ORIGINAL ARTICLE
C2 prosthesis: anterior upper cervical fixation device
to reconstruct the second cervical vertebra
Dezs}o Jeszenszky Æ Tama´s Fu¨lo¨p Fekete Æ
Robert Melcher Æ Ju¨rgen Harms
Received: 22 April 2007 / Accepted: 24 June 2007 / Published online: 14 July 2007

Springer-Verlag 2007
Abstract Destruction of the second cervical vertebra
leads to a highly unstable situation. Reconstruction is dif-
ficult because the axis plays a central role in rotatory
movements and has a unique function in redistributing
axial loads. The axis transfers the axial load of the two
lateral masses of the atlas to three surfaces on the third
cervical vertebra: the two articular facets and the vertebral
body. As reconstruction is difficult and the instability in
this region is life threatening, pathological processes are
often treated less radically compared to other areas of the
cervical spine. However, this more moderate approach may
result in worse outcomes and prognoses. This paper pre-
sents the development of a new implant (C2 prosthesis) and
two illustrative cases describing the implementation of this
new implant. The C2 prosthesis provides anterior support
and therefore allows a more radical surgical approach.
Keywords Axis neoplasm
Spondylectomy–
vertebrectomy
Spinal instability
C2 prosthesis

Anterior support
Introduction
Destruction of the body of the second cervical vertebra may
develop due to primary or secondary bone tumours or
infections. The treatment of these pathological processes
often requires surgical resection, which may further increase
instability [14]. Current treatment strategy consists of tu-
mour removal, decompression and posterior fixation [2–4, 8,
9, 13, 15]. If the vertebral body of the axis—including the
superior facet joints—is not present either by the destruction
of a pathological process or by surgical removal, posterior
fixation is widely extended. The usual extent of posterior
fixation is from the occiput down to the lower subaxial spine
and external immobilization is also applied [3, 6, 9, 13]. This
fixation has to exceed the biomechanically compromised
segments because the missing anterior support has to be
compensated for. Some surgeons also perform anterior
reconstructions with bone grafts and screws or bone grafts,
plates and screws. However, such anterior reconstruction
alone is insufficient, the posterior occipito-cervical fixation
and external immobilisation cannot be avoided. These
combined anterior and posterior approaches are limited to
isolated case reports or small series [1, 8, 10, 11]. The low
numbers of anterior reconstructions might be due to the
difficulty in achieving an adequate connection between the
C1 lateral masses located laterally and the C3 vertebral body
in the midline.
To meet the special anatomical and biomechanical
requirements of reconstructing the axis, the first and senior
authors designed a C2 prosthesis by integrating the Harms
anterior transoral plate and titanium mesh cage. An implant,
that restores stability following total removal of the second
cervical vertebra, without the need for fixation of the atlanto-
occipital joints, has, to the authors’ knowledge, not been
described before.
D. Jeszenszky (&)
T. F. Fekete
Schulthess Clinic, Spine Center, Lengghalde 2,
8008 Zurich, Switzerland
e-mail: dezsoe.jeszenszky@kws.ch
R. Melcher
J. Harms
SRH Klinikum Karlsbad-Langensteinbach,
Center for Spine Surgery, Guttmannstrasse 1,
76307 Karlsbad, Germany
123
Eur Spine J (2007) 16:1695–1700
DOI 10.1007/s00586-007-0435-6

Materials and methods
During surgical interventions of C2 resection the implants
used to reconstruct the axis were serially modified. As the
first step of development a transoral T-shaped plate and a
Harms cage was assembled prior to each surgery up to
1997 (Fig. 1a–d, g). Later a shorter and wider titanium
cage to provide support for the C1 lateral masses was ad-
ded (Fig. 1e, h). The prosthesis was custom-made for each
patient. The size of the implant was based on measure-
ments of preoperative radiological data. However, later it
turned out that two different sizes (large and small) were
sufficient for all patients. Therefore the design was finally
changed to accommodate for both sizes by intraoperatively
shortening the larger size implant when necessary
(Fig. 1f, i).
Illustrative case report 1
A 16 year-old patient had a history of neck pain radiating
to the occipital region. MRI scans showed a tumour mass at
the level of C1 and C2. Suboccipital craniectomy, C1 and
C2 laminectomy, and a partial tumour resection were
performed through a posterior transdural approach in
another hospital (Fig. 2). The histology revealed chord-
oma. The patient had long tract signs and lower limb ataxia
at the postoperative period, which spontaneously resolved
in a few weeks. The patient was referred to our hospital for
complete tumour removal before proton beam therapy.
