What local injection is used for anterior cutaneous entrapment syndrome?

Local Injection for Anterior Cutaneous Nerve Entrapment Syndrome

The standard local injection for anterior cutaneous nerve entrapment syndrome (ACNES) is 1% lidocaine (10 mL) combined with corticosteroid (typically triamcinolone acetonide 10-40 mg/mL) injected into the trigger point just beneath the anterior fascia of the rectus abdominis muscle. 1, 2

Diagnostic and Therapeutic Injection Protocol

Initial Diagnostic Injection

• Start with 1% lidocaine alone (10 mL) as a diagnostic test to confirm ACNES before proceeding to therapeutic injections 1, 2
• The injection should be administered at the point of maximal abdominal wall pain, just beneath the anterior fascia of the rectus abdominis muscle at the lateral border 3, 1
• A successful diagnostic response is defined as ≥50% pain reduction on visual analog scale (VAS) or ≥2 points on verbal rating scale within 15-20 minutes 2
• Approximately 81% of patients demonstrate significant pain reduction after the first diagnostic injection 1

Therapeutic Injection Regimen

• Following positive diagnostic response, proceed with lidocaine plus corticosteroid injections 1
• Use triamcinolone acetonide at concentrations of 10-40 mg/mL, with higher concentrations (40 mg/mL) recommended for more severe cases 4
• Approximately 33% of patients achieve permanent pain relief with injection therapy alone 1

Injection Technique Considerations

Ultrasound-Guided Approach

• Ultrasound-guided transversus abdominis plane (TAP) block can be used as an alternative to landmark-based injection technique 5
• This approach may provide more precise needle placement and potentially longer duration of pain relief 5

Monitoring and Follow-up

• Monitor for local adverse effects including atrophy, pigmentary changes, telangiectasias, and hypertrichosis with repeated corticosteroid injections 4
• Assess for systemic absorption with repeated injections, particularly when using higher corticosteroid doses 4

Treatment Algorithm

1. Confirm clinical diagnosis with positive Carnett test (pain increases with abdominal wall tensing) 5
2. Administer diagnostic injection with 1% lidocaine (10 mL) alone 2
3. Reassess pain 15-20 minutes post-injection using standardized pain scales 2
4. If diagnostic injection successful (≥50% pain reduction), proceed with therapeutic injections combining lidocaine and corticosteroid 1
5. If injection therapy fails after multiple attempts, consider surgical neurectomy (successful in approximately 71% of injection-refractory cases) 1

Important Clinical Pitfalls

• Do not confuse ACNES with intra-abdominal pathology - the syndrome is commonly underdiagnosed and patients often undergo unnecessary invasive diagnostic evaluations 6, 3
• Avoid using saline injections therapeutically - randomized trial evidence demonstrates that pain reduction is based on anesthetic mechanism, not placebo or volume effect 2
• Do not skip the diagnostic lidocaine-only injection - this step confirms the diagnosis and prevents unnecessary corticosteroid exposure in patients who may not have ACNES 2