A PSIS, or Posterior Superior Iliac Spine, is a bony prominence located on the posterior (back) aspect of the iliac bone of the pelvis. It's a commonly used anatomical landmark, particularly in medical settings.
Here's a breakdown of its significance:
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Anatomical Location: The PSIS is found at the very back of the pelvis, specifically on the iliac crest (the upper border of the ilium). You can often feel it as a small bump or indentation just below your waistline on either side of your spine.
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Clinical Relevance: The PSIS serves as an important reference point for several medical procedures and assessments, including:
- Reference Frame Placement: As the provided reference indicates, the PSIS is frequently used as a site for placing reference frames during surgeries, particularly spinal surgeries. This is because it is located away from the surgical site and allows for secure fixation.
- Anatomical Landmark: Identifying the PSIS is crucial for palpating other anatomical structures in the lower back and pelvis.
- Sacroiliac Joint Assessment: It's used to assess the position and movement of the sacroiliac joint (SIJ), which connects the sacrum (the base of the spine) to the ilium.
- Posture Analysis: The PSIS is used in postural assessments to identify imbalances or asymmetries in the pelvis.
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Importance in Surgery: In surgical settings requiring precise navigation, the PSIS can act as a stable anchor point. Surgeons rely on accurately locating the PSIS to correctly position surgical instruments and navigate the surgical field, especially when using computer-assisted surgery or navigation systems.
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Palpation: The PSIS is typically palpable (able to be felt through the skin), making it a readily accessible landmark for clinicians. This ease of palpation contributes to its widespread use in clinical practice.
In summary, the PSIS is a key anatomical landmark on the pelvis that is clinically relevant for various medical assessments and procedures, especially those requiring precise anatomical reference.
