Summary
Objectives: Firstly, to investigate the effect that using different landmarks has on the measured
stifle angle. Secondly, to determine whether any differences in measured stifle angle
would lead to variations in the required extent of tibial tuberosity advancement (TTA).
Methods: Three greyhound stifles were positioned in a total of 66 different angles. Radiographic
exposures of each stifle angle were made. For each radiograph i) the stifle angle
was measured using each of three sets of landmarks and ii) the extent of TTA required
to obtain a patella tendon angle of 90° was measured. Each radiograph was plotted
graphically according to the stifle angle and the extent of TTA required. Linear regression
analysis was used to calculate the TTA required for a stifle angle of 135° measured
using each of the three landmark sets.
Results: On average, the stifle angle determined by the Long Axes method differed by 18° from
the stifle angle determined with the Kinematic method. The stifle angle determined
using the Eminence method differed from that determined using the Kinematic method
by three degrees. The use of the Long Axes of the tibia and femur as landmarks to
determine a stifle angle resulted in 5 mm and 4 mm over-advancement of the tibial
tuberosity compared to the use of Kinematic or Eminence landmark methods respectively.
Clinical significance: The method used to measure the stifle joint angle can influence the value of the
required TTA advancement. This is an additional variable that should be considered
during TTA planning and when comparing in vivo and in vitro studies.
Keywords
Tuberosity - advancement - stifle - angle - landmark
