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Metal Artifact Reduction MRI of Total Ankle Arthroplasty

C Cesar Netto MD; L Fonseca MD; E Dein MD; H Zhang MD; T Zahoor MD L Schon MD; J Fritz MD.

Medstar Union Memorial HospitalJohns Hopkins University

Baltimore, MD

Disclosures

• This research project was supported by SiemensHealthcare, USA.

• Our disclosures are listed in the AOFAS Mobile App.– Lew Schon– Jan Fritz

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Total Ankle Arthroplasty (TAA)Monitoring

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• Rising number of Total Ankle arthroplasty (TAA)procedures.

• Increasing number of symptomatic patients and possiblesurgical revisions may require a more accurate pre-operative evaluation of periprosthetic bone and soft tissues.

TAA Imaging-Challenges andThe role of the MRI

• Radiography is often effective for imaging of TAA, but cannot visualize soft tissues and bone-implant interfaces.

• MRI provides excellent visualization of soft tissues, but metal implant induced artifacts cause image distortion, signal displacement and failure of fat saturation.

• Traditional high-bandwidth (high-BW) metal artifact reduction sequence (MARS) MRI lessens metal artifacts, but substantial image distortions remain, specifically with Cobalt-Chromium implants.

• Slice-Encoding-Metal-Artifact-Correction (SEMAC) is a recently FDA-approved, advanced MARS technique that promises more powerful metal suppression and improved visualization of the bone-implant interfaces and periprosthetic soft tissue 4

Study Objectives

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We prospectively tested the hypothesisthat SEMAC MARS MRI facilitates bettermetal reduction and visibility of boneimplant-interfaces and periprostheticstructures than does traditional MARSMRI in patients with TAA.

Methods

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• IRB-approved, prospective study.

• Total of 20 volunteers with TAA included, 10 females/10 males, meanage 59 (41-73) years, 15 (3-24) months post-operatively.

• All patients underwent in the same session (1.5 Tesla MRI scanner) :– high-BW MARS MRI (25 min)– SEMAC MARS MRI (25 min)

• For each technique, intermediate-weighted and fat-suppressed MRimages were obtained in axial, sagittal and coronal orientation.

• Three board certified observers evaluated the high-BW and SEMAC MRimages in an independent, random and blinded fashion.

Methods

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• A total of 112 different parameters were graded in a 5-point Likert scale (1=non-diagnostic, 5=very good) andincluded:– Patient motion– Image quality– Quality of metal suppression– Visibility of bone-metal interfaces– Visibility of tendons– Visibility of ligaments– Visibility of bone– Visibility of joints

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LateralPosterior

AnteriorMedial

Tibial Component

1 23 4

5

6 78

9 10

11 1213

1415

Talar Component

12 3

4 5

6 7 89 10

11 12 1314

15

Anterior

Lateral

Medial

Posterior

MethodsBone-Implant Interface Quadrants

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3 45

1 23

4 5

Results: Bone-Implant Interface and Soft Tissues

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SE

MA

C M

AR

S M

RI

Hig

h-B

W M

AR

S M

RI

High-BW MARS MRI SEMAC MARS MRI

SE

MA

C M

AR

S M

RI

Hig

h-B

W M

AR

S M

RI

• Better visibility of soft-tissues atthe level of the implants onSEMAC images, including:

• Peroneal tendons• Medial long flexor tendons

• Better visibility of tibial, fibular and talar bone-implant interfaces andperiprosthetic bone on intermediate-weighted and fat-suppressedSEMAC images, when compared to High-BW.

ResultsImage Quality

10

Fibular Plate Talar Component

P<0.0001

5

4

3

2

1

Tibial Component

P<0.0001 P<0.0001

Like

rt S

core

s

P<0.0001

SEMAC

High-BW

1 2 3

1 2 3

4 5 6

4 5 6

7 8 910

11

12

13

14

15

7 8 9 10

11

12

13

14

15

5

4

3

2

1

Like

rt S

core

s

P<0.0001

5

4

3

2

1

SEMAC

High-BW

1 2 3

1 2 3

4 5 6

4 5 6

7 8 910

11

12

13

14

15

7 8 9 10

11

12

13

14

15

Like

rt S

core

s

Flui

d Br

ight

ness

Fat S

uppr

essi

on -

STIR

Shar

pnes

s –

PD n

on-fa

t-sat

Tiss

ue C

ontra

st –

PD n

on-fa

t-sat

Shar

pnes

s –

STIR

fat-s

at

5

4

3

P=0.0234 P<0.0001 P<0.0001 P<0.0001 P=1.0

2

1Like

rt S

core

s

Metal Artifact Reduction

Image Quality

Bone-Implant Interface – Tibial Component

Bone-Implant Interface – Talar Component

ResultsInter-observer Agreement andSoft-tissue Visibility

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LIGAMENTS

SEMAC High-BW P-Value

Deltoid deep 5 4 0.055

Deltoid superficial 5 5 0.74

Spring plantar 5 5 0.80

Spring Superomedial 5 5 0.50

Tib-Fib Anteroinferior 4 3 <0.0001

Tib-Fib Posteroinferior 4.5 3 <0.0001

ATFL 5 3 <0.0001

CFL 4 4 0.0030

PTFL 5 3 <0.0001

PERONEALS TENDONS

Brevis Above Implants 5 5 0.14

Brevis at level of Implants 5 3 <0.001

Brevis bellow Implants 5 4 0.03

Longus Above Implants 5 5 0.43

Longus at level of Implants 5 3 <0.001

Longus bellow Implants 5 5 0.12

FLEXOR TENDONS

SEMAC High-BW P-Value

PTT Above Implants 5 5 0.19

PTT at level of Implants 5 5 <0.001

PTT bellow Implants 5 5 0.66

FDL Above Implants 5 5 0.08

FDL at level of Implants 5 3 <0.001

FDL bellow Implants 5 5 0.03

FHL Above Implants 5 5 0.08

FHL at level of Implants 5 4 <0.001

FHL bellow Implants 5 5 0.15

EXTENSOR TENDONS

ATT Above Implants 5 5 0.01

ATT at level of Implants 5 4 0.66

ATT bellow Implants 5 5 0.80

EDL Above Implants 5 5 0.006

EDL at level of Implants 4.5 5 0.42

EDL bellow Implants 4 4 0.053

EHL Above Implants 5 5 0.01

EHL at level of Implants 4.5 4.5 0.93

EHL bellow Implants 4 4 0.07

INTER-OBSERVER AGREEMENT INTRACLASS CORRELATION COEFFICIENT

(ICC)

ICC

95% Confide

nce Interval

All Parameters 0.7920 0.7827-0.8010

Tibial ComponentBone-Implant

Interface0.8399 0.8192-

0.8589

Talar ComponentBone-Implant

Interface0.8540 0.8349-

0.8715

Conclusion

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• The use of SEMAC MARS MRI, in the evaluation of aTAA, outperforms traditional high-BW MARS MRI in:– Degree of metal artifact reduction.– Visibility of bone-implant interfaces.– Visibility of periprosthetic tendons and ligaments

around the level of the implant.

• Advanced MARS MRI technique can be a valuableclinical tool to assess osseous integration and softtissue lesions in patients following TAA.

References

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