Transmalleolar tibiotalocalcaneal fusion with biologic augmentation and fibular preservation for chronic Charcot ankle arthropathy: A retrospective cohort study

Abstract

BACKGROUND

Charcot neuroarthropathy of the ankle presents significant surgical challenges with conventional tibiotalocalcaneal (TTC) fusion techniques often prioritizing mechanical stability while neglecting biological deficiencies, resulting in high non-union rates. This study evaluated a refined surgical approach integrating biological augmentation with fibular preservation.

AIM

To evaluate trans-malleolar TTC fusion with bone marrow aspirate (BMA)-soaked allograft and fibular preservation for chronic Charcot ankle arthropathy.

METHODS

We conducted a retrospective case series of 24 adult patients with chronic ankle Charcot arthropathy who underwent TTC fusion with biologic augmentation between 2023 and 2024 at a tertiary care trauma center. The technique involved a transmalleolar approach with fibular preservation, comprehensive joint preparation, and biologic augmentation using BMA-soaked allograft. Outcomes were assessed using the validated American Orthopedic Foot and Ankle Society hindfoot scale and Short Form-36 health survey with comprehensive radiographic evaluation.

RESULTS

At a mean follow-up of 1.5 years, 100% (24/24) of patients achieved successful TTC fusion confirmed by robust bony bridging. Mean American Orthopedic Foot and Ankle Society scores demonstrated significant improvement from 31.2 ± 9.1 preoperatively to 76.8 ± 14.2 at the final follow-up (P < 0.001), exceeding the minimal clinically important difference. Short Form-36 scores showed significant improvements across all domains with physical function scores improving from 29.4 ± 10.8 to 72.1 ± 15.3 (P < 0.001). Complications included breakage of both fibular fixation screws managed conservatively without compromising stability, nail protrusion requiring a minor removal procedure, and a periprosthetic tibial fracture treated conservatively with walker boot immobilization. No major infections, wound complications, or amputations were observed.

CONCLUSION

Trans-malleolar TTC fusion with BMA-soaked allograft and fibular preservation achieved high union and improved outcomes in chronic Charcot ankle arthropathy.

Key Words: Charcot arthropathy; Ankle fusion; Tibiotalocalcaneal fusion; Bone marrow aspirate; Biologic augmentation; Trans-malleolar approach; Fibular preservation

Core Tip: This retrospective case series evaluated a transmalleolar tibiotalocalcaneal fusion with biologic augmentation while preserving the fibula for chronic Charcot neuroarthropathy of the ankle. The technique aims to enhance stability, promote fusion, and reduce wound morbidity by avoiding fibular osteotomy and supplementing fixation with orthobiologics. We reported limb salvage, fusion, alignment, and complication outcomes, demonstrating consistent union and acceptable risks in a high-risk cohort. Transmalleolar tibiotalocalcaneal fusion with fibular preservation is a pragmatic, tissue-sparing option for complex Charcot neuroarthropathy ankles.

INTRODUCTION

Charcot neuroarthropathy of the ankle represents one of the most challenging conditions in foot and ankle surgery. It is characterized by progressive joint destruction, deformity, and potential limb loss. The condition predominantly affects patients with diabetes and peripheral neuropathy with ankle involvement occurring in approximately 10%-20% of cases[1]. The fundamental therapeutic objective involves achieving a stable, plantigrade, ulcer-free foot capable of withstanding daily functional demands.

Tibiotalocalcaneal (TTC) fusion remains the primary surgical intervention for advanced ankle Charcot arthropathy. However, conventional techniques have historically focused on mechanical stabilization through rigid fixation, often overlooking the inherent biological deficiencies that characterize the Charcot process[2]. These biological challenges include compromised bone quality, impaired vascularity, and dysregulated inflammatory responses that significantly impact healing potential. Consequently, traditional approaches report non-union rates ranging from 30%-50%, highlighting the limitations of purely mechanical strategies[3]. Existing surgical techniques often fail due to their inability to adequately address the hostile biological environment of the Charcot foot. Simple mechanical fixation, even with robust implants, cannot overcome the impaired osteogenesis and compromised soft tissue envelope. The innovation of this study lies in its dual approach: Robust mechanical stabilization combined with potent biological augmentation, a synergy that is critical for success in this patient population.

