Imaging the Pelvis and Hip

Systematic pelvis and hip imaging encompasses a broad spectrum of pathology from acute trauma (NOF fracture, acetabular fracture, pelvic ring disruption) to chronic conditions (OA, AVN, FAI, DDH). The AP pelvis radiograph is the essential first-line investigation, with advanced imaging selected based on the clinical question.

The most important clinical scenario is the elderly patient with hip pain after a fall and normal radiographs — this requires urgent MRI to exclude an occult NOF fracture. Delayed diagnosis is one of the most common causes of medicolegal claims in orthopaedic practice.

Systematic Pelvis and Hip Imaging Assessment

When the AP pelvis is normal or near-normal but the patient has significant hip pain, the differential is the highest-yield part of this topic. Distinguishing these entities is almost entirely an MRI exercise, because the discriminating features are in the bone marrow and soft tissue.

Pelvis and hip imaging pathways are broadly concordant worldwide, but the named guidelines, resource availability and registry context differ. The AP pelvis radiograph is the universal first-line study; the principal global divergence is in how quickly and how often advanced imaging (MRI/CT) is added.

Global epidemiology

Hip fracture is the dominant high-volume indication. There are an estimated 1.5 million-plus hip fractures per year worldwide, projected to rise sharply with population ageing, with the largest absolute increase expected in Asia. Around 5-10% of fractures that ultimately require surgery are not seen on the initial radiograph, and meta-analysis data show that among elderly patients imaged for clinical suspicion with negative/equivocal films the occult-fracture rate is far higher (about 39%). Non-traumatic AVN of the femoral head presents most often in the 30-50 age group and is bilateral in roughly half to four-fifths of non-traumatic cases. Developmental dysplasia of the hip (DDH) affects roughly 1-3 per 1000 live births for frank dislocation, with higher rates of sonographic dysplasia.

Side-by-side guideline comparison

Registry and outcome context

National hip fracture registries and audits (e.g. the UK National Hip Fracture Database, and equivalents in Australia/New Zealand, the Nordic countries and elsewhere) tie prompt, accurate imaging diagnosis to time-to-surgery targets, because delayed diagnosis of an occult fracture delays surgery and worsens outcome. Arthroplasty registries (NJR, AJRR, AOANJRR, SHAR/Swedish, Norwegian, NZJR) capture downstream implant survival for the hemiarthroplasty and total hip replacements that displaced NOF fractures and end-stage AVN ultimately require.

High- versus limited-resource practice variation

In well-resourced systems 24-hour MRI for occult fracture, MR arthrography for labral pathology, and CT with 3D reconstruction for acetabular/ring planning are routine. Where MRI access is constrained, CT (sensitivity around 79% for occult fracture) is the accepted substitute, repeat/delayed radiographs and bone scanning are used, and ultrasonography has an expanding bedside role — for DDH screening, for hip effusion, and as a high-accuracy adjunct for occult femoral neck fracture where MRI is unavailable. DDH screening strategy itself varies globally between universal sonographic screening (common in parts of continental Europe) and selective screening of at-risk infants (breech, family history, clinical instability), with radiography reserved for after the femoral head ossifies (around 4-6 months).