High-yield overview
Femoral head fracture classification for posterior hip dislocation
4 typesbased on fragment location relative to the fovea and associated fractures
Type I / IIinfrafoveal (non-weight-bearing) vs suprafoveal (weight-bearing dome)
Type IIIany femoral head fracture PLUS femoral neck fracture — highest AVN risk
Type IVany femoral head fracture PLUS acetabular posterior wall fracture
Critical Must-Knows
- Pipkin classifies femoral head fractures that occur with posterior dislocation of the hip (typically a dashboard injury) and the classification guides both surgical approach and prognosis.
- Type I is infrafoveal (below the fovea, non-weight-bearing); Type II is suprafoveal (above the fovea, weight-bearing dome). The foveal boundary determines whether the articulating surface is involved and changes the threshold for operative fixation.
- Type III adds a femoral neck fracture and carries the highest AVN risk because the retinacular vessels supplying the femoral head are disrupted at the neck. Type IV adds an acetabular posterior wall fracture requiring a different surgical approach.
- Urgent closed reduction of the dislocated hip is the first priority in every case. The Pipkin type is assigned after reduction and CT scanning — never before.
Clinical Pearls
- “The fovea capitis is the dividing line — Type I (below) does not involve the weight-bearing surface, Type II (above) does
- “Reduce the hip first, then classify on CT — never assign a Pipkin type from the injury film
- “Anterior approach for the head fragment, posterior for the wall, Ganz when you need both
- “Time to reduction (under 6 hours) is the single most modifiable AVN risk factor
The sequence examiners expect
Always state: reduce the hip first, then classify. After successful closed reduction obtain a CT scan (2 mm cuts through the hip joint) to classify the Pipkin type, assess joint congruity, identify loose bodies, and check for an associated femoral neck or acetabular fracture. A non-concentric reduction after closed reduction is an indication for urgent open surgery regardless of the Pipkin type.
The Pipkin Classification
The Pipkin classification applies to femoral head fractures sustained during posterior dislocation of the hip — most commonly a dashboard-type injury in a road traffic collision. Each type is defined by the fracture fragment's relationship to the fovea capitis and the presence of associated femoral neck or acetabular fractures.
| Type | Definition | Weight-Bearing Surface | Key Feature |
|---|---|---|---|
| I | Infrafoveal fracture (below fovea capitis) | Not involved | Small fragment sheared off during dislocation; attached to ligamentum teres |
| II | Suprafoveal fracture (above fovea capitis) | Involved | Fragment includes the weight-bearing dome; articular congruity depends on its reduction |
| III | Type I or II PLUS femoral neck fracture | Variable | Highest AVN risk — retinacular vessels disrupted at the neck |
| IV | Type I or II PLUS acetabular posterior wall fracture | Variable | Fracture-dislocation complex; posterior wall must be addressed surgically |
Mnemonic
One-Below, Two-Above, Three-Neck, Four-WallThe four Pipkin types
B
Below the fovea — infrafoveal, non-weight-bearing
A
Above the fovea — suprafoveal, weight-bearing dome
A
Adds a Neck fracture — femoral neck, highest AVN risk
A
Adds a Wall fracture — acetabular posterior wall
Hook:1-Below, 2-Above, 3-Neck, 4-Wall — numbers climb from simple to complex
Clinical Pearl
The fovea capitis is the dividing line. Below the fovea (Type I), the fragment does not articulate with the acetabulum — it is attached to the ligamentum teres and is often small. Above the fovea (Type II), the fragment is part of the weight-bearing dome and even a small step-off will affect joint mechanics. Examiners test whether you understand that a Type II fragment demands a lower threshold for operative fixation because the articulating surface is at stake.
