Osteoarthritis: what does imaging tell us about its etiology?

Osteoarthritis (OA) is the most common joint disorder and a leading cause of disability. Due to an aging population and increasing obesity, the incidence of OA is rising. The etiology of OA is multifactorial and complex; thus prevention of OA remains challenging. Risk factors can be divided into person-level factors such as age, sex, obesity, genetics, race/ethnicity, and diet, and joint-level factors including injury, malalignment, and abnormal loading of the joints. This review provides a brief overview of the person-level risk factors and a more in-depth analysis of those at the joint level. It is only through an improved understanding of risk factors for the disease that we may be able to intervene meaningfully and prevent its occurrence.

Pictorial review: 'fishtail deformity' of the elbow.

Fishtail deformity of the elbow is characterised by a contour abnormality of the distal humerus, which develops when the lateral trochlear ossification centres fails to develop or resorbs. It is an uncommon complication usually following a distal humeral fracture in childhood. Whilst initially presumed to be a benign condition, long-term follow-up suggests that patients with fishtail deformity are prone to functional impairment, ongoing pain and the development of early osteoarthrosis. This paper reviews the imaging findings in fishtail deformity, the proposed aetiology and the potential long-term complications.

Overuse and traumatic injuries of the elbow.

MR imaging is a useful modality for evaluating athletes presenting with elbow pain. Osteochondral injuries and ligamentous injuries are well seen on MR imaging. Ligamentous injuries may be associated with clinical instability syndromes, the secondary signs of which may be evident on MR images. Enthesopathies and distal biceps tendon injuries are common clinical problems that may be seen in both professional and recreational athletes. Nerve compression syndromes may be investigated using MR imaging; however, the usual aim of imaging is to exclude an underlying space-occupying lesion. This article reviews the basic anatomy of the elbow joint and discusses the common osteochondral injuries, ligamentous injuries, instability syndromes, and tendinous pathologies at the elbow joint. The role of imaging in compressive neuropathies is briefly discussed.

Delayed gadolinium-enhanced magnetic resonance imaging of cartilage: clinical associations in obese adults.

OBJECTIVE: Delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) is used to assess cartilage glycosaminoglycan distribution. Our aim was to determine the relationships between self-reported pain and disability, clinical variables, and serum leptin, and dGEMRIC indices in obese subjects with and without clinical knee osteoarthritis (OA). METHODS: Seventy-seven subjects were recruited from laparoscopic adjustable gastric banding or exercise and diet-weight loss programs. The dGEMRIC index was assessed on MRI according to established protocol. Regression analysis adjusted for age, sex, body mass index (BMI), and presence of clinical knee OA. RESULTS: Mean age and BMI were 51 +/- 12.7 years and 39.6 +/- 6.2 kg/m(2). Twenty-three subjects (30%) had clinical knee OA (American College of Rheumatology criteria). The medial and lateral dGEMRIC indices were 538 +/- 80 ms and 539 +/- 86 ms. Age correlated negatively with medial (r = -0.40, p < 0.001) and lateral (r = -0.29, p = 0.012) dGEMRIC index. Subjects with clinical knee OA had significantly lower medial dGEMRIC index; however, no association was found for BMI. Varus alignment correlated with lower medial dGEMRIC index (r = -0.43, p < 0.006), while quadriceps strength correlated positively with lateral dGEMRIC index (r = 0.32, p = 0.008). There was also a negative correlation between serum leptin and lateral dGEMRIC index in women (r = -0.39, p = 0.035), with a trend in men (r = -0.52, p = 0.08). There were weak associations with physical disability, as self-reported on the WOMAC questionnaire. CONCLUSION: In obese subjects, knee dGEMRIC index was associated with age, clinical knee OA, abnormal tibiofemoral alignment, and quadriceps strength. Longitudinal studies are required to assess the potential for improvement in dGEMRIC index with interventions such as strength training.

Bone bruises associated with ACL rupture: correlation with injury mechanism.

