Trochleoplasty in major trochlear dysplasia: current concepts

Abstract

Trochleoplasty is the theoretical solution to persistent symptoms (pain and/or instability) related to trochlear dysplasia where there is not only a trochlear flatness but also a trochlear prominence. The threshold of prominence indicating surgical intervention has as yet not been determined. A bump of 5 mm is generally accepted as the inferior limit. Given the interventional nature of this demanding procedure, it should be proposed in selected cases after considerable discussion with the patient. Trochleoplasty is indicated as a primary procedure for major trochlear dysplasia with a prominence > 5 mm. Stabilization is obtained in most of the cases with the risk of residual mild anterior knee pain. It is also indicated as a salvage procedure when a previous surgery failed. Despite the reputation of the procedure, the published results are encouraging in terms of prevention of re-dislocation, satisfaction index, and radiological outcomes. Post-operative stiffness is the main complication, which may require manipulation under anaesthesia or arthroscopic arthrolysis. There are few other complications reported and to date secondary necrosis of the trochlea has not been reported. Technically speaking, the deepening trochleoplasty is a difficult procedure without reliable landmarks. We propose a recession wedge trochleoplasty which is an easier procedure. It is never undertaken as an isolated procedure, but always in conjunction with other realignment procedures of the extensor apparatus according to the "a la carte" surgery concept.

Figure 1

Elevation of the lateral facet, according to the Albee technique.

Figure 2

Deepening throchleoplasty. The trochlear groove has been restored but note the incongruency between the flat patella and the deepened trochlea.

Figure 3

Recession trochleoplasty. There is a reduction of the prominence but the flat trochlea remains (crossing sign).

Figure 4

Different types of trochlear dysplasia a: crossing sign without prominence b: crossing sign and marked prominence demonstrating a major dysplasia.

Figure 5

lateral view in complete extension and quadriceps contraction. It allows to assess patellar tilt, according to the shape of the patella.

Figure 6

CT scan. It directly evaluates the trochlear prominence. The orientation of the trochlear plane and the trochlear lateralization explain patellar tilt and subluxation.

Figure 7

The four steps of deepening trochleoplasty.

Figure 8

Pre and Post-operative bump height measurement technique. A and B: Drawings showing the Dejour and Walch method for calculating the bump height. Point "D" is the junction between the posterior cortex and articular cartilage. Bump height is measured between points "B" and "C". C: Pre operative lateral radiograph: the boss height is positive. D: Post operative lateral radiograph: the boss height is now negative.

Figure 9

The recession wedge trochleoplasty surgical technique. A and B: The base of the wedge which is removed should be the same in millimeter that the value of the trochlear bump in order to allow the trochlea to settle into a deeper position, without modifying the trochlear groove. C and D: The correction is obtained after removal of the proximally based wedge by progressively applying a pressure on the trochlea. Fixation is carried out with two 3.5 mm cancellous screws, positionned just laterally to the cartilage surface.

Figure 10

Post operative X rays after Recession wedge trochleoplasty. A: lateral view showing the reduction of the trochlear porminence. B 30° patello femoral view showing the extracartilaginous position of the screws.