title: Is the distal radioulnar variance useful for identification of radial head prosthesis overlengthening? A cadaver study.
abstract: BACKGROUND
  Overlengthening by radial head prosthetic replacement leads to insufficient functionality and increased capitellar wear. It has been shown that in monopolar prostheses, the radial overlengthening by an overstuffed prosthesis leads to significant differences in the distal radioulnar variance at the wrist. This study evaluated ipsilateral ulnar variance as a predictor for overlengthening after implantation of a multipolar prosthesis.
  
  
  METHODS
  The radial heads of seven fresh frozen upper extremities were resected and a multipolar radial head prosthesis was implanted. Thereafter, the native radioulnar variance at the wrist was documented via fluoroscopy. The alignment of the distal radioulnar joint in neutral, pronated and supinated rotational positions of the forearm was recorded fluoroscopically, and digital image analysis was performed regarding radioulnar shifting.
  
  
  RESULTS
  Statistical analysis of the difference between native height and the manipulated states did not show consistent significant differences with stepwise overlengthening of +1.5, +3, +4.5 and +6 mm and with respect to rotational position of the forearm (p > 0.05). Interclass correlation coefficients showed excellent interobserver reliability (ICC 96%), as did tests for intraobserver reliability (ICC 98-99%).
  
  
  CONCLUSIONS
  No consistent influence of overlengthening on the alignment of the radius and ulna at the distal radioulnar joint was found after sequential overlengthening with a multipolar prosthesis. Maybe the ligamentous structures of the forearm prevent significant longitudinal dislocation of the radius, as the multipolar prosthesis gives way by at the radiocapitellar joint. According to the data of the present study, the ipsilateral wrist is not useful in diagnosing overlengthening of the radial column in multipolar prosthetic replacement of the radial head-in contrast to the reported results with monopolar prostheses.
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center, Josef-Stelzmann-Str.9, 50924, Cologne, Germany. Kilian.Wegmann@uk-koeln.de.|Cologne Center for Musculoskeletal Biomechanics, Medical Faculty, University of Cologne, Josef-Stelzmann-Str.9, 50924, Cologne, Germany. Kilian.Wegmann@uk-koeln.de.
authors.forename: Kilian
authors.initials: K
authors.lastname: Wegmann
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center, Josef-Stelzmann-Str.9, 50924, Cologne, Germany.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center, Josef-Stelzmann-Str.9, 50924, Cologne, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Strauss
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center, Josef-Stelzmann-Str.9, 50924, Cologne, Germany.|Cologne Center for Musculoskeletal Biomechanics, Medical Faculty, University of Cologne, Josef-Stelzmann-Str.9, 50924, Cologne, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Ries
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center, Josef-Stelzmann-Str.9, 50924, Cologne, Germany.|Cologne Center for Musculoskeletal Biomechanics, Medical Faculty, University of Cologne, Josef-Stelzmann-Str.9, 50924, Cologne, Germany.
authors.forename: Lars P
authors.initials: LP
authors.lastname: Müller
authors.affiliation: Arcus Klinik , Raststatter Straße 17-19, 75179, Pforzheim, Germany.
authors.forename: Klaus J
authors.initials: KJ
authors.lastname: Burkhart
mesh_terms: D002102:Cadaver; D005471:Fluoroscopy; D006801:Humans; D019736:Prostheses and Implants; D019919:Prosthesis Implantation; D011884:Radius / Q000000981:diagnostic imaging* / Q000601:surgery*; D016059:Range of Motion, Articular; D015203:Reproducibility of Results; D014457:Ulna / Q000000981:diagnostic imaging*; D014955:Wrist Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery
keywords: Forearm rotation; Multipolar prosthesis; Overlengthening; Prosthetic replacement; Radial head; Ulnar variance