Operative Techniques in Orthopaedic Surgery (4 Volume Set) 1st Edition

531. Tendon Transfer for Foot Drop

Mark E. Easley and Aaron T. Scott

DEFINITION

images Pathology leading to a spectrum of motor function loss that includes loss of ankle dorsiflexion

images Common peroneal nerve palsy, L5 radiculopathy, cerebrovascular accident

images Loss of ankle dorsiflexion and hindfoot eversion

images Retained posterior tibial tendon (PTT) function

images Hereditary sensory motor neuropathy

images A constellation of motor function deficits and associated deformity

images Includes loss of dorsiflexion and hindfoot eversion

images Retained PTT function

images Flaccid paralysis

images Global loss of motor function to the ankle and foot

ANATOMY

images Posterior tibialis

images Muscle originates on the posterior tibia, interosseous membrane, and fibula.

images Muscle and then tendon course in the deep posterior compartment.

images Tendon travels directly posterior to the medial malleolus.

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

images Interosseous membrane (IOM) and distal tibia–fibula syndesmosis

images Thick fibrous bands between tibia and fibula

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

images Inferior extensor retinaculum

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

images Sciatic nerve

images Comprises tibial and common peroneal nerves that separate immediately proximal to the popliteal fossa

images Common peroneal nerve often affected in these neuropathies

images Superficial peroneal nerve

images Motor function to anterior and lateral compartment muscles

images Dorsiflexion and eversion, respectively

images Sensory distribution to dorsum of the foot

images Deep peroneal nerve

images Courses between tibialis anterior and extensor hallucis longus tendons proximal to the ankle

images Located directly on the dorsum of midfoot

images Immediately deep to extensor hallucis brevis muscle belly

images Motor function to intrinsic muscles of foot

images Sensory distribution to first web space

images Tibial nerve function typically spared

images Tibial nerve must be intact to create a dynamic tendon transfer

images If tibial nerve is not intact, then transfer can only be a tenodesis

images Anterior ankle and dorsal midfoot neurovascular structures at risk

images Superficial peroneal nerve (may be insensate as part of the neuropathy)

images Deep neurovascular bundle

images Anterior tibial artery

images Deep peroneal nerve (may also be insensate as part of the neuropathy)

images Peroneal artery branch

images Situated directly on anterior distal IOM

PATHOGENESIS

images Loss of common peroneal nerve function

images Loss of ankle dorsiflexion and hindfoot eversion

images Loss of major antagonists

images Eventual equinus contracture

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

images Eventual hindfoot varus deformity

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

images Flaccid paralysis

images Tibial and common peroneal nerve palsies

images No motor function distal to knee

images Since both sets of major antagonists lost, typically no contractures

NATURAL HISTORY

images Foot drop may eventually recover.

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

images 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.

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

PATIENT HISTORY AND PHYSICAL FINDINGS

images Gait abnormality

images “Slap foot gait”

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

images Exaggerated hip and knee flexion

images Inability to dorsiflex ankle or great toe from push-off through swing phase

images Compensation to allow toes to clear during swing phase

images Hindfoot inversion

images Patient walks on lateral border of foot.

images Inability to dorsiflex ankle

images May check by asking patient to walk on heels

images Manual muscle testing with patient seated on examining table with knee flexed

images Lack of eversion

images Varus hindfoot

images Over time, may become a fixed inversion contracture

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

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

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

images Passive dorsiflexion of the ankle will reveal this.

images With equinocavovarus foot contracture, calluses may form under metatarsal heads, particularly the fifth.

images Sensation may be diminished on the dorsal and lateral aspects of the foot.

IMAGING AND OTHER DIAGNOSTIC STUDIES

images Imaging is typically unnecessary for patients with foot drop except in the following situations:

images Consideration should be given to MRI:

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

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

images Consideration should be given to radiographs of foot or ankle:

images To rule out stress fracture

images 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)

images Electrodiagnostic studies

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

images Nerve conduction studies and electromyography

images Baseline and follow-up studies to determine if any recovery evident

images Important to determine if tendon transfer is warranted

images Tendon transfer should not be performed if nerve function may recover!

