title: Deviation between navigated and final 3-dimensional implant position in mini-invasive unicompartmental knee arthroplasty: a pilot study in 13 patients.
abstract: OBJECTIVE
  Unicompartmental knee arthroplasty (UKA) is an established method of treating isolated gonartrosis. Modern techniques such as computer-assisted surgery (CAS) and minimally invasive surgery (MIS) are attractive complementary methods to UKA. However, the positioning of the components remains a concern. Thus, we performed a prospective study to assess whether there was deviation between the navigated implant position and the final implant position.
  
  
  METHODS
  We performed UKA with MIS and CAS in 13 patients. By comparing intraoperative navigation data with postoperative computed tomography (CT) measurements, we calculated the deviation between the computer-assisted implant position and the final 3-D implant position of the femoral and tibial components.
  
  
  RESULTS
  The computer-assisted placement of the femoral and tibial component showed adequate position and consistent results regarding flexion-extension and varus-valgus. However, regarding rotation there was a large variation and 6 of 10 patients were outside the target range for both the femoral component and the tibial component.
  
  
  CONCLUSIONS
  Difficulties in assessing anatomical landmarks with the CAS in combination with MIS might be a reason for the poor rotational alignment of the components.
authors.affiliation: Department of Orthopaedics, Karolinska University Hospital, Stockholm, Sweden. nicolas.martinez-carranza@karolinska.se
authors.forename: Nicolas
authors.initials: N
authors.lastname: Martinez-Carranza
authors.forename: Lars
authors.initials: L
authors.lastname: Weidenhielm
authors.forename: Joakim
authors.initials: J
authors.lastname: Crafoord
authors.forename: Margareta
authors.initials: M
authors.lastname: Hedström
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D021621:Imaging, Three-Dimensional; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures / Q000009:adverse effects / Q000379:methods; D010865:Pilot Projects; D011446:Prospective Studies; D011475:Prosthesis Failure; D017755:Prosthesis Fitting / Q000295:instrumentation / Q000379:methods; D018570:Risk Assessment; D012494:Sampling Studies; D025321:Surgery, Computer-Assisted / Q000009:adverse effects / Q000379:methods*; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods; D016896:Treatment Outcome