Use of ring fixator in staged primary total ankle arthroplasty

Tibial Plafond fractures are severe bony injuries within a tenuous soft tissue envelope. The incidence of post-traumatic osteoarthritis is high for intra-articular fractures, such as fractures of the tibial plafond fractures, which are associated with 70–75% of PTOA. The patient that develops PTOA of the ankle is on average 9 years younger than that who develops OA. These patients tend to be in their working years and the toll of the disability is great with respect to their well-being and quality of life. A reconstructive option that restores motion and offers pain relief for PTOA is often attractive.

This case study follows a 57 year old woman with a tibial plafond fracture that was initially treated with open reduction and internal fixation of both the tibia and fibula. Due to the development of stiffness and pain, the patient subsequently underwent hardware removal, distraction arthroplasty, and definitive treatment with TAR. Distraction arthroplasty has been part of the armamentarium of treatment of ankle arthritis but has been used as a definitive treatment to avoid or delay arthrodesis or arthroplasty.^, To our knowledge, there are no reports in the literature describing the use of a ring fixator as a means of distracting the joint space to correct the shortening of the tibia due to bone loss from necrosis and to gradually stretch the soft tissue envelope.

A 57 year old woman with a history of multiple sclerosis and hypertension presented to us 14 months after operative repair of a tibial plafond fracture sustained by a low energy twisting mechanism. She was treated with open reduction and internal fixation of both the tibia and fibula. After the surgery she developed stiffness and pain. She had a trial of physical therapy, image guided corticosteroid injection and cheilectomy and partial hardware removal to try to alleviate her symptoms. She had an anterior and lateral skin incision that was well healed with no signs of infection. Ankle motion was 10 degrees of dorsiflexion and 10 degrees of plantarflexion. Deep peroneal and Posterior tibial pulses were 2+ and sensation and motor function was intact throughout the foot. Injury CT scans demonstrated an OTA 43-C3 articular multifragmentary distal tibial fracture (Fig. 1A). Three views of the ankle were taken at the time of consultation and demonstrated a precontoured anterior tibial plate, a fibular plate and joint space narrowing of the tibiotalar joint with osteophyte formation (Fig. 1B). Radiographs showed that she had developed advanced degenerative changes in a little over a year after the index procedure. She was offered a carbon fiber dynamic ankle foot orthosis which she tried but tolerated poorly. She was offered fusion as well as total ankle replacement as treatment options and she indicated that she would proceed with a two stage procedure first to remove hardware and then follow with TAR. Shortly thereafter, the first COVID-19 “Stay at Home” orders were issued for the state of Washington and the patient was lost to follow up for several months.

Upon return to the clinic 6 months later she expressed that she still wanted to proceed with HWR and TAR. She subsequently underwent HWR. Once the obstructing hardware was removed the clinical challenges of her condition were more apparent. Three views of the ankle demonstrated varus ankle arthritis, 2 views of the tibia demonstrated neutral tibial alignment and long leg views demonstrated shortening of the right lower extremity compared to the left. Of greatest concern was the shortening of the soft tissue envelope around the ankle (Fig. 1C and D). Weightbearing CT scan demonstrated healing of the metaphyseal segment (Fig. 1E). Shortening the limb at the time of TAR to accommodate the soft tissues would require at least a centimeter of tibial shortening compared to the contralateral side. This would compromise the fixation of the tibial implant by placing it in less dense tibial bone and would lead to gait disturbance and potentially be a source of dissatisfaction. Conversely, restoring the length of the tibia acutely during TAR would cause significant tension on the soft tissue envelope, creating the risk of wound complications and infection. After much consideration, the decision was made to gradually restore the length of the tibia with a circular fine wire external fixator that would also stretch the soft tissues.

