MRI of Labral and Chondral Lesions of the Hip

Tönnis stage 0 and 1 acetabular rim cartilage injuries: Incidence, grade, location and associated pre-surgical factors

INTRODUCTION AND PURPOSE

Articular cartilage lesions have a direct effect on the success of surgical treatment. The aim of this study was to determine the prevalence rate, location, grade, and factors associated with acetabular rim articular cartilage lesions in patients undergoing hip arthroscopy.

MATERIAL AND METHODS

A prospective study was conducted by analysing the intraoperative data of 152 hips in 122 patients treated with hip arthroscopy for femoroacetabular impingement from January 2011 to May 2016. The prevalence rate, location, and grade were calculated, as well as the pre-operative factors associated with acetabular rim articular cartilage lesions.

RESULTS

The mean age of the patients was 38.6 years. The Tönnis grade was 0 in 103 hips, and 1 in 52 hips. Acetabular rim articular cartilage lesions were present in 109 (70.3%) hips. The location of the lesions was superior-anterior. Independent risk factors for the presence of acetabular rim articular cartilage lesions were an alpha-angle equal or greater than 55°, duration of symptoms equal or greater than 20 months, and Tegner activity scale level equal or greater than 6.

DISCUSSION

Although patients were classified as Tönnis grade 0 and 1, and 3tesla MRI reported acetabular lesions in 1.3% of cases, there was a high frequency of acetabular rim cartilage lesions. Knowledge of the independent risk factors associated with acetabular rim articular cartilage lesions may assist the orthopaedic surgeon with the decision to perform hip arthroscopy.

In vitro chondrocyte toxicity following long-term, high-dose exposure to Gd-DTPA and a novel cartilage-targeted MR contrast agent

OBJECTIVE

To determine the concentrations exhibiting toxicity of a cartilage-targeted magnetic resonance imaging contrast agent compared with gadopentetate dimeglumine (Gd-DT-PA) in chondrocyte cultures.

MATERIALS AND METHODS

A long-term Swarm rat chondrosarcoma chondrocyte-like cell line was exposed for 48 h to 1.0-20 mM concentrations of diaminobutyl-linked nitroxide (DAB4-DLN) citrate, 1.0-20 mM Gd-DTPA, 1.0 μM staurosporine (positive control), or left untreated. Cell appearance, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays of metabolic activity, quantitative PicoGreen assays of DNA content, and calcein-AM viability assays were compared.

RESULTS

At 1.0-7.5 mM, minimal decrease in cell proliferation was found for both agents. At all doses of both agents, cell culture appearances were similar after 24 h of treatment. At the higher doses, differences in cell culture appearance were found after 48 h of treatment, with dose-dependent declines in chondrocyte populations for both agents. Concentration-dependent declines in DNA content and calcein fluorescence were found after 48 h of treatment, but beginning at a lower dose of DAB4-DLN citrate than Gd-DTPA. Dose-dependent decreases in MTT staining (cell metabolism) were apparent for both agents, but larger effects were evident at a lower dose for DAB-DLN citrate. Poor MTT staining of cells exposed for 48 h to 20 mM DAB4-DLN citrate probably indicates dead or dying cells.

CONCLUSION

The minimal effect of the long-term exposure of model chondrocyte cell cultures to DAB4-DLN citrate and Gd-DTPA concentrations up to 7.5 mM (3x typical arthrographic administration) is supporting evidence that these doses are acceptable for MR arthrography. The findings are reassuring given that the experimental exposure to the contrast agents at sustained concentrations was much longer than when used clinically.

A narrative overview of the current status of MRI of the hip and its relevance for osteoarthritis research - what we know, what has changed and where are we going?

OBJECTIVE

To review and discuss the role of magnetic resonance imaging (MRI) in the context of hip osteoarthritis (OA) research.

DESIGN

The content of this narrative review, based on an extensive PubMed database research including English literature only, describes the advances in MRI of the hip joint and its potential usefulness in hip OA research, reviews the relevance of different MRI features in regard to symptomatic and structural progression in hip OA, and gives an outlook regarding future use of MRI in hip OA research endeavors.

RESULTS

Recent technical advances have helped to overcome many of the past difficulties related to MRI assessment of hip OA. MRI-based morphologic scoring systems allow for detailed assessment of several hip joint tissues and, in combination with the recent advances in MRI, may increase reproducibility and sensitivity to change. Compositional MRI techniques may add to our understanding of disease onset and progression. Knowledge about imaging pitfalls and anatomical variants is crucial to avoid misinterpretation. In comparison to research on knee OA, the associations between MRI features and the incidence and progression of disease as well as with clinical symptoms have been little explored. Anatomic alterations of the hip joint as seen in femoro-acetabular impingement (FAI) seem to play a role in the onset and progression of structural damage.

CONCLUSIONS

With the technical advances occurring in recent years, MRI may play a major role in investigating the natural history of hip OA and provide an improved method for assessment of the efficacy of new therapeutic approaches.

MRI for the preoperative evaluation of femoroacetabular impingement

Femoroacetabular impingement (FAI) refers to a condition characterized by impingement of the femoral head–neck junction against the acetabular rim, often due to underlying osseous and/or soft tissue morphological abnormalities. It is a common cause of hip pain and limited range of motion in young and middle-aged adults. Hip preservation surgery aims to correct the morphological variants seen in FAI, thereby relieving pain and improving function, and potentially preventing early osteoarthritis. The purpose of this article is to review the mechanisms of chondral and labral injury in FAI to facilitate an understanding of patterns of chondrolabral injury seen on MRI. Preoperative MRI evaluation of FAI should include assessment of osseous morphologic abnormalities, labral tears, cartilage status, and other associated compensatory injuries of the pelvis. As advanced chondral wear is the major relative contraindication for hip preservation surgery, MRI is useful in the selection of patients likely to benefit from surgery.

Teaching points

• The most common anatomical osseous abnormalities predisposing to FAI include cam and pincer lesions.

• Morphological abnormalities, labral lesions, and cartilage status should be assessed.

• In cam impingement, chondral wear most commonly occurs anterosuperiorly.

• Pre-existing advanced osteoarthritis is the strongest predictor of poor outcomes after FAI surgery.

• Injury to muscles and tendons or other pelvic structures can coexist with FAI.