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

Y1 - 2012

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 (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 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 F(MEDIAL) (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 (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 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 F(MEDIAL) (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

VL - 41

SP - 422

EP - 429

JO - Veterinary Surgery

JF - Veterinary Surgery

SN - 0161-3499

IS - 3

ER -