Femoral Head Fractures

Femoral head fractures are uncommon, and they almost never happen on their own. They occur almost exclusively with a traumatic hip dislocation, most commonly posterior: 75-90% are associated with a posterior dislocation, and the fracture is made when the head is driven against the acetabular rim as it leaves the socket. Pipkin classified them in 1957, and his scheme is still the one used.

Mechanism. High-energy trauma: motor vehicle accidents (the dashboard injury), falls from height, industrial accidents and, rarely, sport. The classic sequence is a seated occupant with the hip flexed and adducted whose knee strikes the dashboard; the force travels up the femur and produces a posterior dislocation with a head fracture.

What decides the outcome. Time from injury to reduction. While the head is out, the medial femoral circumflex artery, its main blood supply, is stretched and occluded, and the rate of avascular necrosis rises dramatically once the hip has been dislocated for more than 6 hours. Everything else in this topic follows from that fact: reduce first, image properly afterwards, and choose an operation that does not injure what blood supply remains.

The classification. Pipkin divides the injuries by where the fragment lies relative to the fovea. A fragment below the fovea (Type I) has come from the non-weight-bearing part of the head; one above it (Type II) has come from the weight-bearing part. Types III and IV are the more complex injuries with an associated femoral neck fracture or acetabular fracture respectively.

The head. Its superior aspect is the weight-bearing dome, covered by articular cartilage and critical to hip biomechanics; a Pipkin II fragment comes from here. The fovea capitis is the small depression where the ligamentum teres attaches, and it is the landmark on which the classification turns: below the fovea is the non-weight-bearing part of the head.

The blood supply. The medial femoral circumflex artery (MFCA) provides 80% of the head's supply. It arises from the profunda femoris, runs posterior to the femoral neck and gives off the retinacular arteries that enter the head. The lateral femoral circumflex artery supplies the greater trochanter primarily and contributes little to the head. The artery of the ligamentum teres, a branch of the obturator artery, feeds a small area around the fovea; its contribution is variable, significant in 10-20%, and never enough on its own to prevent AVN.

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Why a posterior dislocation threatens the head. The MFCA runs behind the neck, so a head that is displaced posteriorly stretches and kinks it. Prolonged dislocation means ischaemia; reduction relieves the stretch, but if reduction is delayed the damage may already be done. The same anatomy governs the surgeon's choice of approach later, since a posterior exposure crosses an artery that the injury has already compromised.

History. A high-energy injury, severe hip or groin pain, and a leg the patient cannot move and that looks shortened and internally rotated. In the dashboard mechanism the force arrives through the knee and the femur, so look for the injuries that ride with it:

• Knee injuries (PCL, patella fracture)
• Femoral shaft fracture (the floating hip)
• Other pelvic and acetabular fractures
• Sciatic nerve injury

Examination. The posterior dislocation announces itself: the hip is flexed, adducted and internally rotated, the leg is short, the deformity is obvious and the patient cannot move the hip. The neurovascular examination is mandatory, and the sciatic nerve is the structure at stake.

Differential diagnosis. The deformed, painful hip after trauma has a short list, and the post-reduction CT settles most of it.

Before reduction. An AP pelvis radiograph is the first-line investigation: it confirms the dislocation and shows associated fractures. A lateral of the hip helps to assess a posterior dislocation but may be difficult to obtain. Neither is a reason to delay the reduction.

After reduction. AP and lateral radiographs confirm a concentric reduction. Joint-space widening is the sign of an interposed fragment, and the films are checked again for associated fractures.

CT is essential after every hip dislocation once it is reduced. It defines the fracture pattern, finds loose bodies and plans the approach, and the report should document six things:

1. Fragment size (percentage of the head)
2. Fragment location (above or below the fovea)
3. Articular step-off
4. Loose bodies in the joint
5. Associated acetabular fracture
6. Femoral neck integrity

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3D reconstruction helps surgical planning: it shows the orientation of the fragment, the sphericity of the head and the trajectory a screw will need.

