Condylar hyperplasia

Condylar hyperplasia (mandibular hyperplasia) is over-enlargement of the mandible bone in the skull.[1] It was first described by Robert Adams in 1836 who related it to the overdevelopment of mandible. In humans, mandibular bone has two condyles which are known as growth centers of the mandible.[2] When growth at the condyle exceeds its normal time span, it is referred to as condylar hyperplasia. The most common form of condylar hyperplasia is unilateral condylar hyperplasia where one condyle overgrows the other condyle leading to facial asymmetry. Hugo Obwegeser et al.[3] classified condylar hyperplasia into two categories: hemimandibular hyperplasia and hemimandibular elongation. It is estimated that about 30% of people with facial asymmetry express condylar hyperplasia.[4]

Condylar hyperplasia
Other names	Mandibular hyperplasia

In 1986, Obwegeser and Makek[3] specifically detailed two hemimandibular anomalies, hemimandibular hyperplasia and hemimandibular elongation. These anomalies can be clinically present in a pure form or in combination.

Cause

Condylar hyperplasia has an unknown cause. Several theories exist in literature which related to the cause of condylar hyperplasia. One theory states that an event of a trauma leading to increase in number of repair mechanism and hormones in that area may lead to increase in growth of mandible on that side.[5] Another theory states that an increase in loading of the temporomandibular joint can lead to increase in expression of bone forming molecules.[6] Condylar hyperplasia predominantly affects women with 64% of patients being women.[7]

Diagnosis

Diagnosis of asymmetry can be done through many different methods. PA cephalometry, panoramic radiograph, and nuclear imaging are some of the techniques that can be used for diagnosis.[8] Primarily nuclear imaging techniques such as single-photon emission computed tomography (SPECT), positron emission tomography (PET), and bone scintigraphy are taken along with other data before a patient is diagnosed for Condylar Hyperplasia.[8] In SPECT imaging, an increase uptake of the isotope is seen on the affected in comparison to the non-affected side. A difference of at least 10% or a minimum ratio of 55% to 45% uptake of technetium-99m is seen when comparing affected vs non-affected side respectively. An uptake of more than 55% and difference of at least 10% indicates an active condylar growth.[9]

Classification

Hugo Obwegesr and Makek classified condylar hyperplasia into three categories, listed in the table below.[3] Type 1 develops its characteristics from the horizontal vector, and Type 2 develops its characteristics from the vertical vector. Type 1 CH occurs much more common (15x) than Type 2 CH. Wolford et al.[10] in 2014, developed an updated classification of condylar hyperplasia. In 1986, Slootweg & Muller devised a histopathological classification which allows the condylar tissues to be classified into specific categories.[11]

Type	Name	Clinical findings	Histological findings
Type 1	Hemimandibular elongation	- Chin deviation towards contralateral side - Midline shift towards contralateral side - Posterior crossbite on contralateral side	- Excessive growth in the horizontal vector - Enlarged ramus, normal condyle
Type 2	Hemimandibular hyperplasia	- Sloping rima oris with minimal chin deviation - Supra-eruption of maxillary molars on affected side - Open bite - Midline shift (minimal to none)	- Excessive growth in the vertical vector - Excessive growth in the condylar head
Type 3	Combination of both	- Chin deviation towards contralateral side - Possible open bite - Sloping rima oris with possible chin deviation	- Combination of excessive growth in both vectors

Treatment

Many treatment options exist for this type of condition. Orthognathic surgery can be performed once the active condylar growth has finished in some cases. The point of this surgery to wait as long as the condyle is growing and only do surgery when the condyle stops growing, so the chances of any worsening of facial asymmetry lessens. This option, however, does include a person living with the facial asymmetry features all the way up until 18 to 19 years of age. A procedure called condylectomy can also be done which involves removing part of the growing condyle to arrest any active growth.[12] Sometimes condylectomy can be done in conjunction with articular disk repositioning and orthognathic surgery to treat patients with mandibular hyperplasia, such as shown by Wolford et al.[13]

