Traumatic Myositis Ossificans of Temporalis Muscle: Systematic Review, Meta-Analysis and Case Reports

Abstract

Introduction

Traumatic myositis ossificans is rare pathology affecting muscles/soft tissue. Its involvement in temporalis muscle is rarely reported in literature. The aetiopathogenesis is unknown, the diagnosis is based on clinco-radiological findings. Surgical management and follow-up are paramount.

Materials and Methods

A database search was done using Science Direct and PubMed search engines along with other published and unpublished literature. The final publications were tabulated using a custom made Performa. The available publications were subjected to appropriate statistical analysis. The data were recorded on excel spreadsheet (Microsoft Inc), and review was made using Review Manager (Rev Man) software for meta-analysis.

Results

A total of 21 articles were considered for systemic review and meta-analysis. Forest plotting for demographics included the gender predilection/age of involvement. The data segregation was done with “temporalis involved” group and “other than temporalis involved” group. The study was free of homogeneity ( τ 2 = 0.26 I 2 = 5%) for gender and age. The overall analysis revealed that Temporalis muscle although rare to be affected shows greater propensity for involvement. This is supported by a lesser degree of heterogeneity ( τ 2 = 0.000) with a I 2 value of (The test showed a higher degree of significance for overall effect of muscle involvement (Z = 2.33, p = 0.02) (< 25%). The test showed a higher degree of significance for overall effect of muscle involvement (Z = 2.33, p = 0.02) (< α = 0.05).

Case reports.

Two male cases with similar age predilection, reported after sustaining trauma. Both the cases presented with limited mouth opening and ultrasound was done for the first time to arrive at clinic-radiological diagnosis. The management was conservative with temporalis myotomy and coronidectomy.

Conclusion

Traumatic myositis ossificans presents as a rare disorder that poses a dilemma to the treating surgeon. The present article makes an attempt to critically analyse the pathology that is scantly reported in the literature.

Introduction

Myositis Ossificans (MO) is a rare disease presenting as hetrotropic ossificans of muscle or soft tissue. MO is broadly divided into myositis ossificans progressiva (MOP) and myositis ossificans traumatic (MOT) also called as mysositis ossificans circumscriptia, or Traumatic Myositis Ossificans (TMO), the term Mucher-Meyer diseaseis applied to a autosomal dominant hereditary pattern along with systemic manifestations [1, 2]. TMO is usually a result of single or repetitive injury to the muscle which results in calcification and restricted function. TMO is widely reported in the orthopaedic literature [3]. The quadriceps femoris and brachialis anticus are the most affected muscles, young athletes in particular have a higher predilection [4]. In the craniofacial complex, the lesion seems to be scantly reported, with relatively common predilection to master muscle, mostly in the third, fourth and fifth decades of life [5]. The involvement of temporalis muscle is even more uncommon with a total of six cases being reported in the literature to date. However, in most of the cases trauma seems to be the single causative factor with rare exceptions.

It is to till date the nature and cause of TMO and has been scantly elucidated, the possible theories suggesting that metaplasia of connective tissues and hematoma ossificans are mentioned in literature [6, 7]. Nevertheless, all possible theories revolve around the aberrancy in physiological healing processes. There are four main theories as postulated by Cary which are as follows: displacement of bone fragments in the soft tissues with subsequent proliferation, detachment of periosteal fragments into the surrounding tissues with proliferation of osteoprogenitor cells, migration of sub-periosteal osteoprogenitor cells around the soft tissue through periosteal perforation induced trauma and metaplasia of extraosseous cells exposed to bone morphogenetic proteins (BMPs) derived from bone lysis when it is displaced into the soft tissue during traumatic events [8].

Over the past years researchers have addressed the issue via their publications. It was our effort to evaluate the lesion based on various parameters; hence, it was decided to approach the issue by systematic review and meta-analysis with temporalis muscle and other than temporalis muscle as the mainstay. The article is also supplements with additional two cases of TMO involving Temporalis muscle and the management that was carried out at our tertiary level hospital.

