MRI Fingers Including the Thumb – Generic Standard Protocol

1. Executive Summary

Finger MRI represents the most technically demanding examination in the MSK upper extremity protocol series. The diagnostic structures of interest — the collateral ligaments (1–2 mm wide), the volar plate (< 1 mm at its thinnest), the annular pulleys (A2 pulley approximately 0.5–1 mm thick), the flexor digitorum profundus and superficialis tendons (3–5 mm diameter in their digital sheaths), and the articular cartilage of the PIP and DIP joints (< 1 mm) — are an order of magnitude smaller than those of the shoulder or knee. MRI of the finger requires spatial resolution approaching that of dedicated extremity imaging systems and demands a technically optimised protocol that would be described as a dedicated research acquisition for any other body region.

This protocol covers the individual fingers (index, middle, ring, and little finger) and the thumb, from the level of the proximal phalanx base to the distal phalanx. The metacarpal level and the MCP joint are covered by the MRI Hand protocol; this page focuses on the phalangeal and interphalangeal anatomy that requires individual digit-specific imaging planes and the highest spatial resolution in the upper extremity protocol series.

The fundamental principle of the finger MRI protocol is that each finger must be imaged individually — with the imaging planes prescribed relative to the specific axis of that individual finger, not relative to the hand or body axes. Even adjacent fingers lie at slightly different angles to the magnet axis, and using a common prescription across multiple fingers produces non-diagnostic partial-volume averaging through the ligamentous structures.

1.1 Core Strengths

Flexor pulley system assessment is the primary indication for finger MRI in sports medicine and hand surgery. The annular pulleys — particularly A2 (at the proximal phalanx), A3 (at the PIP joint), and A4 (at the middle phalanx) — are the primary dynamic stabilisers of the flexor tendon, and their rupture in climbers and athletes produces the characteristic "bowstringing" deformity. MRI at 3T with dedicated coil demonstrates the annular pulley system with sufficient resolution for grading complete vs. partial ruptures and for identifying which specific pulleys are involved [3, 4].

PIP and DIP joint ligamentous assessment: the proper and accessory collateral ligaments of the PIP joint, the volar plate, and the extensor mechanism (central slip and lateral bands) are all demonstrable on 3T finger MRI. Proper collateral ligament tears are displayed on coronal sequences; volar plate tears on sagittal sequences; central slip tears on sagittal and axial sequences [2, 5].

Flexor tendon integrity: flexor digitorum profundus and superficialis tendon partial and complete tears within the digital sheath are assessed on axial and sagittal sequences. Zones of tendon injury (Bell-stage grading system; Klein classification) are mapped pre-operatively to guide repair approach.

Phalangeal bone marrow pathology: stress fractures of the phalanges, osteoid osteoma (a primary indication in young adults with nocturnal phalangeal pain), bone marrow oedema from post-traumatic contusion, early septic arthritis, and enchondroma are uniquely characterised on MRI.

Glomus tumour: glomus tumour of the fingertip subungual region is the primary indication where MRI — even on a standard 3T system with a hand/wrist coil — provides the definitive pre-operative localisation. The characteristic T2-bright, enhancing subungual nodule (typically 2–5 mm) is reliably demonstrated on dedicated high-resolution finger sequences.

Superior to ultrasound for: bone marrow changes (phalangeal), deep intra-articular pathology, and complete structural assessment of all ligament layers simultaneously. Ultrasound excels for dynamic assessment and superficial structures; MRI provides the complete structural map.

1.2 Intrinsic Limitations of the Generic Protocol

Resolution at the pulley and volar plate level: the A2 pulley at 3T with standard hand/wrist coil (FOV 6–8 cm, target resolution 0.2–0.3 mm) is at the detection threshold of clinical diagnostic imaging. Partial pulley tears — particularly of the volar A2 aspect — may not be detectable at the resolution achievable in routine clinical practice without a dedicated single-finger coil. The generic protocol with a standard hand/wrist coil provides reliable assessment of complete pulley tears and significant partial tears; subtle partial tears require a dedicated single-element cylindrical finger coil or 7T research system for reliable detection.

Articular cartilage grading: PIP and DIP joint cartilage is 0.5–1.0 mm thick. Even at the highest clinical MRI resolution (0.2–0.3 mm in-plane at 3T), reliable grading of focal chondral defects requires dedicated 3D isotropic sequences and knowledge of the normal cartilage signal variation at this resolution.