Recent advances in orthobiologic therapies have demonstrated promise in enhancing bone healing and fusion rates in challenging orthopedic contexts. Bone marrow aspirate (BMA) concentrate, rich in mesenchymal stem cells, growth factors, and osteoprogenitor cells, has emerged as a valuable adjunct in promoting osteogenesis[4].

The integration of biological augmentation with mechanical stabilization represents a paradigm shift toward addressing both aspects of the healing process. A study by Sherman et al[5] demonstrated that biologic augmentation of TTC arthrodesis using allogeneic bone block and osteoinductive agents combined with protected weight-bearing yielded high fusion rates (92.9% on plain radiographs and 90.9% on CT scans). This approach also led to favorable patient-reported outcomes, including reduced pain and preserved lower extremity function, suggesting its efficacy in challenging cases[5].

This study presented a technical refinement to the traditional transmalleolar TTC fusion approach that incorporates biological augmentation with BMA-soaked allograft and enhanced fibular preservation techniques. These technical modifications aim to address both mechanical instability and biological deficiencies inherent to Charcot arthropathy, potentially improving fusion rates and clinical outcomes over conventional methods.

MATERIALS AND METHODS

Study design and patient population

This retrospective case series analyzed 24 consecutive patients diagnosed with chronic ankle Charcot arthropathy who underwent TTC fusion with biological augmentation between January 2023 and December 2024 at a tertiary care trauma center. All procedures were performed by a single experienced foot and ankle surgery consultant to ensure technical consistency.

Inclusion and exclusion criteria

Inclusion criteria comprised adult patients (≥ 18 years) with chronic ankle Charcot arthropathy classified as Eichenholtz stage II (coalescence) or stage III (reconstruction) with anatomical classification as Brodsky type 3A or Sanders and Frykberg type IV. All patients had documented diabetes mellitus with recorded glycated hemoglobin levels and absence of active infection or severe peripheral vascular disease (ankle-brachial index ≥ 0.6).

Exclusion criteria included acute Charcot flares (Eichenholtz stage I), mechanical ulceration (Wagner grade ≥ 2), active osteomyelitis, severe peripheral vascular disease requiring revascularization, and systemic conditions significantly impairing bone healing.

Surgical technique

Step 1: Transmalleolar approach with periosteal preservation: The surgical approach was initiated through a lateral transmalleolar incision with a controlled lateral malleolar osteotomy performed approximately 2-4 cm proximal to the ankle joint line using an oscillating saw with the cut made perpendicular to the long axis of the fibula. The critical innovation involves opening the syndesmosis from anterior to facilitate preparation, followed by careful sliding and eversion of the fibula downward while maintaining its attachment to all related anatomical structures. Meticulous attention was paid to preserving the periosteal attachment and vascular supply to the entire distal osteotomized fragment, ensuring the fibular segment remained viable as a vascularized flap. This was achieved by careful subperiosteal dissection and protection of the perforating branches of the peroneal artery. This technique allows the preserved lateral malleolus to be retracted posteriorly using a Hohmann retractor, providing excellent visualization and access to both the ankle and subtalar joint complexes while maintaining the biological viability of the malleolar fragment for subsequent reconstruction and enhanced healing potential (Figures 1 and 2).

Figure 1 Transmalleolar approach with lateral malleolar osteotomy. A: Lateral malleolar osteotomy with preserved periosteal blood supply; B: Posterior retraction of the fibula with a Hohmann retractor providing exposure to the ankle and subtalar joints.

Figure 2 Joint surface preparation. A: Saw preparation of the inner aspect of the fibula and the lateral tibia at the syndesmosis level to create fresh, bleeding bone surfaces; B: Multiple drill holes created in the talus to enhance biological healing potential.

Step 2: Comprehensive joint surface preparation: Following adequate exposure, comprehensive joint surface preparation is initiated with meticulous debridement of both the subtalar and ankle joint surfaces using an oscillating saw, curettes, and rongeurs to remove all articular cartilage and sclerotic bone until healthy, bleeding subchondral bone was exposed. The inner aspect of the fibula and the lateral aspect of the tibia at the syndesmotic level were carefully prepared using an oscillating saw to create fresh, bleeding bony surfaces to facilitate tibiofibular fusion as part of the construct. The lateral wall of the talus was similarly prepared to optimize the interface for tibiotalar and talofibular arthrodesis. To enhance the biological healing potential, multiple microdrill holes were created throughout the talar body using a 2.0-mm drill bit, penetrating the subchondral bone to stimulate bleeding and promote revascularization (Figure 2).

