Anterolateral ligament in pediatric knees A radiographic study

O R I G I N A L R E S E A R C H

Anterolateral ligament in pediatric knees: A radiographic study Downloaded from http://journals.lww.com/c-orthopaedicpractice by rmPZughc3fjoCtCwopXeCpwrDODu1qJ6K6KwBbNN8Enh3ioCbziEqMSA2lcR3xKaPZl1gIUM0RoOY4sD+HQ1MhVycqAFfLLuGMUCXFRFuBKO3GHKWMyYIA== on 06/24/2020

Adel Hegaze, MDa, Khalid Khashoggi, MDb, Abdulraof Alqrache, MDc, Abdullah Ashour, MDa and Hesham N. Mustafa, MDd a

Orthopedic Department, Faculty of Medicine, King Abdulaziz University, Saudi Arabia Radiology Department, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia c Clinical Biochemistry Department, Faculty of Medicine – Rabigh, King Abdulaziz University, Jeddah, Saudi Arabia d Anatomy Department, Faculty of Medicine, King Abdulaziz University, Saudi Arabia b

INTRODUCTION

ABSTRACT Background: The anterolateral ligament (ALL) is a true well-defined ligament in the knee first described in 1879 by Segond. After the work of Claes et al., several studies were conducted about biomechanics and its role in stability of the knee. The anatomical existence of the ALL has been studied by and various radiographic diagnostic modalities and in cadavers. It originates from lateral femoral epicondyle and is inserted between Gerdy’s tubercle and the fibular head. There has been controversy about the existence of ALL in pediatric patients. The aim of this work was to confirm the presence of ALL in pediatric patients by using MRI. Materials and Methods: We reviewed the knee MRI scans of 100 pediatric patients (ages between one and 12 yr) who had no knee injury or congenital deformity and had been evaluated by an expert radiologist.

Results: The ALL was detected in 90% of the pediatric patients with the use of MRI. Conclusions: The main finding of this study was that ALL can be seen in pediatric patients using MRI. Despite numerous studies, additional research is needed to further define the role of the ALL in knee function.

Level of Evidence: Level IV. Key Words knee, anterolateral ligament, ALL, MRI, pediatric

Financial Disclosures: The authors report no conflicts of interest.

Correspondence to Hesham N. Mustafa, MD, Department of Anatomy, Faculty of Medicine, King Abdulaziz University, PO Box 80205, Jeddah 21589, Saudi Arabia Tel: +966 566 764 762; fax: +966 126 400000 (20123); e-mail: hesham977@hotmail.com.

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T

he anterolateral ligament (ALL) was first described in 1879 by Paul Segond, a French surgeon, as a fibrous band.1 In the past the status of the ALL as a true ligament has been questioned, but it was recognized as a true ligament in adults in 20122,3 by the description of its origin and insertion. In addition, some studies used different radiographic modalities to describe the anatomy of the ALL. Recent articles have reported the function and biomechanics of the ALL and its role in knee stabilization and pivot shifting phenomena in comparison to other knee stabilization structures.2–5 The ALL is a well-defined ligament. It originates from the lateral femoral epicondyle, distal and anterior to the lateral collateral ligament. It crosses the joint line in an oblique manner, with firm attachments to the lateral meniscus and inserts between Gerdy’s tubercle and the tip of the fibular head.1,6 The ligament stabilizes and limits internal rotation of the knee joint; therefore, it affects the pivot shift mechanism.7–10 In literature, few studies report the ALL in pediatric patients, and most of those were cadaver studies. Although some of those studies succeeded in locating the ligament and describing its anatomy,11,12 others denied it.9,13 One study that located it showed a 100% result of the ALL in 20 specimens studied,11 and another found it in 64% of specimens studied.12 In this study, we aim to confirm the presence of ALL using magnetic resonance imaging (MRI).

MATERIALS AND METHODS Ethical Review and Study Design This radiographic study has been carried out in accordance with the Code of Ethics of the World Medical Association (Declaration of Helsinki). Patients provided a signed informed consent for the procedures. This study was approved by the Unit of Biomedical Ethics Research Committee of our institution with an approval number of 587-18.

Patient Selection A radiology consultant reviewed 100 pediatric patients who had an MRI of the knee without intravenous contrast. The Volume 31 Number 4 July/August 2020

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patients were between 1 and 12 yr of age (mean age, 8.6 yr; range 10.7 yr), and had diagnoses other than severe knee injury, infection, congenital anomalies, marked deformity, or hemarthrosis. The ALL was followed at its anatomical course, at the tibial attachment, the joint line, and the femoral attachment. All patients were imaged on a 1.5-T Symphony system (Siemens Medical Solutions, Erlangen, Germany), 3-T Verio system (Siemens Medical Solutions, Erlangen, Germany), or 3-T Skyra system (Siemens Medical Solutions, Erlangen, Germany). All the examinations included a minimum of the following sequences: axial proton density (PD)-weighted fast spin-echo (FSE) or turbo SE (TSE) sequence; coronal PD- and T2-weighted FSE or TSE sequences; and either sagittal conventional PD- and T2-weighted SE and FSE or TSE T2-weighted sequences or sagittal PD- and T2-weighted FSE or TSE sequences. Additional sequences included T1-weighted and T1- or T2-weighted gradientrecalled echo sequences. All FSE and TSE sequences were fat suppressed.

