Pelvis, hip & SI joints

Pelvis, hip, and SI joints

Exam category: Procedures → Head, Spine and Pelvis
Why it matters: This is where the spine's projection logic meets a patient who may have a fractured hip. The registry tests two things hard here: the trauma-safe alternatives for the hip — because the routine lateral requires exactly the movement a femoral-neck fracture can't tolerate — and a cluster of central-ray angles (sacrum, coccyx, SI joints) that are easy to confuse because several of them share a centering point.

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Overview

Vertebral column worked down the spine to the lumbar region. This module takes what sits below and behind it: the sacrum and coccyx, the sacroiliac joints, and the pelvis and hip. The angles matter more than anywhere else in the body — the sacrum, coccyx and SI joints all get axial projections whose CR angle is the whole projection, and two of them center to the same point in opposite directions. And the hip is a trauma decision: the standard lateral requires abduction, so knowing which alternative to reach for is the tested skill.

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1. Hip and pelvis — the trauma-safe pattern

Frog-leg, Danelius-Miller and Clements-Nakayama are used in a fixed order: each is the answer only when the movement the previous one requires is impossible. Frog-leg is the non-trauma lateral, and it is the one a hip fracture cannot tolerate — the same logic as Neer for the trauma shoulder. So trauma steps down to the Danelius-Miller cross-table axiolateral, which needs no movement of the injured side but does need the other leg lifted clear. When even that is impossible — bilateral injury, or a post-arthroplasty patient with limited movement in both limbs — you step down again to Clements-Nakayama, which leaves both legs extended and buys the same view by angling instead: the IR is tilted 15° and the CR angled 15° posteriorly, perpendicular to the femoral neck, the angle compensating for the leg it cannot internally rotate.