Utility of MR Imaging in Developmental Dysplasia of Hip

Review Article

Austin J Radiol. 2016; 3(3): 1052.

Utility of MR Imaging in Developmental Dysplasia of Hip

Poonam Sherwani1*, Adweta Vire1, Rama Anand2 and Anil Aggarwal3

1Department of Radiodiagnosis, Chacha Nehru Bal Chikitsalya Hospital, India

2Department of Radiodiagnosis, Lady Harding Medical College and associated Hospitals, India

3Department of Orthopaedics, Chacha Nehru Bal Chikitsalya Hospital, India

*Corresponding author: Poonam Sherwani, Department of Radiodiagnosis, Chacha Nehru Bal Chikitsalya Hospital, Geeta Colony, New Delhi, India

Received: May 30, 2016; Accepted: August 23, 2016; Published: August 29, 2016


Developmental dysplasia of the hip is the most common cause of an unstable hip in paediatric population. It can be assessed using various radiological modalities. However due to excellent soft tissue characterization and with no radiation hazards, Magnetic Resonance Imaging (MRI) plays an important role in the early detection as well as in the evaluation of various soft tissue obstacles that can cause hindrance in reduction. Preoperative MR imaging also helps in determining the acetabular labral coverage which further guides the orthopaedic surgeon in planning the management. In postoperative cases, apart from the assessment of adequacy of reduction, immediate and delayed post operative complications like ischemic necrosis can be detected earlier than with other imaging modalities thus helping in appropriate and timely management. Here we present a pictorial assay of the MR imaging techniques and the findings with a focus on various important anatomical structures required to be evaluated while performing and reporting MRI of these cases.

Keywords: Acetabulum; Complications; Computed tomography (CT); Developmental dysplasia of hip (DDH); Magnetic resonance imaging (MRI); Radiography


Developmental Dysplasia of Hip (DDH), also termed as infantile hip dysplasia is the most important cause of unstable hip in children [1]. Left hip is more commonly involved (40 to 60% of cases) with bilateral involvement in 20% [2]. It includes spectrum of developmental disorders in which mild dysplasia refers to stable and aligned hip while in severe cases the hip is unstable and dislocated [3]. DDH occurs either due to the acetabular dysplasia or due to the laxity of the supporting structures. The hip joint develops from the cartilaginous anlage at around 4 to 6 weeks gestational age. The femoral head gets completely encircled by the acetabular cartilage. Due to disproportionate growth of the femoral head and the surrounding cartilage, less than 50% coverage of the femoral head occurs at birth. However weeks after the birth, the acetabular cartilage develops more rapidly than the femoral head which results in progressively increased coverage [4]. Therefore minimal structural support of the femoral head is during late gestation and few months after birth so there are more chances of hip dislocation or subluxation in this period. Intrauterine factors like oligohydrominos and post natal positioning such as wrapping the legs in extended position affect the acetabular development [5]. The Risk factors include positive family history, breech presentation, torticollis, scoliosis and structural abnormalities which include underdevelopment of anterior capsule, ligament of Bigelow or rectus muscle [6]. Early diagnosis and treatment are important as the acetabulum is susceptible for remodeling in the first 6 weeks.

Clinical tests play a major role in the early detection of DDH. Imaging studies which include plain films, Ultrasound, CT and MRI supplement the clinical tests both for diagnosis as well as for follow up. Plain films are valuable in children >6 months after the femoral head and acetabular ossification occurs. Ultrasound plays an important role in the evaluation of acetabular morphology before the appearance of ossific nucleus and also in the dynamic examination. CT has a limited role and is only done in postoperative cases for assessment of adequacy of reduction when the patient is in spica cast and ultrasound cannot be done [7]. To minimize the radiation, low dose CT technique should be employed [8]. Due to better soft tissue characterisation and no risks of ionising radiation, MRI is the excellent modality to show the relationship of femoral head and the acetabulum even when they are not ossified. It is preferred to look for- the femoral ossific nucleus, the acetabulum, and the soft tissue obstacles in the reduction in non reducible cases and also to look for the immediate and delayed post operative complications like ischemia which can be detected earliest on MRI.


MRI can be used in early detection and evaluation of DDH. The femoral capital epiphysis displays intermediate signal on T1W and hyperintense signal on T2W. Due to its multiplanar imaging capability ,the position of the capital epiphysis can be demonstrated on coronal imaging especially when it is uncertain on conventional radiograph and the ossific nucleus is not visible on plain radiograph. Axial and coronal MR images are most useful and small surface coils with high spatial resolution are necessary to evaluate DDH. Essential sequences include T1W for portraying the ossified elements with good anatomical detail, T2W for effusion, PDFS to see for cartilage a s well as labrum and dynamic Post contrast T1W FS for the early detection of ischemia in post operative cases.MR imaging has numerous advantages over radiography particularly in looking for the ossified femoral nucleus as well as in better demonstration of morphology of the acetabular dysplasia in single examination with lack of ionising radiation. Also with the proper use of sequences arthrogram like image can be produced [9]. MR is also used to evaluate the causes of non reducibility in the preoperative imaging and also to detect the immediate and delayed post operative complications. Aditi et al.

[10] described the use of postoperative MRI after spica cast to look for the successful reduction and also to see for the post reduction complications.

However, limitations of MRI include high cost, need for sedation in children due to long scanning time and lack of dynamic evaluation. Also immediate post operative imaging cannot be done if the non compatible MR implants are used.

In general, MRI is only indicated for complicated or severely dysplastic hips and in post operative unsuccessful reduction and to see for post operative complications [6].

MR Techniques and interpretation

Sedation is given in infants and younger children to optimize the MR imaging technique and to avoid the motion artifacts. Proper sedation guidelines are to be followed and commonly used sedatives include barbiturates and fentanyl. Proper monitoring should be done during and after the sedation.

For imaging and comparison of both the hips large FOV is required for which body coil is used however dedicated Hip coil is used to provide high resolution images. Examination is performed with 512 x 256 or 256 x 256 acquisition matrix using 1 or 2 excitations (NEX). Thin sections (3 or 4 mm) are used with minimal interslice gap. Standard imaging protocols in hip includes coronal T1W Spin echo, coronal short tau inversion recovery, axial T2 W Fast Spin Echo (FSE), fat saturated oblique sagittal FSE, Proton Density (PD) FS and axial FSE PD images. Additional protocols include coronal three-dimensional spoiled gradient recall echo with fat suppression and post contrast FS T1W.

Anatomy with normal MR appearance

Important anatomical structures to be evaluated and to be reported in hip in DDH with their typical appearance on MRI are:

1. Acetabular Labrum: It is the fibro cartilaginous rim which deepens the acetabular cavity. On routine MR imaging, the normal labrum is seen as dark signal triangle covering the articular cartilage at the peripheral margin of the acetabulum and are named according to the location as anterior superior, superior and posterior superior labrum (Figure1a and b).