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National Journal of Maxillofacial Surgery
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Table of Contents
Year : 2021  |  Volume : 12  |  Issue : 2  |  Page : 276-279  

Management of a case of osteoma of coronoid: A rare case report

1 Department of Oral and Maxillofacial Surgery, JSS Dental College and Hospital, Mysore, Karnataka, India
2 Department of Oral and Maxillofacial Surgery, Kalinga Institute of Dental Sciences, Bhubaneswar, Odisha, India

Date of Submission26-Oct-2019
Date of Acceptance04-Aug-2020
Date of Web Publication15-Jul-2021

Correspondence Address:
Dr. Asutosh Das
Department of Oral and Maxillofacial Surgery, Kalinga Institute of Dental Sciences, Bhubaneswar, Odisha
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/njms.NJMS_68_19

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Coronoid process osteoma is an extremely unusual and slow growing tumor which causes functional limitations of the temporomandibular joint. Till december 2014 only 7 cases have been reported worldwide. This case report is about a 40 year old male patient with osteoma of left coronoid process. Treatment plan constitutes of surgical resection of the mass and post operative physiotherapy.

Keywords: Coronoidectomy, osteoma, pseudoankylosis

How to cite this article:
Saikrishna D, Das A, Jha C. Management of a case of osteoma of coronoid: A rare case report. Natl J Maxillofac Surg 2021;12:276-9

How to cite this URL:
Saikrishna D, Das A, Jha C. Management of a case of osteoma of coronoid: A rare case report. Natl J Maxillofac Surg [serial online] 2021 [cited 2021 Dec 5];12:276-9. Available from: https://www.njms.in/text.asp?2021/12/2/276/321455

   Introduction Top

Extrinsic joint pathologies constitute one of the chief causes of restricted mandibular movements. Trauma, infection, ankylosis, and arthritis are few etiological factors that lead to progressive functional limitation of the temporomandibular joint. Coronoid process osteoma is an extremely unusual and slow-growing tumor that can lead to restriction of mandibular movements. The first case of compact osteoma of the coronoid process of mandible was reported by Lewars in 1959. Osteomas comprise histologically normal membranous bone varying from insignificant thickening to large masses affecting the skeletal system largely. They are predominantly restricted to the craniofacial skeleton,[1] and the most common sites include the paranasal sinuses and the mandible. True osteomas of the jaws may arise centrally or subperiosteally or in a peripheral location and might be either cancellous or compact in nature.[2],[3] The cause of osteoma in the maxillofacial region is reported to be reactive bone hyperplasia or advanced bone ossification. Coronoid osteomas are largely asymptomatic and are nontender until their size and position incommodes with functioning. The present report describes one such case. Aspects dealing with the differential diagnosis, treatment, surgical access, possible complications, and outcomes have been elucidated. Until December 2014, only seven authors have described this rare entity in scientific literature [Table 1].
Table 1: Courtesy: Table form of published cases on coronoid osteoma till date, da Costa Araújo et al.[7]

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   Case Report Top

A 40-year-old male reported to us with a complaint of progressive restriction in mouth opening for 1 month. The restriction in mouth opening had gradually increased to the present state [Figure 1]a. There was no history of associated maxillofacial trauma, infections, or any surgical procedures. The patient presented with mild facial asymmetry toward the left with an accentuated prominence over the left malar region. Temporomandibular joint examination showed restriction of translatory and lateral excursive movements.
Figure 1: (a) Diminished preoperative mouth opening. (b) Intraoperative adequate mouth opening

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On intraoral examination, a tender, ill-defined bony mass could be palpated in the coronoid process of the ipsilateral side.

Noncontrast computed tomography (NCCT) face sections revealed a well-defined radiopaque lesion with a surrounding radiolucent rim, noted in relation to the lateral side of the left maxillary sinus and zygomatic buttress region [Figure 2]a. Sagittal section of the NCCT revealed an altered anatomy of the coronoid process having similar density to that of the normal bone with a radiopaque “horse head-” or “mushroom-”shaped mass encroaching the left infratemporal region [Figure 2]b. The axial section represented an oval mass impinging on the adjacent arch [Figure 2]c.
Figure 2: (a) Coronal section of computed tomography face suggestive of a round mass in the left malar region. (b) Sagittal section of noncontrast computed tomography face showing typical horsehead- or mushroom-shaped mass encroaching the left infratemporal region. Note the similarity in the density of the lesion to that of the normal bone. (c) Axial section of the noncontrast computed tomography face showing oval mass impinging on the adjacent arch of the left side

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On the basis of clinical and radiographic features, as well as the slow progressive nature, a provisional diagnosis of a benign osseous neoplasm of the coronoid process of the left side was given.

The procedure planned was left coronoidectomy under general anesthesia. The tumor mass was reached through hemicoronal approach along with lateral swing osteotomy of the left zygomatic arch. Osteotomy of the coronoid process and tumor mass was performed at the level of sigmoid notch.

Intraoperatively, the mouth opening improved and was recorded as 30 mm, following which contralateral coronoidectomy was carried out intraorally, thereby increasing the mouth opening to 45 mm. Zygomatic arch repositioning and stabilization was done using titanium miniplate and screws [Figure 1]b.

The resected bony mass had a mixed nodular and smooth surface, measuring about 4 cm × 3 cm × 2 cm [Figure 3].
Figure 3: Resected specimen

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Microscopic examination of the specimen revealed a dense lamellar bone with marrow space and trabeculae lined by periosteum. Unlike osteochondroma, it lacked the typical cartilaginous cap [Figure 4].
Figure 4: Dense lamellar bone with marrow space and trabeculae lined with periosteum can be seen under microscope

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The postoperative recovery was uneventful with no facial nerve deficits. No occlusal discrepancy was observed and the mouth opening was found to be 35 mm 1 month later. The patient was advised to continue aggressive physiotherapy and regular follow-up.

