An Unusual Cause of Ankle Pain in a Pediatric Patient – Isolated Transient Bone Marrow Edema of the Talus - Case Report and Review of Literature

INTRODUCTION

Transient osteoporosis of the talus is an uncommon condition of unknown etiology that is characterized clinically by ankle pain without a history of trauma. This is very difficult to distinguish from osteonecrosis, stress fracture, reflex sympathetic dystrophy, infection, or tumor. We present a case of isolated transient bone marrow edema of the talus in a pediatric patient which is the youngest described in the literature.

CASE REPORT

A 7-year-old child presented to the outpatient department of the orthopedic clinic with complaints of pain in the ankle and foot region. The pain was insidious in onset, dull aching in nature without any associated swelling. Pain score was 6 out of 10 by visual analog scale. There was no history of trauma. Symptoms were relieved by anti-inflammatory and rest. Clinically, he had antalgic gait. Blood investigations (including full blood count, ESR (erythrocyte sedimentation rate), and C-reactive protein) and radiographs of the ankle were unremarkable. Magnetic resonance imaging (MRI) revealed diffuse low signal on T1 and increased signal intensity on T2/ STIR (Short tau inversion recovery) of the entire talus and a small tibiotalar joint effusion. The marrow signal in the rest of the bones was normal. Articular cartilage, especially of the tibiotalar joint was preserved [Figure 1]. He was managed conservatively with analgesics and anti-inflammatories. There was complete resolution of clinical symptoms at 4 months.

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Figure 1:

T1 sag (a), STIR sag (b), STIR axial (c), and STIR coronal (d) showing marked T1 low signal and T2 high signal involving the entire talus.

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DISCUSSION

Transient osteoporosis syndrome, alternatively transient bone marrow edema, is defined as self-limiting, painful osteopenia of the involved area with unknown etiology.^[1] It was first described in the hip during pregnancy by Curtiss et al.^[2] Soon afterward, a migratory and recurrent type of transient osteoporosis was described by Duncan et al. who performed a biopsy which showed decalcified trabecular bone.^[3] Although the hip joint is by far the most common involved location,^[4] there are reports of transient bone marrow edema involving the foot. Isolated involvement of the talus is sparse, particularly in the pediatric population.^[5] Calvo et al. reported four cases of bone marrow edema of the foot, two of them showed involvement of the talus.^[6] Judd et al. reported a case of isolated involvement of the talus in 2000.^[7] Radke et al. studied ten patients with foot bones edema, eight of them involved the talus.^[8] Shariff et al. studied ten cases of transient osteoporosis of the foot, in which talus was involved in seven of them.^[9] Albrudeni had reported a case of transient osteoporosis of talus in a 54-year-old male.^[10]

The diagnosis of transient osteoporosis of the talus is essentially by exclusion with a wide range of differentials as previously discussed.^[9] Clinical presentation was similar in most of the cases as a sudden onset of progressive ankle pain without a history of trauma.^[8,9] MR imaging is always the key for the diagnosis of transient osteoporosis, especially with unremarkable radiographs. MRI finding in our case was diffuse T2 high signal with corresponding low signal on T1 of the entire talus and was consistent with the MRI findings of five cases of foot transient bone marrow edema reported by Calvo et al.^[6]

Treatment has been discussed in the literature to a much lesser extent compared to the transient osteoporosis of the hip and knee. Most of these cases are managed non-operatively with non weight bearing ambulation and analgesia. Some authors suggested a protected weight-bearing in a pneumatic boot for 8 weeks coupled with administration of bisphosphonates.^[11] The addition of bisphosphonates reduces the average time of resolution of symptoms from 25.6 weeks down to 24 weeks for oral bisphosphonates and to 13.8 weeks for intravenous bisphosphonates.^[11] Other treatments have been described include surgical core decompression^[6,8] and intravenous prostaglandin I2 analog (Iloprost).^[12,13] Recurrence of transient osteoporosis of the foot has been reported to be as high as 44% at an average follow-up of 5.75 years.^[10]

The differential diagnosis of TBME (Transient bone marrow edema) includes avascular necrosis, reflex sympathetic dystrophy, stress fracture, and osteomyelitis.

CONCLUSION

Isolated transient bone marrow edema of talus in the pediatric population is extremely rare with a non-specific clinical presentation and a wide differential diagnosis. MRI is the gold standard for diagnosis.