The Pelvis and Hip
- Assess skeletal radiographs using a systematic approach
- Describe pelvic and femoral anatomy
- Understand mechanisms of injury and the likely fractures/dislocations which may result
- Search for subtle injuries and understand their clinical significance
- Accurately describe dislocations and associated fractures
- Understand common eponyms
- Recognise potential ligament injuries
- Understand paediatric anatomy and common paediatric injuries
- Recognise common pathological conditions seen around the pelvis and femora
Femoral Neck Fractures
- Femoral neck fractures may be subtle. Assess the subcapital, transcervical and intertrochanteric regions. Subcapital and transcervical fractures are intracapsular and may be at risk of avascular necrosis.
- Look carefully:
At the bony cortices, for any evidence of a subtle break or buckle.
At the trabecular pattern for any distuption. The prominence of the trabecular pattern varies between patients.
For sclerosis; this is evidence of impaction.
- Subcapital fractures are most common. May be impacted or displaced, complete or incomplete. Clinically, the patient's leg is usually shortened and externally rotated:
- Intertrochanteric fractures generally occur in an older age group than subcapital. May be 2,3 or 4 part, depending on involvement of greater and lesser trochanters. Clinically there tends to be less displacement (shortening and rotation) of the patient's leg, therefore there is often less suspicion of a fracture:
- Positioning in internal rotation (as the patient's pain will allow) will give a clearer demonstration of the femoral neck:
- An undisplaced fracture may be subtle on the initial radiograph. Repeat x-rays may be taken a couple of days later, or an MRI/isotope scan may be required:
- Don't forget to scrutinise the lateral as this projection is often overlooked:
- Clinically a pubic ramus fracture may mimic a femoral neck fracture.
Pubic Rami Fractures
- Simple falls tend to result in isolated rami fractures:
- Suspect further complex fractures particularly at the sacrum or iliac wing, with an increase in force, eg, RTAs:
- The symphysis pubis width may be up to 10mm in children, but should be no more than 5mm in adults. Increased width (diastasis) indicates disruption:
- The superior cortices of the superior pubic rami should align. Superior displacement suggests disruption:
- The ischial-pubic synchondrosis (cartilaginous junction) may present as irregular and asymmetric during development (up to 12-13 years). May be mistaken for healing fractures or lesions.
- The sacrum is often obscured by bowel gas, and should be carefully scrutinised.
- The sacral foramina should be checked for disruption. The upper 3 arcuate lines (which form the edge of the sacral foramina) should be traced. Compare one side with the other; the lines should be smooth and unbroken. Asymmetry indicates significant injury to the sacrum:
- A fractured L5 transverse process may suggest an occult sacral fracture in the absence of an obvious fracture of the iliac crest:
- The SI joints are normally wide in adolescents but should be only 2-4mm in adults. An increase suggests disruption:
Complex Pelvic Fractures
- As the pelvis is a bony ring, a fracture at one point is likely to be accompanied by a second fracture. The second injury may be a widened SI joint or symphysis pubis.
- A double break in the pelvic ring is regarded as an unstable injury.
- Complex pelvic fractures are described by the direction of impact:
An anterior compression force results in disruption of the SI joints (>4mm), diastasis of the symphysis pubis (>5mm) and external rotation of the hemipelvis. Also known as an "open book" injury:
A lateral compression force results in oblique fractures of the pubic rami bilaterally (with overlapping fragments), impacted fractures of the sacral foramina ipsilateral to the force, with infolding of the hemipelvis:
A vertical shearing injury results in vertical, unilateral fractures of the pubic rami, vertical fracture of the sacral foramina on the same side (or fractured ileum paralleling SI joint/disruption of the SI joint) with the hemipelvis usually displaced superiorly:
A straddle injury refers to a force against the perineum. This results in fractures of all pubic rami bilaterally with the central fragment displaced superiorly.
- Acetabulum fractures - Associated with dislocations (usually posterior), but the retained fragments post-reduction may be subtle. Carefully scrutinise the joint for evidence of bony fragments. Clincially, posterior dislocations are evident by internal rotation and adduction of the femur:
- Five apophyses appear by puberty, fusing by the age of 25. An apophysis is a secondary ossification centre that contributes to the growth of the bone, but is not related to a joint. These have strong muscle attachments, and may avulse during exercise.
Crest of ileum (Quadratus lumborum)
Anterior superior iliac spine (Sartorius):
Anterior inferior iliac spine (Rectus femoris):
Ischial tuberosity (Hamstrings):
Lesser trochanter (Iliopsoas):
Slipped Upper Femoral Epiphysis (SUFE)
- Important to diagnose but easily missed.
- Presents typically in overweight children (more often boys), aged over 8 years.
- Look for a widened physeal growth plate.
- The frog lateral often demonstrates the medial slip better than the AP:
- A line drawn along the lateral femoral neck should intersect a portion of femoral epiphysis. If it doesn't, this is evidence of a medial slip (Salter-Harris I):
- Can be bilateral. Occurs due to minor trauma.
- Refers to Osteochondritis of the femoral head.
- Presents typically in children (more often boys) aged under 8 years.
- The femoral head characteristically becomes sclerotic and flattened due to avascular necrosis:
- Osteochondritis includes a number of pathologies given specific names based on their location:
||Vertebral epiphysis (apophyseal rings)
- Within these locations, there are similar appearances to Perthes': patchy sclerosis, collapse and flattening of the articular surface with subsequent fragmentation.
- It is thought that in most cases the appearance is due to repetitive micro-trauma, leading to the AVN.
- Refers to transient synovitis of the hip joint. The only radiographic evidence may be a joint effusion.
- Primary tumours often metastasise to the pelvis and it is important to search for any moth-eaten, lytic lesions, or areas of sclerosis:
- Potential lesions may be an incidental finding on a non-fractured hip, or the femoral fracture may be pathological in origin:
- The pelvis and proximal femur are often affected. There are three key features:
Bone is expanded.
The cortex is thickened.
The trabeculae is coarse.
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