Perform a physical examination that includes both static and dynamic measurements. Evaluate subtalar and ankle joint range of motion, both non-weight-bearing and weight-bearing.

The ankle joint should be pain-free even if it is stiff, noncongruent, or maloriented.

Perform a clinical axial examination of the hindfoot (calcaneal position) during static stance to help determine the hindfoot position.

Evaluate the alignment of the hindfoot in relation to the forefoot with a non-weight-bearing push-up test to load the foot, which simulates the midstance of gait. To determine a matching hindfoot-to-forefoot relationship, load the first and fifth metatarsal heads (forefoot) and the calcaneus (hindfoot) with a flat foot-board during a non-weight-bearing push-up examination.

Evaluate digital deformities preoperatively with the non-weight-bearing push-up test to determine their flexibility.

Conduct a Silfverskiöld test to determine the type and amount of equinus deformity.

Perform a clinical assessment of the foot height (sphyrion height) by measuring the distance from the standing surface to the tip of the medial malleolus.

Measure limb-length discrepancy on a full-length anteroposterior standing radiograph that includes the pelvis, femur, tibia, and foot. Calculate the overall limb length by adding measured limb segments (i.e., the pelvis, femur, tibia, and foot) and then compare the measurements with those of the contralateral limb to determine any discrepancy. Calculate the foot height contribution by subtracting the proximal segments from the overall limb-length discrepancy. If the patient is standing on a lift when the anteroposterior radiograph is obtained, make sure to account for the height of the lift in the discrepancy calculations.

Obtain a weight-bearing hindfoot alignment radiograph to assess the axial alignment. Use this radiograph to measure the relationship (angulation and translation) of the calcaneus to the tibia (i.e., the angle of the longitudinal axis of the calcaneus in relation to the tibial shaft)^2,3,4.

Obtain three weight-bearing radiographs of the foot and three of the ankle (lateral, anteroposterior, and medial oblique views). Use the lateral radiograph of the foot to draw the U-osteotomy around the center of rotation of the ankle joint (demarcated by the lateral process of the talus) on tracing paper^1,5,6. The paper tracing can be used to visualize the initial and final osteotomy positions by rotating the foot around the center of rotation of angulation in the sagittal plane (Fig. 1). The anteroposterior radiograph of the foot may also be used to plan the U-osteotomy correction in the transverse plane.

Use the lateral radiograph of the ankle to evaluate for osseous equinus (anterior ankle osteophytes) because preserving or maintaining a functional ankle joint is important for the final outcome. When the ankle joint is congruent, correct the osseous equinus by resecting the anterior ankle osteophytes. When the ankle joint is noncongruent, correct the osseous equinus with a U-osteotomy, which dorsiflexes the entire foot. Occasionally, both procedures may be performed together to fully correct the deformity.

Position the patient supine on a radiolucent table. Prepare and drape the entire lower limb up to the non-sterile thigh tourniquet using aseptic technique. Under tourniquet control, complete a prophylactic tarsal tunnel decompression prior to the osteotomy to prevent posterior tibial nerve entrapment⁷.

Place an ipsilateral hemisacral bump after completion of the prophylactic tarsal tunnel decompression to create a patella-forward position of the lower extremity. To facilitate lengthening, you can perform a posterior muscle group lengthening (gastrocnemius recession, gastrocnemius-soleus recession, or Achilles tendon lengthening) prior to the U-osteotomy.

Bend a 1.8-mm Ilizarov wire into a U configuration and lay the wire on the lateral side of the foot at the level of the proposed osteotomy under fluoroscopic guidance to determine the incision site and then mark the incision site on the skin.

Using the marks on the skin as a guide, make a modified Ollier-type incision on the lateral aspect of the foot. Identify the peroneal tendons and sural nerve, and retract the superficial peroneal nerve and extensor digitorum brevis muscle.

Dissect subperiosteally around the intended osteotomy level, along the lateral wall of the calcaneus, dorsal to the tuberosity of the calcaneus, anterior to the Achilles tendon insertion, and dorsal to the neck of the talus.

The U-osteotomy passes across the neck of the talus, through the sinus tarsi, and under the sustentaculum tali of the calcaneus to exit posterior and dorsal in the calcaneus.

Mark the intended level of the osteotomy with multiple orthogonally inserted 1.8-mm Ilizarov wires along its course and check their positioning with fluoroscopy (Fig. 2).

Complete the U-osteotomy by connecting the multiple 1.8-mm Ilizarov wire holes with a small Hoke osteotome (Fig. 3-A). You can use multiple small osteotomes simultaneously to create the U-osteotomy. Avoid penetrating the soft-tissue structures on the medial side.

