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KneeSchool/Imaging Academy/ACL Reconstruction

ACL Reconstruction

Page 5.17.1 · Post-operative Imaging · imaging page

Graft, tunnels and fixation, where the tunnel position decides a revision and the graft's signal needs an interval to mean anything.

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.

ACL Reconstruction

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For Medical Students

What It Shows

Post-operative imaging of an ACL reconstruction shows the graft, the tunnels carrying it and the fixation holding it. 5.7.9 covers the ACL reconstruction.

Radiographs show the tunnels and the fixation, and magnetic resonance imaging shows the graft. 5.3.2 covers the lateral view.

It matters because the construct has three parts and each one fails differently. 5.7.11 covers the graft failure.

How It Is Acquired

Obtain radiographs first, for the fixation and the tunnel apertures. 5.3.2 covers the lateral view.

Use a post-operative protocol where the graft is the question. 5.5.3 covers the post-operative protocol.

State the interval since surgery before describing the graft. 5.7.10 covers the graft maturation.

Assess the tunnel positions on the femoral and the tibial side. 5.7.12 covers the tunnel assessment.

Assess the menisci and the cartilage, since they carry the prognosis. 5.20.2 covers reporting meniscal tears.

What Normal Looks Like

A continuous graft running between its tunnel apertures. 5.7.9 covers the ACL reconstruction.

Fixation in position with no migration at the bone interface. 5.5.6 covers the bones.

Tunnel apertures at their intended positions. 5.7.12 covers the tunnel assessment.

Signal change around the graft and the tunnels appropriate to the interval. 5.7.10 covers the graft maturation.

No cyclops lesion in the anterior notch. 5.7.13 covers the cyclops lesions.

What Abnormal Looks Like

A discontinuous or absent graft. 5.7.11 covers the graft failure.

Fixation that has migrated or loosened. 5.5.6 covers the bones.

A tunnel aperture away from its intended position. 5.7.12 covers the tunnel assessment.

Tunnel widening, which matters for a revision rather than for the diagnosis. 5.7.14 covers the revision ACL imaging.

A cyclops lesion limiting extension. 5.7.13 covers the cyclops lesions.

Key Learning Points

  • The construct has three parts, each failing differently.
  • Radiographs carry the fixation and the tunnels.
  • The interval is stated before the graft is described.
  • Tunnel position matters most for a revision.
  • Tunnel widening is a revision finding.

MRCS Level

How It Is Acquired

In a viva the expected answer separates graft, tunnel and fixation.

The expected points are the radiographs, the post-operative protocol, the interval, the tunnel positions, and the menisci and cartilage.

Say that graft signal changes for a long time and alone says nothing. 5.7.10 covers the graft maturation.

Say that tunnel position is the finding a revision depends on. 5.7.12 covers the tunnel assessment.

Say that the examination reports the function and the imaging the construct. 4.20.1 covers the ACL reconstruction examination.

What Abnormal Looks Like

The reasoning expected is that a graft remodels through a predictable sequence, so an appearance is abnormal only relative to the time since surgery, which makes the interval part of the finding rather than part of the history. 5.7.10 covers the graft maturation.

A mechanically failed graft is often continuous on imaging, because failure is laxity rather than rupture in many cases, which is why the examination decides the outcome. 4.20.1 covers the ACL reconstruction examination.

Tunnel position explains more failures than graft choice does, and it is fixed at the index operation. 5.7.12 covers the tunnel assessment.

A meniscal or chondral injury left untreated at the index operation changes the prognosis independently of the graft. 5.20.5 covers reporting cartilage lesions.

How Good It Is

Imaging is a good test of the construct's integrity and no test of the reconstruction's success.

Its best contribution is the tunnel positions, the fixation and any secondary injury. 5.7.12 covers the tunnel assessment.

It is limited because graft signal is time dependent, because a continuous graft can be incompetent, and because laxity is a clinical measurement. 4.20.1 covers the ACL reconstruction examination.

No figures appear for accuracy on this page, under decision 028, and no tunnel positions, widening measurements or maturation intervals appear either: those are published quantities tied to particular techniques and this environment cannot check them.

Key Learning Points

  • An appearance is abnormal only relative to the interval.
  • A failed graft is often continuous on imaging.
  • Tunnel position explains more failures than graft choice.
  • Untreated secondary injury changes the prognosis.
  • Laxity is a clinical measurement.

FRCS Level

How Good It Is

At decision level the imaging decides whether a revision can be single stage. 5.7.14 covers the revision ACL imaging.

Tunnel position and tunnel diameter together answer that, and both want the radiographs and a computed tomography study. 5.16.8 covers the 3D reconstructions.

A malpositioned tunnel is a technical failure, and a well positioned one with laxity points elsewhere. 5.20.4 covers reporting MCL injuries.

The secondary restraints and the meniscal root belong in the same assessment. 5.6.9 covers root tears.

Alignment belongs in the plan for a failed reconstruction, which means a standing radiograph rather than a scan. 5.3.6 covers the long leg alignment films.

Where It Misleads

The commonest error is reporting graft failure from signal alone. 5.7.10 covers the graft maturation.

Expected peritunnel signal is read as infection. 5.5.3 covers the post-operative protocol.

A continuous graft is read as a successful reconstruction. 4.20.1 covers the ACL reconstruction examination.

Tunnel widening is read as a cause rather than as a constraint on the revision. 5.7.14 covers the revision ACL imaging.

A cyclops lesion is reported as scar with no mention of extension. 5.7.13 covers the cyclops lesions.

Key Learning Points

  • Graft failure is reported from signal alone.
  • Peritunnel signal is read as infection.
  • Continuity is read as success.
  • Widening is a constraint rather than a cause.
  • A cyclops lesion has a functional consequence.

Fellowship Level

Where It Misleads

At fellowship level the reconstruction was done elsewhere and the operative detail is unavailable. 5.20.7 covers reporting the post-operative knee.

The construct on the images rarely identifies the technique, and the technique sets what the tunnels should look like. 5.7.12 covers the tunnel assessment.

The index imaging records the anatomy before the tunnels existed and is the most useful study to obtain. 5.20.1 covers structured reporting.

A second failure after a technically sound revision points at alignment, the secondary restraints or the rotational profile. 5.16.3 covers the rotational profiles.

Automated tunnel measurement fixes one convention and returns a number that looks settled. 5.18.8 covers artificial intelligence in imaging.

The useful report gives the interval, the graft, the fixation, both tunnel positions, any widening, the secondary injuries and the alignment. 5.20.1 covers structured reporting.

Key Learning Points

  • The technique is rarely identifiable from the images.
  • The index imaging is the most useful study to obtain.
  • A second failure points away from the graft.
  • Automated measurement looks settled and is not.
  • The report gives the interval first.

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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