Multi-finger assessment: this protocol is designed for a single digit or at most two adjacent digits. Multi-finger assessment — as in polyarticular inflammatory arthropathy involving all PIP joints — is better addressed by the MRI Hand protocol with a wider FOV or by a combined hand-wrist inflammatory protocol.

Motion sensitivity: the finger is a small structure on a long lever arm from the patient body; any involuntary hand movement is amplified at the fingertip. At the high spatial resolution required for finger MRI, even sub-millimetre motion between acquisitions degrades image quality disproportionately.

When dedicated child protocols are required: MR arthrography for partial collateral ligament tears and volar plate stability assessment; dedicated dynamic pulley assessment in the flexed position; glomus tumour dedicated high-resolution protocol; inflammatory PIP/DIP joint protocol with post-contrast RAMRIS scoring.

2. Main Clinical Indications

2.1 Standard Indications

Flexor pulley rupture in climbers and athletes is the most common sports medicine indication for finger MRI. Rock climbers are particularly susceptible to A2 and A3 pulley ruptures due to the crimp grip position. MRI characterises the degree of injury (partial vs. complete, single vs. multi-pulley), identifies the bowstringing gap, and assesses for associated injuries (volar plate, collateral ligament). The generic protocol at 3T with a dedicated hand/wrist coil is sufficient for the large majority of clinically important pulley injuries.

PIP joint collateral ligament tears occur after forced radial or ulnar deviation of the finger. The proper and accessory collateral ligaments of the PIP joint are assessed on coronal sequences. MRI determines tear grade (sprain, partial, complete), guides decision between conservative (splinting) and surgical (repair or reconstruction) management. For the clinician, the critical question is whether the MCP or PIP collateral is the dominant injury site and whether the volar plate is involved.

Volar plate injuries of the PIP joint: PIP joint hyperextension injuries produce a spectrum from volar plate sprain to complete avulsion with joint instability. The volar plate is best assessed on sagittal sequences. MRI is indicated when instability is clinically suspected or when plain radiographs are normal but functional limitation persists.

Central slip rupture and Boutonnière deformity: acute central slip rupture at the PIP joint produces the classic Boutonnière deformity (PIP flexion, DIP hyperextension) when the lateral bands migrate volarly. MRI demonstrates the central slip discontinuity, lateral band migration, and the status of the triangular ligament. This is a surgically important diagnosis where MRI guides decision-making.

Jersey finger (FDP avulsion): avulsion of the flexor digitorum profundus at its DIP joint insertion after forced extension of a flexed finger (classically ring finger in rugby). MRI identifies the degree of retraction (Leddy classification), the presence of a bony fragment, and the integrity of the vascular supply to the tendon — all of which determine surgical urgency and approach. This is one of the clearest acute surgical indications for finger MRI.

Mallet finger (DIP extensor avulsion): avulsion of the terminal extensor tendon at the DIP joint, producing a characteristic DIP flexion deformity. MRI characterises the size of any bony fragment, the degree of DIP joint subluxation (which determines whether conservative splinting or surgical stabilisation is appropriate), and the integrity of the articular surface.

Flexor tendon zone II injuries within the digital sheath: lacerations and degenerative partial tears of the FDP or FDS tendons within the flexor sheath (zone II, from A1 pulley to FDS insertion) are assessed pre-operatively on MRI for tear geometry, degree of retraction, and sheath integrity.

Glomus tumour: subungual glomus tumour is the classic indication where a 2–5 mm lesion must be precisely localised before excision. MRI is the definitive pre-operative investigation.

Inflammatory arthritis of individual PIP/DIP joints: when clinical assessment is uncertain between inflammatory arthropathy (RA, psoriatic, gout) and post-traumatic joint changes in a single digit, MRI demonstrates the synovitis pattern, bone erosions, and volar plate integrity that differentiate these entities.

Osteoid osteoma of the phalanx: nocturnal pain relieved by aspirin or NSAIDs in a young adult with a phalangeal lesion visible on radiographs is the classic presentation. MRI demonstrates the nidus, surrounding reactive marrow oedema, and periosteal reaction before CT-guided treatment.

2.2 Urgent Red Flags Requiring Expedited or Emergency Imaging

The finger is not a life-threatening anatomical region. The following clinical scenarios require prompt imaging.

3. Preparation Reference

Universal MRI safety screening is covered in the general MRI preparation page and is not repeated here.

