title: Computer guided restoration of joint line and femoral offset in cruciate substituting total knee arthroplasty.
abstract: OBJECTIVE
  This prospective study aimed to evaluate radiographically, change in joint line and femoral condylar offset with the optimized gap balancing technique in computer-assisted, primary, cruciate-substituting total knee arthroplasties (TKAs).
  
  
  METHODS
  One hundred and twenty-nine consecutive computer-assisted TKAs were evaluated radiographically using pre- and postoperative full-length standing hip-to-ankle, antero-posterior and lateral radiographs to assess change in knee deformity, joint line height and posterior condylar offset.
  
  
  RESULTS
  In 49% of knees, there was a net decrease (mean 2.2mm, range 0.2-8.4mm) in joint line height postoperatively whereas 46.5% of knees had a net increase in joint line height (mean 2.5mm, range 0.2-11.2mm). In 93% of the knees, joint line was restored to within ± 5 mm of preoperative values. In 53% of knees, there was a net increase (mean 2.9 mm, range 0.2-12 mm) in posterior offset postoperatively whereas 40% of knees had a net decrease in posterior offset (mean 4.2mm, range 0.6-20mm). In 82% of knees, the posterior offset was restored within ± 5 mm of preoperative values.
  
  
  CONCLUSIONS
  Based on radiographic evaluation in extension and at 30° flexion, the current study clearly demonstrates that joint line and posterior femoral condylar offset can be restored in the majority of computer-assisted, cruciate-substituting TKAs to within 5mm of their preoperative value. The optimized gap balancing feature of the computer software allows the surgeon to simulate the effect of simultaneously adjusting femoral component size, position and distal femoral resection level on joint line and posterior femoral offset.
authors.affiliation: Department of Orthopaedic Surgery, Breach Candy Hospital, Mumbai, India. gautams10@gmail.com
authors.forename: Gautam M
authors.initials: GM
authors.lastname: Shetty
authors.forename: Arun
authors.initials: A
authors.lastname: Mullaji
authors.forename: Sagar
authors.initials: S
authors.lastname: Bhayde
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery*; D005500:Follow-Up Studies; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D016119:Posterior Cruciate Ligament / Q000000981:diagnostic imaging / Q000601:surgery*; D011184:Postoperative Period; D011446:Prospective Studies; D011859:Radiography; D016059:Range of Motion, Articular; D025321:Surgery, Computer-Assisted / Q000379:methods*; D016896:Treatment Outcome