Complete the U-osteotomy and use fluoroscopy to demonstrate that the bone segments can translate and to confirm the completeness of the osteotomy. A non-toothed laminar spreader can help distract the osteotomy site to visualize the medial cortex (Fig. 3-B). Elevate the medial periosteum from the calcaneus to allow easier motion of the segment. Perform other corrective foot and ankle procedures as needed.

Deflate the tourniquet, obtain hemostasis, and close the incision over a drain as needed.

Choose the number and size of the rings of the Taylor Spatial Frame (Smith & Nephew, Memphis, Tennessee) to be used according to the size of the foot and leg. Place the tibial ring or tibial block (two rings) on the leg first, prior to insertion of the lateral-to-medial 1.8-mm Ilizarov distal tibial wire. Apply the tibial ring or tibial block perpendicular to the long axis of the tibia, and ensure adequate clearance between the soft tissues and the rings.

Place a bicortical 1.8-mm transverse Ilizarov wire at the junction of the middle and distal thirds of the tibia from medial (starting just anterior to the fibula) to lateral perpendicular to the tibia on the anteroposterior fluoroscopic view. Oscillate (rather than drill) the wire after the far cortex has been penetrated to prevent entanglement of nerves and soft tissues. Connect the 1.8-mm Ilizarov wire to the full tibial ring or tibial block with wire fixation bolts tensioned to the ring at 130 kg.

Add two tall half-pin fixation cubes (one up, one down) to the tibial ring. For the down-facing cube, choose a location that will not interfere with the struts. Using the sagittal view on the image intensifier, rotate the tibial ring on the transverse wire until it is perpendicular.

Insert the two 6-mm half-pins after the bone has been predrilled with a 4.8-mm drill bit. For small-diameter bones, we use a 3.8-mm drill bit to predrill for 4.5-mm half-pins. Tighten the cubes to the ring, and secure the half-pins to the cubes using two set screws for each half-pin. We use hydroxyapatite-coated half-pins for increased longevity. Surgeon preference determines whether wires, half-pins, or a combination (which we prefer) are used to construct the tibial external fixation. Be careful to place wires and half-pins in the safe zones (to avoid the neurovascular structures) and avoid the anticipated position of the Taylor Spatial Frame struts.

Apply the U foot ring completed with a half-ring parallel to the weight-bearing surface of the foot (Figs. 4 and 5-F). Ensure that there is sufficient clearance circumferentially between the foot and the foot ring.

Attach the foot ring to two crossed 1.8-mm olive wires that are inserted through the calcaneus. One is inserted transversely from medial to lateral. The other is inserted obliquely from medial-posterior to lateral-anterior. Tension both calcaneal wires to 90 kg. Insert a transverse midfoot smooth wire and tension it to 70 kg.

Next, insert two 1.8-mm smooth wires and an optional olive wire (all called stirrup wires) through the talus and the sustentaculum tali. Ideally, the two smooth stirrup wires are passed transversely from medial to lateral, just above the osteotomy site (one in the sustentaculum tali and one through the talar neck). Bend them 90° outside the skin to attach them to the tibial ring without tension. An optional third stirrup wire (olive wire) can be used for a third point of talar fixation to increase the stability of the talar segment because this wire is also attached to the tibial ring. Before inserting this olive wire, place a temporary smooth 1.8-mm wire through the plantar aspect of the calcaneus into the sustentaculum tali fragment by overdrilling with a cannulated 4.5-mm drill from the calcaneus just into the sustentaculum tali. Remove the temporary 1.8-mm smooth wire, and insert an olive wire to the level of the skin. Then cut the olive wire, bury it up against the sustentaculum tali, and attach it anteriorly to the distal tibial ring. Alternatively, place this olive wire obliquely from the posterior-lateral to the anterior-medial aspect of the talus. Some surgeons prefer to insert the two smooth stirrup wires into the sustentaculum tali fragment and talar body prior to applying the foot ring. Use of the image intensifier coupled with the ability to position the foot in multiple oblique angles helps you to place these wires precisely.

Perform a percutaneous tenotomy and/or pinning of contracted toes when the toes are rigid. The pin exiting each toe is then affixed to the external fixation device for additional stability. However, when the toes are flexible, we recommend only postoperative splinting of the toes with a custom-molded toe sling.

After the external fixation is applied, connect the six Taylor Spatial Frame struts between the tibial and foot rings. Typically, the ring closest to the osteotomy (the foot ring) is considered to be the reference ring, as per the Taylor Spatial Frame planning protocol.

After cleaning the foot with saline solution, place Ilizarov sponges around the pin sites and use sterile gauze to cover all incisions. Admit the patient to the hospital for pain and drain management.

