From Origins to Ultrasound: The Evolution of Femoral Region Blocks

Why These Blocks Matter

Regional anesthesia in the femoral region has undergone a remarkable transformation from landmark-based techniques to precision-guided ultrasound blocks that optimize pain control, preserve motor function, and improves patient satisfaction. Here we explore four cornerstone blocks of the femoral region.

• Femoral Nerve Block

• Fascia Iliaca Compartment Block

• Lateral Femoral Cutaneous Nerve (LFCN) Block

• Pericapsular Nerve Group (PENG) Block

Each block is unpacked through its historical context, anatomical targets, procedural rationale, and modern ultrasound-guided technique with illustrations that clarify the endpoint injection goals.

Historical Timeline of Development

Year	Milestone
Pre-2000s	Femoral and LFCN blocks widely used for anterior thigh and lateral hip pain
2001–2010	Fascia Iliaca block introduced to broaden coverage with simpler landmark technique
2018	PENG block developed by Girón-Arango et al. to target hip articular branches with motor-sparing precision
2020–2025	Ultrasound validation, cadaveric studies, and ERAS integration elevate all four blocks into multimodal pain strategies

Block-by-Block Breakdown

Femoral Nerve Block

Purpose: Anterior thigh and knee analgesia

Historical Role: One of the earliest regional blocks for lower extremity surgery

Target: Femoral nerve beneath fascia iliaca, lateral to femoral artery

Indications: ACL repair, total knee arthroplasty, anterior hip procedures

Modern Use: Often paired with obturator block for complete hip coverage

Ultrasound Tip: Identify femoral artery, vein, and nerve in transverse view; inject lateral to artery under fascia iliaca

Fascia Iliaca Compartment Block (FICB)

Purpose: Broader sensory coverage with simplified technique

Historical Role: Developed to anesthetize femoral, LFCN, and partial obturator nerves via compartment spread

Target: Space beneath fascia iliaca, above iliopsoas muscle

Indications: Hip fracture, ER analgesia, preoperative pain control

Modern Use: Suprainguinal approach improves spread and reliability

Ultrasound Tip: Visualize iliopsoas and fascia iliaca; inject above muscle belly for optimal spread

Lateral Femoral Cutaneous Nerve (LFCN) Block

Purpose: Lateral thigh analgesia and treatment of meralgia paresthetica

Historical Role: Used for isolated lateral thigh pain and as adjunct in hip procedures

Target: LFCN as it passes under fascia lata near ASIS

Indications: Hip arthroscopy, lateral incisions, nerve entrapment syndromes

Modern Use: Paired with PENG or iliopsoas plane block for full hip capsule coverage

Ultrasound Tip: Locate sartorius and tensor fascia lata; inject between muscle layers near ASIS

Pericapsular Nerve Group (PENG) Block

Purpose: Motor-sparing hip analgesia targeting articular branches

Historical Role: Introduced in 2018 to fill gaps left by femoral and fascia iliaca blocks

Target: Articular branches of femoral, obturator, and accessory obturator nerves near iliopubic eminence

Indications: Hip fracture, total hip arthroplasty, geriatric ERAS protocols

Modern Use: Often paired with LFCN block for complete coverage

Ultrasound Tip: Identify iliopubic eminence, psoas tendon, and acetabulum; inject between psoas and pubic ramus

Comparative Table: Choosing the Right Block

Block	Coverage	Motor Impact	Best Use	Pairing Potential
PENG	Articular branches (femoral, obturator, accessory obturator)	Minimal	Hip fracture, arthroplasty	LFCN, iliopsoas plane
Femoral	Femoral nerve	High	Knee surgery, anterior hip	Obturator block
Fascia Iliaca	Femoral, LFCN, partial obturator	Moderate	Hip fracture, ER use	Obturator block
LFCN	Lateral thigh	None	Meralgia paresthetica, lateral hip	PENG, iliopsoas plane

Success Comparison Table: Clinical Outcomes by Block

Block	Study Population	Success Rate (Analgesia)	Motor-Sparing	Opioid Reduction	Patient Satisfaction
PENG Vetrone et al., 2024	60 patients undergoing hip arthroplasty	93% excellent pain relief within 30 min	95% preserved quadriceps strength	40–60% reduction	4.8/5 average satisfaction
Femoral Ying et al., 2023	80 patients post-ACL or hip surgery	85% moderate to strong analgesia	30% experienced quadriceps weakness	25–35% reduction	4.2/5
Fascia Iliaca Smruthi et al., 2023	100 patients with hip fractures	88% good analgesia within 1 hour	60% motor-sparing (suprainguinal)	30–50% reduction	4.3/5
LFCN  Liu et al., 2024	40 patients with lateral thigh pain or hip arthroscopy	65% localized pain relief	100% motor-sparing	Minimal impact	3.9/5

Final Takeaway: When to Choose What

Choose PENG when:

• You need motor-sparing hip analgesia

• Obturator coverage is critical

• Early mobilization is a priority

Choose Femoral when:

• Anterior thigh or knee surgery is planned

• Motor block is acceptable

Choose Fascia Iliaca when:

• Broad sensory coverage is needed quickly

• ER or pre-op settings demand simplicity

Choose LFCN when:

• Lateral thigh pain predominates

• You’re supplementing hip capsule coverage

Continuing Education: From Reluctance to Mastery

Whether you're a student just starting out or a seasoned physician adapting to ultrasound-guided regional anesthesia (UGRA), mastery comes from:

• Hands-on simulation with tactile feedback

• Ultrasound anatomy training using real-time imaging

• Peer-reviewed technique reviews

• Mentorship and repetition

Valkyrie Simulators are designed to bridge the gap, offering realism, clarity, and confidence for every learner.