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KneeSchool/Imaging Academy/Graft Failure

Graft Failure

Page 5.7.11 · ACL MRI · imaging page

The failed reconstruction, where the useful question is why rather than whether.

Pipeline status. Editorial draft. Evidence verification did not run. Not consultant reviewed. Not for clinical use.

The same topic at 4 depths

Each tier deepens the one below it and never repeats it. Choose the level you want.

Graft Failure

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For Medical Students

What It Shows

A graft fails when it ruptures, when it stretches, or when it was never placed where it could work. 3.7.20 covers the reconstruction biomechanics.

Imaging shows a discontinuous graft, a graft with a lost line, or correctly intact tissue in the wrong tunnels. 5.7.9 covers cruciate reconstruction.

It matters because the three have different answers, and a report that says only that the graft has failed gives the surgeon nothing to plan with. 6.8.1 covers graft failure.

How It Is Acquired

Assess continuity on three planes, which separates a rupture from the other mechanisms. 5.5.9 covers the ligaments.

Assess the graft's line against the notch roof, which detects a graft that is continuous and lengthened. 2.7.12 covers the surgical anatomy.

Assess the tunnel positions, since a malpositioned tunnel is the explanation rather than the consequence. 5.7.12 covers tunnel assessment.

Measure anterior tibial translation, which is the mechanical state. 3.7.8 covers anterior stability.

Assess the secondary restraints, because a failed graft in a knee with an unaddressed corner injury is a different problem. 5.10.3 covers posterolateral corner injuries.

What Abnormal Looks Like

A discontinuous graft with fluid signal along its course, which is a rupture.

A continuous graft lying flatter than the notch roof, which is a lengthened graft. 2.7.12 covers the surgical anatomy.

Tunnels placed anteriorly on the femur or posteriorly on the tibia, which load a graft abnormally through range. 5.7.12 covers tunnel assessment.

Anterior tibial translation with a buckled posterior cruciate, the mechanical companion signs. 5.8.1 covers the normal posterior cruciate.

Key Learning Points

  • A graft fails by rupture, by stretching, or by being wrongly placed.
  • The three mechanisms have different answers.
  • A lengthened graft is continuous, so continuity alone is not enough.
  • Tunnel position is the explanation rather than the consequence.
  • The secondary restraints are part of this assessment.

MRCS Level

How It Is Acquired

In a viva the expected answer asks why the graft failed rather than confirming that it has.

The expected points are continuity, the line, the tunnels, the translation, and the secondary restraints.

Say that a technical cause and a traumatic cause lead to different revisions. 6.8.2 covers tunnel malposition.

Say that a continuous graft can be a failed graft. 2.7.12 covers the surgical anatomy.

Say that an unaddressed corner injury is a cause of graft failure rather than an incidental finding. 5.10.3 covers posterolateral corner injuries.

What Abnormal Looks Like

The reasoning expected is that a graft placed outside the native footprint changes length through flexion, so it is either too tight in part of the range or too loose in the rest, and it fails from repeated loading rather than from one event. 3.7.20 covers the reconstruction biomechanics.

A graft in correct tunnels that ruptures from a new injury behaves like a native ligament failing, with the secondary injury signs to match. 5.11.7 covers bone marrow lesions.

A biologically failed graft stretches without a discrete rupture, which is why the line matters more than the signal. 5.7.10 covers graft maturation.

An unaddressed secondary restraint leaves the graft carrying loads it was not designed for, which is a mechanical cause of failure visible elsewhere in the study. 3.7.3 covers the secondary restraints.

How Good It Is

Magnetic resonance imaging detects a ruptured graft well and distinguishes the mechanisms of failure only when it is asked to.

Its best contribution is the combination of continuity, line and tunnel position, which separates a technical failure from a traumatic one. 5.7.12 covers tunnel assessment.

It is limited by a lengthened graft looking intact, and by the rotational component of the failure being outside what the study measures. 3.7.7 covers rotational stability.

