Imaging of the Pelvis, Hip, and Knee Flashcards
1
Q
Pathology of the hip and pelvis
A
- Trauma
- Metabolic disease: osteoporosis
- Systemic disease
- Nutritional deficiencies
- Neoplasm
- Infection: septic arthritis
- Osteoarthritis
- Operative studies: pre/post op
- Congenital syndromes: developmental dysplasia (DDH)
- Transient synovitis
- Legg Calve Perthes
- Slipped Capital Epiphysis
- Snapping hip syndrome
- Femoroacetabular impingement (FAI)
- Vascular lesions
2
Q
Imaging modalities
A
- X-ray: fracture, dislocation, arthritides
- CT: complex fractures, acetabular fractures, localization of fracture fragments
- MRI: eval soft tissue injuries = labrum, articular cartilage, FAI, avascular necrosis
- MSK US: DDH assessment in neonatal, snapping hip syndrome, effusion assessment, guide needle for aspiration
3
Q
ACR guidelines for the hip and pelvis
A
- Chronic hip pain
- Avascular necrosis
- Stress fractures
4
Q
Diagnostic imaging pathway
A
- Non traumatic hip pain
- Suspected hip fracture
- Avascular necrosis
- Stress fracture
5
Q
Guidelines for the hip and pelvis imaging
A
- Trauma
- Low energy: avulsions, individual bone fracture; AP view or oblique view
- High energy: pelvic ring disruption; high speed CT scan for TAP series
6
Q
Diagnostic pathway for non traumatic hip or knee pain
A
- X-ray of affected joints
- Cause of pain found or cause of pain uncertain
- Further investigation or further investigation will depend on suspicion of a serious underlying disorder
- Further investigation: Mild arthritis -> conservative management; Mod-severe arthritis -> referral to orthopedics
- Suspicion of serious disorder: Fracture -> go to suspected hip fx or traumatic knee pain pathway; Bone metastases -> bone scan; Infection -> septic arthritis (joint aspiration & antibiotics) or osteomyelitis (go to suspected osteomyelitis pathway)
7
Q
Diagnostic pathway for suspected hip fracture
A
- X-ray = fracture seen or no fracture seen
- Fx seen = treat; no fx seen = ongoing suspicion of fx?
- No = stop; Yes = MRI
- If yes other options include Bone scan and/or CT
8
Q
Diagnostic pathway for suspected avascular necrosis (AVN) of hip
A
- X-ray = normal/nonspecific changes or positive for AVN
- Normal = further investigation based on level of suspicion; Pos. for AVN = appropriate treatment
- Level of suspicion = low or higher suspicion
- Low suspicion = stop; Higher suspicion = MRI (preferred) or Bone scan
9
Q
Diagnostic pathway for suspected stress fracture
A
- X-ray = Negative or Positive
- Negative = Early imaging or Delayed imaging; Positive = Treat
- Early imaging = 3 phase bone scan; Delayed imaging = repeat plain x-ray after 1 month
- Bone scan = other options like MRI or CT; Repeat x-ray = appropriate management depending on imaging findings
10
Q
Routine radiologic exam for the pelvis and hip
A
- Pelvis: only one projection; AP view
- Hip: requires 2 projections; AP, Lateral frog leg, and oblique (special)
11
Q
Typical patient position for routine x-ray of the pelvis and hip
A
- Central ray (CR) is perpendicular to the image receptor & directed midway b/w the levels of the anterosuperior iliac spine & symphysis pubis
- LEs are internally rotated 15-20 degrees to place femoral neck plane parallel to the image receptor
12
Q
When does the triradiate cartila and coxal epiphyses fuse
A
- Triradiate Cartel fuse at about 17 years old
- Coxal epiphyses may not fuse until our early 20s
13
Q
Differences between adult male and female pelvis
A
- Male: <90º pubic arch, narrower, less flared, oval or heart shaped inlet
- Female: >90º pubic arch, adapted for childbirth, broader, round pelvic inlet
14
Q
Describe Shenton’s hip line
A
- It should be possible to draw a smooth curve along the medial & superior surface of the obturator foramen to the medial aspect of the femoral neck
15
Q
Describe iliofemoral line
A
- It should be possible to draw a smooth curve along the outer surface of the ilium that extends inferiorly along the femoral neck
16
Q
