- Pauwels (1935) classified intracapsular femoral neck fractures by the angle the fracture line makes with the horizontal plane on an AP radiograph, measured at the level of the fracture.
- Type I is under 30 degrees (compression force predominates), Type II is 30 to 50 degrees (mixed compression and shear), and Type III is over 50 degrees (shear predominates). Higher angles produce greater shear across the fracture and higher rates of nonunion and fixation failure.
- The classification guides fixation choice: low-angle fractures can be managed with parallel screws or a sliding hip screw; high-angle vertical fractures demand fixation that resists shear β such as a valgus-angled implant, an intramedullary device, a calcar-referencing screw arrangement, or primary arthroplasty in older patients.
- Pauwels Type III fractures in young patients are an orthopaedic emergency β urgent anatomical reduction and stable internal fixation to protect the femoral head blood supply.
Pauwels Type I is a fracture line under 30 degrees from the horizontal, Type II is 30 to 50 degrees, and Type III is over 50 degrees. The key principle: higher angle equals more shear equals higher nonunion risk. In an exam viva, always state the angle, the type, and the biomechanical implication β then explain how your fixation counters shear. For a young patient with a Type III fracture, say urgent anatomical reduction and internal fixation; for an elderly patient with the same fracture pattern, consider primary arthroplasty.
The Pauwels Classification System

Pauwels divided femoral neck fractures into three types based on the inclination of the fracture line measured from the horizontal on a standard AP pelvic radiograph.
| Type | Angle from Horizontal | Dominant Force | Healing Prognosis |
|---|---|---|---|
| I | Less than 30 degrees | Compression (axial load) | Favourable β compression promotes healing |
| II | 30 to 50 degrees | Mixed compression and shear | Intermediate β shear begins to jeopardise stability |
| III | Greater than 50 degrees | Shear (vertical force) | Unfavourable β shear displaces the fracture, high nonunion risk |
30-50 RuleThe three angles
To measure the Pauwels angle, draw a horizontal line along the superior margin of the sacral ala or the ischial tuberosity (the pelvis reference), then draw a line along the fracture plane. The angle between them is the Pauwels angle. A more vertical fracture is a higher type with worse prognosis. Always measure on the AP radiograph β the lateral view is used to assess sagittal plane displacement, not the Pauwels angle.
Biomechanics β Why the Angle Matters
The femoral neck is loaded in compression during weight-bearing. A horizontal (low-angle) fracture is held together by axial compressive forces β the same force that drives healing. As the fracture line tilts toward vertical, an increasing component of the load becomes a shear force that slides the proximal fragment downward along the fracture plane.
- Type I (under 30 degrees): Compression across the fracture site exceeds shear. The bone surfaces are pressed together, which promotes stability and union. Standard fixation (cannulated screws or sliding hip screw) works reliably.
- Type II (30 to 50 degrees): Shear is significant. The fracture has a tendency to displace inferoposteriorly. Fixation must provide some shear resistance β parallel cannulated screws placed with a valgus orientation, or a sliding hip screw with a derotation screw.
- Type III (over 50 degrees): Shear dominates over compression. The proximal fragment tends to slide down and medially, causing varus collapse and screw cut-out. Standard parallel screws have a high failure rate. Fixation must actively resist shear: a valgus-angled blade plate, a dynamic hip screw with an anti-rotation screw, a cephalomedullary nail, or β in older patients β primary total hip arthroplasty.
At 30 degrees from horizontal, shear is roughly half the body weight; at 60 degrees, shear exceeds compression. This biomechanical shift is why Type III fractures fail with simple screw fixation β the screws bend or cut out under shear loading rather than being loaded in compression.
Higher shear means greater displacement risk. Each episode of displacement threatens the superior retinacular vessels (posterior superior retinacular artery β the main supply to the femoral head). This is the pathway to avascular necrosis: displacement disrupts blood supply, not the fracture angle itself.
Vertical is VillainAngle climbs, shear climbs, prognosis drops
Fixation Strategy by Pauwels Type
| Pauwels Type | Young Patient (under 60) | Elderly Patient (over 65) |
|---|---|---|
| I (under 30 degrees) | Three parallel cannulated screws in inverted triangle | Cannulated screws or sliding hip screw; consider arthroplasty if displaced or osteoporotic |
| II (30 to 50 degrees) | Cannulated screws with valgus orientation, or sliding hip screw + derotation screw | Sliding hip screw with anti-rotation screw; low threshold for hemi- or total arthroplasty |
| III (over 50 degrees) | Urgent open reduction + valgus-angled blade plate, cephalomedullary nail, or modified screw construct | Primary total hip arthroplasty (cemented or uncemented); hemiarthroplasty if low demand |
A Pauwels Type III fracture in a young patient is an orthopaedic emergency. Urgent anatomical reduction (open if necessary) and stable internal fixation should be performed as soon as the patient is fit for surgery. Every hour of delay increases the risk of AVN. Do not accept a non-anatomical reduction β the blood supply to the femoral head depends on it.
