DEFINITION

Pathology leading to a spectrum of motor function loss that includes loss of ankle dorsiflexion Common peroneal nerve palsy, L5 radiculopathy, cerebrovascular accident

Loss of ankle dorsiflexion and hindfoot eversion Retained posterior tibial tendon (PTT) function

Hereditary sensory motor neuropathy

A constellation of motor function deficits and associated deformity Includes loss of dorsiflexion and hindfoot eversion

Retained PTT function Flaccid paralysis

Global loss of motor function to the ankle and foot

 

 

ANATOMY

 

Posterior tibialis

 

 

Muscle originates on the posterior tibia, interosseous membrane (IOM), and fibula. Muscle and then tendon course in the deep posterior compartment.

 

Tendon travels directly posterior to the medial malleolus.

 

Tendon has numerous insertions on bones of plantar midfoot, spring ligament, and medial aspect of navicular.

 

IOM and distal tibia-fibula syndesmosis

 

Thick fibrous bands between tibia and fibula

 

Distal tibia-fibula syndesmosis is narrow, with little space for tendon transfer even when a generous window is created in the distal IOM.

 

Inferior extensor retinaculum

 

On the dorsum of the foot to prevent bowstringing of the extensor tendons as they transition across the anterior ankle to the dorsal foot

 

Sciatic nerve

 

 

Comprises tibial and common peroneal nerves that separate immediately proximal to the popliteal fossa Common peroneal nerve often affected in these neuropathies

 

Superficial peroneal nerve

 

Motor function to anterior and lateral compartment muscles

 

 

Dorsiflexion and eversion, respectively Sensory distribution to dorsum of the foot

 

Deep peroneal nerve

 

 

Courses between tibialis anterior and extensor hallucis longus tendons proximal to the ankle Located directly on the dorsum of midfoot

 

 

Immediately deep to extensor hallucis brevis muscle belly Motor function to intrinsic muscles of foot

 

Sensory distribution to first web space

 

 

Tibial nerve function typically spared

 

 

Tibial nerve must be intact to create a dynamic tendon transfer. If tibial nerve is not intact, then transfer can only be a tenodesis.

 

 

 

Anterior ankle and dorsal midfoot neurovascular structures at risk Superficial peroneal nerve (may be insensate as part of the neuropathy) Deep neurovascular bundle

 

Anterior tibial artery

 

 

Deep peroneal nerve (may also be insensate as part of the neuropathy) Peroneal artery branch

 

Situated directly on anterior distal IOM

 

PATHOGENESIS

 

Loss of common peroneal nerve function

 

 

Loss of ankle dorsiflexion and hindfoot eversion Loss of major antagonists

 

Eventual equinus contracture

 

Imbalance of hindfoot inverter (PTT) and everters (peroneus brevis and usually, but not always, peroneus longus)

 

Eventual hindfoot varus deformity

 

Imbalance of hindfoot inverters (PTT) and everter (peroneus longus)

 

 

Flaccid paralysis

 

 

Tibial and common peroneal nerve palsies No motor function distal to knee

 

Because both sets of major antagonists lost, typically no contractures

 

NATURAL HISTORY

 

Foot drop may eventually recover.

 

Tendon transfers should not be considered until a chance for recovery has been ruled out.

 

Common peroneal nerve palsy may lead to progressively worsening equinocavovarus foot deformity due to overpull of plantarflexors and inverters powered by intact tibial nerve and loss of dorsiflexors and everters powered by compromised common peroneal nerve.

 

Flaccid paralysis remains relatively stable because both sets of antagonists are compromised.

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

 

Gait abnormality “Slap foot gait”

 

Inability to dorsiflex ankle and control tibialis anterior from heel strike to stance phase

 

 

81

 

Exaggerated hip and knee flexion

 

 

Inability to dorsiflex ankle or great toe from push-off through swing phase Compensation to allow toes to clear during swing phase

 

Hindfoot inversion

 

Patient walks on lateral border of foot.

 

 

Inability to dorsiflex ankle

 

May check by asking patient to walk on heels

 

 

Manual muscle testing with patient seated on examining table with knee flexed Lack of eversion

 

Varus hindfoot

 

Over time, may become a fixed inversion contracture

 

In some disease processes (eg, Charcot-Marie-Tooth disease), toe dorsiflexion is spared, creating claw toe deformities.

 

Patient attempts to compensate for lack of ankle dorsiflexion with toe extensors, worsening claw toe deformities.

 

Even when toe extensors are involved in the palsy, flexor tendons may become contracted.

 

Passive dorsiflexion of the ankle will reveal this.

 

 

With equinocavovarus foot contracture, calluses may form under metatarsal heads, particularly the fifth. Sensation may be diminished on the dorsal and lateral aspects of the foot.

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

 

Imaging is typically unnecessary for patients with foot drop except in the following situations: Consideration should be given to MRI:

 

If there is concern for mass effect creating a compressive neuropathy: lumbar spine, common peroneal nerve at fibular head

 

To rule out tibialis anterior tendon rupture (should be evident on clinical examination alone)

 

 

Consideration should be given to radiographs of foot or ankle: To rule out stress fracture

 

To better define bony deformity (fixed deformity, associated ankle or foot arthritis; important because arthrodesis

 

may need to be considered in lieu of or in combination with tendon transfer) Electrodiagnostic studies

 

Absence of recovery at 1 year and particularly at 18 months is highly suggestive that recovery of nerve function will not occur.