References

1. Olate, Sergio; Netto, Henrique Duque; Rodriguez-Chessa, Jaime; Alister, Juan Pablo; de Albergaria-Barbosa, Jose; de Moraes, Márcio (2013-09-25). "Mandible condylar hyperplasia: a review of diagnosis and treatment protocol". International Journal of Clinical and Experimental Medicine. 6 (9): 727–737. ISSN 1940-5901. PMC 3798207. PMID 24179565.
2. Landesberg, R.; Proctor, R. L.; Rosier, R. N.; Puzas, J. E. (1995-01-01). "The mandibular condylar growth center: Separation and characterization of the cellular elements". Calcified Tissue International. 56 (1): 71–77. doi:10.1007/BF00298747. ISSN 0171-967X. PMID 7796350.
3. Obwegeser, H. L.; Makek, M. S. (1986-08-01). "Hemimandibular hyperplasia--hemimandibular elongation". Journal of Maxillofacial Surgery. 14 (4): 183–208. doi:10.1016/S0301-0503(86)80290-9. ISSN 0301-0503. PMID 3461097.
4. Olate, Sergio; Almeida, Andrés; Alister, Juan Pablo; Navarro, Pablo; Netto, Henrique Duque; de Moraes, Márcio (2013). "Facial asymmetry and condylar hyperplasia: considerations for diagnosis in 27 consecutives patients". International Journal of Clinical and Experimental Medicine. 6 (10): 937–941. ISSN 1940-5901. PMC 3832331. PMID 24260600.
5. Alyamani, Ahmed; Abuzinada, Sondos (2012). "Management of patients with condylar hyperplasia: A diverse experience with 18 patients". Annals of Maxillofacial Surgery. 2 (1): 17–23. doi:10.4103/2231-0746.95311. ISSN 2231-0746. PMC 3591071. PMID 23483790.
6. Scapino, Robert P. (1983-04-01). "Histopathology associated with malposition of the human temporomandibular joint disc". Oral Surgery, Oral Medicine, Oral Pathology. 55 (4): 382–397. doi:10.1016/0030-4220(83)90193-7. PMID 6574416.
7. Almeida, Luis Eduardo; Zacharias, Joseph; Pierce, Sean (2017-05-25). "Condylar hyperplasia: An updated review of the literature". Korean Journal of Orthodontics. 45 (6): 333–340. doi:10.4041/kjod.2015.45.6.333. ISSN 2234-7518. PMC 4664909. PMID 26629479.
8. Yang, Zhiyun; Reed, Tameron; Longino, Becky H. (March 2016). "Bone Scintigraphy SPECT/CT Evaluation of Mandibular Condylar Hyperplasia". Journal of Nuclear Medicine Technology. 44 (1): 49–51. doi:10.2967/jnmt.115.158691. ISSN 1535-5675. PMID 26111714.
9. Hodder, S. C.; Rees, J. I.; Oliver, T. B.; Facey, P. E.; Sugar, A. W. (April 2000). "SPECT bone scintigraphy in the diagnosis and management of mandibular condylar hyperplasia". The British Journal of Oral & Maxillofacial Surgery. 38 (2): 87–93. doi:10.1054/bjom.1999.0209. ISSN 0266-4356. PMID 10864700.
10. Wolford, Larry M.; Movahed, Reza; Perez, Daniel E. (2014-03-01). "A classification system for conditions causing condylar hyperplasia". Journal of Oral and Maxillofacial Surgery. 72 (3): 567–595. doi:10.1016/j.joms.2013.09.002. ISSN 1531-5053. PMID 24388179.
11. Slootweg, P. J.; Müller, H. (August 1986). "Condylar hyperplasia. A clinico-pathological analysis of 22 cases". Journal of Maxillofacial Surgery. 14 (4): 209–214. doi:10.1016/S0301-0503(86)80291-0. ISSN 0301-0503. PMID 3461098.
12. Pereira-Santos, Darklilson; De Melo, Willian Morais; Souza, Francisley Avila; de Moura, Walter Leal; Cravinhos, Julio César de Paulo (July 2013). "High condylectomy procedure: a valuable resource for surgical management of the mandibular condylar hyperplasia". The Journal of Craniofacial Surgery. 24 (4): 1451–1453. doi:10.1097/SCS.0b013e318285d31f. ISSN 1536-3732. PMID 23851829.
13. Wolford, Larry M.; Mehra, Pushkar; Reiche-Fischel, Oscar; Morales-Ryan, Carlos A.; García-Morales, Patricia (February 2002). "Efficacy of high condylectomy for management of condylar hyperplasia". American Journal of Orthodontics and Dentofacial Orthopedics. 121 (2): 136–150, discussion 150–151. doi:10.1067/mod.2002.118403. ISSN 0889-5406. PMID 11840126.