The Pelvis and Hip

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The Pelvis and Hip

Femoral neck Pubic rami Sacrum Complex pelvic fractures Avulsion fractures SUFE Perthes' Irritable hip Bone metastases Paget's

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Learning outcomes

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 disruption. 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:

$Subcapital fracture left neck of femur$ $Subcapital fracture$

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:

$Intertrochanteric fracture left femur$ $Intertrochanteric fracture$

Positioning in internal rotation (as the patient's pain will allow) will give a clearer demonstration of the femoral neck:

$Subcapital fracture left neck of femur in external rotation$ $Subcapital fracture in internal rotation$

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:

$Missed subcapital fracture left NOF, right rami fractures - first attendance$ $Missed subcapital fracture left NOF - first attendance$ $Missed subcapital fracture left NOF - 3 weeks later$

Don't forget to scrutinise the lateral as this projection is often overlooked:

$Right intertrochanteric fracture, old fracture inferior pubic ramus$ $Right intertrochanteric fracture$

Clinically a pubic ramus fracture may mimic a femoral neck fracture.

Fractures of the Pubic Rami

Simple falls tend to result in isolated fractures of the pubic rami:

Suspect further complex fractures particularly at the sacrum or iliac wing, with an increase in force, eg, RTAs:

$Fractures of the right pubic rami, fracture right ilium, fracture left sacrum$

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.

Sacral Fractures

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:

Fracture left sacrum, inferior pubic ramus

A fractured L5 transverse process may suggest an occult sacral fracture in the absence of an obvious fracture of the iliac crest:

$L5 transverse process fracture, left ileum fracture$

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:

Anterior compression - outlet projection

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:

$Right acetabular fracture with posterior dislocation, diastasis left SIJ, fracture left pubic rami$

Avulsion Fractures

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):

Avulsion right AIIS with ossification at torn tendon insertion

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.

Perthes' Disease

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:

Perthes'	Femoral Head
Osgood Schlatter's	Tibial tuberosity
Kienböck's Malacia	Lunate
Freiberg's	Metatarsal head
Sinding Larsen	Patella
Scheuermann's	Vertebral epiphysis (apophyseal rings)
Calve's	Vertebral body
Köhler's	Navicular
Sever's	Calcaneum

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.

Irritable Hip

Refers to transient synovitis of the hip joint. The only radiographic evidence may be a joint effusion.

Bone metastases

Primary tumours often metastasise to the pelvis and it is important to search for any moth-eaten, lytic lesions, or areas of sclerosis:

Metastatic lesion left intertrochanteric region

Potential lesions may be an incidental finding on a non-fractured hip, or the femoral fracture may be pathological in origin:

$Pathological fracture through metastatic lesion$ $Pathological fracture through metastatic lesion$

Paget's Disease

The pelvis and proximal femur are often affected. There are three key features:

Bone is expanded.
The cortex is thickened.
The trabeculae is coarse.

TAKE THE PELVIS SELF-TEST

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Norwich Image Interpretation Course

Heidi Nunn (Advanced Practice Reporting Radiographer)