title: Position of the prosthesis components in total ankle replacement and the effect on motion at the replaced joint.
abstract: OBJECTIVE
  In some cases of total ankle replacement, perfect alignment of the prosthetic components is not achieved. This study analyses the extent to which component positioning is critical for the final range of motion.
  
  
  METHODS
  Fourteen patients undergoing total ankle replacement were assessed preoperatively and postoperatively at seven and 13 months follow-up. X-ray pictures of the ankle were taken in static double leg stance, i.e. at neutral joint position, and in maximum plantarflexion and dorsiflexion. Measurements were obtained by a specially devised computer program based on anatomical reference points digitised on the radiograms. These allowed calculation of the position and orientation of the components in the sagittal and coronal planes, together with the joint range of motion.
  
  
  RESULTS
  The mean range of motion was about 34 degrees at the first follow-up and maintained at the second. Tibial and talar components were more anterior than the mid-tibial shaft in 11 and nine patients, respectively. Mean inclination was about four degrees posterior for the tibial component and nearly one degree anterior for the talar component. A significantly larger range of motion was found in ankles both with the talar component located and inclined more anteriorly than the tibial.
  
  
  CONCLUSIONS
  Correlation, though weak, was found between motion at the replaced ankle and possible residual subluxation and inclination of the components. However, a satisfactory range of motion was also achieved in those patients where recommended locations for the components could not be reached because of the size of the original joint deformity.
authors.affiliation: Movement Analysis Laboratory, Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136, Bologna, Italy. francesco.cenni@ior.it
authors.forename: Francesco
authors.initials: F
authors.lastname: Cenni
authors.forename: Alberto
authors.initials: A
authors.lastname: Leardini
authors.forename: Andrea
authors.initials: A
authors.lastname: Cheli
authors.forename: Fabio
authors.initials: F
authors.lastname: Catani
authors.forename: Claudio
authors.initials: C
authors.lastname: Belvedere
authors.forename: Matteo
authors.initials: M
authors.lastname: Romagnoli
authors.forename: Sandro
authors.initials: S
authors.lastname: Giannini
mesh_terms: D000328:Adult; D000368:Aged; D016512:Ankle Injuries / Q000601:surgery; D000843:Ankle Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D001172:Arthritis, Rheumatoid / Q000601:surgery; D058737:Arthroplasty, Replacement, Ankle / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D017760:Bone Malalignment / Q000000981:diagnostic imaging / Q000209:etiology; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000209:etiology; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000601:surgery; D011183:Postoperative Complications; D017755:Prosthesis Fitting / Q000009:adverse effects / Q000379:methods*; D011859:Radiography; D016059:Range of Motion, Articular