Foot Drop Treatment & Management

Updated: Aug 03, 2017
  • Author: James W Pritchett, MD; Chief Editor: Vinod K Panchbhavi, MD, FACS  more...
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Treatment

Approach Considerations

Foot drop is highly distressing, and attention to the patient’s psychological needs is very important. Pain should be managed. Optimizing glucose control in diabetic patients and managing vitamin deficiencies with supplements of vitamin B1, B6, or B12 can also be useful.

When foot drop is not amenable to surgical treatment, an ankle-foot orthosis (AFO) is often used. If the foot drop is due to hemiplegia, peroneal nerve stimulation can be considered. Foot drop due to direct trauma to the dorsiflexors generally calls for surgical repair. When nerve insult is the cause of foot drop, treatment is directed at restoring nerve continuity, either by direct repair or by removal of the insult.

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Pharmacologic Therapy

If painful paresthesias develop, they can sometimes be effectively managed with sympathetic blocks or laparoscopic synovectomy. Alternative treatments are amitriptyline, nortriptyline, duloxextine, pregabalin, and gabapentin. Local treatment with transdermal capsaicin or diclofenac can also reduce symptoms. Even if there is significant pain, narcotic medications should be kept to a minimum.

Erythropoietin is a naturally occurring hormone that is approved by the US Food and Drug Administration for the treatment of anemia but also has neuroprotective and, possibly, neurotrophic properties. The proposed mechanism of action is antiapoptotic and anti-inflammatory, promoting cell survival. Erythropoietin is given in three doses of 5000 U/kg over 1 week after nerve injury. It has a minimal side-effect profile. An animal study showed that erythropoietin treatment accelerated functional recovery after peripheral nerve injury. [11]

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Ankle-Foot Orthosis

An AFO may be used for foot drop when surgery is not warranted or during surgical or neurologic recovery. The specific purpose of an AFO is to provide toe dorsiflexion during the swing phase, medial or lateral stability at the ankle during stance, and, if necessary, pushoff stimulation during the late stance phase. An AFO is helpful only if the foot can achieve plantigrade position when the patient is standing. Any equinus contracture precludes its successful use.

The most commonly used AFO in foot drop is constructed of polypropylene and inserts into a shoe. If it is trimmed to fit anterior to the malleoli, it provides rigid immobilization. This device is used when ankle instability or spasticity is problematic, as is the case in patients with upper motor neuron diseases or stroke.

If the AFO fits posterior to the malleoli (posterior leaf spring type), plantarflexion at heel strike is allowed, and pushoff returns the foot to neutral for the swing phase. This provides dorsiflexion assistance in instances of flaccid or mild spastic equinovarus deformity. A shoe-clasp orthosis that attaches directly to the heel counter of the shoe also may be used.

A study by Menotti et al suggested that anterior AFOs are associated with lower energy costs of walking and higher levels of perceived comfort than posterior AFOs are and thus may allow people with foot drop to walk longer distances while expending less physical effort. [12]

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Nerve Stimulation

When foot drop is due to hemiplegia, peroneal nerve stimulation has potential advantages over an AFO, in that it provides active gait correction and can be tailored to individual patients. A short burst of electrical stimulation is applied to the common peroneal nerve between the popliteal fossa and the fibular head. This burst is controlled by a switch in the heel of the affected limb. The stimulator is activated when the foot is lifted and stopped when the foot contacts the ground. This achieves dorsiflexion and eversion during the swing phase of gait.

In a study by Ring et al, the effects of a radiofrequency-controlled neuroprosthesis were compared with those of a standard AFO in 15 patients with foot drop caused by stroke or traumatic brain injury. [13] Compared with the AFO, the neuroprosthesis yielded better balance control during walking and thus managed foot drop more effectively.

The nerve stimulator can be either external or implanted and radiofrequency-activated. In a study of stroke patients with spastic hemiplegia, Chae et al found electrical stimulation to be useful in approximately 2% of the cases. [14] This method may enhance gait speed and quality, and it can contribute to motor relearning.

In a study of 197 patients who had sustained a stroke approximately 3 months previously, Kluding et al compared use of an AFO with use of a foot-drop stimulator (FDS) for treatment of foot drop. [15] They concluded that whereas both approaches resulted in significant improvement in gait speed and functional outcomes, user satisfaction was higher with the FDS; they also stressed that initial therapy can provide long-term benefit.

Van Swigchem et al studied the potential benefits of peroneal functional electrical stimulation (FES) versus an AFO in regard to the patient’s ability to avoid an obstacle. [16] They concluded that FES was superior and that this finding was particularly relevant to people with low strength in the lower leg muscle.

