Lateral epiphyseal narrowing with valgus deformities of the knee and ankle are cardinal radiographic features of Congenitally Shortened Limbs (CSL) exhibiting Congenital Fibular Deficiency (CFD). Radiographs of typical CFD limbs reveal valgus deformities and lateral epiphyseal reductions at both the knee and ankle. Arteriography of CSL reveals not only absence of adult vessels, but preservation of primitive vessels. Specifically, the superior and inferior lateral genicular arteries that habitually serve the lateral femoral condyle (LFC) and the lateral aspect of the proximal tibial epiphysis are absent in CSL. Similarly, the usual arteries supplying the distal tibial epiphysis are absent, except for a singular periosteal vessel, which independently serves the anteromedial portion. Active transitioning of the single primitive Axial Artery (AA) to the usual adult pattern of the lower limb accompanies periods of rapid growth and ossification its anlagen. Dysgenesis of the lateral arteries supplying the secondary ossification centers leads to asymmetric growth of the developing epiphyses, caused by relative medial overgrowth. Since vascular dysgenesis manifests at sites of failed embryonic transition of the proximal Femur, fibula and midline Metatarsals (FfM) in CSL, it is herein hypothesized that vascular dysgenesis also underlies the impaired growth of the reduced epiphyses as seen in CSL.

Background Dissections of congenitally shortened limbs displaying congenital fibular deficiency have revealed pathologic cartilaginous bodies and fragments along the course of the “absent” fibula consistent with remnants of a fibular anlage (Wagstaffe, 1875; Freund, 1936; Harmon & Fahey, 1937; Thompson et al., 1957). Bands distal to the anlagen have traditionally been reported as fibular calcaneal collateral ligaments. Objective This project reinterprets the composition of the posterolateral ankle band frequently found in patients with congenital shortened limb (CSL) with fibular deficiency based on advanced radiographic criteria. Patient and Method Bilateral thin slice computed tomography (TSCT) imaging was performed on the distal lower extremities of a 43‐year‐old female patient with unilateral congenital shortened limb with fibular “absence” for operative planning. The images were imported into virtual modeling system 3D Slicer and various tissues in the region were measured and compared for attenuation using the Hounsfield unit (HU) scale. Results The radiological study of the posterolateral ankle band in the presence of a limb with a diminutive fibular anlage exhibiting a normal medullary density revealed a tubular structure sharing attenuation readings with nearby adipose tissue at its core and fibrous tissue at its periphery. Conclusion The tubular structure of the posterolateral ankle band with an adipose core, surrounded by fibrous tissue in the presence of a retained primitive fibular anlage, supports the assertion that fibular absence in this congenitally shorted limb is a radiographic misnomer, since a dystrophic anlage persists in its place. Additionally, previously identified fibulocalcaneal structures (or bands) may actually represent a stretched periosteal sleeve caused by traction exerted on the anlage by the paired lower tibia. These findings support the hypothesis that this “ligament” structure is the distalmost tubular remnant of an otherwise normally formed cartilaginous scaffold of the fibular anlage. The anlage has failed to ossify to form a normal fibular long bone structure, due to embryonic arterial dysgenesis and failed vascular invasion during the sixth‐seventh weeks of embryonic development.