Summary

This study revealed that the iliotibial band and lateral joint capsule attach equally to the Segond fracture, suggesting that both contribute to the pathogenesis of the injury.

Abstract

Introduction

The Segond fracture was classically described as an avulsion fracture of the anterolateral structures of the knee, like the iliotibial band (ITB). Recently, some authors have attributed its pathogenesis to a unique capsular ligament, the “anterolateral ligament”. Biomechanical studies that have attempted to reproduce this fracture in vitro, have reported conflicting findings [1,2]. The purpose of this study was to determine: 1) the anatomic characteristics of the Segond fracture on magnetic resonance imaging (MRI) and 2) its attachments to anterolateral structures of the knee.

Methods

From October 2007 to March 2016, a total of 36 ACL injured patients with Segond fractures (33 males, 3 females; mean age: 23.2 ± 8.4 years) were seen at our institution and enrolled in this study. MRIs were reviewed by two examiners to determine the anatomic characteristics of the Segond fracture, including: proximal-distal (PD) length, anterior-posterior (AP) width, PD distance to lateral tibial plateau, AP distance to Gerdy’s tubercle (GT), and AP distance from GT to the posterior aspect of the fibular head (Figure 1). Attachment of the anterolateral structures to Segond fragment was then categorized as ITB or anterolateral capsule. Inter-rater reliability of the measurements was determined by calculating Spearman ranked.

Results

On MRI, the mean distance of the midpoint of the fracture to the tibial plateau was 7.8mm ± 2.7mm. The center of the fracture was 49.9% of the distance between Gerdy’s tubercle and the posterior aspect of the fibular head. These measurements showed good reliability (IRR >0.75).
Analysis of soft tissue structures attached to the fragment (IRR=0.74) revealed the ITB attached in 34/36 cases and capsule attached in 34/36 cases (Figure 2). One patient had just capsule attachment, another had only ITB attached, and the last showed neither clearly attached.

Discussion

The most important finding of this study was that the ITB and lateral capsule both attach to the Segond fracture in 94% of the cases. This cohort of patient’s with Segond fractures is consistent with previous literature describing the soft tissue attachments to the Segond fracture [1]. In the present study, the finding that the ITB and capsule attach equally to the Segond fracture suggests that both contribute to the pathogenesis of the injury. Considering the strength of the ITB, it is reasonable to assume that it imparts significantly greater force on the lateral tibia during the ACL injury mechanism [3]. However, considering the proximity of the posterior fibers of the ITB and the lateral capsule, these structures are difficult to separate [4]. In this study, Segond fractures represent a combined avulsion of the ITB and lateral capsule in 94% of the cases, suggesting that both contribute to the pathogenesis of the injury. Future studies will examine Segond fracture healing and the influence on quantitative pivot shift in patients with ACL injury.

[1] Campos, Rads 2001
[2] Claes, Arthroscopy 2014
[3] Rahnemai-Azar, AJSM 2016
[4] Porrino, AJR 2015