Clinical and Radiographic Outcomes of a Tibial Precut Technique for Severe Varus Deformity in Transfibular Total Ankle Arthroplasty: A Retrospective Case Series

Abstract

Background: Achieving orthogonal coronal-plane alignment in total ankle arthroplasty (TAA) remains challenging in cases with severe varus deformity. We developed a novel tibial precutting technique for use in transfibular TAA to resolve intra-articular bony conflict and enable accurate implant placement without excessive medial soft tissue release. Methods: This technique involves a controlled resection of the lateral distal tibia to eliminate impingement between the tibial plafond and talar dome. From November 2019 to June 2022, 15 patients with coronal varus deformities >15° underwent transfibular TAA using this method. Twelve patients with ≥2 years of follow-up were retrospectively evaluated. Coronal alignment was assessed using the tibiotalar angle (TTA) on weight-bearing radiographs. Clinical outcomes were measured using the Self-Administered Foot Evaluation Questionnaire (SAFE-Q) and ankle range of motion (ROM) before surgery and at final follow-up. Results: The median TTA significantly improved from 20.4° (IQR: 18.1–24.3) preoperatively to 1.8° (IQR: 0.9–3.6) at the latest follow-up (p < 0.01), indicating successful correction to neutral alignment. All SAFE-Q subscales showed statistically significant improvement (p < 0.05), and ankle ROM also increased significantly postoperatively (p < 0.05). No cases of talar subsidence, implant lucency, fibular non-union, or avascular necrosis were observed. Conclusions: These results indicate that the TIBIA #2 technique can broaden the indications for transfibular total ankle arthroplasty in severe varus deformity while delivering meaningful clinical benefit. Nevertheless, confirmation in larger, controlled, and multi-centre cohorts is required before widespread adoption.

1. Introduction

Over the past two decades, the clinical outcomes of total ankle arthroplasty (TAA) have remarkably improved with advancements in implant design and surgical techniques. However, the use of TAA in ankles with severe preoperative deformities remains a considerable challenge [1,2,3]. In particular, primary ankle osteoarthritis (OA) with severe varus deformities, which is common in Asian populations, often involves relative distal tibial-talar erosions, deformity of the medial malleolus, and medial soft tissue contracture. These bony and soft tissue factors collectively pose challenges in achieving precise orthogonal coronal-plane alignment (perpendicular to the weight-bearing axis) during implantation, which is widely recognized as essential for the long-term survivability of TAA [1,4]. Recent advances such as patient-specific 3D planning, 3D printing, and intraoperative navigation have been increasingly used in orthopedic surgery to improve accuracy in complex deformity correction procedures [5,6,7].

The surgical technique manual for lateral approach TAA using the TM Ankle (Zimmer Biomet, Warsaw, IN, USA) does not describe management strategies for cases with severe preoperative varus deformity. In such cases, the realignment procedures to prepare for orthogonal bone cutting are often blocked by bony obstruction at the lateral part of the joint due to varus deformity at the tibial plafond surface and soft tissue contracture of the deltoid.

To overcome these limitations, we introduced a modified surgical approach using a tibial precut technique to eliminate bony obstruction prior to fixation in the surgical frame. This study aimed to investigate whether the tibial precut technique could improve the alignment and clinical outcomes in patients with severe varus ankle deformity undergoing transfibular TAA. We hypothesized that this technique would allow more accurate correction of deformity and facilitate functional recovery, with a low rate of complications.

2. Materials and Methods

This study was approved by the Institutional Review Board of our hospitals (Approval numbers: 5001 and 22045; Approval dates: 25 October 2018 and 30 June 2022). Written informed consent was obtained from all participants. Fifteen consecutive cases with a preoperative coronal-plane varus deformity greater than 15 degrees who underwent transfibular TAA using this technique between November 2019 and June 2022 were included. Inclusion criteria were patients who underwent transfibular TAA using the TIBIA #2 technique, with a minimum of 2 years of follow-up and complete radiographic and clinical data. Exclusion criteria included patients with less than 2 years of follow-up, prior ipsilateral ankle fusion, active infection, or severe bone loss rendering TAA contraindicated.

2.1. Surgical Technique

The fibula was osteotomized according to the manufacturer’s instructions, and the lower leg was positioned on the alignment frame. A transosseous calcaneal pin was placed, and the sole was then secured to the footplate using calcaneal pin holders. Subsequently, the medial talar half-pin was inserted and fixed to the talar pin post on the footplate.

