There are various options for the surgical treatment of ankle osteoarthritis. The optimal treatment should be selected with a thorough consideration of the patient’s characteristics. Total ankle arthroplasty for patients with progressive or end-stage ankle osteoarthritis is well indicated for bilateral patients and patients with degeneration in the adjacent joints. However, total ankle arthroplasty is contraindicated for patients with infectious ankle osteoarthritis or a severe deformity (≥15° varus and valgus deformity of the ankle joint). In addition, total ankle arthroplasty is not appropriate for patients with a high level of physical activity (e.g., sports and farming), even if they are ≥60 years of age [18]. Although ankle arthrodesis shows stable long-term outcomes and is effective in reducing pain, it has disadvantages, such as a loss in the ankle ROM and adjacent joint disorders. Furthermore, in countries such as Japan, where people do not wear shoes and 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, with good outcomes reported in patients with stage I-IIIA ankle osteoarthritis. However, LTO, which is an extra-articular osteotomy surgery, is contraindicated for 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 patients treated with joint distraction 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 maturation of the regenerated tissue [18, 21]. In the present study, we combined DTO and distraction arthroplasty. DTO has been shown to be effective in older patients with a high physical activity level because the treatment preserves the ROM [22, 23]. There is also a study in which DTO was successfully performed in patients with stage IIIB arthropathy and ankle joint instability. The merits of DTO, relative to arthrodesis, are that it preserves joint function and reduces pain. Another merit of DTO is that it has less influence on peripheral joints, which often cause problems in fixation. None of the patients in the present study had an adjacent joint disorder.
Deliberate flexion of the osteotomy serves to stabilize the talus and provide more coverage to the talus. Because most patients with ankle osteoarthritis lack dorsiflexion, many surgeons are hesitant to flex the osteotomy and create more equinus. However, we have overcome this issue by using the transverse Vulpius gastrocsoleus recession for equinus. The end result provides better coverage of the talus and shifts the better posterior cartilage anteriorly. This approach may have contributed to the observed good results.
The merit of DTO, relative to LTO, is that it improves ankle joint stability by an angled osteotomy of the proximal tibial attachment site of the anterior tibiofibular ligament and valgus correction [23]. DTO without fibular osteotomy is similar to LTO with fibular osteotomy in that they both correct alignment. Both osteotomies can 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 medial ankle arthritis with mortise widening [22]. DTO with joint distraction using a circular external fixator may also be beneficial to cartilage [10, 24].
Currently, there are various discussions regarding supramalleolar osteotomy with or without fibular osteotomy for varus ankle arthritis. Hongmou et al. [25] reported that fibular osteotomy may be necessary in supramalleolar osteotomy cases with a large talar tilt and small tibiocrural angles. Stufkens et al. [26] reported that only supramalleolar osteotomy with fibular osteotomy shifts the pressure laterally for varus ankle arthritis. Further research is needed.
Because 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 the patients. In addition, mechanical stimulation by weight-bearing may have additional effects. On the other hand, DTO using a plate requires 1 to 2 months of non-weight-bearing [22, 23].Furthermore, caution is required when the amount of correction is high due to a high burden on soft tissue.
By evaluating joint space narrowing on pre- and postoperative X-ray, it was possible to visualize postoperative improvements with our technique (Figure 7). Furthermore, the MRI evaluations confirmed the improvements, with preoperative signal changes reduced or disappeared after surgery.
This study has some limitations. First, patients may find the use of a circular external fixator uncomfortable. However, one of the major reasons that none of the patients in the present study had a deep infection or soft tissue problem requiring additional surgery may be the avoidance of plate fixation. Additionally, in most patients, improvement of talus instability without ligament reconstruction requires a relatively large opening (i.e., about 20 mm) at the osteotomy site, which, for the medial ankle, substantially increases the tension of the medial soft tissue. Additional studies, with a larger number of older patients with ankle osteoarthritis and a high physical activity level, are needed to confirm DTO with distraction arthroplasty using a circular external fixator as a treatment option.