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Reading File

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Finding Sources

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Question 1 — Morton's Neuroma (Interdigital Neuritis)

b. Working Clinical Diagnosis (1 Mark)

Morton's Neuroma (Interdigital Neuritis) — 3rd/4th web space, left foot

This is a compressive neuropathy/perineural fibrosis of the common plantar digital nerve at the 3rd intermetatarsal space. The presentation is classic: middle-aged obese female, burning pain in the 3rd/4th intermetatarsal space radiating distally into the 3rd and 4th digits, worsened by wearing tight dress shoes (narrow toe box). — Miller's Review of Orthopaedics, 9th Edition

a. Assessment and Management Plan (8 Marks)

Assessment

History features supporting the diagnosis:

55-year-old female (higher predilection in females, likely related to footwear with forced plantar flexion of metatarsal heads)
Burning sensation in the 3rd/4th intermetatarsal space radiating distally — >60% of patients report pain radiating into the toe distally
Narrow dress shoes (exacerbates symptoms due to compression and narrow toe box)
Obesity (increases forefoot loading)
3 months duration (subacute/chronic course typical)

Physical Examination:

Palpation between and just distal to the metatarsal heads — elicits plantar tenderness
Mulder's Sign (pathognomonic): Compress the medial and lateral forefoot simultaneously while palpating the web space — reproduces pain and may elicit a palpable/audible "click" as the neuroma is displaced
Assess for numbness between 3rd/4th toes (reported in ~40% of patients)
Rule out metatarsalgia, MTP synovitis, stress fracture, and plantar plate tear

Investigations:

Weight-bearing plain X-rays — to rule out bony pathology, deformity, stress fracture
Ultrasound or MRI — not mandatory for diagnosis but can confirm an oval hypoechoic mass plantar to the transverse intermetatarsal ligament if clinical picture is unclear; also differentiates from intermetatarsal bursitis
Neurovascular assessment of the lower limb (given obesity and sedentary lifestyle — screen for peripheral vascular disease and neuropathy)

Management Plan

Conservative (First-line):

Footwear modification — most important and effective intervention
- Avoid high heels and narrow toe boxes
- Switch to wider, lower-heeled shoes with a deep toe box
- This directly addresses the primary aggravating factor (dress shoes)
Metatarsal pads — placed proximal to the point of maximum tenderness
- Spreads/decompresses the metatarsal heads during weight-bearing
- Widens the intermetatarsal space, indirectly decompressing the nerve
Weight management — obesity increases forefoot loading; referral for dietary/lifestyle support
Activity modification — reduce prolonged standing/walking in aggravating footwear
Corticosteroid injection — moderate effectiveness (~50% report short-term relief)
- Useful if conservative measures fail after 4–6 weeks
- Caution: repetitive injections can cause hammer-toe deformity
- Alcohol sclerosing injections are NOT recommended (unproven)

Surgical (if conservative fails after 3–6 months):

Neuroma excision — dorsal approach most common; transverse intermetatarsal ligament is incised; common digital nerve is resected 2–3 cm proximal to the intermetatarsal ligament
Plantar approach reduces risk of missed excision
Overall surgical success rate ~80%
Main complication: stump neuroma

— Miller's Review of Orthopaedics, 9th Edition; Gray's Anatomy for Students

c. Gait Alterations (3 Marks)

Morton's neuroma causes forefoot pain that predictably alters gait mechanics. The following alterations may be observed:

Antalgic gait — The patient reduces time spent on the affected limb during stance phase (shortened stance phase on the left) to minimise pain during forefoot loading.
Reduced push-off / avoidance of toe-off — Pain is aggravated during terminal stance and toe-off when body weight transfers through the metatarsal heads. The patient will toe-off early or supinate the foot to offload the 3rd/4th web space, reducing propulsive force.
Forefoot offloading / lateral weight shift — The patient may shift weight to the lateral border of the foot or heel-walk to avoid bearing weight through the painful intermetatarsal space. This can also manifest as a widened base of gait or abducted toe-out position.

(Additionally: in an obese, sedentary patient, these gait deviations are likely more pronounced due to increased forefoot ground-reaction forces and reduced lower-limb muscle conditioning.)

d. Foot Orthosis Design and Evaluation (5 Marks)

Orthosis Design: Custom Functional Foot Orthosis with Metatarsal Dome/Pad

Type: Semi-rigid or rigid custom moulded foot orthosis (full-length or 3/4 length)

Key Design Features:

Feature	Rationale
Metatarsal dome/pad placed proximal to the 3rd/4th metatarsal heads	Spreads and depresses the metatarsal heads during weight-bearing, widening the intermetatarsal space and decompressing the interdigital nerve
Soft top cover (e.g. PPT or Poron foam)	Cushions the plantar forefoot, reduces impact loading on the metatarsal heads
Medial longitudinal arch support	Controls excessive pronation (which increases transverse intermetatarsal ligament tension and nerve compression during loading)
Heel cup	Controls rearfoot position, reduces midfoot hypermobility
Wide forefoot platform	Accommodates the forefoot without compressing the web spaces (counteracts the narrow toe box of dress shoes)
Accommodative cut-out under the 3rd/4th web space (if very acute)	Directly offloads the painful area

Shoe Prescription: The orthosis must be fitted into a low-heeled shoe with a wide, deep toe box — without this, the orthosis cannot function correctly.

Evaluation of the Orthosis:

Symptom relief: Reduction in burning/pain score (VAS) at follow-up (4–6 weeks)
Mulder's sign reassessed — reduction in provoked pain
Gait re-assessment — improvement in antalgic pattern, restored push-off
Patient-reported outcomes: Comfort during work hours, ability to tolerate dress shoes
Orthosis fit check: Ensure metatarsal pad is positioned proximal (not under) the metatarsal heads; re-cast/adjust if necessary
Footwear assessment: Confirm compatibility with the patient's work shoes; if dress shoes remain incompatible, explore alternative wide-fit professional footwear

— Miller's Review of Orthopaedics, 9th Edition; Gray's Anatomy for Students; Imaging Anatomy Vol. 3

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