Osteotomy Planning

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Student MRCS FRCS Fellow

For Medical Students

What It Shows

Osteotomy planning establishes where a limb's deformity sits and how much correction is needed. 5.3.10 covers the deformity analysis.

The plan is built on a weight bearing long leg radiograph, with computed tomography added for rotation and for the joint surface. 5.3.6 covers the long leg alignment films.

It matters because an osteotomy moves load from one compartment to another, and the amount moved is set by the geometry. 5.3.7 covers the mechanical axis.

How It Is Acquired

Start from a standing long leg film, because the deformity that matters is the loaded one. 5.3.6 covers the long leg alignment films.

Establish whether the deformity is femoral, tibial or both. 5.3.8 covers the anatomical axis.

Establish whether it is intra-articular, since a bone cut cannot correct a worn surface. 5.3.9 covers the joint line obliquity.

Add computed tomography where rotation or the articular surface is part of the deformity. 5.16.3 covers the rotational profiles.

Record the compartment that will receive the load after correction. 5.3.17 covers joint space narrowing.

What Normal Looks Like

A standing film that includes the hip and the ankle. 5.3.6 covers the long leg alignment films.

Both the femoral and the tibial contribution stated separately. 5.3.8 covers the anatomical axis.

The joint line orientation measured and stated. 5.3.9 covers the joint line obliquity.

The receiving compartment documented as preserved. 5.3.17 covers joint space narrowing.

The patellofemoral joint assessed, because a tibial correction moves it too. 5.12.7 covers the patellofemoral arthritis.

What Abnormal Looks Like

A deformity attributed to the tibia when the femur carries part of it. 5.3.10 covers the deformity analysis.

An intra-articular deformity planned as though it were extra-articular. 5.3.9 covers the joint line obliquity.

Rotation unmeasured in a limb being corrected in one plane. 5.16.3 covers the rotational profiles.

A receiving compartment already worn, which turns a correction into a transfer of pain. 5.3.17 covers joint space narrowing.

Planning done on a supine study, which loses the load. 5.1.6 covers imaging pitfalls.

Key Learning Points

The deformity that matters is the loaded one.
The femoral and tibial contributions are stated separately.
A bone cut cannot correct a worn surface.
Rotation belongs in the plan when it is part of the deformity.
The receiving compartment has to be preserved.

MRCS Level

How It Is Acquired

In a viva the expected answer plans on the standing film and adds the scan for a stated reason.

The expected points are the standing long leg film, the level of the deformity, the intra-articular component, the rotation, and the receiving compartment.

Say that a supine study cannot carry the alignment question. 5.3.6 covers the long leg alignment films.

Say that computed tomography contributes rotation and surface rather than alignment. 5.16.3 covers the rotational profiles.

Say that the patellofemoral joint changes with a tibial correction. 3.12.12 covers the tibial tubercle position.

What Normal Looks Like

The reasoning expected is that the correction is calculated from the mechanical axis and the joint line, so the film has to contain both the hip and the ankle to be usable at all. 5.3.7 covers the mechanical axis.

Deformity analysis localises the apex, and correcting at the wrong level restores the axis while leaving the joint line oblique. 5.3.9 covers the joint line obliquity.

A rotational component corrected only in the coronal plane leaves the limb malrotated. 5.16.3 covers the rotational profiles.

The soft tissue and the ligament state decide whether the corrected limb is stable, and the scan does not carry that. 5.5.9 covers the ligaments.

How Good It Is

Radiographic planning is the best available method for a knee osteotomy, and computed tomography is the best available addition to it.

Its best contribution is the loaded mechanical axis with the deformity localised. 5.3.7 covers the mechanical axis.

It is limited by positioning on the standing film, by supine scanning, and by the soft tissues it cannot assess. 5.3.6 covers the long leg alignment films.

No figures appear for accuracy on this page, under decision 028, and no correction values, axis angles or planning thresholds appear either: those are published quantities tied to particular techniques and this environment cannot check them.

Key Learning Points

The film has to contain the hip and the ankle.
Correcting at the wrong level leaves the joint line oblique.
A coronal correction leaves rotation uncorrected.
The ligament state decides stability after correction.
Positioning on a standing film is a real limitation.

FRCS Level

How Good It Is

At decision level the imaging decides the level, the plane and the size of the correction. 5.3.10 covers the deformity analysis.

It also decides against an osteotomy, when the receiving compartment or the patellofemoral joint rules one out. 5.12.7 covers the patellofemoral arthritis.

A tubercle transfer is planned from the same geometry and interacts with any tibial correction. 5.16.4 covers the TT-TG measurement.

A rotational correction is planned from the scan and changes the coronal plan. 5.16.3 covers the rotational profiles.

The post-operative imaging has to repeat the same measurements by the same method to mean anything. 5.17.4 covers the osteotomy.

Where It Misleads

The commonest error is planning from a film that does not include both joints. 5.3.6 covers the long leg alignment films.

Rotation of the limb on the standing film changes the apparent deformity. 5.1.6 covers imaging pitfalls.

Flexion on the standing film shortens the apparent femur and alters the axis. 5.3.8 covers the anatomical axis.

A supine scan is used to confirm an alignment measured standing, and the two disagree legitimately. 5.18.5 covers weight-bearing MRI.

An intra-articular deformity is corrected extra-articularly, which moves the load without levelling the surface. 5.3.9 covers the joint line obliquity.

Key Learning Points

A film without both joints cannot be planned from.
Limb rotation changes the apparent deformity.
Flexion on the film alters the measured axis.
A supine scan and a standing film disagree legitimately.
An extra-articular correction does not level an intra-articular deformity.

Fellowship Level

Where It Misleads

At fellowship level the limb has usually been corrected once already and the question is what remains. 5.17.4 covers the osteotomy.

A previous correction moves the reference points, so the pre-operative films are the only comparable ones. 5.12.8 covers the post-operative imaging.

Deformity in three planes is planned plane by plane, and the planes interact. 5.3.10 covers the deformity analysis.

A limb corrected into a position the ligaments cannot hold looks correct on the film. 5.5.9 covers the ligaments.

Planning software fixes the landmark rules, which removes variability and hides the uncertainty in the landmarks themselves. 5.18.8 covers artificial intelligence in imaging.

The useful report gives the standing film with both joints, the deformity localised, the intra-articular component, the rotation, the receiving compartment, and the patellofemoral joint. 5.20.1 covers structured reporting.

Key Learning Points

A previous correction moves the reference points.
The planes interact and are planned separately.
A film cannot show whether the ligaments hold the correction.
Software removes variability and hides landmark uncertainty.
The report should state the receiving compartment.

Explore Further

Where this topic came from and where it goes next in the spiral.

References

No reference list is attached to this draft. Evidence verification has not run, because source retrieval was unavailable at generation time. Under the Operations Handbook a missing reference is acceptable and an invented one is a critical failure, so nothing has been cited and no citation marker appears in the text. This page carries no diagnostic accuracy figure, which is decision 028 rather than an omission: the comparative standing of the modalities is standard teaching and a specific sensitivity written from memory is the same class of claim as an invented citation, so ACC-001 refuses the number and the page states the comparison. A reviewer with the literature can add the figures into How Good It Is without restructuring the page. Any measurement here, including a sequence parameter, an angle or a millimetre, is written from standard teaching, has not been checked, and is registered under decision 006 in pipeline/config/figures with a verification state of UNVERIFIED_FROM_MEMORY.

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