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MRI of joint fluid in the normal and ischemic hip
Abstract:
MR images in 36 hips with documented avascular necrosis and 80 hips without evidence of joint disease were studied to determine the amount and appearance of fluid in the joint. All MRI examinations were done on a 1.5-T machine and included coronal images made with relative T2 weighting (repetition times = 2000-2500 msec, echo delays = 60-100 msec). The amount of joint fluid, which had an intense signal higher than fat, was graded from 0 to 3 and analyzed with respect to the patient's age and radiographic stage of avascular necrosis. Joint fluid was seen in 84% of presumed normal hips. Only four (5%) of 80 had enough fluid to surround the femoral neck (grade 2), and none had sufficient fluid to distend the joint capsule (grade 3). In comparison, 21 (58%) of 36 hips with avascular necrosis had grade-2 or grade-3 effusions (p less than 0.005), and some fluid was seen in all. Grade-3 effusions were seen in seven (50%) of 14 hips with flattening of the femoral head, compared with only one (5%) of 20 in which the femoral contour was normal. It is concluded that small amounts of fluid are present in both normal hips and those with avascular necrosis. In avascular necrosis, increased joint fluid may be present before radiographic abnormalities occur, but it is greatest after there is flattening of the femoral head. MRI is a highly sensitive method for detecting fluid in the hip joint.
Insights
Magnetic Resonance Imaging (MRI) detects increased joint fluid in hips with avascular necrosis. This fluid accumulation, especially larger effusions, correlates with femoral head flattening, aiding early diagnosis.
Area of Science:
- Orthopedics
- Radiology
- Biomedical Imaging
Background:
- Avascular necrosis (AVN) of the hip is a debilitating condition.
- Accurate detection of early AVN is crucial for timely intervention.
- Joint fluid analysis via Magnetic Resonance Imaging (MRI) may offer diagnostic insights.
Purpose of the Study:
- To investigate the presence and quantity of joint fluid in hips with and without avascular necrosis using MRI.
- To correlate joint fluid volume with radiographic stages of avascular necrosis.
- To assess MRI's sensitivity in detecting hip joint effusions.
Main Methods:
- Coronal T2-weighted MRI scans (1.5-T) were performed on 36 hips with AVN and 80 control hips.
- Joint fluid was graded (0-3) based on amount and location.
- Fluid volume was analyzed against patient age and radiographic AVN stage.
Main Results:
- Joint fluid was detected in 84% of normal hips, typically small effusions (grade 0-1).
- Hips with AVN showed significantly higher rates of grade-2 or grade-3 effusions (58% vs 5%, p<0.005).
- Grade-3 effusions were most common in AVN hips with flattened femoral heads (50%).
Conclusions:
- MRI is highly sensitive for detecting hip joint fluid.
- Increased joint fluid is characteristic of avascular necrosis, potentially preceding radiographic changes.
- The degree of joint effusion correlates with the severity of AVN, particularly femoral head flattening.