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

images We recommend consultation with a neurologist to confirm interpretation of electrodiagnostic studies.

images Studies may also define function of PTT.

images Important when considering dynamic PTT transfer versus PTT tenodesis

images 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.

images Useful in determining if a more proximal compressive neuropathy exists

DIFFERENTIAL DIAGNOSIS

images Tibialis anterior tendon rupture

images Cerebrovascular accident

images Lumbar spine radiculopathy

images Hereditary sensorimotor neuropathy

images Leprosy

images Poliomyelitis

images Cerebral palsy (spastic)

NONOPERATIVE MANAGEMENT

images Bracing with an ankle–foot orthosis (AFO)

images Requires a fixed AFO in flaccid paralysis

images May be a flexible AFO with common peroneal palsy

images Requires plantarflexion stop

images Equinus contracture may need to be corrected to facilitate bracewear.

images Achilles stretching

images Botulinum toxin injection

images Tendo Achilles lengthening (TAL)

images Varus deformity

images If flexible may be corrected with bracing

images If fixed, bracing is difficult.

SURGICAL MANAGEMENT

Preoperative Planning

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

images Serial clinical examination

images Serial electrodiagnostic studies (at least one compared to baseline)

images The surgeon must determine what motor function persists:

images Tibial nerve

images PTT (inversion)

images Gastrocnemius–soleus (plantarflexion)

images None (flaccid paralysis)

images The surgeon must evaluate for equinus contracture.

images The surgeon should be prepared to perform TAL if necessary (see Tech Fig 1AD).

images Flexible versus fixed deformities

images Flexible deformity typically corrects with tendon transfer alone.

images Fixed deformity

images May require capsular release or even arthrodesis

images Toe contractures

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

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

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

images Tendon transfer anchoring

images We routinely use interference screws to anchor tendon transfers to bone.

images Need to have an anchoring system available

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

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

images 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

images Supine

images 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.

images We routinely use a thigh tourniquet.

Approach

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

images PTT harvest

images Medial harvest over navicular

images Posteromedial tibia at musculotendinous junction of PTT

images PTT transfer through the IOM

images Incision over distal IOM

images Incision over dorsolateral foot

images PTT transfer anterior to tibia

images Incision over central midfoot

images Bridle procedure

images Same PTT harvest

images PTT transfer through IOM with incision directly anterior over distal tibia; may be extended to dorsal foot. Alternatively, separate small incision over centrodorsal midfoot.

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

TECHNIQUES

ACHILLES LENGTHENING

images Indications

images Not always necessary, but typically required when foot drop occurs

images Without active dorsiflexion the gastrocnemius– soleus' antagonist is lost, often leading to an Achilles contracture.

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

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

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

images Technique

images Determined by the Silfverskiold test

images Equinus contracture with the knee in extension and flexion (Tech Fig 1A)

images

Tech Fig 1 • Tendo Achilles lengthening. A. Equinus with knee in flexion and extension suggests tight gastrocnemius and soleus. B. Initial Achilles hemisection. C. Second Achilles hemisection (opposite direction from first), to be followed by third and final hemisection in same direction as first. D. Dorsiflexion re-established after Achilles lengthening.

images Triple hemisection (Hoke procedure) because both the gastrocnemius and soleus are contracted (Tech Fig 1BD)

images 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

images Advantages

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

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

images Disadvantage

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

Posterior Tibial Tendon Harvest

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

images Open the PTT sheath to expose the tendon.

images Release the PTT insertion on the medial navicular.

images 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).

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

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

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

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

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

images 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).

images

images

Tech Fig 2 • Posterior tibial tendon (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. 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.

images Place tag sutures in the distal PTT (Tech Fig 2D,E).

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

images 3-cm incision (Tech Fig 2F)

images Flexor digitorum tendon is usually encountered first.

images Deep to the FDL, directly on the posteromedial tibia, the PTT is identified.

images Place a blunt retractor around the PTT through this more proximal wound to isolate it.

images Mobilize the distal PTT.

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

images This may not work.

images 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.

images Once mobilized, the distal aspect of the PTT may be transferred to the proximal wound (Tech Fig 2H).

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

Posterior Tibial Tendon Transfer Through the Interosseous Membrane

images Lateral incision on anterior aspect of distal fibula, at distal tibiofibular syndesmosis

images Careful exposure of anterior IOM

images Elevate the anterior compartment soft tissues.

images A branch of the peroneal artery courses on the anterior IOM and is at risk.

images Create a generous window in the distal IOM (Tech Fig 3A).

images From tibia to fibula

images About 3 to 4 cm long

images 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).

