title: Does a modified gap-balancing technique result in medial-pivot knee kinematics in cruciate-retaining total knee arthroplasty? A pilot study.
abstract: BACKGROUND
  Normal knee kinematics is characterized by posterior femorotibial rollback with tibial internal rotation and medial-pivot rotation in flexion. Cruciate-retaining TKAs (CR-TKAs) do not reproduce normal knee kinematics.
  
  
  OBJECTIVE
  We hypothesized a more anatomic reconstruction of the medial femoral condyle, simultaneously preserving the tension of the PCL and medial collateral ligament, resulted in (1) medial-pivot rotation and tibial internal rotation, (2) lateral femoral rollback, and (3) reduced liftoff.
  
  
  METHODS
  We compared 10 patients who underwent CR-TKA using the new technique at their 1-year followup to a matched control group of nine patients using a traditional gap-balancing technique at their 2- to 4-year followup. All patients received lateral radiographs in extension and flexion, which we utilized for three-dimensional implant matching to calculate tibial internal rotation, lateral rollback, and lateral liftoff in extension and flexion.
  
  
  RESULTS
  The new gap-balancing technique resulted in a median of 3.5° tibial internal rotation with 2.7-mm rollback of the lateral femoral condyle relative to the medial condyle in flexion, which was different from the control group. We found no differences in liftoff between the groups.
  
  
  CONCLUSIONS
  The new technique resulted in tibial internal rotation with flexion and lateral rollback comparing the lateral to the medial condyle in flexion, but no differences in condylar liftoff. These preliminary results were comparable to published kinematic results of an asymmetric CR-TKA or medial-pivot CR-TKA but not to symmetric CR-TKA.
authors: Department of Orthopedic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA. wfitz@partners.org
authors: Wolfgang
authors: W
authors: Fitz
authors: Sonal
authors: S
authors: Sodha
authors: William
authors: W
authors: Reichmann
authors: Tom
authors: T
authors: Minas
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods*; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D016001:Confidence Intervals; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000601:surgery*; D010865:Pilot Projects; D016119:Posterior Cruciate Ligament / Q000601:surgery*; D004856:Postural Balance / Q000502:physiology; D011300:Preoperative Care / Q000379:methods; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D016059:Range of Motion, Articular / Q000502:physiology*; D018570:Risk Assessment; D012399:Rotation; D018709:Statistics, Nonparametric; D013977:Tibia / Q000000981:diagnostic imaging / Q000502:physiology; D013997:Time Factors; D016896:Treatment Outcome