title: Surface and form alterations in retrieved shoulder hemiarthroplasty.
abstract: BACKGROUND
  Shoulder hemiarthroplasty is a viable treatment for shoulder arthritis, particularly if the natural glenoid is still intact. One of the most common reasons for revision surgery is glenoid erosion, where the cartilage or bone is worn. The aim of the current study was to analyze whether the metallic articular surface of retrieved shoulder hemiarthroplasty is different from new implants. We hypothesized that the surface roughness would increase as a result of the articulation and that metallic wear would be detectable on the implants.
  
  
  METHODS
  Included were 13 retrieved and 3 new shoulder hemiarthroplasties. The surface roughness was measured on different sites of the surface (dome of the head and the rim). The implants were further measured using a coordinate measuring machine to gain information on volumetric wear and geometric alterations. The surface was analyzed with a scanning electron microscope to see marks of wear.
  
  
  RESULTS
  Compared with new implants, the surface roughness on the retrievals was significantly increased. The roughness parameters within the retrieval group were generally higher at the dome of the head than at the rim; however, this difference was not significant. Apart from shape deviations caused by deformation of the retrievals, no volumetric wear was detectable on the heads.
  
  
  CONCLUSIONS
  The current results indicate that the roughness of the surface of the implant and the shape changes occur in vivo and that the material incurs damaged caused by the articulation against the softer cartilage or bone. Increasing roughness of the humeral component may be one cause for glenoid erosion over time.
authors.affiliation: Clinic for Orthopaedic and Trauma Surgery and Laboratory of Biomechanics and Implant Research, University of Heidelberg, Heidelberg, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Bülhoff
authors.affiliation: Laboratory of Biomechanics and Implant Research, University of Heidelberg, Heidelberg, Germany.
authors.forename: Jörn
authors.initials: J
authors.lastname: Reinders
authors.affiliation: Clinic for Orthopaedic and Trauma Surgery and Laboratory of Biomechanics and Implant Research, University of Heidelberg, Heidelberg, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Zeifang
authors.affiliation: Clinic for Orthopaedic and Trauma Surgery and Laboratory of Biomechanics and Implant Research, University of Heidelberg, Heidelberg, Germany.
authors.forename: Patric
authors.initials: P
authors.lastname: Raiss
authors.affiliation: Laboratory of Biomechanics and Implant Research, University of Heidelberg, Heidelberg, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Müller
authors.affiliation: Laboratory of Biomechanics and Implant Research, University of Heidelberg, Heidelberg, Germany. Electronic address: philippe.kretzer@med.uni-heidelberg.de.
authors.forename: J Philippe
authors.initials: JP
authors.lastname: Kretzer
mesh_terms: D000368:Aged; D020878:Device Removal; D005260:Female; D062785:Hemiarthroplasty; D006801:Humans; D008297:Male; D008855:Microscopy, Electron, Scanning; D008875:Middle Aged; D012086:Reoperation; D012785:Shoulder Joint / Q000601:surgery; D000072227:Shoulder Prosthesis
keywords: Shoulder hemiarthroplasty; cup arthroplasty; form alteration; glenoid erosion; retrievals; roughness; wear