MRI of Hip Osteoarthritis and Implications for Surgery

Osteoarthritis (OA) is the most common form of joint disease, affecting over 33% of people over 65 years old. The patho-physiology of OA is complex and manifested by changes at the molecular, cellular, and tissue levels. High resolution, three-dimensional (3D) imaging methods provide the opportunity to quantitatively assess changes in the morphology and composition of multiple articular joint tissues in small animal models. Two of the main imaging modalities used in research to examine articular tissue changes are magnetic resonance imaging MRI and micro-computed tomography (μCT). MRI is the clinical gold standard for assessment of joint inflammation and damage associated with arthritis. μCT imaging, which relies on a material’s ability to attenuate X-rays, provides very high resolution 3D images and increased contrast between bone and soft tissue. This chapter explains in detail the uses and limitations of MRI and μCT with respect to imaging cartilage in OA. Other imaging modalities, such as ultrasound imaging, vascular imaging, reactive oxygen species imaging, two-photon laser scanning microscopy and atomic force microscopy, are also discussed.

To develop a semiquantitative MRI-based scoring system (HOAMS) of hip osteoarthritis (OA) and test its reliability and validity.

Fifty-two patients with chronic hip pain were included. 1.5T magnetic resonance imaging (MRI) was performed on all patients. Pelvic radiographs were scored according to the Kellgren–Lawrence (KL) system. Clinical outcomes were assessed by the hip osteoarthritis outcome score (HOOS). MRIs were analyzed using a novel whole-joint MRI score that incorporated 13 articular features. Reliability was determined on a random subset of 15 cases. Weighted-kappa statistics and overall agreement were used as a measure of intra- and inter-observer reliability. Associations between MRI features and radiographic OA severity were calculated using Cochran–Armitage test for trend. Ordinal logistic regression was used to assess associations between MRI features and severity of pain and functional limitation.

Distribution of radiographic grading was: KL 0 = 12 (27%), KL 1 = 11 (25%), KL 2 = 14 (32%), KL 3 = 5 (11%) and KL 4 = 2 (5%). Intra-reader reliability for the different features ranged from 0.18 (cysts) to 0.85 (cartilage). Inter-reader reliability ranged between 0.15 (cysts) and 0.85 (BMLs). Low kappas were due to low frequencies of some features as overall percent agreement was good to excellent (83.8% and 83.1%). There was a strong association between MRI-detected lesions and radiographic severity (P = 0.002). Non-significant trends were observed between MRI features and clinical outcomes.

MRI-based semiquantitative assessment of the hip shows adequate reliability. Presence of more severe MRI-detected intraarticular pathology shows a strong association with radiographic OA. The results suggest possible associations between MRI-detected pathology and clinical symptoms.

To test whether serum transforming growth factor-beta 1 (TGF-β1) predicts incident and progressive hip or knee radiographic OA (rOA).

Serum TGF-β1 was measured for 330 participants aged 45 years and older in the Johnston County Osteoarthritis Project, with paired longitudinal films available for 618 hips and 658 knees. Incident and progressive rOA were defined using Kellgren–Lawrence (K–L) grade as well as osteophyte (OST) and joint space narrowing (JSN) scores. Natural logarithm transformation was used to produce near-normal distributions for continuous TGF-β1 (lnTGF-β1). Separate multivariable Weibull regression models were used to provide hazard ratios (HRs) for a 1-unit increase lnTGF-β1 with each rOA outcome, accounting for variable follow-up times and clustering by individual, adjusted for age, race, gender, and body mass index (BMI). Interaction terms were considered statistically significant at P < 0.10.

The mean (±SD) age of the sample was 61.9 ± 9.7 years, the mean BMI was 30.3 ± 6.9 kg/m², with 60.6% women and 42.4% AA. The mean (±SD) TGF-β1 was 17.8 ± 6.1 ng/ml; follow-up time was 6.1 ± 1.3 years. There were no significant interactions by race or gender. HRs showed no significant relationship between lnTGF-β1 and incident or progressive rOA, OST, or JSN, at the knee or the hip.

Levels of TGF-β1 do not predict incident or progressive rOA, OST, or JSN at the hip or knee in this longitudinal, population-based study, making it unlikely that TGF-β1 will be a robust biomarker for rOA in future studies.