Osteoid Osteoma of the Proximal Phalanx of the Great Toe in a 13-Year-Old Female Patient

Abstract

Osteoid osteoma (OO) is a benign osteoblastic bone tumor typically involving the diaphysis or metaphysis in long tubular bones. OO in phalanges of the great toe has been rarely reported, and it is often challenging to differentiate with subacute osteomyelitis, bone abscess, or osteoblastoma. This case report describes an uncommon case of a 13-year-old female patient with subperiosteal OO in the proximal phalanx of the great toe. The atypical location of OO should be familiarized to include appropriate differential diagnosis and to ensure accurate diagnosis by radiologic evaluations. Surgical excision remains the benchmark for the treatment of OO with its advantages on direct visualization and histologic confirmation for the diagnosis.

Osteoid osteoma (OO), a benign osteoblastic bone tumor typically involving the diaphysis or metaphysis of long tubular bones such as the femur or tibia, is responsible for approximately 10% of all benign bone tumors.¹ OO mostly occurs in the second and third decades of life with male predilection. OO in phalanges of the great toe has been rarely reported in the previous literature to the best of our knowledge, and it is often challenging to differentiate with subacute osteomyelitis, bone abscess, or osteoblastoma.² In this report, we present an uncommon case of a 13-year-old female patient with subperiosteal OO in the proximal phalanx of the great toe.

Case Report

A 13-year-old female patient was admitted to the department of orthopaedic surgery outpatient clinic with a chief complaint of recurring swelling, burning sensation, and focal tenderness at the right great toe for the past 12 months with no history of trauma. Her symptoms had been well-controlled by NSAIDs but reappeared 4 months ago. The pain was more severe at night after long periods of walking or sports activities.

The physical examination revealed a slightly swollen great toe with focal tenderness at the interphalangeal joint area of the plantar aspect of the great toe. The radiographs showed a 4-mm, round, radiolucent lesion with central mineralization and rim sclerosis at the head of the proximal phalanx of the great toe (Figure 1). The complete blood analysis indicated no remarkable findings. With a clinical suspicion of subacute osteomyelitis, enhanced MRI indicated heterogeneously low signal intensity on T1-weighted images and low signal intensity in the center and higher signal intensity in the periphery on T2-weighted images at the same lesion seen on the simple radiograph. In addition, there were diffuse bone marrow edema and periosteal inflammatory change around the bony lesion along with thin enhancement at the periphery of the lesion (Figure 2). CT revealed a radiolucent central nidus surrounded by a sclerotic rim (Figure 3). Both MRI and CT findings were consistent with the diagnosis of OO in the head of the proximal phalanx of the great toe. After nonsurgical management with pain medication for 2 months, the patient underwent surgical excision because of recurring pain.

Figure 1.

Simple anterioposterior (A) and lateral (B) radiographs of the right foot showing a 4-mm, round, radiolucent lesion with central mineralization and rim sclerosis at the head of the proximal phalanx in the great toe.

Figure 2.

Gadolinium-enhanced MR T1-weighted axial images indicating a 4-mm bony lesion with high signal intensity in the periphery and low signal intensity at the center along with diffuse bone marrow edema and periosteal inflammatory changes in the proximal phalanx of the great toe.

Figure 3.

Computed tomography axial (A) and coronal (B) images showing a radiolucent central nidus surrounded by sclerotic rim in the head of the proximal phalanx of the great toe.

Under general anesthesia, the patient was positioned prone for better access to the plantar location of OO. A longitudinal incision was made on the plantar aspect of the great toe, and after retracting the flexor hallucis longus tendon laterally, the subperiosteally located bony lesion was visible. Intraoperative localization of the nidus was rather direct and simple because of its juxtacortical and subperiosteal location without additional damages to the surrounding osseous structure. A 5-millimeter nidus was completely removed with en bloc surgical resection with curettage and sent for microbiologic and histopathologic analyses (Figure 4). The immediate postoperative radiograph showed complete excision of the nidus in the proximal phalanx of the great toe (Figure 5).

Figure 4.

Intraoperative clinical photographs showing a grayish red and gritty lesion in the head of the proximal phalanx of the great toe (A). Postexcision intraoperative clinical photographs indicating a complete removal of the bone tumor after surgical excision and curettage (B) and the resected bone tumor specimen (C).

Figure 5.

Immediate postoperative radiograph indicating complete resection of the bone tumor in the proximal phalanx of the great toe.

Histopathologic examination revealed OO with typical morphologic features of hypercellular central nidus with vascular fibrous tissues, surrounded by osteoblastic rims (Figure 6). Microbiologic culture showed no pathogenic organisms present. The patient's symptoms remitted immediately after the surgery, and the patient postoperatively began weight-bearing with postoperative flat-soled shoes for 2 weeks. One year after the surgical resection, the follow-up radiograph indicated no recurrence and the patient remained symptom-free (Figure 7).

Figure 6.

An osteoid osteoma nidus and the normal bone structures are shown in the permanent biopsy of the bone tumor. The hematoxylin and eosin–stained section showing the hypercellular nidus with vascular fibrous tissues and prominent osteoblastic rims (magnification, ×400)

Figure 7.

