Effect of temporomandibular joint bony ankylosisand surgical sequelae of gap arthroplasty on middleear volumeMohammad Dehisa, Wahid H. Tantawyb, Abeer Kamalc, Sayed A. Rashedc

and Mamdouh Sayeda

Aim The aim of this study was to evaluate the effect of

temporomandibular joint bony ankylosis and surgical

sequelae of gap arthroplasty on middle ear volume (MEV).

Patients and methods Sixteen Egyptian individuals were

selected and divided into two equal groups. The first group

(group I) included eight patients with 14 bony ankylosed

joints; the second group (group II) included eight normal

individuals. The operated patients were chosen from those

attending the outpatient clinic of the Department of

Oral and Maxillofacial Surgery, Faculty of Oral and Dental

Medicine, Cairo University. Gap arthroplasty was utilized

for the management of such patients. Radiographic

assessments for MEV for the first group were obtained

for all the participants preoperatively and also 3 months

postoperatively. Comparison of MEV was carried out with

normal individuals both preoperatively and 3 months

postoperatively.

Results It was observed that there was a significant

decrease in MEV of ankylosed patients preoperatively

when compared with normal individuals and a

significant decrease in MEV 3 months postoperatively

when compared with the preoperative volume.

Conclusion Patients with temporomandibular joint

bony ankylosis showed a decrease in MEV

compared with normal individuals; also, gap arthroplasty

has a decreasing effect on MEV. Egypt J Oral Maxillofac

Surg 4:72–77 �c 2013 The Egyptian Association of Oral &

Maxillofacial Surgeons.

Egyptian Journal of Oral & Maxillofacial Surgery 2013, 4:72–77

Keywords: computed tomography, gap arthroplasty, middle ear volume,temporomandibular joint ankylosis

aDepartment of Oral and Maxillofacial Surgery, Faculty of Oral and DentalMedicine, Cairo University, bDepartment of Radiology, Faculty of Medicine,Ain Shams University, Cairo and cDepartment of Oral Surgery, Faculty of Oral andDental Surgery, Misr University for Science and Technology (MUST), Giza, Egypt

Correspondence to Abeer Kamal, BDS, MSc, PhD, Department of Oral Surgery,Faculty of Oral and Dental Surgery, Misr University for Science and Technology(MUST), 7 Ghernat St., Roxy Heliopolis, 413 EgyptTel: + 20 24543572/ + 20 1005168009; fax: + 002 02 24543572;e-mail: abeermk7@gmail.com

Received 20 June 2013 accepted 20 July 2013

Introduction and review of the literatureTrauma was reported to be the first etiologic factor in

temporomandibular joint (TMJ) bony ankylosis. Hemar-

throsis and the anatomical nature of joints in children

are believed to be the major cause, whereas condylar

fractures with iatrogenic factors were found to be the

major etiologic factor in adults. TMJ disruption was

reported to be involved in massive head trauma

complicated with the presence of a temporal bone

fracture. It was hypothesized that displaced fracture of

the posterior wall of the TMJ may affect the middle ear

because of a concomitant perforation, leading to ossicular

chain discontinuity. High-resolution computed tomogra-

phy (CT) is an appropriate investigation for the detection

of middle ear changes with ossicular disruptions showing

separation of the incudostapedial joint, fracture of the

stapes, and dislocation of the incus [1–3].

The treatment of TMJ ankylosis poses a significant

challenge because of its technical difficulties and a high

incidence of recurrence. Gap arthroplasty has been

described as a simple and effective surgical technique

in the management of TMJ ankylosis. It is the technique

of resecting a segment of the bone at some point between

the base of the skull and the site of the mandibular

foramen. The gap created usually ranges from 0.6 to

1.5 cm and up to 2 cm as recommended by Topazian [4].

The induced gap should be established at the most

superior part of the ramus to maintain a maximal ramal

height, to minimize the possibility of occurrence of

anterior open bite, and to increase the chance of

normality of postoperative mandibular function [5–7].

The ear and the TMJ are embryologically, physically, and

anatomically very close to each other and have a strong

influence on proper functioning of each other. Pain of

the TMJ may lead to contraction of the little muscles

(the tensor tympani and tensor veli palatini) inside the

tympanic cavity. These muscles hold the ear bones

(malleus, incus, and stapes) in place. All these three ear

bones are essential to the function of hearing. The

contraction and spasm of these muscles cause hearing

impairment by affecting the proper functioning of the ear

bones [8,9].

