Supramalleolar osteotomy combined with lateral ligament reconstruction and talofibular immobilization for varus ankle osteoarthritis with excessive talar tilt angle

Ankle osteoarthritis (OA) can be manifested as varus, valgus, or neutral alignment, in which varus accounts for approximately 52% of the cases [1, 2]. Abnormal alignment often leads to progressive aggravation of ankle osteoarthritis, which gradually progresses to end-stage ankle arthritis. At present, ankle fusion or arthroplasty is the main method for treating end-stage ankle arthritis. However, the former causes loss of ankle motion and the possibility of subsequent adjacent joint degeneration, and the latter may be difficult to perform in patients with preoperative ankle stiffness, high demand for postoperative exercise, osteoporosis, and so on [3, 4]. Therefore, it is of great significance to prevent the progression of moderate ankle arthritis to end-stage arthritis.

A deformation apex of varus ankle arthritis (the center of rotation of angulation, CORA) may peak at the distal tibia, tibia-talus joint, subtalar joint, or at the calcaneus. As the main joint-preserving surgery, supramalleolar osteotomy can adjust the alignment of the tibia and talus and normalize the stress distribution on the ankle joint surface, thus preventing degeneration of the joint; this technique is increasingly widely used [5‐8]. Although traditional supramalleolar osteotomy has been reported to be effective [9‐13], clinical and radiographic results showed that varus ankle arthritis with an excessive talar tilt angle (TTA) could not be treated effectively. Most authors considered this technique to be ineffective in correcting the TTA if the preoperative TTA was greater than 10° [10] or 7.3° [12]. Lee [14] designed a modified supramalleolar osteotomy in response to the problem. However, Ahn et al. [1] found that Lee’s osteotomy technique could improve most radiographic parameters satisfactorily, while there was no significant improvement in TTA.

Chronic lateral instability of the ankle (CLIA) can cause varus tilt of the talus and is considered to be the most common cause of varus ankle OA [2, 5]. In the treatment of varus ankle arthritis, lateral ligament reconstruction is performed with poor improvements to the TTA [8, 12]. We hypothesized that after lateral ligament reconstruction in supramalleolar osteotomy for the treatment of varus ankle arthritis, immobilization with Kirschner wires for 6 weeks to maintain accurate matching of the talus in the ankle mortise can correct the excessive TTA and achieve a favorable outcome. We investigated the results of this technique for the treatment of varus ankle arthritis with an excessive TTA.

For the group as a whole, the mean follow-up time was 32.2 months (range, 24–40 months). At the last follow-up, the AOFAS score improved significantly from 45.8 ± 2.1 (range, 35–60 points) preoperatively to 84.8 ± 1.8 (range, 66–96 points) (p < 0.001), and the VAS score decreased from 4.9 ± 0.4 (range, 2–8 points) to 1.1 ± 0.2 (range, 0–2 points) (p < 0.001).

By radiological evaluations, the MDTA, TTA, and HMAVs changed from 80.9° ± 0.4° (range, 78–83°) to 90.1° ± 0.4° (range, 86–93°), 11.7° ± 0.6° (range, 8–17°) to 1.4° ± 0.3° (range, 0–3°), and 12.6 mm ± 0.8 mm (range, 8–18 mm) to 4.2 mm ± 0.6 mm (range, 0–10 mm), respectively (each p < 0.001). The ADTA changed from 82.1° ± 0.3° (range, 80–84°) to 82.5° ± 0.3° (range, 80–85°), and there was no statistical significance (p = 0.370) (Table 1).

All patients achieved bone healing in an average of 3.3 months (range, 3–6 months). The arthritis staging improved in 11 cases (65%); 2 cases improved from stage 2 to stage 1, 7 cases from stage 3a to stage 2, and 2 cases from stage 3b to stage 3a. No change was observed in 6 cases, and there were no aggravated cases (Table 2).

Intramuscular vein thrombosis of the lower limbs occurred in 1 patient 1 week after surgery, and superficial infection occurred in 1 patient. No cases of bone nonunion, delayed union, or subsequent ankle fusion were observed during the follow-up.