Management and Surgical Decision-Making
Definitive management depends on the Pipkin type, fragment size and displacement, joint congruity after reduction, the presence of loose bodies, and the patient's age and functional demands.
| Pipkin Type | Non-Operative Criteria | Operative Indication | Preferred Surgical Approach |
|---|---|---|---|
| I | Congruent reduction, small fragment, no loose bodies, hip stable | Incongruent reduction, loose bodies in joint, fragment incarcerated | Anterior (Smith-Petersen) for fragment removal or ORIF |
| II | Rarely non-operative — most require fixation | Displacement greater than 2 mm step-off, any joint incongruity | Anterior (Smith-Petersen) or Ganz surgical dislocation for visualisation |
| III | Rarely non-operative | Young patient with non-displaced neck: ORIF of both; older or displaced: arthroplasty | Anterior for head and neck fixation; consider Ganz for comprehensive access |
| IV | Almost always operative | Posterior wall fixation plus femoral head ORIF | Posterior (Kocher-Langenbeck) for the wall; Ganz if head fragment needs addressing too |
Caution
Closed reduction of the hip is the immediate priority in every Pipkin-type injury. The risk of avascular necrosis rises dramatically if the hip remains dislocated beyond 6 hours. After reduction, confirm concentric reduction on plain films and proceed to CT. Attempt no more than two closed reductions — repeated attempts increase femoral head chondral damage and AVN risk. An irreducible dislocation or a non-concentric reduction after reduction mandates urgent open intervention.
Mnemonic
Head = Anterior, Wall = Posterior, Both = GanzSurgical approach selection
A
Anterior — Smith-Petersen, preserves posterior blood supply from MFCA
P
Posterior — Kocher-Langenbeck for acetabular posterior wall fixation
G
Ganz surgical dislocation — trochanteric flip osteotomy, comprehensive access to both articular surfaces
Hook:Head is Anterior (protects MFCA), Wall is Posterior (KL approach), Both needs Ganz surgical dislocation
Complications and Pitfalls
- Avascular necrosis (AVN) is the most significant complication. Risk factors include delay to reduction beyond 6 hours, severity of initial displacement, Type III injuries (femoral neck fracture disrupts the retinacular vessel arcade), and repeated closed reduction attempts. Reported AVN rates range from 10 to 25 percent in Types I and II and exceed 30 percent in Type III. Time to reduction is the single most modifiable risk factor.
- Post-traumatic osteoarthritis develops in up to half of patients long-term, driven by chondral damage sustained at the moment of dislocation, residual articular step-off, or late AVN collapse. Accurate anatomical reduction of the femoral head fragment is the main surgeon-controlled variable.
- Heterotopic ossification (HO) is common after operative management, particularly through a posterior approach or Ganz surgical dislocation (reported in 20 to 50 percent of operatively treated cases). Prophylaxis with indomethacin (25 mg three times daily for 3 to 6 weeks) or single-fraction radiation (700 cGy within 72 hours of surgery) is routinely recommended.
- Sciatic nerve injury occurs in 10 to 20 percent of posterior fracture-dislocations, typically a neuropraxia of the peroneal division. Document neurovascular status before and after reduction. Most resolve within 6 to 12 months but a complete palsy at presentation warrants discussion of prognosis.
- Missed injuries — always check for an associated femoral neck fracture on CT, which may be occult on plain films. A missed femoral neck fracture converts a Type I or II to a Type III and fundamentally changes management. Also screen for knee injuries (dashboard mechanism causes PCL tears and patella fractures).
- Loose bodies in the joint after reduction prevent concentric reduction and cause early post-traumatic arthropathy. They are an absolute indication for surgical removal (arthrotomy or hip arthroscopy) regardless of the Pipkin type.
