Imaging Structural Abnormalities in the Hip Joint: Instability and Impingement as a Cause of Osteoarthritis

Abstract

Osteoarthritis is thought to be caused by a combination of intrinsic vulnerabilities of the joint, such as anatomic shape and alignment, and environmental factors, such as body weight, injury, and overuse. It has been postulated that much of osteoarthritis is due to anatomic deformities. Advances in surgical techniques such as the periacetabular osteotomy, safe surgical dislocation of the hip, and hip arthroscopy have provided us with effective and safe tools to correct these anatomical problems. The limiting factor in treatment outcome in many mechanically compromised hips is the degree of cartilage damage which has occurred prior to treatment. In this regard, the role of imaging, utilizing plain radiographs in conjunction with magnetic resonance imaging, is becoming vitally important for the detection of these anatomic deformities and pre-radiographic arthritis. In this article, we will outline the plain radiographic features of hip deformities that can cause instability or impingement. Additionally, we will illustrate the use of MRI imaging to detect subtle anatomic abnormalities, as well as the use of biochemical imaging techniques such as dGEMRIC to guide clinical decision making.

Is the Damage of Cartilage a Global or Localized Phenomenon in Hip Dysplasia, Measured by dGEMRIC?

“…Patients with DDH are considered to be at risk for having OA develop owing to the loss of GAG as an early event in the development of hip OA [16]. Therefore, observation of cartilage integrity and the amount of GAG is important in evaluating the effect of joint-preserving hip surgery on OA progression [17,25].…”

Can Radiographic Morphometric Parameters for the Hip Be Assessed on MRI?

“…We determined the LCE angle, Tönnis angle, and extrusion index on AP radiographs and the ACE angle on false-profile views using OsiriX Version 3.9 (Pixmeo, Geneva, Switzerland) and the OsiriX plug-in Orthopaedic Studio Version 1.2 (Carl Siversson, Department of Medical Radiation Physics, Lund University, Lund, Sweden; http://orthostudio.spectronic.se) manually using standard technique as previously described [19]. The same observers evaluated acetabular retroversion with use of the criteria proposed by Reynolds et al [30].…”

“…FAI is defined as the abutment between the proximal femur and the acetabular rim, either as a result of reduced femoral head-neck offset (cam type) or acetabular (pincer type) overcoverage or both [14,15]. Ganz et al [14] and others [19] have emphasized the importance of detection of such anatomic abnormalities of the hip, which may lead to pain and osteoarthritis (OA) in young adults [14,19]. In most cases, a combination of cam and pincer forms is present called mixed-type impingement [3].…”

Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) and morphologic MRI of cartilage in the long-term follow-up after Legg-Calvé-Perthes disease (LCPD)

“…However, the unaffected hip is commonly used as control in studies on unilateral hip conditions. 11 In four hips of this group, low-degree cartilage defects could be observed. It may be possible that in healthy patients without history of hip disorders, the penetration of Gd-DTPA 2into cartilage matrix may have been even lower, resulting in higher dGEMRIC values.…”

“…The use of MRI is an established method for assessing osteoarthritic cartilage changes. [9][10][11] The modified classification according to Outerbridge has gained acceptance in the grading of morphological cartilage damage. [12][13][14] High validity of the Outerbridge classification based on morphologic MRI cartilage sequences was noted by direct comparison with arthroscopic examinations in the knee joint and subtalar joint.…”