Suspend a walking ring with a cast shoe below the foot ring so that the patient can perform weight-bearing as tolerated and undergo physical therapy and occupational therapy prior to discharge.

At the end of surgery, obtain lateral and anteroposterior radiographs in the operating room with the central beam aimed orthogonal to the reference ring with magnification and ring-centering markers. These radiographs allow for calibration of the Taylor Spatial Frame mounting parameters.

Record the ring sizes and strut lengths and sizes. Enter the mounting and deformity parameters into the Internet-based computer program for the Taylor Spatial Frame to generate a daily schedule for the external fixation adjustments. We currently use the newest version (version 4.1) of the Internet-based program for the Taylor Spatial Frame. The “Long Bone” program, not the various foot modules, is most appropriate for planning the U-osteotomy.

Perform the correction in two stages. The Internet-based computer program for the Taylor Spatial Frame should be programmed to purely lengthen to disengage the pieces (Fig. 1-B). Then the software can be reprogrammed to correct varus, valgus, flexion, extension, rotation, and translation without fear of the segments impinging on each other and limiting correction (Fig. 1-C). The amount of foot height (created by posterior opening of the U-osteotomy) should be comparable with the contralateral foot height, or it may moderately exceed this height if additional limb lengthening is necessary for limb equalization.

To avoid premature consolidation, begin distraction at a rate of approximately 1 mm per day starting three to five days after surgery^5,8.

Maintain the external fixation device until complete consolidation occurs while allowing weight-bearing as tolerated. A walker, a cane, or crutches are used for additional balance.

Educate the patient preoperatively and postoperatively on pin-site care. After seven days, the patient begins showering and cleaning the pin sites with a cotton-tip applicator and normal saline solution. Instruct the patient to gently clean the pin sites once daily. Aggressive cleaning disrupts the skin-pin interface (barrier), which can result in a pin-site infection. No dressings are required for the pin sites unless they are draining. If they are draining, apply dry gauze and prescribe oral antibiotics on the basis of pin-site culture results.

See the patient in your office every two weeks during the distraction phase (modified as necessary for strut changes). After adequate distraction and appropriate alignment have been achieved, the patient is in the consolidation phase and is seen monthly.

See the patient more frequently if compliance is a concern or if problems or questions arise during treatment. The external fixation may become unstable and require tightening or adjustment of the wires and/or half-pins in the office or in the operating room. The patient may need to return to the operating room for additional adjunctive procedures (e.g., to address nerve entrapment or digital contractures, or to perform pin exchange).

Obtain serial radiographs during each office visit to evaluate correction of the deformity, the amount of distraction, evidence of lucency around the pin sites, and the amount of osseous consolidation. Perform fluoroscopy as necessary during an office visit to improve osseous visualization.

If the toes have become contracted during treatment, perform a flexor tenotomy at the time of external fixation removal.

Gently curet the open pin sites, clean them with sterile saline solution, cover them with sterile dressings, and allow closure by secondary wound-healing.

Place the foot and ankle in a short leg walking cast for protected walking for one month.

Preexisting stiffness and/or fusion of the subtalar joint with a pain-free ankle joint

A uniform deformity of the foot in relation to the tibia in which the forefoot and hindfoot deformities match each other

Short foot height or limb-length discrepancy

A mobile subtalar joint

The forefoot deformity differing from the hindfoot deformity

Active infection

Vascular insufficiency

To prevent the development of a knee flexion contracture, the posterior calf muscle group can be lengthened at the initial surgery or the U-osteotomy can be modified to an L or tick osteotomy¹⁰ to exit distal to the Achilles tendon insertion. Also, the external fixation device can be modified to allow knee extension or physical therapy.

Overlengthening or underlengthening should be avoided. The amount of foot height or the posterior aspect of the “cornucopia” (i.e., the posterior opening of the U-osteotomy) should be comparable with the contralateral foot height, or it may exceed this height if additional limb lengthening is necessary for limb equalization.

Prophylactic tarsal tunnel decompression should be performed because deformity correction through the U-osteotomy creates nerve tension. Preoperatively, it is important to consider how the soft-tissue structures (e.g., nerves, muscles, skin, and vessels) will be affected.

To prevent digital contracture, we recommend splinting the toes when they are flexible, performing percutaneous tenotomy and/or pinning if the toes are rigid at the beginning of treatment, and performing percutaneous flexor tenotomy at the time of fixator removal if the toes become contracted during treatment.

Which prophylactic measures have you found to be effective in reducing complications during the U-osteotomy?

What are the indications for the U-osteotomy?

What are the advantages of the U-osteotomy?