Chou et al found that application of FES to the upper limbs as well was useful for abnormal arm swing in hemiplegic patients with foot drop. [17]

Bethoux et al carried out a 12-month follow-up analysis of a multicenter unblinded randomized controlled study that compared FES with AFOs over a period of 6 months. [18]  At 12 months, there were no statistically significant differences between the FES group and the AFO group with respect to either primary endpoints (10-Meter Walk Test and device-related serious adverse event rate) or secondary endpoints (6-Minute Walk Test, GaitRite Functional Ambulation Profile, and Modified Emory Functional Ambulation Profile).

Miller et al compared two different FES devices, the Odstock Dropped Foot Stimulator (ODFS) and the Walkaide (WA), in terms of their effect on energy cost and speed of walking. [19]  The ODFS yielded a significant increase in walking speed over what was achieved without FES, and the WA yielded a near-significant increase. Neither walking speed nor eenrgy cost differed significantly between the two FES systems.

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Options for Surgical Intervention

If foot drop is secondary to lumbar disc herniation (a finding in 1.2-4% of patients with foot drop), discectomy should be considered. In the early phase of this condition, decreased blood flow due to compression is thought to lead to nerve-root ischemia. The nerve root is more susceptible to compression injury than the peripheral nerve is because the vascular network of the nerve root is less developed, with no regional arteriolar blood supply. Foot drop due to nerve-root injury may depend on the magnitude and duration of nerve-root compression.

Early decompression is recommended in cases accompanied by severe motor disturbance, especially in older patients. [6] A Japanese study of 46 patients with degenerative lumbar disease who presented with drop foot noted that palsy duration and preoperative strength were the factors that most affected recovery after surgical intervention. [20]

Foot drop following hip replacement can also be treated with sciatic nerve decompression, particularly if there is any concern about bleeding at the operative site. Shortening of the hip prosthesis may be helpful if the limb was lengthened during surgery. [21]

A review of surgical management of peroneal nerve lesions demonstrated that neural repair is the first priority in selected patients with peroneal nerve palsy. [22] This may be accomplished by means of nerve decompression (either central or peripheral) or nerve grafting or repair. For foot drop from deep peroneal nerve injuries of less than 1 year’s duration, one study reported success in transferring functional fascicles to deep peroneal-innervated muscle groups, with either the superficial peroneal nerve or the tibial nerve used as a donor. [23]

If sufficient recovery is not achieved with those measures, tendon transfer procedures (see below) may be considered. It has been suggested that a tendon transfer may be considered if there is no significant neural recovery at 1 year. If a foot drop is chronic and accompanied by contracture, lengthening of the Achilles tendon may be necessary to achieve adequate dorsiflexion.

In patients in whom foot drop is due to neurologic and anatomic factors (eg, polio or Charcot joint), arthrodesis may be the preferred option. The goal is to achieve a stable, well-aligned foot and ankle. This may be accomplished by means of ankle arthrodesis, Lisfranc arthrodesis, and triple or pantalar arthrodesis, with or without lengthening of the Achilles tendon.

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Nerve Exploration, Decompression, and Repair

Decisions regarding the appropriate timing of nerve exploration and repair must take into consideration the mechanism of insult.

For sharp laceration with suspected nerve transection, early repair is warranted. Blunt lacerations are repaired 2-4 weeks after injury. Lesions in continuity usually are monitored for several months with clinical examination and electromyography (EMG) for signs of early regeneration. If spontaneous regeneration does not occur, surgical exploration and intraoperative nerve action potential (NAP) recordings are used to determine the need for repair, either with end-to-end sutures or with nerve grafts.

Patients with peroneal nerve palsy after knee arthroplasty or tibial osteotomy should initially be treated by removing all constrictive dressings and repositioning the knee to 20-30° of flexion. If an expanding hematoma is noted, urgent exploration is warranted. If functional recovery does not occur within 2 months, nerve exploration or release is advocated. The time interval between symptom onset and decompression appears to affect the final functional outcome. However, the severity of the preoperative palsy does not seem to affect recovery.

The recommended approach for nerve decompression is through a longitudinal posterolateral incision centered at the fibular head and paralleling the biceps tendon and fibula. The peroneal nerve is identified at the biceps femoris and traced distally. The nerve is released proximally from its fibrous enclosure at the fibular neck. Distally, it is released to the level where it dives into the peroneus longus. The attachment of the peroneus longus at the fibular neck is also released.

A wider exposure should be used for posttraumatic exploration if immediate repair or grafting is anticipated. With the patient prone, a mildly curved incision is made just medial to the short head of the biceps femoris in the lower thigh, extending to the skin posterior to the fibular head and then toward the anterior compartment. Superficial and deep peroneal nerve branches are exposed distal to the fibular head. The peroneal nerve is traced obliquely across the popliteal fossa, and its division can be split away from the tibial fossa if further length is needed.

