E2152. Variety is the Spice of Life: Normal Musculoskeletal Variants of the Lower Extremity
  1. Andrew Sill; Mayo Clinic Arizona
  2. Min Kong; Mayo Clinic Arizona
  3. Jonathan Flug; Mayo Clinic Arizona
  4. Jeremiah Long; Mayo Clinic Arizona
Normal musculoskeletal variants are the spice of musculoskeletal imaging, particularly in the lower limbs. They are frequently encountered, typically incidental, and may have a confusing appearance on imaging, often simulating pathologic conditions despite their benignity. To further complicate matters, they may occasionally result in symptomatology or pathology. In many instances, these normal variants have specific imaging characteristics that allow for confident determination of the benign nature of these variants. Prompt and confident recognition of these variants will avoid confusion and allow for the accurate interpretation of musculoskeletal imaging.

Educational Goals / Teaching Points
The goals of our presentation are to provide a framework for categorizing anatomic variants; evaluate viewers' pre-existing knowledge of common, recognizable, and/or important lower extremity musculoskeletal variants via a quiz-style, case-based approach; and enhance viewers' comprehension and analysis of variants via examples and explanations of potential symptomatic and pathologic presentations.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Anatomic variants can be categorized as (1) variations in ossification, (2) variations in ligamentous or tendinous insertions, (3) variations in cartilaginous structures, and (4) variations in musculature. We will also define the common terminology that describes many “variants,” such as ossicle, partite, synostosis, accessory, and sesamoid. Then, in a quiz-style, case-based format, we will present the multimodal imaging appearance of a variety of clinically significant, frequently encountered, and/or easily misinterpreted lower extremity musculoskeletal variants, predominantly those of the hip, knee, and foot/ankle. Examples include the bipartite navicular, tarsal coalitions, os peroneum, bipartite patella, supra-acetabular fossa, dorsal defect of the patella, accessory soleus, and the os acetabuli, to name a few. With each case, we will describe methods of differentiating these entities from pathologic lesions, correlate these variants with potential symptomatology, and highlight potential pitfalls in interpretation.

Confident recognition of musculoskeletal variants is important for radiologists so that they might avoid misinterpretation of normal variants as pathology and thereby avoid potentially costly workup. Furthermore, a deeper understanding of the potential symptomatology or pathology that may be associated with normal variants is equally as important, since many variants can go on to become clinically significant. After reviewing this presentation, viewers will feel confident in their abilities to identify lower extremity musculoskeletal variants and understand their potential clinical implications.