3.1 Anatomy-Specific Preparation Items

Individual finger isolation is mandatory: unlike the hand protocol, which images the entire hand simultaneously, the finger protocol images a single digit. The target finger must be isolated from adjacent fingers to avoid partial-volume contamination. This is achieved by: - Gently abducting the adjacent fingers away from the target digit - Placing foam wedge separators between the target finger and adjacent fingers - Ensuring no contact between the target finger's skin surface and adjacent digits during the acquisition

Rings and nail jewellery: all metallic rings, nail piercings, and metallic nail accessories on the imaged finger or adjacent fingers must be removed before scanning. Even small metallic nail polish or gel coating residues produce susceptibility artefacts at the distal phalanx level.

Prior surgery: document any history of PIP joint arthroplasty, tendon repair, pullley reconstruction (synthetic graft), or internal fixation. Titanium K-wires produce significantly less artefact than stainless steel. Synthetic pulley grafts (silicone, Dacron) are MRI-compatible.

Wound care: any wound dressings, tapes, or splints on the finger must be removed or verified as MR-compatible before positioning.

Thumb specifics: the thumb requires separate plane prescription from the lesser fingers because it lies at approximately 40–50° palmar abduction from the plane of the palm (see Section 4.6). The thumb cannot be meaningfully imaged by adopting the same coronal and axial planes used for the index to little fingers.

Patient pain management: finger MRI requires absolute immobility of the imaged digit. For patients with acute pain, appropriate pre-examination analgesia is relevant to image quality. A painful finger that is involuntarily flexed and guarded cannot be maintained in the required extension for the full acquisition duration.

3.2 Patient Positioning on the MRI System

Position options: the same three positioning options as the hand and wrist protocols — supine arm-at-side, or Superman (prone, arm overhead). For finger MRI, the Superman position is preferred when possible because it places the finger near isocentre, optimising B0 homogeneity, SNR, and fat suppression at the very small FOV (6–8 cm) required for diagnostic resolution.

Superman position specific to fingers: the patient lies prone with the affected arm extended overhead, and the target finger is positioned in the wrist/hand coil with the finger extended along the coil's long axis. The finger must be straight — not flexed — to allow the coronal prescription to display the straight-line course of the collateral ligaments and volar plate. If the patient cannot achieve full finger extension due to injury, image in the available position and document it explicitly.

Supine arm-at-side: acceptable when the patient cannot tolerate Superman. Dixon fat suppression is mandatory in this position. The SNR and fat suppression at the very small FOV of finger imaging (6–8 cm) are more significantly compromised by off-isocentre positioning than for wrist or hand protocols, making Superman the preferred choice for finger MRI specifically.

Coil selection: a dedicated small hand/wrist phased-array coil (16-channel preferred) provides optimal SNR for finger MRI. For single-digit assessment of the PIP and DIP joints specifically, a dedicated cylindrical single-finger coil (if available) provides markedly superior SNR uniformity and spatial resolution compared to a hand/wrist coil [6]. However, clinical departments rarely have access to dedicated single-finger coils; the standard 16-channel hand/wrist coil at 3T is the practical standard.

Centering: isocentre at the specific joint of interest — the PIP joint for most injuries; the DIP joint for jersey finger, mallet finger, or glomus tumour. For pulley assessment, centre at the A2 pulley level (proximal half of the proximal phalanx).

Immobilisation: the target finger must be completely immobilised within the coil. The two most effective immobilisation strategies are: (i) use of the coil's built-in immobilisation system (foam padding around the coil interior), supplemented with custom-cut foam strips wedged between the finger and the coil wall; (ii) medical tape strapping the fingertip gently to the coil exterior, preventing involuntary flexion. Do not apply tape that restricts blood flow or that will be uncomfortable for 25–35 minutes.

Adjacent finger separation: maintain a clear foam gap between the target finger and its neighbours throughout the acquisition. Inadvertent contact between fingers produces partial-volume averaging at the edges of the FOV.

Common positioning errors: - Target finger in slight flexion: volar plate and collateral ligaments cannot be fully assessed in the coronal plane; straight full extension is required - Adjacent fingers in contact with target finger: partial-volume contamination and possible fat suppression failure at the contact interface - Thumb not planned from its own axis: thumb-specific prescriptions must use the first metacarpal long axis as the reference, not the hand plane

4. Standard Protocol Design

The standard finger MRI protocol is built around three orthogonal planes — coronal, sagittal, and axial — each prescribed relative to the individual finger's long axis. Unlike the hand protocol, where a single prescription covers all five metacarpals simultaneously, the finger protocol requires individual prescription for each finger.