Describe the femoral neck angle
A
- Normal = 130º
- Alteration of the femoral neck angle can indicate fracture
- Angle is formed by the intersection of a line drawn through the center of the femoral shaft & a line drawn through the center of the femoral neck
17
Q
What is the most common injury of the hip and most common cause of chronic hip pain
A
- Injury: hip fracture
- Chronic pain: hip OA
18
Q
Differences between coxa vara and coxa valga
A
- Coxa Vara = <130º (look like right angle); increased risk of femoral neck Fx & SCFE
- Coxa Valga = >130º (looks like a line); increased risk of dislocation
19
Q
Describe a false positive view and Dunn view
A
- FP view: anterior coverage of the femoral head can be assessed; can diagnose CAM deformity
- Dunn view: evaluates relationship of the femoral head & acetabulum
20
Q
Primar indicates for a CT scan of the hip/pelvis
A
- Severe trauma
- Assessment of alignment & displacement of fracture fragments
- Identification of loose bodies in the joint
- Evaluation of fractures of the acetabulum or sacrum
- Evaluation of bony alignment or accurate measurements of bone geometry
- Evaluation of any condition typically seen by MRI if MRI is contraindicated
21
Q
Describe a femoroacetabular impingement with labral tear
A
- Signs & symptoms: snapping, clicking, limited hip ROM, & painful provocation tests
- Imaging: pelvic/hip x-ray are assessed for osseous alignment & acetabular configuration; MRA is choice for visualizing labral tears
22
Q
Pathological conditions at the hip
A
- DJD (degenerative joint disease)
- RA (rheumatoid arthritis)
- AVN (avascular necrosis)
- Leg Calve Perthes Disease
- Slipped capital femoral epiphysis (SCFE)
- Developmental dysplasia (DDH)
- Femoroacetabular impingement (FAI)
23
Q
X-ray hallmarks of DJD at the hip joint
A
- Joint space narrowing
- Sclerotic subchondral bone
- Osteophyte formation at the joint margins
- Cyst or pseudocyst formation
- Migration of the femoral head
24
Q
Characteristics of RA at the hip
A
- Osteoporosis of periarticular areas
- Symmetrical & concentric joint space narrowing
- Articular erosions, located either centrally or peripherally in the joint
- Synovial cysts located within nearby bone
- Periarticular swelling & joint effusions
- Axial migration of the femoral head
- Acetabular protrusion
25
X-ray findings for AVN/aseptic necrosis
- Initial stages of AVN may appear normal for several wks on x-ray
- Sclerosis & cyst formation at the femoral head, signs of initial necrotic processes, & healing attempts taking place
- Presence of a radiolucent present image, representing the collapse of the necrotic subchondral bone of the femoral head
- In advanced stages the femoral head will collapse or appear flattened
26
What are some causes of aseptic necrosis
- Anemia
- Steroids
- Ethanol
- Pancreatitis
- Trauma
- Idiopathic
- Caisson's disease
27
Describe Caisson's disease
- Decompression sickness
- Condition arising from dissolved nitrous gases coming out of solution into bubbles inside the body on depressurization
- Results in impingement of the blood vessels
28
Describe AVN of the femoral head
- Interruption of blood supply to the femoral head resulting in bone tissue death
- Signs & symptoms: nonspecific dull pain in joint or thigh, limited ROM, and progressive painful limp
- Imaging: MRI is most sensitive for early diagnosis
29
Describe Legg Calve Perthes disease
- Necrosis of the epiphysis of the femoral head (7 y/o)
- Most common between 4-8 yrs
- Permanent deformity: osteoarthritis
- Boys are 5x more likely than girls
- Imaging: MRI is most sensitive for early diagnosis
30
Symptoms of Legg Calve Perthes disease
- Limping
- Pain and stiffness in hip
- Decreased ROM
- Can lead to THA in adulthood
31
Describe slipped capital femoral epiphysis (SCFE)
- Most common adolescent hip disorder
- Weakening of the epiphyseal plate allows for displacement
- Decreased ROM & antalgic gait
- Imaging: lateral frog x-ray best demos the amount of epiphyseal displacement