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

images

Tech Fig 3 • PTT transfer through the interrosseous membrane (IOM). A. A window is carefully created in the interosseous membrane (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. Posterior tibial tendon (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.

images Use the tonsil clamp to grasp the tag sutures of the PTT (Tech Fig 3C).

images 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).

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

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

images Keep the tendon end in the wound to limit desiccation.

Preparation of the Dorsal Foot Anchor Site

images Fluoroscopically identify the center of the lateral cuneiform.

images Oblique foot views usually best define the lateral cuneiform (Tech Fig 4A).

images Center a 3to 4-cm longitudinal skin incision directly over the lateral cuneiform.

images Dissect to the lateral cuneiform.

images Protect the superficial peroneal nerve and extensor tendons.

images Deep neurovascular bundle is usually medial to this approach.

images Expose and define the cuneiform.

images 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).

images Periosteum and capsular tissue are left intact.

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

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

images Remove the wire and introduce sequentially larger drill bits to enlarge the tunnel (Tech Fig 4C).

images

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.

images We use drill bits to a diameter of 4.5 mm.

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

images Introduce the reamer system for the interference screw system to enlarge the tunnel to the desired diameter (Tech Fig 4D).

images 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

images 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).

images 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).

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

images 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.

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

images 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).

images Dorsiflex the ankle.

images 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).

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

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

images Anchoring the tendon to bone

images 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).

images

images

Tech Fig 5 • Posterior tibial tendon (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). 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.

images A properly sized isolated interference screw is probably adequate.

images 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.

images 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 5MO).

images Have the assistant maintain full ankle dorsiflexion and tension on the tag sutures on the plantar foot.

images We usually cut the tag sutures so they retract beneath the skin.

images 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.

images 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.

POSTERIOR TIBIAL TENDON TRANSFER ANTERIOR TO THE TIBIA

images Advantages

images PTT has no opportunity to stenose in the IOM.

images Glides smoothly around anteromedial tibia

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

images

Tech Fig 6 • Adequate dorsiflexion (essential for successful tendon transfer to re-establish dorsiflexion).

images Disadvantage

images PTT is not in direct line from its origin to anchor point in the foot; it must travel around medial tibia.

images Anchor point is in the middle (second) cuneiform.

images Central location so it cannot provide an eversion moment

images However, typically unimportant since with PTT transfer the agonist–antagonist balance between PTT and peroneus brevis is again re-established by being neutralized.

Achilles Lengthening

images Same as for PTT transfer through IOM described earlier (Tech Fig 6)

Posterior Tibial Tendon Harvest

images Same as for PTT transfer through IOM described earlier (Tech Fig 7)

Preparation of the Dorsal Foot Anchor Site

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

images

images

Tech Fig 7 • Approach to posterior tibial tendon (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). 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.

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

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

images Middle cuneiform is smaller than the lateral cuneiform.

images In our experience, greater risk of fracture with drill hole, tendon transfer, and interference screw

images Fluoroscopically identify the center of the middle cuneiform.

images AP and sometimes oblique foot views best define the middle cuneiform.

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

images Dissect to the middle cuneiform.

images Protect the superficial peroneal nerve and extensor tendons (Tech Fig 8A).

images Protect the deep neurovascular bundle, usually encountered in this approach; it is directly deep to the muscle of the extensor hallucis brevis.

images Expose and define the cuneiform.

images 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).

images Leave the periosteum and capsular tissue intact.

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

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

images Remove the wire and introduce sequentially larger drill bits to enlarge the tunnel (Tech Fig 8C).

images We use drill bits to a diameter of 4.5 mm.

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

images

images

Tech Fig 8 • Preparation of dorsal foot osseous tunnel. A. Dorsal incision over middle cuneiform. B. Middle cuneiform is identified and marked.C. Increasingly largerdiameter drill bits. D. Increasingly larger reamers (judiciously, since the middle cuneiform is not particularly large).

images Use the reamer from the interference screw system to enlarge the tunnel to the desired diameter (Tech Fig 8D).

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

Posterior Tibial Tendon Transfer to Dorsum of Foot

images 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).

images 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).

