Perilunate and Lunate Dislocation: The Wrist Injury X-Rays Get Read Wrong

Written by Nigel Chua, hand occupational therapist · 21 years treating fingers, hands, wrists, forearms and elbows · Singapore

The Wrist Injury X-Rays That Often Mistakenly Get Read As Normal

A perilunate dislocation is a severe injury in which the wrist bones dislocate AROUND the lunate, and a lunate dislocation is the later stage where the lunate itself gets pushed out of place.

They are the same injury at different points along one sequence.

Around a quarter of these are missed at the first hospital visit, because the front-on X-ray can look almost normal and the injury only declares itself on the side view.

This is the one wrist injury on this site where the delay is measured in hours, not weeks.

What happens mechanically

High energy — a fall from height, a motorbike accident, a heavy fall onto an extended wrist.

The force travels around the lunate in a predictable arc, tearing ligaments as it goes.

Stage 1: scapholunate ligament fails
Stage 2: the capitate dislocates behind the lunate
Stage 3: the lunotriquetral ligament fails
Stage 4: the lunate itself is squeezed forwards out of position — a lunate dislocation

Often a bone breaks on the way through, most commonly the scaphoid. That variant is called a trans-scaphoid perilunate dislocation, and it is the commonest version.

The lunate ends up sitting in the carpal tunnel. Which is why acute median nerve symptoms — numbness in thumb, index and middle fingers, appearing straight after the injury — are part of the presentation and not a coincidence.

Why it gets missed

On the PA film, the carpal bones stay roughly in a row. What’s abnormal is the loss of the three smooth arcs the wrist bones normally form — subtle unless you’re looking for it.

On the LATERAL film it is obvious: the normal stack of radius, lunate, capitate is broken. The lunate tips forward into what radiologists call the spilled teacup sign.

If a high-energy wrist injury was assessed without a proper lateral X-ray, it was not assessed.

The other reason it’s missed: swelling and severe pain get attributed to a bad sprain, and the wrist is put in a cast.

What to do

This one is short. Emergency department, same day.

Reduction — putting the bones back — is usually done urgently to take pressure off the median nerve, but it is a holding measure, not the treatment.

Definitive treatment is surgical, ideally within the first week:

Open reduction, ligament repair, and wire or screw fixation
Carpal tunnel release where there are nerve symptoms
Fixation of the scaphoid fracture if present

Recovery, honestly

Week 0 to 8: cast or splint with wires in place
Week 8 to 10: wires removed, motion begins
Month 3 to 6: strengthening, gradual return to load
Month 6 to 12: final functional level

Even with prompt, well-executed surgery, the typical outcome is around 60 to 70 percent of normal wrist motion and grip.

Post-traumatic arthritis develops in a substantial proportion within 5 to 10 years. Heavy manual workers frequently do not return to the same job.

Missed or treated late, the outcomes are markedly worse, and salvage procedures — partial fusion, proximal row carpectomy — become the realistic options rather than repair.

The window

First 8 hours: reduce it, protect the nerve
First week: definitive repair, best results
Beyond 6 to 8 weeks: ligaments have scarred and shortened; anatomic repair becomes unreliable
Chronic: salvage surgery only

This is not a wrist sprain that went badly. It is one of the highest-energy injuries the wrist sustains, and the whole prognosis turns on whether somebody looked at the side view on day one.