ACL Retear After Reconstruction: Why Does Revision Surgery Sometimes Require Osteotomy?

Basketball, football and skiing involve sudden stops, landing from jumps and rapid turns. A further substantial twisting force can damage the reconstructed ligament.

Returning to high-intensity sport too early may increase reinjury risk, particularly before muscle strength, balance and neuromuscular control have adequately recovered.

Reconstruction requires tunnels in the femur and tibia to accommodate the tendon graft, which is secured in the appropriate position with fixation devices.

If the tunnels are away from the ligament’s anatomical attachment sites, the graft may experience abnormal tension during certain movements or impinge against surrounding bone.

Inadequate fixation or poor healing may also affect stability after reconstruction.

Some patients have varus or valgus alignment, or an excessive posterior tibial slope. These features can alter knee loading during movement and expose the ACL to sustained higher loads.

Even after a new ligament is implanted, persistent causes of increased loading may continue to affect the graft adversely.

The menisci help stabilise the knee as well as distribute load. Injury to a meniscal posterior root, posterior horn or another important structure may place greater stabilising demands on the ACL.

If other ligaments are also lax or injured, ACL reconstruction alone may not restore normal stability.

A graft retear therefore requires reassessment of its causes, including the original surgical technique, bony anatomy, meniscal condition and the patient’s sporting needs.

The tibial plateau is the joint surface at the top of the tibia that contacts the femur.

Viewed from the side, it normally slopes backwards to some degree. This angle is called the posterior tibial slope (PTS).

Think of it as a platform tilted slightly backwards. Standing, walking and landing from a jump produce complex forces between the femur and tibia.

If the backward slope is pronounced, the tibia may move forwards relative to the femur more readily under certain loading conditions.

One of the ACL’s important functions is to restrain this excessive forward movement.

A greater slope may therefore increase tension in the ACL or graft. Biomechanical experiments have found that, under specific conditions, reducing an excessive slope through osteotomy can decrease anterior tibial translation and graft forces.

A value of 12° is often used as a clinical reference. The European Society of Sports Traumatology, Knee Surgery and Arthroscopy (ESSKA) revision consensus suggests considering slope-reducing osteotomy after failed primary ACL reconstruction when the posterior tibial slope is 12° or greater.

Marked anterior tibial translation, repeated reconstruction failures or loss of medial meniscal posterior horn function may strengthen the clinical case for osteotomy.

However, 12° is not an absolute surgical threshold. The measurement method, knee hyperextension, sporting demands and other stability factors also need assessment.

Varus alignment typically gives the legs a bowed, or “O-shaped”, appearance.

Some patients bear greater load on the inner side of the knee. Coexisting medial meniscal deficiency, cartilage damage or ligament insufficiency may allow this abnormal loading to further affect function and stability.

Appropriate alignment correction can redistribute loading between the medial and lateral compartments and may improve the associated mechanics.

Valgus alignment typically brings the knees inwards, giving the legs an “X-shaped”, or knock-kneed, appearance.

Marked valgus can also alter load distribution. Correction may be considered when ligament insufficiency, cartilage injury or meniscal damage coexist.

The ESSKA consensus suggests considering correction when varus or valgus deviation reaches approximately 5° alongside early osteoarthritis, substantial cartilage injury, symptomatic meniscal deficiency or associated ligament instability.

Selected patients may warrant assessment for osteotomy even with a deviation below 5°.

Mild varus alone, without related symptoms or structural damage, does not mean osteotomy is required.

Correcting varus or valgus and reducing posterior tibial slope are also different surgical goals. Some patients have both abnormalities and need more complex planning.

With a large slope, especially 12° or greater, together with reconstruction failure, marked anterior tibial translation or other risk factors, slope-reducing osteotomy may be considered.

After two or more failed reconstructions, potential biomechanical problems need a particularly comprehensive review.

Repeatedly replacing the graft may not adequately address abnormal loading, making assessment of alignment and plateau shape especially important.

For marked varus or valgus accompanied by meniscal deficiency, cartilage damage or instability, osteotomy may form part of the overall treatment.

In some patients, the tibia sits relatively far forwards even during quiet standing.

A large slope or deficient medial meniscal posterior horn function may increase concern about the effect of bone angles on the graft.

Patients with marked knee hyperextension, serious bone-quality problems or other factors increasing osteotomy risk require cautious assessment.

This means dealing with the old graft, adjusting tunnels, and inserting and fixing the new graft during one procedure.

It is generally suitable when tunnel conditions allow reliable fixation and severe bone loss does not first require bone grafting.

Markedly widened or malpositioned tunnels, or substantial bone loss, may require revision in two operations.

The first stage mainly addresses the old graft, existing fixation and abnormal tunnels, with tunnel bone grafting when appropriate.

After the grafted bone has gradually healed with the surrounding bone, the second-stage ligament reconstruction is performed.

Staged revision and adding an osteotomy are separate decisions. The former concerns the timing of tunnel restoration and ligament reconstruction; the latter corrects bone angles or alignment. Some patients can undergo osteotomy and reconstruction together, while others need stages according to bone conditions.