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Fig. 7B —Radiographic measurements for total ankle arthroplasty
(illustrated using STAR [Scandinavian Total Ankle Replacement, Waldemar Link]
device). Angular and linear values can be defined to evaluate changes in
component alignment and position that may signify component migration
[8–10].
Lateral view of STAR device depicts method of angular evaluation. Beta angle
(β) is formed by intersection of lines drawn parallel to flat plate of
tibial component and long axis of tibial shaft (normal = 90°). Gamma angle
(
) is formed by intersection of line drawn through long axis of talar
component with line drawn from posterior talar component through middle of
talar neck. Gamma angle in postoperative setting has been shown to range from
11.1° to –33.4°, with average measurement of 18.8°
[10].