We removed the C2 vertebral body through a high
cervical left anterolateral approach. Following total tumour
removal it was evident that the atlas was not involved, the
lateral masses and anterior arch were intact. We then
implanted the C2 prosthesis. The C1 lateral mass screws
were inserted through two stab incisions on the pharynx in
a transoral approach. We turned the patient and performed
a posterior C1–C3 fixation using polyaxial screws and rods.
The patient was mobilised without any orthosis and the
recovery period was uneventful. Postoperative radiographs
showed well-situated implants (Fig. 3). There was no
evidence of residual tumour on the postoperative MRI.
Illustrative case report 2
A 51 year-old patient suffered from progressive neck pain.
Radiological investigation revealed a left-sided tumour
partially destroying the C2 and C3 vertebral bodies.
Posterior decompression, C2, C3, C4 laminectomy and
tumour resection was performed in another institution. The
result of the histological analysis was chordoma.
The patient was referred to our hospital to complete the
removal of the tumour before a proton beam irradiation.
We performed a posterior fusion from C1 to C5, using
polyaxial lateral mass screws and rods, and restored a
lordotic curve. We decided to include the C4–5 segment in
the stabilisation, because of significant instability from
previous surgery. At that stage we turned the patient and
Fig. 1 Evolution of C2 prosthesis. a–c Original transoral T-shaped
plate. d Integration of transoral plate with a titanium mesh cage. e A
wider elliptical cylinder cage was added to provide support for the
lateral mass of atlas. f final version. The horizontal part of the plate
was shortened to ease insertion and the caudal end of the implant was
changed to provide longitudinal adaptability. g–i Corresponding
superior view of the implants from d to f
Fig. 2 Signs of C1 and C2 laminectomy and kyphotic angulation are
visible on the lateral cervical spine X-ray
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performed total tumour removal, an anterior C2, C3
vertebral body resection and a left-sided vertebral artery
resection. We also performed a C4–5 discectomy and fu-
sion. A custom-made C2 prosthesis was used to reconstruct
the anterior aspect of the spine. The length of the cylin-
drical cage was long enough to replace both the C2 and C3
vertebral bodies. The right third of the C2 vertebral body
seemed to be intact and preservation was possible. The
wing of the C2 prosthesis on the right side was removed
accordingly (Fig. 4). The anterior plate of the prosthesis
was made especially long to incorporate the C5 vertebra
into the fusion. The third approach in the same session was
transoral. Two screws to the lateral mass of C1 were
inserted through two stab incisions on the posterior wall of
the pharynx to stabilise the cranial end of the T-shaped
plate of the C2 prosthesis.
The patient was extubated on the third postoperative day
and mobilised without any external immobilisation device.
Unfortunately, there was a haematoma formation at the
anterior surgical site so the anterior wound on the tenth
postoperative day was revised and the haematoma was
evacuated. There was no implant failure and there was no
neurological complication. The postoperative radiographs
showed a good alignment of the cervical spine (Fig. 5).
Later the patient received proton beam therapy. At
2-year follow-up the patient is still tumour-free. The
patient is fully reintegrated into normal daily activities.
Results: description of C2 prosthesis
The prosthesis consists of a T-shaped plate, a long cylinder
mesh cage, and a short elliptical cylinder mesh cage
(Fig. 1f, i). The width of the elliptical cylinder cage is
25 mm, the depth is 14 mm and the height is 10 mm. The
diameter of the cylinder cage is 14 mm. The elliptical
cylinder cage is situated at the cranial end of the main
cylinder cage. The horizontal part of the T-shaped plate is
just above the main cylinder cage and the caudal part of the
plate extends below the main cylinder cage. All three
components are built together as a robust construct.
The elliptical cylinder cage provides axial support to the
inferior articular facets of the atlas. The load of the ellip-
tical cylinder cage is transferred to the caudally adjacent
vertebra via the main cylinder cage (Fig. 8).