Posterior displacement of the condyle has been reported

to exert pressure on the auriculotemporal nerve and the

chorda tympani, as well as the Eustachian tube. Pressure

on these structures might induce erosion of the tympanic

plate. Eustachian tube dysfunction has been attributed

to reflex disturbances of the tensor tympani and the veli

palatini muscles. Bettega et al. [10] and Ioannides and

Hoogland [11] reported that the otomandibular (e.g.

diskomalleolar and tympanomandibular) ligaments are

among the structural causes for aural symptoms. It is

hypothesized that patients with TMJ disorders have

muscle spasms responsible for regulating the activity of

the Eustachian tube [12–17].

72 Research paper

2090-097X �c 2013 The Egyptian Association of Oral & Maxillofacial Surgeons DOI: 10.1097/01.OMX.0000434297.76601.e3

It has been reported that the average middle ear volumes

(MEVs) in the normal ears, as measured using CT, were

5.6–7.9 ml [18–20]. Ahn et al. [21] reported that the

MEVs were 1.1 ± 0.8 ml in 44 ears with chronic otitis

media, which were smaller than the normal values.

Acquired cholesteatoma is the main complication of

chronic otitis, resulting from ingrowth of the keratinizing

squamous epithelium from the external acoustic meatus

to the middle ear through the tympanic membrane. It

was represented on the CT scan in the form of a soft-

tissue mass-like opacity in the middle ear cavity and

mastoid antrum associated with smooth bony erosion of

the ossicles and expansion of adjacent structures [22].

CT examination of patients with osteopetrosis showed

conductive hearing loss, and this was attributed to

exostosis projection into the middle ear cavity, calcified

and sclerotic ossicles, recurrent otitis media, and poor

aeration of the mastoid air cells, with no evidence of

internal auditory canal narrowing [23–25]. A CT scan of

Paget’s disease of the skull showed thickening of the

auditory ossicles and stapes suprastructure was not

visible; these findings explain the hearing impairment

in patients with Paget’s disease [26].

High-resolution CT of the temporal bone is the method

of choice for the evaluation of ossicular chain integrity

and tympanic cavity walls. Axial high-resolution CT scans

can ordinarily show the exact nature and placement of

the ossicular fractures and dislocations. High-resolution

CTof the middle ear is a useful noninvasive technique; it

can detect the extent of the disease, exact location,

structures involved, and possible bone erosion. It can be

addressed in cases of traumatic and nontraumatic

opacified middle ear, acute coalescent otomastoiditis,

and chronic otitis media. Recently, virtual endoscopy and

three-dimensional reconstructions of the middle ear as

well as the tympanic cavity were used to assess middle

ear pathologies and ossicular injuries using the standard

high-resolution CT temporal bone as a template [27,28].

Patients and methodsThis study included 16 Egyptian individuals. They were

divided equally into two groups. The first group (group I)

had 14 bony ankylosed TMJ. They were selected from

those attending the outpatient clinic of the Department

of Oral and Maxillofacial Surgery, Faculty of Oral and

Dental Medicine, Cairo University, Egypt. The second

group (group II) included normal individuals of the same

age (range, mean) and sex distribution. They were

recruited from among patients with other medical

conditions of the temporal bone in whom no abnormal-

ities of the middle ear were detected; consequently, CT

was not performed specifically for the middle ear to avoid

extra radiation hazard. The condition was explained and

their consents were obtained. Every patient of group I

was subjected to laboratory routine investigations for

general anesthesia. Surgically, the preauricular approach

was used in all patients to gain access to the TMJ area.

Gap arthroplasty was applied to release the TMJ

ankylosis. MEVs were measured preoperatively and 3

months postoperatively.

Radiographic assessment for ankylosis and for the middle

ear was performed using multislice CT scan. Volumetric

measurement of middle ear was estimated semidigitally.

MEV was calculated starting from the tympanic mem-

brane to the bony part of the Eustachian tube.

Comparison of the MEV in TMJ ankylosis patients with

normal individuals was carried out. Also, comparison

between MEV preoperatively and postoperatively for

detection of the effect of gap arthroplasty on the MEV

was carried out. The data were tabulated and analyzed

statistically (Fig. 1).

Radiological assessment of the middle ear

All the CT examinations were performed using a slice

multidetector CT scanner (Aquillion 64; Toshiba, Tokyo,

Japan). Scanning was performed on the standard axial

plane using the helical technique (a field of view of

18 cm, a pitch of 0.562, a rotation time of 0.35 s, a section

thickness of 0.5 mm, and a matrix of 512� 512). The

patients were scanned in a supine position to obtain

the image plane parallel to the orbitomeatal line. All the

image data sets were transferred from the CT scanner

to the PC workstation and the data sets were analyzed

using the three-dimensional medical imaging software

(Medicor imaging Charlotte, North Carolina, USA) (on

vitra workstation). MEVs were measured using the digital

Fig. 1

Axial, coronal, and three-dimensional reconstruction images of computed tomography showing an ankylosis bony mass.

