Routine MRI Signal Intensity as a Surrogate of Subchondral Bone Healing: Validation Against Micro-CT and Histology in...

Area of Science:

• Orthopedics
• Radiology
• Biomaterials Science

Background:

• Osteochondral defects pose significant clinical challenges.
• Assessing bone regeneration after scaffold implantation requires reliable methods.
• Current methods may be invasive or involve radiation exposure.

Purpose of the Study:

• To evaluate if T1-weighted spin-echo (T1-SE) and proton-density fast spin-echo (PD-FSE) MRI signal intensity (SI) can serve as non-invasive markers of bone regeneration.
• To correlate MRI metrics with micro-computed tomography (micro-CT) and histological assessments of bone repair.
• To determine the utility of MRI for monitoring bone regeneration after osteochondral scaffold implantation.

Main Methods:

• Sheep with trochlear defects received either a scaffold or no treatment.
• MRI scans (T1-SE, PD-FSE) were performed at 30, 180, and 365 days post-implantation.
• Radiologists used Likert scales for apparent mineralization and SI normalization; contrast-to-noise ratio (CNR) was computed and correlated with micro-CT and histology.

Main Results:

• Likert ratings from both T1-SE and PD-FSE correlated significantly with micro-CT and histological measures of new bone formation.
• PD-FSE CNR showed an inverse association with bone regeneration, decreasing as regeneration increased.
• T1-SE CNR did not show significant associations with bone regeneration metrics; inter-reader agreement was excellent.

Conclusions:

• Reader-based Likert assessments and PD-FSE CNR are valuable, complementary non-invasive markers for subchondral bone regeneration.
• MRI shows potential for radiation-free follow-up and endpoint selection in translational osteochondral repair studies.
• T1-SE CNR is not recommended as a standalone quantitative marker for early bone healing assessment.