactech Inc., Gainesville, Florida, United States
  • T. Write - University of Florida, UF Orthopaedics and Sports Medicine Institute, Gainesville, United States
  • L. Crosby - Write State University, Dayton, United States
  • D. Hutchinson - Exactech Inc., Gainesville, Florida, United States
  • J. D. Zuckermann - NYU Hospital for Joint Diseases, New York, United States

Deutscher Kongress für Orthopädie und Unfallchirurgie. 73. Jahrestagung der Deutschen Gesellschaft für Unfallchirurgie, 95. Tagung der Deutschen Gesellschaft für Orthopädie und Orthopädische Chirurgie, 50. Tagung des Berufsverbandes der Fachärzte für Orthopädie. Berlin, 21.-24.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. DocWI46-491

DOI: 10.3205/09dkou405, URN: urn:nbn:de:0183-09dkou4059

Veröffentlicht: 15. Oktober 2009

© 2009 Flurin et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielfältigt, verbreitet und öffentlich zugänglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Gliederung

Text

Fragestellung: Little guidance exists regarding reverse shoulder test methods and performance standards. Of the bench studies that have been published, most were performed under idealized conditions (i.e. uniform bone densities of 30 lb/ft3 in which all compression screws achieve optimal fixation). Since many of the patients who would receive this type of prosthesis have compromised glenoid bone stock, the purpose of this study is to evaluate the effect of varying compression screw configurations and bone quality on reverse glenoid fixation following cyclic loading.

Methodik: Reverse glenoid components were assembled to two different densities (15 and 30 lb/ft3) of polyurethane bone substitute blocks and secured with 4.5mm compression screws in five different screw configurations and locked to the glenoid plate with locking caps. Three samples of each configuration were tested in each density bone block (n=30). Configuration #1 had four screws. Configuration #2 had three screws. Configuration #3 had two screws. Configuration #4 had 4 screws and was a revision of a pegged glenoid to a reverse shoulder. Configuration #5 had 4 screws and was a revision of a keeled glenoid to a reverse shoulder. After assembly, the humeral liner component was cyclically loaded for 5,000 cycles about a 55° arc along the glenosphere using a rotatory actuator at a rate of 0.5 Hz as a 750 N compression load was applied with a hydraulic testing machine through the center of the glenosphere. Before and after cyclic loading, the stability of the glenoid plate was quantified using a dial indicator; statistical analysis was conducted using one-tailed paired t-tests (p<0.05).

Ergebnisse und Schlussfolgerungen: The average glenoid plate motion both before and after cyclic loading (in both the sup/inf and ant/post directions) was significantly greater in the 15 lb/ft3 density bone than in the 30 lb/ft3 density bone. However, the maximum difference in glenoid motion before and after cyclic loading occurred with screw configuration #3 in the ant/post direction for both density bone blocks: 140 and 10 microns for the 15 lb/ft3 and 30 lb/ft3 density bone blocks, respectively. It should be noted that this component in the 15 lb/ft3 density block had a maximum post-cyclic motion of 178 microns. This value is greater than the generally-accepted 150 micron threshold for osseous on-growth; no other component in any other configuration had a maximum motion above this threshold. The results of this study demonstrate that the pattern of screw fixation and the degree of bone density has a direct effect on reverse shoulder glenoid fixation following cyclic loading. Furthermore, the results demonstrate that certain 'worst-case' combinations of these conditions (e.g. only 2 screws of fixation in poor quality bone) may not provide sufficient stability to achieve the osseous on-growth necessary for the long-term survival of the prosthesis.