Step 3: Guide wire insertion and retrograde intramedullary nail placement: Under fluoroscopic guidance a guide wire was inserted through the plantar aspect of the calcaneus and advanced across the subtalar and ankle joints into the tibial medullary canal. Following sequential reaming, an appropriately sized retrograde intramedullary nail was inserted and advanced until adequate purchase was achieved in the tibial metaphysis with final positioning confirmed fluoroscopically (Figure 3).

Figure 3 Tibiotalocalcaneal nailing procedure. A: Guide wire insertion through calcaneus across subtalar and ankle joints into tibia; B: Retrograde intramedullary nail insertion following standard technique.

Step 4: Biologic augmentation with BMA and allograft: BMA was performed using a Jamshidi needle inserted into the ipsilateral iliac crest or proximal tibia to harvest autologous BMA concentrate. Processed allograft chips were prepared and subsequently soaked with the concentrated BMA to create a biologically enhanced graft material that provided both osteoconductive scaffolding and osteoinductive properties for enhanced fusion potential (Figure 4).

Figure 4 Biologic augmentation preparation. A: Bone marrow aspirate using Jamshidi needle; B: Allograft preparation; C: Bone marrow aspirate mixed with allograft chips.

Step 5: Biologic graft insertion and impaction: The BMA-soaked allograft was carefully inserted into the prepared subtalar and ankle joint spaces, filling all void areas created by debridement. The biologically enhanced graft material was then impacted into the inner aspect of the fibula and all fusion interfaces using bone tamps to ensure optimal contact and integration with the prepared bony surfaces. This integrated biological augmentation strategy provided biological enhancement while preventing post-compression shortening (Figure 5).

Figure 5  Biologic graft insertion and impaction.

Step 6: Fibular reduction and “trap door” fixation: The lateral malleolus was anatomically reduced and temporarily secured with cannulated guide wires under fluoroscopic guidance. Two cortical screws were then inserted in a posteroanterior direction at approximately 18-20 degrees, similar to syndesmotic screw placement but positioned to avoid interference with the intramedullary nail. This innovative “trap door” technique transforms the preserved fibular fragment into a multifunctional construct that provides: (1) Enhanced mechanical stability through tibiofibular compression; (2) Biological augmentation by creating a sealed chamber for the BMA and allograft; and (3) Additional fusion surface area between the fibula, tibia, and talus (Figure 6).

Figure 6 Fibular reduction and fixation. A: Anteroposterior radiographic view showing fibular reduction with cannulated wires; B: Lateral radiographic view with cannulated wires; C: Anteroposterior radiographic view showing screw insertion; D: Lateral radiographic view showing screw placement; E: Final clinical image showing two screws inserted from fibula creating the “trap door” construct.

Postoperative management

Patients underwent strict non-weight bearing immobilization in below-knee casts for 6 weeks, followed by 6 weeks of partial weight-bearing in range of motion walker boots. Gradual progression to full weight-bearing occurred as tolerated with radiographic confirmation of healing. Protective footwear was maintained for a minimum of 6 months postoperatively.

Outcome assessment

Clinical evaluation utilized the American Orthopedic Foot and Ankle Society (AOFAS) hindfoot scale, which has been validated as the most widely used outcome measure for hindfoot fusion procedures and demonstrates excellent reliability in assessing pain, function, and alignment parameters in TTC fusion studies[6]. Radiological assessment included serial weight-bearing radiographs and CT scans at 6 months and 12 months to evaluate fusion progression. Radiological union was defined by trabecular bridging across joint interfaces or absence of clearly demarcated joint spaces. All complications were systematically documented.

Statistical analysis

Continuous variables were summarized as mean ± SD and range and categorical variables as n (%). Preoperative and postoperative AOFAS scores were compared using a paired-samples t test (two-tailed). A P < 0.05 was considered statistically significant. Statistical analyses were performed using SPSS Statistics (IBM Corp., Armonk, NY, United States).

RESULTS

Patient demographics

The study cohort comprised 24 patients with a mean age of 57.8 years (range 42-74). There were 14 males (58.3%) and 10 females (41.7%). All patients had diabetes mellitus with a mean glycated hemoglobin of 8.4% (range 6.9%-10.3%). The mean follow-up was 1.5 years (range 0.8-2.2 years).