Fig. 3 Postoperative radiographs show good positioning of the C2
prosthesis, the posterior screws and rods. The atlanto-occipital
segment was spared. The preoperatively seen kyphotic angulation
below the level of C3 was unchanged
Fig. 4 Axial CT image at the C2 level. The right half of the C2 body
was spared (arrows), so the right wing of the prosthesis was removed
accordingly to adapt to the situation
Fig. 5 Postoperative lateral an AP radiographs showing the prosthe-
sis replacing the partially and completely removed C2 and C3
vertebral bodies, respectively
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There is one hole on each side at the horizontal part of
the plate for screws to the lateral mass of C1. There are
four holes in two rows at the caudal end of the plate for two
screws to the next adjacent subaxial vertebral body. The
screw holes in the plate are shaped in a compressive
fashion, i.e. when tightening the screws the prosthesis is
compressed between the lateral mass of the atlas and the
caudally adjacent subaxial vertebra. The holes are designed
for bicortical screws with a diameter of 3.5 or 4 mm.
A combined anterolateral and transoral surgical
approach was used in both cases described here, however, a
transoral approach described by Schmelzle and Harms [12]
is generally used.
Transition of the large C2 prosthesis to the small size
There are four holes at the caudal end of the plate, as
mentioned above. By cutting off the distal end of the plate
with the two holes and, accordingly, cutting off the caudal
end of the mesh cage, the implant can be used where the
smaller size is needed. Furthermore, the prosthesis can be
individually modified intraoperatively just like the Harms
mesh cage. The shape of implant can be modified
according to the type and extent of resection.
The length of the main cylinder cage can depend on the
extent of resection. In individual cases an implant can be
made to reconstruct a longer segment of the cervical spine
with an appropriately long main cylinder cage and plate.
This allows for the resection of additional cervical verte-
bral bodies. The extent of resection this implant still
provides a safe support for is still unknown.
Discussion
Anatomical and biomechanical considerations
The craniovertebral junction is the most mobile portion of
the spinal column accounting for about half of all move-
ments in the cervical spine. The second cervical vertebra is
a transition between the atlas and the more typical third
cervical vertebra. The role of axis in the rotatory movement
of the atlantoaxial complex is well known, as its name
implies. However, the unique arrangement of its articular
facets, along with its special role in the redistribution of
axial load, is rarely discussed.
Unlike any other vertebra, the superior articular facets of
the axis originate from the vertebral body and extend
posteriorly onto the adjoining parts of the pedicles. The
inferior articular facets are situated at the junction of the
pedicles and laminae. Thus the superior articular facets are
anteriorly situated with respect to the inferior articular
facets. The consequences are twofold.
Fig. 8 This figure illustrates the anterior support and rotational
stability provided by the C2 prosthesis
Fig. 6 This figure illustrates the axial load redistribution of the atlas:
the 2-column system in the atlantoaxial complex and 3-column
system in the C2–C3 complex. The transparent red lines indicate the
axial forces through the upper cervical spine. The width of the lines
corresponds to the magnitude of force. The short black lines indicate
contours of the articular facets
Fig. 7 This figure illustrates how C2 body resection leads to
complete disconnection of the spine. The body of the axis vertebra,
along with the dens and superior articular facets, were removed
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First, the superior facets do not form an articular pillar
with the inferior facets. As C1 lacks a vertebral body, the
axial load of atlas is transferred through the C1–C2 facet
joints on both sides and can be regarded as a two-column
(left and right) system. The joints between the axis and the
third cervical vertebra are the C2–C3 facet joints and the
C2–C3 intervertebral disc. Thus, the C2–C3 joints repre-
sent a three-column system. The unique role of the body of
axis is to redistribute the two-column axial load of the atlas
into a three-column system of the subaxial spine (Fig. 6).
Second, the removal of the body of the axis includes
removal of the superior articular facets, thereby separat-
ing all the connections of the atlas to the pedicle of the
axis and thus to the inferior articular facets of C2. This
is practically a iatrogenic lesion in the pars interartical-
uris of the axis. Vertebral body resection at C2 level
through a single anterior approach results in complete
disconnection of the spine (Fig. 7)! This is equivalent to
a 360 surgical decompression/resection at any other
lower spinal level. Therefore following removal of the
body of the axis, both anterior and posterior structures
have to be reconstructed.
