MACI Imaging

For Medical Students

What It Shows

Matrix assisted autologous chondrocyte implantation seeds cells on a membrane which is then fixed into the defect. 5.11.9 covers ACI imaging.

Imaging shows the fill, the surface, the repair tissue and the bone beneath, as for any cartilage repair. 5.11.8 covers cartilage repair procedures.

It matters because the membrane adds one question the earlier technique did not have, which is whether it has remained in place. 5.11.4 covers delamination.

How It Is Acquired

Establish the date and the procedure, as for any cartilage repair. 5.17.5 covers post-operative cartilage procedures.

Use a cartilage sensitive sequence consistently across follow ups. 5.2.18 covers gradient echo imaging.

Assess the fill and the surface level. 5.11.2 covers chondral defects.

Assess the deep interface specifically, because membrane detachment appears there rather than at the surface. 5.11.4 covers delamination.

Assess the subchondral bone, as for the earlier technique. 5.11.7 covers bone marrow lesions.

What Normal Looks Like

A filled defect with a surface roughly level with the surrounding cartilage. 5.11.2 covers chondral defects.

Repair tissue signal unlike native cartilage, maturing across studies. 5.11.1 covers normal cartilage.

An intact deep interface with no fluid between the repair and the bone. 5.11.4 covers delamination.

Subchondral marrow signal in the early period. 5.11.7 covers bone marrow lesions.

MRCS Level

How It Is Acquired

In a viva the expected answer names the one difference from the earlier technique.

The expected points are the date and procedure, the consistent sequence, the fill, the deep interface, and the subchondral bone.

Say that the deep interface is the added question. 5.11.4 covers delamination.

Say that the maturation timescale is long, as before. 5.11.9 covers ACI imaging.

Say that an intact surface does not exclude detachment. 5.11.4 covers delamination.

What Normal Looks Like

The reasoning expected is that the construct is fixed to the bed rather than grown from it, so its failure mode includes losing that fixation, which the earlier technique's failure modes did not include in the same way. 5.11.9 covers ACI imaging.

Detachment presents as fluid at the deep interface with the surface continuous, which is the same appearance as native cartilage delamination and is assessed the same way. 5.11.4 covers delamination.

Because an intact surface conceals it, the lesion is missed unless the interface is examined deliberately, which is the practical point of the page. 5.11.1 covers normal cartilage.

Everything else, the maturation, the signal and the subchondral response, behaves as the earlier technique does. 5.11.8 covers cartilage repair procedures.

How Good It Is

Imaging assesses this repair as it assesses the earlier one, with one extra finding it can detect that nothing else can.

Its best contribution is detecting membrane detachment at the deep interface, which an arthroscopic probe on an intact surface can miss. 5.11.4 covers delamination.

It is limited in the same way as the earlier technique, because mechanical quality remains invisible. 5.18.2 covers T2 mapping.

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

FRCS Level

How Good It Is

At decision level this page adds one actionable finding to the cartilage repair assessment.

Detachment in a symptomatic patient is a mechanical failure with a surgical answer, and the imaging is how it is found. 5.11.4 covers delamination.

Progressive fill with an intact interface is the expected course. 5.11.8 covers cartilage repair procedures.

Progressive subchondral deterioration is the worrying pattern, as for the earlier technique. 5.11.7 covers bone marrow lesions.

A symptomatic patient with a well filled and well attached repair has no imaging answer. 5.1.6 covers imaging pitfalls.

Where It Misleads

The commonest error is not examining the deep interface. 5.11.4 covers delamination.

An intact surface is taken to mean an attached construct. 5.11.1 covers normal cartilage.

A partial volume line at the interface is reported as detachment. 5.2.5 covers magnification.

Expected repair signal is reported as failure. 5.11.8 covers cartilage repair procedures.

The date is absent and the maturation cannot be judged. 5.17.5 covers post-operative cartilage procedures.

Fellowship Level

Where It Misleads

At fellowship level this technique shows how a change in surgical method creates an imaging question, and how slowly the reporting follows.

The membrane introduced a failure mode at the deep interface, and the reporting templates inherited from the earlier technique focus on fill and surface, so the new question is not asked by default. 5.20.5 covers reporting cartilage lesions.

Detachment and native cartilage delamination are the same appearance, so the skill already exists and is applied in one setting and not the other. 5.11.4 covers delamination.

Scoring systems carried over from the earlier technique do not include attachment, which means a repair can score well and be detached. 5.21.3 covers the cartilage imaging literature.

Everything the earlier technique's page says about maturation, surrogates and the weak relationship to outcome applies unchanged, so the addition is a finding rather than a solution. 5.11.9 covers ACI imaging.

The practical recommendation is to add the deep interface to the report as a named observation. 5.20.5 covers reporting cartilage lesions.