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KneeSchool/Biomechanics Academy/Lateral Extra-articular Tenodesis

Lateral Extra-articular Tenodesis

Page 3.11.7 · Anterolateral Complex Biomechanics · biomechanics page

A strip of the iliotibial band, routed deep to the collateral and fixed to the femur. An old operation whose mechanics are better understood than they were.

Pipeline status. Editorial draft. Evidence verification did not run. Not consultant reviewed. Not for clinical use.

The same topic at 4 depths

Each tier deepens the one below it and never repeats it. Choose the level you want.

Lateral Extra-articular Tenodesis

Choose a depth

For Medical Students

The Principle

Taking a strip of a nearby structure and fixing it across a joint creates a new restraint without needing a separate graft.

Where it is fixed decides what it restrains. A strip fixed to the bone above the joint restrains the bone below it.

The route it takes decides its line of action, and the line of action decides which motion is limited.

At the Knee

A lateral extra-articular tenodesis takes a strip of the iliotibial band, leaves it attached distally at Gerdy's tubercle, and fixes it to the distal lateral femur. 2.11.1 covers the band.

It is routed deep to the lateral collateral ligament, which sets its line of action. 3.10.3 covers that ligament.

Its job is to restrain internal rotation of the tibia, which the cruciate graft does less completely. 3.11.5 covers internal rotation control.

It is extra-articular, so it stays outside the joint and does not replace the cruciate. It is an addition rather than an alternative.

What Changes It

Where it is fixed on the femur, which decides what it restrains.

Whether it is routed deep or superficial to the collateral.

Graft tension and the tibial rotation at fixation.

The width of strip taken.

Clinical Relevance

It is added to a cruciate reconstruction rather than used alone, because it does not restrain translation. 3.11.8 covers the combined reconstruction.

Conventional teaching adds it in high grade rotatory laxity, revision, young pivoting athletes and generalised laxity. Section 6 covers management.

Over-tensioning restricts internal rotation, which is the error to avoid. 3.11.5 covers that.

7.30 covers the technique.

Key Learning Points

  • A strip of a nearby structure can create a restraint without a separate graft.
  • Where it is fixed decides what it restrains.
  • The route decides the line of action, which decides the motion limited.
  • It is routed deep to the lateral collateral and fixed to the distal lateral femur.
  • It is an addition to a cruciate reconstruction rather than an alternative.

MRCS Level

The Principle

A tenodesis restrains a motion; an anatomic reconstruction reproduces a structure. The distinction matters because a tenodesis can work without corresponding to any native anatomy. 3.11.3 covers the anatomic alternative.

Its mechanics are set by three things: femoral fixation position, route, and tension at fixation. None of them depends on what the native structure was.

That is why the operation predates the anatomical argument and survived it.

At the Knee

Conventional teaching describes several variants, with the Lemaire and the MacIntosh procedures and their modifications the most cited, differing in strip length, route and fixation.

Fixation is conventionally proximal and posterior to the lateral collateral's femoral origin, which places it in the Kaplan fibre region. 3.11.2 covers those fibres.

Routing deep to the lateral collateral gives a line of action that restrains internal rotation; routing superficial changes it and is not conventional.

Robotic testing shows it restraining internal rotation and the simulated pivot shift, with over-constraint at higher tensions. 3.11.5 covers over-constraint.

What Changes It

Fixation position on the femur.

Route relative to the collateral.

Tension and tibial rotation at fixation.

Variant used and strip dimensions.

How It Is Measured

Robotic testing compares variants and tensions against the intact knee.

Instrumented pivot shift measures the clinical effect without a threshold.

Randomised trials measure reinjury rates, which is the strongest clinical evidence.

Range of motion and lateral compartment imaging assess the over-constraint risk clinically.

Clinical Relevance

Fix proximal and posterior to the collateral's origin.

Route deep to the collateral, which is what sets the line of action.

