Functional and Radiological Benefits of Adding Fibular Osteotomy to Supramalleolar Osteotomy in Ankle Osteoarthritis

Introduction

Ankle osteoarthritis is a chronic degenerative disorder characterized by prominent pathological features such as cartilage degradation, secondary cartilage hyperplasia, and subchondral bone ossification [1–3]. Epidemiological data indicate a prevalence of approximately 1%, with 70% to 78% of diagnosed cases attributed to post-traumatic osteoarthritis [4,5]. Clinically, this condition is primarily characterized by recurrent pain, swelling, and functional impairment of the ankle joint. Furthermore, up to 37.5% of patients demonstrate asymmetric disease progression and commonly exhibit concurrent varus deformity, thereby establishing it as the leading cause of foot and ankle pain in individuals over the age of 50 [6–9]. It is noteworthy that the incidence of ankle osteoarthritis has exhibited a trend toward younger age groups in recent years, particularly manifesting as a significant increase among physically active adolescent populations [10]. Ankle osteoarthritis is increasingly recognized as a significant threat to human health, contributing substantially to social and economic burdens and posing considerable challenges in clinical management.

Currently, the treatment approaches for osteoarthritis can be broadly categorized into conservative and surgical interventions. The primary treatment objectives include alleviating pain, correcting deformities, delaying the progression of joint degeneration, and enhancing overall quality of life [11,12]. For the management of symptomatic ankle osteoarthritis, early-stage interventions typically involve pharmacological therapy, physical therapy, and intra-articular injections of sodium hyaluronate. In the end stages of ankle osteoarthritis, joint fusion or replacement remains the primary treatment approach. There remains substantial clinical controversy regarding the optimal treatment of Takakura Stage II–III ankle osteoarthritis, which is an asymmetric mid-term ankle arthritis characterized by the narrowing of the medial joint space and the varus tilt of the talus on weight-bearing radiographs. As an important part of the ankle acupoint, the length and position of the fibula and its relationship with the distal tibiofibular syndesmosis are crucial to maintain the stability and load distribution of the ankle joint. In the process of ankle arthritis, it is often accompanied by relative shortening and displacement of the fibula or abnormal micromovement of the distal tibiofibular syndesmosis, which may aggravate the mismatch of ankle points and local stress concentration [13]. In recent years, supramalleolar osteotomy (SMOT) has emerged as an effective treatment for non-terminal, asymmetric ankle arthritis [14–16]. The principle is to restore the lower limb force line by correcting the coronal deformity of the distal tibia, so that the joint contact pressure is transferred from the area of severe wear, and then the joint coordination is reformed [17,18]. The prevailing view is that combined fibular osteotomy is an essential step for correcting severe varus deformity. This procedure facilitates the improvement of talar tilt (TT) and tibiocrural angle (TC), thereby enabling a better restoration of ankle point matching. Biomechanical research also indicates that fibular osteotomy can encourage the lateral shift of tibiotalar joint contact pressure [19]. Nevertheless, certain studies adopt different stances and propose that the integrity of the fibula should be preserved to the greatest extent possible during the osteotomy. Alternatively, the decision regarding fibular osteotomy should be solely based on patient-specific intraoperative alignment and stability [20–22].

We hypothesized that fibular osteotomy might play a role in the reset surgery and might help restore the consistency of the ankle joint. Therefore, this retrospective study of 65 patients with mid-stage (Takakura Stage II–III) ankle osteoarthritis aimed to compare functional and radiological outcomes from simple supramalleolar osteotomy and supramalleolar osteotomy combined with fibular osteotomy.

Material and Methods

ETHICS STATEMENT:

The study was approved by the Ethics Committee of our hospital (CZX2024191) and the requirement for informed consent was waived by the Ethics Committee of our hospital since this was a retrospective study and the data were anonymous.

INCLUSION AND EXCLUSION CRITERIA:

We retrospectively analyzed the therapeutic efficacy of 2 surgery approaches for 70 patients who were admitted to our department and received SMOT combined with or without fibular osteotomy for the treatment of varus ankle arthritis from January 2021 to June 2023. They were divided into the SMOT group and the SMOT with fibular osteotomy (SMOT+FO) group. The inclusion criteria were as follows: (1) adults over the age of 18; (2) primary or traumatic ankle osteoarthritis classified as stage 2 or 3 based on the modified Takakura staging system [23]; (3) varus deformity, characterized by a distal tibial articular surface angle (TAS) of less than 84° [24]; (4) clinical symptoms, like pain and functional disorders; (5) treated with SMOT with or without FO; and (6) at least 1-year follow-up. The exclusion criteria were: (1) juvenile patients or those with the tibial epiphysis not yet closed; (2) patients with Charcot arthropathy or rheumatoid arthritis; (3) patients with neuromuscular dysfunction; and (4) patients with acute or chronic infection of the ankle joint.

