Why is classification of femoral neck fractures using Garden (degree of displacement) and Pauwel (angle of fracture line) classifications necessary?

Why Femoral Neck Fracture Classification is Necessary

Classification of femoral neck fractures using Garden and Pauwels systems has historically been used to guide treatment decisions, but current evidence shows that only the distinction between displaced versus non-displaced fractures reliably predicts outcomes and determines appropriate surgical management.

Primary Treatment-Relevant Classification

The most clinically important classification is the two-category system distinguishing displaced from non-displaced fractures, as this directly determines surgical approach 1:

• Displaced fractures: Arthroplasty is strongly recommended over internal fixation to reduce complications and improve functional outcomes 2
• Non-displaced fractures: Internal fixation, hemiarthroplasty, or conservative care may be considered depending on patient-specific factors 2

The American College of Radiology specifically recommends this simplified two-category approach because the traditional four-stage Garden classification has poor interobserver reliability 1.

Limitations of Traditional Classification Systems

Garden Classification Problems

• Poor reliability: Research demonstrates only moderate interobserver agreement (kappa 0.41) and intraobserver agreement (kappa 0.49) for the Garden system 3
• Frequent misclassification: 38% of fractures initially classified as Garden I were actually Garden II upon careful review, leading to a three-fold higher risk of secondary displacement (RR = 2.8) when misclassified 4
• Not recommended for detailed clinical use: While useful for the basic displaced/non-displaced distinction, Garden classification is unreliable for more granular treatment decisions 3

Pauwels Classification Problems

• Very poor reliability: Demonstrates the lowest interobserver agreement (kappa 0.19) and intraobserver agreement (kappa 0.38) among commonly used systems 3
• No unified measurement standard: Lack of standardized methodology for measuring the Pauwels angle makes the classification unreliable 5
• Not recommended for clinical use: Current evidence does not support using Pauwels classification for treatment decisions 3

Modern Classification Approach

The AO Foundation/Orthopaedic Trauma Association classification with CT imaging is increasingly preferred 1:

• Shows improved interobserver reliability compared to radiograph-based systems 1, 6
• CT without contrast alters surgical decision-making in 21% of non-displaced femoral neck fractures 1, 6
• Allows measurement of specific predictive angles, such as femoral neck impaction angle >135 degrees, which predicts secondary displacement with an odds ratio of 11.73 1, 6

Clinical Algorithm for Classification

1. Initial radiographs (AP pelvis with cross-table lateral) to identify fracture 6
2. Determine displacement status (displaced vs. non-displaced) as primary treatment determinant 1
3. Consider CT without contrast for surgical planning, particularly for:
   • Non-displaced fractures where conservative management is considered 6
   • Measuring impaction angles to predict stability 1
   • Improving surgical decision-making accuracy 6

Common Pitfalls

• Over-reliance on Garden subtypes: The four-stage Garden system should not drive treatment decisions beyond the displaced/non-displaced distinction 1, 3
• Using Pauwels classification: This system lacks reliability and should not guide treatment 3
• Skipping CT in borderline cases: CT improves classification accuracy and predicts fracture stability in non-displaced fractures 1, 6
• Assuming Garden I is stable: Many Garden I fractures are actually Garden II and have significantly higher displacement risk 4