Meniscal Repair Imaging

For Medical Students

What It Shows

A repaired meniscus has been held together rather than cut away, so the torn surfaces are still present and are expected to heal across. 5.6.4 covers vertical tears.

The repair site keeps a line of altered signal while it heals, and that line can persist for a year or more in a meniscus that is healing normally. 2.5.3 covers the vascular supply.

It matters because the line that means a repair has failed and the line that means a repair is healing look the same on a single study. 5.6.2 covers meniscal signal grading.

How It Is Acquired

Establish when the repair was done, because the same appearance means different things at three months and at three years. 5.17.2 covers the post-operative meniscal repair.

Use the post-operative protocol, since suture material and any implant produce local artefact at exactly the site in question. 5.5.3 covers the post-operative protocol.

Compare with the earliest post-operative study available, which turns the appearance into a trend. 5.20.7 covers reporting the post-operative knee.

Assess for displacement, which is the finding that does not depend on signal. 5.6.6 covers bucket handle tears.

Assess the position of the body, because a repair that has not restored the anchor leaves the meniscus extruded. 5.6.11 covers meniscal extrusion.

What Normal Looks Like

A persistent line of intermediate signal at the repair site, narrower and less fluid-bright than the original tear.

Suture material or implant artefact at the repair, which is the hardware rather than a lesion. 5.2.19 covers artefacts.

A meniscus of normal size and shape in a normal position, which is what the repair was for. 5.6.1 covers the normal meniscus.

Gradual reduction of signal across successive studies, which is the appearance of healing rather than any single image.

What Abnormal Looks Like

Fluid signal as bright as joint fluid filling the repair site and reaching both surfaces, which is a repair that has not healed.

A displaced fragment, which settles the question. 5.6.7 covers flap tears.

Widening of the repair line compared with an earlier study, which is the trend going the wrong way.

Progressive extrusion, which says the repair has not restored the circumferential tension whatever the repair line looks like. 3.6.13 covers the meniscal repair biomechanics.

MRCS Level

How It Is Acquired

In a viva the expected opening is that you cannot read a repair without knowing when it was done.

The expected points are the date of surgery, the post-operative protocol, the comparison study, displacement, the position of the body, and the trend.

Say that persistent signal at a repair site is the normal early finding. 5.6.2 covers meniscal signal grading.

Say that fluid as bright as joint fluid crossing the site is the finding that suggests failure. 5.6.3 covers horizontal tears.

Say that the trend across studies carries more weight than any one appearance. 5.20.7 covers reporting the post-operative knee.

What Abnormal Looks Like

The reasoning expected is that healing across a repair happens from the vascular periphery inwards, so the time course is a tissue property rather than a convention. 2.5.3 covers the vascular supply.

Granulation and fibrous tissue in the healing gap hold water and so carry signal, which is why the line persists in a repair that is working. 2.5.2 covers the histology.

A gap filled with joint fluid rather than tissue is the mechanical failure, and fluid that bright is the observation that distinguishes it.

Repair restores continuity, so it should restore the circumferential tension, and persistent extrusion after repair says it has not. 3.6.2 covers hoop stress.

How Good It Is

Magnetic resonance imaging is poor at calling a repair healed and better at calling one displaced.

Its best contribution is serial comparison, because the direction of change is interpretable where a single appearance is not. 5.20.7 covers reporting the post-operative knee.

It is limited by the long persistence of normal repair signal, by suture artefact, and by the absence of an agreed threshold for a failed repair. 5.2.19 covers artefacts.

No figures appear for accuracy on this page, under decision 028. The claim being made is that displacement is read more reliably than healing, and that is a comparison rather than a number.

FRCS Level

How Good It Is

At decision level the imaging rarely decides whether a repair has healed, and the useful questions are narrower than that.

A displaced fragment in a symptomatic knee after repair has a mechanical answer. 13.7.5 covers failed meniscal repair.

A persistent repair line in a patient who is doing well is not a reason to re-operate, and reporting it as a re-tear invites one. 5.1.6 covers imaging pitfalls.

A root repair is assessed by what happened to the extrusion rather than by the repair line, which makes extrusion the measurement to insist on. 5.17.3 covers the root repair.

Intra-articular contrast changes the reading when the distinction actually matters, and is worth requesting for that narrow question. 5.2.21 covers advanced MRI techniques.

Where It Misleads

The commonest error is reporting a persistent repair line as a re-tear. 5.6.2 covers meniscal signal grading.

The date of surgery is absent, so a normal three month appearance is read as a failure. 5.20.7 covers reporting the post-operative knee.

Suture or implant artefact is read as the lesion it sits on. 5.2.19 covers artefacts.

Extrusion after a root repair goes unmeasured, so the repair's main purpose goes unassessed. 5.6.11 covers meniscal extrusion.

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

Fellowship Level

Where It Misleads

At fellowship level the repaired meniscus is where imaging and the clinical course disagree most often, and the imaging usually loses.

Repairs that look unhealed on magnetic resonance imaging are found intact at arthroscopy often enough that an unhealed appearance alone is a weak basis for re-operation. 13.7.5 covers failed meniscal repair.

There is no agreed imaging definition of healing, so each study in the literature defines it differently and the reported healing rates are not comparable. 5.21.1 covers the meniscal imaging literature.

The time course of normal repair signal is long and variable, which means a single post-operative study is almost always ambiguous. 2.5.3 covers the vascular supply.

Root repair is judged by extrusion, and extrusion is measured supine when the mechanical question is about standing. 5.18.5 covers weight bearing imaging.

Quantitative sequences are proposed for assessing repair tissue and have not displaced the problem, because the question is mechanical rather than compositional. 5.18.1 covers quantitative MRI.