Abstract
Objectives:
Articular cartilage injury has been identified as a risk factor for poor outcomes following hip arthroscopy for femoroacetabular impingement syndrome (FAI). The purpose of this study was to evaluate the efficacy of magnetic resonance imaging (MRI) in detecting cartilage defects, and to identify specific MRI findings associated with cartilage injury.
Methods:
All patients undergoing hip arthroscopy between February 2015 and May 2017 at one institution were enrolled in a prospective cohort. Intra-articular findings were documented at the time of surgery. MRI reports were retrospectively reviewed for radiologist-reported articular cartilage, osseous or synovial abnormalities. Sensitivity and specificity of MRI findings were calculated; multivariate logistic regression analysis determined which findings were associated with high-grade chondral damage at time of arthroscopy and used to create an online risk calculator, https://orthop.washington.edu/hiprisk/.
Results:
Out of a total of 598 patients who underwent hip arthroscopy, 550 had MRI reports available for review (92%). Grade III and IV cartilage injuries were reported on arthroscopy in 70 patients (13%) of average age 33 ± 13 years. On univariate analyses, individual MRI findings were not found to be sensitive in detection of articular cartilage injury (mean 22%, range 1.4% – 46%), but positive findings were highly specific (mean 90%, range 76% – 99%). Multivariate analysis revealed that older age (OR 1.09 [1.06-1.11], p < .001) and osseous findings such as subchondral cyst or edema (OR 4.77 [2.51-9.05], p <.001) were most predictive of grade III and IV defects (p < .001). An example of use of the online calculator is in Figure 1.
Conclusions:
MRI was a specific but not sensitive tool in diagnosing articular cartilage injury. Surgeons should be aware that osseous findings such as cysts or edema are highly predictive of full-thickness cartilage loss in FAI.