The TIBIA #2 technique was indicated when preoperative valgus stress radiographs showed that the talar dome cannot be corrected to a position perpendicular to the tibial axis due to bony conflict. A distal tibial pin was inserted from the anterior surface, approximately 5 cm proximal to the tibiotalar joint, and connected to the alignment frame. The silhouette guide was then positioned laterally, and the cutting block was adjusted until aligned with the talar dome. Once alignment was confirmed, the cutting guide was fixed in place, the silhouette guide removed, and bone cutting was initiated. A preliminary cut on the lateral distal tibia was performed through the TIBIA #2 hole to eliminate bony impingement between the lateral talar wedge and distal tibia. This “TIBIA #2 technique” utilized a guide hole originally designed for auxiliary resection after primary cuts with the TALUS and TIBIA #1 holes. Subsequently, the distal tibial pin was disconnected, and the alignment frame was manipulated into a valgus orientation to correct varus alignment. In cases with more severe deformity, the medial gutter was accessed anteriorly to perform a superficial deltoid ligament release and remove osteophytes. Fluoroscopy was used to confirm coronal alignment: on AP view, the talar dome was aligned horizontally and the tibia vertically. The ankle was distracted along the frame to allow appropriate bone resection while maintaining medial soft tissue tension (Figure 1) [8].

Standard bone cuts were subsequently performed according to the manufacturer’s guide, followed by trialing and implantation. The fibula was shortened and fixed with a plate or screws to address coronal deformity, and a Broström repair of the anterior talofibular ligament was performed before wound closure (Figure 1). If dorsiflexion angle of the ankle joint was less than 10 degrees, additional Achilles tendon lengthening was performed. A tourniquet was employed as required and released after a maximum of 2 h.

2.2. Radiographic Assessment

Radiographic assessments were performed on weight-bearing anteroposterior radiographs of the tibiotalar joint preoperatively, 3 months postoperatively, and at the latest follow-up visit. All radiographic measurements were performed by a single orthopedic surgeon who was not blinded to the clinical data. Coronal angulation of the tibiotalar joint was assessed using the tibiotalar angle (TTA; Figure 2) on weight-bearing anteroposterior radiographs both preoperatively and postoperatively.

A TTA between 5 degrees valgus and 5 degrees varus was considered as neutral alignment [9]. Successful fusion of the fibular osteotomy was defined according to previously described clinical criteria (absence of pain or warmth, with reduced swelling and improved stress stability) and radiographic criteria (at least 85% visible trabecular bridging across the osteotomy site without peri-implant lucency) [10].

2.3. Clinical Assessment

The self-administered foot evaluation questionnaire (SAFE-Q) was used preoperatively and at the latest follow-up to examine clinical outcomes. The SAFE-Q was developed by the Japanese Society for Surgery of the Foot as a region-specific assessment tool [11,12]. The main part of the SAFE-Q consists of 34 questions with five subscale scores: “pain and pain-related,” “physical functioning and daily living,” “social functioning,” “shoe-related,” and “general health and well-being.” Passive range of motion (ROM) of the ankle was clinically evaluated at the preoperative and last follow-up visits.

2.4. Statistical Analysis

Continuous variables are expressed as median (interquartile range [IQR]), and categorical variables are expressed as counts (percentages). The Wilcoxon signed-rank test was employed to compare the preoperative and postoperative radiographic assessments, as well as clinical values. In addition to p-values, effect sizes with 95% confidence intervals were calculated using rank-biserial correlation to provide estimates of the magnitude of change. The level of statistical significance was set at p = 0.05. Statistical analyses were performed using R software (http://www.r-project.org/ (accessed on 6 June 2025)).

3. Results

Of the 15 patients, 3 were lost to follow-up. Therefore, 12 patients were included in this study. Demographic characteristics of the three patients who were lost to follow-up included a 51-year-old male with post-traumatic osteoarthritis, a 68-year-old male with primary osteoarthritis, and an 88-year-old female with primary osteoarthritis. The median follow-up period was 35.7 (IQR: 30.3 to 41.8) months. Characteristics of the 12 patients enrolled in the study are presented in

Table 1. Patient characteristics (n = 12).

