2015 ISAKOS Biennial Congress Paper #0

Syndesmotic Malreduction Assessment Using Three-Dimensional Distance Mapping: A Cadaveric Weight Bearing CT Study

Cesar De Cesar Netto, MD, PhD, Iowa City, Iowa UNITED STATES
Nacime Salomao Barbachan Mansur, MD, PhD, Coralville, IA UNITED STATES
Grayson Mark Talaski, Bloomington, Illinois UNITED STATES
John Kwon, MD, Boston, Massachusetts UNITED STATES
Matthieu Lalevee, MD, Iowa City, IA UNITED STATES
Eli Schmidt, Iowa City UNITED STATES
Ki Chun Kim, MD, PhD, Seoul KOREA, REPUBLIC OF
Andrew Behrens UNITED STATES
Kepler Carvalho, MD UNITED STATES
Kevin Dibbern, PhD, Iowa City, IA UNITED STATES
Aly Fayed, MD, M.SC., Iowa City, IA UNITED STATES
University of Iowa , Iowa City, Iowa, UNITED STATES

FDA Status Not Applicable

Summary: Distance mapping WBCT algorithms could detect syndesmotic instability in a cadaveric model with a high accuracy. Malreduction and subsequent positioning change after flexibilization were identified by the system. 3D WBCT algorithms might be an ample instrument in diagnosing tibiofibular instabilities.

Abstract:

Introduction

Syndesmotic injury and subsequent malreduction can be devastating to the long-term health of the ankle joint. The objective of this cadaveric study was to develop a WBCT 3D distance mapping algorithm that would allow for detection of syndesmotic instability, different types of syndesmotic malreduction, as well as possible correction of malpositioning with flexible fixation. We hypothesized that this algorithm could detect syndesmotic instability, enable assessment of induced syndesmotic malreduction and gauge correction of malpositioning provided by flexible syndesmotic fixation.

Methods

Four WBCT scans were obtained for each of 22 matched pairs (44 legs) of through knee cadaveric specimens in a radiolucent frame under native normal, syndesmotic destabilization, rigid malreduction, and flexibilization conditions. A conventional limited lateral approach was used to destabilize the joint ahead of 4 controlled malreduction conditions: 5mm anterior displacement, 5mm posterior displacement, 15° of internal rotation, and over-compressed (140N). Fixation was performed with a single implant 20mm proximal to the ankle joint. Implant utilized allowed initial rigid screw-type fixation, followed by implant flexibilization similar to a suture-type fixation. Syndesmotic incisura and gutter distances were assessed using a 3D distance map algorithm.

Results

Significant increases in mean syndesmotic distance was observed over the first centimeter of the syndesmosis from control to injured conditions. The largest changes were observed posteriorly with an average increase of 19% and averaged 1mm. Anterior increases were less pronounced at 11.8% in the first centimeter from the joint and averaged 0.5mm. Qualitatively, these changes were visually apparent in comparison distance maps. The increased distances observed more proximally at 3cm, 5cm, and 10cm from the joint were less pronounced. ROC analysis of injured specimens and contralateral intact limbs for the first 1cm proximally to the ankle joint found that this method achieved a diagnostic accuracy for syndesmotic instability of 90.75% (sensitivity of 85% and a specificity of 95%), at a threshold of 0.53mm difference in mean distances. Comparatively, when the ROC analysis was conducted using a logistic regression of unpaired data of the entire specimen population, the diagnostic accuracy for syndesmotic instability was smaller (74.24%) and achieved a sensitivity of only 40% and a specificity of 92%. Paired syndesmotic area and volumetric analyses had diagnostic accuracies for syndesmotic instability of 82.5% and 74.3%, respectively.

Conclusion

Distance mapping WBCT algorithms could detect syndesmotic instability in a cadaveric model with a high accuracy. Moreover, malreduction and subsequent positioning change after flexibilization were identified by the system. The findings shown by this study might support the use of 3D WBCT algorithms in the clinical scenario as an ample instrument in diagnosing tibiofibular instabilities, malpositionings and its potential corrections. Further basic and clinical research is necessary to confirm this premise.

KEYWORDS: Syndesmosis; syndesmotic instability; Weight Bearing; Weightbearing CT; WBCT; Malreduction; Three-dimensional; Distance Mapping

LEVEL OF EVIDENCE: Level V, Cadaveric Study