Effect of Limb Position on Measurements of the Quadriceps Muscle Length/Femoral Length Ratio in Normal Beagle Dogs

Abstract

Objectives Dogs with patella alta reportedly have a shorter extensor mechanism than normal dogs. The present study aimed to measure the length of the extensor mechanism and to assess the effect of limb position on the quadriceps muscle length (QML)/femoral bone length (FL) ratio. Study Design Three-dimensional computed tomography images were taken of 12 Beagle dogs. Each dog underwent computed tomographic imaging 24 times with different limb positions. The QML/FL was measured on each image, along with the hip flexion–extension, hip abduction–adduction and stifle flexion–extension angles. Multiple regression analysis was used to determine the effect of these angles on the QML/FL. Results The QML/FL was increased with the hip extended (standardized partial regression coefficient 0.855 with linear plotting, 0.829 with log plotting) and with the stifle flexed (standardized partial regression coefficient 0.814 with linear plotting, 0.800 with log plotting). The partial regression coefficient of the hip abduction–adduction angle was small, indicating a small impact on the QML/FL. The 95% confidence range of the QML/FL with the hip extended and stifle flexed was 0.87 to 1.00 (mean ± standard deviation: 0.93 ± 0.03). Conclusion The QML/FL was more influenced by joint angles when the hip was flexed or the stifle was extended. Hence, these positions should be avoided when evaluating the QML/FL so that the QML is less altered by slight positioning disparities.

Examination of the proximodistal patellar position in small dogs in relation to anatomical features of the distal femur and medial patellar luxation

“…Thus, the ratio of the patellar ligament length to patellar length (PLL/PL) based on the Insall-Salvati index in humans was introduced as an index that is minimally affected by the stifle angle [6,[9][10][11]. Although some studies have introduced other indices to evaluate the proximodistal patellar position [2,12,13], these indices have not been used in clinical cases as often as the PLL/PL. Many canine studies have focused on the PLL/PL to discuss the proximodistal alignment between the patella and the femoral trochlea [1][2][3][4][5][6][7][8].…”

Evaluation of the quadriceps muscle length to femoral length ratio in small breed dogs with medial patellar luxation

“…Based on a previous study, 28 we defined QML as the distance from the lateral area of the rectus femoris muscle on the iliac crest to the proximal patella and FL as the distance from the proximal greater trochanter of the femur to the long extensor tendon fossa of the lateral femoral condyle. After QML and FL were measured, QML/FL was calculated by dividing QML by FL (Figure 1).…”

“…After QML and FL were measured, QML/FL was calculated by dividing QML by FL (Figure 1). An abnormal QML/FL was defined as <0.87, which was the lower limit of the reference range established in beagle dogs 28 …”

“…Based on a previously reported method, 28 we defined PLL as the length from the most distal point of the patella to the patellar ligament insertion point on the tibial tuberosity, and PL as the length from the most proximal to the most distal points of the patella. PLL/PL was calculated by dividing PLL by PL (Figure 3).…”

“…The quadriceps muscle length to femoral length ratio (QML/FL) is an indicator that has been reported in beagle dogs with normal stifle joints 28 . It is obtained using computed tomography (CT) images and reflects the QML in three‐dimensional (3D) space 28 .…”