MRI has no routine place in the acute setting. Its use comes weeks later, to look for early AVN and to assess cartilage damage.

The order of priorities. Everything is done in this sequence, and the first step is the one that decides the outcome:

1. Urgent reduction, within 6 hours
2. Assess fragment size and location on CT
3. Remove incarcerated fragments and loose bodies
4. Fix weight-bearing fragments
5. Monitor for AVN

The emergency. A dislocated hip is a time emergency. Reduce it in the emergency department if possible, and in theatre if not; do not send the patient for elaborate imaging first. A patient who presents late, beyond 6 hours, is still reduced urgently, accepting that the AVN risk is now higher.

Closed reduction. Under general anaesthesia or deep sedation for muscle relaxation, the Allis manoeuvre:

1. Patient supine
2. Assistant stabilises the pelvis
3. Hip flexed to 90 degrees
4. Axial traction in line with the femur
5. Gentle internal and external rotation
6. Hip adducted initially, then abducted
7. Feel or hear the clunk of reduction

The Bigelow manoeuvre, a circumduction technique, is the alternative if Allis fails. Closed reduction fails when a fragment or soft tissue is interposed in the joint, and a hip that will not reduce closed goes to emergent open reduction.

Who needs an operation. Surgery is required for:

• Pipkin II (a weight-bearing fragment)
• A large Pipkin I fragment (over 20%)
• Loose bodies in the joint
• A non-concentric reduction
• An associated acetabular or femoral neck fracture
• An incarcerated fragment

Pipkin II. The fragment is reduced anatomically and fixed with countersunk screws, restoring articular congruity with every piece of hardware below the cartilage surface. Anatomic reduction is what the outcome depends on.

Pipkin III. The neck fracture takes priority. In the young patient it is fixed urgently and the head fracture is addressed second, often through combined approaches, accepting a high failure and AVN rate. In the elderly patient a total hip arthroplasty gives a better functional outcome and avoids prolonged immobilisation.

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Pipkin IV. Two surgical problems, staged: the acetabular fracture is usually fixed first, through a posterior approach, and the head fragment through an anterior approach. These injuries need careful surgical planning.

Choosing the approach. The classic teaching is an anterior approach after a posterior dislocation, so that the exposure does not cross the posterior blood supply the injury has already compromised; after an anterior dislocation the posterior approach gives direct access.

The evidence for that rule is thinner than the rule suggests. Stannard's 26-patient series found a 3.2-fold higher osteonecrosis rate with the Kocher-Langenbeck approach than with Smith-Petersen, but the approach was not randomised and the worse injuries went posterior. The Wang meta-analysis of five case-control studies of Pipkin I-II fractures found no difference in osteonecrosis, function or arthritis between approaches, and less heterotopic ossification after the posterior approach. The defensible position is to choose by fracture location and associated injuries, to add heterotopic ossification prophylaxis when the approach is anterior, and not to let a single small series decide.

Avascular necrosis. The rate by Pipkin type is in the outcomes table below; Type III carries the highest. Beyond the type, the risk rises with:

• Dislocation time, the most important factor
• Multiple reduction attempts
• Severity of the initial injury
• Age, higher in older patients

Established AVN is managed conservatively at first if asymptomatic, by core decompression in its early stages, and by total hip arthroplasty when advanced; in the young patient joint preservation is considered.

Post-traumatic arthritis. Develops in 20-50% at 10 years, and may progress despite a good initial result. It follows residual articular incongruity, cartilage damage at the moment of injury, AVN and retained loose bodies. Treatment runs from activity modification, NSAIDs and intra-articular injections to total hip arthroplasty at end stage.

Heterotopic ossification. More likely after delayed surgery, extensive soft-tissue trauma, in men and after head injury. Prophylaxis:

• Indometacin 75mg daily for 6 weeks
• Single-dose radiation (700 cGy)
• Low-dose radiation for the high-risk patient

Sciatic nerve injury. Most palsies recover after reduction, the peroneal division doing worse than the tibial. If there is no recovery, EMG at 3-4 weeks.

