MRI Toes – Generic Standard Protocol

1. Executive Summary

Toe MRI occupies the extreme high-resolution end of the musculoskeletal imaging spectrum. The diagnostic structures of interest — plantar plates (0.5–2 mm thick), collateral ligaments (1–2 mm wide), flexor and extensor tendons (2–5 mm in cross-section), and the articular cartilage of the metatarsophalangeal (MTP) and interphalangeal (IP) joints (< 1 mm) — are among the smallest diagnostic targets in all of MRI. This demands the highest achievable spatial resolution in clinical practice, which in turn requires dedicated small-bore coils, optimal patient positioning, and the same level of technical precision described in the MRI Fingers master page.

The clinical context of toe MRI differs substantially from finger MRI despite superficial structural similarities. The weight-bearing function of the foot places unique mechanical demands on the plantar plate — the fibrocartilaginous structure at the plantar aspect of the MTP joint — which is the primary target of the most common toe MRI indication: lesser toe MTP joint instability and plantar plate tear. The great toe (hallux) MTP joint, with its two sesamoid bones embedded in the flexor hallucis brevis tendons, represents a distinct anatomical complex that is the primary target of turf toe assessment. Inflammatory arthropathy — rheumatoid arthritis, psoriatic arthritis, gout — produces characteristic toe findings that require both structural and bone marrow assessment. Diabetic foot with toe involvement — osteomyelitis, ulceration, neuropathic changes — places additional demands on post-contrast and bone marrow sequences.

Compared with ultrasound, MRI provides superior assessment of the deep plantar plate structures, the collateral ligaments, the intraosseous extent of early osteomyelitis, and the bone marrow changes of early stress reaction. Ultrasound is superior for dynamic assessment of the plantar plate under load and for Morton's neuroma (which lies in the intermetatarsal space just proximal to the MTP joint — at the boundary of the forefoot and the toe MTP joint level). CT is superior for cortical bone detail in acute fracture assessment and for sesamoid fracture classification.

1.1 Core Strengths

Plantar plate integrity: the plantar plate at the second MTP joint — the most common site of plantar plate pathology — is a 2 mm thick fibrocartilaginous structure at the plantar aspect of the MTP joint, directly attached to the base of the proximal phalanx. Partial and complete plantar plate tears are clearly depicted on coronal and sagittal PD-FS sequences at ≤ 0.3 mm in-plane resolution. MRI is the definitive pre-surgical assessment tool for plantar plate repair planning.

Hallux MTP sesamoid complex: the two sesamoids (medial and tibial) embedded in the flexor hallucis brevis are assessed for fracture, osteonecrosis, bipartition versus fracture, and sesamoiditis by bone marrow signal on T1 and STIR. The plantar plate of the hallux MTP joint (the intersesamoid ligament) and the metatarsosesamoid ligaments are assessed on coronal and axial sequences.

Bone marrow sensitivity for early osteomyelitis: MRI detects osteomyelitis in the phalanges and metatarsal heads weeks before radiographic changes, and with sensitivity superior to nuclear medicine in the context of diabetic foot neuropathic disease — particularly important for toe tip and distal phalangeal osteomyelitis overlying diabetic ulcers.

Inflammatory arthropathy: the periarticular soft tissue swelling, bone erosions, joint effusion, and bone marrow oedema of rheumatoid, psoriatic, and gouty arthropathy at the MTP and IP joints are characterised on multisequence MRI.

Turf toe (first MTP plantar plate-capsular complex): MRI documents the full injury spectrum of first MTP joint injury from sprain to complete capsular disruption, sesamoid displacement, and chondral injury.

1.2 Intrinsic Limitations of the Generic Protocol

Resolution at the plantar plate detection threshold: the plantar plate of the lesser toes is approximately 2 mm thick at its distal insertion on the proximal phalangeal base. At clinical 3T with a standard hand/wrist coil (the typical coil for toe MRI), the target in-plane resolution is 0.2–0.3 mm, which places small partial tears at the edge of detection. Very thin partial tears of the distal plantar plate insertion may not be reliably visualised.