Materials and Methods

Search Strategy

The search protocol followed standard guidelines. An electronic database search for published, unpublished and ongoing articles till Sep 2021 was conducted. The search engines were restricted to Science Direct and PubMed databases without the use of filters. The key words which were used were; “Myositis Ossificans”, “Facial muscles”, “Trauma”. We used the character “ + ” in between the keywords to activate a phrase search. Parallel to this a manual search was carried out of relevant maxillofacial journals published over the past 5 years was carried out and of the available literature in other forms were also included in the study (Bibliography, Dissertation etc.).

Selection of Studies

The search was conducted independently by two authors V.K. and S.G. The citations were retrieved on the basis of title, abstract and keywords. Publications which did not belong to the research process and those with incomplete data were excluded from the study. An eligibility criteria form was used to evaluate the publications available at hand. The articles which were included were again analysed carefully using full texts that were evaluated carefully by the two authors.

Data Collection

The included publications were re-analysed by authors V.K. and S.G. and was recorded on the Performa which was designed by the authors and was tabulated on Excel Spreadsheet (Microsoft Inc) Table 1 the data was then entered based on board characteristics like: 1. Study characteristics: First author name, Year of publication; 2. Demography: Age, Sex, number of patients, type of study; 3. Site involved: Muscle involved (Temporalis versus other than temporalis); 4. Aetiology: Iatrogenic, Trauma, 5. Pre-operative mouth opening versus post-operative mouth opening; 6. Intervention, 7. Follow-up.

Table 1.

Publications included in the meta analysis

S.NO	Author	Year
1	Hellinger et al. [9]	1962
2	Leo Lutwak et al. [10]	1964
3	Shawkat et al. [11]	1965
4	Abdin HA et al. [12]	1984
5	Royji Arima et al. [13]	1984
6	Lello et al. [14]	1986
7	Glenn et al. [15]	1986
8	Martin Steiner et al. [16]	1997
9	C Debeney-Bruyerre et al. [17]	1998
10	Dongsoo David Kim et al. [18]	2002
11	Rattan et al. [19]	2004
12	Wiggins et al. [20]	2008
13	Estevam Rubens et al. [21]	2010
14	Bhushan Jayade et al. [22]	2013
15	Michel J Schiff et al. [23]	2013
16	Almedia et al. [24]	2014
17	Torres et al. [25]	2014
18	Becker et al. [26]	2015
19	Almahndr et al. [27]	2019

Data Synthesis

The data was analysed using data analysis software for conduct of meta-analysis using Review Manager (Rev Man) version 5.3; and the data was fed on Spreadsheet (Google Inc) to carry out analysis. Continuous data such as maximum inter-incisal mouth opening (MIO) and age were expressed as mean with a standard deviation (SD) and 95% confidence interval (CI). The number of cases that was available due to rarity of the pathology, was small, publication bias was not formally assessed. Forest plotting was done for evaluation of mouth opening and gender predilection and was documented using Chi square test and other statistical analysis.

Data Analyses

The data which was obtained was evaluated for number of cases reported in the article and was divided based on demography (Age and Sex) and those where temporalis was involved and those where other than temporalis was involved. Appropriate statistical analysis was applied to test the level of significance, Degree of freedom, test of heterogeneity and independence in order to eliminate the risk of bias for selection.

Results

Study Characteristics

A total of 784 publications were retrieved from the databases (Fig. 1a). After which titles and abstracts were analysed independently by authors (V.K. and S.G.) About 21 articles which were considered eligible were re-analysed by a full text review by the same authors and a total of 19 articles were finally included for meta-analysis.

Fig. 1.

A Graph representing age distribution of Temporalis involved cases. B graph representing age distribution of Non-Temporalis involved cases. C increase in mouth opening as reported in the literature. D statistical analysis of demographic data

Tabulation.

The tabulation of each article was carried out as mentioned in Materials and Methods (Table 1). The Review Manager (Rev Man) software also showed a total of 19 articles and a total of 22 cases that was analysed and subjected to Forest plotting. The final articles considered are represented in Table 1.