The following parameters are significant in the evaluation of varus ankle arthritis deformities. The first parameter is MDTA. The MDTA is applied to assess the varus deformity of the distal tibia, and it varies by region. Hintermann et al. [15] reported the normal MDTA of Europeans ranged from 91 to 93°, while Monji [20] reported the mean value of Japanese was 87.7 to 89.0°. According to a biomechanical study conducted by Stufkens et al. [21], when the lateral malleolus was intact, there was no significant increase in pressure on the lateral half of the tibial talus joint when the axial load was applied after the tibial osteotomy. However, once the lateral malleolus was cut, the pressure on the lateral half of the tibial talus joint increased significantly. This suggests the necessity of considering lateral malleolus osteotomy in supramalleolar osteotomy for patients with lateral malleolus obstruction. A decreased MDTA results in varus deformity above the ankle, high pressure in the medial ankle, accelerated cartilage degeneration, and narrowed medial joint space [15]. The optimal correction with distal tibia osteotomy is a 2–4° slight overcorrection of the MDTA [20] or a correction in reference to the normal contralateral limb. With supramalleolar osteotomy, the varus deformity was effectively corrected proximal to the tibial talus joint, leading to restoration of the talar center on the axis of the tibia and dispersion of the stress on the ankle joint surface [22, 23]. In this study, the mean MDTA improved approximately 10° after the operation and was considered to be the most important reason for postoperative functional improvement.

The second parameter is TTA. The TTA is applied to assess the varus deformity of the talus on the coronal plane. An excessive TTA is often cited as one of the relative contraindications to supramalleolar osteotomy. Tanaka Y et al. [12] considered a TTA exceeding 7.3° to be a negative factor for a supramalleolar osteotomy, while Lee WC et al. [10] considered a TTA exceeding 10° to be a negative factor. A large TTA implies disability of the lateral ligament complex or an erosion of the medial malleolar subchondral bone (widening of the medial mortise space). A proper understanding of large TTAs is helpful in the formulation of targeted surgical procedures, such as arthroplasty [1, 24] for intra-articular deformity or lateral ankle ligament reconstruction [24, 25] for talar instability. It is meaningful that one of the inclusion criteria of our study was a preoperative TTA larger than 7.3°. The results showed that the TTA decreased significantly after surgery and was maintained effectively during the follow-up; this result was mainly attributed to the release of the deltoid ligament, the reconstruction of the lateral malleolar, and the fixation of the tibia and talus with Kirschner wires to maintain the reduction of the talus in the ankle mortise.

The third parameter is HMAVs [17]. The HMAV is applied to assess the varus deformity of the heel, and the average normal value is 1.6–3.2 mm [16] inside the tibial axis. The HMAV is more reliable than the tibial heel angle, which is affected by foot rotation [26]. A high HMAV in varus ankle arthritis indicates a varus deformity of the distal tibia, a decrease in the height of the medial half of the talus, or abnormal alignment of the talus and calcaneus. In rare cases, a high HMAV is also associated with varus deformity of the calcaneus body, which sometimes requires lateral sliding calcaneus osteotomy with or without a closing wedge [25]. In addition, when the talus is tilted, the calcaneus may compensate in the opposite direction, resulting in a z-shaped deformity [15]. In this situation, CT scans are recommended to identify the biplane deformity. In this study, the average HMAV changed from 12.6 mm before surgery to 4.2 mm after surgery. Although there was significant improvement, the HMAV still did not reach the normal range (1.6–3.2 mm) [17], which may be related to the coexistence of hidden subtalar joint varus or the uncorrected varus deformity of the calcaneus body.

In moderate to severe ankle osteoarthritis, approximately 60% of patients present talus varus or valgus, which may be related to talus instability [15, 27]. The stability of the talus depends on the finely matched bone structure and the healthy soft tissue around the talus, including the medial and lateral collateral ligaments, the ligaments between the talus and calcaneus, and the perimalleolar tendons. Instability of the talus can be caused by abnormal bone structure, such as erosion of the medial malleolus or dysfunction of related ligaments and tendons. In different stages, these abnormalities can exist alone or simultaneously and affect each other. A medial clear space greater than 3 mm is recommended as a predictor of widened ankle mortise on ankle stress radiographs, and a widened ankle mortise usually implies instability of the talus [1, 28].