All toes cannot be optimally imaged in a single acquisition: the five toes diverge laterally from their metatarsal heads by different angles. A single coronal acquisition plane optimised for the second MTP joint will be slightly oblique relative to the fourth and fifth MTP joints. For all-toe coverage at optimal resolution, a single common prescription is a compromise. Individual toe protocols — as described in the dedicated Fingers-equivalent approach — provide the best resolution for a single toe.

The hallux requires a separate prescription: as with the thumb in the MRI Fingers protocol, the hallux lies in a slightly different plane from the lesser toes and requires either its own prescription or a compromise angulation that partially degrades either the hallux or the lesser toe planes.

Weight-bearing function not assessable: the plantar plate injury spectrum is biomechanically defined by load, but MRI is performed non-weight-bearing. Clinical instability and subluxation under load — the surgical threshold criterion — are assessed on weight-bearing plain radiographs, not MRI.

When dedicated child protocols are required: plantar plate tear with surgical planning; turf toe (first MTP capsular-ligamentous injury); sesamoid osteonecrosis; diabetic toe osteomyelitis; Morton's neuroma (forefoot protocol); psoriatic/rheumatoid MTP joint assessment; gout tophus characterisation.

2. Main Clinical Indications

2.1 Standard Indications

Plantar plate tear of the lesser MTP joints is the primary sports medicine indication for toe MRI. The second MTP joint plantar plate is most commonly affected, followed by the third. Clinical presentation is chronic plantar pain and deformity (hammertoe, crossover toe) from plantar plate failure. MRI characterises the tear location (distal insertion vs. mid-substance), grade (partial vs. complete), and associated collateral ligament status and MTP joint instability — all of which guide the surgical decision. The generic protocol with high-resolution coronal and sagittal PD-FS sequences centred on the second to fourth MTP joints is adequate for initial assessment.

Turf toe (first MTP injury) occurs in athletes from forced hyperextension of the hallux MTP joint. The injury spectrum ranges from sprain to complete plantar capsule disruption with sesamoid fracture or proximal sesamoid dislocation. MRI is the primary tool for injury grading, sesamoid assessment, and surgical planning. The hallux requires its own prescription plane from the hallux long axis.

Sesamoid pathology — sesamoiditis, sesamoid stress fracture, avascular necrosis of the sesamoid, and bipartition versus fracture — produces plantar hallux pain. T1 and STIR sequences characterise the marrow signal; PD-FS coronal sequences assess the sesamoid-metatarsal articular surfaces and the intersesamoid ligament.

Diabetic toe osteomyelitis — particularly at the distal phalanges overlying neuropathic ulcers — is one of the most clinically important toe MRI indications. The generic protocol with STIR + T1 + post-contrast T1-FS provides the standard assessment. DWI adds sensitivity for acute osteomyelitis versus soft tissue cellulitis versus Charcot change at the toe level.

Inflammatory arthropathy MTP and IP joint assessment in rheumatoid arthritis, psoriatic arthritis, and gout produces characteristic MRI findings: the "squeezed toothpaste" pattern of rheumatoid MTP joint erosion; the asymmetric enthesitis and erosion of psoriatic MTP disease; the tophus of gout with its T2* blooming and T1 intermediate signal.

Post-traumatic assessment: subacute toe injuries — collateral ligament tears at IP joints, phalangeal stress fractures, post-fracture non-union, and late post-traumatic osteonecrosis — are assessed when clinical examination or radiographs are inconclusive.

Soft tissue masses at the toe: glomangioma (glomus tumour) of the great toe tip subungual region (identical to the finger equivalent described in the MRI Fingers master page); ganglion cysts; lipoma; vascular malformation.

2.2 Urgent Red Flags Requiring Expedited or Emergency Imaging

The toes are not a life-threatening region. The following 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

Nail coatings and toe jewellery: metallic nail polish, gel nail coatings with metallic pigments, nail piercings, and toe rings must all be removed before toe MRI. These metallic materials produce susceptibility artefacts at the distal phalanx — precisely the region of highest clinical interest for subungual glomus tumour, nail bed pathology, and distal phalangeal osteomyelitis. The same rules apply as for the MRI Fingers protocol.

