Fracture Assessment

For Medical Students

What It Shows

Computed tomography shows the cortical outline and the articular surface of a knee fracture in any plane, from one acquisition. 5.2.22 covers the CT acquisition.

It shows the number of fragments, where each one sits, and how far the articular surface has been depressed. 5.3.11 covers tibial plateau fractures.

It matters because the fracture is usually already visible on the radiograph, and what changes with the scan is how the injury is classified. 5.3.1 covers the AP view.

How It Is Acquired

Request it after the radiographs rather than instead of them, because the radiograph decides whether the scan is needed. 5.1.3 covers choosing the correct investigation.

Acquire thin slices through the joint, since a reformat can only be as good as the slice it was built from. 5.2.23 covers the reconstruction.

Review the axial images alongside coronal and sagittal reformats rather than one plane alone. 5.2.23 covers the reconstruction.

Assess the articular surface separately from the metaphysis, because they drive different decisions. 2.2.2 covers the tibial plateau.

Record the dose, since this is a higher dose study than the radiographs it follows. 5.2.24 covers the radiation dose.

What Normal Looks Like

A continuous cortical outline on every reformat. 2.1.8 covers the imaging anatomy.

An articular surface at an even level across the plateau and the condyles. 2.2.2 covers the tibial plateau.

A trabecular pattern without the impaction lines of a compression injury. 5.13.3 covers stress fractures.

No fragment separate from the bone it belongs to. 5.3.14 covers avulsion injuries.

What Abnormal Looks Like

A cortical break traced across consecutive slices rather than seen on one. 5.3.13 covers femoral condyle fractures.

Articular depression measured from the surrounding intact surface. 2.2.2 covers the tibial plateau.

The number and position of the fragments, including those hidden on the radiograph. 5.3.11 covers tibial plateau fractures.

An avulsion at a ligament attachment, which points at the ligament rather than the bone. 5.3.14 covers avulsion injuries.

Impaction with no cortical break, which a radiograph can miss entirely. 5.13.3 covers stress fractures.

MRCS Level

How It Is Acquired

In a viva the expected answer requests the radiographs first and says why.

The expected points are the radiographs first, the thin slices, all three planes, the articular surface, and the dose.

Say that the radiograph establishes the injury and the scan characterises it. 5.3.1 covers the AP view.

Say that a reformat cannot recover detail the acquisition did not capture. 5.2.23 covers the reconstruction.

Say that the scan shows bone and says nothing about the ligaments. 5.5.9 covers the ligaments.

What Abnormal Looks Like

The reasoning expected is that an operation on an articular fracture is planned around fragment position and surface depression, neither of which a single projection can give. 5.3.11 covers tibial plateau fractures.

Depression is measured against the intact surface nearby, so the reference matters as much as the figure. 2.2.2 covers the tibial plateau.

A posterior fragment is the one a lateral radiograph understates and the one that changes the approach. 5.3.2 covers the lateral view.

An avulsion fracture is a ligament injury carrying a piece of bone, so the report should name the ligament. 5.3.15 covers Segond fractures.

How Good It Is

Computed tomography is the best available test of fracture architecture in the knee and adds nothing about the soft tissues.

Its best contribution is fragment position and articular depression, which decide the approach. 5.3.11 covers tibial plateau fractures.

It is limited by soft tissue contrast, by the dose, and by a normal scan not meaning an uninjured knee. 5.5.9 covers the ligaments.

No figures appear for accuracy on this page, under decision 028, and no slice thicknesses, dose values or depression thresholds appear either: those are local protocol and published quantities and this environment cannot check them.

FRCS Level

How Good It Is

At decision level the scan is requested to choose an approach and a fixation, so a report listing fragments without their positions has not helped. 5.20.8 covers common reporting errors.

The articular surface decides whether the operation is a reduction or an augmentation. 2.2.2 covers the tibial plateau.

The posterior structures decide whether the approach is anterior at all. 5.3.2 covers the lateral view.

A magnetic resonance study is added when the ligaments and menisci change the plan, which in these injuries is often. 5.5.1 covers the standard protocol.

The dose is justified by the plan that follows it rather than by completeness. 5.1.5 covers the cost-effectiveness of imaging.

Where It Misleads

The commonest error is reading a bone scan as a knee assessment. 5.5.9 covers the ligaments.

Thick slices produce a stair artefact at an oblique surface, which is read as a step in the articular surface. 5.2.23 covers the reconstruction.

Metal or motion degrades the study where the question sits. 5.2.19 covers the artefacts.

A fracture reduced by the position on the table is reported as a reduced fracture. 5.1.6 covers imaging pitfalls.

An old healed injury is reported as acute, because the scan carries no interval. 5.13.3 covers stress fractures.

Fellowship Level

Where It Misleads

At fellowship level the scan arrives with the patient and the first fixation has already been done elsewhere. 5.20.7 covers reporting the post-operative knee.

The pre-operative anatomy cannot be recovered from a scan taken after fixation, which makes the original study the more valuable one to obtain. 5.12.8 covers the post-operative imaging.

Classification systems were built on radiographs and on scans from earlier eras of resolution, so a modern scan reclassifies the injuries those systems were calibrated on. 5.3.11 covers tibial plateau fractures.

Automated fracture detection performs on the obvious injuries and is weakest on the impaction that changes the plan. 5.18.8 covers artificial intelligence in imaging.

Repeat scanning through a treatment course accumulates dose in a population that is often young. 5.2.24 covers the radiation dose.

The useful report gives the fragments with their positions, the surface with its reference, the dose, and the soft tissue question stated as open. 5.20.1 covers structured reporting.