TMJ bony ankylosis and middle ear volume Dehis et al. 73

image processing CT program. The area of the air-

containing cavity was measured semiautomatically. A

volume of interest was applied manually on each slice.

The volume of the air-containing cavity at each slice was

computed by clicking on the air cavity within the volume

of interest. The total volume of the air-containing cavity

was calculated as the sum of the volumes of the air-

containing cavities of each slice (Figs 2 and 3).

Radiological measurements of middle ear volume

(1) MEV of the right and left ears of the patient group

(group I).

(2) MEV of the right and left ears of the control group

(group II).

(3) Equality test of the right and left MEV.

(4) Comparison of the preoperative results of MEV of

TMJ ankylosed joints (group I) versus control joints

(group II).

(5) Comparison between preoperative and postoperative

results of MEV of ankylosed joints (group I).

Analysis of patients data

Group I included 14 bony ankylosed joints in eight patients

(two men and six women, age range 18–45 years and mean

age 29.5 years). The etiology of ankylosis was trauma in 75%

of cases and congenital cause in the remaining 25%. The

preoperative interincisal opening ranged from 0 to 6 mm,

mean 3.2 mm. Seventy-five percent of cases had bilateral and

Fig. 2

Outline tracing of preoperative middle ear volume (group I).

Fig. 3

Outline tracing of middle ear volume (group II).

74 Egyptian Journal of Oral & Maxillofacial Surgery 2013, Vol 4 No 3

25% had unilateral involvement with fibrous ankylosis in the

contralateral sides. Previous surgical intervention for the

correction of TMJ ankylosis was reported in six patients:

one of them was operated three times, three patients were

operated two times, and two were operated only once.

Surgical procedure

Gap arthroplasty was performed to release TMJ ankylosis

through a modified preauricular incision under fiberoptic

nasoendotracheal intubation. Patients were admitted for

general anesthesia in the Dental Educational Hospital,

Faculty of Oral and Dental Medicine, Cairo University.

The operation was followed by physiotherapy for 6

months to prevent recurrence (Fig. 4).

ResultsThe postoperative course passed without incidence and

all patients resumed their normal activities early; they

were encouraged for early ambulation and were dis-

charged from the hospital at the second postoperative

day. Follow-up was performed at the outpatient clinic.

The maximum interincisal opening achieved at the end

of 3 months postoperatively ranged from 24 to 50 mm,

mean 35.3 mm.

Results of middle ear volume

Middle ear volume of right and left ears of the

patient group (group I)

On studying the MEV of right ears of the patient group,

it was found that the preoperative values obtained ranged

from 0.036 to 0.528 ml, with a mean of 0.26 ml. The

3-month postoperative volumes obtained ranged from

0.039 to 0.216 ml, with a mean of 0.09 ml (Table 1).

On studying the MEV of left ears of the patient group, it

was found that the recorded preoperative values ranged

from 0.043 to 0.676 ml, with a mean of 0.26 ml. The

recorded 3-month postoperative volumes ranged from

0.021 to 0.184 ml, with a mean of 0.07 ml (Table 1).

Fig. 4

(a) Preauricular incision. (b) Exposure of the ankylotic bony mass. (c) Initiation of cutting the ankylotic bony mass. (d) The gap obtained.(e) Intraoperative interincisal opening.

TMJ bony ankylosis and middle ear volume Dehis et al. 75

Middle ear volume of the right and left ears of the

control group (group II)

The MEV of the right ears of the control group ranged

from 0.742 to 2.193 ml, with a mean of 1.23 ml, whereas

that of the left ears ranged from 0.864 to 1.854 ml, with

a mean of 1.29 ml (Table 1).

Equality test of right and left middle ear volumes

On comparing the results of right and left MEVs of the

operated and the control individuals, it was found that

there was no statistical difference. Hence, the results of

the right and left ears of eight patients with ankylosis and

control individuals were summed up into 14 ankylosed

joints and 16 normal joints.

Comparison of preoperative results of middle ear

volume of ankylosed temporomandibular joints

(group I) versus control joints (group II)

On taking the mean MEV of the control group as a

reference point of comparison with the preoperative

mean MEV of ankylosed joints, it was found that there

was a significant deficiency in the MEV of ankylosed

joints preoperatively at a P-value of 0.000 (Table 2).

