What is the classification system for neck of femur (femoral neck) fractures?

Femoral Neck Fracture Classification Systems

The Garden classification system remains the most widely used classification for femoral neck fractures, but should be simplified to a two-category system distinguishing only between non-displaced (Garden I/II) and displaced (Garden III/IV) fractures, as the four-stage system has poor interobserver reliability and Garden type I fractures are actually complete fractures on CT imaging. 1, 2, 3, 4

Primary Classification: Garden System (Simplified)

The Garden classification is preferred by 72% of orthopaedic trauma surgeons internationally, but with critical limitations 3:

Two-Category Approach (Recommended)

• Non-displaced fractures (Garden I/II): 96% of surgeons can reliably distinguish these from displaced fractures 3
• Displaced fractures (Garden III/IV): Clear displacement with treatment implications 5

Key Clinical Pitfall: The traditional four-stage Garden classification has poor interobserver agreement (Kappa = 0.39), with only 15% agreement among observers when using all four categories 2. When simplified to displaced versus non-displaced, agreement becomes acceptable (Kappa = 0.68) 2.

Garden Type I Fractures Are a Myth

• All Garden type I fractures classified as "incomplete" on radiographs are actually complete fractures on CT scan (100% in prospective study) 4
• This finding suggests eliminating Garden type I as a separate category, as it represents a radiographic artifact rather than a true incomplete fracture 4
• All such fractures should be treated as complete fractures requiring fixation 4

Alternative Classification: AO/OTA System

The 2018-revised AO Foundation/Orthopaedic Trauma Association classification is increasingly used, particularly with 3-D CT imaging 5:

• 31-B1.1 and 31-B1.2: Valgus impacted femoral neck fractures 6
• Improved interobserver reliability when using CT compared to radiographs alone 5

Pauwels Classification

The Pauwels system classifies fractures based on the angle of the fracture line, which has biomechanical implications 1:

• Helps predict fracture stability and shear forces
• Used in conjunction with Garden classification for treatment planning 1

Advanced Imaging for Classification

CT without contrast improves surgical decision-making and classification accuracy 5:

• CT altered surgical decisions in 21% of non-displaced femoral neck fractures (odds ratio 1.4 for choosing arthroplasty) 5
• However, CT did not improve interobserver agreement for Garden classification itself 5
• CT is most valuable for measuring specific angles (impaction angle >135° predicts secondary displacement with odds ratio 11.73) 5

Critical Angles on CT

• Femoral neck impaction angle (coronal plane): >135° predicts secondary displacement 5
• Posterior tilt angle (axial plane): >7.5° predicts conservative treatment failure 6
• Retroversion: >12.5° predicts conservative treatment failure 6

Clinical Application for Treatment Decisions

The primary treatment-relevant distinction is displaced versus non-displaced 5:

Displaced (Unstable) Fractures

• Arthroplasty is strongly recommended over fixation 5
• Choice between hemiarthroplasty and total hip arthroplasty based on patient selection 5

Non-displaced (Stable) Fractures

• Internal fixation, hemiarthroplasty, or conservative care may be considered 5
• Conservative treatment viable only with: no medial cortex displacement, posterior tilt <7.5°, retroversion <12.5°, and absence of chronic kidney disease 6

Common Pitfalls

• Avoid relying on four-stage Garden classification for research or clinical communication—only 39% of surgeons believe they can distinguish all four types 3
• Do not assume Garden type I fractures are incomplete—they require the same fixation as other complete fractures 4
• Recognize that standard radiographs have limited sensitivity (30-70%) for detecting femoral neck fractures 7
• Problems persist in distinguishing Garden II from Garden III fractures even among experienced observers 2