In general, limited exposure should be avoided, so as to facilitate the performance of intraoperative stimulation and recording studies. Having clear exposure of the lesion, as well as viable nerve proximally and distally, is essential. Surgical exploration with NAP monitoring of lesions in continuity can document sufficient peroneal recovery to allow the surgeon to avoid unnecessary resection and repair. Allograft nerve conduits and allograft cable grafts are an alternative to autografts for nerve reconstruction.

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Tendon Transfer

With a tendon transfer, retraining of the transferred tendon and stretching exercises for the Achilles tendon are advocated. Retraining may be avoided with a neurotendinous transposition of the gastrocnemius and the proximal end of the deep peroneal nerve.

This procedure requires very specific patient selection in the subgroup with persistent traumatic peroneal nerve palsy. The common peroneal nerve lesion must be at or distal to the branching from the tibial nerve (to guarantee that intact motor fibers proximal to the lesion are available for transposition). Paralysis must be permanent.

Specifically, there must be no recovery of function for at least 18 months after injury or after the most recent attempt at exploration or repair. Electrodiagnostic changes indicative of permanent damage must be present. Also, there must be good passive range of motion, with at least 90° of dorsiflexion. The muscles innervated by the tibial nerve must be normal. Finally, soft-tissue coverage must be adequate.

A common method of tendon transfer moves the posterior tibial tendon (PTT), with or without complementary lengthening of the Achilles tendon. This procedure is accomplished via an open Z-lengthening of the Achilles tendon to allow a minimum of 15° of passive dorsiflexion.

The route by which the PTT is transferred may be either through the intraosseous membrane or circumtibial. One series that included patients with leprosy concluded that the circumtibial route had an unacceptably high rate of recurrent inversion, leading to ulceration of the lateral border of the foot. [24] Other series have found either method to be acceptable, but a 2009 study argued that the interosseous membrane route is preferred in this patient population. [25]

The circumtibial route is technically easier, but it may be less appealing cosmetically. The intraosseous membrane route can be prone to adhesions if the window in the membrane is too narrow. In addition to discouraging adhesions, a generous window produces a straight line of pull of the posterior tibial muscle-tendon unit from its origin to its new insertion on the dorsum of the foot.

Once a transfer route is selected, the point of fixation of the split PTT may be either tendon-to-tendon or tendon-to-bone. In tendon-to-tendon fixation, the points of attachment are as follows:

  • Lateral slip - Peroneus brevis, peroneus tertius, or extensor digitorum longus (EDL) tendons
  • Medial slip - Tibialis anterior or extensor hallucis longus (EHL)

In tendon-to-bone fixation, an osseous tunnel in the tarsal or metatarsal bones serves as the point of attachment. One study cited a report of a consequent neuropathic arthropathy of the tarsal joints.

A popular approach to tendon-to-bone attachment is the Bridle procedure, a modification of the Riordan technique described by Rodriguez. [26] This procedure involves insertion of the PTT into the second cuneiform bone, combined with anastomosis of the PTT transfer to the anterior tibial tendon (ATT) and a rerouted peroneus longus tendon in front of the lateral malleolus to balance the foot in dorsiflexion.

The Bridle procedure makes use of five incisions (see the first image below). The PTT insertion is secured through incision 1 on the medial foot. Incision 2 is used to retrieve the end of the PTT proximal to the tarsal canal into the posterior compartment of the leg (see the second image below).

Incisions for Bridle procedure. Incisions for Bridle procedure.
Posterior leg with retrieved posterior tibial tend Posterior leg with retrieved posterior tibial tendon above ankle. Window in interosseous membrane is labeled with X.

Incision 3, on the anterior leg proximal to the ankle, provides wide exposure of the interosseous membrane. The PTT is pulled through the interosseous membrane and a longitudinally split ATT, then into the anterior compartment between the tibia and the ATT. The PTT is anastomosed to the ATT with the foot in full dorsiflexion (see the image below).

Posterior tibial tendon (C) is pulled through slit Posterior tibial tendon (C) is pulled through slit in anterior tibial tendon (A) and inserted into second cuneiform. Posterior tibial tendon is anastomosed to anterior tibial tendon and distal stump of peroneus longus (B) that has been rerouted anterior to lateral malleolus.

Incision 4, posterior to the lateral malleolus, accesses the peroneus longus and brevis tendons proximal to the lateral retinaculum. The peroneus longus is transected about 5 cm proximal to the tip of the lateral malleolus. The distal transected end of the peroneus longus is retrieved into the foot distal to the superior and inferior peroneal retinaculum, then transposed via a direct subcutaneous tunnel that is anterior to the lateral malleolus. The proximal end of the transected peroneus longus is anastomosed to the peroneus brevis tendon.

