An eight-point score for osteonecrosis risk after screw fixation of femoral neck fracture

Design

Retrospective multicentre derivation study

Population

1,012 adults aged 18–65 with femoral neck fracture fixed with three cannulated screws

Primary outcome

Osteonecrosis of the femoral head at ≥2 years

Effect

4% at scores 0–3 vs 42% at 6–8; AUC 0.80 vs 0.70 for Garden

This retrospective study across three Chinese centres analysed 1,012 patients aged 18 to 65 whose femoral neck fractures were fixed with three cannulated screws, with at least two years of follow-up. Osteonecrosis of the femoral head developed in 21%.

Five preoperative factors made up the score: age 45 or over (1 point), displacement (3), comminution (1), a superior subcapital fracture line (2) and an inferior subcapital fracture line (1). Osteonecrosis occurred in 4% of patients scoring 0–3 and 42% of those scoring 6–8. The score discriminated better than the Garden classification (AUC 0.80 vs 0.70), and remained useful within displaced fractures.

The score is most useful for counselling: a young patient with a high score can be told plainly that head preservation carries a substantial chance of later arthroplasty. It has not been validated outside the derivation centres, and 21% of patients were excluded for missing imaging or follow-up.

• Record displacement, comminution, fracture line position and age before fixing a femoral neck fracture in a younger adult.
• Consider using the score to counsel patients about the chance of later osteonecrosis.
• Plan closer radiological follow-up for patients with high scores.
• Do not use the score alone to choose arthroplasty over fixation until it is externally validated.

Why it matters

It gives a younger patient a number for the risk they are taking by keeping their own femoral head.

Don't overread it

The score has not been externally validated; it was developed and tested in the same three centres.

The statistics, in plain English

An AUC of 0.80 means the score ranks a patient who develops osteonecrosis above one who does not about 80% of the time, against 70% for Garden. Scores derived and tested in the same data usually perform worse elsewhere.

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