Follow-up radiograph obtained at 1 year after the surgical excision revealed no signs of recurrence in the proximal phalanx of the great toe.

Discussion

OO typically occurs in the long trabecular bones, but is rarely reported in the foot and hallux with incidence rates of less than 2%, including only 17 cases in the great toes and only one pediatric case among them³ (Table 1). OO is radiographically classified based on axial distribution of tumor, proposed by Edeiken, classified OO as cortical, cancellous (or medullary), or subperiosteal origin.^4,5 While cortical origin comprises 75% of all OOs, subperiosteal OOs are the least common type, accounting for less than 5%. However, a study by Kayser et al⁵ proposed a hypothesis that all OOs arise from the subperiosteum and progressively migrate internally.

Table 1.

Summary of the Available Previous Literature on Osteoid Osteoma in the Great Toe⁹

Number	Author	Year	Sex	Age	Location	Treatment
1	Kahn et al8	1983	Female	32	Distal phalanx	Surgical excision
2	Alkalay et al9	1987	Male	22	Ossicle	Surgical excision
3	Mohr et al10	1990	Male	20	Distal phalanx	Surgical excision
4	Ekmekci et al11	2001	Female	29	Subungual	Surgical excision
5	Ozturk et al12	2008	Female	9	Distal phalanx	Surgical excision
6	Jowett et al13	2010	Female	20	Proximal phalanx, head	Surgical excision
7	Hattori et al14	2011	Male	22	Distal phalanx, shaft	Surgical excision
8	Turkmen et al2	2013	Male	23	Distal phalanx, shaft	Surgical excision
9	Mohsen et al15	2015	Female	32	Subungual	Surgical excision
10	Yamaga et al16	2015	Male	16	Distal phalanx	Surgical excision
11	Xarchas et al17	2017	Male	22	Distal phalanx	Surgical excision
12	Manae et al18	2017	Male	17	Distal phalanx, tip	Surgical excision
13	Torrent et al19	2017	Male	16	Proximal phalanx, condyle	Surgical excision with bone autograft
14	Hassini et al20	2019	Male	23	Sesamoid	Surgical excision
15	Trave et al21	2020	Female	20	Distal phalanx	Surgical excision
16	Basile et al6	2020	Female	27	Proximal phalanx, base	Surgical excision
17	Ozdemir et al22	2020	Female	46	Distal phalanx, shaft	Radiofrequency ablation

Characteristic clinical manifestations include intermittent pain predominating at night but easily relieved by NSAIDs. The pathophysiology of pain in OOs is due to the presence of nerve endings in the tumor and the high level of prostaglandin and prostacyclin in the nidus. Such high levels of prostaglandin E2 cause inflammatory reactions in the periphery of the tumor and vasodilation, causing bone marrow edema in surrounding tissues, both of which can be radiologically evidenced.^1,6

The time taken for the correct diagnosis of OO in the great toe is often delayed because of the rarity of the disease and variable radiologic imaging appearances depending on the disease progression. Therefore, the differential diagnosis of OO in the great toe includes subacute osteomyelitis, intraosseous abscess, osteoblastoma, stress fracture, hemangioma, and inclusion epidermoid cyst.^6,7 Among various diagnostic modalities including plain radiograph, bone scan, CT, and MRI, CT has preoperatively the greatest diagnostic values in demonstrating low-attenuation nidus with localized central calcification and peripheral rim sclerosis because OOs in small bones, unlike typical long bones, may present atypical radiologic presentations, such as medullary origin, absence of osteosclerosis, and multicentric nidi.^1,6 In this case, MRI was helpful to rule out infection and other OO-mimicking lesions, but the CT scan was integral in obtaining a better understanding of the osseous nature of OO in the unusual location.

The critical point from this case report is associated with clinical suspicion of OO and its differential diagnosis in the uncommon location. Table 1 summarizes the available literature on OOs occurring in the great toe in a chronological order, where its primary treatment modality was surgical excision in all cases.^{8,9,10,11,12,13,14,15,16,17,18,19,20,21,22} In addition to surgical excision of the OO, radiofrequency ablation (RFA) has shown clinically equivalent treatment results with advantages of a minimally invasive procedure, negligible postprocedural complications, low recurrence rates, and a shorter recovery time.²³ Intraoperative navigation-assisted or CT-assisted RFA is also an excellent noninvasive modality to accurately localize and ablate medullary OOs. However, the use of RFA is often limited when the location of OO is within 1 cm away from critical anatomical structures such as neurovascular structure and skin.²⁴ In this case, because the location of the nidus was just below the flexor tendon and near the skin and phalangeal neurovascular structures, the patient underwent en bloc surgical resection to prevent nerve damages and thermal burn from the RFA procedure. In addition, the localization of the nidus was not challenging because of its superficial location to the cortex, and en bloc excision under direct visualization was sufficient for the complete removal in this case.

Conclusion

In this article, we presented a rare example of juxta-articular and subperiosteal OO occurring in the head of the proximal phalanx of the great toe to the limited literature. The atypical location of OO should be familiarized to include appropriate differential diagnosis and to ensure accurate diagnosis by radiologic evaluations. Surgical excision remains the benchmark for the treatment of OO with its advantages on direct visualization and histologic confirmation for the diagnosis.