Recurrent dislocation. Rare, and usually the consequence of a malreduced posterior wall; it may need revision fixation.

The first two weeks. On the day of surgery: an abduction pillow or wedge, DVT prophylaxis with enoxaparin, analgesia and hip precautions if needed. Over the first fortnight the wound is checked, weight-bearing is protected at toe-touch, gentle range-of-motion exercises begin and DVT prophylaxis continues. Early mobilisation reduces the DVT risk.

Weight-bearing. The timeline is individualised to the Pipkin type, the stability of the fixation, radiographic healing and the associated injuries:

• Weeks 0-6: toe-touch weight-bearing
• Weeks 6-8: partial weight-bearing (50%)
• Weeks 8-12: progressive to full
• Week 12 onwards: full weight-bearing

Rehabilitation. The early phase (0-6 weeks) is passive range of motion, isometric strengthening and gait training with an aid, avoiding hip flexion beyond 90 degrees. The late phase (6-12 weeks) progresses to active range of motion and strengthening, pool therapy once the wound has healed, and a gradual return to activities. High-impact activity is avoided for a minimum of 6 months.

Follow-up. AVN may appear up to 2 years after the injury, so the follow-up is long: AP and lateral radiographs at 6 weeks, then radiographs at 3, 6 and 12 months, and a final assessment at 2 years. Serial films are read for collapse, MRI is requested if symptoms suggest AVN, and intervention is early if it is found.

What predicts a good result. Reduction within 6 hours, a Pipkin I with a small fragment, an anatomic reduction, a young patient and no associated fractures.

What predicts a poor one. Reduction delayed beyond 12 hours, a Pipkin III pattern or an associated neck fracture, a non-anatomic reduction and multiple reduction attempts.

Return to function. Most patients return to their daily activities. High-impact activity is often limited, athletes may struggle to return to sport, and some patients need their occupation modified.

Global Epidemiology

Femoral head fractures are rare injuries that occur almost exclusively after high-energy posterior hip dislocation, most often from motor vehicle dashboard injuries or falls from height. The contemporary EFORT narrative review (Menger et al., 2021) confirms they remain uncommon and are still classified worldwide using the 1957 Pipkin system, with osteonecrosis, post-traumatic arthritis and heterotopic ossification as the principal drivers of poorer long-term outcome.

Side-by-Side Guidance and Evidence

Registry and Pooled Evidence

Because femoral head fractures are rare, no national joint registry isolates them as a discrete cohort; registry data (AOANJRR in Australia, NJR in England and Wales, AJRR in the United States) inform only the salvage arthroplasty pathway for Pipkin III injuries and post-traumatic arthritis. The highest-level synthesis comes from pooled studies: a meta-analysis of Pipkin I-II fractures found the posterior approach reduced heterotopic ossification without affecting osteonecrosis (Wang et al., 2016), while a systematic review of surgical hip dislocation reported osteonecrosis in 12%, heterotopic ossification in 25% and osteoarthritis in 16% (Khalifa et al., 2021).

Practice Variation

• Approach: North American and many European units favour the anterior (Smith-Petersen) approach after posterior dislocation to protect the medial femoral circumflex artery; others prefer the Ganz surgical hip dislocation for full articular visualisation, accepting trochanteric osteotomy-related risk.
• Heterotopic ossification prophylaxis: more routinely used after anterior and extensile approaches; indometacin or single-dose radiotherapy regimens vary by region.
• Salvage in the elderly: primary total hip arthroplasty for Pipkin III in older patients is widely accepted internationally, reflecting the very high osteonecrosis risk of combined head-and-neck injuries.
• Standard trauma pathway: in major trauma centres internationally, femoral head fractures are managed with emergent reduction within 6 hours under general anaesthesia, universal post-reduction CT, and protocolised rehabilitation according to fracture pattern and fixation.

Exam Day Cheat Sheet

Quick Reference: Key Numbers

Pipkin Summary Table