4.1 Mandatory Core Sequences

4.2 Conditional Sequences

4.3 Rationale Summary Per Sequence

Coronal PD-FS is the primary sequence for collateral ligament and bone marrow assessment, directly analogous to the coronal plane in the wrist and shoulder. In the coronal plane of the individual finger, the following structures are displayed in their optimal longitudinal cross-section: - The proper collateral ligaments of the PIP and DIP joints: low-signal bands running from the proximal phalanx condyle to the base of the middle phalanx, optimally visible as parallel low-signal structures flanking the joint — a tear manifests as signal discontinuity, oedema, or avulsion fragment - The accessory collateral ligaments: thinner bands volar to the proper collateral, also displayed coronally - The bone marrow of all three phalanges: STIR-supplemented assessment for osteitis, contusion, stress fracture, and tumour changes - The articular surfaces of PIP and DIP joints: cartilage interface and joint space width - The interosseous tendons at MCP level (if included)

Fat suppression is mandatory for the same reasons as in all MSK protocols. Magic angle effect is present in the proper collateral ligaments at PD TE (20–40 ms) because these ligaments run obliquely from the condyle of the proximal phalanx to the phalangeal base. Apparent signal increase in the proper collateral ligament on coronal PD-FS should always be verified on a T2-weighted sequence or the T1 coronal — magic angle disappears at TE > 60 ms; true tears persist.

Sagittal PD-FS is the primary plane for the volar plate, the flexor tendon in its longitudinal profile, the annular pulley system, and the extensor mechanism. Each of these structures runs in the sagittal plane relative to the finger: - The volar plate at the PIP joint: a low-signal triangular structure with its wide attachment at the middle phalangeal base and its more elastic paired check-rein ligament attachments at the proximal phalanx; tear manifests as proximal avulsion with signal change at the attachment or frank discontinuity - The flexor tendons (FDS and FDP) in their entire visible digital course: normal tendons are uniformly low signal; a tear manifests as fluid signal, tendon retraction, or gap - The annular pulleys: visible as focal low-signal thickenings of the tendon sheath overlying the tendon; A2 at the proximal phalanx, A3 at PIP, A4 at middle phalanx; rupture manifests as absence of the pulley with increased bowstringing gap between the tendon and bone - The extensor mechanism: the central slip at its insertion on the dorsal base of the middle phalanx (central slip rupture in Boutonnière deformity) - The posterior fat pad and subungual region (distal phalanx)

The sagittal plane must be perpendicular to the coronal plane of the finger — not perpendicular to the body sagittal plane. A true sagittal of the finger is the lateral view of the digit.

Axial PD-FS provides cross-sectional anatomy of all structures: - The flexor tendons (FDS and FDP) in cross-section: at the level of the proximal phalanx, the FDS tendon is seen as a superficial arc partially surrounding the deeper FDP tendon before its bifurcation (Camper's chiasm); at the PIP level, FDS has bifurcated and FDP is central - The annular pulleys: visible as thin peripheral bands encircling the flexor tendons — the A2 pulley is the thickest and most reliably visualised - The proper and accessory collateral ligaments in cross-section - The extensor mechanism: the central slip (dorsal) and the lateral bands (dorsolateral) - The volar plate in cross-section at the joint level - Bone marrow: cortical integrity of the phalangeal bones

The axial plane at the level of the A2 pulley is the single most important plane for pulley assessment. The axial section shows the pulley as a distinct low-signal ring around the tendon; a partial or complete rupture manifests as absence of this ring focally, with the tendon displaced away from the volar cortex (bowstringing sign) [3].

Coronal T1 provides the anatomical complement for: bone erosion characterisation (cortical break without associated T2 signal, distinguishable from partial-volume artefact); T1 signal characterisation of masses (lipoma, enchondroma); glomus tumour localisation (visible as a T1-intermediate nodule against the fatty marrow of the distal phalanx); magic angle verification.

STIR provides B0-independent bone marrow screening and is the required backup for fat suppression failure. At the very small FOV of finger imaging, STIR is critical because B0 inhomogeneity at the fingertip (near the end of the coil sensitivity region) can cause severe spectral fat saturation failure in the distal phalanx — exactly the region of highest clinical interest for subungual glomus tumour and DIP joint pathology.

