title: Are We Subluxating Knees in Total Knee Arthroplasty? A Cadaveric Investigation.
abstract: In comparison to coronal, sagittal, and rotational alignment, translational alignment parameters have been widely neglected in total knee arthroplasty (TKA) so far. As there is a certain variable range of possible component placement in mediolateral, ventrodorsal, and proximodistal direction, we hypothesized that relative positions between the femoral and tibial bones are changed after TKA, resulting in a subluxation of knees.
  
  
  
  In 10 knees of Thiel-embalmed whole body cadavers, the relative position between the femur and the tibia during passive flexion was measured before and after TKA by means of a navigational device.
  
  
  
  After TKA, in extension, femoral bones in average shifted 5.3 mm (standard deviation [SD] = 4.0, P = .002) laterally and 2.4 mm (SD = 3.1, P = .038) proximally in extension which, however, decreased throughout flexion. Furthermore, the ventrodorsal femoral position was altered, resulting in a slight relative dorsal shift (2.6 mm, SD = 4.5, P = .099) in extension, which continuously changed into a ventral shift (2.6 mm, SD = 4.3, P = .087) during flexion.
  
  
  
  The present investigation reveals changed translational parameters between the tibia and the femur after TKA. The resulting subluxation of the knee may be responsible for changed kinematic patterns. These changes in tibofemoral position should be considered in future biomechanical studies. Main reasons for this effect might be a noncentral placement of tibial and femoral implants in relation to the proximal tibial and distal femoral anatomy, obscured intraoperative articular geometry, symmetric implants, and operative techniques. Smaller steps between different component sizes, asymmetric tibial implant design, or individual (anatomic) implants could help to minimize subluxation in TKA.
authors.affiliation: Department of Orthopedic Surgery, University Medical Center Regensburg, Bad Abbach, Germany.
authors.forename: Guenther
authors.initials: G
authors.lastname: Maderbacher
authors.affiliation: Department of Orthopedic Surgery, University Medical Center Regensburg, Bad Abbach, Germany.
authors.forename: Armin
authors.initials: A
authors.lastname: Keshmiri
authors.affiliation: Department of Orthopedic Surgery, University Medical Center Regensburg, Bad Abbach, Germany.
authors.forename: Hans R
authors.initials: HR
authors.lastname: Springorum
authors.affiliation: Department of Orthopedic Surgery, University Medical Center Regensburg, Bad Abbach, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Greimel
authors.affiliation: Department of Orthopedic Surgery, University Medical Center Regensburg, Bad Abbach, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Grifka
authors.affiliation: Department of Orthopedic Surgery, University Medical Center Regensburg, Bad Abbach, Germany.
authors.forename: Clemens
authors.initials: C
authors.lastname: Baier
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000379:methods*; D001696:Biomechanical Phenomena; D002102:Cadaver; D005269:Femur / Q000601:surgery; D006801:Humans; D004204:Joint Dislocations; D031221:Knee Dislocation / Q000209:etiology*; D007719:Knee Joint / Q000502:physiology / Q000601:surgery*; D016059:Range of Motion, Articular; D013977:Tibia / Q000601:surgery
keywords: TKA; alignment; biomechanic; cadaver; component alignment; kinematic