title: Computer-assisted surgery as indication of choice: total knee arthroplasty in case of retained hardware or extra-articular deformity.
abstract: OBJECTIVE
  The use of traditional cutting guides during knee arthroplasty in some cases could be extremely difficult, if not impossible, because of angular deformities, IM sclerosis, long-stemmed hip implants, or hardware within the femoral canal that cannot be removed. In these difficult cases navigation-assisted knee arthroplasty should be considered as an effective and appealing option.
  
  
  METHODS
  We present 14 cases in which ideal mechanical and prosthetic alignment was achieved with different image-free, computer-assisted navigation systems, because of an extra-articular deformity (group A, nine patients) or because of a retained implant or hardware (group B, five patients).
  
  
  RESULTS
  After a mean follow-up of 28 months (range 12-53 months), the average knee score increased overall from a mean of 33 points (range 12-63) to 78 points (range 63-90). The average functional score improved from a mean of 32 points (range 10-65) to 72 points (range 40-90). The postoperative mechanical axis ranged between 3° of varus and 3° of valgus. There was an implant revision in one patient who had a traumatic rupture of medial collateral ligament, which occurred 27 months after the index procedure.
  
  
  CONCLUSIONS
  Based on our results we think that the navigation-assisted technique provides an alternative approach to the traditional instrumentation for treating these difficult patients in an effective and less invasive manner.
authors.affiliation: Department of Orthopaedic Surgery, Santa Maria alle Scotte Hospital, Siena, Italy.
authors.forename: Domenico
authors.initials: D
authors.lastname: Tigani
authors.forename: Gilberto
authors.initials: G
authors.lastname: Masetti
authors.forename: Giacomo
authors.initials: G
authors.lastname: Sabbioni
authors.forename: Rida
authors.initials: R
authors.lastname: Ben Ayad
authors.forename: Mattia
authors.initials: M
authors.lastname: Filanti
authors.forename: Matteo
authors.initials: M
authors.lastname: Fosco
mesh_terms: D000328:Adult; D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D017760:Bone Malalignment / Q000517:prevention & control; D005260:Female; D005269:Femur / Q000473:pathology; D006801:Humans; D016268:Internal Fixators / Q000009:adverse effects; D016916:Joint Deformities, Acquired / Q000209:etiology / Q000601:surgery*; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery; D011475:Prosthesis Failure; D020127:Recovery of Function; D012086:Reoperation; D025321:Surgery, Computer-Assisted / Q000379:methods*