4.4 Sequence Matching and Cross-Sequence Consistency

The three orthogonal planes must be prescribed from the individual finger's long axis — not from the body axes. This is the cardinal rule of finger MRI positioning. If the coronal, axial, and sagittal planes are not defined relative to the specific finger's axis: - The proper collateral ligaments will appear oblique on the coronal — appearing thickened or obliquely torn when they are normal - The annular pulleys will not appear as complete rings on the axial — making pulley tear assessment impossible - The volar plate will not be displayed in its triangular profile on the sagittal

For serial follow-up studies (tendon repair integrity, pulley healing), exact reproduction of the plane prescription is critical. The finger axis angles should be documented at the baseline study and reproduced at all subsequent examinations.

Post-contrast sequences must use the same prescription as pre-contrast sequences for meaningful comparison.

4.5 Fat Suppression — Region-Specific Technical Considerations

Fat suppression at the finger faces the extreme version of the off-isocentre B0 challenge described in the wrist and hand protocols. The fingertip — particularly in the Superman position — is at the end of the coil sensitivity region, where B0 homogeneity is least reliable. The distal phalanx (the region of highest clinical interest for glomus tumour and DIP joint pathology) is frequently affected by fat suppression failure at the distal edge of the FOV.

STIR is the most reliable fat suppression technique for finger MRI and provides the most consistent fat suppression across the full length of the digit, including the distal phalanx. STIR is the mandatory backup when any region of spectral fat saturation failure is identified on the PD-FS sequences.

Dixon fat suppression is preferred for PD-FS sequences because its B0-independent mechanism provides the most uniform fat suppression across the finger FOV. At 3T in the Superman position near isocentre, Dixon and SPAIR both perform well; the advantage of Dixon increases in the supine arm-at-side position and at the extreme distal phalanx region.

SPAIR is an acceptable alternative when Dixon is not available.

CHESS/ChemSat: spectral fat saturation alone is unreliable for finger MRI at the distal phalanx level and should not be the sole fat suppression strategy. It may be acceptable when combined with STIR as backup.

STIR contraindicated post-gadolinium — the same absolute rule applies here as in all MRIninja protocols.

5. Optimisation Strategy

5.1 Artifact Reduction by Source

Motion artefact is the dominant and most common cause of non-diagnostic finger MRI. Because the required FOV is 6–8 cm and target in-plane resolution is 0.2–0.3 mm at 3T, even 0.5 mm of motion between acquisitions produces visible image degradation. The lever arm effect — where any shoulder or elbow movement at the proximal end of the extended arm is amplified 20–30-fold at the fingertip — means that minor patient discomfort during Superman positioning can produce significant fingertip motion while the body appears stationary. Prevention: thorough patient preparation explaining the need for absolute stillness; adequate immobilisation of the target digit; foam padding at the shoulder and elbow in Superman position; limiting acquisition blocks to ≤ 5 minutes with brief comfort breaks between.

Off-isocentre B0 inhomogeneity: at the extreme distal phalanx in the supine arm-at-side position, B0 inhomogeneity produces severe spectral fat saturation failure — the worst of any structure in the entire upper extremity MRI series because the FOV is smallest and the finger is farthest from isocentre. Superman position at 3T with a dedicated hand/wrist coil near isocentre provides the best fat suppression. Dixon fat suppression or STIR are mandatory in the supine position.

Magic angle in the collateral ligaments: the proper collateral ligament of the PIP joint runs obliquely from the metacarpal condyle to the phalangeal base at an angle that varies between approximately 40° and 70° to B0 depending on the joint position, the prescription angle, and the specific joint assessed. Magic angle signal increase on coronal PD-FS is the most common source of false-positive collateral ligament tears on finger MRI. It is eliminated at TE > 60 ms (T2 weighting). Verification rule: any collateral ligament signal increase on coronal PD-FS must be assessed on the T1 coronal and, if equivocal, on a T2-weighted sequence.

Susceptibility artefact from nail metallic material: even small residual metallic nail gel coating or metallic pigment in nail polish produces focal T2* dephasing at the distal phalanx that destroys the glomus tumour assessment region and the DIP joint assessment on the distal phalanx. Nail preparation (removal of all metallic coatings) is essential before examining the distal phalanx.

Chemical shift artefact at phalangeal cortex-marrow interfaces: at narrow bandwidth, the yellow marrow of the phalangeal medullary cavity produces a chemical shift displacement line at the cortical interface that can simulate a periosteal reaction or stress fracture. Wider receiver bandwidth (300–500 Hz/px at 3T) reduces this to below the in-plane resolution and eliminates this artefact.

