Definition
The acetabular teardrop is a radiographic landmark seen on the AP pelvis. It represents the superimposition of structures around the medial acetabular wall and cotyloid fossa.
Components
The teardrop is formed by overlapping lines from the anterior and posterior aspects of the acetabulum. Its lateral limb relates to the acetabular wall and cotyloid fossa, while the inferior portion relates to the acetabular notch and superior obturator region.
Clinical relevance
The teardrop is useful when assessing:
- acetabular position and depth
- hip dysplasia
- protrusio acetabuli
- acetabular fractures
- cup position and medialisation during total hip arthroplasty
Köhler line
Köhler's line, or the ilioischial line, is a separate medial pelvic landmark. Medial migration of the femoral head or acetabular component beyond this line supports protrusio or excessive medialisation.
Interpretation
Always compare both sides on a properly positioned AP pelvis because pelvic rotation can alter the apparent shape and position of the teardrop.
References
- Orthobullets. Adult Pelvis Radiographs.