Bony landmarks available for minimally invasive lateral ankle stabilization surgery: a cadaveric anatomical study

The purpose of this study was to determine the clinical utility of three bony tubercles: fibular obscure tubercle, talar obscure tubercle and tuberculum ligamenti calcaneofibularis, to serve as anatomical landmarks for defining the precise location of the origins and insertions of the anterior talofibular ligament (ATFL) and calcaneofibular ligament (CFL).

Twelve lower extremity cadaveric specimens were procured. The detectability of the tubercles was tested using palpation and fluoroscopy with subsequent confirmation after dissection. If the tubercles were present, then distances from the identified tubercles to the footprint centres and the intersection of the ATFL and CFL were measured to allow precise localization of the ATFL and CFL origin and intersection sites. Further, if the tubercles were not detectable, then an attempt to provide an alternative means of localizing ATFL and CFL origin and insertion sites was made by measuring distances between alternative landmarks and other important structures. All the measurements were performed by two researchers, and the results were averaged.

The fibular obscure tubercle existed and was detectable in all specimens. It was located 1.3 mm proximal to the articular tip of the fibula, 2.7 mm to the intersection of the ATFL and CFL, 3.7 mm distal to the ATFL and 4.9 mm proximal to the CFL origins. The talar obscure tubercle existed 58 % of specimens and was detectable in 57 %. The talar obscure tubercle was located 1.4 mm to the ATFL. The ATFL insertion point was located 60 % of the distance from the inferolateral corner to the anterolateral corner of the of talar body along the anterior border of the talar lateral articular facet. The tuberculum ligamenti calcaneofibularis existed in 33 % of specimens and was detectable in 8 %. The CFL inserted 17 mm on a perpendicular projected line distal from the subtalar joint.

The fibular obscure tubercle was clinically relevant and reliable bony landmark of the ATFL and CFL origin location. However, the talar obscure tubercle was less reliable and the tuberculum ligamenti calcaneofibularis was rarely available and as such alternative landmarks for the ATFL and CFL insertion location should be utilized. The present study describes the utility of clinically relevant bony landmarks that may assist in identifying the origins and insertions of the ATFL and CFL to facilitate minimally invasive ankle stabilization surgery.