Various Types of Medial Tibial Bone Resorption after Total Knee Arthroplasty Using a Thick Cobalt Chromium Tibial Baseplate

Abstract

Recent literature has implicated a thick cobalt chromium baseplate as a potential source of stress shielding and medial tibial bone resorption after total knee arthroplasty (TKA) in a Western population. The purpose was to calculate the incidence of various types and severity of medial tibial bone resorption utilizing a novel classification system after TKA with a thick cobalt chromium baseplate in Asian patients. Five hundred TKAs using Attune prostheses with mean follow-up of 3.4 years were evaluated, using the prospective radiographic data. The mean age was 71.3 years. The preoperative mechanical axis was varus, 11.2 degrees. The type and severity of medial tibial bone resorption were categorized as type U (resorption under the tibial baseplate up to 50% [U1] or beyond 50% [U2] of medial tibial tray width), C (resorption around the penetrated cement under the baseplate), and M (resorption on the medial tibial cortex without extension to the baseplate). Bone resorption of medial proximal tibia was observed in 96 knees (19.2%). Types U1 and U2 were seen in 46 and 28 knees, respectively. Type C was observed in 12 knees and type M in 10 knees. The type U resorption group had significantly more preoperative varus deformity (varus 12.9 vs. 10.9 degrees, p = 0.017). Medial tibial bone resorption after TKAs using a thick cobalt chromium baseplate is not uncommon and has various locations, types, and severities. The medial tibial bone resorption might be related to various causes, including stress shielding, thermal necrosis from cement in the bony hole, and bony devascularization. The type-U resorption has to be closely observed in patients with preoperative severe varus deformity. This is a Level IV study.

High rate of radiolucent lines following the cemented original design of the ATTUNE total knee arthroplasty

“…One study defined any medial tibial bone resorption on AP and lateral radiographs as a radiolucency, and classified it using a novel classification system; data from this study referring to RLLs at the implant-cement interface were extracted and used only for the medial tibia RLL analysis. 28…”

“… ‡ Medial tibia (AP): included one study which defined as radiolucency any medial tibial bone resorption, but only radiolucencies reported for zones of medial tibial baseplate included. 28 …”

“…21,25,27 Analysis of three studies reporting rates of loosening of TKAs with PS components showed a rate of 1.5% (95% CI 0.1% to 22.6%) (heterogeneity: tau 2 = 3.936, I 2 = 93.702, Q = 79.394; p < 0.001). 21,25,28…”

“…Meta-analysis of six studies reporting on revision due to loosening showed an overall rate of revision of 0.9% (95% CI 0.2% to 5.1%) (heterogeneity: tau 2 = 3.587, I 2 = 93.131, Q = 72.789; p < 0.001). 21,25,28-31…”

“…The ATTUNE system uses a thick CoCr tibial baseplate, and there has been a report of an increased rate of medial tibial bone resorption with the ATTUNE TKA, presenting in various locations and severities around the baseplate. 28…”