Fusion outcomes

At the final follow-up successful TTC fusion was achieved in all 24 patients (100%). Fusion was confirmed by robust bony bridging across ankle and subtalar joints on both plain radiographs and CT scans, demonstrating complete osseous consolidation in the entire cohort.

Functional outcomes

Clinical outcomes demonstrated significant improvements across all measured parameters. Mean AOFAS hindfoot scores improved from 31.2 ± 9.1 preoperatively to 76.8 ± 14.2 at the final follow-up (P < 0.001), representing a mean improvement of 45.6 points. This improvement exceeded the minimal clinically important difference of 9 points for the AOFAS hindfoot scale, indicating clinically meaningful functional enhancement. Short Form-36 scores showed significant improvements across all domains with physical function scores improving from 29.4 ± 10.8 to 72.1 ± 15.3 (P < 0.001) and pain scores improving from 31.5 ± 9.4 to 76.3 ± 13.1 (P < 0.001).

Complications

Complications occurred in 3 patients (12.5%), all of which were managed successfully without compromising the overall treatment outcomes. The first patient developed breakage of both fibular fixation screws at 8 months postoperatively. Clinical and radiographic evaluation revealed that the screws had fractured but fusion was progressing satisfactorily with no evidence of construct instability or fibular displacement. This was managed conservatively with continued protected weight-bearing, and the patient achieved successful fusion without requiring screw removal or revision surgery.

The second patient presented with distal nail protrusion through the plantar heel at 6 months postoperatively, causing discomfort during weight-bearing. Radiographic assessment confirmed solid fusion across both ankle and subtalar joints. The protruding portion of the nail was surgically removed in the operating theater under spinal anesthesia with immediate relief of symptoms and no compromise to the fusion construct.

The third patient sustained a periprosthetic tibial fracture at the proximal extent of the nail at 10 months postoperatively following a minor fall. The fracture was classified as a non-displaced hairline crack without involvement of the fusion site. Management consisted of immediate cessation of weight-bearing and immobilization in a below-knee cast for 8 weeks, followed by progressive weight-bearing in a walker boot. The fracture healed uneventfully with conservative management, and the patient maintained successful TTC fusion.

No major infections, wound healing complications, deep vein thrombosis, or amputations occurred in this series. All patients maintained plantigrade foot positioning with no significant loss of correction at final follow-up.

Radiographic outcomes

Mean time to radiographic union was 4.1 months (range 2.8-7.2 months). All patients with successful fusion demonstrated solid bony bridging with no evidence of hardware loosening or construct failure at final follow-up. Hindfoot alignment was maintained in all cases with no significant loss of correction. The 3 patients with complications all achieved successful fusion despite their respective hardware-related issues.

DISCUSSION

This case series demonstrated excellent outcomes for a refined transmalleolar TTC fusion technique incorporating biological augmentation and fibular preservation in chronic ankle Charcot arthropathy. The achieved 100% fusion rate represents a substantial improvement over historical reports of conventional techniques, which typically report fusion rates of 50%-70% in similar patient populations[7].

The biological enhancement strategy utilizing a BMA-soaked allograft directly addresses the fundamental healing deficiencies characteristic of Charcot arthropathy. BMA concentrate provides mesenchymal stem cells, growth factors, and osteoprogenitor cells essential for robust osteogenesis[8]. This biological augmentation, combined with comprehensive joint preparation and strategic graft placement, creates an optimal environment for fusion while addressing the compromised healing potential inherent to Charcot bone.

Siddiqui et al[9] investigated a novel approach to enhance arthrodesis rates in Charcot neuroarthropathy by combining distal tibial distraction osteogenesis with TTC or tibiocalcaneal fusion. This technique resulted in a high arthrodesis rate of 93.3% (14 out of 15 patients) with a mean time to fusion of 4.75 months. The authors suggested that distraction osteogenesis enhanced vascularity at the arthrodesis site, thereby promoting bone healing and providing a viable salvage option for complex Charcot reconstructions[9].

