Usage of Hounsfield unit to differentiate idiopathic condylar resorption: a preliminary study

Background: The Hounsfield unit (HU) is a quantitative scale used to describe radiodensity in computed tomography (CT) scans. Since idiopathic condylar resorption (ICR) and temporomandibular joint osteoarthritis (TMJOA) involve destruction of bone and cartilage in the mandibular condyle, we hypothesized that HU values might be used to differentiate between the two conditions. This study aimed to evaluate the usefulness of HU values in the differential diagnosis of ICR and TMJOA. Methods: Twelve TMJOA and 9 ICR patients, and 11 healthy subjects were recruited as the TMJOA, ICR, and control groups, respectively. CT scans were performed, and HU values were measured in the region of interest (ROI) with 5 mm thickness along the Z-axis from superior condylar surfaces. HU distributions were then analyzed for each ROI. Results: Control and TMJOA patients were significantly older than those in the ICR group. Median HU values of the mandibular condyle did not differ significantly among the three groups. All groups showed a unimodal HU distribution peaking at 250–450 HU, while ICR condyles exhibited a tendency to have an additional peak at 1350–1500 HU. Compared to the control group, the HU distribution of the TMJOA and ICR condyles was significantly lower at 250–450 HU. After age adjustment, significant intergroup differences in the voxel ratio were noted at each HU level at 250–300, 300–350, 400–450, 1400–1450, and 1800–1850 HU. However, no significant differences in HU values were observed between the ICR and TMJOA groups. Conclusions: HU values and distributions of the mandibular condyle may be used to differentiate between the control group and the ICR and TMJOA groups. Further studies with a sufficient sample size are needed to confirm whether HU values and distribution could become important indicators for distinguishing between the TMJOA and ICR condyles.

Hounsfield unit; Computed tomography; Temporomandibular joint; Idiopathic condylar resorption

[1] Tanaka E. Etiology and diagnosis for idiopathic condylar resorption in growing adolescents. Journal of Clinical Medicine. 2023; 12: 6607.

[2] Tanaka E, Mercuri LG. Current status of the management of idiopathic condylar resorption/progressive condylar resorption—a scoping review. Journal of Clinical Medicine. 2024; 13: 3951.

[3] Arnett GW, Milam SB, Gottesman L. Progressive mandibular retrusion—idiopathic condylar resorption. Part I. American Journal of Orthodontics and Dentofacial Orthopedics. 1996; 110: 8–15.

[4] Nobrega MTC, Almeida FT, Friesen R, Davis C, Major PW. Idiopathic condylar resorption in adolescents: a scoping review. Journal of Oral Rehabilitation. 2024; 51: 1610–1620.

[5] Tanimoto K, Awada T, Onishi A, Kubo N, Asakawa Y, Kunimatsu R, et al. Characteristics of the maxillofacial morphology in patients with idiopathic mandibular condylar resorption. Journal of Clinical Medicine. 2022; 11: 952.

[6] Abe S, Kawano F, Matsuka Y, Masuda T, Okawa T, Tanaka E. Relationship between oral parafunctional and postural habits and the symptoms of temporomandibular disorders: a survey-based cross-sectional cohort study using propensity score matching analysis. Journal of Clinical Medicine. 2022; 11: 6311.

[7] Valesan LF, Da-Cas CD, Réus JC, Denardin ACS, Garanhani RR, Bonotto D, et al. Prevalence of temporomandibular joint disorders: a systematic review and meta-analysis. Clinical Oral Investigations. 2021; 25: 441–453.

[8] Da-Cas CD, Valesan LF, Nascimento LPD, Denardin ACS, Januzzi E, Fernandes G, et al. Risk factors for temporomandibular disorders: a systematic review of cohort studies. Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology. 2024; 138: 502–515.

[9] Levine ZH, Peskin AP, Holmgren AD, Garboczi EJ. Preliminary X-ray CT investigation to link Hounsfield unit measurements with the international system of units (SI). PLOS ONE. 2018; 13: e0208820.

[10] DenOtter TD, Schubert J. Hounsfield unit. StatPearls Publishing: Treasure Island (FL). 2025.

[11] Jayamani J, Osman ND, Tajuddin AA, Salehi Z, Ali MH, Abdul Aziz MZ. Determination of computed tomography number of high-density materials in 12-bit, 12-bit extended and 16-bit depth for dosimetric calculation in treatment planning system. Journal of Radiotherapy in Practice. 2019; 18: 285–294.

[12] Courtois EC, Ohnmeiss DD. Assessing bone quality in Hounsfield units using computed tomography: what value should be used to classify bone as normal or osteoporotic? European Spine Journal. 2025; 34: 493–497.

[13] Schiffman E, Ohrbach R, Truelove E, Look J, Anderson G, Goulet JP, et al. Diagnostic criteria for temporomandibular disorders (DC/TMD) for clinical and research applications: recommendations of the international RDC/TMD consortium network and orofacial pain special interest groupdagger. Journal of Oral & Facial Pain and Headache. 2014; 28: 6–27.

[14] Hatcher DC. Progressive condylar resorption: pathologic processes and imaging considerations. Seminars in Orthodontics. 2013; 19: 97–105.

[15] Fahey FH, Abramson ZR, Padwa BL, Zimmerman RE, Zurakowski D, Nissenbaum M, et al. Use of (99m)Tc-MDP SPECT for assessment of mandibular growth: development of normal values. European Journal of Nuclear Medicine and Molecular Imaging. 2010; 37: 1002–1010.

[16] Munakata K, Miyashita H, Nakahara T, Shiba H, Sugahara K, Katakuta A, et al. The use of SPECT/CT to access resorptive activity in mandibular condyles. International Journal of Oral and Maxillofacial Surgery. 2022; 51: 942–948.

[17] Riechmann M, Schmidt C, Ahlers MO, Feurer I, Kleinheinz J, Kolk A, et al. Controversial aspect of diagnostics and therapy of idiopathic condylar resorption: an analysis of evidence- and consensus-based recommendations based on an interdisciplinary guideline project. Journal of Clinical Medicine. 2023; 12: 4946.

[18] He Z, Ji H, Du W, Xu C, Luo E. Management of condylar resorption before or after orthognathic surgery: a systematic review. Journal of Cranio-Maxillofacial Surgery. 2019; 47: 1007–1014.

[19] Iwasa A, Tanaka E. Signs, symptoms, and morphological features of idiopathic condylar resorption in orthodontic patients: a survey-based study. Journal of Clinical Medicine. 2022; 11: 1552.

[20] Phyo Thu A, Song S, Karmacharya N, Huang X, Zhou N. Three-dimensional analysis of the morphological changes of the craniofacial jaw and condyle in patients with idiopathic condylar resorption. British Journal of Oral & Maxillofacial Surgery. 2023; 61: 598–604.

[21] Tanaka E, Rodrigo DP, Tanaka M, Kawaguchi A, Shibazaki T, Tanne K. Stress analysis in the TMJ during jaw opening by use of a three-dimensional finite element model based on magnetic resonance images. International Journal of Oral and Maxillofacial Surgery. 2001; 30: 421–430.

[22] Funck-Brentano T, Cohen-Solal M. Crosstalk between cartilage and bone: when bone cytokines matter. Cytokine & Growth Factor Reviews. 2011; 22: 91–97.

[23] Chen Y, Wang T, Guan M, Zhao W, Leung FKL, Pan H, et al. Bone turnover and articular cartilage differences localized to subchondral cysts in knees with advanced osteoarthritis. Osteoarthritis and Cartilage. 2015; 23: 2174–2183.