Abstract
Introduction
Trochlear dysplasia (TD) is still poorly recognised, generally considered uncommon and to present purely as persistent patella dislocation.
Diagnosis
87 patients diagnosed as having TD by a true lateral X-ray, MRI scan or at surgery were sent a questionnaire about their initial symptoms. 60% had suffered adolescent anterior knee pain. Lack of trust, wobbling, stair problems, giving way and catching were also common symptoms. Only 66% had ever suffered a dislocation, their troubles had started at 12 years of age. Most had undergone unsuccessful realignment procedures and many had developed premature lateral patello-femoral arthritis.
Natural History
13 cases presented with late stage disease, in which the extensor mechanism is chronically dislocated and the PFJ arthritic. These were treated by isolated PFR.
In a further 5 cases end stage disease had developed. In these the chronically dislocated extensor mechanism had lead to an associate valgus knee with lateral compartment arthritis. These were treated by a TKR.
Results
16 of the 18 cases had a satisfactory result, though in two this followed secondary surgery to stabilise the extensor mechanism. Some flexion was lost but the average ROM post operatively was 110°. Two end stage cases, treated early in the series, had a persistent problem with valgus instability. Since this problem tends to occur with end stage disease subsequent similar cases were treated with a rotatating hinge, with much improved results.
Conclusion
TD can present in a variety of ways. If untreated the condition can lead to symptomatic PFOA, often with complete loss of cartilage in the lateral patello femoral joint before the age of 50. In severe cases chronic extensor mechanism dislocation can result and ultimately lateral compartment arthritis may follow.