 

Nerve conduction studies and electromyography

 

 

Baseline and follow-up studies to determine if any recovery is evident Important to determine if tendon transfer is warranted

 

Tendon transfer should not be performed if nerve function may recover

 

Absence of recovery at 1 year and particularly at 18 months is highly suggestive of no recovery.

 

 

We recommend consultation with a neurologist to confirm interpretation of electrodiagnostic studies. Studies may also define function of PTT.

 

Important when considering dynamic PTT transfer versus PTT tenodesis

 

A tendon transfer of a healthy tendon immediately reduces its strength on manual muscle testing from 5/5 to 4/5, so if it is already compromised, then the tendon transfer will do little more than create a tenodesis.

 

Useful in determining if a more proximal compressive neuropathy exists

DIFFERENTIAL DIAGNOSIS

Tibialis anterior tendon rupture Cerebrovascular accident Lumbar spine radiculopathy

Hereditary sensorimotor neuropathy Leprosy

Poliomyelitis

Cerebral palsy (spastic)

 

 

NONOPERATIVE MANAGEMENT

 

 

Bracing with an ankle-foot orthosis (AFO) Requires a fixed AFO in flaccid paralysis

 

May be a flexible AFO with common peroneal palsy

 

Requires plantarflexion stop

 

Equinus contracture may need to be corrected to facilitate brace wear.

 

 

Achilles stretching Botulinum toxin injection

 

 

Tendo Achilles lengthening (TAL) Varus deformity

 

 

If flexible may be corrected with bracing If fixed, bracing is difficult.

SURGICAL MANAGEMENT

Preoperative Planning

 

The surgeon must confirm that motor function will not recover before proceeding with tendon transfer.

 

Serial clinical examination

 

 

Serial electrodiagnostic studies (at least one compared to baseline) The surgeon must determine what motor function persists:

 

Tibial nerve

 

PTT (inversion)

 

 

Gastrocnemius-soleus (plantarflexion) None (flaccid paralysis)

 

The surgeon must evaluate for equinus contracture.

 

The surgeon should be prepared to perform TAL if necessary (see TECH FIG 1A-D).

 

Flexible versus fixed deformities

 

 

Flexible deformity typically corrects with tendon transfer alone. Fixed deformity

 

May require capsular release or even arthrodesis

 

 

Toe contractures

 

Although claw toe deformity may not be evident with the ankle plantarflexed, once the deformity is corrected, toe contractures may become obvious.

 

Dorsiflexing the ankle will put the contracted flexor hallucis and digitorum on stretch, thereby revealing the toe contractures.

 

The surgeon should be prepared to address toe contractures as part of the procedure.

 

 

Tendon transfer anchoring

 

 

 

We routinely use interference screws to anchor tendon transfers to bone. Need to have an anchoring system available

 

 

Alternatively, anchoring to existing distal tendon or existing soft tissues in the foot may be possible.

 

82

 

 

In our experience, anesthesia should maintain complete muscle relaxation and paralysis during the procedure; otherwise, the success of the tendon transfer may be compromised.

 

At the conclusion of the procedure, we often perform botulinum toxin injections into the gastrocnemius-soleus

complex to further protect the tendon transfer postoperatively.

 

Positioning

 

Supine

 

If the PTT will be transferred through the IOM or if a peroneal tendon will be used for correction of flaccid paralysis, we routinely place a bolster under the ipsilateral hip to afford optimal lateral exposure. Once the lateral tendon is harvested or the PTT transferred through the IOM, the bolster may be removed.

 

We routinely use a thigh tourniquet.

 

Approach

 

Multiple relatively small incisions are needed; extensile exposures are unnecessary.

 

PTT harvest

 

Medial harvest over navicular

 

 

Posteromedial tibia at musculotendinous junction of PTT PTT transfer through the IOM

 

 

Incision over distal IOM Incision over dorsolateral foot

 

 

PTT transfer anterior to tibia Incision over central midfoot

 

 

Bridle procedure Same PTT harvest

 

PTT transfer through IOM with incision directly anterior over distal tibia; may be extended to dorsal foot.

Alternatively, separate small incision over centrodorsal midfoot.

 

Lateral incisions: incision over musculotendinous junction of peroneus longus and another incision over lateral cuboid where peroneus longus courses around cuboid

 

TECHNIQUES

• Achilles Lengthening

Indications

Not always necessary but typically required when foot drop occurs

Without active dorsiflexion, the gastrocnemiussoleus' antagonist is lost, often leading to an Achilles contracture.

Occasionally, patients maintain an active stretching program, thereby avoiding an Achilles contracture.

Weakening of the gastrocnemius-soleus complex may be beneficial because a transfer of a healthy muscle-tendon unit is subject to an automatic one-grade loss of power (5/5 manual muscle testing drops to 4/5 with transfer).

Occasionally, we use botulinum toxin in the gastrocnemius-soleus complex when performing a PTT transfer for foot drop.

 

 

 

 

TECH FIG 1 • TAL. A. Equinus with knee in flexion and extension suggests tight gastrocnemius and soleus.

