Supramalleolar Fornix Osteotomy Combined Fibular Segamental Resection for Varus Ankle Osteoarthritis

Background: To investigate the safety and clinical effect of supramalleolar fornix osteotomy combined with bular segmental resection in the treatment of varus ankle osteoarthritis (VAO). Methods: from July 2014 to July 2020, 38 patients with Takakura stage II - III VAO in Aliated Hospital of Chengdu University were retrospectively analyzed, including 31 males and 7 females, 21 left ankles and 17 right ankles. They were divided into open osteotomy group (21 cases) and fornix osteotomy group (17 cases). According to the American Society of foot and ankle surgery ankle and hindfoot score (AOFAS) and visual analogue scale (VAS) for pain function and pain score; weight-bearing ankle acupoints and lateral X-ray imaging evaluation. Results: 38 patients were followed up for 16-54 months (mean 41 months). The healing time of the supramalleolar osteotomy group (3.33 ± 0.90 months) was signicantly shorter than that of the open osteotomy group (6.09 ± 1.74 months) (t = -5.932, P = 0.000). The postoperative FAS score of fornix osteotomy group (85.65 ± 6.49) was signicantly better than that of open osteotomy group (63.05 ± 6.42), and the postoperative VAS score of fornix osteotomy group (2.12 ± 1.05) was signicantly better than that of open osteotomy group (4.38 ± 1.60) (P < 0.05). The improvement of anterior angle of distal tibia, talus inclination angle and talus lateral displacement in the fornix osteotomy group was signicantly better than that in the open osteotomy group (P < 0.05); the postoperative lateral angle of distal tibia in the fornix osteotomy group was 82.05 ± 1.74 ° on average, and that in the open osteotomy group was 80.17 ± 1.34 ° on average, with no signicant difference between the two groups (P > 0.05). Conclusion: The treatment of VAO with supramalleolar fornix osteotomy combined bular segamental resection can effectively solve the anterior and talus lesions. The deformity correction around CORA can avoid the lateral displacement of the talus and effectively reduce the incidence of postoperative ankle degeneration. Short term follow up convinced better function restoration compared with open supramalleolar osteotomy.


Introduction
Ankle arthritis (AOA) accounts for about 1% of all the people [1]. Talus varus or valgus tilt occurs in 60% of the patients after ankle trauma [2]. Ankle instability, intra-articular cartilage damage, iatrogenic fracture reduction and so on will lead to biomechanical and soft bone cell biological abnormalities of the ankle joint, and eventually degenerate to form AOA [3,4]. The onset of AOA is usually 12-15 years earlier than that of hip and knee joint, so the long-term effect is emphasized in the treatment [5]. Takakura et al. [6,7] reported that supramalleolar open osteotomy has achieved good results in the treatment of varus ankle osteoarthritis (VAO), which can improve the posterior foot line, relieve ankle pain and delay joint degeneration. However, in our clinical work, we found that there are some problems in the treatment of VAO with open supramalleolar osteotomy, such as insu cient treatment of medial and lateral degeneration of anterior malleolus and tibiotalar joints, talus lateral displacement caused by non rotation of angulation (Cora) correction, di culty in correcting talus tilt, and so on. Anterior supramalleolar fornix osteotomy combined with bular segmental resection can effectively deal with the tibiotalar joint lesions and correct the deformity around Cora with satisfactory clinical effect. In order to determine the safety and clinical effect of supramalleolar fornix osteotomy combined with bular segmental resection in the treatment of VAO, 35 patients with VAO treated by supramalleolar open osteotomy and fornix osteotomy in the A liated Hospital of Chengdu University were compared and analyzed. Methods 1.1 general data: retrospective analysis of patients with VAO who received osteotomy and orthopedic treatment in A liated Hospital of Chengdu University from July 2014 to July 2020. Inclusive criteria: 45-65 years old, varus ankle arthritis, anterior tibial angle (TAS) ≤ 85 °, Takakura classi cation stage II-III [6], tibiotalar articular cartilage preservation > 50%, simple coronal varus deformity, supramalleolar opening or fornix osteotomy correction. Exclusion criteria [8]: Previous peri ankle fracture or deformity surgery history, severe medial ankle wear requiring intra-articular osteotomy, Takakura stage IV ankle arthritis, posterior foot instability unable to recover through ligament reconstruction, genu derived ankle varus, peri ankle infection, severe vascular and neurological diseases, Charcot osteoarthritis.
Thirty eight patients were included in this study, including 31 males and 7 females, 21 left ankles and 17 right ankles. According to the osteotomy methods, they were divided into two groups: fornix osteotomy (FOT) group (n = 17, male 14, female 3, mean age 60.59); open osteotomies (OOT) group (n = 21, male 17, female 4, mean age 60.86). The general information of the two groups is shown in Table 1. There is no signi cant difference in gender composition, age, height and body mass index, anterior ankle osteophyte and other general information between the two groups (P > 0.05). (2) Imaging examination: preoperative X-ray examination includes the full length of double lower limb weight, ankle weight positive side position, rear foot weight long axis (long axial view radiographs) (10); Clinical determination of ankle arthritis malformation site, type, CORA position, back foot force line, external ankle ligament relaxation degree after determining the surgical program.  ankle front side position, rear foot long axis X-ray perspective to determine the force line, generally maintain with the bone outside the turn of 5 degrees, the outer end of the shin bone joint surface turned 3 degrees by the inner ankle front and rear mound into the knuckle needle temporary xation, bone cut gap > 10mm lled with allogeneic bone implants, placement of the inner anatomy locked steel plate (High, Shandong). After the internal xation is completed, the ankle roll-over and front drawer experiments, such as external ankle instability, are reinforced with improved Brostrom rivet repair techniques. Open osteotomy group patients did not do bula osteotomy, do not place drainage, stitch the wound, thick dressing covering the wound, elastic bandages pressurized bandage.
(2) Fornix osteotomy group ( Postoperative treatment: anesthesia wakes up immediately after the beginning of lower limb muscle contraction exercises, limb elevation promotes swelling and subsidence, encourages ankle stretching activity, drug anticoagulant prevention of deep vein thrombosis, open bone osteotomy 6 weeks after surgery, fornix osteotomy 2 weeks after the start of partial weight-taking activities, X-ray review prompts bone osteotomy after the start of full weight activity and gait exercise. 1.3 clinical follow-up: Monthly outpatient review and record the American Orthopedic foot and ankle score (FAS) ankle and hindfoot score [15]. Three months after the operation, the weight-bearing ankle acupoints and lateral X-ray examination were performed. I. X-ray measurement indexes of ankle acupoints: (1) tibial anterior surface angle (TAS): the angle between the distal articular surface of tibia and the medial side of tibial mechanical axis [16]. (2)

