Review Question - QID 218919

The radiograph shows right-sided fibular deficiency with an abnormally short fibula (Achterman and Kalamchi type 1B). Anterior cruciate ligament hypoplasia has been positively correlated with hypoplasia of the lateral femoral condyle, lateral tibial spine dysplasia, absence of the fibula, and absence of lateral foot rays.

Congenital fibular deficiency (CFD) is the most commonly reported congenital long bone deficiency. While its specific etiology remains unknown, it is associated with ball-and-socket ankle joint, lateral femoral condyle hypoplasia, and a moderately shortened femur. This spectrum of abnormalities also can include hypoplasia of the lateral tibial spine, absent lateral rays, tarsal coalition, developmental dysplasia of the hip, and cruciate ligament deficiency. Treatment of fibular deficiency is typically either amputation or complex limb lengthening, depending on the severity of the deformity and the functionality of the foot and ankle. The Achterman and Kalamchi classification is based on the amount of fibula present, and treatment is based on limb length discrepancy (LLD), skeletal maturity, and the need to achieve a stable, plantigrade foot.

Manner et al. devised a classification system for cruciate ligament hypoplasia based on notch view radiographs in patients with congenital fibula deficiency. Type 1 (hypoplastic ACL, normal PCL) correlated with a normal medial tibial spine and hypoplastic lateral tibial spine. Type 2 (absent ACL, hypoplastic PCL) correlated with a hypoplastic medial tibial spine and an absent lateral tibial spine. Type 3 (absent ACL and PCL) correlated with absent medial and lateral tibial spines. Therefore, diagnosing and classifying the degree of cruciate ligament hypoplasia may be made by interpreting plain radiographs.

Walker et al. describe several radiographic findings that positively correlate with the degree of tibial spine hypoplasia. Using tibial spine morphology as a surrogate for ACL hypoplasia, they found that the degree of lateral femoral condyle hypoplasia was directly correlated to the severity of lateral tibial spine dysplasia, as well as the severity of fibula and foot ray deficiency. Clinically, these correlations can be used to predict the severity of related orthopaedic manifestations that may require future treatment.

Figure A is a standing radiograph demonstrating right sided congenital fibular deficiency in a skeletally immature individual. Illustration A describes the Achterman and Kalamchi classification. Type 1A consists of the proximal fibular epiphysis located distal to the proximal tibial physis. Type 1B consists of an abnormally shortened fibula, about 30-50% of its expected length. Type 2 consists of a completely absent or vestigial portion of the fibula.

Incorrect answers:
Answer 1: Medial femoral condyle hypoplasia is not associated with ACL dysplasia.
Answer 2: Anterolateral tibial bowing is associated with congenital pseudarthrosis of the tibia and neurofibromatosis.
Answer 4: PCL dysplasia may accompany ACL dysplasia but has not been published as having a positive correlation.
Answer 5: Decreased tibial slope is not associated with ACL dysplasia.