Neck of Femur (NOF) Fracture

Overview

Anatomy and Blood Supply

1. Medial femoral circumflex artery (MFCA) - the dominant supply (~82% of femoral head perfusion). Its deep branch gives off the superior retinacular arteries that run in the retinacula of Weitbrecht along the femoral neck and perforate the bone 2-4 mm from the articular cartilage. These are the vessels most at risk in a subcapital fracture.
2. Lateral femoral circumflex artery (LFCA) - contributes ~18%.
3. Artery of the ligamentum teres (foveal artery) - minor contributor, may become more important in elderly with atherosclerotic disease attenuating the other sources.

Classification

1. Anatomical Location

• Subcapital - most common; highest risk of AVN
• Transcervical - mid-neck
• Basicervical - at the base of the neck; only 2-3% of all hip fractures; variable relationship to the capsule

2. Garden Classification (most widely used)

3. Pauwels Classification

4. OTA/AO Classification

• 31-B1: Nondisplaced to minimally displaced subcapital
• 31-B2: Transcervical (basicervical, midcervical adduction, midcervical shear)
• 31-B3: Displaced nonimpacted subcapital (Garden III/IV)

Clinical Features

• History: Fall (elderly) or high-energy trauma (young). Groin/hip pain. Inability to weight-bear.
• Examination:
  • Shortened limb
  • Externally rotated leg (psoas and adductors acting on detached proximal fragment)
  • Pain on passive rotation
  • Impacted fractures may still allow limited weight-bearing

Investigations

• Plain X-ray pelvis AP + lateral hip: First-line. May miss occult or undisplaced fractures.
• MRI: Gold standard for occult hip fractures (e.g., can show hemarthrosis and undisplaced intracapsular fracture when X-ray is normal). CT is an alternative if MRI unavailable.
• Bloods: FBC, U&E, LFTs, Ca, Mg, vitamin D, glucose, coagulation screen
• ECG, CXR: Pre-operative assessment
• Bone health: Ask about previous fragility fractures and osteoporosis treatment

Preoperative Considerations

• Hb <80 g/L
• Na <120 or >150 mmol/L; K <2.8 or >6.0 mmol/L
• Uncontrolled diabetes
• Acute/uncontrolled left ventricular failure
• Correctable arrhythmia with ventricular rate >120/min

Management

1. Patient age and physiological status (biological age, not chronological)
2. Fracture displacement (Garden I/II vs III/IV)
3. Pre-injury mobility and function

Undisplaced Fractures (Garden I/II)

• Cannulated cannulated screws (3 partially threaded screws) - standard technique
  • Placed in inverted triangle configuration for maximum rotational control
  • A 4th screw (diamond configuration) may be used for significant posterior comminution
  • Goal: anatomic reduction + compression across fracture site
• Sliding hip screw (Dynamic Hip Screw) - alternative, especially for basicervical fractures
• Garden alignment index used to evaluate adequacy of reduction (AP: 160-180°; lateral: ~180°)

Displaced Fractures (Garden III/IV)

• Hemiarthroplasty (femoral head replacement; acetabulum left native) - most common
  • Cemented hemiarthroplasty preferred (lower rate of periprosthetic fracture and better early mobilization)
• Total hip arthroplasty (THA) - for active, well-mobilizing patients with pre-existing acetabular disease or good biological age
  • Better functional outcomes than hemiarthroplasty in active patients, but higher early complication rate
  • Recent evidence (2025 systematic review, PMID 41303766) shows THA carries higher thromboembolic risk than hemiarthroplasty

• Internal fixation with urgent reduction is strongly preferred to preserve the native hip
  • Closed reduction (Whitman technique: traction, abduction, extension, then internal rotation) - attempt 2-3 times maximum
  • Open reduction via Smith-Petersen (anterior) or Watson-Jones (anterolateral) approach if closed fails
  • Capsulotomy is considered in young patients to decompress the intracapsular hematoma and potentially reduce AVN risk (no conclusive proof but done quickly and safely)
  • Fully threaded screws to prevent shortening once compression achieved

Complications

Non-union

• Incidence: ~9% in young patients (higher with Pauwels III)
• Causes: inadequate reduction, poor implant position, AVN, infection
• Treatment: valgus intertrochanteric osteotomy, bone grafting, or conversion to arthroplasty

Avascular Necrosis (AVN) / Osteonecrosis

• Most important complication - results from disruption of retinacular vessels
• Incidence in young patients: ~23% overall; 27% displaced, 14% nondisplaced (meta-analysis of 18 studies)
• May present months to years post-injury with collapse of femoral head
• Treatment: core decompression (early), vascularized fibular graft, or total hip arthroplasty (late)
• Recent meta-analysis (PMID 39581960) found global incidence of AVN in adolescents after femoral neck fracture surgery is significant

Fixation Failure

• Cutout of screws, especially with varus malreduction
• More common with high Pauwels angle fractures

Peri-prosthetic Fracture

• More common with uncemented stems

General Complications

• Delirium (most common postoperative complication in elderly; CAM or 4AT screening recommended)
• VTE (DVT/PE) - prophylaxis mandatory
• Chest infection, urinary tract infection
• Pressure ulcers
• Malnutrition

Postoperative Rehabilitation

• Weight bearing as tolerated from day 1 with a frame - the standard for all frail elderly patients. Elderly patients cannot effectively limit weight-bearing and restricting it leads to rapid deconditioning.
• Physiotherapy mobilization on day 1 postoperatively, at least daily thereafter
• Nutrition supplementation (high-protein)
• Osteoporosis treatment - fragility fracture is a mandatory trigger for bone protection therapy
• Falls assessment to reduce future fracture risk

Special Notes

Recent evidence note: A 2025 systematic review (PMID 41303766) confirms THA carries higher thromboembolic risk than hemiarthroplasty in NOF fracture patients - factor this into the THA-vs-hemiarthroplasty decision in high-VTE-risk patients.