Lateral instability of the ankle is considered to be an important cause of ankle osteoarthritis. Due to anatomical and biomechanical factors, ankle sprains are more likely to involve the lateral ligaments, which account for approximately 85% of all ankle sprains; this is consistent with the fact that varus ankle arthritis is more common than valgus ankle arthritis [1, 2, 25]. Relaxation of the anterior talofibular ligament leads to anterior displacement of the talus, which presents as ankle joint subdislocation on anterior stress views in severe cases, while a loose calcaneofibular ligament results in instability of the talus by varus stress, and the combination of the two results in a supination deformity of the talus. Lateral ankle instability can be caused by a single severe injury or multiple minor injuries, and the latter accounts for a higher proportion than the former [29]. The time course of the disease from ankle sprain to ankle joint instability to obvious osteoarthritis is approximately 20 years [30, 31], which suggests that the early treatment of lateral ankle ligament injuries should be emphasized to prevent chronic ankle joint instability and osteoarthritis. In this group, 15 patients had one or more previous obvious ankle sprains, which were believed to be related to the development of arthritis.

The correction of an excessive TTA is a difficult problem in ankle salvage surgery. Talar tilt is often accompanied by erosion of the media malleolus and widening of the medial gutter. Myerson and Zide recommend plafondplasty (intra-articular osteotomy) to narrow the mortise and reduce the TTA [32]. However, Lee believed that the procedure only corrected the medial half dome and may cause new intra-articular deformities; thus, they designed the distal tibial oblique osteotomy to correct the tilt of the entire tibial dome and to narrow the ankle mortise without damaging the joint surface and distal tibiofibular syndesmosis [14]. However, other authors considered that Lee’s technique was effective in correcting the width of ankle mortise but not effective when the TTA was too large [1].

The need for reconstruction of the lateral malleolar ligaments after distal tibial osteotomy is controversial. Lee et al. [25] and Mann et al. [24] believed that reconstruction was an essential adjunct to bony osteotomy and that the talus could be accurately stabilized in the ankle mortise. However, other authors believed that the abnormal stress within the ankle joint would be distributed after the realignment of the lower limbs, and ligament reconstruction was unnecessary [8, 9, 12]. We believe that if the treatment of ankle arthritis with a significantly increased TTA is not combined with reconstruction of the lateral ligament, the supination deformity of the talus would still exist, and the stress on the medial side of the ankle would remain too high while weight-bearing. The lateral ligament reconstruction technique (the modified Brostrom operation) used in this study is the gold standard for the treatment of CLIA; however, Lee et al. [25] showed that this technique was not effective when the TTA was too large. We considered this result to be due to the re-disability of the ligaments postoperatively. To avoid the re-relaxation of the reconstructed ligaments, we fixed the fibula and talus with two 2.0-mm Kirschner wires, immobilized the ankle joint with a short leg brace after surgery, and removed the Kirschner wires 6 weeks postoperatively. The mechanism is similar to the postoperative external fixator fixation mechanism after osteotomy introduced by Zhao et al. [33] but is more simple and minimally invasive.

Some limitations of the present study must be acknowledged. A small number of cases were included in our study, and there was no control group to confirm the positive effect of the 6-week postoperative tibia-talus fixation by Kirschner wires. In addition, the mean follow-up time was 32.2 months, but the range was large (24–40 months), which may have an impact on the efficacy results. Moreover, this study has not successfully analyzed the individual factors (high TTA, severity of arthritis preoperatively, age, etc.) that might be perhaps predictive of success or failure as a result of the sample size. Large-scale and long-term follow-up studies are needed to provide more convincing clinical data for the application of this technique.

Supramalleolar osteotomy combined with lateral ligament reconstruction and talofibular immobilization can effectively improve the load of the ankle in the treatment of varus ankle arthritis. As the talar tilt angle can be significantly improved and effectively maintained, this technique could be an alternative method for the treatment of varus ankle arthritis with an excessive TTA.