Mnemonic
Time — Type — Trauma — TechniqueAVN risk factors after hip dislocation
R
Reduction beyond 6 hours significantly increases AVN — most modifiable factor
T
Type III injuries — femoral neck fracture disrupts lateral epiphyseal artery and retinacular vessels
H
Higher-energy mechanism causes greater vascular insult at the moment of impact
R
Repeated forceful closed reductions and posterior surgical approach may further damage the MFCA
Hook:The 4 Ts of AVN: Time to reduction, Type III, Trauma severity, Technique of reduction
Evidence Base
Evidence
Treatment of grade IV fracture-dislocation of the hip
Pipkin G • J Bone Joint Surg Am (1957)
Key Findings:
- Original four-type classification of femoral head fractures associated with posterior hip dislocation
- Defined the fovea capitis as the key anatomical landmark separating Type I (infrafoveal) from Type II (suprafoveal)
- Emphasised urgency of hip reduction and recommended open treatment for displaced fragments
Clinical implication: Established the classification system that remains the international standard for describing femoral head fractures in the setting of posterior hip dislocation.
Limitation: Small case series, no long-term follow-up data, pre-CT era.
Source: J Bone Joint Surg Am 1957;39-A(5):1027-42
Evidence
Fractures of the femoral head
Brumback RJ, Kenzora JE, Levitt LE, Burgess AR, Poka A • The Hip (1987)
Key Findings:
- Refined Pipkin's classification with specific treatment recommendations for each type
- Advocated anterior surgical approach for isolated femoral head fractures to preserve posterior blood supply
- Demonstrated superior results with anatomical reduction and internal fixation compared with excision of large weight-bearing fragments
Clinical implication: Established the anterior approach as standard for isolated femoral head ORIF and clarified that large suprafoveal fragments must not be excised.
Limitation: Retrospective case series with heterogeneous treatment protocols and no control group.
Source: The Hip 1987:181-206
Evidence
Intermediate-term experience of Pipkin fracture-dislocations of the hip
Marchetti ME, Steinberg GG, Coumas JM • J Orthop Trauma (1996)
Key Findings:
- Anatomical reduction achieved within 24 hours correlated with significantly better long-term clinical outcomes
- Type III injuries had the poorest prognosis driven by high AVN rates
- Quality of articular reduction was the strongest surgeon-controlled predictor of outcome at mean 8-year follow-up
Clinical implication: Supports early, aggressive anatomical reduction and internal fixation, particularly for Types II and III.
Limitation: Retrospective design, relatively small cohort, mixed operative approaches.
Source: J Orthop Trauma 1996;10(7):455-61
Exam Viva
Practise clinical reasoning and management decisions out loud
Viva scenarioStandard
Clinical prompt
“A 32-year-old man is involved in a head-on road traffic collision. His right lower limb is shortened and internally rotated. Radiographs show a posterior dislocation of the right hip with a femoral head fracture fragment visible in the joint. How do you manage this patient?”
Practical approach
This is a posterior fracture-dislocation of the hip — an orthopaedic emergency. My first priority is urgent closed reduction of the hip under sedation or general anaesthesia, ideally within 6 hours of injury, to minimise the risk of avascular necrosis. I would check and document neurovascular status before and after reduction. After successful closed reduction, I would obtain a CT scan of the pelvis with 2 mm cuts through the hip joint to classify the femoral head fracture using the Pipkin system, assess joint congruity, identify loose bodies, and exclude an associated femoral neck or acetabular fracture. If the CT demonstrates a suprafoveal fragment (Pipkin Type II) with greater than 2 mm of articular step-off, I would recommend open reduction and internal fixation via an anterior (Smith-Petersen) approach, which gives direct access to the femoral head fragment while preserving the posterior blood supply from the medial femoral circumflex artery. Post-operatively I would begin protected weight-bearing, prescribe indomethacin for heterotopic ossification prophylaxis, and arrange serial follow-up with MRI at 6 to 12 months to screen for AVN.
Key clinical points
State urgency: closed reduction of the hip within 6 hours to reduce AVN risk
Always classify the Pipkin type AFTER reduction using CT, not from the injury film
Anterior approach for isolated femoral head fracture — protects the medial femoral circumflex artery
Document neurovascular status pre- and post-reduction; counsel the patient about AVN risk and the need for long-term follow-up
Common pitfalls
Attempting to classify the Pipkin type before reducing the hip (reduction is always the first step)
Using a posterior approach for an isolated femoral head fragment without a posterior wall injury (further devascularisation risk)
Forgetting to check for an associated femoral neck fracture on CT (a missed Type III changes management entirely)
Further questions
“What if the hip is irreducible on closed reduction?”