Compression hosiery and dressings: wound dressings, adhesive tapes, and compression hosiery must be removed. Wound dressings may contain metallic components (silver-impregnated dressings) that produce T2* signal loss over the wound region.

Prior surgical hardware: K-wires, screws, and arthrodesis hardware from toe surgery (hallux valgus correction, claw toe repair, MTP fusion) produce susceptibility artefacts. At 3T, these are substantially more severe than at 1.5T. For post-operative toe MRI, 1.5T is preferred and MARS sequences (wider bandwidth, STIR) should be applied.

Pain management: toe pain — particularly from plantar plate pathology, turf toe, or diabetic neuropathic changes — may make positioning uncomfortable for 25–35 minutes. Pre-examination analgesia improves positioning tolerance and reduces motion. For acute diabetic toe infection, pain may prevent full toe extension into the neutral position; the foot should be imaged in the available position and this documented.

Bilateral comparison: the contralateral toe is useful for comparison in conditions where the "normal" baseline is the clinical question — mild bone marrow signal or plantar plate thickness in the contralateral foot provides a direct reference. Bilateral toe imaging adds time but can be achieved by repositioning.

3.2 Patient Positioning on the MRI System

Position options: the same three options as for the foot and ankle series:

Superman (prone, arm overhead): the preferred position for toe MRI when tolerated. Places the toes at or near isocentre, maximising B0 homogeneity and fat suppression quality. The toes are held in a neutral dorsiflexion position (approximately 10–20° plantar flexion). At isocentre, SPAIR fat suppression is reliable; Dixon provides additional assurance.

Supine feet-first: the most comfortable position. The toes are at 40–60 cm from isocentre, where B0 inhomogeneity is pronounced. Dixon fat suppression is mandatory at this distance. Despite the off-isocentre disadvantage, supine feet-first is clinically adequate with Dixon.

Supine head-first: worst option for fat suppression; only used as a last resort.

Coil selection: a dedicated small extremity coil (hand/wrist phased-array, typically 8 channels, internal diameter 10–15 cm) placed directly over the forefoot and toes provides the highest SNR for toe MRI. For the great toe or a single lesser toe, the wrist channel positions that are closest to the toe of interest provide the best coil coupling. If a dedicated 16-channel small extremity coil is available, it provides superior SNR for sub-0.3 mm resolution.

The toes are even smaller than the mid-foot structures, and the SNR constraint is the primary limitation on achievable resolution. A larger coil (knee coil, body coil) provides insufficient SNR for the 0.2–0.3 mm in-plane resolution required for plantar plate assessment.

Individual toe isolation: for single-toe assessment (e.g., single-toe plantar plate repair planning, glomus tumour localisation), the target toe should be isolated from adjacent toes using foam wedge separators. Contact between toes produces partial-volume averaging at the margins of the small toe FOV and degrades fat suppression at the contact interface.

Centring: isocentre at the level of the second MTP joint (the most common pathological level and the reference for lesser toe plantar plate assessment). For hallux-specific examinations, centre at the first MTP joint. For IP joint assessment (hammer toe, claw toe), adjust the centring distally.

FOV and coverage: the FOV must include the plantar plates of the relevant MTP joints distally and extend to the mid-proximal phalanx shaft proximally for complete collateral ligament and flexor tendon assessment.

Hallux prescription: the hallux lies at approximately 10–15° abduction from the midline of the foot. Its long axis must be used as the reference for the hallux-specific coronal and sagittal planes, separately from the lesser toes.