In the exam, if asked about a young patient with a vertical femoral neck fracture, your answer should follow this sequence: (1) recognise it as Pauwels III, (2) state it is an emergency requiring urgent anatomical reduction, (3) describe fixation that resists shear (blade plate, angular-stable construct, or cephalomedullary nail), (4) discuss AVN risk and need for long-term follow-up. For an elderly patient with the same fracture, say primary arthroplasty β the risk of nonunion and re-operation with fixation is too high in osteoporotic bone.
Limitations and Practical Considerations
- Inter-observer reliability is moderate at best. Multiple studies (including those by Beimers and colleagues) have shown that different surgeons measure the Pauwels angle differently on the same radiograph, and the same fracture can shift types with minor rotation of the hip or pelvis.
- The classification is purely biomechanical and does not account for patient age, bone quality, displacement, timing of surgery, or vascularity β all of which influence outcome as much as, or more than, the fracture angle alone.
- Garden and Garden-Pauwels hybrid systems exist. In practice, many surgeons consider displacement (Garden type) alongside the Pauwels angle. A Garden IV (fully displaced) Pauwels I fracture may carry a worse prognosis than a Garden I (undisplaced) Pauwels III fracture treated urgently.
- Modern fixation implants have narrowed the outcome gap between Pauwels types. Locking plates, angular-stable implants, and cephalomedullary nails provide shear resistance that older screw-only constructs could not, so the prognostic difference between Type II and Type III is less dramatic than in Pauwels' original series.
- CT is increasingly used to define the fracture geometry more precisely than plain radiographs, especially in vertically oriented fractures where surgical planning depends on the exact geometry.
Evidence Base
Results of internal fixation of Pauwels type-3 vertical femoral neck fractures
- Multicentre retrospective study of Pauwels Type III vertical femoral neck fractures treated with internal fixation
- Nonunion and fixation failure rates were substantially higher than in lower-angle femoral neck fractures
- Anatomical reduction and angular-stable constructs were associated with better outcomes than parallel screws alone
Osteosynthesis and primary valgus intertrochanteric osteotomy in displaced intracapsular fracture neck of femur with osteoporosis in adults
- Valgus intertrochanteric osteotomy converted shear forces to compressive forces across vertical femoral neck fractures
- Union rates improved significantly with osteotomy combined with internal fixation in displaced fractures
- AVN rates were comparable to internal fixation alone when osteotomy was performed early
Revisiting Pauwels' classification of femoral neck fractures
- Review reaffirming that the Pauwels angle reflects the biomechanical balance between shear and compression at the fracture site
- Higher fracture angles correlate with greater shear forces, higher nonunion rates, and increased fixation failure
- The classification remains clinically useful but should be combined with Garden staging and patient factors for decision-making
The role of the medial plate for Pauwels type III femoral neck fracture: a comparative mechanical study using two fixations with cannulated screws
- Biomechanical cadaver study comparing cannulated screws alone versus cannulated screws with a medial buttress plate for Pauwels Type III fractures
- The medial plate construct significantly increased stiffness and load-to-failure compared with screws alone
- Adding a medial plate counteracted the shear forces that cause varus collapse in vertical fracture patterns
Efficacy of four internal fixation devices on femoral neck fractures in young adults: A systematic review and network meta-analysis
- Network meta-analysis comparing cannulated screws, DHS, femoral neck system, and CCP for young adult femoral neck fractures
- Angular-stable constructs (femoral neck system, CCP) showed lower failure and re-operation rates than parallel cannulated screws
- Urgent reduction and fixation timing were key modifiers of outcome across all implant types
Exam Viva
Practise clinical reasoning and management decisions out loud
βA 32-year-old man is involved in a high-speed motor vehicle collision. Radiographs show a vertical fracture line through the femoral neck, measured at 55 degrees from the horizontal. The fracture is minimally displaced. How do you classify and manage this?β
βA 68-year-old active woman sustains a fall at home. Radiographs show a femoral neck fracture with a Pauwels angle of 60 degrees and the fracture is displaced. She is independent, mobilises with no aids, and has mild osteoporosis (T-score minus 2.5). Discuss your management.β
The three types (angle from horizontal)
- Type I: less than 30 degrees β compression-dominated, favourable healing
- Type II: 30 to 50 degrees β mixed forces, intermediate risk
- Type III: greater than 50 degrees β shear-dominated, high nonunion and AVN risk
Fixation by type
- Type I: parallel cannulated screws or sliding hip screw
- Type II: cannulated screws with valgus orientation or DHS plus derotation screw
- Type III young: urgent anatomical reduction, angular-stable fixation (blade plate, CMN)
- Type III elderly: primary total hip arthroplasty (fixation failure rate too high)
Key principles for the exam
- Higher angle equals more shear equals worse prognosis
- Young Pauwels III is an emergency β urgent reduction, protect retinacular vessels
- Always state angle, type, biomechanical implication, and fixation rationale
- Pauwels measures angle only β combine with Garden (displacement) for full picture
- AVN risk depends on displacement and timing, not the angle alone