Comparison of Tibial Bone Coverage of 6 Knee Prostheses: A Magnetic Resonance Imaging Study with Controlled Rotation

Abstract

The asymmetric tray provided improved tibial coverage at the expense of posterolateral and posteromedial overhang of the tibial tray.

Retrospective study of asymmetric vs symmetric tibial plates and ultracongruent vs posterior stabilized inserts in Indian population: An Indian experience of Natural Knee II

“…Increased Q-angle leads to lateral subluxation of patella, anterior knee pain and patellofemoral wear. 19,20 It has been observed that the best mediolateral or anteroposterior cortical fit of the tibial component in most cases does not result in optimal rotational alignment with the femoral component, 13 i.e. it leads to malrotation of tibial tray with respect to femoral component.…”

“…Also complete medial and lateral cortical coverage may lead to posterolateral or posteromedial overhang. 13 This posterolateral or posteromedial overhang can be reduced by internally rotating the tibial tray. But internal rotation of tibia increases the Q-angle and causes a mismatch between the femoral and tibial rotations.…”

“…Most studies 13,14 which demonstrate the superiority of asymmetric tibial base plates over symmetric tibial base plates have not been done on cases of post knee replacement patients, but they have been done on hypothetical computer generated models of anthropometric western tibia; ignoring the fact that the tibial base plate has to be implanted matching the external rotation of the femoral component. External rotation of the femoral component differs from patient to patient and population to population.…”

“…External rotation of the femoral component differs from patient to patient and population to population. Even the MRI study with controlled rotation of Wernecke et al 13 has ignored this fact and still their increased coverage of tibial plateau by asymmetric tibial plates over symmetric tibial plates is at the cost of increased posterolateral and increased posteromedial overhang. On the other hand the study of Incavo et al, 15 clearly supports my study that it is the symmetric tibial plates and not the asymmetric tibial plates which provide greater tibial coverage when no component overhang is permitted.…”

“…1 Conversely, tibial underhang results in subsidence of the tibial tray and loosening. 12,13 Traditionally, it has been proposed that maximizing tibial coverage to increase fixation by improving load transfer from the implant to the proximal tibia avoids subsidence and loosening. 14 Asymmetric tibial trays are claimed to be more anatomic in nature and therefore cover the tibial plateau more completely than symmetric tibial trays 15 ; thus decreasing the incidence of tibial tray overhang and subsidence.…”