Partial volume averaging from adjacent finger contact: as described in positioning — any contact between the target finger and an adjacent finger produces a mixed tissue voxel at the lateral margins of the finger FOV, simulating periarticular oedema or soft tissue thickening. Foam spacers between fingers are the prevention.

5.2 Protocol Efficiency and Throughput

A full diagnostic finger MRI at 3T with standard hand/wrist coil requires 25–35 minutes. For two adjacent fingers, add 10–15 minutes for the additional prescriptions.

3D isotropic sequences: at 3T, a single 3D isotropic PD-FS acquisition (SPACE/CUBE/VISTA) at 0.3–0.4 mm isotropic provides the coronal, sagittal, and axial planes from a single acquisition. This replaces three separate 2D acquisitions and reduces total scan time by approximately 8–12 minutes. The trade-off is the same as for the wrist: 3D isotropic provides excellent MPR capability at the cost of slightly lower SNR per voxel compared to optimised 2D acquisitions [3].

Short protocol: coronal PD-FS + sagittal PD-FS + axial PD-FS provides the minimum clinically useful finger MRI in approximately 12–15 minutes at 3T. T1 coronal can be omitted if bone characterisation is not the clinical question (e.g., purely soft tissue pathology like pulley rupture).

5.3 Field Strength Considerations

3T is strongly preferred for finger MRI and is effectively the minimum required field strength for reliable diagnostic assessment of the pulley system and collateral ligaments. At 1.5T, the SNR margin for the 0.2–0.3 mm in-plane resolution required for annular pulley assessment is insufficient — published series at 1.5T consistently show lower diagnostic accuracy for partial pulley tears and smaller collateral ligament injuries compared to 3T.

The AJR paper documenting the clinical 3T protocol used a 16-channel hand/wrist coil, TE 24 ms (PD), slice thickness 1.5–2 mm, FOV 6–8 cm, and target in-plane resolution 0.2–0.3 mm — parameters achievable only at 3T with dedicated surface coil [3].

1.5T with dedicated hand/wrist coil: clinically adequate for complete pulley tears, large collateral ligament tears, volar plate avulsion with fragment, FDP avulsion (jersey finger), and bone marrow assessment. Not adequate for subtle partial pulley tears or very small ligament injuries.

7T research imaging: achieves in-plane resolution of 160–200 μm for finger joints, enabling resolution of articular cartilage, individual pulley laminae, and ligament fibre bundles not visible at clinical field strengths [6]. Not available for routine clinical use but represents the research frontier demonstrating the information potentially accessible with further SNR improvement.

6. Contrast Use Principles Specific to Finger MRI

6.1 Non-Contrast Standard Protocol — Sufficient For

• Complete and most partial flexor pulley tears (A2, A3, A4)
• Collateral ligament tears (PIP, DIP, MCP)
• Volar plate tears
• Central slip rupture and Boutonnière deformity
• Jersey finger (FDP avulsion) — complete and retracted
• Mallet finger (DIP extensor avulsion)
• Bone marrow screening (stress fracture, osteoid osteoma nidus, enchondroma)
• Glomus tumour detection (T2-bright subungual nodule without contrast)
• Post-traumatic joint effusion and periarticular oedema

6.2 Gadolinium Indicated — Region-Specific Contexts

Glomus tumour: while T2-bright subungual nodules can be detected without contrast, post-contrast T1-FS sequences confirm the intensely enhancing nature of glomus tumour and enable precise localisation against the enhancing nail bed for surgical planning. For pre-operative planning specifically, post-contrast sequences are recommended.

Flexor tendon sheath infection: post-contrast axial and sagittal sequences demonstrate the enhancing sheath and define the distal and proximal extent of purulent tenosynovitis, guiding surgical incision planning.

Soft tissue mass characterisation: vascular malformations, fibromatoses, and malignant soft tissue lesions require enhancement characterisation. Giant cell tumour of the tendon sheath (GCTTS) shows variable enhancement; lipoma does not enhance; glomus tumour enhances intensely.

Inflammatory PIP/DIP joint arthritis: when synovitis quantification is the clinical question, post-contrast T1-FS sequences demonstrate synovial enhancement pattern distinguishing active RA, gout, and psoriatic arthritis.

6.3 Post-Contrast Acquisition Timing

For glomus tumour and vascular lesion assessment: immediate to 2-minute post-injection timing maximises the enhancement differential between the lesion and surrounding tissue.

For inflammatory synovitis: 3–5 minutes post-injection provides adequate synovial enhancement.

STIR contraindicated post-gadolinium — same absolute rule as all other protocols.

