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Osteomyelitis of the Mandibular Coronoid Process Mimicking a Temporomandibular Joint Disorder: A Case Report
J Oral Med Pain 2024;49:35-39
Published online June 30, 2024;
© 2024 Korean Academy of Orofacial Pain and Oral Medicine

Jeong Yeop Chun1│Young Joo Shim1,2

1Department of Oral Medicine, Wonkwang University Daejeon Dental Hospital, Daejeon, Korea
2Department of Oral Medicine, Institute of Wonkwang Dental Research, College of Dentistry, Wonkwang University, Iksan, Korea
Correspondence to: Young Joo Shim
Department of Oral Medicine, Wonkwang University Daejeon Dental Hospital, 77 Dunsan-ro, Seo-gu, Daejeon 35233, Korea
Received May 24, 2024; Revised June 12, 2024; Accepted June 13, 2024.
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Osteomyelitis of the jaw is an inflammatory process of the bone marrow that is caused by odontogenic local infection and trauma such as tooth extraction and fractures in the oral and maxillofacial region. The clinical signs include pain, swelling, pus formation, and limited mouth opening. Chronic osteomyelitis presents a diagnostic challenge because of the variability of symptoms across different disease stages and varying health conditions of the patients. This report presents a case of osteomyelitis that was misdiagnosed as a temporomandibular joint disorder (TMD) after tooth extraction. The patient was treated for inflammation after tooth extraction in the early stage; however, as the osteomyelitis progressed chronically, symptoms mimicked those of a TMD. The patient was finally diagnosed with osteomyelitis 6 months after tooth extraction. A review of this case and relevant literature revealed the necessity for a differential diagnosis of chronic osteomyelitis that mimics TMD symptoms.
Keywords : Differential diagnosis; Osteomyelitis; Temporomandibular joint disorders; Tooth extraction

Osteomyelitis is an inflammatory disease that involves the destruction of bone tissue caused by infectious microorganisms [1]. It can affect various parts of the bone, including the bone marrow, periosteum, cortex, and surrounding soft tissues. The inflammation can be caused by hematogenous spread or local infection. Most osteomyelitis cases are typically attributed to odontogenic infections from the infected pulp or periodontal tissue and trauma such as tooth extraction and jaw fractures [2-4].

The clinical manifestations of osteomyelitis include fever, pain, swelling, purulent discharge, limited mouth opening, and necrotic bone exposure. However, specific symptoms may vary depending on the disease stage and condition of the patient. This can result in misdiagnosis and treatment delay [5]. The differentiation between osteomyelitis and temporomandibular joint (TMJ) disorders (TMDs) can be challenging when inflammation affects the TMJ and masticatory muscles [6-8].

Herein, we present a case of chronic osteomyelitis that was misdiagnosed as TMD after tooth extraction. The patient was initially treated for post-extraction inflammation but subsequently developed chronic osteomyelitis and exhibited symptoms consistent with a TMD. The case was analyzed according to symptom presentation, and the relevant literature was reviewed to assist in the differential diagnosis of osteomyelitis from TMD.

This study was conducted using a retrospective medical record review and was approved by the Public Institutional Review Board (IRB) of the Ministry of Health and Welfare (IRB no. P01-202403-01-010). The IRB waived the need for informed consent from the patient.


A 50-year-old male patient with no systemic diseases was referred to the Department of Oral Medicine of Wonkwang University Daejeon Dental Hospital, from the Department of Oral and Maxillofacial Surgery (OMS) of the same hospital for pain and swelling in the right masseter region that developed 13 weeks after the extraction of the impacted right mandibular third molar (Fig. 1A).

