SLR - December 2023 - Sato
Title: Anatomical variations of the tibial nerve and their clinical correlationReference: Soetoko AS, Fatmawati D. Anatomical variations of the tibial nerve and their clinical correlation. Anat Cell Biol. 2023 Sep 11. doi: 10.5115/acb.23.065. Epub ahead of print. PMID: 37694293.
Level of evidence: V
Reviewed By: Shane Sato, DPM PGY-3
Residency Program: Cambridge Health Alliance, Cambridge, MA
Podiatric Relevance: To be a successful podiatric surgeon, one should become as familiar with the anatomy of the lower extremity as possible. This review article further potentiates this by detailing the anatomic variations of the cross sectional area of the tibial nerve and its terminal branching point.
Methods: The authors compiled research data from articles written in English found through a search of the PubMed and Google scholar databases. The keywords used were tibial nerve, posterior tibial nerve, cross-sectional area, tarsal tunnel syndrome, neuropathy, and diabetic polyneuropathy.
Results: The malleolar calcaneal axis (MCA), a line extending from the medial malleolus to the medial calcaneal tuberosity, has been used as a reference point to classify the branching points of the tibial nerve. Based on this line there are five types of branching points:
I) above the axis and within the tarsal tunnel
II) as high as the axis
III) distal end of the axis, within the tarsal tunnel
IV) proximal axis, outside the tarsal tunnel
V) distal axis, outside the tarsal tunnel
Most cadaveric studies found that branching occurs within the tarsal tunnel and at the proximal portion of the axis (type I). In regards to cross-sectional area (CSA), they found that this varied between ethnicities. The mean tibial nerve CSA was 6.36 to 15.25 mm². The CSA appears to increase with age and is also related to BMI and weight. CSA is also increased in patients with tarsal tunnel syndrome as well as those with diabetic peripheral neuropathy. CSA was found to be similar in both legs of the same patient.
Conclusions: The authors summarize the above findings in their conclusion. They do emphasize that the contralateral leg can be used as an internal control when establishing a diagnosis. The article offers valuable information to the foot and ankle surgeon helping them become a better diagnostician (i.e., comparing the CSA of the nerve from the affected side to the control (contralateral side) if there is suspicion for tarsal tunnel syndrome) and surgeon (i.e., knowing that variations of the terminal branching of the nerve exist and the approximate region they exist in, avoiding costly injury to the nerve).