7. Reporting Essentials

7.1 Interpretation Framework

The finger MRI report should assess five anatomical compartments for each digit: (i) the flexor tendon system (FDS and FDP tendons, annular pulleys A1–A5, cruciate pulleys); (ii) the extensor mechanism (extensor digitorum, central slip at PIP insertion, lateral bands, triangular ligament); (iii) the capsuloligamentous structures (proper and accessory collateral ligaments at each joint, volar plate); (iv) the osseous structures (cortex and marrow of all three phalanges, subchondral bone, articular surfaces); and (v) periarticular and para-tendinous soft tissues (tendon sheaths, ganglia, masses).

For each joint (MCP, PIP, DIP): assess separately because pathology rarely involves all three joints simultaneously, and the surgical implications of PIP vs. DIP collateral ligament tears are different.

Pulley system: report each pulley individually (A1 to A5). State which pulleys are intact and which show complete or partial tears. Document the bowstringing gap if present — measured as the perpendicular distance between the volar cortex and the volar surface of the flexor tendon at the level of maximal displacement on the sagittal sequence.

7.2 Mandatory Reporting Checklist

Flexor system: - FDS tendon at each segment: intact / signal change / partial tear / complete tear - FDP tendon at each segment: intact / signal change / partial tear / complete tear; if ruptured — retraction level (Leddy classification if applicable) - Pulley system: A1, A2, A3, A4, A5 each individually: intact / partial tear / complete tear; bowstringing gap if present

Extensor system: - Central slip at PIP insertion: intact / partial tear / complete tear - Lateral bands: intact / volar subluxation (Boutonnière) - Terminal extensor at DIP insertion: intact / avulsion (mallet)

Capsuloligamentous structures (at each joint): - Proper collateral ligament (radial and ulnar): intact / sprain / partial tear / complete tear; avulsion fragment - Accessory collateral ligament: intact / tear - Volar plate: intact / sprain / partial tear / avulsion with check-rein (PIP level)

Osseous structures: - Phalangeal cortex: intact / cortical disruption / stress fracture - Bone marrow signal: normal / oedema (specify location) - Joint articular surfaces: intact / subchondral change / erosion

Soft tissues: - Tendon sheath: normal / tenosynovitis (fluid volume) - Soft tissue masses: location, dimensions, signal characteristics

Technical limitations: fat suppression quality, motion artefact, nail contamination artefact, adjacent finger contact

7.3 Structured Reporting

Reports: Indication (clinical question, finger, joint level, laterality); Technique (field strength, position, coil, sequences, contrast); Comparison; Findings (per anatomical compartment); Impression; Limitations; Critical communication if required.

7.4 Incidental Findings — Clinical Decision Framework

Usually benign: small interphalangeal joint effusion without synovitis; cortical irregularity at the volar plate attachment of the middle phalanx base in young adults (normal variant avulsion ossicle); mild flexor tendon sheath fluid in elderly patients; mild enchondromal-type signal in the phalangeal medullary cavity.

May require clinical correlation: bone marrow oedema at a specific phalangeal level without history of trauma in an older patient — may represent early inflammatory arthritis; small subungual T2-bright lesion without clinical symptoms of glomus tumour — follow-up versus clinical correlation.

Require explicit communication: aggressive bone lesion features at any phalangeal level; complete FDP avulsion with proximal retraction not mentioned in the clinical request (changes surgical urgency immediately); subungual mass with T2 characteristics atypical for glomus tumour (alternative malignant subungual neoplasm).

8. MRI Technologist Pearls

8.1 Sequence Order Logic

Recommended acquisition order for standard non-contrast finger MRI:

1. Three-plane body localiser
2. Dedicated finger localiser (low-resolution coronal + axial through the target digit) ← mandatory additional planning step unique to finger MRI
3. Coronal PD-FS ← most diagnostically critical for collateral ligaments; acquire after good positioning is confirmed
4. Sagittal PD-FS ← volar plate, pulley, tendons
5. Axial PD-FS ← pulley cross-sections, tendon cross-sections
6. Coronal T1
7. STIR (coronal or sagittal)