After the extraction of the impacted right mandibular third molar at the Department of OMS, no clinical abnormalities or discomfort were observed. However, the patient returned 5 weeks after the extraction, reporting pain in the right mandible. The panoramic radiograph revealed no abnormalities. The patient reported temporary pain relief after the administration of the oral nonsteroidal anti-inflammatory drug (NSAID) loxoprofen and antibiotic cefaclor. Three weeks later (8 weeks after extraction), the patient returned with severe right mandibular pain. Surgical debridement and a 7-day antibiotic treatment were performed. Granulation tissue was observed in the extraction socket. The patient returned 10 weeks after extraction with persistent pain, swelling on the right cheek, and limited mouth opening. Panoramic radiograph did not indicate inflammation; however, clinically, tenderness was noted upon palpation of the right masseter, temporalis, and TMJ areas. The oral and maxillofacial surgeon suspected that the symptoms were indicative of right masseter myalgia and thus prescribed aceclofenac and tizanidine for 21 days. Despite the lack of improvement in symptoms, the patient was referred to the Department of Oral Medicine for TMD evaluation at 13 weeks after extraction. The patient reported spontaneous pain with a numerical rating scale (NRS) of 6 in the right masseter area and right TMJ, which was exacerbated by chewing and mouth opening. A clinical examination revealed a limited maximum unassisted opening of 34 mm and a maximum assisted opening of 38 mm and pain in the right masseter area, which was swelling slightly. A panoramic radiograph revealed unhealed extraction sockets of the right mandibular third molar (Fig. 1B). The lack of improvement after surgical debridement and antibiotic treatment in the Department of OMS, absence of oral fistula formation, and absence of pus discharge led to the tentative diagnosis of local myalgia and arthralgia. Behavioral therapy, physiotherapy including spray and stretch technique, and pharmacological therapy with dexibuprofen and cyclobenzaprine were conducted over 3 weeks. The pain reduced to an NRS of 2; however, swelling and limited mouth opening persisted, and a small fistula was observed in the distobuccal gingival area of the right mandibular second molar without pus discharge. A magnetic resonance image (MRI) was ordered to differentiate a masticatory fascial space abscess from TMD. Eighteen weeks after tooth extraction, the maximum unassisted and assisted mouth opening values were 42 and 45 mm, respectively. The pain and swelling had decreased. However, the MRI revealed a high-intensity lesion surrounding the right mandibular coronoid process suggestive of osteomyelitis or a malignant lesion (Fig. 2A). The patient was referred to the Department of OMS for a reevaluation for osteomyelitis.

At the Department of OMS, computed tomography (CT) demonstrated a permeative pattern of bone destruction at the right mandibular coronoid process with mild swelling and absence of abscess formation in the adjacent soft tissue (Fig. 2B). This finding led to the provisional diagnosis of osteomyelitis of the mandibular coronoid process, with a less probable diagnosis of a primary bone tumor. Surgery under general anesthesia was performed 6 months after the extraction. Histopathological examination revealed chronic inflammation with bone marrow fibrosis and necrotic bone, thereby confirming the clinical diagnosis of chronic osteomyelitis (Fig. 3). The patient recovered well, and the treatment was terminated 1 month after the surgery.


Osteomyelitis is classified into acute osteomyelitis (AO), secondary chronic osteomyelitis (SCO), and primary chronic osteomyelitis (PCO) based on the clinical presentation, disease course, and radiological features [9]. AO is an acute onset of osteomyelitis accompanied by deep penetration of bacterial pathogens within the medullary and cortical bone. AO persisting for >4 weeks will progress to SCO. AO and SCO are regarded as the same pathological entity at different stages of their clinical presentation. PCO is a chronic osteomyelitis that has not undergone an acute phase and has not been caused by a definitive initiating event. It is characterized by nonsuppurative chronic inflammation of the jaw bone without pus formation, development of extra- or intraoral fistula, or presence of sequestration. Episodic attacks of varying intensity may last from days to weeks, with remission periods in between. During the active phase, patients may experience symptoms ranging from dull to severe pain, limited mouth opening, myofascial pain, and variable swelling. In this case, the symptoms of osteomyelitis were similar to those of PCO; however, the patient had a history of tooth extraction. Untreated or inadequately treated osteomyelitis can progress to nonsuppurative SCO [10].

OA symptoms are variable but frequently include pain, swelling, abscess formation, and limited mouth opening in >50% of cases [5]. SCO symptoms are usually less extensive than AO. The intense pain in the acute stage is replaced by a more dull pain, and painful swelling subsides by a harder tenderness caused by periosteal reaction. Pain, swelling, and abscess formation were the most common symptoms of both AO and SCO [9]. Restricted mouth opening was observed in 50% of cases in AO and 20.7% in SCO [9]. The patient exhibited more pronounced symptoms, including swelling and a restricted mouth opening at a later disease stage. Furthermore, no abscess formation was found. These points are the reasons why the final diagnosis has been delayed.

Osteomyelitis can cause pain and limited mouth opening in the TMJ area through direct tissue inflammation and indirect central sensitization. Inflammation spreads to the surrounding TMJ area and masticatory muscles, and pain and mouth opening limitation can occur. The other mechanism is a central excitatory effect. Musculoskeletal pain is classified as deep somatic pain. Persistent deep somatic pain can exhibit central excitatory effect, such as referred pain and protective co-contraction [11]. SCO is a deep somatic pain that can exhibit central excitatory effects. The patient exhibited pain in the TMJ, masseter muscle region, preauricular area, and limited mouth opening. These characteristics are consistent with those observed in TMD.

