Fibular osteotomy is helpful for talar reduction in the treatment of varus ankle osteoarthritis with supramalleolar osteotomy

Unlike the hip and knee, which are prone to developing primary osteoarthritis, the ankle develops arthritis usually because of a traumatic event, mainly ankle sprains. Lateral loosening and instability lead to medial stress concentration, and uneven pressure on the articular surface is closely related to cartilage degeneration, which may induce osteoarthritis changes and progress the development of degeneration [1‐3]. There is consensus on the use joint-sacrificing procedures, including total ankle replacement or ankle arthrodesis, for the treatment of painful end-stage ankle osteoarthritis [1, 4]. However, more than half of the tibiotalar joint surface is usually preserved in early and mid-stage ankle osteoarthritis, and treatment is challenging and controversial [5].

Supramalleolar osteotomy (SMOT) is an effective procedure for the treatment of non-end-stage asymmetric ankle osteoarthritis that was first introduced by Speed and Boyd in 1936 [6] and was popularized after Takakura’s report in 1995 [7]. Clinical and biomechanical studies have reported that SMOT can realign the weight-bearing axis, restore the congruence of the tibiotalar joint [8‐12], decrease the contact pressure of the medial malleolar joint [13, 14], and even reverse the stage of radiological ankle osteoarthritis [5, 7, 15]. However, the indications for this procedure are still controversial, and some patients have reached unsatisfactory outcomes.

The necessity of fibula osteotomy (FO) is one of the most controversial issues. Some authors have proposed the combination of SMOT and FO in all cases [7, 10, 15‐18], some have suggested that the entirety of the fibula should be reserved [8, 19‐21], and some have used FO depending on the conditions [5, 9, 12, 22, 23]. However, until now, the indications for FO have remained unclear. Thus, we hypothesize that FO may play a role in realignment surgery and may be helpful in restoring the congruence of the ankle joint. The purpose of the current study is to retrospectively analyze and compare the clinical and radiological outcomes of SMOT with or without FO for the treatment of varus ankle osteoarthritis.

The current study was approved by the research board of our hospital. The authors retrospectively studied the outcomes of SMOT with or without FO in the treatment of varus ankle osteoarthritis between January 2010 and January 2018. The inclusion criteria were as follows: (1) adults more than 18 years old; (2) tibial articular surface angle (TAS) less than 84 degrees; (3) varus ankle osteoarthritis; (4) clinical symptoms, such as pain with walking and limitations in daily and recreational activities; (5) treated with SMOT with or without FO; and (6) at least two years of follow-up. The exclusion criteria were as follows: patients with (1) neurological disorders; (2) rheumatoid arthritis; (3) Charcot arthropathy; (4) Charcot-Marry-Tooth deformity; (5) acute or chronic infections of the ankle joint; or (6) resurgery after SMOT failure.

Finally, 39 patients in the SMOT group and 24 patients in the SMOT with FO group were enrolled in the study. There were 19 males and 44 females, and the mean age was 55.7 ± 9.4 (range, 23–77) years. According to the modified Takakura ankle osteoarthritis stage, there were 9 stage 2, 25 stage 3a, 27 stage 3b and 2 stage 4 patients. The basic information of the included patients is listed in Table 1, and no significant differences were found with the numbers available.

Realignment surgery, which is based on the theory that uneven pressure on the articular surface of the lower extremities may induce degeneration [3], is used to redistribute the joint weight-bearing pressure to delay the progression of osteoarthritis. The midterm results of SMOT showed good outcomes for pain relief, functional improvements, and returning to sports and recreation activities [7‐12, 15‐19, 21, 23, 27, 28]. However, SMOT is still controversial, the indications for this procedure are still unclear, and the evidence is limited.

When the SMOT procedure was used for varus ankle osteoarthritis, the necessity of FO was debated. Takakura and Tanaka performed FO first before the SMOT procedure in all cases [7, 15]. Stamatis et al. [18] also performed FO first and at the same level as the tibial osteotomy level without any internal fixation. These earlier studies used tibial osteotomy at the level proximal to the level of syndesmosis; while tibial osteotomy was gradually carried out, the distal part of the tibia was rotated with the lateral cortex of the tibia as the center of rotation. In this case, syndesmosis may impact and prevent the rotation, and FO may be a necessary procedure to facilitate the medial opening of the tibia. Ahn et al. [8] reported distal tibial oblique osteotomy without FO to constrict the ankle mortise and to achieve a lateral shift of the weight-bearing center of the talus. His tibial osteotomy line was on the lateral tibial cortex 5 mm proximal to the joint and distal to the syndesmosis to avoid syndesmosis impingement. However, in his cases, talar tilt was not corrected. In our patients treated with SMOT and FO, talar tilt was better corrected than in those without FO (Fig. 5). This result suggests that the fibula plays a role in hindering the reduction in the talus. Biomechanical studies have reported that creating a supramalleolar valgus deformity does not cause a shift in contact toward the lateral side of the tibiotalar joint, and the restrictive role of the fibula is revealed during osteotomy [13, 14]. According to current results, the weight-bearing center of the talus was better reduced in the SMOT with FO group (P = 0.006). In current study, we used lateral closing wedge or Z-shaped FO at the same level to the tibial osteotomy. Although the osteotomy methods were different, they played the same roles to relieve the lateral stress and allowed the distal tibial to rotate centered on the lateral cortex when the osteotomy site was opened.

In SMOT without FO, the ankle mortise may be narrowed. As the talus dome has an anatomy of a wide anterior and narrow posterior, dorsiflexion of the ankle joint may be limited after the SMOT procedure. Pagenstert et al. [23] reported that the improvement of pain was correlated with walking ability and general activity but was not correlated with the achieved ROM. Nüesch et al. [11] reported that after SMOT, patients walked more slowly, had a smaller sagittal range of motion in their affected leg, and had lower peak ankle dorsiflexion; however, they observed no difference in the quality-of-life score compared with the healthy controls. According to the current results, the ROM in SMOT decreased postoperation, although the decreased ROM was not reported to influence the physical activity of the SMOT patients. Long-term weight bearing and dorsiflexion may concentrate the stress on syndesmosis and widen the distal tibiofibular syndesmosis (Fig. 6). This narrowing of the mortise may lead to lateral malleolar impingement during weight bearing and walking and may induce pain symptoms. In our cases without FO, seven patients experienced failure: three patients with ankle arthrodesis and four patients who made an appointment for fibular osteotomy.

There are limitations in this study. First, the retrospective design led to some differences between the two groups, and there were more patients in the SMOT group. However, other basic information was not significantly different between the two groups, which makes the results of the two groups comparable. Second, there were some additional procedures, such as modified Brostrom procedure or calcaneal osteotomy, that might affect the final outcomes of SMOT. However, there was no significant difference in the proportion of additional procedures between the two groups (Table 1). The third limitation is that the follow-up period was short, with a mean time of 46 months. Although the outcomes will change over time, our early results confirm that the functional outcome of SMOT is good in terms of pain relief, correction of malalignment, and a reduction in symptoms for varus ankle osteoarthritis patients. Moreover, if SMOT is combined with the use of FO, talar tilt and medial displacement can be better corrected.

In conclusion, SMOT is a promising procedure for functional improvement and malalignment correction in varus ankle osteoarthritis, but it reduces ankle range of motion. If SMOT is combined with FO, talar tilt and medial displacement can be better reduced. However, well-designed prospective comparative studies are still needed to further clarify the necessity of FO, while SMOT is used for the treatment of varus ankle osteoarthritis.