Comparison between preoperative and postoperative

results of middle ear volume of ankylosed joints (group I)

On comparing the MEV in ankylosed patients preopera-

tively and 3 months postoperatively, it was found that

there was a significant decrease in the volume post-

operatively at a P-value of 0.021 (Table 2; Fig. 5).

DiscussionThere is a close embryological, anatomical, and clinical

association between TMJ and the middle ear; for this, the

hypothesis of the present investigation was raised. It was

aimed to clarify the changes in MEV in response to TMJ

bony ankylosis. Gap arthroplasty is a standard technique

used widely in Egypt to release TMJ bony ankylosis. It

was utilized in this study as it is simple, atraumatic, and led

to fewer complications when compared with other

techniques. It has a low cost and can be used in low

socioeconomic communities. The effect of gap arthroplasty

on some aspects of the orofacial area was studied [29–32].

This research aimed to elucidate the changes that were

induced by gap arthroplasty on the MEV.

High-resolution CT was utilized in the current study as

it is an excellent technique for determination of

small abnormalities of the thin and complex bony

structures of the middle ear; for this reason, it is the

modality of choice in the study of conductive hearing loss.

Most middle ear lesions cause impairment of one or more

elements of the mechanical chain that transmits sounds

from the eardrum to the oval window [33,34].

The current research showed a marked statistically

significant deficiency of the preoperative MEV in

the TMJ bony ankylosis sample when compared with the

control group. The same findings were observed when

compared with the international published results [35–37].

Skeletal changes associated with TMJ bony ankylosis

extended to include facial skeleton; the detected decrease

in MEV of the current study seems to be responsive to

these changes. These findings could be attributed to the

lack of functional stimuli transmitted from the jaw to

the temporal bone by direct articulation with TMJ and

indirectly through the temporalis muscle and its related

fascia as well as the styloid process. This consequently

interferes with the growth and development of the

temporal bone as a whole and its contents, including

Table 1 MEVs (ml) of the right and left ears in patients and controls both preoperatively and 3 months postoperatively

Patients and controls Preoperative MEV (Rt) Preoperative MEV (Lt) Postoperative MEV (Rt) Postoperative MEV (Lt) MEV control (Rt) MEV control (Lt)

1 0.181 0.067 0.039 0.042 1.113 1.2892 0.036 0.043 0.216 0.184 0.976 1.0433 0.528 0.676 0.058 0.048 0.800 0.9914 0.229 0.384 0.051 0.054 1.131 1.3195 0.071 0.045 0.049 0.021 1.878 1.8546 0.511 0.324 0.078 0.052 0.742 0.8647 0.365 0.383 0.075 0.085 2.193 1.8118 0.156 0.122 0.156 0.093 1.041 1.160Mean 0.25963 0.2555 0.09025 0.07238 1.23425 1.29138

Lt, left; MEV, middle ear volume; Rt, right.

Table 2 Paired sample t-test for comparison of MEV of preopera-tive MEV of group I with the control group (group II) and forcomparison of preoperative with postoperative MEV (group I)

Mean t-test d.f. P-value

MEV preoperatively (group I) 0.255 –7.849 28 0.000MEV control (group II) 1.262MEV preoperatively (group I) 0.255 2.623 13 0.021MEV postoperatively (group I) 0.086

MEV, middle ear volume.

Fig. 5

0

0.2

0.4

0.6

0.8

1

1.2

1.4

(Preop (group I (Postop (group I (control (group II

mean of MEV

(Preop (group I

(Postop (group I

(control (group II

Mean middle ear volume in group I (preoperative and postoperative)and group II.

76 Egyptian Journal of Oral & Maxillofacial Surgery 2013, Vol 4 No 3

the middle ear. This explanation needs further investiga-

tion to explore the deficient aspect of the temporal bone

and its relation in patients with TMJ ankylosis. This

finding is supported by hearing impairment in ankylosed

patients detected in a previous study [38].

The postoperative assessment of MEV showed a statis-

tically significant decrease in response to gap arthroplasty.

This might be ascribed to the negative pressure of the

middle ear at that time with an inward movement of

the tympanic membrane. Small MEV in ankylotic

patients makes any change in the volume, however small,

critical or significant. Surgery of TMJ ankylosis, although

it deals with a huge bony mass, usually needs delicate

manipulation to release the jaw from the forest of

multiple abundant vital structures. In contrast, an

atraumatic surgery in close proximity to the external

and middle ears is highly needed. Surgical trauma and its

associated vibration, effusion and collected hematoma are

accused to be responsible for the decrease in MEV.

AcknowledgementsConflicts of interest

There are no conflicts of interest.

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