Dysplasia of the cruciate ligaments: radiographic assessment and classification.

BACKGROUND:
A common pathologic finding in the knee associated with congenital longitudinal deformity is aplasia of one or both cruciate ligaments. We performed a radiographic analysis to assess the changes in the femoral intercondylar notch and the tibial eminence in relation to the status of the cruciate ligaments.

METHODS:
Thirty-four knees in thirty-one patients with longitudinal congenital deficiency of the lower limb were evaluated. The cruciate ligaments and the associated abnormalities of the distal aspect of the femur and the proximal aspect of the tibia were evaluated with use of magnetic resonance imaging and a tunnel view radiograph.

RESULTS:
We differentiated three main types of dysplasia of the cruciate ligaments with typical associated changes. In type I, partial closure of the femoral intercondylar notch and hypoplasia of the tibial eminence are observed and the anterior cruciate ligament is hypoplastic or aplastic. In type II, these findings are accentuated and there is additional hypoplasia of the posterior cruciate ligament. In type III, the femoral intercondylar notch and the tibial eminence are completely absent and there is aplasia of both cruciate ligaments.

CONCLUSIONS:
We delineated three types of congenital deficiency of the cruciate ligaments and found corresponding morphologic changes of the femoral notch and the tibial eminence, which can be observed on tunnel view radiographs. Thus, the diagnosis and differentiation between aplasia of one or both cruciate ligaments and between congenital and trauma-induced absence of the cruciate ligaments may be made by interpreting plain radiographs.