Influence of increasing construct constraint in the presence of posterolateral deficiency at knee replacement: A biomechanical study.
When faced with posterolateral corner (PLC) deficiency, surgeons must choose a total knee replacement (TKR) construct that provides the appropriate level of constraint. This should match the internal constraint of the device to the soft tissue host laxity pattern. Little guidance is available peroperatively, with factors influencing final component choice remaining ill defined. This study aimed to quantify the effect of PLC insufficiency on the "envelope of laxity" (EoL) after TKR and the effect of increasingly component constraint upon knee behavior through a functional arc of flexion. Using computer navigation, mixed effect modeling and loaded cadaveric legs--laxity was quantified under separate states: the native knee, after implantation of a posterior stabilized (PS)-TKR, after sectioning the lateral (fibular) collateral ligament and popliteus tendon (PS-TKR-PLC), and after re-implantation with a semi-constrained "total stabilized" knee replacement (TS-TKR). Laxity was quantified from 0 to 110° of flexion for anterior draw, varus-valgus, and internal-external rotation. Implantation of the PS-TKR was consistently associated with increased constraint when compared to the native knee. PLC sectioning led to significantly increased laxity during varus stress from mid to deep flexion. Revision to a TS-TKR construct restored constraint mimicking that of the primary state but only for the arc of motion 0-90°. In a posterolateral deficient state, a fixed bearing semi-constrained TS-TKR restored the knee to near normal kinematics but this was only achieved from an arc of motion 0-90° of flexion. At higher flexion angles, there remained an unfavorable laxity pattern with varus stress opening.
Freeman Hospital, High Heaton, Newcastle upon Tyne, NE7 7DN, United Kingdom.
Kanishka M
KM
Ghosh
Freeman Hospital, High Heaton, Newcastle upon Tyne, NE7 7DN, United Kingdom.
William A
WA
Manning
School of Biology, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom.
Alasdair P
AP
Blain
School of Biology, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom.
Steve P
SP
Rushton
Biomechanics, Mechanical Engineering, Imperial College London, London, SW7 2AZ, United Kingdom.
Lee M
LM
Longstaff
University Hospital of North Durham, North Road, Durham, County Durham, DH1 5TW, United Kingdom.
Andrew A
AA
Amis
Freeman Hospital, High Heaton, Newcastle upon Tyne, NE7 7DN, United Kingdom.
David J
DJ
Deehan
D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D008875:Middle Aged
biomechanics; constraint; knee replacement; laxity; navigation