Glossary
Interference screw
Quick answer
An interference screw is a small screw inserted alongside a ligament graft inside its bone tunnel, wedging the graft firmly against the bone while it heals in. Most never need removal, explains Dr. Pablo Gelber, who performs ACL reconstruction at Aman Hospital in Doha, Qatar.
What it is
During ligament reconstruction, tunnels are drilled in the thighbone and shinbone and the graft is passed through them. An interference screw is driven into the tunnel next to the graft. It works by pressure: it squeezes the graft or its bone block against the tunnel wall so it cannot slide.
Screws are made of titanium, of materials designed to be gradually absorbed and replaced by bone, or of composite materials. Each has advantages, and the choice depends on the graft and the surgeon's technique.
Why it matters for patients
Secure fixation lets rehabilitation start early, including bending the knee and taking weight, while the graft heals into the bone over the following months.
Metal screws show on X-ray but cause little distortion on modern MRI. Absorbable screws avoid metal but can leave a cyst-like area while they break down, which is usually harmless.
Will it ever need attention?
Most screws stay in place for life without problems. Occasionally one irritates the tissues near the shin and is removed, or it has to be taken out or bypassed during revision surgery. Pain directly over a screw is worth mentioning at follow-up.
Frequently asked questions
Will the screw set off airport security?
Small knee screws rarely trigger airport scanners, and many are not metal at all. If you are concerned, your surgical summary describes what was used.
Can I have an MRI with an interference screw?
Yes. Titanium and absorbable screws are compatible with MRI, although a metal screw can create a small dark area on the images near it.
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