Internal Rotation of the Tibial Component is Frequent in Stiff Total Knee Arthroplasty

Abstract

Background Stiffness complicating TKA is a complex and multifactorial problem. We suspected internally rotated components compromised motion because of pain, patellar maltracking, a tight medial flexion gap, and limited femoral rollback on a conforming lateral tibial condyle. Questions/purposes We sought to determine: (1) the incidence of internal rotation of the femoral and tibial components in stiff TKAs; (2) if revision surgery that included correction of rotational positioning improved pain, ROM, and patellar tracking; and (3) if revision altered nonrotational radiographic parameters.Methods From a cohort of 52 patients with TKAs revised for stiffness, we performed CT scans of 34 before and 18 after revision to quantify rotational positioning of the femoral and tibial components using a previously validated scanning protocol.

Maximizing Tibial Coverage Is Detrimental to Proper Rotational Alignment

“…Bonnin et al [7] noted that correct positioning of the tibial component requires that two criteria be fulfilled simultaneously; first, implant rotation ensuring optimal knee kinematics and second, optimized prosthetic coverage ensuring uniform load transfer. The concern that too little coverage causes an increase in stress of the tibia-implant interface has not been shown to decrease the success of implants, unless coverage was less than 75% [3,11,16,18]. No tray in this study had less than 74% coverage.…”

“…However, multiple recent publications demonstrate that internal tibial component rotation still occurs and is a source of failure in TKA [3,6,17,18]. Correct rotation can be achieved using symmetric or asymmetric components, but the extent of coverage (especially posteromedial) may vary depending on component design.…”

“…There is also literature to demonstrate that accepting some uncovered posterior medial tibial bone aids in the proper rotational positioning of the tibial component [12]. There is a lack of data to support the concern that decreased tibial coverage is the cause of tibial subsidence and several long-term studies report very low rates of tibial loosening [3,11,16]. Nonetheless, we still encounter many failed TKAs because coverage has been maximized at the expense of proper rotation.…”

“…However, tibial coverage rarely exceeds 78%, and several authors have proposed a minimum of 75% coverage for adequate fixation; however, this is based on mechanical data, and the degree to which this is clinically relevant is unknown [3].…”

Design rationale for customized TKA: a new idea or revisiting the past?

“…But the slightly undersized tibial tray allows the surgeon no more than 5 degrees of internal or external rotation to optimize the tray between the ML axis and the axis of the medial 1/3 of the tibial tubercle [21•]. This is an important feature since correctly rotated femoral and tibial components have been shown to decrease pain and stiffness after total knee replacement [22,23].…”