Osteochondromas are one of the most common benign tumours of bone, but they
are rare in the craniofacial region. These condylar tumours have been
variably treated, including resection through local excision or condylectomy
with or without reconstruction.
Methods
A case of osteochondroma of the mandibular condyle and cranial base arising
concurrently in the 76 years old patient was presented. The surgical
excision of the skull base lesion and condylectomy with immediate
reconstruction of temporomandibular joint was applied.
Results
Based on the history, clinical examination and radiographic findings,
osteochondroma of the skull base was diagnosed, with a concurrent lesion of
the condylar process. Treatment methods for this patient included excision
of the skull base tumour and condylectomy with immediate temporomandibular
joint reconstruction using appropriately sized stock total temporomandibular
joint prosthesis. At the 24 month follow-up, patient was free of pain and
her maximal incisal opening was maintained, with no radiographic evidence of
tumour recurrence or failure of the device.
Conclusions
Temporomandibular joint stock total replacement prosthesis became a good
option to reconstruct both the fossa and the condyle in a one-stage surgery,
due to the fact that both the condylar/mandibular and the fossa implants
were stable in situ from the moment of fixation, with a good outcome at 24
month follow-up, with no loosening of the screws nor failure of the
device.
Osteochondromas are one of the most common benign tumours of bone, representing
approximately 35% to 50% of all benign tumours and 8% to 15% of all primary bone
tumours. These tumours are rare in the craniofacial region (0.6%) [1], with the coronoid process of the mandible
and the mandibular condyle as the most common sites of occurrence [2-4]. When
skull base osteochondromas are included, there is a comparable number of case
reports mostly located around the temporomandibular joint (TMJ) [5,6]. A
relatively high frequency of osteochondromas around the TMJ can be explained
embryologically when it is considered that the region from the mandibular lingual to
the anterior process of the malleus is derived from the part of Meckel's cartilage
not replaced by mandibular bone and that remnants of this embryonic tissue may still
persist. But, concurrent osteochondroma involving the mandibular condyle and
ipsilateral cranial base is extremely rare, with only one previous case report
[7].
The alternative descriptive name of osteocartilaginous exostosis recognizes the
uncertainly about the fundamental nature of the lesion. Whether it is in fact
developmental, truly neoplastic, or even exuberant repair activity is still
controversial [7].
Clinical symptomatology of patients with osteochondromas may include vertical
elongation of the face on the affected side with mandibular asymmetry, malocclusion
with cross-bite on the contralateral side and lateral open bite on the affected
side, TMJ dysfunction symptoms such as pain.
Radiographically, these lesions are radiopaque and are easily identified on computed
tomography (CT). Due to their distinct borders, these tumours can be followed with
CT as well as plain radiography.
These condylar tumours have been variably treated. Treatment has included resection
through local excision or condylectomy with or without reconstruction, using a
variety of techniques, such as arthroplasty [8,9], vertical ramus osteotomy
[10], autogenous costochondral graft
[11] or total joint prosthesis [7].
In this article, authors present a case of osteochondroma of the mandibular condyle
and cranial base arising concurrently in the same patient. The surgical treatment
was an excision of the skull base lesion and condylectomy with immediate
reconstruction by means of a stock total temporomandibular joint prosthesis.
CASE DESCRIPTION AND RESULTS
A 76 years old woman was referred to Department of Oral and Maxillofacial Surgery,
Son Dureta University Hospital, Palma de Mallorca, Spain for evaluation. She
complained of severe right preauricular pain increasing with jaw movement. Patient
described it like trigeminal neuralgia. The pain had begun one month before and she
had been prescribed anti-inflammatory and muscle-relaxing agents only.
Physical examination showed a class I inter-arch relationship, with metal and ceramic
dental restoration over implants and teeth. No facial asymmetry, occlusal changes
nor preauricular swelling were noticed. A slight limitation (30 mm) in mouth opening
was observed.
The panoramic radiograph showed a shortening of the right condylar neck and a
flattening and widening of the right condylar head. The left TMJ was normal. CT
showed a severely deformed right condyle with medial bony projections. This was
associated with a bony mass at the base of the temporal bone and the articular
fossa, with a pseudoarthrosis between the skull base tumour and the deformed condyle
(Figure 1A,B). Due to the proximity to
the foramen ovale, the carotid canal and the stylomastoid foramen, magnetic
resonance imaging (MRI) was performed to further delineate the anatomy of the tumour
and its relationship with the surrounding structures. Neither the CT scan nor the
MRI showed any evidence of intracranial extension.
