Hip Fractures in the Young Adult

A hip fracture in the young adult almost always means an intracapsular fracture of the femoral neck in a patient under about 60 years of age, usually caused by high-energy trauma such as a road traffic collision or a fall from height. Unlike the fragility hip fracture of the elderly, where arthroplasty is often the answer, the priority in the young adult is to save the native femoral head: urgent anatomical reduction and stable internal fixation, because the fracture threatens the retinacular blood supply and carries a real risk of avascular necrosis (AVN) and non-union. It is treated as a surgical urgency, and it is a classic ST3 Trauma & Orthopaedics interview scenario precisely because the evidence behind "how urgent" and "whether to decompress the capsule" remains contested.

Why is a femoral neck fracture different in a young adult?

The femoral head is supplied predominantly by the retinacular branches of the medial femoral circumflex artery running within the capsule, with minor contributions from the lateral femoral circumflex artery and the artery of the ligamentum teres. A displaced intracapsular fracture can kink, tear or compress these vessels, and the contained haematoma may raise intracapsular pressure above capillary perfusion pressure. In the elderly this dilemma is bypassed by replacing the head; in the young adult, arthroplasty condemns the patient to near-certain revision surgery in their lifetime, so head-preserving fixation is the default and every decision is aimed at protecting head perfusion and achieving union.

Because these are high-energy injuries, the fracture is often vertical and unstable, and associated injuries are common. In particular, an ipsilateral femoral shaft fracture coexists with a femoral neck fracture in a small but important minority of cases and the neck component is easily missed — actively look for it.

How does it present and how is it diagnosed?

• Assessment: manage high-energy cases along ATLS lines; the hip is examined as part of the secondary survey. The classic posture is a shortened, externally rotated limb, but undisplaced fractures may allow weight-bearing.
• Imaging: AP pelvis and lateral hip radiographs first line. In the polytrauma patient, scrutinise the trauma CT for the femoral neck, especially when a femoral shaft fracture is present. Where a hip fracture is suspected despite normal radiographs, NICE CG124 (Hip fracture: management) recommends MRI as the investigation of choice, with CT if MRI is not available within 24 hours or is contraindicated.
• Classification: the Garden system grades displacement on the AP radiograph; the Pauwels classification grades the verticality of the fracture line, which predicts shear and guides implant choice in the young adult.

What is the initial management?

• Resuscitate and treat life-threatening injuries first; provide adequate analgesia (paracetamol plus opioid titration; consider a fascia iliaca block, as recommended for hip fracture patients in NICE CG124).
• Keep the patient fasted and escalate immediately to the on-call orthopaedic consultant — this is a decision that should not wait for the next trauma meeting.
• Plan urgent surgery. NICE CG124 recommends surgery for hip fracture "on the day of, or the day after, admission". No BOAST specifically addresses the young femoral neck fracture (the BOAST on the older or frail trauma patient covers the fragility population), and it is widely regarded as good practice to treat the displaced young femoral neck fracture with greater urgency than that — on the next available list, and ideally within hours — with a surgeon capable of achieving anatomical reduction, rather than as a purely out-of-hours emergency case done badly.

Does the clock really cause AVN? The traditional teaching of a strict 6-hour window is not well supported. A systematic review and meta-analysis (Papakostidis et al., Injury, 2015) found no significant association between time to internal fixation (6, 12 or 24-hour thresholds) and AVN, but delay beyond 24 hours substantially increased the odds of non-union. The defensible interview position: operate urgently — certainly within 24 hours — prioritising the quality of reduction over minutes saved, because reduction quality is the strongest modifiable predictor of outcome.

Should the capsular haematoma be decompressed?

This is the classic debate. The rationale is physiological: the hip capsule is unyielding, the fracture haematoma raises intracapsular pressure, and cadaveric and clinical pressure studies show that aspiration or capsulotomy lowers intracapsular pressure and can improve femoral head perfusion. Against this, no adequately powered prospective trial has shown that capsulotomy reduces AVN; the supporting literature consists of small observational series, and practice varies widely between surgeons and countries. A balanced answer is that capsular decompression (open capsulotomy at the time of open reduction, or percutaneous aspiration) is reasonable and low-cost, particularly in a displaced fracture undergoing open reduction where the capsule is opened anyway, but it cannot be mandated on current evidence — label it good practice by rationale, not a guideline standard.

What are the definitive fixation options?

Anatomical reduction comes first. Attempt gentle closed reduction on the traction table; if an anatomical reduction cannot be achieved closed, proceed to open reduction (Smith-Petersen anterior or Watson-Jones anterolateral approach). Accepting a poor closed reduction to keep the operation percutaneous is the recognised error.

• Multiple cannulated cancellous screws (typically three, inverted triangle, washers in weaker bone) — standard for undisplaced and low-angle fractures; minimal further insult to the head.
• Sliding hip screw ± anti-rotation screw — a fixed-angle, load-sharing device better suited to vertical (Pauwels III) and basicervical patterns.
• Adjuncts for the vertical fracture — a medial buttress plate or an off-axis screw may be added to neutralise shear; the femoral neck system (FNS) is an increasingly used fixed-angle alternative, though long-term comparative data in young adults are limited.
• Arthroplasty is reserved for the exceptional young patient in whom fixation is not viable (pathological bone, delayed presentation with a non-viable head, or physiological rather than chronological old age).

The evidence: the FAITH trial (Lancet, 2017; 1,108 patients aged 50 and over with low-energy femoral neck fractures) found no difference in 24-month reoperation between sliding hip screw and cancellous screws (20% vs 22%, HR 0.83, p=0.18); AVN was more common with the sliding hip screw (9% vs 5%), while subgroup analyses of low-to-moderate credibility favoured the sliding hip screw in displaced fractures, basicervical fractures and smokers. Its findings are extrapolated to, not derived from, the young adult. The FAITH-2 pilot (91 patients aged 18–60, J Orthop Trauma, 2020) found no significant difference between implants and no benefit from vitamin D 4,000 IU daily, and confirmed that a definitive trial in this rare injury is difficult to deliver. In practice, implant choice is dictated by fracture geometry more than by trial data.

What are the complications and outcomes?

Pooled data from 41 studies of young femoral neck fractures (Slobogean et al., Injury, 2015) give the numbers worth quoting: AVN 14.3%, non-union 9.3%, malunion 7.1%, implant failure 9.7%, and reoperation approximately 18%, with displaced fractures faring significantly worse. AVN may declare itself two years or more after injury, so follow-up must be prolonged and the patient counselled from the outset. Established AVN with collapse, or failed fixation, is usually salvaged by total hip arthroplasty; symptomatic non-union in a young patient with a viable head can be treated with a valgising intertrochanteric osteotomy to convert shear into compression. Malunion (typically varus with shortening) causes abductor weakness and limp.

Key points

• A young-adult femoral neck fracture is a high-energy, limb-altering injury: the goal is preservation of the native femoral head.
• Operate urgently — NICE CG124 requires surgery by the day after admission, and good practice is fixation within 24 hours; delay beyond 24 hours increases non-union, while the timing–AVN link is unproven.
• Anatomical reduction (open if necessary) is the strongest modifiable determinant of outcome; do not accept a poor closed reduction.
• Capsular decompression is physiologically rational but unproven — present it as an option, not a standard.
• Implant by geometry: cannulated screws for undisplaced/low-angle patterns; fixed-angle constructs (SHS ± derotation screw, FNS, ± medial buttress) for Pauwels III and basicervical fractures.
• Quote the pooled figures: AVN ~14%, non-union ~9%, reoperation ~18%; counsel and follow up for at least two years.