Osteotomy

For Medical Students

What It Tests

An osteotomy moves load from a worn compartment to a less worn one by changing the alignment, so the examination is checking the correction, the healing and the symptoms. 4.5.1 covers the mechanical axis.

The examination's reference is the intended alignment rather than a neutral limb, because an osteotomy is often planned to overcorrect slightly. 4.3.3 covers standing alignment.

It matters that the operation treats the load rather than the surface, so the examination of the compartment continues afterwards. 4.18.3 covers the varus worn knee.

How It Is Performed

Establish which osteotomy was done, at which bone, in which direction and when. 4.2.30 covers previous surgery.

Look at the scars and ask about metalwork, since prominent metalwork produces its own symptoms. 4.3.7 covers surgical scars.

Assess the alignment standing from the front, comparing it with the other limb and with the intended correction. 4.3.3 covers standing alignment.

Watch the gait for a residual thrust, since a thrust after correction suggests an undercorrection or a lax side. 4.4.6 covers the arthritic gait.

Measure the range, since an osteotomy can change the flexion available and the extension. 4.7.10 covers the post operative range assessment.

Palpate the osteotomy site for tenderness, which raises delayed union. 4.6.1 covers systematic palpation.

Palpate the compartment joint lines, because the original compartment and the newly loaded one both matter now. 4.6.4 covers joint line tenderness.

Assess the collateral ligaments, since correcting the bone changes their tension. 4.12.1 covers valgus stress testing.

What a Positive Means

A corrected alignment with a healed site, a settled range and reduced compartment pain is the expected result.

Tenderness at the osteotomy site beyond the expected healing period raises delayed or non union. 4.6.1 covers systematic palpation.

A residual thrust suggests the correction was insufficient or the opposite side is lax. 4.4.6 covers the arthritic gait.

Pain appearing in the newly loaded compartment suggests overcorrection or that compartment was worse than assessed. 4.18.4 covers the valgus worn knee.

A corrected alignment with persistent compartment pain suggests the surface damage is the symptom source rather than the load. 4.17.5 covers articular cartilage defects.

MRCS Level

How It Is Performed

In a viva this is the post osteotomy station and the expected answer examines both compartments and the osteotomy site.

The expected points are the osteotomy and its date, the scars and metalwork, the standing alignment against the intended correction, the gait, the range, the osteotomy site, both joint lines, and the collaterals.

Say that you would assess the alignment standing, since the correction is a loaded measurement. 4.3.3 covers standing alignment.

Say that you would examine the newly loaded compartment as well as the original one. 4.6.4 covers joint line tenderness.

Say that you would palpate the osteotomy site, because union is part of the assessment. 4.6.1 covers systematic palpation.

What a Positive Means

The reasoning expected is that load passes through the compartment the mechanical axis crosses, so moving the axis moves the load. 3.13.9 covers osteotomy biomechanics.

A slight overcorrection is often planned, because the dynamic load during gait is greater than the static alignment predicts. 3.13.10 covers alignment correction principles.

Correcting the bone alters the collateral tension, so the ligament findings after an osteotomy differ from those before it. 3.9.1 covers valgus stability.

Changing the alignment does not repair the surface, which is why compartment pain can persist after a technically good correction. 3.13.8 covers alignment and arthritis.

How Good It Is

The examination establishes the correction, the union and the symptom pattern reliably.

Its best contribution is the gait and the standing alignment together, since the dynamic finding is what a static film does not show. 4.4.6 covers the arthritic gait.

It estimates rather than measures the correction, which the long leg film quantifies.

Long leg films measure the mechanical axis, so the examination contributes the dynamic and symptomatic findings. 4.1.6 covers that relationship.

No figures appear for any accuracy comparison on this page, under decision 023, and the comparison is the claim being made.

FRCS Level

How Good It Is

At decision level the examination separates an undercorrected limb, a deteriorating compartment, a non union and a surface problem.

A residual thrust with persistent compartment pain suggests undercorrection, and the examination is where that is identified. 4.4.6 covers the arthritic gait.

Pain in the opposite compartment after correction suggests the load has been moved too far, and the examination localises it. 4.6.4 covers joint line tenderness.

Tenderness and pain on loading at the osteotomy site raise non union, which changes the plan entirely. 4.6.1 covers systematic palpation.

An osteotomy that has worked mechanically and failed symptomatically moves the discussion to the joint surface. 4.18.2 covers established disease.

Where It Misleads

The commonest error is assessing the alignment supine, where a correction looks different from under load. 4.3.3 covers standing alignment.

The correction is compared against a neutral limb rather than against the plan, so a deliberate overcorrection is called an error. 4.5.1 covers the mechanical axis.

Metalwork tenderness is attributed to the joint. 4.3.7 covers surgical scars.

Collateral findings are compared against the preoperative examination, which the correction has invalidated. 4.12.1 covers valgus stress testing.

A persistent effusion is attributed to the osteotomy when the compartment is the source. 4.8.3 covers the bulge sign.

Fellowship Level

Where It Misleads

At fellowship level the examination after an osteotomy is checking a plan, and its weakness is that it cannot measure what the plan specified.

The intended correction is a radiographic quantity and the examination estimates it, so the two are compared rather than substituted. 4.5.1 covers the mechanical axis.

An osteotomy changes the joint line obliquity as well as the axis, and the examination does not describe obliquity at all. 4.3.3 covers standing alignment.

Collateral tension after correction can be asymmetric in a way that is neither laxity nor normal, which leaves the ligament findings hard to classify. 4.12.1 covers valgus stress testing.

Pain can arise from the bone, the metalwork, the original compartment, the newly loaded compartment or the patellofemoral joint, and the examination separates some of those and not all. 4.15.9 covers patellofemoral pain.

An osteotomy changes the patellar height relationship in some techniques, and the examination does not detect that. 4.15.1 covers patellar tracking.