Calcaneum tuberculosis – A rare entity: Case report and review of literature

INTRODUCTION

In the era of modern medicine, infections like tuberculosis (TB) remain a major concern in developing countries like India. TB can be seen in the skeletal system, tissues, and visceral organs. The prevalence rate of TB in the Indian population is 193/100,000.^[1] TB involving the skeletal system accounts for only 2% of all cases affected by TB,^[2] whereas the involvement of foot and ankle joints accounts for approximately 10% of the skeletal involvement.^[3] Of all the foot bones, the calcaneum is the most commonly involved, followed by the talus, distal end of the first metatarsal, cuneiform, navicular, and cuboid bone involved in TB of osteoarticular origin.^[4-6]

Calcaneum TB is a rare entity. It does not present with typical features of TB and can be confused with other pathologies affecting the heel. A rare occurrence of TB of the foot and lack of awareness among orthopedic surgeons lead to difficulty and delay in diagnosis, which can further lead to patient disability in terms of function and poor clinical outcomes.^[7]

Very few studies, including case reports and case studies, describe the presentation of foot and ankle TB and its management are present. We report a case with an unusual presentation of calcaneal TB without any other bony involvement. We also performed a literature review to study the involvement of calcaneum in foot and ankle TB, as well as the different treatment modalities.

In most cases of foot and ankle TB, medical management has a key role, whereas surgery is required in cases not responding to anti-Koch treatment (AKT) for tissue collection, deformity correction, pain relief, and reconstruction of the joint.^[8]

CASE REPORT

A 23-year-old female presented to the orthopedic clinic complaining of pain and swelling around the left heel and posterior aspect of the ankle for 3 months. Her examination showed minimal swelling around the posterior aspect of the ankle with a normal overlying skin and tenderness on deep pressure. There were no local (hotness and sinus formation) or systemic features (weight loss and loss of appetite) of TB and no lymphadenopathy of inguinal lymph nodes.

Hematological parameters showed lymphocytosis and raised erythrocyte sedimentation rate. A radiograph of the calcaneum showed a lytic lesion in the posterosuperior aspect of the calcaneum [Figure 1]. Magnetic resonance imaging of the left foot [Figure 2] was advised, which showed the presence of a lesion around the posterior-superior aspect of the calcaneum along with the involvement of retro-calcaneal bursa with the size of the lesion around 21 × 37 × 42 mm and altered signal intensity on both T1- and T2-weighted images suggestive of mainly infective pathology. Proper consent before the biopsy was taken from the patient and her relatives. In the present case, an incisional biopsy was performed, followed by en bloc excision.

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Figure 1:

Lateral radiograph of ankle suggestive of lesion around posterior-superior aspect of calcaneum.

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Figure 2:

Sagittal section of magnetic resonance imaging ankle suggestive of bony and soft tissue involeument.

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Then, histopathological examination (HPE) report suggested granuloma formation with caseous necrosis and cartridge-based nucleic acid amplification test (CBNAAT) was also positive for mycobacterial TB infection.

The calcaneal TB in this patient belonged to “Stage-2” as per the Classification of Foot and Ankle TB by Martini et al.^[9]

Stage Feature

1. No bony changes and localized osteoporosis

2. Cavity formation or bony destruction within the bone

3. Complete bony involvement without major joint involvement

4. Massive destruction

After that, an excisional biopsy was performed for the lesion affecting the calcaneum using a posterior-lateral approach around the ankle. Intraoperatively, lysis around the posterosuperior aspect of the calcaneum was seen, along with the involvement of retro-calcaneal bursa. Then, curettage of the calcaneum was done along with the retrocalcaneal bursa, and the wound was closed in layers. Next, a left below-the-knee plaster was applied for 4 weeks followed by partial weight-bearing after 4 weeks and then complete weight-bearing from the 8^th week. The sample was sent for HPE, CBNAAT, and Ziehl-Nelson (ZN) staining. Superficial infection was seen postoperatively, which was managed with regular dressing under antibiotic (Tablet. Cefuroxime, 500 mg, bd and linezolid, 600 mg, bd orally for 2 weeks) cover. HPE showed caseating tubercular granuloma [Figure 3], the ZN stain showed the presence of tubercular bacilli and CBNAAT was positive.

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Figure 3:

Histopathological examination showing caseating tubercular granuloma.

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After these results, AKT was started (For the first 2 months, isoniazid [5 mg/kg], rifampicin [10 mg/kg], pyrazinamide [15 mg/kg], and ethambutol [25 mg/kg], for the next 10 months only isoniazid and rifampicin). The patient was called for regular follow-up, which consisted of radiological evaluation [Figure 4] and hematological investigations. Weight-bearing was allowed after 6 weeks. After 18 months of follow-up, it showed no signs of recurrence. Improvement in terms of clinical (pain, swelling, and activity of daily routine) and radiologically (for bone formation and no recurrence) was seen.

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Figure 4:

Lateral radiograph of ankle at 12^th follow-up.

