Limitations of Jaw Movement in Fibrodysplasia Ossificans Progressiva: A Review

Abstract

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder characterized by heterotopic ossification (HO) of the skeletal muscles, fascia, tendons and ligaments. Patients often experience limitations in jaw function due to HO formation in the maxillofacial region. However, no studies have yet analyzed the age of onset and location of HO and the type of restrictions it may yield in the maxillofacial region. The aim of this study was to evaluate all existing literature on the site of onset of HO and associated functional restrictions of the jaw. To this end, a scoping review was performed focusing on limitations of jaw movement in FOP patients. The literature search resulted in 725 articles, of which 30 articles were included for full study after applying the exclusion criteria. From these articles 94 FOP patients were evaluated for gender, age, presence and age at which HO started in the maxillofacial region, location of HO, whether HO was caused spontaneous or traumatic and maximum mouth opening. Formation of HO is slightly more common in female patients compared to male patients, but the age of HO onset or the maximum mouth opening does not differ between genders. Trauma-induced HO occurred at a significantly younger age than spontaneous HO. Interestingly, a difference in maximum mouth opening was observed between the different ossified locations in the maxillofacial region, with ossification of the masseter muscle resulting in the smallest and ossification of the zygomatic arch resulting in the largest maximum mouth opening. This review revealed that the location of the maxillofacial region affected by HO determines the degree of limitations of the maximum mouth opening. This finding may be important for establishing clinical guidelines for the dental management of FOP patients.

Keywords: dental; fibrodysplasia ossificans progressiva; jaw; maxillofacial region; maximum mouth opening; review.

Figure 1

Flowchart of the literature search strategy. Records were included or excluded based on the beforehand defined criteria.

Figure 2

Relation between HO and gender. Female patients in our cohort were significantly older than male patients, (A) (p < 0.5, female n = 47, male n = 45). Female patients show statistically more HO in the maxillofacial area compared to male patients, (B) (p < 0.05, female n = 47, male n = 45). There is no difference between age of onset of HO (C, female n = 34, male n = 24) or between mouth opening (D, female n = 23, male n = 25) and gender. When both female and male patients are taken together there is a non-significant decrease in maximum mouth opening with increasing age (E, n = 48). *p < 0.05.

Figure 3

Age of spontaneous or trauma-induced HO. Trauma-induced HO occurs at a significantly lower age compared to spontaneously occurring HO, (A) (p < 0.05, spontaneous n = 47, trauma induced n = 22). Also the mean age of onset is significantly lower in trauma-induced HO, (B) (p < 0.05, spontaneous n = 41, trauma induced n = 17). There is no difference in maximum mouth opening between the two causes of HO (C) (spontaneous n = 27, trauma induced n = 11). **p < 0.01.

Figure 4

Anatomic representation of maxillofacial structures and muscles that can be affected by HO in FOP patients. (A) (1) The coronoid process (front side of the rami) can ossify with the zygomatic arch. (2) The coronoid process and zygomatic arch can ossify individually. (3) The condyle process (back side of the rami) can ossify individually (lateral view). (B) The masseter (lateral view). (C) The lateral and medial pterygoid (lateral view). (D) The lateral and medial pterygoid (posterior view). (E) The suprahyoid muscles (digastric, geniohyoid, and mylohyoid) can ossify with the hyoid bone (lateral view). (F) The suprahyoid muscles (digastric, geniohyoid, and mylohyoid) can ossify with the hyoid bone (inferior view). Frequencies of HO of the various muscles and bony regions are shown in Figure 5. Picture: Courtesy of Jan Harm Koolstra, ACTA, The Netherlands.

Figure 5

Relation between HO and location. There does not seem to be a correlation between the cause of HO or the age of onset of HO and its location (A,B). The different possible locations of HO seem to differ in their effect on maximal mouth opening, with a significant difference between HO in the masseter muscle and HO between the zygomatic arch and the coronoid process (C).