Bryan D. Den Hartog
INDICATIONS
Talar body avascular necrosis with collapse or infection (FIG 1) is one indication for femoral head allograft.
Failed total ankle arthroplasty with insufficient bone remaining for revision (FIG 2) also warrants a femoral head allograft.
Use of a femoral head graft for those patients with severe (> 25 degrees) hindfoot valgus may not be appropriate, because correction of the deformity can cause significant lateral soft tissue tension and lead to tissue necrosis and poor wound healing. In those cases, a tibiocalcaneal fusion with shortening of the medial ankle may be more appropriate.
FIG 1 • Lateral radiograph demonstrating avascular necrosis and infection of the talar body after open fracture–dislocation.
POSITIONING
Under a general or spinal anesthetic block, the patient is placed in a supine position on the operating table with the ipsilateral hip bumped to facilitate internal rotation of the leg.
The lower extremity is prepped and draped in the usual fashion, and a thigh tourniquet inflated to 250 mm Hg is applied after exsanguination of the leg with an Esmarch bandage.
FIG 2 • Radiographs of a failed total ankle arthroplasty with severe loss of talar bone stock.
TECHNIQUES
PREPARATION FOR ALLOGRAFT
A 12to 14-cm lateral incision is made along the distal fibula, starting 6 cm above the ankle joint and extending distally along the anterior border of the peroneal tendons to the peroneal tubercle (TECH FIG 1).
The tendons are carefully retracted posteriorly to expose the distal fibula, lateral ankle, and subtalar joints.
The fibula is osteotomized 6 cm above the joint, then excised and morcelized for later grafting (TECH FIG 2).
Débridement of avascular bone and removal of osteophytes and implant is performed until only viable bone surfaces remain (ie, distal tibial plafond, talar head and neck, and posterior facet of the subtalar joint).
Determine the size of acetabular reamer from the total hip arthroplasty set that best fits the defect (TECH FIG 3).
Only enough subchondral bone is removed from the tibia, talar neck, and calcaneus to expose viable, softer cancellous bone for fusion to the femoral head graft. If an assistant holds the foot and ankle in the desired position, the surgeon can ream the defect safely, without the ankle bouncing around. No provisional fixation is necessary: the ankle is still relatively stable even after the ankle implant or necrotic bone is removed.
TECH FIG 1 • Patient positioned supine on the operating table. A lateral incision is made over the distal fibula and lateral hindfoot.
TECH FIG 2 • A fibulectomy is performed to expose the ankle and subtalar joints and lateral calcaneus.
TECH FIG 3 • The defect remaining after talectomy is sized with the male reamers from the hip arthroplasty set.
With the ankle and hindfoot held in neutral, the defect is reamed (TECH FIG 4). The desired position of fusion is with the ankle in neutral plantar/dorsiflexion flexion and the hindfoot in approximately 5 degrees of valgus in relation to the distal tibia.
It is critical to protect the soft tissue about the ankle with either Army-Navy or Hohmann retractors while the acetabular reamers are used.
Bone shavings are saved and mixed with the morcelized fibular graft.
TECH FIG 4 • The bone surrounding the defect is reamed until cancellous bone is exposed on the distal tibia, talar neck, and calcaneus.
PREPARATION AND PLACEMENT OF ALLOGRAFT
An allograft femoral head is thawed in a warm saline bath at the beginning of the procedure and placed in the bone vice (Allogrip Vice, DePuy), with the three limbs of the vice gripping the femoral neck.
The female reamer corresponding to the same size male reamer used for reaming the defect is used to decorticate the allograft (TECH FIGS 5 AND 6).
The head can be drilled multiple times in areas that still contain hard sclerotic bone to facilitate fusion.
The appropriately sized and decorticated femoral head allograft is then placed in the defect (TECH FIG 6B).
Ankle and foot position is then checked for neutral position (ie, neutral ankle dorsiflexion–plantarflexion, 5 degrees of hindfoot valgus, and neutral rotation of the foot on the tibia). Because the femoral head graft is spherical, it is relatively easy to dial in the correct position of the ankle and hindfoot.
TECH FIG 5 • A. A frozen femoral head allograft is thawed and placed in the Allogrip Bone Vice (DePuy). B. The female reamer (DePuy) is used to remove the subchondral bone from the allograft to expose cancellous bone and size the graft.
TECH FIG 6 • A–B The femoral head graft is placed in the defect to ensure proper sizing.
The femoral neck is marked flush with the lateral tibia, the graft is removed, and the femoral neck is cut with a large oscillating saw.
A bone slurry graft, made up of the autograft from the fibula and male reamers, is then placed in the defect to fill any voids around the fusion site (TECH FIG 7).
The male reamers can again be placed and used in reverse to evenly spread the graft.
The femoral head graft is placed back in the defect, and alignment is checked to ensure that it sits flush with the lateral fusion surface. Again, no provisional fixation is needed, as the interference fit between the femoral head and the recipient site is very stable.
This will allow unimpeded placement of the lateral blade plate.
TECH FIG 7 • Once sizing is complete, a slurry of graft reamings is placed in the base of the defect and the reamers placed in reverse to spread the graft.
PLACEMENT OF PLATE AND SCREWS
The 90-degree blade plate is then sized by placing it along the lateral fusion surface equidistant between the anterior and posterior surfaces of the tibia and femoral head graft.
In my experience, fixation with six to eight cortical screws in the tibia proximal to the femoral head allograft is desirable; therefore, a blade plate of appropriate length is required. The decision depends on the quality of bone. Typically, for six cortical screws to be positioned in the tibia above the graft, a nine-hole blade plate will be needed.