Demographics

Out of the available 20 cases, there were 09 males and 11 females. Four studies did not mention about the gender of the cases considered for the study. Age distribution of cases where in temporalis was involved showed a mean age of 27 years ± 7.118, n = 07 at α = 0.05 (Fig. 1b, c).

Segregation

The available data was analysed based on two categories, one was where the temporalis muscle (n = 7) was involved and other category was other than temporalis muscle involved group (n = 13). The analysis however was limited to the maxillofacial complex.

Outcome Variable

Mouth opening pre-operative versus post-operative was the outcome variable which was considered for the analysis of the study. A total of 07 publications had a complete documentation of pre-operative and post-operative analysis rest had incomplete or no documentation of mouth opening. The Post-operative change in mouth opening was tabulated and analysed and had a mean of 31.28 ± 11.26, n = 07, α = 0.05 (Fig. 1d).

Statistical Analysis for Demographics (Gender and Age)

Forest plotting is done for Gender, where random effect model is considered and odds ratio is considered for effect measure.The analysis is done to evaluate test of heterogeneity by use of τ²test, which had a value of 0.26 with a I ² value of 5%, which meant that the study has low or no heterogeneity (< 25%) for gender. The analysis also suggested that the analysis for overall effect ofgender is not significant (Z = 0.44, p = 0.66(> α = 0.05). This suggests that the overall effect of age is not significant with the lesion under study (Fig. 2a).

Fig. 2.

Statistical representation of temporalis and non-temporalis involved cases

Statistical Analysis for Site Predilection (Temporalis versus Non Temporalis)

Similar forest plotting was extended to the variable of temporalis involvement versus other than temporalis, where random effect model is considered with odds ratio as effect measure at 95%CI. involvement. The overall analysis revealed that Temporalis muscle although rare to be affected shows greater propensity for involvement. This is supported by a lesser degree of heterogeneity (τ² = 0.000) with a I ² value of) (< 25%). The test showed a higher degree of significance for overall effect of muscle involvement (Z = 2.33, p = 0.02) (< α = 0.05).

Case Report

Case 1

A 32 year old male reported to the Department of Oral and Maxillofacial Surgery with a history of trauma following a road traffic accident. He was examined clinco-radiologically on the fourth day post-trauma and was diagnosed as a case of fracture Zygomatico-maxillary complex (Left) along with zygomatic arch (Left). On clinical examination he had a mouth opening of 15 mm (mm) (Fig. 3a). He was operated for open reduction and internal fixation with closed reduction of zygomatic arch via Keen’s approach. Post-operative period he was evaluated for mouth opening which improved to 35 mm. He was observed for 12 days post-operatively and was discharged for out-patient follow-up after 04 weeks. On revisit the individual had trismus with a mouth opening of 5 mm. As he was refractory to all mechanical and pharmacological management, he was recommended an ultrasonography of the temporalis muscle which revealed a diagnosis of myositis ossificans of temporalis (Left). The finding were in sync with the clinical findings hence a working diagnosis of Traumatic Myositis Ossificans (TMO) left temporalis was made. A decision to carry out coronoidectomy with temporalis myotomy was done under general anaesthesia (Fig. 3b). The biopsy of musce tissue from the cornoid area was subjected to histopathologial testing which was consistent with myositis ossificans, thereby confirming the diagnosis of TMO Temporalis. Post-operative period showed a drastic improvement of mouth opening of 50 mm (Fig. 3c). The individual has been under follow-up since the past 52 weeks.

Fig. 3.

