Fissuring

For Medical Students

What It Shows

A fissure is a cleft in the cartilage surface with the layer's overall thickness preserved. 5.11.1 covers normal cartilage.

It appears as a line of fluid signal extending from the surface into the substance. 5.11.2 covers chondral defects.

It matters because it is the earliest morphological abnormality visible, and it is at the limit of what the resolution supports. 5.2.5 covers magnification.

How It Is Acquired

Use a cartilage sensitive sequence with a sharp cartilage to fluid interface. 5.2.18 covers gradient echo imaging.

Use the thinnest slices available, because a fissure is narrower than most slice thicknesses. 5.2.5 covers magnification.

Look at the surface contour as well as the signal, since a surface irregularity may be the only sign. 5.11.1 covers normal cartilage.

Confirm in a second plane, because partial volume averaging produces a line in one plane. 5.5.1 covers the standard protocol.

Assess whether the thickness is preserved, which is what separates this from a defect. 5.11.2 covers chondral defects.

What Abnormal Looks Like

A linear fluid signal cleft running from the surface into the cartilage with preserved thickness around it. 5.11.1 covers normal cartilage.

Surface irregularity without a visible cleft, which is a softer sign.

Fissuring in a compartment whose cartilage is otherwise of normal thickness. 5.11.2 covers chondral defects.

No subchondral marrow change, or a small amount beneath it. 5.11.7 covers bone marrow lesions.

MRCS Level

How It Is Acquired

In a viva this is the finding to name when asked what the earliest visible cartilage change is.

The expected points are the cartilage sequence, the thinnest slices, the surface contour, the second plane, and the preserved thickness.

Say that it is at the limit of the resolution. 5.2.5 covers magnification.

Say that a single plane line may be partial volume averaging. 5.5.1 covers the standard protocol.

Say that matrix change precedes it and is invisible on a routine study. 5.18.2 covers T2 mapping.

What Abnormal Looks Like

The reasoning expected is that a fissure is narrower than the voxel it sits in, so it is detected by the fluid filling it rather than by its own dimensions, which makes detection dependent on the fluid contrast. 5.2.18 covers gradient echo imaging.

That dependence is why a cartilage sensitive sequence matters more here than for any other cartilage finding. 5.5.7 covers the cartilage.

Fissuring follows matrix degeneration, so the tissue was already abnormal before the fissure appeared, and the compositional sequences detect that earlier phase. 5.18.3 covers T1 rho imaging.

Preserved thickness is what makes it a different lesion from a defect, because there is still a full layer bearing load. 3.5.2 covers the contact pressures.

How Good It Is

Fissuring is the cartilage finding at the limit of the modality's resolution, and its detection depends almost entirely on the sequence.

Its best contribution is identifying a compartment with early change in a knee that is otherwise normal. 5.11.1 covers normal cartilage.

It is limited by being narrower than the voxel, by partial volume artefacts imitating it, and by its clinical significance being uncertain. 5.21.3 covers the cartilage imaging literature.

No figures appear for accuracy on this page, under decision 028, and no depth or width values appear either: those are published quantities and this environment cannot check them.

FRCS Level

How Good It Is

At decision level fissuring changes the conversation rather than the operation.

Fissuring in a symptomatic compartment establishes that the cartilage is involved, which supports a loading and activity discussion. 4.17.5 covers articular cartilage defects.

Fissuring is not itself a repair indication, because there is no defect to fill. 5.11.8 covers cartilage repair procedures.

Fissuring adjacent to a planned meniscal or cruciate operation is prognostic information for that operation. 5.6.13 covers meniscal repair imaging.

Fissuring in an asymptomatic compartment is a finding of uncertain significance and should be reported as such. 5.20.5 covers reporting cartilage lesions.

Where It Misleads

The commonest error is reporting a partial volume artefact as a fissure. 5.2.5 covers magnification.

A single plane appearance is accepted. 5.5.1 covers the standard protocol.

Fissuring is treated as a repair indication. 5.11.8 covers cartilage repair procedures.

A normal zonal signal boundary is read as a fissure. 5.11.1 covers normal cartilage.

Symptoms are attributed to it without the clinical picture matching. 4.17.1 covers the cartilage clinical presentation.

Fellowship Level

Where It Misleads

At fellowship level fissuring sits in the awkward space between a finding the modality can barely see and a change that matters before it is visible.

Detection is at the resolution limit, so reported fissuring prevalence depends on the protocol more than on the population, which makes cross study comparison weak. 5.21.3 covers the cartilage imaging literature.

Matrix degeneration precedes fissuring and is detectable by compositional sequences, so the clinically interesting window is earlier than the morphologically visible one and is not routinely imaged. 5.18.3 covers T1 rho imaging.

The clinical significance of isolated fissuring is not established, so a finding at the edge of detectability carries an uncertain consequence, which is the worst combination for a report. 5.20.5 covers reporting cartilage lesions.

Three dimensional isotropic acquisition improves detection and changes the contrast, so improved sensitivity arrives with a changed reference. 5.2.18 covers gradient echo imaging.

The useful report states that the finding is at the limit of resolution and that its significance in isolation is uncertain. 5.20.5 covers reporting cartilage lesions.