32
Treatment of a slipped capital femoral epiphysis (SCFE)
- Stable = closed fixation
- Unstable = open fixation
33
Describe developmental dysplasia (DDH)
- A malformation of the hip in young children beginning to walk
- Etiology: genetic, hormonal, & mechanical factors
- Usually affects the left hip, more prominent in girls, & has a familial tendency
- Risk factors include firstborn children & children born in a breech position
34
Stable versus unstable pelvis fractures
- Unstable = ≥2 articulation sites on the pelvic ring are disrupted
- Stable ischiopublic ramus fractures comprise half of all pelvic fractures
35
Describe acetabular fractures and proximal femoral fractures
Acetabular Fx: most common at the posterior column/rim of the cup; associated with femoral head impaction or posterior dislocation
- Proximal femoral Fx: intracapsular often complicated by vascular disruption = AVN; extracapsular = vascular complication is rare
36
Describe the importance of clinical exam to detect fracture
- In stable/alert trauma patient, a thorough clinical examination will detect pelvic fractures with nearly 100% sensitivity
37
Clinical exam to detect fracture in the hip/pelvis
- All must be present = initial radiograph unnecessary
- Age >3 yrs
- No impairment of consciousness
- No other major distracting injuries
- No complaint of pelvic pain
- No signs of fracture on inspection
- Painless compression of iliac or pubic symphysis
- Pain free hip rotation & flexion
38
Stable pelvic fractures include
- Avulsion fractures of the ASIS, AIIS, or ischial tuberosity
- Iliac wing fracture
- Sacral fractures
- Ischiopubic ramus fracture
39
Widening of the pubic symphysis greater than _____ is considered abnormal
- greater than 1 cm is considered abnormal
40
Signs and symptoms of a pubic ramus stress fracture
- History of overuse
- Relief with non-weight bearing
- Insidious in nature
- Local pain, tenderness, swelling
- Typical site in the pelvis is the pubic ramus
- Bone scan is diagnostic early
41
Describe an acetabulum fracture
- Anterior column fractures
- Posterior column fractures: most common, hip precautions
- Protected weight bearing
42
Describe a femoral neck stress fracture
- Signs & symptoms: gradually worsening pain in back, hip, or groin related to weight bearing activities, pain at extremes of passive external & internal rotation
- MOI: fatigue stress fractures may develop in runners & military trainees owing to increased duration, frequency, & intensity of weight bearing activities imposed on normal bone; Insufficiency stress fractures may develop in the osteoporotic elderly female or females with the female athlete triad (disordered eating, menstrual dysfunction, premature osteoporosis)
- Imaging: MRI is most sensitive & performed if immediate diagnosis ir required
43
Red flags for colon cancer
- Age >50 yrs
- Bowel disturbances
- Unexplained weight loss
- Hx of colon cancer in immediate family
- Pain unchanged by positions or movement
- Possible tenderness to palpation of abdomen in area of colon
44
Red flags for pathologic fracture of the femoral neck
- Older women (>70 yrs) with hip, groin, or thigh pain
- Hx of a fall from standing position
- Severe constant pain, worse with movement
- Shortened & externally rotated LE
45
Red flags for osteonecrosis of the femoral head (aka AVN)
- Hx of long term corticosteroid use
- Hx of osteonecrosis of the contralateral hip
- Trauma
- Gradual onset of pain, may refer to groin, thigh, or medial knee that is worse with weight bearing
- Stiff hip joint, primarily limited in IR & flexion
46
Red flags for Legg Calve Perthes disease
- 5-8 yrs boys with grain/thigh pain
- Antalgic gait
- Pain complaints aggravated with hip movement especially hip ABD & IR
47
Red flags for slipped capital femoral epiphysis (SCPE)
- Overweight adolescent
- Hx of a recent growth spurt or trauma
- Aching in groin exacerbated with weight bearing
- Involved leg held in ER
- ROM limited in hip IR