A pre-operative picture of case 1. B Specimen depicting excised coronoid. C Post-operative mouth opening (50 mm)

Case 2

A 38 year old male reported to the Dept of Oral and Maxillofacial Surgery with a history of trauma following a sports related injury. He was examined clinco-radiologically on the eight day post-trauma and was diagnosed as a case of fracture Zygomatico-maxillary complex (Right) alongwith zygomatic arch (Right. On clinical examination he had a mouth opening of 05 mm (mm) (Fig. 4a). He was operated for open reduction and internal fixation and zygomatic arch was exposed by a hemi-coronal approach and the fracture fragment was removed owing to instability on fixation. Post-operative period he was evaluated for mouth opening which improved to 45 mm. He was observed for 12 days post-operatively and was discharged for out-patient follow-up after 04 weeks. On revisit after 28 days the individual had trismus with a mouth opening of 8 mm. This individual too was refractory to all mechanical and pharmacological management, he was recommended an ultrasonography of the temporalis muscle which revealed a diagnosis of myositis ossificans of temporalis (Right). The finding was in sync with the clinical findings; hence, a working diagnosis of Traumatic Myositis Ossificans (TMO) right temporalis was made. A decision to carry out coronoidectomy with temporalis myotomy was done under general anaesthesia. Post-operatively the individual developed bleeding via surgical site and haematoma which was addressed immediately. The biopsy of muscle tissue from the coronoid area was subjected to histopathologial testing which was also consistent with subacute phase thereby confirming the diagnosis of TMO Temporalis. Post-operative period showed a gradual improvement of mouth opening of 30 mm (Fig. 4b). The individual has been under follow-up since the past 28 weeks.

Fig. 5.

A 100X magnification. B 400X magnification shows tendinous insertion site with mature lamellar bone (Star) with the tendon (Plus) undergoing ossification in the form of woven bony trabeculae (Square). C figure showing foci of necrosis in the tendon (Black arrow). D figure showing areas of neovascularisation in the tendon

Fig. 4.

A Pre-operative image of case-2 showing restricted mouth opening (12 mm). B Post-operative mouth opening following temporalis myotomy and coronoidectomy (37 mm)

Discussion

This systematic review and meta-analysis was carried out using electronic databases as well as reviews on published and unpublished literature. On careful scrutiny round 19 articles were considered appropriate for the study. The reason behind this limited number of cases is the relatively lesser number of cases that have been reported in literature. Boffano et al. [28] have reported in their review of literature a total 43 reported cases of TMO involving muscle of the maxillofacial complex. The later articles which have reported similar cases have been by Torres et al. (MM) and Ramos et al. (MM), who reported one case each. The involvement of temporalis muscle is even rare among all the muscles of mastication. In the present review, it seems that a total of seven cases have been reported where isolated temporalis muscle seems to be involved. However, Becker et al. [26] in their survey mention a total of 17 cases reported in the literature. It is also unique to note that the statistical analysis which involved a forest plotting showed a higher predilection of temporalis muscle. The reasons for this dichotomous presentation could be due the reported cases are lesser as the clinicians most often may feel that it is due to untoward consequence of trauma. This was so in both our cases where the diagnosis becomes very challenging. Other studies that were conducted by Aoki T et al. and Mevio et al. mention that the pathology is more predominant in masseter compared to other muscles with a ratio of 2.23: 1 [29, 30].

The clinical presentation of TMO start immediately post-trauma or up to 06 months later. There a variety of manifestations and may include; trismus, firm/solid oedema, calcification seen as radiolucencies [31], as seen both of our cases and as reported in our review in which all the cases had presented in one or more of the mentioned symptoms. Most of the studies have shown a predilection towards third decade of life which was also seen both of our cases, the reason may be due to increase incidence of trauma to the oro-facial musculature which also falls in this age group [32].

The aetiology of TMO is unknown; most common cause attributed to this hypothesis is the involvement of perivascular mesenchymal cells to bone morphogenic protein. The release of bone morphogenic protein form native bone cells may result from trauma or surgical insults [33]. The diagnosis of the lesion is predominantly clinical. However, all the studies have depended on radiological evidence prior to management. Early lesions have shown amorphous calcification in soft tissues on axial sections. Mature lesions may be well circumscribed and long standing cases may be diffusely calcified. The studies that have been reported till date have not made use of ultrasound, but in our cases ultrasound provided valuable information about the location and extent of the lesion.

