Wear Behavior of an Unstable Knee: Stabilization via Implant Design?

Abstract

Background. Wear-related failures and instabilities are frequent failure mechanisms of total knee replacements. High-conforming designs may provide additional stability for the joint. This study analyzes the effects of a ligamentous insufficiency on the stability and the wear behavior of a high-conforming knee design. Methods. Two simulator wear tests were performed on a high-conforming total knee replacement design. In the first, a ligamentous-stable knee replacement with a sacrificed anterior cruciate ligament was simulated. In the second, a ligamentous-unstable knee with additionally insufficient posterior cruciate ligament and medial collateral ligament was simulated. Wear was determined gravimetrically and wear particles were analyzed. Implant kinematics was recorded during simulation. Results. Significantly higher wear rates (P ≤ 0.001) were observed for the unstable knee (14.58 ± 0.56 mg/106 cycles) compared to the stable knee (7.97 ± 0.87 mg/106 cycles). A higher number of wear particles with only small differences in wear particle characteristics were observed. Under unstable knee conditions, kinematics increased significantly for translations and rotations (P ≤ 0.01). This increase was mainly attributed to higher tibial posterior translation and internal rotations. Conclusion. Higher kinematics under unstable test conditions is a result of insufficient stabilization via implant design. Due to the higher kinematics, increased wear was observed in this study.

Patellar tendon buckling in post-operative total knee arthroplasty patients is more prominent than in healthy controls

“…Weaker quadriceps would have presumably less passive stiffness [32] which, due to the patellar tendon's anatomical function as part of the quadriceps muscle-tendon unit [33,34], would most likely increase buckling within the patellar tendon. A potential effect of such extreme buckling is joint instability, which can lead to abnormal knee joint loading and increased degenerative wear [35]. Pre-operative differences in patellar tracking could also be relevant to consider.…”

Knee Function and Subjective Stability Following Total Condylar Arthroplasty in Joints with Preoperative Varus or Valgus Deformity

“…Po wszech nie wia do mo, iż zbyt "cia sne" ko la no z nad mier ną zwar to ścią wię za deł po bocz nych, mo że być przy czy ną do le gli wo ści bó lo wych i ogra ni cze nia za kre su ru chu [10]. Z dru giej stro ny, nie sta bil ność jest jed ną z naj częst szych przy czyn nie po wo dzeń endo pro te zo pla sty ki sta wu ko la no we go [11]. Nie któ rzy au to rzy do wo dzą, iż pe wien sto pień "lu zu" w sta wie jest nie zbęd ny i przy czy nia się do zmniej sze nia odczu wa nia bó lu po ope ra cyj ne go, a ta kże umo żli wia więk szy za kres ru chu [12,13].…”

“…It is well known that too tight collateral ligaments may result in knee pain and ROM limitations [10]. On the other hand, instability is one of the main causes of implant failure [11]. However, some investigators argue that a certain degree of laxity in the joint may be related to decreased postoperative pain and a better range of motion [12;13].…”

The Effect of Implant Conformity on Muscle Force Requirements in the Implanted Knee

“…Furthermore, the relative sliding of components and higher compressive load can lead to greater implant wear. More conforming implant designs that provide greater knee stabilization have been shown to have significantly lower wear rates (Brockett et al, 2017;Reinders et al, 2014).…”

“…However, muscular co-contraction can be mechanically inefficient and can hinder joint functionality. Furthermore, the relative sliding of components and higher compressive load can lead to greater implant wear (Brockett et al, 2017;Reinders et al, 2014). TKR patients present with slowed gait, reduced range of motion and prolonged muscular co-contractions during stance (Benedetti et al, 2003).…”