Common positioning errors:

• Toes in forced plantar flexion: the plantar plate-phalangeal base interface is not in the neutral position; sagittal plane foreshortens the plantar plate profile
• Adjacent toes in contact with target toe: partial volume contamination
• Coil placed over ankle rather than forefoot: toes at the edge of coil sensitivity; SNR insufficient for plantar plate resolution
• Hallux not separately planned: oblique sections through the hallux MTP joint when the lesser toe prescription is applied

4. Standard Protocol Design

4.1 Mandatory Core Sequences

4.2 Conditional Sequences

4.3 Rationale Summary Per Sequence

Coronal PD-FS is the primary sequence for toe MRI and provides the plantar plate assessment that is the diagnostic cornerstone of the examination. The coronal plane — perpendicular to the long axis of the metatarsals and toes — displays the plantar plate at the MTP joint in its widest cross-section, showing the plantar plate width, medial and lateral gutters, the sesamoid-metatarsal articular surfaces, and the collateral ligaments of the MTP joints simultaneously. The critical diagnostic sign of plantar plate tear — T2-bright signal within the low-signal fibrocartilaginous plate — is most conspicuous on coronal PD-FS. The plantar plate is approximately 2 mm thick and 10–12 mm wide at the second MTP joint; its visualisation requires ≤ 0.3 mm in-plane resolution to differentiate normal from partial tear at the insertion.

Fat suppression is mandatory on this sequence to reveal bone marrow oedema in the metatarsal heads and phalangeal bases against the normal fatty marrow background, and to improve the signal-to-noise ratio for the plantar plate signal.

Sagittal PD-FS provides the longitudinal profile of each toe — the plantar plate in its length, the flexor tendons (flexor digitorum longus and brevis at the distal phalanges; flexor hallucis longus at the hallux), the extensor mechanism (extensor digitorum longus, extensor brevis, and the extensor hood), and the IP joint profiles. Plantar plate tears are characterised by the T2 signal extension into the plate substance on sagittal images — the "J sign" (plantar plate curling proximally after full-thickness distal avulsion) is a sagittal sign. The flexor tendon injury within the flexor sheath and the fibrous flexor sheath integrity are assessed on sagittal sequences.

Axial PD-FS provides the cross-sectional anatomy at each MTP and IP joint level. The plantar plate in cross-section appears as a low-signal band at the plantar MTP joint; the collateral ligaments are seen in cross-section medially and laterally. The flexor digitorum longus and brevis tendons in the flexor sheath, the lumbrical muscles, and the interosseous tendons are seen in cross-section on axial sequences. The neurovascular bundles adjacent to each toe are visible, as are small digital nerve tumours at the MTP level (Morton's neuroma — though the full Morton's neuroma protocol centred on the intermetatarsal space is a mid-foot/forefoot rather than toe protocol).

Coronal T1 provides the anatomical and bone marrow baseline. Normal yellow marrow in the metatarsal heads and phalanges is T1-bright; replacement by oedema, tumour, or infection is T1-dark. This is the reference sequence for bone marrow characterisation in suspected osteomyelitis (which appears T1 dark and STIR bright) versus neuropathic or post-traumatic changes. The T1 also characterises subungual glomus tumours (typically T1 intermediate) and distinguishes lipoma (T1 bright, suppressed on fat-sat) from other soft tissue masses.

STIR provides B0-independent bone marrow oedema screening at the off-isocentre positions typical of toe MRI. At the extreme distal toes — particularly the distal phalanges of the lateral toes — B0 inhomogeneity produces spectral fat suppression failure precisely at the clinically important regions. STIR is essential as a bone marrow screen in diabetic toe osteomyelitis assessment and in stress reaction detection.

4.4 Sequence Matching and Cross-Sequence Consistency

The three orthogonal planes must all be prescribed from the individual toe's or metatarsal's long axis — the same principle as for finger MRI (see MRI Fingers master page). In practice:

For the lesser toes (second to fifth): a single prescription from the second metatarsal long axis provides adequate coverage for the second through fourth MTP joints simultaneously. The fifth MTP joint lies at a slightly different angle; a separate prescription or acceptance of mild obliquity is required.

For the hallux: always prescribe a separate set of coronal and sagittal planes from the hallux long axis, because the abduction angle of the hallux from the lesser toes makes a shared prescription suboptimal.

Post-contrast T1-FS sequences must be geometrically matched to the pre-contrast T1 for subtraction imaging and for enhancement characterisation.

For serial examinations (plantar plate repair healing, osteomyelitis treatment response), document the toe axis angulation and reproduce it at follow-up.

