E5332. The Delicate Balance: Microinstability of The Hip (MIOH)
Authors
Ahmed Taher;
The University of Texas Health Science Center at Houston
Manickam Kumaravel;
The University of Texas Health Science Center at Houston
Serag Attia;
No Affiliation
Vikram Vijayarajan;
The University of Texas Health Science Center at Houston
Rohan Manickam;
The University of Texas Health Science Center at Houston
Background
Microinstability of the hip (MIOH) refers to an uncomfortable excessive movement of the hip beyond its normal range. It occurs due to a combination of structural and functional irregularities that compromise the stability of the joint. These risk factors pertain to the bone structure of the hip joint and the soft tissues surrounding it. Anomalies in the bone structure can be identified through hip assessment measurements. Moreover, the static and dynamic stability of the hip is influenced by soft tissues such as the joint capsule, labrum, ligamentum teres, and adjacent muscles and tendons. Any abnormality or unintended injury to these structures can contribute to the likelihood of developing MIOH. MIOH is a previously unrecognized pathology that necessitates awareness from radiology trainees to diagnose and report it, our main goal in this exhibit is to provide the current general consensus on its key imaging features.
Educational Goals / Teaching Points
1. Define MIOH. 2. Identify causes of MIOH and the associated pathologies. 3. Illustrate the static and dynamic stabilizers of the hip. 4. Discuss the diagnostic criteria with emphasis on history findings and physical examination. 5. Elaborate on major and minor imaging characteristics of MIOH. 6. Provide an animation guide on how to measure the different diagnostic angles (the acetabular index). 7. Demonstration of the proposed diagnostic signs (e.g., cliff, crossover, and coxa profunda).
Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
The diagnosis using hip radiographs relies on various angle measurements and indices. For instance, evaluating dysplasia involves quantifying the Wiberg, Sharp, and Tönnis angles (referred to as the acetabular index). Additionally, indicators like the cliff sign (a break in the circular connection of the lateral femoral head) and the femoral epiphyseal acetabular roof index (measuring the angle between the acetabular roof and the central third of the femoral growth plate) have demonstrated links to MIOH. MRI proves highly valuable in identifying issues related to soft tissues, such as labral pathologies, defects in cartilage, and weaknesses in the capsuloligamentous structures. Additionally, MRI arthrography not only provides a more intricate visualization of cartilage conditions but also enables the evaluation of hip capsule laxity and potential damage caused by medical procedures, which could lead to symptoms of microinstability.
Conclusion
MIOH refers to an uncomfortable excessive movement of the hip beyond its normal physiological range. It occurs due to a combination of structural and functional irregularities that compromise the stability of the joint. These risk factors pertain to the bone structure of the hip joint and the soft tissues surrounding it. Anomalies in the bone structure can be identified through hip assessment measurements. Moreover, the static and dynamic stability of the hip is influenced by soft tissues such as the joint capsule, labrum, ligamentum teres, and adjacent muscles and tendons. Any abnormality or unintended injury to these structures can contribute to the likelihood of developing MIOH.