The patient underwent placement of a circular external fixator. The fixator was sized to her in the office setting and autoclaved for sterilization at the time of surgery. Hydroxyapaptite coated half pins were placed into the tibia and calcaneus and fine wires were passed into the talus. The talus was brought posterior and distal into its anatomic location and postoperative radiographs demonstrated the extent of shortening and anterior tibial bone loss that had taken place (Fig. 1F). The patient was seen for her routine postoperative visit two weeks later. At that time the fine wire in the talus was removed to minimize external contamination of the ankle joint and to allow for epithelialization of the pin tract. The definitive total ankle replacement was scheduled for 3 weeks after placement of the fixator.

At the time of her total ankle replacement surgery the patient underwent general anesthesia with a regional block. She was placed in the supine position with a bump under the ipsilateral hip. The entire circular fixator was prepped with betadine paint and scrub. With the ankle held out to length with the fixator two pins one medial and one lateral were placed into the talus to maintain its length and relationship to the tibia (Fig. 1G). At that point the fixator was removed, a new extremity drape was placed, gloves were exchanged and the leg was reprepped. A standard anterior approach to the ankle was made and conventional instruments and a leg holder were used to implant an Inbone II total ankle replacement. A stemmed component was used to get diaphyseal fixation as the distal tibial bone was found to be necrosed and sclerotic. A minimal skim cut was made anteriorly to preserve as much tibial bone stock as possible (Fig. 1H). A three stem tower with a standard tibial base plate was placed into the tibia. The talus preparation was routine. A superficial and deep deltoid ligament release was necessary to balance the ankle (Fig. 1I). The final TAR had 10 degrees of dorsiflexion and 25 degrees of plantar flexion in the operating room. Postoperatively she had a routine course with uneventful wound healing and progression to full weightbearing at eight weeks.

Tibial Plafond fractures are severe bony injuries within a tenuous soft tissue envelope. Patient Reported Outcomes Measurement System Physical Function (PROMIS PF) and Foot and Ankle Ability Measure (FAAM) are much lower than the general population after ORIF of these injuries and the rate of post traumatic arthritis can be as high as 39%.^, The utilization of total ankle arthroplasty has increased due to a decrease in near term revisions of the implants and an improvement in patient reported outcomes compared to ankle arthrodesis. It is likely that many patients who develop PTOA after plafond fractures will request total ankle arthroplasty over arthrodesis for pain relief.

PTOA of the ankle is the main cause of degenerative joint disease of the ankle at 76% with primary OA being in the minority at 9%. A reconstructive option that restores motion and offers pain relief is often attractive and the clinical outcomes of TAR performed for PTOA secondary to pilon fractures are similar to those of patients who underwent TAR for other indications. The challenges of reconstruction with TAR are demonstrated in this case report. The extensive hardware used to fixate plafond injuries interferes with the intraoperative fluoroscopy necessary to align cutting guides. Even with patient specific instrumentation the hardware at the joint line interferes with the seating of the actual tibial component. These patients therefore require a two stage procedure which further stresses a traumatized non-native soft tissue envelope around the ankle.

Placement of the circular fixator at the time of hardware removal is a consideration but prolonged presence of external fixator pins is a concern for infection especially in the setting of total ankle arthroplasty. The rate of superficial pin tract infection from the limb lengthening literature has been reported at 78% for half pins and 33% for fine wires. For this purpose we attempted to minimize the amount of time in the frame, and the patient was given prophylactic oral antibiotics for five days both after the fixator placement and the total ankle replacement. The use of routine prophylactic oral antibiotics after total knee arthroplasty in a high risk patient population has been recommended, and in this instance we felt the benefits of their use outweighed the risks.

The use of a circular external fixator to correct ankle alignment, restore the tibiotalar joint space and stretch the soft tissues prior to TAR is a viable treatment option in patients who have loss of tibial length and angular deformity from PTOA after tibial plafond fracture. The patient must be counseled on the long clinical course and the need for multiple procedures, including hardware removal, placement of the fixator and finally, definitive TAR. Without having the benefit of literature specific to this topic we recommend the use of prophylactic oral antibiotics after fixator placement and total ankle arthroplasty.

Complete written informed consent was obtained from the patient for the publication of this study and accompanying images.