Landmarks of the normal adult human trochlea based on axial MRI measurements: a cross-sectional study

For deepening trochleoplasty, a procedure used worldwide to correct trochlear dysplasia, only few surgical steps are described precisely. Important surgical landmarks, such as optimal cartilaginous trochlear depth and percentages of the new lateral and medial facet, remain unanswered.

A cross-sectional study (January 2011-August 2012) was carried out in adult patients (16-35 years) without trochlear dysplasia, who underwent magnetic resonance imaging (MRI). The main outcome was trochlear depth. The secondary outcome was the lateral/medial facet ratio. Measurements were made on the first axial cut from proximal with complete cartilage coverage of the trochlea. Differences between men and women were assessed.

Fifty-three patients (70% men) were included. Mean age was 24.6 years (SD±5.5). Overall mean trochlear depth was found to be as 4.0 mm (95% CI 3.6-4.3). Values differed significantly by gender (p=0.0271) with a mean of 3.4 mm (95% CI 3.0-3.8) for women and a mean of 4.2 mm (95% CI 3.8-4.7) for men. The mean ratio between the lateral and medial facet was 1.71 (95% CI 1.62-1.80), the lateral facet contributing 62.6% (95% CI 61.3-63.8) and the medial facet contributing 37.4% (95% CI 36.2-38.7) to the total cartilage length. For the facet ratio, there was no statistically significant gender difference (n.s.).

This study provides data on important landmarks for deepening trochleoplasty based on average MRI measurements in the general population. The difference between the MRI measurement and actual cartilage surface measurement is likely to be minimal, but is yet to be evaluated. Further evaluation of these landmarks by prospectively performing deepening trochleoplasty will determine the value of the clinical implication.

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