Assessment of coronal mechanical alignment with applied varus and valgus force through the range of flexion using non-invasive navigation

  • Fraser John Henderson

Student thesis: Master's Thesis


Osteoarthritis of the knee is a highly prevalent disease, with total knee arthroplasty (TKA) a proven means of alleviating symptoms. In image-free navigation, infra-red markers are attached to bony landmarks to provide kinematic data during the TKA procedure, with the aim of improving the precision of the implant placement. In non-invasive navigation, infra-red markers are attached to the skin surface; recent evidence suggests that this can give reliable measurements of lower limb mechanical alignment. The aim of this thesis was to evaluate the use of a non-invasive navigation system in the assessment of mechanical alignment with applied coronal force through the range of flexion. A previously validated non-invasive system (Physiopilot) was tested on 23 volunteers with healthy knees. 2 users performed 2 registrations of the software workflow on each participant's right and left knees. A force was manually applied to the end-point of varus and valgus knee laxity and the measured change in mechanical alignment was recorded. Force was applied with the knee positioned in increments of flexion from 0˚-90˚. In keeping with previous studies, satisfactory values of CR (Coefficient of Repeatability) of 1.55 and 1.33 were found for intra-observer repeatability in measurement of supine Mechanical Femoro-tibial Angle (MFTA) in extension, with a good inter-observer correlation of ICC (intraclass Correlation Coefficient) 0.72. However, when flexion was introduced, intra-observer and inter-observer reliability fell outwith acceptable limits. The trial therefore did not support the Physiopilot system as a measure of MFTA when flexion is introduced. It was felt that learning-curve, soft tissue artefacts and lack of force standardisation equipment may have accounted for significant levels of error, with further studies required to address these issues.
Date of Award3 Aug 2016
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SupervisorPhil Riches (Supervisor) & Philip Rowe (Supervisor)

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