BACKGROUND: Different patterns of bone bruising are seen on magnetic resonance imaging in acute anterior cruciate ligament ruptures. These patterns may relate to the mechanism of injury. HYPOTHESIS: There is a correlation between the mechanism of anterior cruciate ligament injury and bone bruise patterns on magnetic resonance imaging. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Data regarding the mechanism of anterior cruciate ligament rupture were collected prospectively on patients who had anterior cruciate ligament reconstructions. Inclusion criteria included a clear history of mechanism, magnetic resonance imaging within 6 weeks of injury, and no previous knee injury. Patients were divided into noncontact and contact mechanism groups. Bone bruise frequency, location, depth, and intensity were analyzed using magnetic resonance imaging and correlated with the mechanism of injury. RESULTS: Two hundred fifty-six patients were identified; 100 met the inclusion criteria, 86 were in the noncontact mechanism group, and 14 were in the contact mechanism group. The proportion of bone bruises in the lateral compartment in both groups was higher (P < .001) than in the medial compartment. Bone bruising was more frequent, deeper, and more intense in the noncontact group, with frequency (P = .019) and intensity (P < .001) scores reaching significance at the lateral tibial plateau. Medial compartment bone bruising was seen more frequently than previously reported, particularly in the noncontact group. CONCLUSION: The noncontact mechanism appears to cause more severe bone bruising in both the medial and lateral compartments.

Reliability of bony landmarks for restoration of the joint line in revision knee arthroplasty.

The aim of this study was to determine the reliability of bone landmarks for restoring the joint line in revision knee arthroplasty. The relationship of the femoral epicondyles, the tibial tubercle (TT) and the fibular head (FH) to the joint line was measured on 200 magnetic resonance imaging (MRI, 100 females, 100 males), including assessment on intraobserver and interobserver reliability. MRI scans demonstrating chondral lesions and osteoarthritis were excluded, as were patients with immature skeletons or a history of previous knee surgery. Sequences in sagittal, coronal and axial planes were used as well as cross-referencing with the same computer software. In order to account for size differences between patients, each bony landmark measurement was converted to a ratio relative to the femoral or/and tibial width. We found a transepicondylar axis equal to 3.11 degrees (+/-1.9). The average distance from the epicondyles to the joint line was respectively 23 mm on the lateral side and 28 mm on the medial side. However there was a variation of distance from the epicondyles of the joint line up to 11 mm and a significative difference was found between male and female. We determined the distances from the tip of the FH and from the TT to the joint line. The joint line-FH distance averaged 14 mm (range 4.1-22.13) with no gender difference. The joint line-TT distance was averaged 22 mm (range 10.61-32.09). We determined an epicondylar ratio (distance from the lateral epicondyle to the joint line related to the femoral width). We found this ratio averaged 28% with no gender difference (P = 0.09). There is a large variation of bony landmarks depending on the size of the individual. Considering this findings, the FH is not a reliable guide for the joint line in revision surgery. Previous studies have measured the absolute values from various landmarks to the joint line. This study provides a significant advantage, in that the level of the joint line can be determined for each individual by using a ratio to account for gender and size differences.

Disorders of the distal biceps brachii tendon.

Pathologic conditions of the distal biceps brachii tendon are of clinical interest, with partial and complete tears being the most common. However, the anatomy of the distal biceps brachii tendon makes imaging of the distal tendon somewhat difficult. An innovation in patient positioning for magnetic resonance (MR) imaging of the distal biceps tendon was recently described in which the patient lies prone with the arm overhead, the elbow flexed to 90 degrees , and the forearm supinated, so that the thumb points superiorly. The acronym FABS (f lexed elbow, abducted shoulder, forearm supinated) has been used to describe this position. The FABS position creates tension in the tendon and minimizes its obliquity and rotation, resulting in a "true" longitudinal view of the tendon. MR imaging and, to a lesser extent, ultrasonography are useful in visualizing the distal tendon and in detecting other pathologic conditions in the cubital fossa. Partial tears are usually characterized by enlargement and abnormal contour of the tendon, along with abnormal intratendinous signal intensity. In complete tears, there is discontinuity and, if the bicipital aponeurosis is also disrupted, retraction. Imaging with FABS positioning can complement conventional MR imaging, especially in the axial plane, in the assessment of the distal biceps tendon.