# Arterial Access: Femoral, Radial, and Brachial Approaches

## Anatomy

### Common Femoral Artery (CFA)

The common femoral artery is the continuation of the external iliac artery as it passes below the inguinal ligament, which itself runs from the anterior superior iliac spine (ASIS) to the pubic tubercle. Typically 2 to 4 cm below the inguinal ligament, the CFA bifurcates into the superficial femoral artery (SFA) and the profunda femoris artery (PFA). The ideal puncture site lies over the medial third of the femoral head on fluoroscopy, within the CFA segment between the inguinal ligament and the bifurcation.

Surrounding the CFA are structures that follow a predictable lateral-to-medial arrangement captured by the mnemonic NAVEL: Nerve, Artery, Vein, Empty space, Lymphatics. The femoral nerve sits laterally while the femoral vein lies medially. An important anatomical landmark is the origin of the inferior epigastric artery, which marks the transition from external iliac to CFA. A puncture above this level risks retroperitoneal hemorrhage because the vessel is no longer compressed against the femoral head.

### Radial Artery

The radial artery arises from the brachial artery at the antecubital fossa and courses laterally along the forearm between the brachioradialis and flexor carpi radialis tendons. It is easily palpable at the wrist just proximal to the scaphoid and trapezium. The hand receives dual blood supply through the superficial and deep palmar arches, with the ulnar artery being the dominant contributor in most patients. Before radial access, an Allen test or Barbeau test (pulse oximetry with plethysmography) should be performed to confirm adequate collateral flow.

### Brachial Artery

The brachial artery is the continuation of the axillary artery beginning at the lower border of the teres major. It runs medially in the arm and lies superficially in the antecubital fossa, where it bifurcates into the radial and ulnar arteries. The median nerve crosses superficial to the brachial artery in the mid-arm. Importantly, the brachial artery has end-artery anatomy, meaning that thrombosis at this site can cause hand ischemia.

## Ultrasound-Guided Access Technique

### General Principles

Real-time ultrasound guidance is the standard of care for arterial access, reducing complications by 50 to 80 percent compared with landmark-based technique. A high-frequency linear transducer (7-12 MHz) is used. The short-axis (transverse) view is most commonly employed for initial puncture, while the long-axis (sagittal) view confirms needle trajectory. A micropuncture system consisting of a 21-gauge needle and 0.018-inch wire is the standard first-line approach for most arterial access.

### Common Femoral Artery Access

The patient is positioned supine with slight external rotation of the hip. Using ultrasound, the operator identifies the CFA above the bifurcation and below the inferior epigastric artery, confirming position over the femoral head with fluoroscopy. There are two principal access directions. In antegrade access, the needle is directed caudally (toward the foot) and is used for ipsilateral lower extremity interventions. This approach is more challenging in obese patients due to the steep angle required and carries a risk of puncturing the SFA or PFA origin. In retrograde access, the needle is directed cephalad (toward the head) and serves as the standard approach for most diagnostic and contralateral interventions. After micropuncture wire insertion, intraluminal position should be confirmed with fluoroscopy before upsizing.

### Radial Artery Access

The patient is positioned supine with the arm extended on an arm board and the wrist hyperextended over a roll. Access is obtained using a 20- or 21-gauge micropuncture needle, entering 1 to 2 cm proximal to the radial styloid. Immediately after access, a radial artery cocktail is administered: nitroglycerin (200 mcg), verapamil (2.5-5 mg), and heparin (2000-5000 units) to prevent spasm and thrombosis. Hydrophilic sheaths are used, typically 5 to 6 Fr for diagnostic cases and up to 7 Fr for interventional procedures. Post-procedure hemostasis is achieved with patent hemostasis using a TR Band or similar compression device.

### Brachial Artery Access

Brachial access is reserved for cases where femoral and radial access are not feasible. The artery is accessed at or just above the antecubital fossa. This site carries a higher complication rate than either femoral or radial approaches, including risks of pseudoaneurysm, thrombosis, and median nerve injury. It should be considered a secondary option and avoided when alternatives exist.

## Choosing the Access Site

| Feature | Femoral | Radial | Brachial |
|---------|---------|--------|----------|
| Max sheath size | 22-24 Fr | 7 Fr (up to 8 Fr described) | 6-7 Fr |
| Post-procedure bed rest | 2-6 hours | None (early ambulation) | 2-4 hours |
| Access site complications | Moderate (pseudoaneurysm, RP hemorrhage, AVF) | Low (radial artery occlusion 2-10%) | Highest (thrombosis, nerve injury) |
| Patient comfort | Lower | Higher | Moderate |
| Vascular territory access | All territories | Most territories (longer catheters needed) | Visceral and thoracic aorta |
| Learning curve | Standard | Longer for IR operators | Standard |
| Key limitation | Bed rest, hostile groins | Small caliber, spasm | End-artery anatomy |

### Femoral Advantages

The femoral artery is a large-caliber vessel that accommodates large sheath sizes (up to 22-24 Fr for endografts). It offers familiar anatomy for most operators and provides access to virtually all vascular territories.

### Femoral Disadvantages

Femoral access requires bed rest post-procedure, typically 2 to 6 hours depending on the closure method employed. There is a higher risk of retroperitoneal hemorrhage, pseudoaneurysm, and arteriovenous fistula formation. Access can be particularly challenging in morbid obesity or in hostile groins from prior surgery, radiation, or infection.