He et al[10] conducted a retrospective study comparing fibular osteotomy, fibular strut, and fibular preservation techniques in TTC arthrodesis using retrograde intramedullary nails. Their findings indicated that the fibular strut group had a significantly shorter fusion time (15.1 ± 2.8 weeks) compared with fibular osteotomy (17.2 ± 1.9 weeks) and fibular preservation (16.8 ± 1.9 weeks). The fibular strut technique also provided superior anti-rotation ability and enhanced stability due to the lateral support of the fibula, suggesting its benefits in accelerating bone healing and improving construct stability. Our technique built upon the principles of fibular preservation but with the added benefits of the “trap door” mechanism, which not only preserves the fibula but actively incorporates it into the fusion mass, creating a contained environment for the biologic graft and enhancing the overall stability of the construct. This differs from simple fibular preservation, which may not provide the same degree of containment or rotational control.

The innovative fibular preservation technique represents a significant departure from traditional approaches that often involve fibular resection. By maintaining the fibula as a viable, vascularized flap and incorporating it into the fusion construct through the “trap door” mechanism, we achieved multiple benefits: Enhanced mechanical stability; additional fusion surface area; and a biological chamber for graft material. This approach also prevented post-compression shortening, a common complication that can compromise functional outcomes.

The complication rate of 12.5% compared favorably with published series of similar complexity. Importantly, all three complications were managed successfully without compromising fusion outcomes or requiring major revision procedures. The conservative management of loose syndesmotic screws in the presence of progressing fusion demonstrates the importance of individualized treatment approaches based on clinical and radiographic findings rather than routine hardware removal. The case of nail protrusion while requiring minor surgical intervention highlighted the importance of careful nail sizing and positioning during the initial procedure. The successful management with simple nail removal without compromise to the fusion construct demonstrated the resilient nature of the biological augmentation strategy. The periprosthetic tibial fracture case illustrated the potential for late complications in this patient population, particularly given the compromised bone quality associated with Charcot arthropathy. The successful conservative management with maintained fusion integrity supports the durability of the biological enhancement approach.

While studies like Love et al[11] have found non-union rates as high as 44% and significant infection rates in patients with high-risk Charcot undergoing tibiocalcaneal arthrodesis, our refined technique demonstrated a substantially lower complication profile. Consistent with findings by Kim et al[12], our study indicates that successful limb salvage through TTC fusion is achievable even in cases with severe deformity, underscoring the paramount importance of infection control and comprehensive surgical planning.

The significant improvement in AOFAS scores with a mean improvement of 45.6 points demonstrated not only statistical significance but also clinically meaningful functional enhancement. This improvement substantially exceeds published minimal clinically important difference values, indicating that patients experienced genuine functional benefit from the procedure.

Recent literature supports the integration of biological and mechanical strategies in challenging orthopedic reconstructions. Studies have demonstrated improved outcomes with biological augmentation in various clinical contexts, particularly in patients with compromised healing potential[13]. Our results align with this trend, suggesting that addressing both mechanical and biological aspects of healing can significantly improve outcomes in Charcot reconstruction.

Limitations

This study had several inherent limitations that should be acknowledged. The retrospective design, moderate sample size, and absence of a control group limit the strength of the conclusions that can be drawn. The single-surgeon experience ensured technical consistency but may have limited the generalizability of the findings to other surgical practices. Additionally, 1 patient had a follow-up period of only 9 months, which may be insufficient to fully assess long-term fusion durability and functional outcomes. The relatively short overall follow-up period while adequate for assessing fusion may not capture long-term durability of the construct or late complications.

Future directions

Future research should focus on prospective, comparative studies with larger cohorts and extended follow-up to validate these findings. Direct comparison with traditional TTC fusion techniques would provide valuable insights into the relative benefits of biological augmentation. Long-term studies examining construct durability and functional preservation would strengthen the evidence base for this approach. Additionally, a cost-effectiveness analysis would be valuable given the additional expense of biological augmentation materials.

CONCLUSION

The refined transmalleolar TTC fusion technique incorporating biological augmentation with BMA-soaked allograft and fibular preservation demonstrated high fusion rates and favorable clinical outcomes in chronic ankle Charcot arthropathy. The 100% fusion rate and significant functional improvements observed in this series are promising and suggest that this technique effectively addresses both mechanical instability and biological deficiencies characteristic of Charcot arthropathy, offering hope for improved outcomes in this challenging patient population. The successful conservative management of complications in this series demonstrated the robustness of the biological augmentation approach and the importance of individualized treatment strategies. The integration of biological and mechanical strategies represents a paradigm shift in Charcot reconstruction that warrants further investigation through prospective, comparative studies with extended follow-up periods.

ACKNOWLEDGEMENTS

The authors thank the surgical and nursing teams who assisted with patient care.