Osteochondral Grafts

For Medical Students

What It Shows

An osteochondral graft transplants a plug of bone with its cartilage, either from the patient or from a donor. 5.11.5 covers osteochondral lesions.

Imaging shows the plug's position, whether its bone has united with the host, and the state of its cartilage surface. 5.5.6 covers the bones.

It matters because the bony union is assessable and the cartilage is mature cartilage from the moment it is placed, which makes this the one cartilage procedure without a maturation phase. 5.11.8 covers cartilage repair procedures.

How It Is Acquired

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

Assess the plug's surface level relative to the surrounding cartilage, since a proud or sunken plug is a mechanical problem. 5.11.2 covers chondral defects.

Assess the bone interface for union, which is the finding unique to this procedure. 5.5.6 covers the bones.

Assess the cartilage surface, which should look like cartilage because it is. 5.11.1 covers normal cartilage.

Assess the donor site where an autograft was used, because it is a second lesion. 5.11.2 covers chondral defects.

What Normal Looks Like

A plug whose cartilage surface is level and continuous with the surrounding cartilage. 5.11.2 covers chondral defects.

Bony union at the interface, with marrow signal crossing it. 5.5.6 covers the bones.

Cartilage of normal appearance on the plug, because it is mature cartilage. 5.11.1 covers normal cartilage.

Resolving subchondral marrow signal across successive studies. 5.11.7 covers bone marrow lesions.

MRCS Level

How It Is Acquired

In a viva the expected answer separates the bony question from the cartilage question.

The expected points are the procedure and date, the surface level, the bone interface, the cartilage surface, and the donor site.

Say that the cartilage is mature and does not need to mature. 5.11.8 covers cartilage repair procedures.

Say that bony union is the assessable outcome. 5.5.6 covers the bones.

Say that an autograft donor site is a second defect. 5.11.2 covers chondral defects.

What Normal Looks Like

The reasoning expected is that the graft carries its own cartilage, so the cartilage's quality was determined before the operation and nothing in the healing improves it. 1.2.2 covers the articular cartilage.

What heals is the bone, and bone to bone union is something imaging assesses reliably, which makes this the cartilage procedure with the most measurable endpoint. 5.5.6 covers the bones.

A proud plug carries the whole compartment's load on a small area and a sunken one carries none, so the surface level is a mechanical measurement rather than a cosmetic one. 3.5.2 covers the contact pressures.

An autograft trades a defect in a loaded area for one in a less loaded area, which is why the donor site belongs in the assessment. 3.5.1 covers the contact areas.

How Good It Is

Imaging assesses this procedure better than any other cartilage repair, because its endpoint is bony.

Its best contribution is bony union and the surface level, both of which are real measurements with mechanical meaning. 5.5.6 covers the bones.

It is limited for the cartilage's long term survival, which depends on its integration at the margins and on the compartment's loading. 5.3.7 covers the mechanical axis.

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

FRCS Level

How Good It Is

At decision level this is the cartilage procedure whose imaging follow up is most worth doing.

Bony union with a level surface in a patient doing well is a documented result. 4.20.5 covers the post-operative cartilage examination.

Non-union at the interface is a mechanical failure with a surgical answer. 5.5.6 covers the bones.

A proud or sunken plug is a mechanical problem identified by a measurement rather than an impression. 5.11.2 covers chondral defects.

Compartment malalignment loading the graft is a cause of failure that the graft imaging will not show, so the alignment film belongs in the assessment. 5.3.7 covers the mechanical axis.

Where It Misleads

The commonest error is not assessing the surface level. 5.11.2 covers chondral defects.

The bone interface is not examined, so non-union is missed. 5.5.6 covers the bones.

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

The donor site is not assessed after an autograft. 5.11.2 covers chondral defects.

Alignment is left out of the assessment. 5.3.7 covers the mechanical axis.

Fellowship Level

Where It Misleads

At fellowship level this procedure is the exception that proves the chapter's argument, because its endpoint is bone.

Every other cartilage repair in this chapter is followed by measuring a morphological surrogate for a mechanical property, and this one is followed by measuring bony union, which is the property that matters and is directly visible. 5.11.8 covers cartilage repair procedures.

That is why the imaging follow up here is more useful than for the cell based procedures, and it is a consequence of the surgery rather than of better imaging. 5.11.9 covers ACI imaging.

The cartilage's own fate still depends on its integration and on the compartment's loading, so the part of the result imaging assesses well is the part that fails least often. 5.3.7 covers the mechanical axis.

Allograft adds a viability question that morphological imaging does not answer, and contrast enhanced assessment of it has not become routine. 5.2.21 covers advanced magnetic resonance techniques.

The chapter closes where it opened: imaging shows cartilage's shape, the question is its mechanics, and the one procedure imaging follows well is the one whose endpoint is not cartilage at all. 5.11.1 covers normal cartilage.