B. Initial Achilles hemisection. (continued)

 

 

Technique

 

Determined by the Silfverskiöld test

 

Equinus contracture with the knee in extension and flexion (TECH FIG 1A)

 

Triple hemisection (Hoke procedure) because both the gastrocnemius and soleus are contracted (TECH FIG 1B-D)

 

Equinus contracture only with the knee in extension: gastrocnemius-soleus recession (Strayer procedure) because only the gastrocnemius is contracted

Posterior Tibial Tendon Transfer through the Interosseous Membrane

 

Advantages

 

PTT in direct line from its muscle through the IOM to the lateral cuneiform (our preferred site for tendon anchoring)

 

Anchor point slightly lateral of midline to promote dorsiflexion and eversion

 

 

83

 

 

 

TECH FIG 1 • (continued) C. Second Achilles hemisection (opposite direction from first), to be followed by third and final hemisection in same direction as first. D. Dorsiflexion reestablished after Achilles lengthening.

 

 

Disadvantage

 

PTT may be constricted and stenosed within narrow window created in distal IOM.

Posterior Tibial Tendon Harvest

 

Make a 4-cm longitudinal incision over the medial navicular and PTT on the medial foot.

 

 

 

TECH FIG 2 • PTT harvest. A. Elevating PTT with a sliver of medial navicular may allow longer tendon harvest. B. Isolating PTT. C. Distal PTT needs to be trimmed to allow it to pass into dorsal foot osseous tunnel. D,E. Tag suture in distal PTT. (continued)

 

 

 

Open the PTT sheath to expose the tendon. Release the PTT insertion on the medial navicular.

 

Alternatively, use a chisel to elevate some medial navicular bone with the PTT release from the medial navicular (may allow for another centimeter of tendon for transfer) (TECH FIG 2A).

 

Isolate the PTT attachment on the medial navicular and the tendon fibers that begin to course to the plantar midfoot (TECH FIG 2B).

 

84

 

 

 

TECH FIG 2 • (continued) F. Transfer of PTT to proximal medial wound. A 3-cm incision is made over PTT musculotendinous junction. G. Tendon transfer is mobilized. H. PTT is transferred to proximal wound.

 

 

With the PTT fibers isolated, transect them to release the PTT distally.

 

Be sure to fully isolate the PTT fibers; the medial plantar nerve and the plantar medial complex of veins is in close proximity.

 

Accidentally transecting the nerve leads to loss of sensation in the plantar medial forefoot.

 

Violating the veins may make it difficult to achieve satisfactory hemostasis, as these veins may then retract under the foot.

 

Thin the distal stump of the PTT to be transferred to facilitate its transfer into an osseous tunnel that will be created in the foot (TECH FIG 2C).

 

Place tag sutures in the distal PTT (TECH FIG 2D,E).

 

Make a more proximal medial incision at the PTT musculotendinous junction on the posterior tibia.

 

A 3-cm incision (TECH FIG 2F)

 

Flexor digitorum tendon is usually encountered first.

 

 

Deep to the flexor digitorum longus, directly on the posteromedial tibia, the PTT is identified. Place a blunt retractor around the PTT through this more proximal wound to isolate it.

 

Mobilize the distal PTT.

 

Alternate tension on the proximal tendon through the proximal wound and the distal tag sutures (TECH FIG 2G), then apply tension proximally only.

 

This may not work.

 

The medial incision may need to be extended proximally to allow access to the posterior medial malleolus, a common location where the tendon may bind.

 

Once mobilized, the distal aspect of the PTT may be transferred to the proximal wound (TECH FIG 2H).

 

Tendon will desiccate rapidly, so we keep it tucked in the proximal medial wound.

Posterior Tibial Tendon Transfer through the Interosseous Membrane

 

 

Lateral incision on anterior aspect of distal fibula, at distal tibiofibular syndesmosis Careful exposure of anterior IOM

 

Elevate the anterior compartment soft tissues.

 

 

A branch of the peroneal artery courses on the anterior IOM and is at risk. Create a generous window in the distal IOM (TECH FIG 3A).

 

 

From tibia to fibula About 3 to 4 cm long

 

Pass a tonsil clamp through the IOM directly on the posterior aspect of the tibia to exit in the proximal medial wound (TECH FIG 3B).

 

The posterior neurovascular structures (tibial nerve and posterior tibial artery) are at risk, so be sure the clamp is directly on the posterior tibia.

 

Use the tonsil clamp to grasp the tag sutures of the PTT (TECH FIG 3C).

 

Pull the tag sutures and PTT from the medial wound to the lateral wound, keeping the tendon directly on the posterior aspect of the tibia (TECH FIG 3D,E).

 

Be sure that the window in the IOM does not impinge on the transferred tendon.

 

If there is stenosis, then further enlarge the window so that the tendon easily glides between the tibia and fibula.

 

Keep the tendon end in the wound to limit desiccation.

Preparation of the Dorsal Foot Anchor Site

 

Fluoroscopically identify the center of the lateral cuneiform.

 

 

 

Oblique foot views usually best define the lateral cuneiform (TECH FIG 4A). Center a 3- to 4-cm longitudinal skin incision directly over the lateral cuneiform.

85

 

 

 

TECH FIG 3 • PTT transfer through the IOM. A. A window is carefully created in the IOM (perspective with view of lateral distal leg [foot to the left and knee to the right]). B. A blunt clamp is passed through IOM, directly on posterior tibia. C. PTT tag sutures are grasped. D. PTT is transferred to anterolateral wound, with

tendon immediately on posterior tibia. E. The surgeon must be sure tendon does not bind in IOM window.

