Kansas City University Kansas City, Missouri, United States
Abstract Body : Introduction and Objective: The tensor fascia suralis muscle (TFS) is a clinically relevant muscle variation that describes the insertion of a posterior thigh muscle inserting into the crural fascia of the leg. Clinical relevance of the TFS variation includes a palpable mass within the popliteal fossa and neuromuscular compression of regional nerves. This study reports the findings of bilateral TFS and a unilateral accessory muscle belly of the biceps femoris muscle in a 72-year-old female. In this study, common peroneal neuropathy was most likely as the common peroneal nerve was seen wrapping around the accessory biceps femoris muscle along its course.
Materials and Methods: These findings were first identified during educational dissection of the lower extremity by first-year medical students. The accessory muscle belly and bilateral TFS were further dissected to identify their origin and insertion.
Results: The left TFS (length, 22.83 ± 0.05 cm; width, 6.24 ± 0.14 mm) originated from the biceps femoris long head muscle (BFLH), 18.9 cm inferior from the BFLH origin on the ischial tuberosity, and inserted onto the crural fascia overlying the lateral gastrocnemius muscle 26.1 cm from the superior tip of the calcaneus. The right TFS (length, 114.89 ± 0.62 mm; width, 9.82 ± 0.11 mm) originated from the BFLH, 19.2 cm from its origin on the ischial tuberosity, and inserted onto the crural fascia overlying the medial gastrocnemius muscle 31.9 cm from the superior tip of the calcaneus. The length of the crural fascia insertion was 76.26 ± 3.00 mm and 127.69 ± 1.41 mm in the left and right limbs, respectively. An accessory biceps femoris muscle belly was identified on the left limb only and originated from the inferior most aspect of the greater trochanter. It inserted on the distal end of the biceps femoris long head, 20.0 cm from the BFLH origin and 147.62 mm from the BFLH insertion. The common peroneal nerve passed under the accessory muscle belly 20.3 cm inferior to the lower border of the piriformis.
Conclusion: This data characterizes the novel finding of bilateral TFS muscles with a unilateral accessory biceps femoris muscle belly.
Significance/Implication: To the best of our knowledge, this unique presentation has not been previously explained by cadaveric or imaging studies.
