R E S T R I C T E D M A N D I B U L A R M O V E M E N T S D U E T O O S T E O C H O N D R O M A OF T H E C O R O N O I D PROCESS

By GEORGE PAP, M . D . , and E. FRIEDMAN, M . D .

From the Departments of Plastic Surgery and Radiology, Beilinson Hospital, Petah Tikva, Israel

THIS condition was described by Shackelford and Brown (I949), and our case is presented under the same tide. In our previous experience restriction of mandibular excursion due to involvement of the coronoid process was always secondary to an injury to the zygoma and zygomatic arch. This patient was

FIG. I FIG. 2

Fig. I . --Slight asymmetry of the face is noticeable due to enlargement of the malar prominence.

Fig. 2.--Pre-operative view. Opening of the mouth is restricted to less than i cm.

referred by his dental surgeon because o f trismus of an undetermined origin and acute dental pain, the latter being due to a carious molar tooth which was inaccessible, due to the trismus.

CASE REPORT

H i s t o r y . - - T h e patient was a man of 30 years, who reported that some five years ago he received a blow on the cheek from a fist which was armed with a " knuckle-duster." Some twelve months later he noticed a hard, painless swelling of the left zygoma below the level of the eye. After some further three years the swelling had increased in size and there was definite asymmetry o f the face (Fig. I). At this time a biopsy was performed, and he was assured that no treatment

x69

170 BRITISH JOURNAL OF PLASTIC SURGERY

was necessary, but he became aware of a progressive limitation of mandibular movement which, by the time of admission, was reduced to a distance of I cm. between the edge of the incisor teeth.

On examination the patient's general condition was good and all laboratory investigations were within normal limits. There was a marked swelling of the left zygoma, which on palpation was hard, smooth, and extended into the left orbit. There was no interference with vision or with movements of the left eye. Vertical mandibular movement was limited to less than I cm. There was a

FIG. 3 FIG. 4

Fig. 3.--Pre-operative X-ray taken in the lateral position.

Fig. 4.--Pre-operative X-ray taken in the occipito-mental position.

marked deviation of the jaw to the left on opening, and the space between the upper and lower molars on that side was limited to 2 mm. Both condylar heads moved freely in the fossa:, within this range, thus suggesting that the cause of the trismus was extra-articular (Fig. 2).

Radiographic Findings.--Routine postero-anterior and lateral projectioias (Fig. 3) of the skull disclosed an abnormal mass in the left zygomatic region. The lesion was best demonstrated, however, in axial and semi-axial (Figs. 4 and 5) projections. It appeared as a bony prolongation of the coronoid process about 12 mm. wide at the base extending forwards to the antero-inferior region of the temporal fossa where it formed a mushroom-like head of some 2 5 mm. diameter, the body of the zygoma and zygomatic arch being expanded by this mass and the infero-lateral part of the orbit elevated. Tomography disclosed the coronoid process partly embedded within this structure of pathological bone which was of homogenous density save in the mushroom-like head where it was of a spongy nature. There was a clear line of demarcation between the head and the zygoma and orbital floor. A tentative diagnosis of exostosis or osteoma of the coronoid process was made, but in the differential diagnosis myositis ossificans was also considered.

T rea tmen t . - - I t was expected that resection of the bony mass and coronoid process would restore full vertical movements of the mandible, but that it was

RESTRICTED MANDIBULAR MOVEMENTS DUE TO OSTEOCHONDROMA OF CORONOID PROCESS 171

unlikely that this could be carried out through a submandibular incision alone; thus a double approach was planned. Under endotracheal anmsthesia with nasal intubation, the mandible was exposed through a submandibular incision. The base of the coronoid process was found to be enlarged but the insertion of the temporal muscle appeared normal. The process was divided through its base by chisel and curved rongeur, and was then freely movable but could not be delivered by this route because of the expanded head, nor was the range of

FIG. 5

Pre-operat ive X- r ay taken in a basilar posi t ion with arrows poin t ing to the turnout .

mandibular movement increased at this point. A second incision was made along the lateral orbital wall (modified after Kr6nlein) and extended into the scar over the zygomatic prominence. Here the anterior surface of the zygoma was exposed, a thin layer of bone removed, and a pseudo-joint cavity found containing the head of the tumour which extended inwards to elevate the lateral orbital floor. The tumour was separated from the surrounding bone by a thick fibrous membrane. On severing the tendinous insertion of the temporalis, the whole specimen was easily delivered. The wounds were closed in two layers with drains for twenty-four hours. The next day mandibular movement had increased to 2 cm. and with chewing exercises over the next three months the vertical range of movement increased to some 3"5 cm. (Fig. 6).

Histology.--The base of the mass consisted of normal compact and cancellous bone, but the expanded head was formed of cancellous bone covered by a thin layer of cartilage (Fig. 7), with some islands of cartilage lying just beneath the surface. These findings demonstrated an overgrowth of bone tissue and cartilage in a definite tumour-like fashion, although the microscopic pattern is that of normal bone and cartilage (Fig. 8). It is assumed that the initial cartilaginous overgrowth subsequently ossified into trabecular bone. The tumour has been classified as a benign osteochondroma, but this differs very little from osteocartilaginous exostosis seen in long bones (Professor J. Casper).

172 BRITISH JOURNAL OF PLASTIC SURGERY

FIG. 6 FIG. 7

Fig. 6.--Post-operative view showing free unlimited opening of the mouth to 3"5 cm.

Fig. 7 . - -The resected coronoid process cut after preservation in formalin.

FIG. 8

Low power section of part of the turnout, showing trabecular bone and covering thin layer of cartilage.

RESTRICTED MANDIBULAR MOVEMENTS DUE TO OSTEOCHONDROMA OF CORONOID PROCESS 173

DISCUSSION

Few cases of osteochondroma of the coronoid process have been described, Shackelford and Brown (1949) reporting three cases. They believe, however, that it is more common than is generally recognised because of the difficulty in radiological interpretation. Our own case has a history of injury, but trauma was absent in their series. Their exposure of the tumour was gained by resecting the zygomatic arch which, in the closing stages of the operation, was replaced and wired into position, thus giving a good cosmetic result. In our case the contour defect resulting from removal of a portion of the zygoma will demand further surgical restoration.

The writers are indebted to Dr H. Markowicz for assistance in the planning and execution of treatment of this case, to Professor J. Casper for the pathological report, and Mr D. C. Bodenham of Bristol for advice and assistance in the preparation of the manuscript. We also wish to thank Mrs K. Norton for the illustrations.

REFERENCE

SHACKELFOmg, R. T., and BROWN, W. H. (1949). ft. BoneJt. Surg., 3xA, lO7. LICHTENSTEIN, L. (I952). "Bone Tumours." St Louis : C. V. Mosby Co.