Clinical implications
Anterior reconstruction following axis removal is difficult
with the usual strut grafts. The caudal end of the graft
material can be secured to the subaxial vertebral body just
like anywhere else in the subaxial spine. However, to
establish a secure connection at the cranial end of the
conventional implant to the atlas is more difficult. The
cranial end of a conventional cage or the bone graft can be
secured either by an anterior plate or direct screws to the
tiny anterior arch of the atlas [11]. However, neither of
these methods provide safe fixation. The anterior support is
not reliable, because the bone graft or the cage with a
relatively small diameter can only support the thin anterior
arch of the atlas and not the more important lateral masses.
In addition to this the screw purchase in the arch of the
atlas is also very poor.
As a result the benefit of adding such an anterior support
is at least questionable. This is supported by the authors’
experience and by the small number of reported cases
where the fixation failed and/or extensive posterior fixation
and external immobilisation was used [11, 15].
Another difficult area following removal of the axis is
the counteraction of active rotational forces as muscles
acting to rotate the head still remain intact.
In contrast, the C2 prosthesis provides a reliable anterior
support and rotational stability. The implant presented in
this paper was designed to replace the above-mentioned
roles of the axis in axial load redistribution.
Application of the C2 prosthesis
The C2 prosthesis provides anterior support to the atlas by
the wide elliptical cylinder cage (wings of the prosthesis),
which transfers the axial loads of the C1 lateral masses to
the vertebral body of the subaxial vertebra in the midline
(Fig. 8). In addition, the prosthesis also provides rotational
stability as it is secured to the lateral masses of the atlas by
screws through the wide upper portion of the T-shaped
plate.
The corrugated ends of the elliptical cylinder cage are
designed to embed themselves at C1 lateral masses and at
the most cranially available subaxial vertebra to prevent
any translational or rotational movement. The plate
prevents migration of the implant toward the spinal canal.
As mentioned earlier, an additional posterior fixation
is unavoidable since the removal of the body of the axis
completely disconnects the spine. This is also supported
by a biomechanical study, where additional posterior
stabilisation improved stability of transoral atlantoaxial
plating [7]. The authors’ method of choice for a posterior
fixation is polyaxial screws and rods. However, the ex-
tent of the posterior fixation can be reduced in compar-
ison to previously described methods. In contrast to
formerly known methods of anterior support, a stable
connection is provided between the atlas and the anterior
construct. There are four screws in the atlas with the
anterior and posterior lateral mass screws. Anterior sup-
port is provided by the wings of the implant supporting
the lateral masses. As a consequence, an occipitocervical
fixation is unnecessary; the motion of C0–C1 segment
can be preserved. It also allows a more moderate ap-
proach to the rest of the subaxial spine, as the posterior
fixation can caudally end at the first available unaffected
subaxial vertebra.
The combined anterior C2 prosthesis and posterior
screw–rod construct achieves immediate stability. The safe
reconstruction allows a more radical approach to patholo-
gies affecting the axis. Thus the generally accepted con-
cepts in spine surgery can be applied in cases of destruction
of the axis vertebra. This might result in improved clinical
outcome, longer survival, and higher rate of curative
surgical interventions.
The decreased extent of fixation preserves unaffected
motion segments. Furthermore, the use of an external
orthosis is not necessary. All these improve the quality of
life.
To the authors’ knowledge, there has been no previously
published description of total axis removal without
immobilizing the C0–1 segment to date.
Initial results with the C2 prosthesis proved to be
excellent and without hardware failure [5].
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Conclusions
The new prosthesis was constructed to replace the second
cervical vertebra. This is the first implant which allows
complete removal of C2 while preserving C0–C1 motion.
The combined anterior C2 prosthesis and posterior screw–
rod construct achieves immediate stability, obviating the
need for an external orthosis and allowing for early
mobilisation.
The new implant allows a more radical surgical
approach to spinal pathologies involving the axis vertebra.
The implant can also be applied in a clinical setting, where
the pathological process exceeds the confines of the axis in
the caudal direction and destroys subaxial vertebrae. The
C2 prosthesis allows the application of concepts generally
accepted in other areas of spine surgery.
The benefit of this new fixation method is currently
being investigated in a clinical study with 10-year follow-
up at the time of writing.
Acknowledgments The authors would like to thank Biedermann-
Motech GmbH for construction and development of the C2 prosthesis;
Wilfried Matthis for all the support in biomechanics and the prepa-
rations of the 3D illustrations; Andreas Lu¨tscher for the photographs;
and Charles McCammon for helping to prepare the manuscript.
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