(482.6) Radiography Suggests a Fibrous Tubular Sleeve Distal to a Cartilaginous Anlage in a Limb with ‘Absent Fibular’ Represents a Traction

Poster Board Number: C121
Introduction: AAA has separate poster presentation times for odd and even posters.
Odd poster #s – 10:15 am – 11:15 am
Even poster #s – 11:15 am – 12:15 pm

Maria Krisch (SUNY Upstate Medical University), Mark Levinsohn (SUNY Upstate Medical University, Crouse Irving Memorial Hospital), David Hootnick (SUNY Upstate Medical University), Kent Ogden (SUNY Upstate Medical University), Philip Katzman (University of Rochester Medical Center)

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 amp; 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.