PREOPERATIVE MANAGEMENT:

A researcher who was not involved in the study collected baseline clinical data from all patients, including age, gender, affected side, Takakura stage, American Orthopaedic Foot and Ankle Society (AOFAS) score, Visual Analogue Scale (VAS) score, and ankle range of motion (ROM). Preoperative imaging assessments, including anteroposterior and lateral radiographs, computed tomography (CT), and magnetic resonance imaging (MRI), were conducted for all patients. Key radiographic parameters – TT, TAS, TC, and tibial lateral surface angle (TLS) – were measured (Figure 1A, 1B). All these surgeries were independently performed by the same group of experienced foot and ankle surgeons, each with over 10 years of clinical experience. Radiographic parameters were measured by a third orthopedic surgeon not involved in the procedure using a picture archiving and communication system (PACS; medSynapse 5.30.0). Each parameter was measured 3 times, and the average value was used for final analysis.

OPERATIVE TECHNIQUE:

All surgeries were conducted under spinal anesthesia, and tourniquets were used in all cases. The skin was routinely disinfected using iodine followed by alcohol, and subsequently covered with a sterile surgical drape. A longitudinal incision measuring approximately 8 to 10 centimeters was made on the anterior-medial aspect of the affected ankle joint. The underlying tissues were then carefully dissected in a layer-by-layer manner to expose the distal tibia and ankle joint, followed by the removal of osteophytes located on the anterior and medial surfaces.

The osteotomy line was marked approximately 4–5 cm proximal to the medial malleolus tip and a 2.0 mm Kirschner wire was inserted from the upper medial aspect to the lower lateral aspect, directing it toward the anterior margin of the distal tibiofibular syndesmosis. Placement was confirmed using C-arm fluoroscopy. Using a reciprocating saw, a controlled osteotomy was performed along the Kirschner wire, cutting through the medial and posterior cortices of the tibia while preserving approximately 1 cm of the lateral cortex to serve as a mechanical hinge. The osteotomy gap was then gradually widened using a broad osteotome. Intraoperatively, the alignment of the distal tibial articular surface was assessed via fluoroscopic imaging, aiming for a TAS angle between 88° and 92° and a TT angle of less than 5°. Subsequently, an allograft bone block was inserted and the construct was secured with a locking plate. All surgical steps were verified using anteroposterior and lateral fluoroscopic imaging to confirm implant positioning and the accuracy of angular correction. In the observation group, after the completion of tibial osteotomy, fibular osteotomy was performed. A lateral ankle incision was made to expose the distal end of the fibula. Using a reciprocating saw, the fibular osteotomy was performed at the level of the inferior tibiofibular joint or slightly above it. The osteotomy line in the coronal plane was oriented from the superior-lateral to the inferior-medial direction, forming an approximate angle of 45° with the fibular axis. Following the osteotomy, the fibula was slightly shortened and its valgus angle was increased to enhance the congruence of the ankle mortise. Once satisfactory correction was confirmed under C-arm fluoroscopic guidance, fixation was performed first on the tibia and subsequently on the fibula (Figure 1C, 1D). Both groups of patients underwent surgical closure utilizing standardized, stratified suture techniques. Sterile dressings were applied under pressure, and the ankle joint was maintained in a neutral position throughout the procedure. The surgical process strictly followed aseptic principles, and prophylactic antibiotics were administered within 24 hours after surgery.

POSTOPERATIVE MANAGEMENT:

Both groups of patients followed a standardized stepwise rehabilitation protocol postoperatively, adhering to the principle of early mobilization and delayed weight-bearing. On the second day after surgery, patients began performing isometric muscle contractions and flexion-extension exercises of the interphalangeal joints independently. Partial weight-bearing was permitted 6 weeks postoperatively, although strenuous activities were discouraged. Full weight-bearing and a gradual return to normal daily activities were allowed only when radiographic examination confirmed bony union at the osteotomy site.

POSTOPERATIVE CLINICAL AND RADIOGRAPHIC EVALUATIONS:

All baseline data of the subjects were systematically collected. All patients underwent clinical and imaging follow-up assessments at 3 months, 6 months, and 12 months postoperatively, and at the time of the final follow-up. At each follow-up visit, a physical examination was conducted, and anteroposterior and lateral ankle radiographs, as well as CT or MRI scans, were obtained. In the context of imaging evaluation, TT, TC, TLS, and TAS were measured at the final follow-up using PACS to quantitatively analyze changes in ankle alignment and ankle point matching, respectively. The functional outcome was assessed through the following approaches: The VAS was employed to quantify pain at the final follow-up, and the AOFAS ankle-hindfoot scoring system was utilized to evaluate pain, function, and alignment throughout the entire follow-up period. Simultaneously, the ankle dorsiflexion and plantar flexion range of motion were passively measured with a protractor, and these were combined and calculated as the total ROM to evaluate joint function.