No figures appear for accuracy on this page, under decision 028, and the comparison is the claim: rupture is detected better than stretching, which is a comparison rather than a number.

Key Learning Points

  • A graft outside the native footprint changes length through flexion.
  • A traumatic rupture carries the secondary injury signs of a native tear.
  • A biologically failed graft stretches without rupturing.
  • An unaddressed secondary restraint loads the graft abnormally.
  • Rupture is detected better than stretching.

FRCS Level

How Good It Is

At decision level this study is read to plan a revision, and what it needs to supply is the reason.

Malpositioned tunnels mean the revision is a redesign, and may mean a staged procedure if the tunnels are also widened. 6.8.2 covers tunnel malposition.

Correct tunnels with a traumatic rupture mean the revision can follow the same plan, which is the simplest case. 6.8.1 covers graft failure.

A stretched graft with correct tunnels and an unaddressed corner points the revision at the corner as much as at the cruciate. 5.10.3 covers posterolateral corner injuries.

Varus or increased tibial slope loading the graft is a mechanical cause that no cruciate revision alone addresses. 5.3.7 covers the mechanical axis.

Where It Misleads

The commonest error is reporting graft failure without the mechanism, so the report names a problem and no cause. 5.20.7 covers reporting the post-operative knee.

A lengthened graft is reported as intact because only continuity was assessed. 2.7.12 covers the surgical anatomy.

Tunnel position is not measured, so a technical cause is missed. 5.7.12 covers tunnel assessment.

Expected remodelling signal in the first year is reported as failure. 5.7.10 covers graft maturation.

The secondary restraints and the alignment are left out of a study read as a graft study. 5.10.3 covers posterolateral corner injuries.

Key Learning Points

  • A failure report without a mechanism gives the surgeon nothing to plan with.
  • A lengthened graft is reported as intact when only continuity is assessed.
  • An unmeasured tunnel hides a technical cause.
  • Remodelling signal in the first year is reported as failure.
  • The secondary restraints and alignment are left out.

Fellowship Level

Where It Misleads

At fellowship level the failed reconstruction is where imaging is closest to being decisive and most often falls short of it.

Tunnel position is the one measurement in this chapter with an agreed geometric basis, and it is reported inconsistently or not at all, which wastes the study's strongest contribution. 5.7.12 covers tunnel assessment.

Rotational failure is the commonest complaint after a reconstruction that looks intact, and no routine study measures rotation. 3.7.7 covers rotational stability.

Tibial slope is a recognised mechanical contributor to repeated graft failure and is measured on a lateral radiograph that is often not requested with the magnetic resonance study. 5.3.2 covers the lateral view.

Tunnel widening is assessed better on computed tomography, which belongs to its own chapter and is frequently not obtained before a revision is planned. 5.16.8 covers three dimensional reconstructions.

The report that would change a revision names the tunnels, the slope and the corners, and most reports name the graft. 5.20.1 covers structured reporting.

Key Learning Points

  • The study's strongest measurement is its most inconsistently reported.
  • Rotational failure is common and no routine study measures rotation.
  • Tibial slope needs a lateral radiograph that is often not requested.
  • Tunnel widening is a computed tomography question and is often skipped.
  • The useful report names the tunnels, the slope and the corners.

Explore Further

Where this topic came from and where it goes next in the spiral.

References

No reference list is attached to this draft. Evidence verification has not run, because source retrieval was unavailable at generation time. Under the Operations Handbook a missing reference is acceptable and an invented one is a critical failure, so nothing has been cited and no citation marker appears in the text. This page carries no diagnostic accuracy figure, which is decision 028 rather than an omission: the comparative standing of the modalities is standard teaching and a specific sensitivity written from memory is the same class of claim as an invented citation, so ACC-001 refuses the number and the page states the comparison. A reviewer with the literature can add the figures into How Good It Is without restructuring the page. Any measurement here, including a sequence parameter, an angle or a millimetre, is written from standard teaching, has not been checked, and is registered under decision 006 in pipeline/config/figures with a verification state of UNVERIFIED_FROM_MEMORY.

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