Abstracts Posters SICOT-SOF meeting Gothenburg 2010 _2_

Poster
Topic: Arthroplasty - Knee
Abstract number: 26307
RELATIONSHIP BETWEEN MECHANICAL AXIS OF THE TIBIAL COMPONENT
OF KNEE REPLACEMENT WITH ANATOMICAL AXIS OF TIBIA
Atanu BHATTACHARJEE, Vipul MANDALIA, JD ELDRIDGE
Avon Orthopaedic Centre, Bristol (UNITED KINGDOM)
Aim: Study the relationship between the mechanical axis of the tibial component of
knee replacement prosthesis with the central anatomical axis of the tibia at the apex
of the component stem and ankle joint. Method: 32 standardised long leg
radiographs of patients with knee replacement are reviewed. Central mechanical axis
of the stem of the tibial component is derived by joining four separate central points
across the stem. Deviation of this axis from the anatomical centre of the tibia at the
level of the apex of the tibial stem is measured. Central mechanical axis of tibial
component stem is extended distally to measure its deviation from anatomical centre
of the ankle joint. Results: The mean distance between central mechanical axis of
tibial stem and anatomical centre of proximal tibia at the level of apex of the tibial
stem is 3.21mm. Mean distance between the central mechanical axis of the tibial
component stem extended distally with the anatomical centre of ankle joint is
13.29mm. Conclusion: The central mechanical axis of the tibial stem does not always
correspond to the anatomical centre of the proximal tibia and ankle joint. Such
deviations of mechanical axis can lead to early polyethylene wear and instability.
Clinical evaluation with follow up is recommended with a larger group of patients to
investigate the bearing of this relationship for survival of prosthesis and revision of
knee replacements. A long leg radiograph should be done routinely after knee
replacement to demonstrate the relationship during early follow up.
152