Trochlear dysplasia: imaging and treatment options

Abstract

Recurrent patellar dislocation is a disabling condition, which can lead to articular cartilage injuries, osteochondral fractures, recurrent instability, pain, decreased activity and patellofemoral osteoarthritis. Trochlear dysplasia represents an important component of patellar dislocation.Imaging provides an objective basis for the morphological abnormalities and thus allows determination of the surgical strategy according to the concept of 'à la carte' surgery.The main surgical techniques of trochleoplasty are the sulcus deepening trochleoplasty, the 'Bereiter' trochleoplasty and the recession trochleoplasty.At mid-term, all techniques have shown a postoperative improvement in clinical scores, with a low rate of recurrence of dislocation and a possible return to sport. But these techniques do not halt the progression of patellofemoral arthritis. Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.170058.

Keywords: Bereiter trochleoplasty; crossing sign; deepening trochleoplasty; patellar instability; patellofemoral osteoarthritis; recession trochleoplasty; supra-trochlear spur.

Fig. 1

Axial view and lateral view of a normal trochlea without dysplasia. The two most anterior lines (blue and orange pictures) corresponded to the contours of the condyles. The curve directly posterior to these lines corresponds to the trough of the trochlear groove (yellow star).

Fig. 2

Lateral view radiograph of a right knee showing a crossing sign and a small double contour in the context of trochlear dysplasia type C (D. Dejour’s classification).

Fig. 3

Lateral view radiograph showing the trochlear bump. The yellow line is a straight line tangential to the anterior femoral cortex. The floor of the trochlea (blue line) is anterior to this line, indicating a positive trochlear bump.

Fig. 4

The trochlear depth measurement is performed on a true lateral radiograph view. A tangent to the posterior femoral cortex (red line) and a perpendicular line at the most proximal part of the posterior condyles (blue line) are drawn. A (yellow) line subtended 15° from the perpendicular line is now used to measure the trochlea depth (AB length).

Fig. 5

D. Dejour’s classification for the trochlear dysplasia: type A with an isolated crossing sign, type B with a crossing sign and a supratrochlear spur (flat or convex trochlea), type C with a crossing sign and a double contour (asymmetry of trochlear facets with a hypoplastic medial condyle) and type D with a crossing sign, a supratrochlear spur and a double contour (asymmetry of trochlear facets plus vertical join and cliff pattern). CT scan (or MRI) slices and lateral radiological view are both necessary in this classification.