<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:creator>Spross C</dc:creator>
  <dc:creator>Ebneter L</dc:creator>
  <dc:creator>Benninger E</dc:creator>
  <dc:creator>Erschbamer M</dc:creator>
  <dc:creator>Erhardt J</dc:creator>
  <dc:creator>Jost B</dc:creator>
  <dc:date>2013</dc:date>
  <dc:description xmlns:ns0="xml" ns0:lang="en">BACKGROUND
Proximal humeral fractures with substantial metaphyseal comminution are challenging to treat. In the elderly with osteoporotic bone, arthroplasty sometimes remains the only valuable option; however, the minimally required length of stem fixation is not known. The aim of this study was to investigate the primary stability of cemented short- and long-stem prostheses with different intramedullary fracture bypass lengths.


MATERIALS AND METHODS
Osteoporotic composite bone models of the humerus (Synbone, Malans, Switzerland) with 3 different fracture levels (group A, 6 cm distal to surgical neck; group B, 7 cm distal to surgical neck; and group C, 8 cm distal to surgical neck) were prepared with a cemented standard short (S)- or long (L)-stem prosthesis and were tested for torque to failure. As a reference, we used models with intact bone (group R-O) and a short-stem prosthesis implanted at the surgical neck (group R-P). The radiographic bypass index (BI) was calculated before testing (fracture level to stem tip [in millimeters]/outer cortical diameter at fracture level [in millimeters]).


RESULTS
The resulting BIs of each group were as follows: 1.7 in group A-S, 3.4 in group A-L, 1.4 in group B-S, 3.2 in group B-L, 1.0 in group C-S, and 2.9 in group C-L. Compared with group R-O, the torques to failure of groups B-S and C-S were significantly lower, whereas only group C-S was significantly weaker than group R-P (P &lt; .01). Comparing short- and long-stem bypasses of different fracture heights, we found that only group C-L showed a significantly higher resistance to torque (P &lt; .01).


CONCLUSIONS
A short-stem bypass with a BI of 1.7 was sufficient for primary stability tested by torque to failure in this biomechanical setting. For smaller BIs, a long-stem prosthesis should be considered.


LEVEL OF EVIDENCE
Basic science study, biomechanics.</dc:description>
  <dc:identifier>https://sonar.ch/global/documents/529</dc:identifier>
  <dc:language>eng</dc:language>
  <dc:relation>info:eu-repo/semantics/altIdentifier/doi/10.1016/j.jse.2013.02.012</dc:relation>
  <dc:relation>info:eu-repo/semantics/altIdentifier/pmid/23619248</dc:relation>
  <dc:source>Journal of shoulder and elbow surgery. - 2013</dc:source>
  <dc:subject xmlns:ns1="xml" ns1:lang="en">Basic Science Study</dc:subject>
  <dc:subject xmlns:ns2="xml" ns2:lang="en">Biomechanics</dc:subject>
  <dc:subject xmlns:ns3="xml" ns3:lang="en">Intramedullary bypass</dc:subject>
  <dc:subject xmlns:ns4="xml" ns4:lang="en">arthroplasty</dc:subject>
  <dc:subject xmlns:ns5="xml" ns5:lang="en">comminution</dc:subject>
  <dc:subject xmlns:ns6="xml" ns6:lang="en">fracture</dc:subject>
  <dc:subject xmlns:ns7="xml" ns7:lang="en">proximal humerus</dc:subject>
  <dc:subject xmlns:ns8="xml" ns8:lang="en">Aged</dc:subject>
  <dc:subject xmlns:ns9="xml" ns9:lang="en">Arthroplasty, Replacement</dc:subject>
  <dc:subject xmlns:ns10="xml" ns10:lang="en">Biomechanical Phenomena</dc:subject>
  <dc:subject xmlns:ns11="xml" ns11:lang="en">Female</dc:subject>
  <dc:subject xmlns:ns12="xml" ns12:lang="en">Fractures, Comminuted</dc:subject>
  <dc:subject xmlns:ns13="xml" ns13:lang="en">Humans</dc:subject>
  <dc:subject xmlns:ns14="xml" ns14:lang="en">Humerus</dc:subject>
  <dc:subject xmlns:ns15="xml" ns15:lang="en">Joint Prosthesis</dc:subject>
  <dc:subject xmlns:ns16="xml" ns16:lang="en">Models, Biological</dc:subject>
  <dc:subject xmlns:ns17="xml" ns17:lang="en">Osteoporosis</dc:subject>
  <dc:subject xmlns:ns18="xml" ns18:lang="en">Radiography</dc:subject>
  <dc:subject xmlns:ns19="xml" ns19:lang="en">Shoulder Fractures</dc:subject>
  <dc:subject xmlns:ns20="xml" ns20:lang="en">Shoulder Joint</dc:subject>
  <dc:subject xmlns:ns21="xml" ns21:lang="en">Torque</dc:subject>
  <dc:title xmlns:ns22="xml" ns22:lang="en">Short- or long-stem prosthesis for intramedullary bypass of proximal humeral fractures with severe metaphyseal bone loss: evaluation of primary stability in a biomechanical model.</dc:title>
  <dc:type>http://purl.org/coar/resource_type/c_6501</dc:type>
</oai_dc:dc>