 

 

Dissect to the lateral cuneiform.

 

 

Protect the superficial peroneal nerve and extensor tendons. Deep neurovascular bundle is usually medial to this approach.

 

Expose and define the cuneiform.

 

We routinely use small-gauge hypodermic needles or Kirschner wires to mark the joints surrounding the lateral cuneiform and fluoroscopically confirm that the lateral cuneiform is defined by these markers (TECH FIG 4B).

 

Periosteum and capsular tissue are left intact.

 

 

 

TECH FIG 4 • Preparing dorsal foot osseous tunnel. A. Lateral cuneiform is identified fluoroscopically. B. Borders of lateral cuneiform are exposed and marked. C. Drill hole is created in lateral cuneiform and proper position is confirmed fluoroscopically. D. Osseous tunnel is gradually enlarged, first with drill bits, then dedicated reamer system for interference screw. E. Prepared osseous tunnel in lateral cuneiform.

 

 

Create an osseous tunnel in the center of the lateral cuneiform.

 

We routinely predrill the center with a Kirschner wire and confirm the starting point and trajectory of the wire fluoroscopically.

 

Remove the wire and introduce sequentially larger drill bits to enlarge the tunnel (TECH FIG 4C).

 

We use drill bits to a diameter of 4.5 mm.

 

With fluoroscopic confirmation, slight adjustments may be made with each successive drill bit to center the tunnel optimally in the cuneiform.

 

86

 

Introduce the reamer system for the interference screw system to enlarge the tunnel to the desired diameter (TECH FIG 4D).

 

Typically, we enlarge the tunnel to 6.5 to 7.0 mm in the lateral cuneiform (TECH FIG 4E).

Posterior Tibial Tendon Transfer to Dorsum of Foot

 

Transferring the PTT deep to the extensor retinaculum with the extensor tendons diminishes the power of the transfer (which is by definition already weakened by one grade with transfer).

 

Create a subcutaneous soft tissue tunnel from the dorsal foot incision to the more proximal and lateral lower

leg incision using a curved Kelly or tonsil clamp (TECH FIG 5A).

 

Use the clamp to grasp the tag sutures and pull the tendon through the subcutaneous tunnel to the dorsal foot incision (TECH FIG 5B).

 

 

 

TECH FIG 5 • PTT transfer from lateral lower leg wound to dorsum of foot. A. Subcutaneous tunnel created with a blunt clamp. B. Grasping tag sutures. C. Passing Beath drill with tag sutures through osseous tunnel.

D. Pulling Beath drill through plantar foot. E. The surgeon must be sure the tendon fits appropriately into the osseous tunnel. F. Tendon tensioning. Tendon advances appropriately into osseous tunnel (note, ankle is held in dorsiflexion). (continued)

 

 

Before anchoring the tendon in the osseous tunnel, pull the tendon via the tag sutures into the tunnel to be sure that the tunnel diameter is appropriate.

 

Pass a Beath pin or drill bit (has an eye to place suture) through the tunnel and the plantar skin (TECH FIG 5C).

 

Because of the midfoot arch and the drill hole centered in the lateral cuneiform foot, this pin or the drill bit will exit in the medial arch (TECH FIG 5D).

 

Dorsiflex the ankle.

 

With the tag sutures secured, pull the pin or drill bit through the plantar skin, thereby pulling the distal tendon end into the tunnel (TECH FIG 5E).

 

If the tunnel does not accommodate the tendon, then the tendon and tag sutures must be withdrawn and the tunnel enlarged.

 

Because of the angle at which the tendon enters the tunnel, we often need to guide the tendon into the tunnel with a forceps.

 

Anchoring the tendon to bone

 

Some degree of stretching or accommodation is anticipated, so we routinely anchor the tendon with the ankle maintained in 10 degrees of dorsiflexion and pull firmly on the plantar suture (TECH FIG 5F,G).

 

87

 

 

 

TECH FIG 5 • (continued) G. Tension applied on plantar tag sutures. H. Augmenting anchoring. Suture anchor being placed within osseous tunnel. I. Two anchors secured in tunnel (note separate tag suture of PTT). J. Final fixation of tendon transfer in dorsal foot. Tendon fully tensioned with ankle dorsiflexed. K,L. Securing tendon to anchors and adjacent periosteum. M. Interference screw positioned. N. Screw advanced. O. Screw fully seated.

 

 

A properly sized isolated interference screw is probably adequate.

 

However, we typically augment the anchor point with several nonabsorbable sutures from the periosteum surrounding the tunnel to the tendon directly at the entrance to the tunnel.

 

To further augment the anchor point, before advancing the tendon and tag suture into the tunnel, place one or two suture anchors within the tunnel (TECH FIG 5H,I). Then, advance the tendon into the tunnel and secure the tendon with the anchors (TECH FIG 5J,K). By tightening these sutures, the tendon may be pulled even further into the tunnel (TECH FIG 5L). An interference screw and periosteal sutures may still be used (TECH FIG 5M-O).

 

 

Have the assistant maintain full ankle dorsiflexion and tension on the tag sutures on the plantar foot. We usually cut the tag sutures so they retract beneath the skin.