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

images 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.

images 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).

images Dorsiflex the ankle.

images 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).

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

images

images

Tech Fig 9 • Transfer of posterior tibial tendon (PTT) to dorsum of foot. A. Subcutaneous tunnel for blunt clamp to grasp tag suture in PTT. 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.

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

images Anchoring the tendon to bone

images 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.

images A properly sized isolated interference screw is probably adequate.

images 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.

images To further augment the anchor point

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

images 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).

images Have the assistant maintain full ankle dorsiflexion and tension on the tag sutures on the plantar foot.

images We usually cut the tag sutures so they retract beneath the skin.

images 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.

BRIDLE PROCEDURE

images Advantages

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

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

images Disadvantage

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

images Functions as a tenodesis

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

images

Tech Fig 10 • Harvest of posterior tibial tendon for bridle procedure.

Achilles Lengthening

images Same as for PTT transfer through IOM described earlier

Posterior Tibial Tendon Harvest

images Same as for PTT transfer through IOM described earlier (Tech Fig 10)

Harvest of the Peroneus Longus

images With an adequate skin bridge from the anterior ankle distal tibial incision, make a 2to 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).

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

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

images Divide the peroneus longus tendon at its musculotendinous junction (Tech Fig 11B).

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

images Make another 2to 3-cm incision over the lateral cuboid (Tech Fig 11A).

images Protect the sural nerve.

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

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

images The peroneus longus tendon will be passed to the anterior ankle wound (see below).

images

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 posterior tibial tendon transfer).

Posterior Tibial Tendon Transfer Through the Interosseous Membrane

images Make an incision over the lateral aspect of the distal anterior tibia.

images Carefully expose the anterior IOM (Tech Fig 12A).

images Protect the superficial peroneal nerve.

images Divide the extensor retinaculum over the tibialis anterior and extensor hallucis longus tendons.

images Protect the deep neurovascular bundle (Tech Fig 12B).

images Protect the peroneal artery branch that courses on the anterior IOM.

images Create a generous window in the distal IOM (Tech Fig 12C).

images From tibia to fibula

images About 4 cm long

images 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).

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

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

images 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).

images 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.

images Keep the tendon end in the wound to limit desiccation.

Transfer of the Peroneus Longus

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

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

images 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

images 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.

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

images 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.

images

Tech Fig 12 • Creating an interosseous membrane (IOM) window to transfer the posterior tibial tendon 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 posterior tibial tendon (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.

images

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.

images Pass the PTT through this stab incision in the tibialis anterior (Tech Fig 14).

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

images While 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

images Similar to that described for PTT transfer anterior to the tibia (see earlier)

images Transfer to the middle cuneiform

images 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).

images

Tech Fig 14 • Posterior tibial tendon is transferred through the tibialis anterior. Note the pretensioning of the tibialis anterior to optimize tension in the bridle.

images Create an osseous tunnel in the middle cuneiform (Tech Fig 15A).

images 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.

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

images 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.

images 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).

images Dorsiflex the ankle.

images 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).

images

images

Tech Fig 15 • A. Creating the osseous tunnel in middle cuneiform. B–G. Transferring posterior tibial tendon (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. 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.

images 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).

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

images Maintain the ankle in 10 degrees of dorsiflexion.

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

images Tibialis anterior

images 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.

images 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.

images Peroneus longus

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

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

images

Tech Fig 16 • With the foot balanced, tibialis anterior and peroneus longus are secured to posterior tibial tendon transfer to create the bridle.

images

POSTOPERATIVE CARE

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

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

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

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

images Follow up at 5 to 6 weeks from surgery.

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

images Wound inspection

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

images Consideration may be given to creating a temporary AFO.

images 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.

images At 8 to 10 weeks

images The patient can typically discontinue use of the cast.

images 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.

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

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

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

OUTCOMES

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

COMPLICATIONS

images Infection

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

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

images Imbalance of bridle procedure: tibialis anterior and peroneus longus must be properly tensioned intraoperatively

REFERENCES

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 drop-foot: 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.

3.     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.

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

5.     Soares D. Tibialis posterior transfer for the correction of foot drop in leprosy: long-term outcome. J Bone Joint Surg Br 1996 Jan;78(1):61–2.

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



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