2015 ISAKOS Biennial Congress Paper #0

The Impact Of 3D Foot Alignment On Detection Of Distal Tibiofibular Syndesmotic Widening After Injury Using Comparative Contralateral Distance Mapping

Grayson Mark Talaski, Bloomington, Illinois UNITED STATES
Nacime Salomao Barbachan Mansur, MD, PhD, Coralville, IA UNITED STATES
Kepler Carvalho, MD UNITED STATES
Ki Chun Kim, MD, PhD, Seoul KOREA, REPUBLIC OF
Cesar de Cesar Netto, MD, Iowa City, Iowa UNITED STATES
Kevin Dibbern, PhD, Iowa City, IA UNITED STATES
Andrew Behrens UNITED STATES
University of Iowa, Iowa City, Iowa, UNITED STATES

FDA Status Not Applicable

Summary: Cadaveric study to determine the relationship between hind foot alignment, measured by foot-ankle offset, and the amount of distal tibiofibular syndesmotic widening.

Abstract:

Introduction

Previous studies identified a link between increased hindfoot valgus and distal tibiofibular syndesmosis (DTFS) widening in patients with flatfoot deformity using foot-ankle offset (FAO). However, it is not known what the impact of 3D foot alignment is on the DTFS in the presence of a known syndesmotic injury, particularly in varus. The objective of this cadaveric study was to determine the relationship between hindfoot alignment, measured by FAO, and DTFS widening in specimens with complete DTFS ligamentous injury, under simulated weightbearing. We hypothesized that DTFS widening would be significantly greater in specimens with increased hindfoot valgus.

Methods

Two WBCT scans of the foot and ankle were obtained for each of 17 matched pairs (34 legs) of through-knee cadaveric specimens in a radiolucent frame under 80lbs of load to simulate double legged stance, a baseline normal scan with intact syndesmotic ligaments and a second after surgical ligament sectioning. All syndesmotic ligaments were released through a direct lateral approach to the distal fibula. Models of the bones were created from scans using Disior Bonelogic. Distance mapping was used to evaluate DTFS widening in the first 1cm, 3cm, and 5cm from the joint after injury. Post-injury distance maps were compared to the contralateral baseline normal scan as a control. FAO was measured post-injury and compared to the difference in DFTS widening between the injured leg and its contralateral, healthy control. Linear regression and Spearman’s correlations were used to evaluate relationships.

Results

Significant correlations between hindfoot alignment and DTFS widening were identified at every level in the syndesmosis. Spearman’s rho values at 1cm, 3cm, and 5cm were 0.436 (p = 0.01004), 0.563 (p < 0.001), and 0.653 (p < 0.001), respectively.
Extremely varus FAO measurements (FAO < -10%) showed negligible changes in syndesmotic opening. Feet with less varus hindfoot alignments followed the positive correlation between widening and FAO closely.
Linear regression demonstrate strong positive trends with R2 values at 1cm, 3cm, and 5cm of 0.183, 0.284, and 0.384, respectively.

Discussion

In this cadaveric study, we confirmed our hypothesis showing that valgus FAO was correlated with syndesmosis opening from an uninjured to an injured site. These data are in accord with prior findings relating FAO and DTFS opening in flatfeet and additionally demonstrate a stronger positive trend in the presence of known injury with smaller changes in tibiofibular distances after injury for extreme varus alignments.
This study provides important context to the clinically relevant comparison of contralateral feet. The trend in our data allows for predictable results for the degree of injury in patients with valgus foot alignment, which could be extremely useful in a clinical setting when diagnosing syndesmotic injuries in valgus alignments. However, for physiological and varus FAO, it becomes more challenging to predict the amount of DTFS widening. In severe varus hindfoot, DTFS opening after injury may be more difficult to detect under weightbearing.