The examinations were performed using a single 3D MRI system (Magnetom Verio, Siemens Healthcare, Erlangen, Germany). The imaging protocol consisted of standard multiplanar 2D FSE acquisitions and a SPACE 3D FSE acquisition (Siemens Medical Solutions, Erlangen, Germany).

The conventional sequences included a sagittal PD-weighted FSE and T2-weighted acquisitions, coronal PD fat-saturation sequence, and axial and coronal fat saturation T2-weighted acquisitions. A sagittal T1-weighted acquisition was also utilized.

FIGURE 2. Joint line (arrow).

RESULTS The ALL was detected in 90 of 100 patients (90%). The ligament was visible using the MRI axial view from the femoral attachment (Figure 1) through the joint line (Figure 2) all the way to the tibial attachment (Figure 3) and in the coronal view indicated by arrows (Figure 4). The anterior part of the ligament at the femoral attachment and tibial attachment was a hypointense structure, which was approximately midway between Gerdy’s tubercle and the tip of the fibular head. The femoral attachment had significant variation; however, it was seen approximately 10-mm distal to the femoral epiphyseal line.

DISCUSSION

FIGURE 1. Femoral attachment (arrow).

The ALL of the knee is a capsular structure that runs from the lateral femoral epicondyle to the lateral tibial plateau.14 This structure was initially described by Segond15 in 1879 as a pearly fibrous thickening of the lateral knee capsule that emerged from the iliotibial band (ITB). In recent years, studies have been conducted to understand the anatomical structure and biomechanical role of the anterolateral aspect of the knee in adults.16,17 Several terms and structures related to the ALL include the anterolateral capsule, capsulo-osseous layer of the ITB, midthird lateral capsular ligament, anterior band of the lateral collateral ligament, and anterior oblique band.16,17 The term “anterolateral ligament” was coined by Vieria et al.18 in 2012, and it appears to have become the common term used in recent literature.17

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FIGURE 3. Tibial attachment (arrow).

The landmark study by Claes et al.1 in 2013 renewed interest in the anterolateral anatomy of the knee. In recent years, many studies proved the existence of the ALL in adults and described its anatomy and the possibility to detect it

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radiographically.2–4 A systematic review conducted by Van der Watt et al.14 found that the ALL was a distinct entity present in 96% of examined specimens, although prevalence across individual studies varied considerably.

There is a significant debate about the ALL with regard to its existence, anatomy, and role in knee stability. In addition, it has been a source of controversy among the orthopaedic community.19 Sabzevari et al.13 used anatomical investigation in 21 fetal knees and were unable to find the ALL. In 2016, Shea et al.9 used eight pediatric cadavers and identified the ALL only in one specimen and in 2017, 14 pediatric specimens were used and the ligament was identified in nine of 14.12 Anatomic and histological studies have proven the presence of the ALL. In 2016, Helito et al.11 located the ALL in 20 fetal cadavers. In another study conducted by Parker and Smith in 2016,20 the ALL was identified in 96.2% of the knees studied. The authors found three articles published in 2017; the first article identified the ligament in all 40 cadaveric fetal knees studied,21 the second article identified the ligament in all 26 knees studied,22 and the third article conducted by Shea et al.12 identified it in nine of the 14 pediatric patients studied. In 2018, the ALL was reported in 29 out of 30 cadaveric knees and in eight out of 12 cadaveric knees in two different articles.23,24 Nonetheless, the year 2018 marked the use of MRI in locating the ALL in pediatric patients.23–25 Many studies used radiographic imaging to identify ALL. Muramatsu et al.26 used three-dimensional MRI and located the ALL in 100% of both noninjured knees (40 knees) and ACL-injured knees (60 knees). In 2018, Helito25 used the MRI to identify the ALL in around 70% of 363 knees of participants who were 18 yr of age or younger. Liebensteiner et al.27 imaged 61 pediatric patients by using MRI and concluded that the ALL was present in pediatrics and could be visualized by MRI. A study published in 2019 visualized ALL injuries in 30 patients out of 34 with ACL injury using MRI.28 In 2015, a study conducted by Caterine et al.6 identified the ALL in all 19 cadaveric knees studied using MRI, anatomical dissection, and histological analysis. Biomechanically, the ALL plays a key role in the anterolateral rotatory laxity as concluded by Park et al.29 In 2018, after reviewing several articles about ALL, Zaffagnini et al.19 concluded that the ALL does exist.

In this study, the authors included pediatric patients between 1 and 12 yr old without knee injuries. We located the ALL using MRI in 90% of the cases distributed among all the patients. The results of this study were similar to the results published by Van der Watt et al.14 that found the ALL in 96% of an adult sample, which suggests that the ALL may be absent in a small portion of individuals from birth.

CONCLUSIONS FIGURE 4. Coronal proton density with saturation image (TR = 3180, TE = 33) in a 12-year old male patient showing the normal appearance of the anterolateral ligament (arrows).

The main finding of this study is that anterolateral ligaments (ALL) can be seen in pediatric patients using MRI. Despite numerous studies, additional research is needed to further define the role of the ALL in knee function.

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