Foot drop surgery

What is foot drop surgery?

The principle behind foot dorsiflexor surgery is to restore a foot extension mechanism during walking, preventing it from catching. This involves transferring a tendon around the ankle to substitute the deficient muscle that enables the foot to be lifted.

Depending on the clinical situations, the procedure may vary while keeping the same principle. The tendon transfer performed to lift the foot can work in two ways: by tenodesis effect or by active effect.

Muscle grading is generally done on a scale from 0 to 5. 0 corresponds to the absence of visible or felt muscle contraction, 5 corresponds to normal muscle strength.

When a tendon is transferred, muscle strength decreases by one point. Thus, it can be estimated that a transferred muscle, initially graded 4 or 5, may have an active effect on foot extension. Therefore, the contraction of the transferred muscle alone will be able to cause foot extension.

When the transferred tendon comes from a weak muscle, the transfer will not be active but will work by tenodesis effect. The tenodesis effect refers to the tensioning of the tendon; this tension will automatically lift the foot during walking.

The various conditions treated by the operation

Chronic ruptures of the anterior tibialis tendon can cause foot drop. The anterior tibialis muscle is a powerful foot lifter and a strong shock absorber when walking. It is a muscle that is particularly stressed in walkers. In cases of acute rupture of the posterior tibialis tendon, it can be repaired. Usually, these lesions initially go unnoticed and the diagnosis is made late, at the chronic stage. The tendon is therefore of poor quality, and the muscle is generally infiltrated with fat. Repair will, therefore, likely not result in active foot lifting or a tenodesis effect due to poor musculotendinous trophicity. In this case, it is possible to use the extensors of the second and third toes and transfer them to the insertion of the anterior tibialis tendon.

So-called central neurological feet may exhibit weakness of the foot lifters. These are feet concerning patients who have suffered brain or spinal cord injuries. Depending on the clinical presentation, the neurological condition involved, and the muscle grading of the various muscles in the leg and foot, it may be possible to transfer a hemi-tendon of the anterior tibialis, or even the posterior tibialis tendon. In some cases, the transfer of the peroneus longus tendon can be used.

In peripheral foot drop, by definition, the dorsiflexors are affected. The chosen transfer will depend on the grading of the remaining foot lifter muscles, if any remain. In general, it will be possible to use a transfer of the posterior tibialis tendon.

The benefits of foot lift surgery

The main advantage of performing palliative tendon transfers is to restore foot dorsiflexion through an automatic mechanism by tenodesis effect, or through an active mechanism using the muscle contraction of the transferred musculotendinous unit.

Precautions to take

Considering that these interventions on the dorsiflexors are in the vast majority of cases performed for neurologic feet, it is necessary to wait until the neurologic pathology is stabilized. Since neurological recovery can take a long time, patience is needed; the patient should be regularly re-examined to ensure that their neurological examination remains unchanged. The risk of performing a tendon transfer too early is that it may be done excessively.

It is also essential to properly assess the active muscles around the ankle prior to transfer. Ideally, an active muscle should be transferred into an area where all the extensors are nonfunctional. If a tendon transfer is performed while the foot dorsiflexor muscles are still active, there is a risk of abnormal contractions and disturbances of nerve and muscle control.

The tendon transfer must be incorporated into more extensive surgical programs if there are associated ankle or foot deformities. Indeed, the choice of transfer may also depend on the deformity to be corrected and the surgical methods used to correct it.

The steps of the operation

Repeated clinical examinations with muscle grading each time are probably the most important element before deciding on the intervention.

It will be necessary to take X-rays to assess bone architecture and bone deformities and/or joint laxity.

An electromyogram may be performed depending on the suspected or diagnosed neurological pathology in the preoperative phase.

The different techniques used by the specialists at the Clinique du Pied

We handle traumatic and chronic pathologies of the anterior tibialis and the tendons and muscles around the ankle and foot in general, as well as neurologic feet called peripheral and central.

We perform corrective interventions for deformities and tendon transfers for these pathologies.

Long-term results

The results are generally stable over time. It is difficult to give success or failure percentages because each case is very specific, the condition is different, the impairments are different, as well as the patients' expectations.

Taking all deformities into account is important to prevent deforming forces from evolving and leading to a recurrence of the problem.

In general, the foot drop issue is predominant, so tendon transfer will be a good solution in this case. Subsequently, other neurological symptoms may occur and require further procedures to continue rebalancing the ankle and foot.

Conclusion

Palliative surgical treatments may be offered to address a foot dorsiflexor deficit. These surgical treatments are proposed after functional treatment and physical medicine and rehabilitation therapy have failed to achieve patient satisfaction.

The management of neurological feet is ideally carried out in neuro-orthopedic centers. Unfortunately, these centers are rare, but they are recommended due to their comprehensive, specialized, and multidisciplinary care.