STATISTICAL ANALYSIS:

SPSS 26.0 statistical software (SPSS Corporation, Chicago, USA) was used for data analysis in this study. The normality of measurement data (including VAS score, AOFAS score, ROM in clinical evaluation, and TT, TC, TLS, and TAS in imaging evaluation) was first evaluated by Shapiro-Wilk test. Data with normal distribution were expressed as mean±standard deviation. Independent sample t test was used for comparison between groups (such as combined osteotomy group and simple osteotomy group), and paired sample t test was used for comparison within groups before and after operation. Data that did not follow a normal distribution were presented as medians (interquartile ranges) and analyzed with the use of nonparametric tests. Count data (such as gender and Takakura stage distribution) were expressed as the number of cases (percentage), and comparison between groups was based on sample size and theoretical frequency, using the chi-square test or Fisher’s exact test. For all statistical analyses, P<0.05 was considered statistically significant.

Results

COMPARISON OF GENERAL INFORMATION BETWEEN 2 GROUPS OF PATIENTS:

Ultimately, 65 patients (18 male and 47 female; mean age, 53.2 years; age range, 40 to 68 years) were included in the final analysis, while 5 patients were excluded due to insufficient follow-up duration (less than 12 months). As shown in Table 1, no statistically significant differences were observed between the SMOT group and SMOT+FO group with respect to age, sex, affected side, symptom duration, Takakura stage, follow-up period, or imaging parameters (all P>0.05). Throughout the follow-up period, no cases of internal fixation failure, nonunion at the osteotomy site, malunion, or other complications were identified.

COMPARISON OF THE PREOPERATIVE AND LAST FOLLOW-UP TIME BETWEEN THE 2 GROUPS:

As shown in Table 2, both groups exhibited significant improvements in AOFAS scores and VAS pain scores compared with preoperative values (P<0.001). However, no statistically significant improvement was observed in ankle ROM (all P>0.05). All radiographic parameters, including TAS, TT, TC, and TLS angles, demonstrated significant postoperative improvements relative to preoperative measurements in both groups (P<0.001).

CLINICAL FUNCTIONAL AND RADIOLOGICAL COMPARISON BETWEEN THE 2 GROUPS:

According to the available data, the SMOT+FO group demonstrated significantly better outcomes in AOFAS scores compared with the SMOT only group, with a statistically significant difference (P=0.001). However, no significant differences were observed between the 2 groups in terms of ROM and VAS scores (all P>0.05). With respect to radiological parameters, the improvements in the TT and TC angles in the SMOT+FO group were significantly greater than those in the SMOT only group (P<0.05). In contrast, no statistically significant differences were found in the improvements of the TLS and TAS angles between the 2 groups (all P>0.05). For detailed results, please refer to Table 3.

COMPARISON OF COMPLICATIONS IN THE 2 GROUPS:

A total of 3 postoperative infections were recorded (Table 4). In the SMOT group, 1 patient (2.9%) presented with superficial infection, which resolved following regular dressing changes. In the SMOT+FO group, 2 patients (6.4%) developed infections: 1 case (3.2%) of superficial infection that resolved after dressing changes, and 1 case (3.2%) of wound edge necrosis that was successfully managed after 2 debridement procedures and dressing changes. The overall incidence of postoperative complications in the SMOT group was lower than that in the SMOT+FO group (2.9% vs 6.4%; OR, 0.44; 95% CI, 0.04 to 5.10); however, the difference did not reach statistical significance (P=0.500).

Discussion

This study retrospectively evaluated the clinical outcomes of 65 patients with ankle arthritis who underwent supramalleolar osteotomy, either alone or in combination with fibular osteotomy. The results indicated that, with the exception of ROM, both groups exhibited significant improvements in AOFAS and VAS scores compared with preoperative values. Importantly, patients who received fibular osteotomy demonstrated greater improvements in postoperative radiological parameters, including the TT angle and TC angle. Furthermore, patients who underwent combined fibular osteotomy achieved superior AOFAS scores compared with those who underwent supramalleolar osteotomy alone, suggesting that this combined surgical approach may offer enhanced functional recovery and potential clinical benefits for patients with ankle arthritis.

