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The Quadriceps Angle: Reliability and Accuracy in a Fox ( V ulpes vulpes ) Pelvic Limb Model
Author(s) -
Miles James E.,
Frederiksen Jane V.,
Jensen Bente,
Kirpensteijn Jolle,
Svalastoga Eiliv L.,
Eriksen Thomas
Publication year - 2012
Publication title -
veterinary surgery
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 79
eISSN - 1532-950X
pISSN - 0161-3499
DOI - 10.1111/j.1532-950x.2011.00936.x
Subject(s) - medicine , cadaveric spasm , anatomy , radiography , inclinometer , hip dysplasia , orthodontics , nuclear medicine , vulpes , knee flexion , tibial tuberosity , patella , geodesy , surgery , geology , paleontology , predation
Objectives To evaluate the effect of measurement technique and limb positioning on quadriceps ( Q ) angle measurement, intra‐ and interobserver reliability, potential sources of error, and the effect of Q angle variation. Study Design Cadaveric radiographic study and computer modeling. Animals Pelvic limbs from red foxes ( V ulpes vulpes ). Methods Q angles were measured on hip dysplasia ( HD ) and whole limb ( WL ) view radiographs of each limb between the acetabular rim, mid‐point ( Q 1: patellar center, Q 2: femoral trochlea), and tibial tuberosity. Errors of 0.5–2.0 mm at measurement landmarks alone and in combination were modeled to identify the effect on Q angle. The effect of measured Q angles on the medial force exerted on the patella (F MEDIAL ) was calculated. Results The HD position yielded significantly ( P < .001) more medial Q angles than the WL position. No significant difference was observed between Q 1 and Q 2, but B land– A ltman plots indicated they were not equivalent. Intra‐ and interobserver agreement was substantial. Q 2 errors were inherently greater than Q 1: the mid‐point and tibial tuberosity are the most important sources of Q angle variability. Increasing Q angles significantly increased the exerted F MEDIAL ( P < .0001, gradient 1.7%). Conclusions Measurements are reliable, but Q 2 is more prone to error than Q 1, and the 2 measurement techniques are not interchangeable. Positional errors must be kept below 1.3 mm ( Q 1) or 0.8 mm ( Q 2).