The neuropathic ankle joint presents a difficult problem for the orthopedic surgeon. The severe ankle and hindfoot deformities that occur as a result of neuropathy quite often fail non-operative brace treatment. These deformities can cause abnormal stresses on the skin, bones, and joints of the foot leading to ulcerations, cellulitis, osteomyelitis, stress fractures, and further pain and deformity.
Surgical procedures have been developed to address severe arthritis and deformity of the tibiotalar and subtalar joints. Tibiotalocalcaneal arthrodesis can be performed to address tibiotalar and subtalar joints. However, if the talus has been deemed unsalvageable, a tibiocalcaneal arthrodesis may be the only option. This is often the case in patients with post-traumatic osteonecrosis of the talus, in which the talus has been extruded or gone on to significant collapse. Infection and neuropathic changes can also cause a talus to be fragmented and deficient.
Diabetic neuropathy is a common cause of severe ankle and hindfoot deformity resulting in talar collapse and resorption. Other causes of Charcot arthropathy include tabes dorsalis, syringomyelia, alcoholic neuropathy, Charcot-Marie-Tooth disease, and other peripheral nerve lesions. Other mechanisms for talar fragmentation and resorption include inflammatory arthritis and post-traumatic arthritis with talar osteonecrosis.
The most commonly used classification for stages of Charcot joints is the Eichenholtz classification.
- Stage 0 shows clinical signs of swelling, warmth, and pain; however, normal x-rays though MRI may show bone edema.
- Stage 1 is the “fragmentation” stage, where x-ray reveals fragmentation, resorptions, fractures, or dislocations.
- Stage 2 is the “coalescence” stage, where there is fracture healing, new bone formation, sclerosis, and signs of a reparative process. Clinical signs and symptoms may still be present but are improved.
- Stage 3 is the “consolidation” stage, where the joint is healing but is remodeled and often heals enlarged and deformed. Radiographs reveal sclerosis and remodeling, and the patient is often healed in the new fixed deformity.
- Salvage procedure for non-braceable deformity
- Patient non-compliant
- Peripheral vascular compromise
- Uncontrolled diabetes
- Deep abscess/osteomyelitis
Prior to surgical treatment, a full workup for infection should be done, especially if the reason for surgery is post-traumatic and post-surgical arthritis or osteonecrosis. Fragmentation and resorption of the talus can have the appearance of infection and osteomyelitis on x-ray. If the patient has diabetes, then a work up for healing potential is beneficial, including either transcutaneous oxygen index or toe-level Doppler index. The patient must be informed of the need for strict weight-bearing restrictions and expectations prior to surgery.
- Laterally, on a bean bag
- Axillary roll
- Ensure that AP, lateral, and axial images can be obtained during the procedure
- AO pediatric 40-mm condylar blade plate (Figure 1)
- AO large instrumentation set with pediatric chisel
- AO tension device
- 7.3-mm AO cannulated screw set
- Bone mill
- Image intensifier
- Vancomycin and tobramycin powder
Figure 1. Pediatric AO blade plate
Operative Treatment (Authors' Preferred Approach)
A lateral curvilinear incision is drawn out on the patient (Figure 2). A tourniquet is used, and a Strayer gastrocnemeus lengthening is often performed first. A curvilinear incision is made over the distal one fourth of the fibula down to the calcaneus. Often with neuropathic patients, the sural nerve will be non-functional and may be transected with the peroneal tendons and the distal 10-14 cm of the fibula, which can be used as bone graft later in the case.
Figure 2. Curvilinear lateral incision
The remnants of the talar body are removed while preserving the talar head and neck. All articular surfaces are denuded including the tibial plafond, medial malleolus, and calcaneus. Multiple small drill holes are made in the denuded areas to stimulate bleeding and growth factors for bony healing. The resected fibula or iliac crest autograft is mixed with cancellous allograft chips, as well as tobramycin and vancomycin powder. This bone graft combination is then placed between the calcaneus and the tibia to assist with bony fusion.
Kirshner wires can be used to hold the reduction with the foot plantigrade and the hindfoot in 5 degrees of valgus and 5-10 degrees of external rotation (Figure 3). An appropriate-length, fixed-angle blade plate is used to stabilize the tibia to the calcaneus, such as an AO pediatric condylar 95-degree blade plate (Figure 4). The blade should be placed at the junction of the lower and middle thirds of the lateral calcaneus.
Figure 3. Placement of pin for 7.3-mm cannulated screw
Figure 4. Placement of pediatric AO blade plate
Once the blade has been seated, an AO tensioning device can be used to add compression (Figures 5, 6). Prior to placing 4.5-mm cortical screws into the tibia in the proximal portion of the plate, cancellous screws may be used distally in the tibial metaphyseal bone.
Figure 5. Placement of AO tension device for compression through blade plate
Figure 6. AO tension device in place, providing compression
In addition to the blade plate fixation, several 6.5- or 7.3-mm cannulated, partially threaded screws can be used outside the plate for added stability. One is often placed from the anterolateral tibia aimed distal and posterior into the calcaneus (Figure 7). Another screw from the posterior tibia can be aimed distally and anteriorly into the talar head that is resting anteriorly on the tibia (Figure 3).
Figure 7. Placement of second 7.3-mm cannulated screw from anterior tibia to calcaneus
Fluoroscopic guidance should be used to ensure appropriate alignment of the foot, as well as final hardware position (Figures 8-9).
Figure 8. Lateral view, position of hardware for tibiocalcaneal fusion
Figure 9. Posterior view, position of hardware for tibiocalcaneal fusion
Pearls and Pitfalls
- Make sure the patient is willing to commit to/comply with 5-8 months of non-weight-bearing and post-operative recommendations.
- The pre-operative workup is critical to ensure the patient has adequate circulation to heal the procedure.
- Ensure proper foot position relative to the tibia (varus/valgus, avoid excessive anterior translation of the foot).
- Once union has occurred, the anterior shell of the bivalved AFO helps prevent the moment force of the tibia over the foot to decrease the risk of tibial stress fracture.
- Most patients have multiple medical co-morbidities and are admitted for several days after surgery for therapy and medical management.
- The cast and dressing are changed prior to discharge home.
- The cast is changed at 2-4 week intervals until fusion is acquired, often up to 3-6 months.
- Once out of the cast, a custom-molded AFO is used while weight-bearing is initiated to help offset stresses to the midfoot.
- 93% fusion at an average of 16 weeks
- Bivalved AFO for life helps decrease the risk of tibial stress fractures
- Hardware failure
- Tibial stress fractures
Alvarez RG, Barbour TK, Perkins TD. Tibiocalcaneal arthrodesis for non-braceable neuropathic ankle deformity. Foot Ankle. 1994;15:354-359.
Alvarez R, Gaines D, Easley ME. Tibiocalcaneal Arthrodesis Using Blade Plate Fixation. Operative Techniques in Orthopaedic Surgery. 2011. Lippincott Williams & Wilkins. Philadelphia, PA. Ch 83; 4179-4190