Discussion
Different from primary osteoarthritis of hip and knee, AOA is mainly caused by trauma [18]. Saltzman et al. [18] pointed out that 70% of advanced AOA were traumatic, including 37.0% of ankle fractures and 28.3% of ankle sprains. Stufkens et al. [19] systematic analysis showed that 60% of patients developed traumatic arthritis in the long term after ankle trauma; ankle fusion or joint replacement surgery is usually required for advanced ankle arthritis [20]. With the further understanding of pathophysiology and biomechanics of ankle arthritis, as well as the progress of surgical technology, supramalleolar osteotomy has made extensive progress in the treatment of early VAO. The main indications are Takakura stage II-III [6] and mid-term ankle arthritis with more than 50% tibiotalar articular cartilage reserved. The purpose of supramalleolar osteotomy is to transfer the lower limb load line to the relative normal cartilage area of the lateral ankle joint, restore the talus load center, correct the shear stress of the talus loaded obliquely [21], rearrange the posterior foot line, and improve the triceps torque of the leg. Supramalleolar osteotomy can preserve the patient's own joint, reduce pain, improve ankle function, restore physical activity and delay the progress of ankle arthritis [21].

varus ankle arthritis and Cora
Cora of most patients with VAO is close to ankle point or located in ankle joint [22]. Open or closed supramalleolar osteotomy without Cora will lead to horizontal displacement of the mechanical axis of the distal end of the osteotomy. For severe supramalleolar deformity, additional horizontal correction should be considered to avoid postoperative ankle joint load and abnormal appearance of the hindfoot. The fornix osteotomy with the osteotomy line passing through Cora and rotating around this point can avoid poor correction of force line and load [23].

clinical effect of supramalleolar open osteotomy:
The open osteotomy of the medial and superior malleolus is a simple operation, which can correct the deformity of < 10 ° varus ankle arthritis and sagittal deformity of the ankle. Takakura et al. [6] initially reported 18 cases (18 ankles) of VAO treated by open supramalleolar osteotomy, with an average followup of 6 years and 11 months. The results were excellent in 6 ankles, good in 9 ankles and fair in 3 ankles; 7 cases of brocartilage regeneration were found in 10 patients during the second stage arthroscopic examination. Knupp et al. [24] followed up 94 patients with supramalleolar osteotomy for 43 months, the FAS score improved from 55.6 ± 17.2 to 72.8 ± 18.9, the VAS score decreased from 4.6 ± 1.9 to 2.8 ± 2.3, and the improvement of Takakura grade of joint degeneration was not obvious. Hongmou et al. [12] followed up 41 patients with Takakura stage II and III varus ankle osteotomy (average 36.6 months). The average fracture healing time was 3.8 months. The FAS score was improved from 50.8 ± 13.6 to 83.1 ± 9.6, and the Maryland score was improved from 58.3 ± 12.0 to 81.6 ± 6.0 Fornix osteotomy is suitable for CORA close to ankle or in-joint malformation, orthopaedic range is large, bone osteotomy risk is low, but fornix osteotomy is only a single plane orthopaedic. Chopra and others recommend that the fornix osteotomy treat VAO, usually combined with the bula coronary position oblique or short cut bone. However, Lee and others pointed out that for VAO patients with widening ankle cavities (inner ankle wear, loose external ligaments) after the implementation of the outer ankle bone osteotomy is easy to aggravate the widening of the ankle cavity. In this study, patients with severe internal ankle wear were excluded, and external ankle instability resulted in external ankle-from bone gap widening patients with Brostrom's external ankle ligament strengthening to restore outer ankle-bone stability. The front-way fornix osteotomy can directly deal with internal lesions in the ankle, surround the CORA orthopaedics to avoid poor ankle strength after surgery, and after the excision of the bula section, the patient can rely on the combined stability of the lower tibia and the dynamic structure of the ankle muscles to achieve postoperative ankle cavity self-adaptation, which is conducive to the recovery of the patient's ankle biometric structure. In short, the ankle fornix osteotomy joint bula section excision technology to treat VAO can effectively solve the ex-ankle and tibia-distance joint lesions, while rotating orthopaedics around CORA to avoid displacement from the bone side, improve the distribution of the load in the VAO ankle and then delay the ankle degrease, the recent effect is better than the simple ankle open osteotomy;

Declarations Ethics declarations
Ethics approval and consent to participate The A liated Hospital of Chengdu University granted approval, and informed consent was obtained for all participants included in the study .

Consent for publication
Participants' consent to publish was granted.

Competing interests
The authors declare that they have no competing interests.