4.5 Fat Suppression — Region-Specific Technical Considerations

The fat suppression challenges at the toes are identical to those at the fingers (see MRI Fingers master page) and at the mid-foot, but are more severe because the toes are at the greatest distance from isocentre and at the furthest reach of the coil sensitivity region.

Dixon fat suppression is the preferred technique for all PD-FS and T1-FS sequences in toe MRI. B0-independent fat-water separation is essential at the distal toe phalanges, where spectral fat suppression consistently fails due to the extreme B0 inhomogeneity at 30–60 cm from isocentre.

STIR is the mandatory bone marrow screening sequence because it provides reliable fat suppression independent of B0. At the distal phalanges and the sesamoids, STIR ensures that marrow oedema is not missed even when spectral methods fail locally.

SPAIR is acceptable at the MTP joint level in Superman position near isocentre; unreliable at the distal phalanges even at isocentre due to the small tissue cross-section and susceptibility from nail beds.

STIR post-gadolinium: strictly contraindicated, as in all MRIninja protocols.

5. Optimisation Strategy

5.1 Artifact Reduction by Source

Off-isocentre fat suppression failure is the dominant technical failure mode in toe MRI, as in mid-foot and finger MRI. The toes are at the extreme distance from isocentre (up to 60 cm in supine feet-first position) and at the distal end of the coil sensitivity region. Fat suppression failure at the distal phalanges — precisely the zone of interest for subungual glomus tumour and distal osteomyelitis — is the most common cause of non-diagnostic toe MRI. Dixon fat suppression is mandatory for all toe sequences in supine positioning; SPAIR and CHESS are unreliable at the toe phalanges in this position. STIR provides B0-independent backup.

Motion artefact at high resolution: at the 0.2–0.3 mm in-plane resolution required for plantar plate assessment, even sub-millimetre voluntary or involuntary toe motion produces diagnostic-quality-reducing blurring. Specific risks: (1) the "lever arm" effect — any ankle or mid-foot motion is amplified at the toe tips; (2) pain-related guarding — a patient with plantar plate pain may involuntarily curl the toes during the examination; (3) involuntary toe flexion after antalgic loading. Prevention: comprehensive foam immobilisation in the coil; individual toe isolation and stabilisation; patient counselling about absolute toe stillness; keep each acquisition to ≤ 5 minutes.

Susceptibility from nail metallic material: metallic nail polish, gel nails with metallic pigment, and nail piercings produce T2* signal loss at the distal phalanges on all sequences. This must be removed before scanning. Any residual metallic coating that was not identified pre-scan must be documented in the report as degrading the distal phalangeal and DIP joint assessment.

Chemical shift artefact at phalangeal cortex-marrow interfaces: identical to finger MRI — at narrow bandwidth, the fat-water frequency difference produces bright/dark bands at the cortical margins of the phalanges that can simulate periosteal reaction or cortical disruption. Wider receiver bandwidth (300–500 Hz/px at 3T) eliminates this artefact.

Partial volume from adjacent toe contact: identical principle as fingers — contact between adjacent toes produces mixed-tissue voxels at the lateral margins of the FOV and can simulate periarticular swelling or degrade fat suppression at the contact interface. Foam spacers between toes are the solution.

Magic angle in toe tendons and plantar plate: at PD TE (20–40 ms), the flexor digitorum longus and brevis tendons and the plantar plate fibres that run at approximately 55° to B0 show apparent signal increase. For the plantar plate specifically, this may be difficult to distinguish from a partial tear. Verify any equivocal PD signal in the plantar plate or tendons with a T2-weighted sequence (TE > 60 ms) — magic angle disappears; true tears persist.

5.2 Protocol Efficiency and Throughput

A complete single-toe MRI (e.g., second MTP plantar plate and collateral ligament assessment) at 3T with a hand/wrist coil requires 20–30 minutes. For multi-toe assessment (second through fourth MTP joints, plantar plate and sesamoid survey), 25–35 minutes. Adding post-contrast sequences adds 8–12 minutes.

