The following presentation was given at the Radiological Society of North
America (RSNA) in 2012
metalions@ucl.ac.uk
Multimodality Assessment of Metal-onMetal Hip Arthroplasties
Never Miss a Diagnosis Again on Plain Radiographs, MARS MRI and SPECT-CT
Sabah, S. A., Satchithananda, K., Henckel, J., Mitchell, A. W., Barwick, T., Khan, S.,
Eccles, A., Hirschmann, M., Hart, A. J.
1
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Disclosures
• Dr. K. Satchithananda
– Johnson & Johnson Committee Member
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Overview
• Introduction to metal-onmetal hip arthroplasty
• Assessment of unexplained
hip pain
• Imaging modalities
– Plain radiographs
– MARS MRI
– SPECT-CT
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Metal-on-metal hip arthroplasty
• First popular design
introduced by McKee in 1951
• Failure through aseptic
loosening due to high torque
• Superseded by Charnley lowfriction arthroplasty
http://global.smith-nephew.com/us/BHR_IF_GEORGE_KENETH_MCKE_15656.htm
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
MOM Resurgence
• Sold as hip replacements to
last a lifetime
• Promise of:
– Low component wear rate
– Femoral bone conservation
– Low rate of dislocation
• Approaching 1 million MOM
hips implanted in US over
past decade
National Joint Registry for England and Wales
9th Annual Report
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
MOM Controversy
• Higher failure rates compared to traditional hip types
National Joint Registry for England and Wales - 9th Annual Report
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
MOM Controversy
• Withdrawal of DePuy ASR prosthesis
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
MOM Controversy
• Concern over soft tissue lesions and raised metal ions
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Reasons for revision
• Pain
• Aseptic loosening
• Infection
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Unexplained hip pain
Henderson. JBJS(Br) 2012. 94(B):145-51
MHRA Device Bulletin. MDA/2012/036
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Plain Radiographs
Hip resurfacing
Total Hip Prosthesis
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Component Orientation
• Acetabular inclination
Murray, DW. JBJS(Br). 1993; 75-B:228-32. Hart, AJ. Hip Int. 2009; 19:323-9
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Malposition
• Raised inclination (‘Vertical cup’)
Malposition
• Anteverted femoral stem (retroverted femoral component)
Malposition
• Retroverted acetabular component
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Impingement
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Periprosthetic fracture
• Femoral neck fracture
Aseptic loosening
• Femoral component
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Aseptic loosening
• Gross acetabular loosening
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Dislocation
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Stem Fracture
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Trochanteric resorption
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Metal-artifact reduction sequence MRI
• Artifact reduction techniques
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Metal-artifact reduction sequence MRI
• Reporting protocol
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Metal-artifact reduction sequence MRI
• Imperial Classification
Lesion
category
Wall
Contents
Shape
Thin walled
Fluid like:
T1 hypo / T2
hyper
Flat with
walls mainly
in apposition
Class 2A
Thick walled
or irregular
Fluid like:
T1 hypo / T2
hyper
Not flat and
>50% of the
walls are not
in apposition
Class 2B
Thick walled
or irregular
Atypical fluid:
T1 hyper / T2
variable
Any size
Class 3
Solid
Mixed signal
Any size
Class 1
Hart, AJ. JBJS(Am). 2012; 94(4):317-325
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Pseudotumors
• Imperial Type 1 Pseudotumor
Cor STIR
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Pseudotumors
• Imperial Type 2A Pseudotumor
Ax T2W
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Pseudotumors
• Imperial Type 2B Pseudotumor
Ax T2W
Ax T1W
Ax T2W
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Pseudotumors
• Imperial Type 3 Pseudotumor
Ax T1W
Cor T1W
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Pseudotumors
• Infected Pseudotumor
Ax T2W
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Metal-artifact reduction sequence MRI
• Anderson Classification
Anderson, H. Skeletal Radiol. 2011. 40:303-307
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Periprosthetic hip musculature
• Grading
– Assessed on T1W images
– Compared to contralateral side
Grade
Comment
0
Normal
1
≤30% decrease in muscle size
2
30-70% fatty change with decrease in muscle mass
3
>70% fatty change with an 80% decrease in size
Bal, BS. Instr Course Lec. 2008. 56:223-230.
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Periprosthetic hip musculature
• Abductor anatomy
Minimus
Medius
Maximus
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Tendinopathy
• Pfirrmann system to assess:
– Tendon signal
– Tendon diameter
– Tendon ossification
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
Tendinopathy
• Abductor tendon avulsion due to soft tissue lesion
Ax T1W TSE P2
Cor STIR
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
SPECT-CT
• Hybrid imaging modality
+
=
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
SPECT-CT
• Uses of SPECT-CT
– Occult infection
– Aseptic loosening
– Mechanical symptoms
– Localisation of pathology to the hip
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
SPECT-CT
• Infection
– Best seen on early blood
pool images
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
SPECT-CT
• Femoral head loosening
– ‘Hotspot’ under component
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
SPECT-CT
• Stem loosening
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
SPECT-CT
• Mechanical Symptoms
– Eccentric femoral stem
– ‘Hotspot’ at tip
Introduction | Plain Radiographs | MARS MRI | SPECT-CT
SPECT-CT
• Incidental pathologies
L5/S1 disc pathology accounted for unexplained ‘hip’
pain in this patient
Summary
• Multimodality assessment permits diagnosis of unexplained
hip pain
• We recommend post-op surveillance with plain radiographs
and MARS MRI
• SPECT-CT for occult infection, aseptic loosening, mechanical
symptoms and to localize pathology to hip