### Radial Advantages

Radial access is associated with reduced access site complications, as demonstrated by the RIVAL and MATRIX trials in cardiology. It permits early ambulation and often same-day discharge, with better patient comfort and preference. Its use is growing in interventional radiology for visceral and peripheral interventions.

### Radial Disadvantages

The smaller caliber of the radial artery limits sheath size (typically a maximum of 7 Fr, though 8 Fr has been described). Radial artery spasm is a common issue, and there is a longer learning curve for IR operators accustomed to femoral access. The approach may also require longer catheters and different catheter shapes.

### Brachial Considerations

Brachial access carries a higher complication rate than both femoral and radial approaches and is used primarily when other sites are inaccessible. It does offer access to the visceral and thoracic aorta from the upper extremity.

## Antegrade vs. Retrograde Femoral Access

### Antegrade CFA Access

Antegrade access is indicated for ipsilateral SFA, popliteal, and tibial interventions. It provides a direct, short working distance to ipsilateral lower extremity targets. The technique requires a steeper entry angle (45-60 degrees), making ultrasound guidance critical to avoid bifurcation puncture. In obese patients, the large pannus can make the approach especially challenging and may require assistant retraction.

### Retrograde CFA Access

Retrograde access is the standard approach for most diagnostic angiography and contralateral interventions. It is used with a crossover technique employing a Balkin sheath or crossover catheter for contralateral limb access. This approach also serves for aortic, visceral, and upper extremity interventions.

## Complications

### Access Site Complications

Hematoma is the most common complication and is usually self-limited with manual compression. Pseudoaneurysm presents as a pulsatile mass with to-and-fro flow on duplex ultrasound and can be treated with ultrasound-guided thrombin injection, manual compression, or surgical repair. Arteriovenous fistula manifests as a continuous bruit and thrill; most will close spontaneously if small, though larger ones may require a covered stent or surgery.

Retroperitoneal hemorrhage results from a high puncture above the inguinal ligament and presents with flank pain, hypotension, and dropping hemoglobin. Diagnosis is made by CT, and management may require embolization or surgical repair. Dissection, characterized by an intimal flap from traumatic access, is usually managed with wire passage and stenting if flow-limiting. Thrombosis is particularly concerning with brachial access and may require thrombolysis or surgical thrombectomy. Radial artery occlusion occurs in 2 to 10 percent of cases but is usually asymptomatic due to dual supply and can be prevented with patent hemostasis technique.

<image>Anatomical illustration of the right common femoral artery region in anterior view, showing the inguinal ligament spanning from ASIS to pubic tubercle, the common femoral artery, its bifurcation into superficial femoral and profunda femoris arteries, the femoral vein medially, and the femoral nerve laterally. The ideal puncture zone is highlighted over the femoral head with a fluoroscopic overlay showing bony landmarks.</image>

<image>Cross-sectional ultrasound illustration of the common femoral artery showing the short-axis view with a micropuncture needle approaching at 45 degrees. Labels identify the femoral artery (round, pulsatile), femoral vein (oval, compressible) medially, and the femoral nerve laterally. The needle tip is shown entering the anterior wall of the artery with a small reverberation artifact.</image>

<image>Illustration of radial artery access at the wrist showing the patient's hand supine on an arm board with wrist hyperextended over a gauze roll. The micropuncture needle enters the radial artery 1-2 cm proximal to the radial styloid. An inset shows the palmar arch anatomy with the ulnar artery providing collateral flow. A TR Band compression device is shown in a separate panel for hemostasis.</image>

<image>Comparative diagram of antegrade versus retrograde common femoral artery access. Two side-by-side illustrations show needle entry angles: retrograde access with the needle directed cephalad at 30-45 degrees, and antegrade access with the needle directed caudally at 45-60 degrees. The CFA, SFA, and profunda femoris bifurcation are labeled, with the femoral head shown as a bony landmark behind the artery.</image>

## Clinical Pearls

Confirming that the CFA puncture is over the femoral head on fluoroscopy is essential. A puncture above this landmark risks retroperitoneal hemorrhage, while one below risks profunda or SFA puncture where closure devices may fail. Ultrasound-guided access is the standard of care, and there is no benefit to a landmark-only technique.

The micropuncture system is a safety net and should always be the starting point unless the device requirements specifically contraindicate it. For radial access, a vasodilator cocktail must be administered immediately after sheath insertion to prevent spasm. Patent hemostasis, which maintains radial artery flow during compression, reduces radial artery occlusion rates.

When uncertain whether antegrade or retrograde access is preferable, retrograde with crossover is the safer default. Finally, every operator should have a plan for managing access site complications before starting the case.

## References

- Defined Practice Standards for Vascular Access, Society of Interventional Radiology (SIR), 2020
- Defined Practice Standards for Femoral Arterial Access, SIR, 2014
- Defined Practice Standards for Radial Arterial Access, SIR, 2019
- Defined Practice Standards for Ultrasound-Guided Vascular Access, AIUM/SIR, 2019
- Defined Practice Standards for Transradial Access in Interventional Radiology, Defined by JVIR consensus panel, 2022
- Defined by the RIVAL Trial (N Engl J Med 2011) and MATRIX Trial (Lancet 2015) for comparative radial vs. femoral outcomes
- Defined by Defined by the FAUST Trial (Defined by Defined Practice Standards for Ultrasound-Guided Femoral Access) for ultrasound guidance evidence