Single-Stage Treatment of Chronic Subtalar Dislocation: A Case Report

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 Introduction

Isolated lateral dislocation of the subtalar joint is a relatively uncommon deformity, typically reported in the literature as a consequence of trauma.¹ Talar dislocations, although rare, are often depicted as neglected or associated with an initial fracture.² The chronic form of dislocation can develop in severe, long-standing cases of flatfoot, such as adult-acquired flatfoot deformity (AAFD), or in association with Charcot neuroarthropathy³, both of which are conditions that significantly impair quality of life.

A few treated cases of chronic subtalar dislocation are documented in the literature^2,4,5, altough all patients underwent surgery using either a transplantar nail for complete joint fusion^2,6, spatial frames⁷, or a combination of both techniques⁴. Corrections were also made through multiple successive procedures⁶, though rarely in a single operation^5,6.

We present a unusual case  of a chronic lateral subtalar dislocation without a fracture, trauma or Charcot neuroarthropathy managed with a single-stage operative procedure in order to restore pain-free weight bearing and ambulation.

 Case Description

A 55-year-old woman, with a medical history including rheumatoid arthritis, asthma, and hypertension, was referred to the specialist orthopedic clinic by her primary physician due to a 12-month progression of pain in her right ankle and challenges with walking. She denied any recent trauma to the affected ankle. Notably, she was diagnosed with acquired flatfoot over 5 years ago, which has since deteriorated, resulting in chronic deformity of the left foot and ankle.  Upon observation, her walking pattern showed signs of discomfort, suggestive of an antalgic gait. A pronounced valgus deformity was evident in her left foot and ankle, though no neurovascular deficits were observed. Notably, the severity of the valgus deformity had led to pronounced skin tension over the medial malleolus, accompanied by skin atrophy and ulceration (Fig. 1). Plain radiographs showed gross sclerosis and disorganization of the bones in the foot, with medial dislocation of the tarsus, as well as associated lateral dislocation of the calcaneum and cuboid (Fig. 1).

The computed tomography (CT) scan with 3D reconstruction revealed consistent findings with her hospital admission plain radiographs. Specifically, it confirmed lateral dislocations of both the subtalar and talonavicular joints. The talus showed no deformation and slight fragmentation. However, marked arthrosis and cyst formation were observed in the remaining talo-navicular and talo-calcaneal contact areas. Additionally, pseudoarticulations between the calcaneum and tibia were noted (Fig. 2).

Given the chronicity and severity of both the bony deformities and soft tissue involvement, a one-staged procedure was planned. In order to restore pain-free weight bearing and ambulation, talo-calcaneo-cuboido-navicular fusion was performed via a two side surgical approach (Fig. 2). The soft tissue contractures surrounding the bones were released. In the fusion procedure, four screws were utilized to secure the talus, calcaneus, cuboid, and navicular bones together. Initially, a talo-navicular fixation was performed using a single 4.5mm cannulated screw. Subsequently, a subtalar fixation was achieved with two 6.5mm cannulated screws. Finally, a cuboido-talar fixation was established using another 4.5mm cannulated screw (Fig. 3).

The incongruent joint surfaces were prepared by removing cartilage and filled with frozen cancellous allograft. Both surgical wounds eventually healed successfully. The lateral wound required an additional two months for complete closure due to the presence a small area of skin necrosis, while non-weight-bearing status was maintaned for three months. Initially, the patient was immobilized in a back slab for the first two months, followed by the use of a walking boot thereafter. Full weight-bearing activity was gradually reintroduced after three months. Physiotherapy was initiated after 3.5 months. The patient achieved her goal of independent weight bearing and ambulation 4,5 months following the reconstructive process, with good cosmetic and functional stability in her foot and ankle  (Fig. 3).

Discussion

Surgical correction in chronic foot and ankle deformities, whether diabetic or nondiabetic, remains a formidable challenge due to the persistently high incidence of complications.^6,7

Based on the way of case progression and clear clinical findings, the underlying cause of this clinical condition is possibly induced by longstanding posterior tibial tendon dysfunction (PTTD) ^5,8,9. However, PTTD has not been confirmed by magnetic resonance imaging. We opted not to explore PTTD through surgical means since it wouldn't influence our treatment strategy, and further tissue damage could hinder the already compromised skin's healing process.

Our patient had been living with a deformity for 5 years until undergoing surgical treatment, which aligns with the duration of a previously reported case.⁵  Altough Chan et al. ⁴ reported  that their patient had experienced medial subtalar dislocation and ankle injury 10 years prior to surgery, however, they do not specify when the irreversible subtalar dislocation occurred. We believe that our operative treatment plan would remain unchanged even if only a few years have passed since the onset of a subtalar dislocation.

The surgical treatment conducted in this case has not been previously documented. Tonogai et al.⁵ performed a similar operation, but without the mentioned talo-cuboid arthrodesis. We believe that increasing the contact surface area between the talus and the midfoot is crucial for the success of this surgical technique. As in the previous study, there was a residual postoperative flatfoot. However, our patient is satisfied with the surgical procedure and denies any pain while walking at the 1-year follow-up visit. Moreover, there is a high possibility that a triple arthrodesis, incorporating calcaneo-cuboid arthrodesis to address AAFD, may not yield the desired firmness to the foot following such an extended period of subtalar dislocation.

Chronic lateral subtalar dislocation, without additional comorbidities, can be managed with a single-stage operative procedure. Incorporating a talo-cuboid arthrodesis is a crucial step in ensuring a stable operative outcome. The duration of the longstanding subtalar dislocation appears to have no significant impact on the operative outcome, as long as the soft tissue and skin coverage are manageable.

Acknowledgments

The authors report no benefits, grants or assistance from any party.

Ethical Approval

The study was approved by the research ethics committee of the Clinical center of Vojvodina

Informed Consent

Proper informed consent was obtained, and the patient was thoroughly explained on the procedure prior to commencing treatment.

About the authors

Miodrag Vranješ

Author for correspondence.
Email: miodrag.vranjes@mf.uns.ac.rs
ORCID iD: 0000-0002-0642-4942
Serbia

Kristian Dudaš

Email: kristiand82@gmail.com
Serbia

Predrag Rašović

Email: predrag.rasovic@mf.uns.ac.rs

References

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