Large osteochondroma of the mandibular condyle treated by condylectomy using a transzygomatic approach

Abstract

This article presents an interesting case of osteochondroma of the mandibular condyle with multiple projections in a 42-year-old man. Owing to the large size of the lesion, surgical condylectomy was performed using a transzygomatic approach.

Osteochondroma is considered as a hamartomatous proliferation of cartilaginous tissue and is also known as osteocartilaginous exostosis. It is the commonest benign tumour of the long bones but is relatively rare in the mandible with fewer than 50 cases reported worldwide . Many of these cases have been described as a hyperplasia of the condyle and not as a discrete mass that arises away from the long axis of the mandibular condyle . Osteochondroma of the mandible is more common in the coronoid process, followed by the condyle and rare in other parts. In the condyle, it presents mostly on the medial and anterior aspects and rarely from the superior or lateral aspect . In most reports the size of the lesion has not been given.

These lesions have been treated by resection or condylectomy, but resection has been associated with recurrence in three cases . The surgical approach used is generally a preauricular or a submandibular approach either alone or in combination. As these lesions are usually not large, the use of a transzygomatic approach has not been described in the literature. This article reports a case of a large osteochondroma in a 42-year-old man treated by condylectomy using a transzygomatic approach.

Case report

A 42-year-old man presented with a complaint of progressive deviation of the mandible to the right side of 3 years duration ( Fig. 1 ). Clinically the mandible had deviated 14 mm. Mouth opening was restricted to 24 mm and the patient could not protrude the mandible to the left side. The mandible deviated further onto the right when opening the mouth. Posterior cross bite on the right side was also noted when in occlusion. There was no occlusal canting, nor was there any bowing of the inferior border of the mandible.

Fig. 1
( a – top left ) Clinical presentation of the patient; ( b – top right ) coronal section of CT scan showing extent of lesion and erosion of the greater wing of sphenoid. ( c and d bottom left and right ) Successive sagittal sections of CT scan demonstrating multiple projections of the lesion.

A CT scan revealed a well-defined 50 mm × 45 mm × 35 mm sized irregular pedunculated bony lesion with multiple projections arising from the medial margin of left condyle ( Fig. 1 ). One of the outgrowths was projecting anteromedially into the infratemporal fossa and extending up to the posterolateral wall of the maxillary sinus. A superior projection of the lesion extended to the greater wing of sphenoid, which it had thinned, and laterally the lesion extended to the zygomatic arch. There was also a small inferior projection. An anterior subluxation of the left temporomandibular joint was noted. The scan findings were more suggestive of an osteochondroma of the left mandibular condyle owing to the pedunculated nature.

A three-phase bone scan scintigraphy, carried out with 20 mCi of 99MTc-MDC revealed an increased uptake of the left mandibular condyle with increased vascularity on blood pool images, and the rest of the body showing normal radiotracer uptake. This ruled out multiple osteochondromas. The blood chemistry studies were within normal limits.

The patient was posted for resection of the tumour along with a condylectomy. Owing to the size of the lesion and its extension into the infratemporal fossa, a transzygomatic approach was considered ( Fig. 2 ). A hemicoronal incision ending in a preauricular extension up to the lobule of the ear was made through the skin, subcutaneous tissue and galea. In the temporal region this incision was up to the superficial layer of the temporalis fascia. At the root of the zygomatic arch, the superficial layer of the temporalis fascia was incised anterosuperiorly at a 45 angle. The periosteum was then incised to expose the zygomatic arch. Two plates were adapted, bridging the proposed osteotomy sites and screw holes marked. The zygomatic arch was osteotomized, hinged inferiorly on the masseter exposing the inferior aspect of the temporalis muscle, which was retracted anteriorly to expose the tumour mass ( Fig. 3 ). Inferiorly, anterior retraction of the temporalis brought about a clear exposure of the subcondylar and infratemporal region. An osteotomy cut was made inferior to the origin of the tumour at the condylar neck region. The tumour was then removed by stripping the attachments of the lateral pterygoid. The condylar stump was then reshaped and the wound closed in layers. Arch bars with guiding elastics were fixed for 1 month postoperatively to train the mandible.

Fig. 2
Surgical approach. ( a – left ) Relationship of the tumour mass (in dotted outline and marked as TU) to the zygomatic arch (Z), masseter muscle (M), and temporalis muscle (TE). ( b – right ) Tumour mass exposed (TU) after zygomatic arch osteotomy (with arrows denoting the osteotomy sites and Z denoting the residual part of the arch) and anterior retraction (R depicting a retractor) of the temporalis muscle (TE).

Fig. 3
( a – top ) Tumour mass exposed following zygomatic arch osteotomy, broad arrow depicting the osteotomized zygomatic arch, thin arrow pointing to the condylar process and its osteotomy margin, T denotes tumour mass; ( b – bottom left ) excised specimen showing the tumour mass (T), condylar stump (thin arrow); histopathologic features suggestive of osteochondroma; ( c – bottom center ) shows cancellous bone (B) covered with a proliferative cap of cartilage (C); ( d – bottom right ) shows cartilaginous inclusions (C) in variably sized cancellous bone trabeculae (B).
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Feb 8, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Large osteochondroma of the mandibular condyle treated by condylectomy using a transzygomatic approach
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