Basic Study
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World J Orthop. Nov 18, 2022; 13(11): 969-977
Published online Nov 18, 2022. doi: 10.5312/wjo.v13.i11.969
Role of the posterior deep deltoid ligament in ankle fracture stability: A biomechanical cadaver study
Daniel James McCormack, Matthew Solan, Sheweidin Aziz, Radwane Faroug, Sayyied Kirmani, Georgina Wright, Jitendra Mangwani
Daniel James McCormack, Sheweidin Aziz, Sayyied Kirmani, Georgina Wright, Jitendra Mangwani, Department of Trauma and Orthopaedics, University Hospitals of Leicester, Leicester LE1 5WW, United Kingdom
Matthew Solan, Department of Trauma and Orthopaedic Surgery, Royal Surrey City Hospital NHS Trust, University of Surrey, Guilford GU2 7XX, United Kingdom
Radwane Faroug, Department of Trauma and Orthopaedics, Stoke Mandeville Hospital, Aylesbury HP21 8AL, Buckinghampshire, United Kingdom
Author contributions: McCormack DJ, Aziz S, Kirmani S, Faroug R, Wright G, Mangwani J are responsible for performing the experiment; McCormack DJ, Aziz S, Kirmani S, Faroug R, Wright G, Mangwani J, and Solan M contributed to the manuscript preparation.
Institutional review board statement: Institutional approval for research involving human cadaveric tissue - Keele University, United Kingdom 2019.
Informed consent statement: Cadaveric specimens were used in accordance with the Human Tissue Act, no specific informed consent was required.
Conflict-of-interest statement: All the authors report no relevant conflicts of interest for this article.
Data sharing statement: No additional data.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Daniel James McCormack, MBChB, Surgeon, Department of Trauma and Orthopaedics, University Hospitals of Leicester, University Hospitals of Leicester Headquarters, Level 3, Balmoral Building, Leicester Royal Infirmary, Infirmary Square, Leicester LE1 5WW, United Kingdom. daniel.mccormack@gmail.com
Received: May 25, 2022
Peer-review started: May 25, 2022
First decision: August 1, 2022
Revised: September 1, 2022
Accepted: October 27, 2022
Article in press: October 27, 2022
Published online: November 18, 2022
Processing time: 174 Days and 23.4 Hours
Abstract
BACKGROUND

The deltoid ligament is a key component of ankle fracture stability. Clinical tests to assess deltoid ligament injury have low specificity. In supination external-rotation (SER) type-IV ankle fractures, there is either a medial malleolus fracture or deltoid ligament injury. These injuries are often considered unstable, requiring surgical stabilisation. We look to identify the anatomical basis for this instability. This study investigates the anatomical basis for such instability by re-creating SER type ankle fractures in a standardised cadaveric study model, investigating the anatomical basis for such instability.

AIM

To investigate the anatomical basis for fracture instability in SER type ankle fractures.

METHODS

Four matched pairs of cadaveric limbs were tested for stability both when axially loaded and under external rotation stress. Four matched pairs of cadaveric limbs (8 specimens) were tested for stability when axially loaded to 750 N with a custom rig. Specimens were tested through increasing stages of SER injury in a stepwise fashion before restoring the lateral side with open reduction and internal fixation (ORIF). Clinical photographs and radiographs were recorded at each step. We defined instability in accordance with well accepted radiological parameters: > 4 mm medial clear space opening on a mortise-view radiograph or > 7 degrees of talar tilt.

RESULTS

All specimens with an intact posterior deep deltoid ligament were stable. Once the posterior deep deltoid ligament was sectioned there was instability in all specimens. Stabilisation of the lateral side prevented talar shift, but not talar tilt.

CONCLUSION

If the posterior deep deltoid ligament is intact then SER fractures can be managed without surgery. If the posterior deep deltoid is incompetent, ORIF and cautious rehabilitation is recommended because the talus can still tilt in the mortise.

Keywords: Trauma; Fracture stability; Biomechanics; Cadaveric study; Basic science

Core Tip: The deltoid ligament is a key component of ankle fracture stability. No fracture with an intact posterior deep deltoid ligament demonstrated instability on axial loading or rotational stress. This study suggests the instability can only occur in the presence of posterior deep deltoid ligament deficiency, supporting the non-operative treatment of many ankle fractures. If the posterior deep deltoid ligament is intact then supination external-rotation fractures can be managed without surgery. If the posterior deep deltoid is incompetent, open reduction and internal fixation and cautious rehabilitation is recommended because the talus can still tilt in the mortise.