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DISCUSSION

In developing nations like India, infections like TB continue to be a major concern in the public health sector, leading to morbidity and mortality. Lungs are considered the most common organ affected by TB, but it also involves extra-pulmonary sites. Spine involvement is commonly seen when TB affects the skeletal system, whereas foot and ankle joint involvement is rare.^[10] Prompt diagnosis of infections like TB affecting bone and joints is of utmost importance as it leads to massive destruction, which leads to a disability affecting daily routine activities.

TB affecting the skeletal system is a paucibacillary type and rare presentation around the foot leads to delayed diagnosis and treatment.^[11] The disease usually starts from the cancellous part of the bone through direct inoculation or a hematogenous route.^[12] The order of involvement in skeletal TB is the dorsal spine, pelvic bones, femur and hip joint, tibia and knee, and ribs, in that order. The elbow, ankle, and foot constitute 2% each and multiple-site involvement is merely 3%.^[13,14]

Of all the bones of the foot, the calcaneum is the most commonly affected by TB, as seen in the literature, also supported by the study conducted by Kumar et al., which showed that out of 312 cases of foot TB, 88 (28.2%) cases had calcaneum involvement.^[4] A possible explanation is the larger bone size and the fact that it is the commonly injured foot bone by trauma.^[7,15] Tubercular infections of the foot can present with pain, swelling, discharging sinus, difficulty in weight bearing, heel-up signs, and symptoms like evening rise of temperature, night sweats, and weight and appetite loss.^[16]

The Google Scholar and PubMed data were searched for TB around the foot and ankle by two authors (NB and MS) with keywords – “Tuberculosis,” “Calcaneum,” “Foot,” and “ankle.” We included the search results for the past 10 years (2013–2022) and included all type of studies. Out of the results searched, we found ten relevant studies with the involvement of calcaneum.

The literature review of the past 10 years shows that Male: Female is 3:1.^[4,12,17-24] The disease duration varied from 1 to 24 months. The side involvement does not show much difference in involvement with Left: Right; 1.27:1. All the studies tabulated above show the involvement of the calcaneal body mainly and in few cases, show the involvement of the anterior process (three patients) and^[12] tuberosity (seven patients).^[19,20,22] The most common symptoms noted were pain with weight bearing and swelling.

In the present case, only painful swelling was seen around the foot and ankle, along with heel-up signs on prolonged walking.^[25] Intraoperatively, sequestrum was found in the present case and similar findings have been reported in a study on foot TB by Dhillon and Nagi.^[11] In contrast, a study by Mittal et al.^[15] showed no sequestrum in calcaneum TB. Calcaneum TB can be confused with heel pathologies such as pyogenic and fungal infections, Haglund’s deformity (posterosuperior tuberosity prominence as a result of overuse or footwear), and lytic lesions of bone.^[17]

For differentiating TB from pyogenic infections affecting the foot and ankle, as a result of the absence of proteolytic enzymes, there is a preservation of joint space in TB compared to pyogenic infections. Second, the Phemister triad (peripheral bony erosion, decreased joint space and juxta-articular osteoporosis), is not commonly seen in calcaneal TB.^[10,26]

Dhillon et al.^[7] study on foot TB showed that out of 92 cases, the cystic form was seen in 24 cases. In contrast, a study by Mittal et al.^[15] showed the presence of the cystic form in only 15 cases out of 44. Articular involvement was seen as a common finding whenever a delay in diagnosis was present. While treating lytic lesions of bone, other infections and tumors are considered a differential diagnosis, so it is important to do a detailed clinical and radiological evaluation followed by a biopsy of the lesions for a definitive diagnosis.

The rare occurrence of TB in the foot and ankle and lack of associated symptoms such as evening temperature rise, appetite and weight loss, night sweats, and radiographic appearance make a definitive diagnosis difficult.^[11,27,28] TB is of a paucibacillary nature when bone and joints are involved; therefore, more than one diagnostic modality is required for diagnosis.

To date, many diagnostic tests are available. Still, none of them is highly sensitive and specific for diagnosing skeletal TB, as stated by Dhillon et al.^[7] Therefore, the present case report confirmed the diagnosis from all the available tests.

The improvement in anti-TB drugs showed clinical improvement, and 12–18 months of AKT is given for TB of osteoarticular origin. However, in the presentation where TB is seen in some unfamiliar locations, AKT can be continued for a few months under strict supervision.^[29,30] 12 months of AKT is recommended. With the short duration of treatment, recurrence is commonly due to the paucibacillary nature of skeletal TB, as some of the organisms may remain dormant, leading to resistance to AKT.^[31]

With improvement in AKT, the need for a surgical procedure is beneficial for diagnosis when in doubt, lesions not responding to medical treatment or cases with deformities, arthrodesis, and neurological involvement in the tubercular spine.^[31]

CONCLUSION

AKT plays a crucial role in managing TB affecting the foot and ankle. Therefore, surgery is usually reserved for cases with unclear diagnosis, pain, or when not responding to medical treatment and deformity correction.

AUTHORS CONTRIBUTIONS

NB convicted the idea for the case report and PC and JC wrote the case report. Finally, the manuscript was reviewed by NB, MS, and MB. All authors have critically reviewed and approved the final draft and are responsible for the manuscript’s content and similarity index.