The clinical and radiological signs of SCO exhibit similarities with those of malignant tumors complicated by secondary bone infection. Thus, a persistent bone infection could give rise to a malignant neoplasm through the neoplastic conversion of the infected tissue [12]. In this case, the MRI indicated the possibility of a bone tumor. Subsequently, a biopsy was performed, which confirmed osteomyelitis.

If the initial treatment is unsuccessful, the diagnosis needs to be reevaluated. Misdiagnosis leads to a delay in appropriate treatment, and the patient may undergo extensive and invasive procedure such as surgery. When chronic osteomyelitis is suspected, it must be differentiated from other diseases such as TMD and malignancy. This can be achieved by additional diagnostic tests such as imaging and laboratory tests. Imaging options include panoramic radiographs, radionuclide scintigraphy, CT, and MRI [13]. Panoramic radiography has a limitation in that osteomyelitis can be detected at a stage where bone resorption has reached 30%–50% of the affected bone, which can take 8 days to 3 weeks from symptom onset [14]. Radionuclide scintigraphy, utilizing radioactive isotopes to detect inflammation or infection, can identify affected areas as early as 2 to 3 days after symptom onset [15]. CT can reveal early cancellous bone decalcification in AO, and contrasted CT makes it easier to observe swelling and pathological conditions in the surrounding soft tissues of the mandible [13]. In MRI, inflammation and bone marrow fibrosis replace the fat content with water in the affected bone areas, leading to lower signal intensity in T1-weighted images and higher signal intensity in T2-weighted images in AO. As AO progresses to SCO, the signal intensity appears weaker in both T1- and T2-weighted images [16]. CT and MRI show high sensitivity and specificity in defecting osteomyelitis. Nevertheless, MRI is recommended for differentiating AO from SCO and distinguishing bone tumors, soft tissue diseases, and intraarticular TMDs such as disc displacement without reduction [16]. Laboratory tests can also assist in the diagnosis of osteomyelitis, such as serum inflammatory markers such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). They are regarded as inflammation markers [17]. A total of 66.6% of AO cases exhibited high CRP levels, and 82.6% exhibited elevated ESR levels. In SCO, the CRP level was high in 50.8% of cases, and ESR was high in 56.5% of cases [9]. CRP levels returned to the normal range within 7 days, whereas ESR could take up to 3 months to normalize [16]. Thus, these markers can be used to assess the efficacy of osteomyelitis treatment.

In conclusion, chronic osteomyelitis may present with symptoms that resemble TMDs, including pain and restricted mouth opening in the TMJ area and masticatory muscle region. If the initial treatment is unsuccessful, the diagnosis should be reassessed. Thus, additional diagnostic examinations should be conducted.


No potential conflict of interest relevant to this article was reported.


The datasets used in this study are available from the corresponding author upon reasonable request.




Conceptualization: YJS, JYC. Data curation: JYC. Formal analysis: YJS. Methodology: JYC, YJS. Visualization: JYC, YJS. Writing original draft: JYC, YJS. Writing review & editing: YJS.

Fig. 1. Panoramic radiography. (A) The impacted right mandibular third molar at the first visit to the Department of Oral and Maxillofacial Surgery. (B) The extracted socket at the first visit to the Department of Oral Medicine 13 weeks after the extraction. The anterior border of the mandibular ramus exhibited a blurred appearance (arrow), although this was not identified by the physician.
Fig. 2. Magnetic resonance image (MRI) and computed tomography (CT). (A) In the T2-weighted MRI, a soft tissue mass (arrow) was observed in the region of the right mandibular coronoid process, and inflammatory change of near the masticatory muscle was observed. (B) A CT revealed permeative bone destruction of the right mandibular coronoid process with thin cortical outline (dotted arrows) and mild swelling and enhancement of the surrounding soft tissue.
Fig. 3. Histopathologic examinations of a biopsy specimen of the right mandibular coronoid process, with H&E staining (magnifications: A, ×40; B, ×200). (A) Empty osteocyte lacunae (arrows) in the bone tissue, (B) formation of collagen fibers (dotted arrow), and absence of neutrophils indicate a nonsuppurative inflammatory condition.
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