“How would your management differ for a Type IV injury with a displaced posterior wall?”
“What is the role of Ganz surgical dislocation in these injuries?”
Viva scenarioAdvanced
Clinical prompt
“A 55-year-old woman sustains a posterior fracture-dislocation of the hip. After successful closed reduction, CT confirms a Pipkin Type III injury: a suprafoveal femoral head fragment and a minimally displaced femoral neck fracture. How would you manage this?”
Practical approach
A Pipkin Type III injury — a femoral head fracture with an associated femoral neck fracture — carries the highest risk of avascular necrosis because the neck fracture disrupts the retinacular vessels that are the primary blood supply to the femoral head. In this 55-year-old patient, I would discuss two treatment pathways. If the femoral neck fracture is truly non-displaced and the patient has good bone quality, I would attempt open reduction and internal fixation of both fractures: the femoral head fragment with small-diameter countersunk screws (or bioabsorbable screws to facilitate later MRI surveillance) and the femoral neck with cannulated screws or a sliding hip screw. I would use an anterior approach (Smith-Petersen or Watson-Jones) to access the head fragment while preserving the posterior blood supply. However, if the neck fracture is displaced, bone quality is poor, or the patient is lower-demand, I would recommend a total hip arthroplasty — fixation in this scenario has a high rate of failure and AVN, and arthroplasty provides a more predictable functional outcome. In either case, I would counsel the patient extensively about the significant AVN risk even with anatomical fixation and the possibility of requiring a secondary arthroplasty in the future.
Key clinical points
Type III carries the highest AVN risk — the femoral neck fracture disrupts the retinacular blood supply to the femoral head
In younger patients with non-displaced neck fractures, attempt ORIF of both the head fragment and the neck
In older patients or those with displaced neck fractures or poor bone quality, arthroplasty is often the more reliable option
Always counsel the patient about AVN risk and the realistic possibility of future arthroplasty
Common pitfalls
Attempting internal fixation in an older patient with poor bone quality and a displaced femoral neck fracture
Using a posterior approach, which may further compromise the already tenuous femoral head blood supply
Failing to warn the patient about the high probability of AVN and the potential need for further surgery
Further questions
“What specific factors would tip your decision toward arthroplasty over fixation in this patient?”
“How would you monitor for AVN post-operatively, and what is the typical timeline?”
“What is the role of the Ganz surgical dislocation in Type III injuries, and what are its specific risks?”
Exam day cheat sheet
Pipkin Classification — Exam Cheat Sheet
The four types (fovea is the key landmark)
- Type I: infrafoveal, below fovea, non-weight-bearing — non-operative if congruent and no loose bodies
- Type II: suprafoveal, above fovea, weight-bearing dome — ORIF if step-off greater than 2 mm or any incongruity
- Type III: any femoral head fracture PLUS femoral neck fracture — highest AVN risk
- Type IV: any femoral head fracture PLUS acetabular posterior wall fracture — almost always operative
Management sequence (memorise this order)
- Step 1: urgent closed reduction of the hip (within 6 hours) — maximum two attempts
- Step 2: post-reduction CT pelvis (2 mm cuts) for classification and planning
- Step 3: non-concentric reduction or loose bodies = operative, regardless of Pipkin type
- Step 4: approach — anterior for isolated head, posterior for the wall, Ganz for comprehensive access
Complications to know
- AVN: 10–25 percent Types I/II, over 30 percent Type III; time to reduction is the key modifiable factor
- Heterotopic ossification: 20–50 percent after surgery; prophylax with indomethacin or radiation
- Always exclude occult femoral neck fracture on CT (missed Type III changes everything)
- Sciatic nerve (peroneal division) at risk — document pre- and post-reduction status