Preoperative patients CT scan.
A = coronal view showing a deformed right condyle with medial bony
projection. The right skull base and fossa are also affected.
B = axial view with a radiopaque image in the right temporomandibular joint
that suggests an osteochondroma.
Based on the history, clinical examination and radiographic findings, osteochondroma
of the skull base was diagnosed, with possibly a concurrent lesion of the condylar
process.
Treatment considerations for this patient included excision of the skull base lesion
and condylectomy with delayed or immediate reconstruction. Reconstructive modalities
included an autogenous costochondral graft or a total joint prosthesis. A thorough
explanation was given to the patient with regard to the risks and benefits of each
of the reconstructive modalities. She also was made aware of the fact that completed
excision of the lesion at the skull base would not likely be possible because of its
relationship to key anatomic structures.
The patient was taken to the operating room and intubated using a fibreoptic
nasendoscope. The right TMJ was approached through a preauricular incision. An
osseous mass that involved the mandibular condyle and the zygomatic process with a
line of demarcation between both structures was exposed (Figure 2). It was excised by means of osteotomies through the
condylar neck and the zygoma and, using periosteal elevators, the specimen could be
removed in 2 pieces. Further tumour removal at the cranial base using microsurgical
techniques was then completed.
Photograph showing an osseous mass involving the right condyle and the
zygoma, with a line of soft tissue between both structures.
Once the tumour was removed, an immediate TMJ reconstruction could be performed, by
means of an appropriately sized stock total TMJ prosthesis (Biomet/Lorenz® Warsaw,
IN, USA) (Figure 3). The fossa and cranial
base were recontoured with a round bur. Then a medium-sized prosthetic fossa was
applied to the newly created fossa and, after bony recontouring, was fitted and
secured to the lateral aspect of the zygomatic process with six, 2.0 mm diameter
titanium screws. Maxillomandibular fixation (MMF) was placed into her dental
occlusion. A submandibular incision was then made, with conventional exposure of the
lateral aspect of the ramus. The mandibular component of the prosthesis was sized
and a medium extended prosthetic ramus was inserted through the submandibular
incision, was properly seated in the fossa and was secured to the ramus with six,
2.7 mm diameter titanium screws. MMF was released and dental occlusion and
prosthetic TMJ movement were checked. All the incisions were sutured in layers.
Photograph showing temporomandibular joint fossa and condylar implants fitted
in place.
The histologic findings confirmed the diagnosis of osteochondroma of the mandibular
condyle and skull base.
A week after the intervention, the patient did not experience trigeminal pain and her
maximal incisal opening was 30 mm. At the 24 month follow-up, she was free of pain
and her maximal incisal opening was maintained, with no radiographic evidence of
tumour recurrence or failure of the device (Figure
4).
High-resolution CT scan 18 month after operation with computed
three-dimensional reconstruction, showing no evidence of tumour recurrence
or failure of the device.
DISCUSSION
Osteochondromas have been characterized as cartilage-capped bony protrusions that
present themselves on the external surface of a bone [12]. As a reflection of the combined tissue involvement, this
lesion has been named osteocartilaginous exostosis and osteochondroma. Although
there are many theories regarding its pathogenesis, it is still uncertain whether
the lesion this lesion is developmental, neoplastic or reparative. These theories
include the growth of herniated cartilage precursor cells, growth of displaced
epiphyseal cartilaginous cells that originated in the metaphysic, hyperplasia of
cartilaginous cells due to tensional forces, retained cartilaginous rests that
undergo growth or hyperplasia, and tumour cells arising from pleuripotential cells
in the periosteum [7].
Although frequently occurring in the axial skeleton, osteochondromas are rare in the
maxillofacial region [1]. They have been
reported in diverse locations of the craniofacial area that include the zygoma
[13], maxillary sinus [14], the skull base [5], the glenoid fossa and mandible [6], where the most common sites are the coronoid process and the
condyle [2-4]. Mandibular osteochondroma has also been reported to occur in the
ramus, body, angle and symphyseal regions, however, concurrent osteochondroma
involving the skull base and the ipsilateral condyle is extremely rare, with only
one previous case report [7].
