Persistent bone marrow edema after osteochondral autograft transplantation in the knee joint

The assessment of bone marrow edema-like signal intensity in magnetic resonance imaging (MRI) in patients after osteochondral autograft transplantation (OCT) in the knee joint is a parameter of yet indefinite value. This study determines the prevalence of persistent edema-like signal intensity in OCT patients and evaluates the correlation between edema and morphological imaging findings of the graft and clinical pain symptoms.

In this longitudinal observational study, 10 patients after OCT were followed by MRI prospectively 1 month, 3 months, 6 months, 12 months, and 24 months post-operatively. All MR examinations were performed on a 1.0 T MR unit with the same protocol using a modified scoring system (magnetic resonance observation of cartilage repair tissue-MOCART) for evaluation. Edema-like signal intensity in and beneath the osteochondral graft was assessed in its prevalence and graded using a coronal short tau inversion recovery fast spin echo (STIR-FSE) sequence: grade 1, normal; grade 2, moderate (diameter <2 cm); grade 3, severe (diameter >2 cm). The finding of edema-like signal intensity was correlated with graded parameters describing the morphology of the repair tissue assessed in a sagittal dual FSE sequence including: (a) surface of repair tissue: grade 1, intact; grade 2, damaged. (b) Cartilage interface: grade 1, complete; grade 2, incomplete. (c) Bone interface: grade 1, complete; grade 2, delamination. The finding of edema-like signal intensity was also correlated with the KOOS pain score assessing knee pain after 12 months.

Initially, after 1 month the prevalence of edema-like signal intensity was 70% (7/10 patients) and finally after 24 months 60% (6/10 patients). We found no significant relationship between the prevalence and degree of edema-like signal intensity and parameters describing the morphology of the repair tissue. Also the clinical pain score did not show significant correlation with edema.

Persistent bone marrow edema-like signal intensity in MRI is frequently found in patients after OCT and may post-operatively continue for years without significant relation to delamination and loss of the graft and knee pain.