Lateral trochlear inclination

Last revised by Dr Joachim Feger on 20 Nov 2021

Lateral trochlear inclination (LTI) is the inclination angle between the femoral trochlea and a posterior condylar tangential line 1.

The lateral trochlear inclination angle is used in the assessment of trochlear dysplasia, a dysplastic deformity of the distal femur, which is a known risk factor for patellofemoral instability 1-5. It has been primarily introduced for magnetic resonance imaging 1. A review of the quality assessment of measurements for trochlear dysplasia identified the lateral trochlear inclination as the most useful measurement 3.

Traditionally the inclination angle is measured between the bony contours of the lateral trochlear facet on the most superior/proximal axial slice containing trochlear cartilage and a posterior condylar tangential line at the same level 1.

Recently a modification has been proposed addressing possible problems with the transitional anatomy of the condyles at the level, where the original version of the lateral trochlear inclination was measured. The modification was found more reliable in that study 4,5.

The modified inclination angle is measured between the bony contours of the lateral trochlear facet and a posterior condylar tangential line at the level, where the femoral condyles are best definable 4,5, which is usually further below, about 2 cm above the joint line.

The cut-off angle for the original measurement  <11° indicates trochlear dysplasia, with a reported sensitivity and specificity of 93% and 87% respectively 1.

The modified version suggests a threshold at ≤8.9° with a reported sensitivity and specificity of 68% and 90% 5.

The lateral trochlear inclination angle was introduced by Carillon et al in 2000 1.

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Cases and figures

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  • Figure 2: reporting aid
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