 

Rarely, we have used a well-padded button on the plantar foot to further augment the tendon's anchor point. We do not routinely do so because of the risk for plantar skin necrosis from the button despite adequate padding.

 

In select patients, the dorsiflexed ankle will unmask claw toes due to flexor hallucis longus and flexor digitorum longus contractures. Consider flexor hallucis longus and flexor digitorum longus lengthenings, posterior to the ankle and tibia via the more proximal medial approach, or percutaneous tenotomies at the plantar toes.

 

 

88

• Posterior Tibial Tendon Transfer Anterior to the Tibia

 

Advantages

 

 

PTT has no opportunity to stenose in the IOM. Glides smoothly around anteromedial tibia

 

 

Anchor point slightly lateral of midline to promote dorsiflexion and eversion Disadvantage

 

 

PTT is not in direct line from its origin to anchor point in the foot; it must travel around medial tibia. Anchor point is in the middle (second) cuneiform.

 

Central location so it cannot provide an eversion moment

 

However, typically unimportant because with PTT transfer, the agonist-antagonist balance between PTT and peroneus brevis is again reestablished by being neutralized.

Achilles Lengthening

 

Same as for PTT transfer through IOM described earlier (TECH FIG 6) Posterior Tibial Tendon Harvest

 

Same as for PTT transfer through IOM described earlier (TECH FIG 7) Preparation of the Dorsal Foot Anchor Site

 

Similar to preparation of dorsal foot anchor site described earlier for PTT transfer through IOM

 

However, when transferring the PTT through the IOM, we typically anchor the tendon to the lateral (third) cuneiform.

 

 

 

TECH FIG 6 • Adequate dorsiflexion (essential for successful tendon transfer to reestablish dorsiflexion).

 

 

 

TECH FIG 7 • Approach to PTT harvest. A. The two planned medial incisions. B. Planned dorsal foot incision. C-E. Harvesting PTT. C. PTT is isolated. D. Distal tendon is trimmed (contoured). (continued )

 

In contrast, when we transfer the PTT anterior to the medial tibia, we typically anchor the tendon in the middle (second) cuneiform.

 

Middle cuneiform is smaller than the lateral cuneiform.

 

 

In our experience, greater risk of fracture with drill hole, tendon transfer, and interference screw Fluoroscopically identify the center of the middle cuneiform.

 

Anteroposterior (AP) and sometimes oblique foot views best define the middle cuneiform.

 

 

Center a 3- to 4-cm longitudinal skin incision directly over the middle cuneiform. Dissect to the middle cuneiform.

 

Protect the superficial peroneal nerve and extensor tendons (TECH FIG 8A).

 

89

 

 

 

TECH FIG 7 • (continued) E. Tag suture in distal end of tendon. PTT is mobilized. F. PTT is identified at its musculotendinous junction. G. PTT is mobilized to allow transfer to proximal wound. H,I. Transferring PTT to proximal medial wound. H. Tendon is pulled into proximal wound. I. Proposed course for transfer to dorsum of foot.

 

 

Protect the deep neurovascular bundle, usually encountered in this approach; it is directly deep to the

muscle of the extensor hallucis brevis.

 

Expose and define the cuneiform.

 

We routinely use small-gauge hypodermic needles or Kirschner wires to mark the joints surrounding the medial cuneiform and fluoroscopically confirm that the medial cuneiform is defined by these markers (TECH FIG 8B).

 

 

 

TECH FIG 8 • Preparation of dorsal foot osseous tunnel. A. Dorsal incision over middle cuneiform. B.

Middle cuneiform is identified and marked. (continued)

 

 

Leave the periosteum and capsular tissue intact.

 

Create an osseous tunnel in the center of the medial cuneiform.

 

We routinely predrill the center with a Kirschner wire and confirm the starting point and trajectory of the wire fluoroscopically.

 

90

 

 

 

 

TECH FIG 8 • (continued) C. Increasingly larger diameter drill bits. D. Increasingly larger reamers (judiciously because the middle cuneiform is not particularly large).

 

 

Remove the wire and introduce sequentially larger drill bits to enlarge the tunnel (TECH FIG 8C).

 

We use drill bits to a diameter of 4.5 mm.

 

With fluoroscopic confirmation, slight adjustments may be made with each successive drill bit to center the tunnel optimally in the cuneiform.

 

Use the reamer from the interference screw system to enlarge the tunnel to the desired diameter (TECH FIG 8D).

 

Typically, we enlarge the tunnel from 5.5 to 6.0 mm in the medial cuneiform.

Posterior Tibial Tendon Transfer to Dorsum of Foot

 

Transferring the PTT deep to the extensor retinaculum with the extensor tendons diminishes the power of the transfer (which is by definition already weakened by one grade with transfer).

 

Create a subcutaneous soft tissue tunnel from the dorsal foot incision to the more proximal and medial lower leg incision using a curved Kelly or tonsil clamp (TECH FIG 9A,B).

 

Use the clamp to grasp the tag sutures and pull the tendon through the subcutaneous tunnel to the dorsal foot incision.

 

Before anchoring the tendon in the osseous tunnel, pull the tendon via the tag sutures into the tunnel to be sure that the tunnel diameter is appropriate.