Typical facial features of condylar osteochondromas include facial asymmetry,
malocclusion with open-bite on the affected side, and/or prognathic deviation of the
chin and cross-bite to the contralateral side. Mouth opening is in normal range in
most of the cases because of the pseudoarticulation around the mass. When the facial
asymmetry is not noticeable, these tumours are usually diagnosed as TMJ
dysfunctions, been pain the predominant symptom in these patients [9].
Radiographically, on plain films, these tumours can appear as exophytic masses with
mixed density and a sclerotic appearance. CT and MRI examination are mandatory in
evaluating cases of large tumours, with possible involvement of cranial or vascular
structures.
Histologically, these lesions are composed of well-circumscribed bone and
cartilaginous cap. Underlying the cartilaginous cap is the bony component, which may
also have proliferating chondrocytes overlying bone that resembles the condyle as it
undergoes endrochondral ossification [6].
The recurrence rate for solitary osteochondromas in long bones is approximately 2%,
and there is only one recurrence of a condylar osteochondroma reported in the
literature, which occurred a year after its excision in multiple pieces [9].
Solitary osteochondromas have a 1% risk of malignant transformation [9]. Skull base osteochondroma has been reported
to undergo sarcomatous degeneration; however, this is an extremely rare occurrence
[7].
The treatment protocol for these condylar tumours is controversial. Local resection
or conservative condylectomy with recontouring of the residual condylar neck and
repositioning of the articular disc is a viable option for treatment of
osteochondromas that involve the head of the condyle, without the extension of
tumour into the neck [8,9]. Another acceptable reconstructive procedure for condylar
lesions where the ramus is not involved could be superiorly moving the posterior
ramus border by ramus osteotomy, reconstructing a neocondyle with satisfactory TMJ
function, thus avoiding a donor site deformity [10]. In cases of osteochondroma where the condylar head and neck require
removal, a total condylectomy and simultaneous joint reconstruction is recommended
by most surgeons, due to the benign nature of these lesions, the low likelihood of
recurrence and the importance of the ramus height in TMJ function [7,8]. At
present, autogenous bone grafts (costochondral or sternoclavicular grafts) are
frequently considered for condylar reconstruction, but carries inevitable
disadvantages, such as donor site morbidity, exploration of two surgical sites and
bone resorption [11,16,17]. Total joint
prosthesis is another alternative of TMJ reconstruction, especially when both
condyle and fossa have to be reconstructed after tumour resection [7]. Several papers have reported that TMJ
alloplastic replacement is a safe, effective and reliable option in severely
degenerate joints, with predictable outcomes and an improvement in the quality of
life in these patients [18-21]. Some advantages of alloplastic joint
reconstruction are: 1) that the physical therapy can start immediately after
implantation, 2) a secondary donor site is obviated, and thus surgery time and
potential morbidity are reduced, and 3) the TMJ´s anatomy and function can be
mimicked. Disadvantages include: 1) the cost of the device, 2) material wear and
potential failure, and 3) restricted use in the growing patient [20,21].
Customized prosthetic systems are frequently designed and manufactured for each
specific situation. This ensures intimate contact between the host bone and the
device, thus decreasing micromotion under functional loading which may lead to
loosening of the fixation and premature failure of the prosthesis [22]. The alternative use of a stock prosthetic
system, which is provided in different sizes and shapes for both the
condylar/mandibular and the fossa components, allows adaptation of the host bone to
the implants [23]. In theses stock systems
are not necessary a previous design of their components, and they are indicated for
immediate TMJ reconstruction in not planned cases. On the other hand, the
manufacture of custom devices needs a presurgical work-up, where an accurate
three-dimensional plastic model of the patient´s joints is constructed from CT data.
The prostheses are manufactured from this model with this process taking 6 - 8
weeks. In the present case, due to the severity of pain, the patient refused to wait
for this period of time. She also rejected a two-stage procedure, consisting of a
tumour resection with a delayed reconstruction.
CONCLUSIONS
Under these considerations, a Biomet/Lorenz® stock prosthesis became a good option to
reconstruct both the fossa and the condyle in a one-stage surgery, due to the fact
that both the condylar/mandibular and the fossa implants were stable in situ from
the moment of fixation, with a good outcome at 24 month follow-up, with no loosening
of the screws nor failure of the device.
ACKNOWLEDGMENTS AND DISCLOSURE STATEMENTS
Dr. Miguel Angel Morey-Mas is a Surgeon Consultant for Biomet Microfixation,
LLC.