The non-invasive measurement of knee kinematics in normal, osteoarthritic and prosthetic knees

Clarke, Jon V. and Riches, Phil (2012) The non-invasive measurement of knee kinematics in normal, osteoarthritic and prosthetic knees. PhD thesis, University Of Strathclyde.

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Total knee arthroplasty (TKA) is the most widely performed intervention for end-stage osteoarthritis but in spite of limitations in surgical techniques, alignment measurements and clinical outcomes, the expectations of an active, aging population continue to increase. The aim of this thesis was to develop and validate a non-invasive kinematic assessment tool to improve the assessment of knee alignment and ligament laxity. An intra-operative infrared tracking system was adapted for non-invasive use through the development of external mountings that enabled alignment measurements to be made supine, standing and following manual collateral stress. Coronal and sagittal plane mechanical femorotibial (MFT) angle measurement was validated to a precision of ±1° by comparison to a custom made leg model, a flexible electrogoniometer and through repeatability measurements on 30 asymptomatic volunteers. Assessment of coronal laxity was quantified and standardised by controlling lever arm, applied manual load and knee flexion angle. Thirty one patients with end-stage OA were assessed before, during and six weeks following TKA and comparisons were made between invasive and non-invasive MFT angles and between supine and standing conditions. For osteoarthritic knees, varus and valgus angular displacements were greater intra-operatively in comparison to pre-operative non-invasive measurements, whereas invasive and non-invasive stress angles for prosthetic knees showed less variation. From supine to bi-pedal stance, MFT angles most frequently changed to relative varus and extension for all knee types suggesting that soft tissue restraints may be more important than rigid bony or prosthetic architecture for controlling this weight-bearing alignment change. The development of a non-invasive IR system enabled knee alignment to be quantified as a dynamic parameter in comparison to current static assessment techniques such as radiographs. The generation of subject-specific kinematic profiles could help with the surgical planning and post-operative follow-up of patients undergoing alignment dependent procedures such as TKA.