Analysis of Biomechanical Differences Between Condylar Constrained Knee and Rotating Hinged Implants: A Numerical Study

Abstract

Background: Different levels of constraint for total knee arthroplasty can be considered for revision surgeries. While prior studies have assessed the clinical impact and patient outcomes of condylar constrained knee (CCK) and rotating hinged (RTH) implants, nowadays little is known about the biomechanical effects induced by different levels of constraint on bone stress and implant micromotions. Methods: CCK and RTH implant models were analyzed using a previously validated numerical model. Each system was investigated during a squat and a lunge motor task. The force in the joint, the bone and implant stresses, and micromotions in this latter were analyzed and compared among designs. Results: Different activities induced similar bone stress distributions in both implants. The RTH implant induces mostly high stress compared to the CCK implant, especially in the region close to tip of the stem. However, in the proximal tibia, the stresses achieved with the CCK implant is higher than the one calculated for the RTH design, due to the presence of the post-cam system. Accordingly, the condylar constrained design shows higher implant micromotions due to the greater torsional constraint. Conclusion: Different levels of constraint in revision arthroplasty were always associated with different biomechanical outputs. RTH implants are characterized by higher tibial stress especially in the region close to the stem tip; condylar implants, instead, increase the proximal tibial stress and therefore implant micromotions, as a result of the presence of the post-cam mechanism. Surgeons will have to consider these findings to guarantee the best outcome for the patient and the related change in the bone stress and implant fixation induced by different levels of constrain in a total knee arthroplasty.

Survivorship of highly constrained prostheses in primary and revision total knee arthroplasty: analysis of 6070 cases

“…7,[18][19][20] A recent biomechanical study has compared the bone stresses and implant micromotions of a HTKA to FSTKA prosthesis. 21 This study has demonstrated that HTKA prostheses have the highest implant to bone stress, especially at the tip of the stems. This could explain the mechanism for the higher periprosthetic fracture rate seen with these implants.…”

“…The reasons for the increased periprosthetic fracture risk with HTKA prosthesis remains uncertain, although this complication has been noted in other small case series of HTKA prostheses 7,18–20 . A recent biomechanical study has compared the bone stresses and implant micromotions of a HTKA to FSTKA prosthesis 21 . This study has demonstrated that HTKA prostheses have the highest implant to bone stress, especially at the tip of the stems.…”

High ten-year implant survivorship and low patellofemoral complication rate for S-ROM rotating-hinge implants in revision total knee arthroplasty

“…We have reported high survivorship at ten years, in keeping with contemporary literature. In their recent biomechanical study comparing stresses of constrained condylar knee (CCK) with rotating-hinge implants, Andreani et al 24 reported interesting findings where rotating-hinge implant induced high stress compared to the CCK, especially in the region close to tip of the stem. However, higher stresses in the proximal tibia were seen with CCK implant due to the post-cam system, leading to higher implant micromotions due to greater torsional constraint.…”

Biomechanical Analysis of the Use of Stems in Revision Total Knee Arthroplasty

“…All the steps used for the development of the model, from geometry definition, material models and properties, loads, boundary conditions, and mesh, were performed in strict agreement with the previously validate finite element model [ 22 , 25 , 26 ].…”

“…A cobalt-chromium alloy (CoCr), a titanium alloy (Ti-6Al-4V), and an ultra-high-molecular-weight-polyethylene (UHMWPE) were respectively used for the femoral component, tibial tray, and tibial insert; as with the previous study, homogeneous isotropic models were selected for these materials [ 16 , 17 , 43 ] and their properties were the following: for CoCr: E = 220 GPa, ν = 0.3 [ 25 , 32 ]; for titanium: E = 117 GPa, ν = 0.3 [ 30 , 35 ]; and for UHMWPE: E = 0.685 GPa, ν = 0.4 [ 28 , 30 , 40 , 42 ].…”