TIBIAL FATIGUE FRACTURE AN OVERVIEW

1. FATIGUE FRACTURE - TIBIA MERCURY IMAGING INSTITUTE SCO 172-173 SEC 9C CHANDIGARH MERCURY IMAGING CENTRE SCO 16-17 SEC 20D CHANDIGARH 18 YR OLD FEMALE WITH H/O TIBIAL PAIN. RECENT HISTORY OF INCREASED PHYSICAL ACTIVITY IN THE TRAINING CAMP. MR imaging -Single best technique in assessment of patients with suspected tibial stress injuries in some patients with negative MR imaging findings, CT can depict osteopenia, which is the earliest finding of fatigue cortical bone injury.

2. OVERVIEW OF THE CT , MR FINDINGS IN FATIGUE FRACTURES.

3. PATHOGENESIS Pathogenesis of stress fracture is poorly understood. Stresses related to daily activities stimulate the remodeling process. Increased osteoclasticresorptionis the initial response to abnormal stress. If increased stress persists, imbalance between bone resorption and bone replacement leads to weakening of the bone. Weight bearing, muscle actions, and muscle fatigue may play a role in increasing stress on bone. In the tibia, tensile forces are produced along its anterior convex side, while compressive forces occur along its posterior concave margin . Accelerated intracortical remodeling causes microscopic cracks, osteopenia, and formation of resorption cavities that may join in larger lesions. Stresses in cancellous bone may initially result in microfractures. If the inciting activity is not decreased, the accumulation of microdamages may result in stress fracture of cortical or trabecular bone .

5. Marrow edema./ marrow bruise.

6. Resorption cavities in the cortex.

7. Osteopenia .

8. Striations

9. Gray cortical sign ( Subtle illdefinition of the cortex)

11. FAT SATURATION SEQUENCE - BETTER DEPICTION OF MEDULLARY EDEMA , BRUISE , CONTUSION, PERIOSTEAL EDEMA . PERIOSTEAL EDEMA

12. RESOPTION CAVITIES Focal ill-defined areas of edema / hyperintense haze on STIR / T2w sequences

13. SIMULTANEOUS INVOLVEMENT OF THE ANTERIOR AND POSTERIOR PERIOSTEUM ( THIS IS AN IMPORTANT POINT TO DIFFERENTIATE STRESS/ FATIGUE RELATED MR FINDINGS FROM THE MITOTIC / INFECTIVE LESIONS TI W T2 W STIR