Incision 5 accesses the distal stump of the PTT as it is brought to the dorsum of the foot via a subcutaneous tunnel. Here, the tendon is secured to the second cuneiform bone while full dorsiflexion of the foot is maintained. Ideally, if the tendon has sufficient length, it should be anastomosed to itself through a tunnel in the second cuneiform bone. If this is not feasible, the tendon may be secured to the bone with sutures or tunneled through and secured with a button.

In a study comparing 19 patients with foot drop who underwent the Bridle procedure with 10 matched control subjects, Johnson et al found that although the procedure did not restore foot and ankle strength and balance to normal, it was successful in that patients with a functional posterior tibial muscle had significantly better outcomes and were able to discontinue using an AFO. [27] All of the Bridle-procedure patients had good-to-excellent outcomes and stated that they would undergo the operation again.

Werner et al, in a study of 10 patients with peroneal nerve injury resulting from multiligament instability, evaluated nonoperative treatment (n=5) against PTT transfer (n=5); there was also a control group (n=4) who did not have peroneal nerve injury. [28] Compared with the nonoperative group, the PTT-transfer group showed increased dorsiflexion at initial contact and at mid-late swing phase. Compared with the control group, the PTT-transfer group had similar gait patterns but tended to be more everted. Overall, gait analysis demonstrated significantly improved sagittal-plane ankle kinematics with PTT transfer, with some degree of subtle instability as the tradeoff.

A series of hemiplegic patients demonstrated favorable results when anterior transfer of the long-toe flexors (flexor hallucis longus [FHL] or flexor digitorum longus [FDL]) was combined with Achilles-tendon lengthening. The flexor was transferred intraosseously to the fourth metatarsal. If the foot drop was accompanied by a marked varus deformity, lengthening of the PTT was also performed. Short-toe flexors were released if the patient had severe hammertoes.

Another method of reconstruction involving the coaptation of the EHL to the tibialis anterior was investigated in eight patients who had had polio. At final review, only two of the patients maintained efficient dorsiflexion. These poor results were thought to be due to stretching of the coaptation.

During neurotendinous transposition, the lateral head of the gastrocnemius is transposed to the tendons of the anterior muscle group simultaneously with transposition of the proximal end of the deep peroneal nerve. The nerve is sutured to the motor nerve of the lateral head of the gastrocnemius, restoring active voluntary foot dorsiflexion and automatic walking. By avoiding use of an antagonist muscle to the paralytic group of muscles, this transfer avoids retraining to achieve dorsiflexion, providing physiologic muscle balance and fully automatic walking.

Mohavedi Yeganeh et al described the use of a triple tendon transfer (involving the PTT, the FHL tendon, and the FDL tendon) to correct toe drop associated with common peroneal nerve palsy, which is not addressed by anterior PTT transfer alone. [29]  Excellent postoperative results for foot drop correction were achieved in nine cases (60%), good results in five (33%), and moderate results in one (7%). Excellent postoperative extension of the toes was achieved in seven cases (47%), good extension in five (33%), and moderate extension in three (20%).

Cho et al reported on 17 patients who underwent PTT transfer for foot drop secondary to peroneal nerve palsy (follow-up, ≥3 years). [30] Mean American Orthopaedic Foot & Ankle Society (AOFAS) score, Foot and Ankle Outcome Score (FAOS), and Foot and Ankle Ability Measure (FAAM) improved significantly at final follow-up: from 65.1 to 86.2, from 55.6 to 87.8, and from 45.7 to 84.4, respectively. However, all functional evaluation scores were significantly lower than in the control group. Mean peak torque was 7.1 Nm for ankle dorsiflexors, 39.2 Nm for plantarflexors, 9.8 Nm for invertors, and 7.3 Nm for evertors at final follow-up. These values were significantly lower than corresponding values in the control group.

No significant differences in radiographic measurements were found, and no patients presented with a postoperative flatfoot deformity. [30] One patient (5.9%) needed an AFO for occupational activity. Cho et al concluded that although restoration of dorsiflexion strength postoperatively was about 33% of the normal ankle, function in daily activities and gait ability were satisfactorily improved. In addition, PTT transfer demonstrated no definitive radiographic or clinical progression to postoperative flatfoot deformity at intermediate-term follow-up.

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Long-Term Monitoring

After a nerve exploration or graft procedure, weight-bearing as tolerated is allowed with a 2- to 3-day period of immobilization of the knee in a Robert-Jones dressing (a bulky compressive bandage composed of multiple layers of soft material). An AFO may be used while neural recovery is being awaited.

After a tendon transfer procedure, the patient is placed in a cast and restricted to nonweightbearing ambulation for 6 weeks. Subsequently, the patient receives physical therapy for gait training.

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