title: In vivo comparison of femorotibial contact positions for press-fit posterior stabilized and posterior cruciate-retaining total knee arthroplasties.
abstract: The objective of this study was to determine the in vivo medial and lateral femorotibial condyle contact positions for 20 subjects having either a posterior cruciate-retaining (PCR) or posterior-stabilized (PS) total knee arthroplasty (TKA) while sitting and kneeling. The two-dimensional radiographic images were converted into three-dimensional images using an iterative computer model-fitting technique. Anteroposterior contact positions, axial rotation, and condylar lift-off were assessed for each subject. In a seated position, the femorotibial contact points were, on average, posterior for both TKA groups (PCR: medial = -2.4 mm, lateral = -3.4 mm; PS: medial = -5.1 mm, lateral = -8.9 mm; medial, P=.21; lateral, P=.08). In a kneeling position, the contact position shifted anteriorly for the PCR TKA group (medial = 0.9 mm, lateral = -0.8 mm), whereas the contact positions in the PS TKA group remained posterior (medial = -5.6 mm, lateral = -8.3 mm; medial, P=.002; lateral, P=.0004). It is hypothesized that while in a kneeling position, the posterior cruciate ligament has less resistance to the anterior thrust of the femur relative to the tibia than in a PS TKA, in which this force is absorbed in the cam-and-post mechanism.
authors.affiliation: Rocky Mountain Musculoskeletal Research Laboratory, Denver, Colorado, USA. rkomistek@rmmrl.org
authors.forename: Richard D
authors.initials: RD
authors.lastname: Komistek
authors.forename: Richard D
authors.initials: RD
authors.lastname: Scott
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Dennis
authors.forename: David
authors.initials: D
authors.lastname: Yasgur
authors.forename: Dylan T
authors.initials: DT
authors.lastname: Anderson
authors.forename: Mary E
authors.initials: ME
authors.lastname: Hajner
mesh_terms: D019645:Arthroplasty, Replacement, Knee; D003198:Computer Simulation; D005269:Femur / Q000033:anatomy & histology; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging; D016119:Posterior Cruciate Ligament / Q000502:physiology*; D011187:Posture; D017755:Prosthesis Fitting; D011859:Radiography; D013977:Tibia / Q000033:anatomy & histology