Improved Methods for Measuring Achilles Tendon Moment Arm Prospectively Applied to Total Ankle Arthroplasty Patients

The plantarflexion moment arm of the Achilles tendon (ATma) is critical to healthy locomotion. However, there is no consensus on the best method for measuring ATma. The first study of this dissertation outlines a novel method for quantifying ATma during dynamic tasks, using motion capture to define a functional axis of ankle rotation and ultrasound imaging to locate the Achilles tendon in vivo. The second study compares two methods for computing the axis of ankle rotation – using either a fixed functional axis or instantaneous helical axes. In plantarflexion and neutral, the fixed axis was the most appropriate choice, and provided estimates of ATma commensurate with previously reported values. The second half of this dissertation applies this novel method to total ankle arthroplasty (TAA). Study 3 found that the reduction in pain observed following TAA was associated with increased walking velocity and performance on locomotor tasks. However, improvements in pain did not fully explain improvements in locomotor function, which led to Study 4, where we investigated whether TAA altered ATma. The results indicated that approximately 37% of the change in ATma following TAA was attributable to a change in talar positioning. Further work is needed to determine any muscle adaptations to TAA, and to investigate whether a relationship exists between changes in ATma and changes in locomotor function following TAA.

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Year

Entry

1980

Spoor CW, Veldpaus FE. Rigid body motion calculated from spatial co-ordinates of markers. J Biomech. 1980;13(4):391-393.

2002

Wu G, Siegler S, Allard P, Kirtley C, Leardini A, Rosenbaum D, Whittle M, D'Lima DD, Cristofolini L, Witte H, Schmid O, Stokes I. ISB recommendation on definitions of joint coordinate system of various joints for the reporting of human joint motion, I: ankle, hip, and spine. J Biomech. 2002;35(4):543-548.

1980

Winter DA. Overall principle of lower limb support during stance phase of gait. J Biomech. 1980;13(11):923-927.

1980

Fukubayashi T, Kurosawa H. The contact area and pressure distribution pattern of the knee: a study of normal and osteoarthrotic knee joints. Acta Orthop Scand. December 1980;51(5):871-879.

1957

Kellgren JH, Lawrence JS. Radiological assessment of osteo-arthrosis. Ann Rheum Dis. December 1957;16(4):494-502.