The objective of this study was to review the literature and compare different surgical methods for the management of coronoid process hyperplasia. A literature search was performed for publications since 1995. Case characteristics were extracted (age, sex, duration of symptoms, form, maximal mouth opening and treatment) and entered into a database for analysis. The data were split into two groups (coronoidectomy and coronoidotomy). Maximal mouth opening measurements before and after surgery were analyzed with several statistical tests. 61 cases were entered into the database. The mean age was 23 years and mean duration of symptoms 7 years. The bilateral form occurred 4.1 times more frequently than the unilateral form. The male–female ratio was 3.3 to 1. In 94% of the cases the approach was intra-oral. 84% of the cases received a coronoidectomy. Statistical analysis showed that the preoperative and postoperative differences between the groups were significant. The results were not significant when corrected for the preoperative difference. Postoperative therapy was not comparable due to heterogeneity. Cases that received a coronoidotomy had slightly better postoperative results.
Mandibular coronoid process hyperplasia (CPH) is a rare condition causing a slow, progressive reduction of mouth opening. CPH is defined as an abnormal elongation of the mandibular coronoid process consisting of histologically normal bone. This leads to impingement of the coronoid process on the body or arch of the zygomatic bone on opening of the mouth.
To date, mainly single case reports of CPH have been published. In the most recent complete review published in 1995 by Mcloughlin et al., 31 new cases of coronoid hyperplasia were reported together with a meta-analysis of previous data. They emphasized the normal histology of the resected coronoid process to distinguish it from other pathology. It was found that the condition most often affected adolescent men. Surgery was the treatment of choice, although the outcome was generally disappointing, possibly due to the formation of a haematoma or intra-oral fibrosis. The authors hypothesized that the extra-oral approach might cause less fibrosis, but too few extra-oral surgeries were performed to compare their postoperative measures with those of intra-oral surgeries. Postoperative physiotherapy (stretching exercises) were considered to be essential for the preservation of the increased mouth opening.
In this article, a systematic review of cases published since the review of Mcloughlin et al., is presented. The main objective is to compare the results of different surgical methods (e.g. intra-oral vs extra-oral, coronoidectomy vs. coronoidotomy).
Materials and methods
A systematic search in the Pubmed database was conducted to find related articles. In the search, the following Medical Subjects Headings (MeSH) terms were used: ‘coronoid’, ‘hyperplasia’, and ‘mandible’. The following free-text terms were entered as synonyms. For the term ‘coronoid’, synonyms ‘coronoid process’, ‘processus coronoideus’ and ‘processus muscularis’ were entered. For the term ‘hyperplasia’, synonyms ‘elongation’, ‘impingement’ and ‘enlargement’ were entered, as well as the MeSH term ‘hypertrophy’. For ‘mandible’, ‘mandib*’ and ‘lower jaw’ were entered as synonyms. Boolean operator OR was applied between synonyms. The operator AND was used between the three search terms.
The search was limited to articles in English describing cases, published in, or after, 1995. Titles and abstracts were assessed to select relevant articles, and then the full-text articles were retrieved. The reference lists of the selected articles were manually checked to trace additional cases. Throughout the search, cases were excluded if no hyperplasia with impingement was present, and/or histology and morphology of the coronoid process was characteristic for an osteochondroma.
From the included articles, specific case-characteristics were extracted and entered into a database as numerical or categorical data. Numerical data included age at diagnosis, duration of symptoms, maximum mouth opening (MMO) before, during and after the operation and length of follow-up. Categorical data consisted of uni- or bilateral CPH form, sex, diagnostic method, surgical method, and whether additional physiotherapy was performed. Two additional variables were calculated: age at onset and MMO improvement.
To evaluate if there was a statistically significant association between sex and uni- or bilateral type of CPH, a χ 2 -test was performed. The authors carried out several statistical tests on the outcome data. They split the surgery types into two groups: coronoidectomy and coronoidotomy groups. Cases were filtered out that had an extra-oral approach or underwent additional masseter stripping to make the coronoidectomy group more homogenous. After testing normality of the distribution with a residuals histogram, an independent t test was done to compare the means of the preoperative MMO, final MMO and MMO difference. A univariate analysis of variance (UNIANCOVA) was performed on the final MMO with the preoperative MMO as covariate. Differences were considered to be significant if p < 0.05. Management of the database and statistical analyses were performed using SPSS for Windows version 17.0.
The literature search was performed on 4 June 2010. The search led to 39 hits of which 35 articles were considered relevant. The full text of 5 articles could not be retrieved. With additional cross-referencing 5 relevant articles were found of which 4 were retrieved. Of the 34 articles that were assessed in full text, 8 articles were excluded. In two articles, no cases were described. Six articles reported cases which were excluded based on the exclusion criteria. One case was excluded from an article that reported two cases. From the selected articles, 58 cases were entered into the database. Information from the 3 cases at the authors’ institution was entered. 61 cases in total were analyzed ( Table 1 ).
