Type:
Educational Exhibit
Keywords:
Trauma, Education and training, Athletic injuries, eLearning, Education, Diagnostic procedure, MR, Musculoskeletal joint, Musculoskeletal bone, Anatomy
Authors:
C. Chong1, J. C. Kandathil2; 1Singapore/SG, 2Tan Tock Seng/SG
DOI:
10.1594/ecr2013/C-1841
Imaging findings OR Procedure details
Procedural Details
A retrospective review of MR wrists done in our institution over a 3 year period was performed and illustrative cases were selected.
Imaging technique,
normal MR appearance,
variant anatomy that mimic TFCC disease and spectrum of imaging findings in TFCC injury are discussed.
Normal TFCC Anatomy
- TFCC is a complex of a fibrocartilaginous disk in association with several ligamentous structures.
Fig. 1
- TFCC stabilises the distal radioulnar joint,
and transmits axial loading from carpus to the ulna.
- TFCC is comprised of the following individual components:
- Triangular fibrocartilage proper Fig. 2
- Dorsal and volar radioulnar ligaments Fig. 5
- Extensor carpi ulnaris tendon shealth
- Ulnar collateral ligament
- Meniscus homologue Fig. 2
- TFC is a biconcave disk.
TFC thickness is directly proportional to the degree of ulnar variance.
- The dorsal and volar radioulnar ligament are broad striated ligament arising from the dorsal and volar cortex of the distal radius sigmoid notch respectively.
The respective ligaments blend with the dorsal and volar surface of the TFC,
and attaches to the ulnar styloid medially and distal radius laterally.
- Extensor carpi ulnaris tendon sheath is normally found within the groove on the dorsum of the ulna in neutral position.
- Ulnar collateral ligament represents thickening of the wrist joint capsule,
and extends from the ulnar styloid process proximally to the triquetrum distally.
- Meniscus homologue is thickening of the ulnar joint capsule,
and is inconsistently present.
It is located distal to the prestyloid recess and attaches to the triquetrum.
MRI Protocol
Positioning
- Wrist neutral at side or overhead while prone.
Technique
- Axial 110 mm
- Coronal FOV 120 mm
- Sagittal FOV 120 mm
- No interslicegap (0mm Skip)
- Matrix 448F x 314P
- Bandwidth 248 Hz per pixel
Standard Sequences
- Coronal gradient : Excellent depiction of TFCC.
Also useful to evaluate intrinsic ligaments and cartilage.
- Cor PD and Sag PD : Help evaluate TFCC and intrinsic ligaments.
- Cor IR : Sensitive to marrow oedema and presence of pathological fluid.
- Axial PD FS : Intrinsic wrist ligaments,
flexor and extensor tendons,
DRUJ,
median and ulnar nerves.
Palmer Classification of TFCC Pathologies
- In 1989,
Palmer proposed a classification system for TFCC lesions.
He classified TFCC lesions as traumatic or degenerative.
- Further subdivision denotes the focus of injury in traumatic lesions and the cumulative derangement of the TFCC in degenerative lesions.
- Palmer classification helps determine the mechanism of injury and direct management.
Class 1 : Traumatic
1A : Central perforation Fig. 6
- Traumatic tears or perforations of the TFC proper.
These 1-2 mm slit tears are located 2-3mm medial to the radial aspect of the TFC.
- As these tears occur in the avascular portion of TFC,
they do not heal and often requires debridement of loose flaps.
1B : Ulnar avulsion with or without distal ulnar fracture Fig. 6
- Avulsion of TFC from its ulnar fovea attachment; these injuries are often associated with injuries to the dorsal and volar radioulnar ligament and may result in radioulnar instability.
1C : Distal avulsion Fig. 7
- Traumatic avulsion of peripheral volar attachments of TFCC,
specifically the ulnolunate or ulnotriquetral ligament.
1D : Radial avulsion with or without sigmoid notch fracture Fig. 8
- Avulsions of the radial attachment of the TFC in the region of sigmoid notch.
- Due to its avascular nature,
these lesions heal poorly and often requires debridement.
