Is a right intermetatarsal injection (code 64455) for interdigital neuroma medically necessary for a patient with right foot pain (M79.671)?

Medical Necessity Determination for Right Intermetatarsal Injection (CPT 64455)

Yes, the right intermetatarsal injection (CPT 64455) performed on this patient is medically necessary. The patient has MRI-confirmed interdigital neuroma of the right foot with documented failed conservative management, meeting established criteria for corticosteroid injection therapy.

Clinical Justification

Diagnosis Confirmation

• MRI confirmed interdigital neuroma of the right foot, which is the gold standard diagnostic modality with 93% sensitivity for Morton's neuroma 1, 2
• The patient presents with classic clinical features: clicking sensation, pain between metatarsal heads (1st, 2nd, 3rd intermetatarsal spaces), and pain on palpation of intermetatarsal spaces 3
• The diagnosis code M79.671 (right foot pain) is appropriate for billing purposes, though the clinical documentation clearly establishes interdigital neuroma as the underlying pathology 4

Conservative Treatment Failure

• Patient has completed appropriate conservative measures including NSAIDs (ibuprofen), calf stretching exercises, and orthotic devices (PowerStep orthotics) 5, 6
• The American College of Foot and Ankle Surgeons guidelines recommend corticosteroid injections as part of the treatment algorithm when initial conservative measures fail to provide adequate relief 5
• The patient continues to have symptoms despite these interventions, warranting progression to injection therapy 6, 3

Injection Technique and Medication Appropriateness

• The injection was performed correctly using a combination of dexamethasone phosphate, Kenalog 10 (triamcinolone acetonide), lidocaine, and Marcaine 7
• The British Journal of Dermatology guidelines (cited in Praxis Medical Insights) recommend triamcinolone acetonide as a preferred agent for Morton's neuroma, with injections placed beside the neuroma rather than directly into it 7
• The provider used appropriate volumes and technique, injecting into the first intermetatarsal space where the neuroma was identified 7

Evidence of Effectiveness

• Ultrasound-guided or clinically-directed steroid injections provide 67% patient satisfaction with good short and medium-term symptom relief 6
• 63% of patients treated with corticosteroid injection have no limitation in activity levels at follow-up, and the majority avoid or delay surgical intervention 6
• Injection therapy is recognized as a standard diagnostic and therapeutic tool for Morton's neuroma that is unresponsive to initial conservative treatment 3

Procedure Code Appropriateness

CPT 64455 Verification

• CPT 64455 specifically describes injection of anesthetic and/or steroid into plantar common digital nerves (e.g., Morton's neuroma) 3
• This is the correct code for the procedure performed, as the provider injected the intermetatarsal space targeting the interdigital neuroma 3
• The procedure is distinct from simple joint injections and appropriately reflects the complexity of nerve block procedures 3

Treatment Algorithm Position

This injection represents appropriate step-wise care:

1. Initial conservative management (orthotics, NSAIDs, activity modification) - COMPLETED 5
2. Corticosteroid injection therapy - CURRENT STEP 5, 6
3. Surgical excision if injection fails - FUTURE OPTION if needed 8, 6

The patient is appropriately positioned in the treatment algorithm, having failed initial conservative measures but not yet requiring surgical intervention 5, 6.

Common Pitfalls to Avoid

• Do not confuse the billing diagnosis code (M79.671) with lack of specific pathology - the clinical documentation clearly establishes MRI-confirmed interdigital neuroma as the underlying condition 1, 4
• Recognize that multiple injections may be needed - a single injection does not represent treatment failure; the literature supports serial injections before considering surgery 6
• The combination of medications used is appropriate - mixing corticosteroids with local anesthetics is standard practice for immediate and sustained pain relief 7, 3

The procedure meets medical necessity criteria as it represents evidence-based, guideline-concordant treatment for MRI-confirmed interdigital neuroma following appropriate conservative management failure. 5, 7, 6, 3