For the most common indication — second MTP plantar plate tear assessment — a focused protocol of coronal PD-FS + sagittal PD-FS + axial PD-FS + coronal T1 + STIR in 20–25 minutes non-contrast is usually sufficient for complete assessment.

For diabetic foot toe assessment (osteomyelitis), post-contrast T1 is mandatory and the total extends to 35–40 minutes.

5.3 Field Strength Considerations

3T is the preferred field strength for toe MRI. The higher SNR supports the sub-0.3 mm in-plane resolution required for plantar plate assessment. At 3T with a dedicated small extremity coil, 0.2 × 0.2 mm in-plane at 1.5–2 mm slice thickness is achievable within 5 minutes per sequence — the same target resolution described for finger MRI.

1.5T with a dedicated small extremity coil: clinically adequate for most toe indications, particularly where plantar plate tear status (present or absent) is the binary question. Target in-plane resolution at 1.5T is 0.3–0.4 mm, sufficient for grade 2 and 3 plantar plate tears but borderline for early grade 1 tears.

1.5T is preferred for: post-operative toes with metallic hardware (substantially less susceptibility artefact); when the clinical question is answered at lower resolution (osteomyelitis bone marrow assessment, inflammatory arthropathy bone erosion screening).

6. Contrast Use Principles Specific to Toe MRI

6.1 Non-Contrast Standard Protocol — Sufficient For

Non-contrast toe MRI (PD-FS three planes + T1 + STIR) is diagnostically adequate for:

• Plantar plate integrity assessment (partial vs complete tear)
• Collateral ligament tears at MTP and IP joints
• Turf toe injury grading (capsular sprain vs disruption)
• Sesamoid assessment (fracture, osteonecrosis, bipartition)
• Post-traumatic bone marrow contusion and stress fracture
• Flexor and extensor tendon integrity at the toe level
• Soft tissue masses with benign T2 and T1 signal characteristics
• Glomus tumour detection (T2-bright subungual nodule — identified without contrast)
• Gout tophus identification (T2* and T1 signal patterns)

For the majority of sports medicine and post-traumatic toe indications, contrast is not required.

6.2 Gadolinium Indicated — Region-Specific Contexts

Gadolinium is required or strongly useful for:

• Diabetic toe osteomyelitis: enhancement of the medullary cavity in cortical-breach osteomyelitis; rim enhancement of abscess; sinus tract delineation; differentiation from neuropathic Charcot change
• Soft tissue mass characterisation: glomus tumour (intense enhancement confirms the diagnosis); vascular malformation; fibrosarcoma
• Inflammatory arthropathy synovitis quantification: when the clinical question is active synovitis assessment vs. joint damage — synovial pannus enhancement
• Septic arthritis of MTP/IP joints: synovial enhancement and periarticular enhancement
• Post-surgical assessment: enhancement at repair site; suspected infected hardware

6.3 Post-Contrast Acquisition Timing

For toe osteomyelitis and inflammatory indications: standard post-contrast T1-FS at 3–5 minutes after injection (equilibrium phase). The enhancement of bone marrow in osteomyelitis is diffuse; sinus tract enhancement is evident; synovial enhancement is maximal at this phase.

For glomus tumour: immediate to 2-minute post-injection timing maximises enhancement conspicuity. The pre-contrast T1 localises the subungual nodule; post-contrast confirms intense enhancement.

STIR must not be acquired after gadolinium injection — as stated throughout the MRIninja protocol series.

7. Reporting Essentials

7.1 Interpretation Framework

Toe MRI reporting requires systematic assessment of each anatomical compartment for each relevant toe:

Plantar plate and capsule: at the MTP joint level — integrity, signal, width at the plantar phalangeal insertion. Grade the plantar plate using the Coughlin/Nery grading system (Grades 0–4), which is based on macroscopic and MRI/surgical correlates.

Collateral ligaments: medial (tibial) and lateral (fibular) at each MTP joint — normal/sprain/partial tear/complete tear.

Flexor tendons: FDL and FDB at the toe level — intact/signal change/partial tear/complete tear; sheath fluid.

