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KneeSchool/Imaging Academy/MPFL Reconstruction

MPFL Reconstruction

Page 5.17.6 · Post-operative Imaging · imaging page

An intact graft in a patella that still displaces, which is a failure of indication rather than of fixation.

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

The same topic at 4 depths

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MPFL Reconstruction

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For Medical Students

What It Shows

Post-operative imaging of a medial patellofemoral ligament reconstruction shows the graft, its femoral and patellar fixation, and the patella's position. 5.12.8 covers the post-operative imaging.

Radiographs show the fixation and any tunnel, and magnetic resonance imaging shows the graft. 5.3.3 covers the skyline view.

It matters because the construct can be intact while the patella still displaces, and the two findings are reported alike. 5.12.4 covers patellar subluxation.

How It Is Acquired

State the interval and the technique if known, since graft paths differ. 5.5.3 covers the post-operative protocol.

Assess the graft from its femoral attachment to the medial patella. 5.12.5 covers MPFL injury.

Assess both fixation points for position and migration. 5.5.6 covers the bones.

Repeat the pre-operative measurements by the same method. 5.16.4 covers the TT-TG measurement.

Assess the patella's position and the cartilage of both surfaces. 5.12.6 covers cartilage injury.

What Normal Looks Like

A continuous graft running from the medial femur to the medial patella. 5.12.5 covers MPFL injury.

Fixation in position at both ends. 5.5.6 covers the bones.

A patella engaged in the groove at the imaged angle. 5.12.4 covers patellar subluxation.

Measurements unchanged where the operation did not address them. 5.16.4 covers the TT-TG measurement.

What Abnormal Looks Like

A graft that is discontinuous or pulled off its attachment. 5.12.5 covers MPFL injury.

Fixation that has migrated, or a fracture at the patellar fixation. 5.3.12 covers patellar fractures.

A patella still displaced or tilted with the graft intact. 5.12.3 covers patellar tilt.

New medial cartilage loss, which over-tensioning can cause. 5.12.6 covers cartilage injury.

Bony measurements unchanged in a knee whose instability persists. 5.12.1 covers trochlear dysplasia.

Key Learning Points

  • The graft can be intact while the patella displaces.
  • Both fixation points are assessed.
  • The pre-operative measurements are repeated.
  • Over-tensioning damages medial cartilage.
  • Unchanged measurements with persisting instability point elsewhere.

MRCS Level

How It Is Acquired

In a viva the expected answer separates the construct from the indication.

The expected points are the interval and technique, the graft, both fixations, the repeated measurements, and the cartilage.

Say that an intact graft does not mean a stable patella. 5.12.4 covers patellar subluxation.

Say that the bony risk factors were there before and are there still. 5.12.1 covers trochlear dysplasia.

Say that the examination reports the stability. 4.20.6 covers the MPFL reconstruction examination.

What Abnormal Looks Like

The reasoning expected is that the ligament is a passive restraint near extension, so reconstructing it addresses one contributor while the groove, the patellar height and the rotation remain as they were. 3.12.5 covers the MPFL function.

That is why a technically perfect reconstruction can fail, and why the imaging has to report the measurements rather than only the graft. 5.16.4 covers the TT-TG measurement.

Over-tensioning loads the medial facet and produces its own problem, which is a recognised complication rather than a surprise. 5.12.6 covers cartilage injury.

Patellar fixation carries a fracture risk, which the radiograph rather than the scan reports. 5.3.12 covers patellar fractures.

How Good It Is

Imaging is a good test of this construct and no test of the patella's stability.

Its best contribution is the graft, the fixation and the repeated measurements. 5.16.4 covers the TT-TG measurement.

It is limited because stability is dynamic and loaded while the study is static and unloaded, and because the groove cannot be changed by this operation. 5.12.1 covers trochlear dysplasia.

No figures appear for accuracy on this page, under decision 028, and no graft tension, tunnel position or measurement values appear either: those are published quantities tied to particular techniques and this environment cannot check them.

Key Learning Points

  • The ligament is one contributor among several.
  • A perfect reconstruction can fail on indication.
  • Over-tensioning loads the medial facet.
  • Patellar fixation carries a fracture risk.
  • Stability is dynamic and the study is static.

FRCS Level

How Good It Is

At decision level the imaging separates a technical failure from a wrong operation. 5.12.8 covers the post-operative imaging.

A failed graft or migrated fixation is technical and visible. 5.5.6 covers the bones.

An intact construct with recurrent instability points at the groove, the height or the rotation. 5.16.3 covers the rotational profiles.

Medial cartilage loss after reconstruction changes the conversation from instability to pain. 5.12.6 covers cartilage injury.

A revision plan needs every measurement repeated by the method the original used. 5.16.4 covers the TT-TG measurement.

Where It Misleads

The commonest error is reporting the graft and not the measurements. 5.20.8 covers common reporting errors.

A continuous graft is read as a successful operation. 5.12.4 covers patellar subluxation.

Expected signal around a tunnel is read as loosening. 5.5.3 covers the post-operative protocol.

A measurement made after a tubercle transfer is compared with a threshold from unoperated knees. 5.16.4 covers the TT-TG measurement.

Medial cartilage loss is attributed to the instability rather than to the reconstruction. 5.12.6 covers cartilage injury.

Key Learning Points

  • The graft is reported and the measurements are not.
  • Continuity is read as success.
  • Peritunnel signal is read as loosening.
  • Operated knees are measured against unoperated thresholds.
  • Medial loss can be the reconstruction's own effect.

Fellowship Level

Where It Misleads

At fellowship level the patella has been reconstructed once and is unstable again. 5.12.4 covers patellar subluxation.

The construct rarely identifies the technique, and graft paths differ enough to change what is expected. 5.12.5 covers MPFL injury.

The pre-operative measurements are the key record and are often absent from the referral. 5.20.1 covers structured reporting.

Where a procedure on the groove was performed, the groove's measurements now describe the operation. 5.12.1 covers trochlear dysplasia.

Dynamic and loaded studies address the real question and are rarely available. 5.18.5 covers weight-bearing MRI.

The useful report gives the interval, the graft, both fixations, the repeated measurements with their method, the cartilage, and the statement that stability is a clinical finding. 5.20.1 covers structured reporting.

Key Learning Points

  • The technique is rarely identifiable and graft paths differ.
  • The pre-operative measurements are the key record.
  • A procedure on the groove makes its measurements describe the operation.
  • Loaded studies address the real question and are scarce.
  • The report states that stability is a clinical finding.

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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