Age, years, median (IQR)	71.0 (63.5, 76.0)
Sex, male, n (%)	9 (75.0)
Diagnosis
Primary osteoarthritis, n (%)	6 (50.0)
Posttraumatic osteoarthritis, n (%)	3 (25.0)
Rheumatoid arthritis, n (%)	3 (25.0)

Abbreviation: IQR, interquartile range

.

All patients underwent the “TIBIA #2 technique”. In conjunction with TAA, Achilles tendon lengthening was performed in three cases, metatarsal dorsiflexion osteotomy was performed in two cases, superficial medial ligament release and medial malleolar osteophyte resection were performed in six cases, and artificial ligament reinforcement of the distal tibiofibular ligament was performed in two cases. A tibial fracture at the distal tibial pin insertion level occurred in one patient 5 weeks postoperatively. Although the bone union was achieved with conservative treatment, the longitudinal axis of the tibia shifted in the anteroposterior view. Therefore, this case was excluded from clinical and radiographic evaluations. No other complications or cases requiring revision surgery were observed.

Regarding coronal tibiotalar alignment, the TTA significantly decreased from a preoperative median of 20.4 degrees (IQR: 18.1 to 24.3) to a 3-month postoperative median of 3.0 degrees (IQR: 0.8 to 4.0) (p < 0.01). The effect size was 0.89 (95% CI: 0.89–0.90), indicating a large effect. At the latest follow-up, the TTA remained significantly lower than the preoperative values 1.8 degrees (IQR: 0.9 to 3.6) (p < 0.01). The effect size was 0.88 (95% CI: 0.88–0.89), indicating a large effect. The radiographic results for each case are demonstrated in Figure 3.

Except for one case with a postoperative tibial fracture resulting in altered tibial alignment, all cases had a neutral alignment (5 degrees varus to 5 degrees valgus) at the latest follow-up. No cases of talus subsidence, lucency, fibular non-union, or avascular necrosis were observed.

All SAFE-Q subscales showed significant improvement at the latest follow-up (p < 0.05, respectively;

Table 2. SAFE-Q subscale scores. The values are given as the median, with the interquartile range in parentheses.

SAFE-Q Subscale	Pre-Surgery	Latest Follow-Up	p *
Pain and pain-related	47.8 (33.6, 60.3)	74.7 (55.9, 86.1)	0.02
Physical functioning and daily living	38.6 (29.6, 50.0)	68.2 (53.4, 79.5)	0.02
Social functioning	33.3 (22.9, 50.0)	70.8 (45.9, 85.5)	0.03
Shoe-related	50.0 (37.5, 66.7)	75.0 (58.4, 95.8)	0.03
General health and well-being	45.0 (12.5, 65.0)	80.0 (40.0, 87.5)	0.02

Abbreviation: SAFE-Q, self-administered foot evaluation questionnaire. * The Wilcoxon signed-rank sum test was used to compare the pre- and postoperative values.

). The effect sizes for improvement were also large across all subscales: 0.84 (95% CI: 0.60–0.90) for pain, 0.89 (95% CI: 0.89–0.90) for physical function, 0.87 (95% CI: 0.77–0.90) for social function, 0.87 (95% CI: 0.77–0.91) for shoe-related problems, and 0.89 (95% CI: 0.89–0.91) for general health.

The ROM of the ankle significantly increased at the latest follow-up compared with preoperative values (p < 0.05; Figure 4). The effect size was 0.60 (95% CI: 0.11–0.90).

4. Discussion

In this study, near-orthogonal implantation alignment (within 5 degrees) was consistently achieved in TAA using the TM Ankle system for ankles with a preoperative varus deformity exceeding 15 degrees. Postoperative improvements in both patient-reported outcome measures and ROM were also observed despite the relatively short follow-up period of 2 years. Given that the data were derived from a small, single-race case series, the findings should be interpreted with caution and may have limited applicability to broader populations worldwide. However, the results of this study provide supportive evidence for the hypothesized efficacy of the “TIBIA #2 technique” in achieving reproducible orthogonal implantation.

Severe varus deformity of the ankle, particularly deformities exceeding 15 degrees, is generally considered a contraindication to TAA. Such deformities tend to result in misalignment during implantation and an imbalance in soft tissue tension. These factors increase the risk of edge loading, which may eventually lead to early implant failure [1,13,14]. In the conventional anterior approach (Figure 5), the position of the talus needs to be adjusted to maintain the physiological congruity of the lateral gutter articulation.