 

Pass a Beath pin or drill bit (has an eye to place suture) through the tunnel and the plantar skin (TECH FIG 9C,D). Because of the midfoot arch, this pin or drill bit will exit in the medial arch (TECH FIG 9E).

 

Dorsiflex the ankle.

 

With the tag sutures secured, pull the pin or drill bit through the plantar skin, thereby pulling the distal tendon end into the tunnel (TECH FIG 9F).

 

If the tunnel does not accommodate the tendon, then the tendon and tag sutures must be withdrawn and the tunnel enlarged.

 

Because of the angle at which the tendon enters the tunnel, we often need to guide the tendon into the tunnel with a forceps.

 

Anchoring the tendon to bone

 

Some degree of stretching or accommodation is anticipated in the posterior tibial muscle and tendon, so we routinely anchor the tendon with the ankle maintained in 10 degrees of dorsiflexion.

 

A properly sized isolated interference screw is probably adequate.

 

However, we typically augment the anchor point with several nonabsorbable sutures from the periosteum surrounding the tunnel to the tendon directly at the entrance to the tunnel.

 

To further augment the anchor point

 

Before advancing the tendon and tag suture into the tunnel, place one or two suture anchors within the tunnel (TECH FIG 9G).

 

Then, advance the tendon into the tunnel and secure the tendon with the anchors. By tightening these sutures, the tendon may be pulled even further into the tunnel. An interference screw and periosteal sutures may still be used (TECH FIG 9H).

 

 

Have the assistant maintain full ankle dorsiflexion and tension on the tag sutures on the plantar foot. We usually cut the tag sutures so they retract beneath the skin.

 

Rarely, we have used a well-padded button on the plantar foot to further augment the tendon's anchor point (TECH FIG 9I). We do not routinely do so because of the risk for plantar skin necrosis from the button despite adequate padding.

 

 

 

TECH FIG 9 • Transfer of PTT to dorsum of foot. A. Subcutaneous tunnel for blunt clamp to grasp tag suture in PTT. (continued)

 

 

91

 

 

 

TECH FIG 9 • (continued) B. PTT is transferred subcutaneously to dorsum of foot. C-F. Ensuring that PTT will pass through osseous tunnel in middle cuneiform. C. Beath drill through tunnel with tag suture from PTT secured. D. Entry point of Beath drill in dorsal tunnel. E. Exit of Beath drill in plantar foot. F. Tendon advancing appropriately with ankle in dorsiflexion and tension on tag sutures passed through plantar foot. G,H. Tendon fixation. G. Augmentation possible with suture anchors placed directly in tunnel before advancing tendon into tunnel. H. Interference screw with ankle dorsiflexed and tension maintained on plantar tag suture. I. Suture button. In this case, middle cuneiform fractured with insertion of interference screw and therefore a suture button was used. Note also the use of two Kirschner wires in the medial foot to further stabilize fracture in cuneiform.

 

 

92

• Bridle Procedure

 

Advantages

 

The “bridle” creates a balance to the foot and ankle.

 

 

Potentially can make the patient with flaccid paralysis brace-free Disadvantage

 

With flaccid paralysis, the tendon transfer is static, not dynamic.

 

Functions as a tenodesis

 

If procedure is successful, foot and ankle remain in neutral position at all times.

Achilles Lengthening

 

Same as for PTT transfer through IOM described earlier

Posterior Tibial Tendon Harvest

 

Same as for PTT transfer through IOM described earlier (TECH FIG 10) Harvest of the Peroneus Longus

 

With an adequate skin bridge from the anterior ankle distal tibial incision, make a 2- to 3-cm incision immediately posterior to the fibula, about 8 cm proximal to the tip of the fibula at the level of the peroneus longus' musculotendinous junction (TECH FIG 11A).

 

Protect the superficial peroneal nerve. However, with common peroneal nerve palsy, an injury to this terminal sensory branch will probably be inconsequential.

 

Sharply divide the peroneal retinaculum 2 to 3 cm longitudinally over the musculotendinous junction of the peroneus longus.

 

Divide the peroneus longus tendon at its musculotendinous junction (TECH FIG 11B).

 

 

 

TECH FIG 10 • Harvest of PTT for bridle procedure.

 

 

Place a tag suture in the transected distal end of the tendon.

 

Make another 2- to 3-cm incision over the lateral cuboid (see TECH FIG 11A).

 

Protect the sural nerve.

 

Isolate the peroneus longus tendon and pull its released proximal portion through this lateral foot wound (TECH FIG 11C,D).

 

Tuck the peroneus longus tendon in the distal lateral foot wound to keep it from desiccating.

 

The peroneus longus tendon will be passed to the anterior ankle wound (see in the following text).

Posterior Tibial Tendon Transfer through the Interosseous Membrane

 

 

Make an incision over the lateral aspect of the distal anterior tibia. Carefully expose the anterior IOM (TECH FIG 12A).

 

 

 

TECH FIG 11 • A-C. Harvest of peroneus longus for bridle procedure. A,B. Two small incisions, the first at the musculotendinous junction of peroneus longus and the second where the tendon courses around the cuboid. C. Peroneus longus transferred to distal lateral incision. D. Anticipated course for peroneus longus in bridle procedure (note also approximate course of PTT transfer).

