Background: Because there is limited information concerning the cruciate ligaments in proximal femoral focal deficiency, knee arthroscopy was used to identify the changes of cruciate ligaments and their relation to the different types of this deficiency.
Methods: Knee arthroscopy was performed in 21 consecutive patients with deficiency types III, IV, VII-IX using the Pappas classification. A new classification of the knee was created. It contains types I, II, III according to the findings of the anterior cruciate ligament (ACL) (type I: normal, type II: hypoplasia, type III: aplasia) and 3 subtypes A, B, C according to the findings of the posterior cruciate ligament (PCL) (type A: normal, type B: hypoplasia, type C: aplasia), respectively. Instrumented and radiologic drawer testing was provided additionally in 2010.
Results: The changes of the cruciate ligaments were found in all but 1 patient. Type I was found in only 2 patients. In 1, both cruciate ligaments were intact (type IA). In the other patient, the ACL was intact, but the PCL was absent (type IC). Hypoplastic ACLs (type II) were found in 4 patients, namely in 3 patients with normal PCLs (type IIA), whereas in 1 patient the PCL was absent (type IIC). In the majority of patients, the ACLs completely failed (type III, 15 patients). Absence of both cruciate ligaments was found in 8 patients (type IIIC). PCLs were intact in 4 patients (IIIA) or were hypoplastic in 3 patients (IIIB), respectively. Instrumental drawer testing was not reliable in patients of our group. Radiologic testing showed a posterior shift of the tibia in the majority of patients on the affected side. Anterior and posterior drawer tests were increased in a majority of patients, but did not directly correlate to the presence/absence of cruciate ligaments.
Conclusions: Variable changes of the cruciate ligaments were found in all but 1 patient with proximal femoral focal deficiency. These changes were not related to the type of Pappas classification. Despite the lower clinical relevance of the changes in majority of patients, imaging of cruciate ligaments is recommend before lengthening of the extremity to avoid dislocation of the knee.
Level of evidence: I - Testing of previously developed diagnostic criteria in series of consecutive patients.