TY - JOUR
T1 - The quadriceps angle
T2 - reliability and accuracy in a fox (Vulpes vulpes) pelvic limb model
AU - Miles, James Edward
AU - Frederiksen, Jane V.
AU - Jensen, Bente Rona
AU - Kirpensteijn, Jolle
AU - Svalastoga, Eiliv Lars
AU - Eriksen, Thomas
PY - 2012/4
Y1 - 2012/4
N2 - 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 (Vulpes 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 (Q1: patellar center, Q2: 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 (FMEDIAL) was calculated. Results: The HD position yielded significantly (P < .001) more medial Q angles than the WL position. No significant difference was observed between Q1 and Q2, but Bland-Altman plots indicated they were not equivalent. Intra- and interobserver agreement was substantial. Q2 errors were inherently greater than Q1: the mid-point and tibial tuberosity are the most important sources of Q angle variability. Increasing Q angles significantly increased the exerted FMEDIAL (P < .0001, gradient 1.7%). Conclusions: Measurements are reliable, but Q2 is more prone to error than Q1, and the 2 measurement techniques are not interchangeable. Positional errors must be kept below 1.3 mm (Q1) or 0.8 mm (Q2).
AB - 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 (Vulpes 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 (Q1: patellar center, Q2: 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 (FMEDIAL) was calculated. Results: The HD position yielded significantly (P < .001) more medial Q angles than the WL position. No significant difference was observed between Q1 and Q2, but Bland-Altman plots indicated they were not equivalent. Intra- and interobserver agreement was substantial. Q2 errors were inherently greater than Q1: the mid-point and tibial tuberosity are the most important sources of Q angle variability. Increasing Q angles significantly increased the exerted FMEDIAL (P < .0001, gradient 1.7%). Conclusions: Measurements are reliable, but Q2 is more prone to error than Q1, and the 2 measurement techniques are not interchangeable. Positional errors must be kept below 1.3 mm (Q1) or 0.8 mm (Q2).
U2 - 10.1111/j.1532-950x.2011.00936.x
DO - 10.1111/j.1532-950x.2011.00936.x
M3 - Journal article
SN - 0161-3499
VL - 41
SP - 422
EP - 429
JO - Veterinary Surgery
JF - Veterinary Surgery
IS - 3
ER -