Occult intraosseous fracture: detection with MR imaging

Area of Science:

• Orthopedic imaging
• Musculoskeletal radiology
• Bone injury diagnostics

Background:

• Plain radiographs are standard for knee injuries but may miss subtle bone damage.
• Symptomatic knee injuries without radiographic fracture require further investigation.
• Microscopic bone injuries can cause significant pain and dysfunction.

Purpose of the Study:

• To evaluate magnetic resonance (MR) imaging findings in patients with symptomatic knee injuries and normal radiographs.
• To characterize the MR appearance of bone abnormalities in these cases.
• To determine if MR findings correlate with other imaging modalities and clinical outcomes.

Main Methods:

• Retrospective review of MR images from eight patients with recent, symptomatic knee injuries and no fractures on plain radiographs.
• Analysis of T2-weighted, T1-weighted, and proton density MR sequences.
• Correlation with bone scintigraphy in two patients and follow-up MR imaging in two patients.

Main Results:

• T2-weighted MR images showed intraosseous high signal intensity; T1-weighted and proton density images revealed corresponding low signal intensity.
• Abnormalities were predominantly subchondral in patients without direct contusion.
• Bone scintigraphy confirmed increased activity in corresponding areas.
• Follow-up MR imaging demonstrated complete resolution of abnormalities within 3 months.

Conclusions:

• MR imaging findings suggest microscopic compression fractures of trabecular bone.
• MR imaging is a valuable tool for diagnosing subtle bone injuries in the knee.
• The findings are consistent with early or microscopic stress fractures.