The management of the pathology involves various modalities that have been reported in literature. Conservative management has also been suggested [18]. Nevertheless, many literatures including orthopaedic literature suggest simple excision as a curative measure with minimal recurrence rate [34]. Some authors have suggested early intervention for better results [35], other mention that surgery should not be contemplated until 35% of the lesion does not regress or it becomes a functional handicap [36]. In both our cases the lesion created a restricted mouth opening leading to morbidity hence surgical excision was contemplated via myotomy. This involved a conservative approach of coronoidectomy instead of approaching the whole muscle extra-orally. Various non-surgical management have also been suggested by various authors ranging from medications like non-steroidal anti-inflammatory lesions to low level radiation therapy [37]

The outcome variable considered in our study was the overall mouth opening which was considered in the temporalis group versus the other than temporalis group. The studies so far conducted scantly talk about the change in mouth opening following the procedure. Out of the available studies, five publications have mentioned mouth opening in pre as well as post-operative period. In the present cases we were able to achieve an adequate mouth opening even with a conservative management like myotomy.

Surgical biopsy remains the mainstay for the diagnosis of TM, which was carried out in both of our cases. In most of the times TMO shows zonal architecture with peripheral ossification and a central cellular zone of involvement. It is the zonal architecture which is the hallmark that differentiates it from osteosarcoma, which is mandatory as the latter poses a different challenge and needs a different management protocol. Lello et al. [14] mention that a large biopsy, incorporating all three zones if possible is needed to ensure that a misdiagnosis of osteogenic sarcoma or firosarcoma does not occur. In both our cases we could notice features consistent with myositis ossificans.

Post-operative follow-up has been mentioned in 07 publications that were considered in the study. It is important that a follow-up protocol be in place to observe two, although rare manifestations, first being that of recurrence and the other being any signs and symptoms of malignant conditions which may have been left unnoticed.

The previous reviews of the literature which were conducted did not involve detailed meta-analysis as seen in this study. The rarity of the study makes it even more challenging to arrive at a protocol for management of such pathologies. The present study involved rigorous search strategy and a custom made proforma which was utilised in the present study helped the authors to document every detail from the plethora of publication yet provide a nutshell view of data available at hand for further analysis.

The statistical analysis remained the mainstay of the study which made use of Tests for homogeneity to keep a check on variety of publications used and to also to see that the study was devoid of selection bias. Odds ratio remains the mainstay of the analysis to evaluate the need for significance of the study. The test were cross tabulated and analysed by using appropriate logistics model. The main outcome variables that we considered were broadly based on demographics and outcome variables. The gender predilection was considered as the previous studies did not rely on predominance of gender and TMO. The studies conducted so far are based on mere assumptions as male suffer more trauma comparatively needed appropriate analysis. The outcome variable of mouth opening was considered as the degree of mouth opening provides for a better functional outcome thereby reducing morbidity. The present study is in tandem with most studies and our case presentations also provided an adequate mouth opening as the end result of the procedure.

Conclusion

TMO is a rare disorder that seldom affects the maxillofacial region, Temporalis muscle involvement has scantly been reported in literature. In the present article we felt the need for a rigorous systematic review of the available literature and a roboust meta-analysis so as to understand the disease pathology and also for the better management of the condition. The whole purposes of documenting this manuscript was for enriching the available scant literature academically and also understand the better means of management of the condition. We also present two cases of TMO of temporalis following trauma, and as per our available knowledge, only seven cases have been reported in literature. The addition of two cases was for better understanding of the lesion. Most of the studies have not reported on the use of Ultrasonography for the diagnosis, both the cases we used this as the modality instead of computed tomography, thereby reducing radiation dosage and ease of obtaining results. Moreover, it would help us analysed the location of the lesion. The surgical management was the mainstay, but we were more conservative, by using a intra-oral approach and conducted a myotomy and coronoidectomy. The outcome that was meta-analysed was the mouth opening, which was considered as the best functional advantage to the patient. This aspect has scant evidence in the literature and the present article has tried to furnish appropriate details, both our cases too had adequate mouth opening. The dilemma of aetiology and genesis needs further elaboration, which is the further scope of the present study.

Funding

They have not been funded by any person/firm/organisation.

Declarations

Conflict of interest

The authors declare that they have no conflict of interest.