Extensor mechanism: extensor digitorum longus and extensor hood — intact/injury.

Bone marrow: T1 and STIR signal in each metatarsal head and phalanx — normal/oedema/dark (infiltration/infection).

Articular surfaces: MTP and IP joint cartilage; joint space; subchondral signal.

Soft tissues: subcutaneous fat; skin (for diabetic ulcer); digital nerves (enlargement at MTP level); any mass.

Broad axes: acute vs chronic; traumatic vs inflammatory vs neuropathic; confined to joint vs extraarticular.

7.2 Mandatory Reporting Checklist

Technical quality:

• [ ] Field strength and coil documented
• [ ] Fat suppression technique noted
• [ ] Motion artefacts or fat suppression failures limiting interpretation noted
• [ ] Nail metallic material presence noted (if limiting distal phalanx assessment)

Plantar plate (for each relevant MTP joint):

• [ ] Plantar plate thickness and signal (normal / signal change / partial tear / complete tear)
• [ ] Distal insertion: intact / avulsion signal
• [ ] Plantar plate grade if applicable

Collateral ligaments (each MTP joint):

• [ ] Medial: intact / sprain / partial tear / complete tear
• [ ] Lateral: intact / sprain / partial tear / complete tear

Flexor tendons:

• [ ] FDL/FDB: intact / signal change / partial tear / complete tear; sheath fluid

Sesamoids (hallux):

• [ ] Medial sesamoid: morphology / marrow signal
• [ ] Lateral sesamoid: morphology / marrow signal
• [ ] Intersesamoid ligament: intact / disrupted

Bone marrow (all toes in FOV):

• [ ] Each metatarsal head and phalanx: normal / oedema / dark (infiltration)

MTP and IP joints:

• [ ] Joint space: normal / narrowed
• [ ] Effusion: absent / present
• [ ] Erosions: absent / present (location)

Soft tissues:

• [ ] Subungual region: normal / lesion (size, signal)
• [ ] Digital nerve: normal / enlarged
• [ ] Subcutaneous oedema / ulcer depth (diabetic foot)

7.3 Structured Reporting

Reports must include: Indication; Technique (field strength, coil, sequences, contrast if used); Comparison; Findings (by anatomical compartment); Impression (direct answer including plantar plate grade, sesamoid status, or osteomyelitis extent); Recommendations; Limitations (fat suppression failure, motion, hardware artefact).

7.4 Incidental Findings — Clinical Decision Framework

Usually benign: small ganglionic cyst dorsal to MTP joint; mild periarticular soft tissue oedema in non-symptomatic toe; minor age-related subchondral changes.

May require clinical correlation: sesamoid bipartite variant with mild bone marrow signal — may represent symptomatic vs. asymptomatic variant; mild plantar plate signal increase without macroscopic tear — may represent early degeneration or magic angle; Morton's neuroma-sized intermetatarsal soft tissue focus at the base of the toes (full Morton's assessment requires forefoot protocol).

Require explicit communication: unexpected aggressive bone lesion at phalangeal level (cortical destruction, soft tissue mass component); unexpected widespread osteomyelitis in a patient referred for plantar plate assessment; unexpected complete sesamoid dislocation not mentioned in clinical history.

8. MRI Technologist Pearls

8.1 Sequence Order Logic

1. Three-plane body localiser
2. Dedicated toe localiser (low-resolution coronal + sagittal) ← mandatory planning step
3. Coronal PD-FS ← plantar plate assessment; primary sequence; first while patient most compliant
4. Sagittal PD-FS ← plantar plate profile, flexor tendons, IP joints
5. Axial PD-FS ← cross-sectional anatomy, collateral ligaments
6. Coronal T1 ← bone marrow anatomy
7. STIR ← bone marrow oedema screen; before contrast if used

8.2 Positioning Tricks

For the great toe (hallux) examination: the hallux naturally deviates medially in hallux valgus. Plan the hallux coronal perpendicular to the first metatarsal long axis — not to the hallux phalanx axis, which is deviated. The plantar plate is on the metatarsal head side of the joint, so the coronal plane must be perpendicular to the metatarsal head axis.

