Various options exist for the surgical treatment of ankle osteoarthritis. Selection of the optimal treatment requires a thorough consideration of the patient’s characteristics. In patients with progressive or end-stage ankle osteoarthritis, total ankle arthroplasty is indicated for cases with bilateral involvement or degeneration in the adjacent joints. However, total ankle arthroplasty is contraindicated in patients with infectious ankle osteoarthritis or severe deformities (≥15° varus and valgus deformity of the ankle joint); it is also not appropriate for patients with a high level of physical activity (including sports and farming), even if they are ≥60 years of age . Although ankle arthrodesis shows stable long-term outcomes and is effective in reducing pain, it has certain disadvantages including a loss in the ankle ROM and adjacent joint disorders. Furthermore, in countries such as Japan where people do not wear shoes and tend to sit on the floor in the house, patient satisfaction with ankle arthroplasty is relatively low [7, 9].LTO includes valgus correction of the alignment and an outward shift of the weight-bearing line. The procedure has been reported to have good outcomes in patients with stage I-IIIA ankle osteoarthritis. However, LTO, which involves extra-articular osteotomy, is contraindicated in patients with ankle joint instability and may require additional surgery, such as ligament reconstruction [1, 19, 20].
Distraction arthroplasty includes cell mobilization from the bone marrow in the talus and tibial mortise (via a microfracture procedure or drilling), and requires treated patients to perform articulation while wearing an external fixator, allowing for an increased ROM. Joint traction for an appropriate period of time prevents damage to the regenerated tissue, and articulation promotes its maturation [18, 21].
In this study, we combined DTO and distraction arthroplasty. DTO has been shown to be effective in older patients with a high level of physical activity, as it preserves the ROM [22, 23]. In a study, DTO was successfully performed in patients with stage IIIB arthropathy and ankle joint instability. DTO offers certain advantages over arthrodesis, which include preservation of joint function and pain reduction. Another merit is that it exerts less influence on peripheral joints, which often cause problems in fixation. Hence, none of the patients in the present study had an adjacent joint disorder.
Deliberate flexion of the osteotomy serves to stabilize and provide more coverage to the talus. Since most patients with ankle osteoarthritis lack dorsiflexion, many surgeons are hesitant to flex the osteotomy and increase equinus. However, we overcame this issue by employing transverse Vulpius gastrocsoleus recession for increased equinus, which provided better coverage of the talus and shifted the healthier posterior cartilage anteriorly. This approach may have contributed to the observed good results.
The advantage of DTO over LTO is that it improves ankle joint stability by an angled osteotomy of the proximal tibial attachment site of the anterior tibiofibular ligament with valgus correction . Without fibular osteotomy, DTO is similar to LTO with fibular osteotomy, in that they both correct alignments. Both osteotomies may shift the weight-bearing axis laterally by angulation of the osteotomized distal part of the tibia. However, only DTO without fibular osteotomy can narrow the lateral mortise in cases of medial ankle arthritis with mortise widening . Therefore, DTO with joint distraction using a circular external fixator may also be beneficial to the cartilage [10, 24].
There are numerous reports on supramalleolar osteotomy with or without fibular osteotomy for varus ankle arthritis. Hongmou et al.  reported that fibular osteotomy may be necessary in supramalleolar osteotomy cases with a large talar tilt and small tibiocrural angles. Stufkens et al.  also reported that only supramalleolar osteotomy with fibular osteotomy shifts the pressure laterally for varus ankle arthritis. However, further research is required on this subject.
Since long-term non-weight-bearing leads to reduced walking ability in older patients, walking with a circular external fixator with strong fixation immediately after surgery may greatly benefit them and mechanical stimulation by weight-bearing may have additional effects. Conversely, DTO using a plate requires 1 to 2 months of non-weight-bearing [22, 23]. Caution is required with higher degrees of correction as it places a greater burden on soft tissues.
In our study, the evaluation of joint space narrowing on pre- and postoperative radiographs permitted the visualization of postoperative improvements with our technique (Figure 7). Furthermore, MRI evaluations confirmed the improvements, with reductions or disappearance of preoperative signal changes after surgery.
This study has certain limitations. First, patients may find the use of a circular external fixator uncomfortable. However, one of the major reasons explaining the absence of deep infections or soft tissue complications requiring additional surgery in this cohort, may be the avoidance of plate fixation. Additionally, improvement of talus instability without ligament reconstruction requires a relatively large opening (i.e., about 20 mm) at the osteotomy site in most patients; this substantially increases the tension on the medial soft tissue in most patients. Therefore, additional studies with a larger number of older patients with ankle osteoarthritis and a high level of physical activity, are needed to validate the suitability of DTO with distraction arthroplasty using a circular external fixator as a treatment option for end-stage ankle osteoarthritis.