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Instrument 08Coupled
Pre-op instrument · elbow

The elbow operation that fails at the wrist.

The forearm is a ring: the joint at the elbow, the interosseous membrane between, the joint at the wrist. Take the radial head out while the membrane is incompetent and the radius migrates proximally. The elbow is fine. Months later the patient has ulnar-sided wrist pain from impaction, at a joint nobody touched, and often in a different clinic.

Signature
>3 mm / >2 mm
The two published pull-test thresholds, reported as a gap rather than resolved.
Fig. 1 · The forearm ring, and where it announces itself
radiusulna1 · radial head excised here2 · membrane incompetent, radius migrates3 · pain presents HERE, months laterinterosseous membrane
Break the ring proximally and it can fail distally. The radial head is a secondary stabiliser — expendable only while the coronoid, the medial ligament and the membrane all hold.
Test this forearm → Why this is the strongest case in the thesis →
One intra-operative test and two ligament questions · answers whether the radial head is expendable
The envelope · longitudinal forearm stability

The adjacent segment is at the other end of the limb.

In the hip the adjacent segment is the pelvis, a few centimetres away. In the ankle it is the joint immediately below. Here it is a whole forearm away, which is why this failure is so often not attributed to the operation that caused it.

The ring

Intra-operative radius pull test, and the wrist films.
5.0 mm
Over about 3 mm suggests central-band incompetence. A related test puts it nearer 2 mm.
3.0 mm
The wrist telling you the radius has already moved.

Who else is holding this elbow up

The radial head is a secondary stabiliser. These are the primaries.
The question this page exists to answer
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The four tiers

The radial head is expendable right up until it is not.

Tier A · fix what is broken

The ring holds.

Membrane competent, primaries intact, head reconstructable. Fix it and the forearm looks after itself.

Forearm instability, J Hand Surg →
Tier B · excision is defensible

Nothing is asking it to do a job.

Unreconstructable head, competent membrane, intact primaries. Taking it out does not start a migration.

Essex-Lopresti diagnosis and treatment →
Tier C · now load-bearing

Replace it. Do not excise it.

Either the membrane is incompetent or a primary stabiliser is gone. In both cases the head has been promoted from secondary to essential.

Why the head stops being expendable →
Tier D · broken in two places

Plan for the membrane, and warn them about the wrist.

Longitudinal instability and failed primaries together. Replace, repair, address the central band — and tell the patient which joint is most likely to hurt afterwards.

Addressing the central band →
The numbers

Two thresholds that disagree, and one hierarchy that does not.

The conventional threshold
>3 mm
Longitudinal displacement on the pull test taken to indicate membrane disruption
And a stricter one
>2 mm
The radial axial interosseous load test. This instrument reports the gap between them rather than picking
The hierarchy
secondary
The radial head is a secondary valgus stabiliser; the coronoid and medial collateral are primary
What restores the ring
head + band
Replacement together with central-band reconstruction has been reported to restore radioulnar displacement toward normal
And a caution
not automatic
Three or more fragments does not by itself mandate replacement or excision; fixation can do well
No mandate here
none
TEAM reaches knee, hip, ankle and spinal fusion. Not the elbow
What this instrument cannot do. The pull test is intra-operative, so this informs a decision made with the elbow already open — it is a rehearsal, not a clinic tool. Membrane competence is inferred from displacement rather than imaged. Ulnar variance comparison assumes a normal contralateral wrist. And absence of a wrist signal early is not reassurance, because migration is progressive. Not a cleared device, not clinical advice.
Log this forearm

Put the first row in.

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