Abstract
Objective Patellar luxation can be associated with abnormal proximodistal positioning of the
patella. The current gold standard index (Insall–Salvati) for referencing this position
is poorly suited to postoperative use, if the tibial tuberosity is moved surgically,
but has the advantage of changing minimally with altered joint angles. The aim of
this study was to identify an alternative index, which was simple to use, joint-angle
insensitive and suitable for postoperative use.
Study Design Candidate indices based on the angle between stifle joint landmarks were screened
across a wide range of joint angles for insensitivity to joint angle changes using
vulpine and canine stifle radiographs. Intraobserver and interobserver agreements
were assessed for a single candidate index using canine radiographs.
Results An angular index based on the caudal aspect of the femoral and tibial condyles and
the apex of the patella was largely insensitive to joint angle variation. Intra- and
interobserver agreements appeared suitable for clinical use, with low within-subject
standard deviations (<1.3°) and coefficients of variations (<2.2%), and high intraclass
correlation coefficients (>0.89).
Conclusion Patellar proximodistal position can be acceptably assessed at a variety of caudal
joint angles using the described angular index. Further work is required to define
reference intervals across a range of canine breeds.
Keywords
patella luxation - radiographs - dogs
