Sagittal Orientation and Variabilities of the Anatomical Insertional Footprint of the Achilles Tendon: A Cadaveric Study

Abstract

Category: Hindfoot; Sports Introduction/Purpose: New surgical techniques for Achilles tendon insertional pathology are evolving rapidly. Whether via open surgery, minimally invasive, or endoscopic approaches, more information about the Achilles' insertional footprint is needed to help surgeons with decision making. This study investigated the footprints of the Achilles insertion in sagittal orientation to delineate the anatomical landmarks, safe zones for bone resection3-down surgeries in treating insertional Achilles tendinopathies. Methods: Twenty fresh frozen cadavers were selected excluding insertional Achilles tendon pathology on lateral view x-rays. The calcanei were dissected maintaining the Achilles tendon insertion intact. Dimensions of the posterior tuberosity were recorded and marked to plan for three sagittal cuts (medial, middle, and lateral) (Fig 1 A). Using an oscillating saw (Fig 1 B.), the posterior tuberosity was cut into four pieces (Fig 1 C,E). A trapezoid shape (Fig 1 D) was reconstructed demonstrating relative location of the footprints of the Achilles insertion compared to the boundaries of the tuberosity on each piece (A, most superior point in the posterior tuberosity; B, most superior point in the Achilles insertion; C, most inferior point in the Achilles insertion; D, most inferior point in the posterior tuberosity). Data regarding footprints of the Achilles tendon insertion in the sagittal orientation was analyzed and compared within each trapezoid region and among different regions. Results: AB (calcaneal tuberosity tip to the upper limit of the Achilles insertion) was shortest at the medial cut (9.35mm) and longest at the lateral cut (12.15mm). However, the tendon thickness at the insertion (the distance from the proximal to the distal limits) represented by BC was shortest at the lateral cut (13.19mm) and longest at the middle cut (14.04mm). AD, the distance from the highest to the lowest point of the calcaneal tuberosity, was the longest at the middle cut (41.20mm). AB:BC ratio was highest at the lateral cut and lowest at the medial cut, indicating the safe amount of bone to be resected at the Achilles insertion. Tendon thickness relative to the whole calcaneal tuberosity (BC:CD) was highest at the medial wall (Table1). Conclusion: The sagittal orientation and variability of the Achilles tendon insertion is an under-studied topic in the literature. It needs to be addressed given recent trends towards minimally invasive procedures in treating insertional Achilles pathology. This study precisely delineated the footprint in each region of the insertion by creating a trapezoid pattern to compare the coordinates across these areas. This could lead to future three-dimensional reconstruction of the Achilles insertional footprint and patient- specific instrumentation software directed towards optimizing the management of Insertional Achilles pathology.