What is the clinical significance of the blood supply to the femoral neck in different age groups in orthopedics?

Blood Supply of the Femoral Neck Across Age Groups and Clinical Implications

Age-Related Vascular Anatomy and Clinical Significance

The blood supply to the femoral neck is critically important in orthopedics because it directly determines the risk of avascular necrosis (AVN) following femoral neck fractures, with approximately 75% of fractures showing initial vascular compromise, though 80% of these regain blood flow within 6 weeks post-injury. 1

Primary Vascular Architecture

The femoral head receives blood through three interconnected network structures, with the epiphyseal arterial network serving as the most widely distributed and primary vascular structure 2:

• Inferior retinacular artery system: Has the largest caliber compared to other retinacular vessels and demonstrates remarkable resilience, remaining patent in 100% of nondisplaced fractures and 60% of Garden Type III displaced fractures 2
• Superior retinacular arteries: More vulnerable to disruption with fracture displacement 2
• Anterior retinacular arteries: Smaller caliber vessels with limited compensatory capacity 2
• Round ligament artery: Minimal contribution in adults, particularly in elderly patients 2

Critical Clinical Implications by Age Group

Younger Adults (Under 60 Years)

In younger patients, preservation of the femoral head blood supply is paramount because these patients have higher functional demands and longer life expectancy, making AVN particularly devastating 3:

• The epiphyseal arterial network periphery has fewer anastomoses than the central region, making peripheral drilling during internal fixation more likely to cause iatrogenic vascular injury 2
• Surgical technique must prioritize placing implants closer to the central region of the femoral head to avoid disrupting the main stems of epiphyseal arteries located peripherally 2
• Internal fixation with cannulated screws or femoral neck systems can achieve satisfactory outcomes when vascular structures are preserved 3

Elderly Patients (Over 60-80 Years)

For elderly patients with displaced femoral neck fractures, arthroplasty (hemiarthroplasty or total hip arthroplasty) is strongly recommended over internal fixation because the blood supply is frequently compromised and the risk of AVN is unacceptably high 4:

• Approximately 70% of elderly hip fracture patients have ASA physical status 3-4 with multiple comorbidities 4
• Cemented femoral stems are strongly recommended in this population to reduce periprosthetic fracture risk 4
• The choice between hemiarthroplasty and THA should consider functional status: THA provides functional benefit but increases complication risk (moderate recommendation) 4

Temporal Vascular Changes Post-Fracture

Single-point preoperative vascular imaging is unreliable for prognostication because the femoral head undergoes dynamic temporal variations in blood flow following fracture 1:

• Initial assessment shows total vascular loss in approximately 50% of fractures and partial loss in 29% 1
• By 6 weeks post-fixation, 74% of initially avascular femoral heads and 83% of partially avascular heads demonstrate vascular recovery 1
• The 6-week postoperative imaging reliably predicts long-term AVN risk: all patients with persistent avascularity at 6 weeks developed radiographic AVN by 2 years (p<0.001) 1

Surgical Decision-Making Algorithm

For displaced femoral neck fractures, treatment decisions should follow this hierarchy 4:

1. Elderly patients (>60-65 years): Arthroplasty is strongly recommended

   • Use cemented femoral stems (strong recommendation) 4
   • Consider THA over hemiarthroplasty in active patients accepting higher complication risk (moderate recommendation) 4
   • No preferred surgical approach (anterior, lateral, or posterior) 4

2. Younger patients (<60 years): Internal fixation may be attempted

   • Place screws/implants in the central region of the femoral head to protect peripheral epiphyseal arteries 2
   • Recognize that preoperative vascular status does not reliably predict outcome 1
   • Plan for 6-week vascular reassessment to identify patients requiring conversion to arthroplasty 1

3. Nondisplaced fractures: Multiple options exist including internal fixation, hemiarthroplasty, or even nonsurgical care (limited evidence) 4

Intraoperative Blood Supply Protection

The inferior retinacular arterial system and central epiphyseal arterial network are the two most critical structures to preserve during surgery 2:

• Avoid peripheral drilling that disrupts the main stems of epiphyseal arteries 2
• The central region has richer anastomoses and better compensatory capacity 2
• Use tranexamic acid to reduce blood loss (strong recommendation), as elderly patients commonly present with anemia (40%) and experience significant perioperative hemoglobin drops 4

Common Pitfalls

• Avoid relying solely on preoperative vascular imaging to determine treatment, as 80% of initially compromised femoral heads recover blood flow 1
• Do not place internal fixation implants peripherally in the femoral head, as this disrupts critical vascular structures 2
• Recognize that intertrochanteric fractures require more blood transfusion (1.74 vs 1.00 units) than intracapsular fractures 5
• In elderly patients, pre-operative transfusion should be considered if hemoglobin <9 g/dL or <10 g/dL with ischemic heart disease history 4