The distal end of the plate (the blade end) should line up with the center of the calcaneal body to ensure maximum hold and minimize the chance of fracturing the calcaneus with insertion.
Usually a sixto eight-hole plate with the short blade fits well.
Once the plate size has been selected, place the plate “backward” along the lateral fusion area so the blade is pointing lateral (TECH FIG 8). This technique allows for proper angle of insertion of the guidewire and, therefore, the blade of the plate.
TECH FIG 8 • The blade plate is placed in a “backward” position along the fusion site for sizing. A guidewire is passed through the hole in the blade into the calcaneus.
Check the hole alignment to ensure that at least one screw hole is over the calcaneus, one in the femoral head allograft, and two or three in the distal tibia.
Drive the guidewire through the cannulated hole in the blade to the distal cortex of the calcaneus.
Pull the plate off the wire.
Because the plate could theoretically still rotate on the distal guide pin in the calcaneus, I often place a second wire through the plate. I use one of the screw holes proximally to ensure that when I flip the plate and impact it there is no chance that it will lose its desired proximal position on the tibia and potentially throw off the sagittal alignment or not be seated ideally on the tibia.
Attach the driving device onto the plate and insert the blade plate over the guidewire (TECH FIG 9A,B). The 30-mm blade is most commonly used, because the 40mm blade can easily penetrate the medial cortex and injure the neurovascular bundle.
Be sure to have an assistant apply counterpressure with a padded bolster while driving the plate into the calcaneus.
A separate guidewire driven through a proximal hole in the plate may help avoid unwanted twisting or rotation of the plate during insertion.
Once the plate is seated, the position of the blade is checked to make sure it has not penetrated the medial cortex of the calcaneus. Again, if the 30-mm blade is used, penetration of the medial cortex should not occur.
The screws (cancellous or cortical, depending on the type and quality of bone) are then inserted (TECH FIG 9C). In addition to the blade in the calcaneus, I like to have one additional screw through a distal hole in the plate, immediately above the blade, to enhance fixation in the calcaneus.
A 7-mm cannulated screw is then placed from the posterolateral side of the distal tibia through the femoral head graft into the talar head and neck.
Fluoroscopy is used to check guidewire placement.
Avoid penetration into the talonavicular joint.
A second cannulated screw can be placed from the calcaneal tuberosity into the femoral head graft if the blade-plate fixation to the calcaneus is not stable, as indicated by visible micromotion at the fusion interface or if the patient's bone is osteoporotic. In about half of my patients, this second screw is needed to gain adequate stability of fixation.
Use the remaining autograft to fill any remaining gaps at the fusion sites anteriorly, posteriorly, and laterally.
A layered closure over a drain is done, and a bulky Jones dressing applied.
TECH FIG 9 • A. The blade is pulled off the wire and the driving device attached. B. The blade is driven into the calcaneus over the guidewire. C. Appropriate length screws are applied.
POSTOPERATIVE CARE
Remove the bulky dressing 10 to 14 days postsurgery.
The patient is in a short-leg cast for 6 to 8 weeks, with touch-down weight bearing permitted.
The patient can begin weight bearing in a cam-soled walker at 2.5 to 3 months postoperatively if radiographs show signs of incorporation of the bone graft placed about the femoral head and fusion between the graft and the surrounding cancellous bone (FIG 3).
FIG 3 • AP (A) and lateral (B) radiographs taken 3 months postoperatively demonstrating callus formation about the femoral head allograft.
We recommend that all of our patients use a non-hinged, light-weight, plastic ankle–foot orthosis (AFO) in a shoe with a soft anatomic cushioned heel indefinitely to protect the remaining joints of the foot.
OUTCOMES
Our clinical experience with this technique includes five patients who underwent tibiotalocalcaneal fusion over 3 years.3 Four patients showed radiographic healing by 3 months and began protected weight bearing with a lightweight plastic AFO. One of these four patients subsequently died of a myocardial infarction. The fifth patient was paralytic with severe hindfoot valgus and developed lateral skin breakdown with subsequent methicillin-resistant Staphylococcus aureus (MRSA) infection postoperatively over the graft site; that patient eventually underwent below knee amputation.
Of the four patients who had a good result, the average follow-up was 1.5 years. None of the femoral grafts had collapsed, and all patients had good or excellent relief of their preoperative pain with no loss of leg length. The three surviving patients are community ambulators and use the lightweight AFO for walking outside the home to protect the remaining foot joints from excessive stress.
The lateral blade–plate–screw construct for stabilizing tibiotalocalcaneal fusions has been previously described as a method to gain exceptional stability in patients with Charcot ankle fracture who had unbraceable deformity and severe instability of the ankle.1 This fixation construct has been found to be biomechanically superior to an intramedullary rod for this type of fusion.2
Myerson et al4 have previously described the use of femoral head grafts through an anterior approach to fill large defects of the talar body. They have found them useful for filling large defects and avoiding severe limb shortening.
REFERENCES
1. Alvarez RG, Barbour TM, Perkins TD. Tibiocalcaneal arthrodesis for nonbraceable ankle deformity. Foot Ankle Int 1994;15:354–359.
2. Chiodo CP, Acevedo JI, Sammarco VJ, et al. Intramedullary rod fixation compared with blade-plate-and-screw fixation for tibiocalcaneal arthrodesis: A biomechanical investigation. J Bone Joint Surg Am 2003;85A:2425–2428.
3. Den Hartog BD, Palmer DS. Femoral head allografts for large talar defects. Tech Foot Ankle Surg 2008;7:264–270.
4. Myerson MS, Alvarez RG, Lam PW. Tibiocalcaneal arthrodesis for the management of severe ankle and hindfoot deformities. Foot Ankle Int 2000;21:643–650.