 

 

93

 

 

 

TECH FIG 12 • Creating an IOM window to transfer the PTT to the anterior lower leg. A. Approach. B. Protecting deep neurovascular bundle and peroneal artery. C. Creating the window in the IOM. D,E. Transfer of the PTT to the anterior lower leg. D. Blunt clamp is passed directly on the posterior tibia from anterior to proximal medial wound to grasp tag suture in PTT. E. Ensuring that the tendon does not bind in the IOM window.

 

 

Protect the superficial peroneal nerve.

 

 

Divide the extensor retinaculum over the tibialis anterior and extensor hallucis longus tendons. Protect the deep neurovascular bundle (TECH FIG 12B).

 

 

Protect the peroneal artery branch that courses on the anterior IOM. Create a generous window in the distal IOM (TECH FIG 12C).

 

 

From tibia to fibula About 4 cm long

 

Pass a curved Kelly or tonsil clamp through the IOM directly on the posterior aspect of the tibia to exit in the proximal medial wound (TECH FIG 12D).

 

The posterior neurovascular structures (tibial nerve and posterior tibial artery) are at risk, so be sure the clamp is directly on the posterior tibia.

 

Use the tonsil clamp to grasp the tag sutures of the PTT.

 

Pull the tag sutures and PTT from the medial wound to the lateral wound, keeping the tendon directly on the posterior aspect of the tibia (TECH FIG 12E).

 

Be sure that the window in the IOM does not impinge on the transferred tendon. If there is stenosis, then further enlarge the window so that the tendon easily glides between the tibia and fibula.

 

Keep the tendon end in the wound to limit desiccation.

Transfer of the Peroneus Longus

 

Using a Kelly clamp, create a subcutaneous tunnel from the anterior distal tibial wound to the lateral foot wound (TECH FIG 13A).

 

Spread this tissue carefully with the clamp to avoid any soft tissue impingement within the tunnel.

 

Grasp the tag suture in the peroneus longus and pull the tendon from the lateral foot wound to the anterior distal tibial wound (TECH FIG 13B).

Transfer of Posterior Tibial Tendon through the Tibialis Anterior Tendon

 

Make a stab incision in the tibialis anterior tendon with proximal tension placed on the tibialis anterior tendon while the ankle is held in dorsiflexion.

 

This will tension the distal extent of the tibialis anterior tendon before it is secured to the PTT.

 

Avoid simply creating an incision in the tibialis anterior tendon in situ; this will render the tension in the medial aspect of the bridle ineffective.

 

Pass the PTT through this stab incision in the tibialis anterior (TECH FIG 14).

 

94

 

 

 

TECH FIG 13 • Transferring peroneus longus tendon from distal lateral foot wound to anterior lower leg wound. A. Subcutaneous tunnel to grasp free end of peroneus longus. B. Tendon transferred.

 

 

If a more secure fixation between the tibialis anterior and PTT is desired, then consider a Pulvertaft weave.

 

Although more weaving of the PTT through the tibialis anterior may afford greater fixation, it may in turn diminish the excursion of the PTT, thereby limiting the amount of distal PTT that will rest within the middle cuneiform's osseous tunnel.

Preparation of the Dorsum of the Foot and Anchoring the Posterior Tibial Tendon

 

 

Similar to that described for PTT transfer anterior to the tibia (see earlier) Transfer to the middle cuneiform

 

A separate incision may be made (two limited incisions anteriorly) or the anterior distal tibial approach may be extended to the dorsum of the foot (single extensile anterior incision).

 

Create an osseous tunnel in the middle cuneiform (TECH FIG 15A).

 

 

 

TECH FIG 14 • PTT is transferred through the tibialis anterior. Note the pretensioning of the tibialis anterior to optimize tension in the bridle.

 

 

Create a subcutaneous soft tissue tunnel from the dorsal foot incision to the more proximal and anterior lower leg incision using a curved Kelly clamp.

 

Use the clamp to grasp the tag sutures and pull the tendon through the subcutaneous tunnel to the dorsal foot incision (TECH FIG 15B).

 

Before anchoring the tendon in the osseous tunnel, pull the tendon via the tag sutures into the tunnel to be sure that the tunnel diameter is appropriate.

 

Pass a Beath pin or drill bit (has an eye to place suture) through the tunnel and the plantar skin (TECH FIG 15C). Because of the midfoot arch, this pin or drill bit will exit in the medial arch (TECH FIG 15D).

 

Dorsiflex the ankle.

 

With the tag sutures secured, pull the pin or drill bit through the plantar skin, thereby pulling the distal tendon end into the tunnel (TECH FIG 15E).

 

With the PTT properly tensioned in the second cuneiform's osseous tunnel, the PTT is anchored in a manner similar to that described earlier for the other techniques (interference screw with or without suture anchor in tunnel) (TECH FIG 15F,G).

 

 

 

TECH FIG 15 • A. Creating the osseous tunnel in middle cuneiform. B-G. Transferring PTT from anterior lower leg wound to dorsum of foot. B. Tendon passed through subcutaneous tunnel to dorsum of foot. C. Beath needle with tag sutures from PTT passed through osseous tunnel. (continued)

 

 

95

 

 

 

TECH FIG 15 • (continued) D. Tension on tag sutures on plantar foot. E. Tendon passed into middle cuneiform osseous tunnel. F. Positioning interference screw. G. Interference screw fully seated with appropriate PTT tension achieved.