8.2 Positioning Tricks

• For the Superman position: position the wrist so that the target finger is at the centre of the coil. For the index finger, the wrist is positioned in slight ulnar deviation; for the little finger, in slight radial deviation. This centres the target digit in the highest-SNR zone of the coil.
• For the single-finger examination with a standard hand/wrist coil: gently flex the adjacent fingers away from the target finger using foam wedge separators, and rest them against the coil wall. The target finger should be straight and isolated.
• For the thumb: position the thumb in slight abduction with the palmar surface facing slightly upward. The thumb axis will be oblique in the coil — plan the prescription from the localiser showing the thumb axis most clearly, not from the body axes.
• For glomus tumour examination: the distal phalanx must be precisely at isocentre. Adjust the table position so that the distal phalanx — not the PIP joint — is at the laser alignment line.
• If the patient cannot maintain Superman for the full protocol: prioritise the coronal and sagittal PD-FS (the two most diagnostically critical sequences), then return to the axial and T1 sequences. Most clinical questions can be addressed with coronal + sagittal alone.

8.3 Fast Salvage Protocol

Three sequences in approximately 10 minutes provide the minimum diagnostically interpretable finger MRI.

8.4 Common Avoidable Errors

9. Quality Control Checklist

• Dedicated finger localiser obtained before diagnostic sequences
• Coronal planes parallel to dorsal phalangeal cortex (verified on axial localiser)
• Axial planes strictly perpendicular to phalangeal long axis (verified on sagittal localiser)
• A2 pulley level (proximal half of proximal phalanx) included in axial coverage
• DIP joint and distal phalanx included in coverage
• Adjacent fingers not in contact with target digit
• Thumb prescribed from thumb axis if thumb is the target
• Fat suppression uniform across full finger FOV — no regional failure (especially distal phalanx)
• STIR acquired before gadolinium injection
• Post-contrast sequences acquired at appropriate timing (if used)
• No significant motion artefact on coronal PD-FS
• No susceptibility artefact from metallic nail material
• Correct laterality and finger identity documented in sequence labels
• All five mandatory sequences completed

11. Evidence Gaps and Ongoing Debate

Partial pulley tear detection limits: the clinical threshold for detection of partial A2 pulley tears on non-arthrographic 3T MRI with standard hand/wrist coils has not been formally established in a large prospective arthroscopy-confirmed study. Published series are limited in size, predominantly retrospective, and use varying MRI protocols and coil configurations. The minimum pulley tear area that is reliably detectable at clinical 3T MRI resolution is unknown.

Single-finger coil vs. standard hand/wrist coil: while dedicated cylindrical single-finger coils demonstrably improve SNR and spatial resolution, no prospective comparative study has documented a clinically significant difference in diagnostic accuracy between a standard 16-channel hand/wrist coil at 3T and a dedicated single-finger coil for pulley and ligament assessment in the clinical setting.

3D isotropic sequences vs. 2D optimised sequences for finger MRI: the comparative diagnostic accuracy of 3D isotropic PD-FS (SPACE/CUBE) at 0.3–0.4 mm isotropic versus 2D PD-FS at 0.2–0.3 mm optimised in-plane resolution for pulley and collateral ligament assessment at the finger level has not been prospectively evaluated.

AI reconstruction for finger MRI: deep learning reconstruction applied to undersampled 3D finger MRI has been described in early reports but not validated for the specific diagnostic tasks of pulley and ligament tear detection.

MR arthrography for PIP/DIP ligament tears: the diagnostic benefit of direct MR arthrography versus optimised non-arthrographic 3T MRI for PIP collateral ligament partial tears has not been established. Given the small joint size and the complexity of intra-articular injection of the PIP joint, the clinical threshold for arthrography of the finger joints is not clearly defined.

Dynamic MRI for pulley bowstringing: static MRI in extension underestimates the degree of bowstringing compared to dynamic imaging in flexion. Standardised dynamic finger MRI protocols for pulley bowstringing quantification are in development but not yet in clinical use.

12. Evidence-Based References

A. Guidelines / Consensus / Society Recommendations

(No specialty society guidelines specific to finger MRI protocol exist. The evidence base rests primarily on prospective cohort studies and technical papers.)

B. Systematic Reviews / Meta-analyses

(No systematic reviews addressing finger MRI technical protocol were identified in the literature search.)

C. Important Prospective / Original Studies

D. Technical MRI Papers

E. Landmark Historical References

End of document — MRI Fingers Generic Standard Protocol — MRIninja v1.0 — May 2026 This master page is the reference for all future finger MRI child pages including: flexor pulley rupture protocol, PIP collateral ligament tear, volar plate injury, central slip rupture and Boutonnière deformity, jersey finger (FDP avulsion), mallet finger, glomus tumour, osteoid osteoma of the phalanx, and inflammatory PIP/DIP arthritis.