Uneven load distribution across the lower limb joints may accelerate the progression of osteoarthritis. Joint-preserving surgical procedures, such as SMOT, are designed to correct biomechanical abnormalities through early intervention, with the aim of delaying or potentially reversing the disease process, improving joint function, and alleviating pain [25,26]. The fundamental mechanism of SMOT involves adjusting the weight-bearing axis of the lower limb to achieve a more balanced distribution of joint surface pressure, thereby preventing further deterioration of the arthritis [27,28]. Existing clinical and biomechanical evidence has demonstrated that SMOT yields significant therapeutic benefits in patients with early- to mid-stage ankle arthritis. However, whether fibular osteotomy should be performed in conjunction with SMOT remains a subject of debate. Biomechanical studies have shown that during a distal tibial valgus osteotomy, failure to perform fibular osteotomy may result in persistent medial concentration of talotibial joint contact pressure. In contrast, when fibular osteotomy is combined with SMOT, the contact pressure can be effectively redistributed toward the lateral side as the degree of external rotation increases, thereby restoring joint congruence [29,30]. Finite element analysis further supports this finding, indicating that in cases of varus ankle arthritis, the combination of SMOT and fibular osteotomy can significantly reduce medial pressure concentration and facilitate lateral displacement of the weight-bearing line [31]. Collectively, these findings suggest that fibular osteotomy plays a crucial role in optimizing the mechanical environment of the ankle joint.

The TAS angle is among the important parameters requiring correction in SMOT, with a normal reference range of 84°–100° [24]. In this study, the TAS angle in both patient groups returned to the normal range postoperatively; however, no statistically significant difference was observed between the 2 groups (P=0.817). In contrast, the TT angle, which serves as a critical indicator for determining whether to combine fibular osteotomy with SMOT, remains a subject of ongoing debate. Previous studies suggest that when the difference in TT angle between the affected and contralateral sides exceeds 5°, combining fibular osteotomy may enhance the correction of varus deformity [32,33]. Nevertheless, Tanaka et al [23] reported that satisfactory correction is often difficult to achieve through simple osteotomy alone in patients with a preoperative TT angle ≥10°. The findings of the present study indicate that the improvement in TT angle was more pronounced in the group receiving SMOT+FO, a result consistent with the findings of Zhao et al [15]. Furthermore, this study observed a significant improvement in the TC angle in the SMOT+FO group. This may be attributed to the structural optimization of the ankle joint following fibular shortening, thereby enabling more effective correction of the varus angle between the tibial axis and the ankle joint. Zhao et al [34] further supported this conclusion through biomechanical and clinical investigations, demonstrating that the addition of fibular osteotomy can lead to greater improvement in TC angle.

The results of this study demonstrate that patients who underwent SMOT+FO exhibited significantly improved AOFAS scores postoperatively, suggesting that this surgical approach can effectively enhance ankle function. However, no statistically significant differences were observed in the improvement of pain, as measured by the VAS, or in ROM between the 2 groups. These findings align with the conclusions of Pagenstert et al [35], which indicate that postoperative functional recovery is primarily associated with the extent of pain relief and not significantly correlated with improvements in ROM. Importantly, although the theoretical expansion of the surgical scope – through the addition of fibular osteotomy – may increase the risk of complications such as infection due to prolonged operative time and greater incision exposure, the present study revealed that the complication rate in the SMOT+FO group was only marginally higher than that in the simple SMOT group, without reaching statistical significance (P=0.500). This outcome suggests that, when surgical indications are strictly followed and standardized procedures are implemented, adding fibular osteotomy does not substantially elevate surgical risk.

This study has several limitations: Firstly, the follow-up period was relatively short (average 16 months). Although the early results indicated that fibular osteotomy could significantly improve ankle joint function, its long-term efficacy still needs to be verified through longer-term follow-up observations. Secondly, the small sample size (n=65) may lead to a certain amount of heterogeneity in the research results, affecting the reliability of the conclusions. Most importantly, there is currently a lack of well-designed prospective randomized controlled studies to systematically evaluate the exact mechanism and clinical value of fibular osteotomy in ankle arthrodesis. Future research should involve large sample sizes, multiple centers, and long-term follow-up in prospective studies to further clarify the indications and clinical significance of fibular osteotomy in the treatment of ankle osteoarthritis.

Conclusions

For patients meeting the surgical indications for SMOT+FO, this surgical approach not only significantly enhances ankle joint function but also exhibits distinct advantages in correcting critical radiological parameters, including the TT angle and TC angle. These anatomical corrections may provide patients with prolonged clinical benefits and an improved biomechanical environment.