Cartilage Repair Procedures

For Medical Students

What It Shows

A cartilage repair procedure fills a defect with repair tissue, by stimulating marrow, by implanting cells or by transplanting tissue. 5.11.9 covers ACI imaging.

Imaging after one shows how much of the defect is filled, what the repair tissue looks like and what the bone beneath is doing. 5.11.7 covers bone marrow lesions.

It matters because fill is measurable and the repair tissue's mechanical quality is not, which is the same conclusion the meniscal and cruciate repair pages reach. 5.6.13 covers meniscal repair imaging.

How It Is Acquired

Establish which procedure was done and when, because the expected appearance differs between them and over time. 5.17.5 covers post-operative cartilage procedures.

Use a cartilage sensitive sequence, and compare with the earliest post-operative study. 5.2.18 covers gradient echo imaging.

Assess the degree of fill against the surrounding cartilage. 5.11.2 covers chondral defects.

Assess the repair tissue's signal relative to native cartilage, accepting that it differs. 5.11.1 covers normal cartilage.

Assess the subchondral bone, which responds to the repair and often looks worse before it looks better. 5.11.7 covers bone marrow lesions.

What Normal Looks Like

A defect filled to the level of the surrounding cartilage, with a continuous surface. 5.11.2 covers chondral defects.

Repair tissue whose signal differs from native cartilage, which is expected rather than failure. 5.11.1 covers normal cartilage.

Subchondral marrow signal beneath the repair, which is expected in the early period. 5.11.7 covers bone marrow lesions.

Gradual change across successive studies rather than a single appearance. 5.17.5 covers post-operative cartilage procedures.

MRCS Level

How It Is Acquired

In a viva the expected opening is the procedure and the date, because neither appearance means anything without them.

The expected points are the procedure and timing, the cartilage sequence and comparison, the fill, the tissue signal, and the subchondral bone.

Say that repair tissue is not native cartilage and does not look like it. 5.11.1 covers normal cartilage.

Say that serial comparison carries more than any single study. 5.17.5 covers post-operative cartilage procedures.

Say that fill is measured and stiffness is not. 5.18.2 covers T2 mapping.

What Normal Looks Like

The reasoning expected is that every repair produces fibrocartilage or a cell-derived matrix rather than native hyaline cartilage, so a different signal is the expected outcome rather than a complication. 1.2.2 covers the articular cartilage.

The property that determines whether the repair survives is its stiffness and its integration with the surrounding cartilage, and neither is visible. 3.5.2 covers the contact pressures.

Subchondral marrow responds to the procedure itself, particularly where marrow was stimulated, so early marrow signal is part of the operation rather than a failure of it. 5.11.7 covers bone marrow lesions.

That leaves fill as the measurable variable, which is why every imaging scoring system for cartilage repair is built around it. 5.21.3 covers the cartilage imaging literature.

How Good It Is

Imaging measures a cartilage repair's fill well and its function not at all.

Its best contribution is the serial trend in fill and in the subchondral bone, which is interpretable where a single appearance is not. 5.17.5 covers post-operative cartilage procedures.

It is limited because fill and durability are weakly related, so a well filled repair and a working one are not the same finding. 5.18.2 covers T2 mapping.

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

FRCS Level

How Good It Is

At decision level the imaging informs a conversation and rarely decides a reoperation.

Complete fill with a continuous surface in a patient doing well is a result, and the imaging confirms what the patient reports. 4.20.5 covers the post-operative cartilage examination.

Absent or minimal fill in a symptomatic patient is a failed repair, and that is a secure imaging finding. 5.11.2 covers chondral defects.

Progressive subchondral change beneath a filled repair is a worse sign than the fill is a good one. 5.11.7 covers bone marrow lesions.

A patient doing badly with a well filled repair has no imaging answer, and this is the common case. 5.1.6 covers imaging pitfalls.

Where It Misleads

The commonest error is reporting expected repair tissue signal as failure. 5.11.1 covers normal cartilage.

Expected early subchondral marrow signal is read as a complication. 5.11.7 covers bone marrow lesions.

The date and the procedure are absent, so the appearance is read against no reference. 5.17.5 covers post-operative cartilage procedures.

Fill is reported as success. 5.18.2 covers T2 mapping.

A single study is read as a trend. 5.20.8 covers common reporting errors.

Fellowship Level

Where It Misleads

At fellowship level cartilage repair is the third place in Section 5 where the same conclusion arrives, and the convergence is the point.

The meniscal repair pages concluded that healing is not measured, the cruciate graft pages concluded that stiffness is not measured, and the cartilage repair pages conclude that the repair tissue's mechanical quality is not measured. 5.6.13 covers meniscal repair imaging.

In each case the measurable surrogate is a morphological one, and in each case the surrogate's relationship to outcome is weak, which suggests the problem is the modality rather than the tissue. 5.7.10 covers graft maturation.

Compositional sequences measure matrix properties and are the obvious candidate, and their values do not transfer between sequences and field strengths, which has kept them inside the centres that developed them. 5.18.2 covers T2 mapping.

Scoring systems for cartilage repair are numerous, built around fill, and not interchangeable, so a score without its system is uninterpretable. 5.21.3 covers the cartilage imaging literature.

The honest position is that imaging documents a cartilage repair and does not evaluate it, and a report that says so is more useful than a score. 5.20.5 covers reporting cartilage lesions.