Securing and Tensioning Tibialis Anterior and Peroneus Longus to the Posterior Tibial Tendon

 

Maintain the ankle in 10 degrees of dorsiflexion.

 

 

Balance the foot with respect to varus or valgus; it should have a neutral to slight valgus heel. Tibialis anterior

 

Tension the tibialis anterior proximally and suture the tibialis anterior and PTT to one another at the point where the PTT passes through the tibialis anterior.

 

Reinforce this connection with several more side-to-side sutures between the two tendons, both proximal and distal to where the PTT passes through the tibialis anterior.

 

Peroneus longus

 

Approximate the peroneus longus to the PTT where it passes anterior to the distal tibia and ankle, with maximum tension applied (TECH FIG 16).

 

Without support, the ankle should maintain dorsiflexed ankle and neutral hindfoot positions.

 

 

 

TECH FIG 16 • With the foot balanced, tibialis anterior and peroneus longus are secured to PTT transfer to create the bridle.

 

 

 

 

96

PEARLS AND PITFALLS
	Tension of ▪ Overtension rather than undertension, as some “stretching out” of the transfer is tendon anticipated transfer     Achilles ▪ The threshold to lengthen the gastrocnemius-soleus complex should be low. lengthening Obviously, with an Achilles contracture, lengthening is warranted. Transferring the PTT immediately reduces its power by one grade, so weakening the transfer's antagonist may be prudent. Overlengthening must be avoided.

 

	Residual ▪ Be sure the PTT is fully functional; if not, the transfer will not be dynamic but instead muscle simply a tenodesis. This is the objective in flaccid paralysis but not for a foot drop function secondary to a common peroneal nerve palsy.     Route of ▪ PTT transfer through the IOM may lead to stenosis. Provided there is no residual PTT peroneal (eversion) function, then transferring the PTT anterior to the tibia may lead to transfer an effective transfer without the risk of stenosis.     Bridle ▪ Balance the foot with proper tensioning of the tibialis anterior and peroneus longus procedure components of the transfer.     Anchoring ▪ With newer anchoring techniques, placing a suture button on the plantar foot secured the transfer to the tag suture is typically unnecessary.

 

POSTOPERATIVE CARE

 

We routinely place a well-padded short-leg cast in the operating room to protect the transfer, with the ankle in maximum dorsiflexion.

 

At first follow-up (2 to 3 weeks), we remove the cast while maintaining ankle dorsiflexion.

 

To protect the transfer, the ankle should not be allowed to plantarflex.

 

A new short-leg cast is applied, one that allows touchdown weight bearing.

 

Follow-up at 5 to 6 weeks from surgery.

 

 

The short-leg cast is removed, again protecting dorsiflexion. Wound inspection

 

Without allowing the ankle to plantarflex, the cast is removed.

 

Consideration may be given to creating a temporary AFO.

 

We typically place the patient in a short-leg walking cast at this point, with the ankle in near-maximum dorsiflexion. The patient is encouraged to walk.

 

At 8 to 10 weeks

 

The patient can typically discontinue use of the cast.

 

AFO for ambulation is typically worn until 4 to 5 months after surgery. During the final month of brace wear, the surgeon can consider hinging the AFO and placing a plantarflexion stop at neutral.

 

A cam boot is used for sleeping; it is typically worn until 4 to 5 months after surgery.

 

A physical therapy program is initiated to train the PTT to function as an ankle dorsiflexor.

 

Return to brace-free full function is not recommended before 6 months.

OUTCOMES

Select case series of PTT transfers for foot drop and bridle procedures suggest a satisfactory outcome in a majority of cases.

 

 

 

COMPLICATIONS

Infection

Wound dehiscence. The wound must be healed before initiating active dorsiflexion (usually not a problem because cast is maintained for at least 8 weeks).

Failure of the tendon transfer anchoring point; less common with newer anchoring system

Imbalance of bridle procedure: Tibialis anterior and peroneus longus must be properly tensioned intraoperatively.

 

 

SUGGESTED READINGS

1. Elsner A, Barg A, Stufkens SA, et al. Lambrinudi arthrodesis with posterior tibialis transfer in adult drop-foot. Foot Ankle Int 2010;31:30-37.

    

    

2. Hove LM, Nilsen PT. Posterior tibial tendon transfer for dropfoot. 20 cases followed for 1-5 years. Acta Orthop Scand 1998;69: 608-610.

    

    

3. Mizel MS, Temple HT, Scranton PE Jr, et al. Role of the peroneal tendons in the production of the deformed foot with posterior tibial tendon deficiency. Foot Ankle Int 1999;20:285-289.

    

    

4. Morita S, Muneta T, Yamamoto H, et al. Tendon transfer for equinovarus deformed foot caused by cerebrovascular disease. Clin Orthop Relat Res 1998;(350):166-173.

    

    

5. Rodriguez RP. The Bridle procedure in the treatment of paralysis of the foot. Foot Ankle 1992;13:63-69.

    

    

6. Soares D. Tibialis posterior transfer for the correction of foot drop in leprosy. Long-term outcome. J Bone Joint Surg Br 1996;78(1):61-62.

    

    

7. Sundararaj GD. Tibialis posterior transfer (circumtibial route) for foot-drop deformity. Indian J Lepr 1984;56:555-562.