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Can we define envelope of laxity during navigated knee arthroplasty?

Lookup NU author(s): Dr Alasdair Blain, Professor Stephen Rushton, Professor David Deehan

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Abstract

Functional outcomes after knee arthroplasty (TKA) remain poor. The ability to restore the soft tissue envelope intraoperatively may improve such outcomes. The aim of this study was to extend the scope of computer navigation as a tool to quantifying the envelope of laxity during subjective stress testing preoperatively and to quantify the effects of knee replacement and how it changes as a result of ligamentous failure.Loaded cadaveric legs were mounted on a purpose-built rig. Envelope of laxity was measured in 3 degrees of freedom using computer navigation. Knees were subjectively stressed in varus/valgus, internal/external rotation and anterior draw. This was performed preoperatively, during TKA and after sequential sectioning of ligaments. Real-time data were recorded at 0A degrees, 30A degrees, 60A degrees and 90A degrees of flexion. Mixed effect modelling was used to quantify the effects of intervention on degree of laxity.In all cases, there was an increase in laxity with increasing flexion or ligament sectioning. Operator and movement cycle had no effect. Insertion of a TKA showed increased stability within the joint, especially in internal/external rotation and anterior drawer. Once the PCL and popliteus were cut, the implant only maintained some rotatory stability; thereafter, the soft tissue envelope failed.This work has shown a novel way by which computer navigation can be used to analyse soft tissue behaviour during TKA beyond the coronal plane and throughout range of motion. Despite subjective stress testing, our results show reproducible patterns of soft tissue behaviour-in particular a wide range of mid-flexion excursion. It also quantifies the limits within which a cruciate-retaining TKR can maintain knee stability. This functionality may guide the surgeon in identifying and/or preventing soft tissue imbalances intra-operatively, improving functional results.

Publication metadata

Author(s): Ghosh KM, Blain AP, Longstaff L, Rushton S, Amis AA, Deehan DJ

Publication type: Article

Publication status: Published

Journal: Knee Surgery, Sports Traumatology, Arthroscopy

Year: 2014

Volume: 22

Issue: 8

Pages: 1736-1743

Print publication date: 01/08/2014

Online publication date: 06/07/2013

Acceptance date: 10/06/2013

ISSN (print): 0942-2056

ISSN (electronic): 1433-7347

Publisher: Springer

URL: http://dx.doi.org/10.1007/s00167-013-2574-0

DOI: 10.1007/s00167-013-2574-0

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