   Discussion Top

Osteoma is a benign tumor which arises from the proliferation of compact or cancellous bone, which leads to hypomobility of the mandible. It can reach a significant size, causing an increase in volume, facial asymmetry, limited mouth opening, and fracture of zygomatic complex in some cases. Central type, peripheral type, and extraskeletal type are the three variants based on the origin.[4] A central osteoma arises from the endosteum, while the periosteum gives rise to the peripheral variant. An extraskeletal soft-tissue osteoma is of muscular origin.[5] Coronoid osteomas lead to limitation of mandibular movements and might lead to pathological fractures of the zygomatic arch. Reports of pseudo-ankylosis are also present in such cases. They can occur at any age but are predominantly associated with young adult males. Osteoma is most common in the fourth and fifth decades, but lesions are reported from 10 to 79 years. They are usually solitary. However, Gardner's syndrome is associated with multiple such tumors.

Osteochondromas of the coronoid process have been reported in literature by Shackelford and Brown in 1943.[6]

The etiology is unknown, however it might be associated with aberrant activity of the surrounding periosteum. An endochondral ossification may occur around a foci of such metaplastic cartilage, leading to the formation of exostoses.

Another supporting theory is that it may arise post trauma, wherein a hematoma may undergo fibrosis and lead to the formation of chondrocytes. Histopathological evaluation of osteoma reveal absence of cartilaginous cap which can be attributed to shifting of the growth to the juxtaposition of new bone rather than that of endochondral ossification.

Coronoid hyperplasia can also be a striking differential to our diagnosis as it may occur as a reactive bone hyperplasia secondary to endocrine stimulus, trauma, increased temporalis activity, or genetic influences. Another differential to restricted mouth opening is Jacob's disease, which differs from the osteoid osteoma owing to the histopathological evidence of regions of endochondral ossifications enclosed by hyaline cartilage.[7]

Histopathological evaluation, therefore, is a key tool in establishing a diagnosis in such cases.

Kersher et al. reported a theory presuming that osteomas of the coronoid process are the sequelae of osteochondromas after total ossification of cartilage. Exhibition of cellular pleomorphism of chondrocytes and disturbances in endochondral ossification are suggestive of neoplastic nature. Hence, they have been correctly categorized as tumors by several authors.

Facial asymmetry is the most common presentation of such patients owing to the lack of other symptoms apart from functional limitations, if any. Continuous growth might push the cortices of zygoma, resulting in an evident malar bulge and leading to the resorption of zygoma, which is followed by remodeling into a state of pseudo-ankylosis, resulting in trismus.

The aim of treatment is to restore the function, that is, optimal mandibular movements and chewing. Depending on the size, location, and type of restriction, surgery can be performed using a submandibular, coronal, retromandibular, preauricular, or intraoral access. It may accompany myotomy of masseter and temporalis muscles to relieve the limited range of motion as the facial musculature gets adapted to the existing scenario. Surgical excision of the osseous mass is the preferred treatment for patients with functional impairment. The coronoid process can be approached extraorally, intraorally, or using a combination of both. However, extraoral approach is preferred for larger coronoid process lesions. Osteomas of the coronoid process have a satisfactory prognosis, with no recurrence. The procedure involved is carried out with utmost care to avoid severing of the facial nerve. The intraoral approach involves an incision from the superior limit of the coronoid process to the retromolar trigone region with exploration of the entire anterior mandibular ramus. This procedure offers safety in terms of associated nerve damages and extraoral scars. However, the accessibility is compromised.

Postoperative mouth opening exercises, physiotherapy, and regular follow-up of treated cases are advocated. The present report is a pursuit to draw the attention of clinicians to such rare cases, where trismus is among the clinical findings. Such a case, if diagnosed and managed effectively, will result in impressive functional and esthetic outcomes.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the legal guardian has given his consent for images and other clinical information to be reported in the journal. The guardian understands that names and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Manjunatha BS, Nagarajappa D. Osteoid osteoma. Indian J Dent Res 2009;20:514-5.  Back to cited text no. 1
[PUBMED]  [Full text]  
Kutluhan A, Salviz M, Bozdemir K, Değer HM, Culha I, Ozveren MF. Middle turbinate osteoma extending into anterior cranial fossa. Auris Nasus Larynx 2009;36:702-4.  Back to cited text no. 2
Ogbureke KU, Nashed MN, Ayoub AF. Huge peripheral osteoma of the mandible: A case report and review of the literature. Pathol Res Pract 2007;203:185-8.  Back to cited text no. 3
Frölich MA. Mandibular osteoma: A case of impossible rigid laryngoscopy. Anesthesiology 2000;92:261-2.  Back to cited text no. 4
Nah KS. Osteomas of the craniofacial region. Imaging Sci Dent 2011;41:107-13.  Back to cited text no. 5
Shackelford Rt, Brown WH. Restricted jaw motion due to osteochondroma of the coronoid process. J Bone Joint Surg Am 1949;31A: 107-14.  Back to cited text no. 6
da Costa Araújo FA, Melo Barbalho JC, de Farias ON Jr., de Vasconcellos RJ, do Egito Vasconcelos BC. Pseudo-ankylosis caused by osteoma of the coronoid process. Ann Maxillofac Surg 2014;4:208-10.  Back to cited text no. 7


  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1]


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