title: Identification of overlengthening after replacement of the radial head with a bipolar prosthesis.
abstract: BACKGROUND
  Overlengthening of the radial column leads to insufficient functionality and increased capitellar wear. Methods to detect or prevent overlengthening have been described for monopolar prostheses. The aim of this study was to evaluate whether one such method described by Athwal et al. is also applicable for a bipolar prosthesis.
  
  
  METHODS
  The radial heads of six fresh frozen upper extremities were resected. A bipolar radial head prosthesis was implanted in each, and the effects of sequential overlengthening on the alignment of the radiocapitellar and ulnohumeral joint line were recorded by fluoroscopic images. Digital image analysis and estimation of overlengthening followed according to the method described by Athwal et al.
  
  
  RESULTS
  Statistical analysis of the estimated and actual differences between the native state and bipolar replacement of the radial head with stepwise overlengthening of 1.5, 3, 4.5, and 6 mm showed a specificity of 86 % but consistently underestimated the amount of overlengthening with a sensitivity of only 61 %.
  
  
  CONCLUSIONS
  The method described by Athwal et al. for the identification of overlengthening by a monopolar prosthesis was not found to be reliable for ruling out or quantifying overlengthening of the tested bipolar prosthesis. However, the use of the method to detect (rule in) overlengthening may be acceptable in certain circumstances. A reliable method for postoperative quantification of overlengthening by bipolar prostheses has still to be found.
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center, 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: K
authors.initials: K
authors.lastname: Wegmann
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center, Cologne, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Lamsfuss
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center, Cologne, Germany.|Cologne Center for Musculoskeletal Biomechanics, Medical Faculty, University of Cologne, Josef-Stelzmann-Str.9, 50924, Cologne, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Ries
authors.affiliation: Institute of Anatomy I, University of Cologne, Cologne, Germany.
authors.forename: W F
authors.initials: WF
authors.lastname: Neiss
authors.affiliation: Institute of Medical Statistics, Informatics and Epidemiology, University of Cologne, Cologne, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Franklin
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center, Cologne, Germany.|Cologne Center for Musculoskeletal Biomechanics, Medical Faculty, University of Cologne, Josef-Stelzmann-Str.9, 50924, Cologne, Germany.
authors.forename: L P
authors.initials: LP
authors.lastname: Müller
authors.affiliation: Clinic for Shoulder Surgery, Bad Neustadt/Saale, Germany.
authors.forename: K J
authors.initials: KJ
authors.lastname: Burkhart
mesh_terms: D000369:Aged, 80 and over; D002102:Cadaver; D004551:Elbow Joint / Q000601:surgery*; D058569:Elbow Prosthesis / Q000009:adverse effects*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D057072:Intra-Articular Fractures / Q000175:diagnosis / Q000601:surgery*; D008297:Male; D011183:Postoperative Complications / Q000175:diagnosis* / Q000517:prevention & control; D011474:Prosthesis Design; D019919:Prosthesis Implantation / Q000009:adverse effects*; D011884:Radius / Q000293:injuries / Q000601:surgery*; D011885:Radius Fractures / Q000175:diagnosis / Q000601:surgery*; D012092:Replantation; D000092464:Elbow Injuries
keywords: Bipolar prosthesis; Forearm rotation; Overlengthening; Prosthetic replacement; Radial head; Ulnohumeral joint