For plantar plate-focused examination of the second MTP joint: centre the coil over the second metatarsal head specifically; foam pad the first and third toes away from the second toe to prevent contact partial volume.

For glomus tumour of the great toe subungual region: centre the coil and the FOV on the distal phalanx tip — not on the MTP joint level. The target structure is 2–5 mm at the nail bed; the FOV should be 4–6 cm to maximise resolution at this small target.

8.3 Fast Salvage Protocol

Three sequences in approximately 10 minutes provide the minimum clinically interpretable toe MRI. T1 and axial plane can be added if the patient recovers compliance.

8.4 Common Avoidable Errors

9. Quality Control Checklist

• [ ] Dedicated toe localiser acquired before diagnostic sequences
• [ ] Coronal planes perpendicular to metatarsal long axis (verified on sagittal localiser)
• [ ] Hallux separately planned if hallux is the clinical target
• [ ] MTP plantar plate insertion zone included in coronal coverage
• [ ] Distal phalanges included in coverage for osteomyelitis/glomus tumour assessment if relevant
• [ ] Adjacent toes not in contact with target toe
• [ ] Fat suppression uniform across full FOV including distal phalanges — no regional failure
• [ ] STIR acquired before gadolinium injection
• [ ] Post-contrast T1 acquired at appropriate timing (if used)
• [ ] Motion artefacts assessed on coronal PD-FS before ending examination
• [ ] Correct laterality and toe identity labelled
• [ ] All five mandatory sequences completed

11. Evidence Gaps and Ongoing Debate

Plantar plate grading system validation: the Coughlin/Nery grading system for plantar plate tears was originally described for surgical-macroscopic appearance. Its MRI correlate has been validated in small case series with surgical reference standards, but prospective multicentre validation with standardised MRI protocol and grading interobserver reliability data is lacking.

Resolution threshold for plantar plate grade discrimination: no prospective study has formally established the minimum in-plane resolution required to reliably discriminate plantar plate grade 1 (signal change) from grade 2 (partial distal tear) on MRI. The 0.2–0.3 mm recommendation is based on expert practice and the known anatomy rather than controlled resolution threshold data.

3D isotropic vs 2D optimised for toe plantar plate: the comparative diagnostic performance of 3D isotropic PD-FS (0.3 mm isotropic) versus 2D optimised PD-FS (0.2 mm in-plane, 2 mm slice) for plantar plate tear grading with surgical reference has not been formally evaluated.

DWI role in toe osteomyelitis differentiation: preliminary data suggest DWI may help differentiate toe osteomyelitis from Charcot change or sterile inflammation, but formal prospective validation for this specific anatomical location at the required spatial resolution is lacking.

AI reconstruction for small extremity MRI: identical gap as documented in the MRI Fingers page — DLR has not been specifically validated for sub-0.3 mm in-plane resolution toe MRI. The risk of smoothing artefacts at this resolution is real and not yet characterised.

Hallux vs lesser toe protocol standardisation: no society guideline specifies the standard protocol for toe MRI. The technical parameters described in this page are based on expert practice and technical extrapolation from finger MRI evidence [1, 3].

12. Evidence-Based References

A. Guidelines / Consensus / Society Recommendations

(No dedicated society guidelines exist for toe MRI protocol design. The evidence base consists of technical papers, anatomical studies, and extrapolation from small extremity imaging principles.)

B. Systematic Reviews / Meta-analyses

(No dedicated systematic reviews address toe MRI technical protocol.)

C. Important Prospective / Original Studies

D. Technical MRI Papers

E. Landmark Historical References

End of document — MRI Toes Generic Standard Protocol — MRIninja v1.0 — May 2026

This master page is the reference for all future toe MRI child pages including: plantar plate tear (grading and surgical planning); turf toe (first MTP capsular-ligamentous injury); sesamoid pathology (fracture, AVN, bipartition); diabetic toe osteomyelitis; inflammatory arthropathy (RA, PSA, gout) MTP/IP joint; glomus tumour of the toe; Morton's neuroma forefoot protocol.