Tension modestly and fix with the tibia neutral.

Judge the variant by trial evidence as well as by cadaveric performance.

Key Learning Points

  • A tenodesis restrains a motion; an anatomic reconstruction reproduces a structure.
  • Its mechanics are femoral fixation, route and tension, none anatomy dependent.
  • That is why the operation predates the anatomical argument and survived it.
  • Fixation is proximal and posterior to the collateral's origin, in the Kaplan region.
  • Over-constraint appears at higher tensions in robotic testing.

FRCS Level

At the Knee

Treat the tenodesis as the augmentation with the strongest clinical evidence and the weakest anatomical rationale, and treat that combination as acceptable. 3.11.9 covers the controversies.

Conventional teaching now supports adding it in defined groups on randomised trial evidence of reduced graft failure, which is a stronger basis than the mechanism alone would give.

The historical objection was stiffness and lateral compartment degeneration, and conventional teaching reports that trials have not borne it out at the tensions and routes now used. 3.11.5 covers over-constraint.

What Changes It

The group it is applied to, which is where the trial evidence applies.

Fixation, route and tension.

Cruciate graft position, since the constructs interact. 3.7.20 covers that.

Bony morphology, which sets the rotational demand. 3.13 covers alignment.

How It Is Measured

Randomised trials report graft failure and reinjury, which is the primary evidence.

Instrumented pivot shift measures the mechanism's effect in cohorts.

Range of motion and imaging assess the historical objections.

Robotic testing establishes the tension and route that avoid over-constraint.

Clinical Relevance

Add it in the groups the trial evidence covers rather than universally.

Tension modestly and route deep, which is what the cadaveric work supports.

State that the stiffness objection has not been borne out at current tensions.

Plan it alongside the cruciate graft rather than as an afterthought.

Key Learning Points

  • Strongest clinical evidence, weakest anatomical rationale, and that is acceptable.
  • Randomised trial evidence of reduced graft failure is a stronger basis than mechanism.
  • The historical objection was stiffness and lateral compartment degeneration.
  • Trials have not borne it out at the tensions and routes now used.
  • Apply it in the groups the trial evidence covers.

Fellowship Level

At the Knee

At fellowship level the question is who gets one, and the honest answer is that the indications are a list rather than a principle: high grade rotatory laxity, revision, young pivoting athletes, generalised laxity, and increased posterior tibial slope. 3.11.9 covers the debate.

Each item on the list is a statement about rotational demand or about rotational restraint, which is the principle the list is a proxy for. 3.11.5 covers internal rotation control.

The practical constraints are femoral fixation crowding and the interaction with the cruciate graft's tunnel. 3.11.2 covers the fixation region.

What Changes It

Which indications the patient meets.

Femoral fixation space and previous hardware.

Slope, and whether it is being corrected instead or as well.

Graft and strip availability.

How It Is Measured

Trial subgroup data informs the indications, with the subgroups small.

Computed tomography planning assesses femoral fixation and convergence.

Instrumented pivot shift measures the effect in research cohorts.

No measurement identifies the individual who needs one.

Clinical Relevance

Apply the indications as proxies for rotational demand and restraint.

Plan femoral fixation alongside the cruciate tunnel.

Consider slope correction as an alternative or an addition in the right knee.

State that no measurement identifies the individual who needs one.

Key Learning Points

  • The indications are a list rather than a principle.
  • Each item is a statement about rotational demand or restraint.
  • That is the principle the list is a proxy for.
  • Femoral fixation crowding and cruciate tunnel interaction are the practical constraints.
  • No measurement identifies the individual who needs one.

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. Every measurement on this page is written from standard teaching rather than from a retrieved paper, and none has been checked against a source. Under decision 006 each one is registered in pipeline/config/figures with the sentence it supports and a verification state of UNVERIFIED_FROM_MEMORY, so the whole list can be checked and corrected rather than hunted for.

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