Moreover, significant talar lowering is required to achieve orthogonal alignment in cases of severe varus ankles. As talar lowering is often restricted by medial soft-tissue contracture, aggressive medial ligament release is frequently necessary, and additional procedures including medial malleolar osteotomy and/or tibialis posterior tendon lengthening may be employed as needed [1,15]. However, as the lateral approach utilized with the TM Ankle system involves fibular osteotomy (Figure 6), the congruity of the lateral gutter can be optimized by adjusting the height of the lateral malleolus, specifically by shortening the fibular length during internal fixation of the osteotomy site.

Additionally, if soft tissue imbalance occurs after implantation due to the relative looseness of the lateral capsule compared to the contracted medial capsule, augmentation of the anterior talofibular ligament with an artificial ligament can be easily performed. These features may collectively enhance the deformity correction capability of the TM Ankle system [16], while the TIBIA #2 technique appears to effectively address issues of bony conflict that challenge the realignment procedures necessary for orthogonal bone cutting. We believe that transfibular TAA using this technique has the potential to expand the indications for TAA to include ankles with severe preoperative varus deformities exceeding the 15-degree limit.

One complication observed in this series was a pin site fracture in one patient. Upon review, we believe this fracture resulted from pin insertion too close to the edge of the tibial cortex rather than the central metaphyseal region. This suboptimal positioning likely weakened the cortical support, predisposing the site to fracture. To prevent such complications, it is crucial to confirm the pin insertion site carefully and to ensure that the pin is placed within the central portion of the tibial metaphysis where cortical bone is more robust.

This procedure was developed independently and is not part of the standard surgical protocol provided by the implant manufacturer. Implementation of this technique should be determined with careful consideration at the discretion of each surgeon. Although this technique requires additional time for lateral tibial resection, the benefit of consistently achieving orthogonal alignment may outweigh this drawback, particularly in cases of severe varus deformity. Based on the principles of this technique, further refinement of procedures and/or devices can enhance the efficiency of the surgical sequence.

While recent studies have explored advanced technologies such as 3D planning or hybrid TAA techniques [17,18], our study was not designed to compare these methods. Although 3D planning can improve surgical accuracy and allow for detailed preoperative visualization, the TIBIA #2 technique offers a simple, quick, and reproducible solution that does not require special equipment. Instead, it focused solely on a specific technical refinement within the standard transfibular approach. Future comparative studies will be necessary to evaluate the relative clinical benefits of these evolving strategies.

5. Limitations

One of the major limitations of this study is the small sample size (n = 12), which may limit the generalizability of the findings. Although the results are promising, they should be interpreted with caution. Another key limitation is the absence of a control group treated using the standard anterior approach, which prevents direct comparison and weakens the level of evidence supporting the effectiveness of the TIBIA #2 technique. Future research with larger, prospective, and preferably multi-center cohorts is essential to validate these findings. Additionally, all radiographic measurements were performed by a single, non-blinded orthopedic surgeon involved in the procedures. The absence of interobserver and intraobserver reliability assessments, as well as potential confirmation bias due to lack of blinding, may have introduced systematic error in outcome evaluation. These limitations must be carefully considered when interpreting the radiographic improvements reported in this study.

6. Conclusions

In this retrospective series of 12 ankles with preoperative varus > 15°, the TIBIA #2 precut technique consistently restored neutral coronal alignment, reducing the median tibiotalar angle from 20.4° (IQR 18.1–24.3) to 1.8° (0.9–3.6). Patient-reported outcomes improved substantially (SAFE-Q pain 47.8 → 74.7; physical functioning 38.6 → 68.2; social functioning 33.3 → 70.8; shoe-related 50.0 → 75.0; general health 45.0 → 80.0), and ankle range of motion increased by a median of 10°. No talar subsidence, radiolucency, or implant-related failures were observed, and only one pin-site fracture occurred. These findings suggest that the TIBIA #2 technique may broaden the indications for transfibular total ankle arthroplasty in severe varus deformity while delivering meaningful clinical benefit. Nevertheless, confirmation in larger, controlled, and multi-centre cohorts is required before widespread adoption.