Class 2 : Degenerative
2A : TFCC wear Fig. 9
- Degenerative wear or thinning of TFC disc without perforation.
2B : TFCC wear with lunate and/or ulnar chondromalacia Fig. 9
- In addition to TFC thinning,
there is chondromalacia of the lunate,
triquetrum or distal ulna.
2C : TFCC perforation with lunate and/or ulnar chondromalacia Fig. 10
- Perforation of TFC,
often require debridement.
2D : TFCC perforation with lunate and/or ulnar chondromalacia and LT ligament perforation Fig. 11
- Perforation of TFC,
lunotriquetral ligament perforation and chondromalacia.
2E : TFCC perforation with lunate and/or ulnar chondromalacia,
LT ligament perforation,
and ulnocarpal arthritis Fig. 12
- Large TFC perforation,
chondromalacia,
lunotriquetral ligament disruption and concomitant ulnocarpal or radioulnar arthritis.
Treatment includes debridement or arthrodesis.
MRI Artifacts
- Imaging with low spatial resolution and low signal to noise ratio (SNR) reduces sensitivity. Fig. 13
- Chemical shift artifact – due to spatial misregistration of fat and water molecules,
often due to narrow bandwidth.
It occurs at the cartilage bone marrow interface,
and results in misrepresentation of cartilage thickness.
- Magic angle effect – phenomenon related to anisotropy or directionality of collagen fibers,
leading to increased signal intensity within the collagen fibers.
It mimics disease,
such as degenerative changes and partial tears.
- Flow or motion artifact – most common and manifests as ghosting.
It is worst in the phase encoding direction,
due to the increased time interval between phases.
It includes intrinsic physiological motions (heart beats,
blood flow,
arterial pulses) as well as extrinsic motions (patient motions).
- Wraparound artifact – occurs when the imaged object is larger than the FOV or when there is an adjacent object close to the FOV.
In the wrist,
the artifact occurs when the wrist is placed by the patient side.
To avoid this artifact,
choose a phase direction along the minor axis of the object and add presaturation pulses to tissue outside the FOV before excitation pulses.
Most newer machines are able to automatically remove this artifact.
- Partial volume artifact – due to signal averaging over a finite voxel size,
in particular where there is rapid spatial variation.
The solution is to decrease voxel size,
or in other terms,
increase the spatial resolution.
The decrease in SNR can be compensated by increasing the number of excitations.
- Ringing artifact – occurs at interfaces where there is a large and abrupt contrast difference.
It is due to the fixed size of the volume sampling elements in the imaging unit and Fourier series truncation from inadequate high spatial frequency sampling at sharp spatial transition.
The solution is to reduce the size of voxels,
thereby increasing the spatial resolution.
- MR Arthrography artifacts – uncommon,
but is likely related to injection hardware or injectate.
Eg local anaesthesia appearing like muscle edema,
air bubbles within joints.
Potential Pitfalls
- Normal variation in TFCC signal intensities and morphology
- Striation within the triangular ligament and ligamentum subcruentum (space between proximal and distal lamina of the ligament) often demonstrate increased internal signal intensities.
These should not be misinterpreted as tears.
Fig. 14
- TFCC degeneration manifest as increased signal intensities without extension to the articular surface.
It should not be confused with a partial tear. Fig. 14
- Perforation of the TFCC central portion may be found in normal asymptomatic subjects.
Prevalence of perforation increases linearly with age.
- Proximal lamina of the triangular cartilage has relatively high signal intensity,
and should no be misinterpreted as a partial tear.
- The hyaline cartilage at the tip of ulnar styloid process has intermediate signal intensity and should not be misinterpreted as a partial tear of ligamentous attachment.
Fig. 15
- The prestyloid recess is a synovium lined pouch bordered by meniscal homologue distally,
the TFCC attachment to ulnar styloid proximally and central TFCC disk radially.
The recess may appear in different shapes: saccular,
tubular and conical.
Again,
it should not be confused with a tear.
- Supination and pronation of the wrist may result in a thinner appearance of the TFCC.