|Authors||Year||Age (yrs)||History (yrs)||Type||Sex||Preoperative MMO (mm)||Peroperative MMO (mm)||Final MMO (mm)||Approach||Type||Follow-up (months)|
|2||Loh et al.||1997||22||4||bi||M||5||NS||20||EO||Ectomy||4|
|3||Loh et al.||1997||41||NS||bi||M||15||25||25||IO||ectomy||4|
|4||Loh et al.||1997||25||10||bi||F||16||NS||30||IO||Ectomy||4|
|5||Loh et al.||1997||14||2||bi||M||13||22||37||IO||Ectomy||12|
|6||Gerbino et al.||1997||15||1||uni||M||15||NS||41||IO||Tomy||12|
|7||Gerbino et al.||1997||14||2||uni||M||12||NS||48||IO||Tomy||60|
|8||Gerbino et al.||1997||13||3||bi||M||18||NS||38||IO||Tomy||15|
|9||Gerbino et al.||1997||32||17||bi||M||20||NS||38||IO||Tomy||60|
|10||Gerbino et al.||1997||16||2||bi||M||20||NS||45||IO||Tomy||60|
|11||Yamaguchi et al.||1998||25||8||uni||M||24||NS||43||IO||Ectomy||18|
|12||Pregarz et al.||1998||17||NS||uni||M||18||28||35||IO||Ectomy||20|
|13||Pregarz et al.||1998||20||7||bi||M||13||20||27||IO||Ectomy||12|
|14||Pregarz et al.||1998||17||5||bi||M||17||NS||39||IO||Ectomy||12|
|15||Pregarz et al.||1998||15||5||bi||M||18||NS||40||IO||Ectomy||24|
|16||Pregarz et al.||1998||16||NS||bi||M||19||25||38||IO||Tomy||12|
|17||Kubota et al.||1999||23||NS||bi||F||NS||NS||NS||NS||NS||NS|
|18||Kubota et al.||1999||28||NS||bi||F||NS||NS||NS||NS||NS||NS|
|19||Kubota et al.||1999||61||NS||bi||M||NS||NS||NS||NS||NS||NS|
|20||Mavili et al.||1999||17||14||uni||M||22||48||45||Endo||Ectomy||8|
|23||Asaumi et al.||2001||7||NS||bi||M||17||NS||NS||NS||NS||NS|
|24||Asaumi et al.||2001||14||NS||bi||M||2||NS||NS||NS||NS||NS|
|26||Colquhoun et al.||2002||26||3||bi||M||22||35||22||IO||Ectomy||30|
|27||Fabie et al.||2002||8||8||bi||F||6||33||30||IO||Ectomy||8|
|28||Mano et al.||2005||5||NS||bi||M||17||NS||40||IO||Ectomy||82|
|29||Tieghi et al.||2005||17||1||bi||F||25||40||40||IO||Ectomy||20|
|30||Tieghi et al.||2005||15||2||bi||M||25||40||46||IO||Ectomy||6|
|31||Satoh et al.||2006||13||1||bi||M||27||40||45||IO||Ectomy||8|
|32||Leovic et al.||2006||35||18||bi||M||15||NS||35||NS||Tomy||NS|
|33||Kursoglu and Capa||2006||17||NS||bi||M||14||NS||NS||None||None||NS|
|34||Kursoglu and Capa||2006||24||NS||bi||M||27||NS||NS||None||None||NS|
|35||Gibbons and Abulhoul||2007||36||20||bi||M||20||30||38||IO||Ectomy||12|
|36||Mazzetto et al.||2007||55||NS||uni||M||32||NS||NS||None||None||NS|
|37||Yoshida et al.||2008||34||NS||bi||F||18||44||38||IO||Ectomy||6|
|38||Ferro et al.||2008||28||NS||bi||M||13||NS||40||IO||Ectomy||12|
|39||Wenghoefer et al.||2008||53||NS||uni||F||NS||NS||30||NS||Ectomy||12–15|
|40||Wenghoefer et al.||2008||38||NS||uni||M||7||NS||35||NS||Ectomy||12–15|
|41||Wenghoefer et al.||2008||52||NS||uni||M||22||NS||NS||NS||Ectomy||12–15|
|42||Wenghoefer et al.||2008||18||NS||uni||F||NS||NS||30||NS||Ectomy||12–15|
|43||Wenghoefer et al.||2008||4||NS||bi||M||NS||NS||30||NS||Ectomy||12–15|
|44||Wenghoefer et al.||2008||28||NS||bi||M||NS||NS||30||NS||Ectomy||12–15|
|45||Wenghoefer et al.||2008||56||NS||bi||M||25||NS||NS||NS||Ectomy||12–15|
|46||Wenghoefer et al.||2008||23||NS||bi||M||10||NS||23||NS||Ectomy||12–15|
|47||Wenghoefer et al.||2008||2||NS||bi||F||10||NS||25||NS||Ectomy||12–15|
|48||Wenghoefer et al.||2008||18||NS||bi||M||16||NS||30||NS||Ectomy||12–15|
|49||Wenghoefer et al.||2008||35||NS||bi||M||5||NS||31||NS||Ectomy||12–15|
|50||Wenghoefer et al.||2008||45||NS||bi||M||10||NS||31||NS||Ectomy||12–15|
|51||Wenghoefer et al.||2008||5||NS||bi||F||4||NS||32||NS||Ectomy||12–15|
|52||Wenghoefer et al.||2008||14||NS||bi||M||15||NS||33||NS||Ectomy||12–15|
|53||Wenghoefer et al.||2008||16||NS||bi||M||14||NS||40||NS||Ectomy||12–15|
|54||Wenghoefer et al.||2008||24||NS||bi||M||18||NS||40||NS||Ectomy||12–15|
|55||Zhong et al.||2009||39||13||uni||F||8||40||31||IO||Ectomy||9|
|56||Yura et al.||2009||28||13||uni||M||30||50||43||IO||Tomy||15|
|57||Baraldi et al.||2010||20||NS||uni||F||12||30||35||IO||Ectomy||8|
|58||Galie et al.||2010||3||2||uni||F||5||NS||35||EO||Ectomy||18|
|59||The authors’ patient||2010||41||6||bi||F||15||25||22||IO||Ectomy||16|
|60||The authors’ patient||2010||14||2||bi||M||6||40||30||IO||Ectomy||4|
|61||The authors’ patient||2010||29||14||bi||M||20||40||39||IO||Ectomy||5|