Longitudinal analysis of T1ρ and T2 quantitative MRI of knee cartilage laminar organization following microfracture surgery

ObjectiveTo quantitate longitudinally the radiographic properties of different layers of repaired tissue following microfracture (MFx) surgery using T1ρ and T2 magnetic resonance imaging (MRI).Design10 patients underwent MFx surgery to treat symptomatic focal cartilage defects (FCD). Sagittal three-dimensional (3D) water excitation high-spatial resolution (HR) spoiled gradient recalled (SPGR) for quantitative T1ρ and T2 mapping were acquired for each patient 3–6 months and 1 year after surgery. Cartilage compartments were segmented on HR-SPGR images, and T1ρ and T2 maps were registered to the HR-SPGR images. T1ρ and T2 values for the full thickness of deep and superficial layers of repaired tissue (RT) and normal cartilage (NC) were calculated, and compared within and between respective time points. A p-value < 0.05 is considered statistically significant.ResultsThe majority of FCD were found in the MFC. The average surface area of the lesions did not differ significantly overtime. At 3–6 months, RT had significantly higher full thickness T1ρ and T2 values relative to NC. At 1 year, this significant difference was only observed for T1ρ values. At 3–6 months follow-up, the RT's superficial layer had significantly higher T1ρ and T2 values than the deep layer of the RT and the superficial layer of NC. At 12 months, the superficial layer of the RT had significantly higher T1ρ values than the RT's deep layer and the NC's superficial layer.ConclusionT1ρ and T2 MRI are feasible methods for quantitatively and noninvasively monitoring the maturation of repaired tissue following microfracture surgery over time.