Vol.2, No.7, 405-410 (2013) Case Reports in Clinical Medicine
Copyright © 2013 SciRes. OPEN ACCESS
Use of long implants with distal anchorage in the
skull base for treatment of extreme maxillary atrophy:
The remote bone anchorage concept
Luc Vrielinck1*, Y i Sun1,2, Serge Schepers1,3, Constantinus Politis2,4, Sarah Van Slycke1,
Jimoh Olubanwo Agbaje1,4
1Oral and Maxillofacial Surgery, St. John’s Hospital, Genk, Belgium; *Corresponding Author: Luc.Vrielinck@zol.be
2Faculty of Medicine, Hasselt University, Diepenbeek, Belgium
3Oral and Maxillofacial Surgery, Faculty of Medicine, Gent University, Gent, Belgium
4Department of Oral Health Sciences, KU Leuven & Oral and Maxillofacial Surgery, University Hospitals Leuven, Leuven, Belgium
Received 14 July 2013; revised 20 August 2013; accepted 5 September 2013
Copyright © 2013 Luc Vrielinck et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
The objectives of t his s t udy are to present a new
concept of the bone anchorage using long im-
plants in remote bone sites and to discuss four
cases treated with this method. Our patients were
treated with long implants with a distant anchor-
age in the skull bone. The planning procedure,
the construction of the drill guide, and the sur-
gical protocol are described. In the clinical
cases described, all four patients were rehabili-
tated with the remote bone anchorage concept
using long implants anchored in the skull base.
Patients were followed for 5 - 12 years and the
implants remained present and stable in these
time periods. The skull base implant is a new
concept of bone anchorage using long implants.
It can be a solution for complicated clinical si-
tuations (often failed bone reconstructions and
implant placements) or an alternative for bone
grafting and maxillary augmentation procedures.
There is effective implant retention in the skull
base, an anatomical area that is often over-
looked for implant placement.
Keywords: Long Implant; Zygomaticus Fixture;
Skull Base Implant; Sphenoid Implant; Maxillary
Osseointegrated implants are commonly used in oral
and maxillofacial prosthetic rehabilitation [2,3,10]. Al-
though, advanced alveolar bone resorption combined
with increased maxillary sinus pn eumatisation, failure of
bone reconstruction, or maxillectomy procedures often
leave insufficient bone for the standard implant anchor-
age. Some bone graft augmentation methods lead to sig-
nificant patient morbidity, require lengthy healing times,
and are resource demanding [4,8]. The zygoma implant,
introduced by Brånemark, provided a new treatment al-
ternative that eliminates the need for bone grafting pro-
cedures in the lateral part of the maxilla [8,9,11,12].
However, rehabilitation of edentulous patients with
severe maxillary resorption with a fixed implant-sup-
ported prosthesis is only feasible when 2 to 4 standard
implants are placed in the anterior maxilla and splinted
with the zygomatic implants that are placed more poste-
riorly [1,7,13,16]. For patients with extensive bone loss
in the pre-maxilla and lateral bones, implant placement
in defect areas is compromised unless other bone sites
are considered. The use of long implants, which pass
through the p alate and is anchored to th e skull base, may
provide remote distal anchorage that was previously un-
Skull Base Implants
The use of conventional implants for local anchorage
is limited to the available maxillary bone. Unfortunately,
because of bone loss or maxillary resection, these an-
chorage sites are not always suitable for the placement of
conventional implants. Subsequent investigation into the
use of remote bone anchorage led to the development of
implants with a distal anchorage in the zygomatic bone
[9,12] and the scaphoid fossa of th e pterygoid bone [15].
Image-based planning and the use of surgical drill guides
or navigation techniques [5,15] can be helpful in select-
ing implantation sites and in drilling distal bone [6,
14,15]. By doing this, it is possible to consider more re-
L. Vrielinck et al. / Case Reports in Clinical Medicine 2 (2013) 405-410
Copyright © 2013 SciRes. OPEN ACCESS
mote bone sites lying 3 - 5 cm from the entry point in the
maxilla or the palate. An example of the remote bone
anchorage concept is the skull base implant (like the zy-
goma implant), which was developed for use in patients
with severe maxillary atrophy or challenging maxillary
defects, reconstruction of failed previous bone grafts, or
maxillectomy defects.
Four patients were treated with long implants with dis-
tant anchorage in the skull bone. They all presented with
extensive bone loss due to a failed bone graft, implant
placement, or maxillectomy defect. The majority of im-
plant procedures were rescue treatments following failed
standard implant or augmentation procedures in the max-
illa; while, one patient h ad a maxillectomy procedure for
a malignant tumour.
For implantation, the “zygomaticus fixture” (Nobel
Biocare, Göteborg, Sweden) was used, which is av ailab le
in different lengths, from 30 mm with increasing incre-
ments of 2.5 mm up to 52.5 mm. The head of the implant
has a built-in angulation of 45˚, which mimics the 45˚
inclination towards the occlusal plane in which the im-
plant is inserted (Figure 1). All patients were preopera-
tively evaluated with respect to jaw size, bone volume,
jaw relations, intermaxillary distance, occlusal relation,
and condition of the opposing dentition. A thorough
evaluation of the general health status was conducted to
ensure that the patient could withstand a 2 h operation
under general anaesthesia. Preoperative analysis of the
anatomical conditions and possible pathologies was
conducted with panoramic radiographs and a spiral CT
scan (Somatom Plus S®, Siemens, Erlangen, Germany).
Figure 1. The zygomati-
cus fixture from Nobel Bio-
The digital data from the CT scan were transferred to a
personal computer and a treatment plan was designed to
make optimal use of the remaining bone volumes by
simulation with long implants using Simplant® software
(Materialise, Leuven, Belgium).
A step by step account of the planning procedure is
described below. An implant, represented by a cylinder
with a central axis, was defined using two points named:
the entry and end points. The cylinder diameter corre-
sponded to the diameter of the selected implant (4.5 mm
at the entry and 4.0 mm at the end point for a zygoma
implant). Using the CT-derived surface model of the
maxilla, the surgeon indicated the entry and the desired
end points for the drills. The implant and surrounding
bone was then observed in three dimensions. After plan-
ning, the implant angulation was further adjusted and its
dimensions adapted to obtain the optimal position to en-
sure maximal bone anchorage distally.
2.1. Applied Anatomy
The skull base implant enters the bone midpalatally,
and then follows an intranasal trajectory in a dorso-cra-
nial direction beside the nasal septum. Subsequently, the
implant perforates the inferior wall of the sphenoid sinu s
or body of the sphenoid bone (Figure 2). Uttermost care
has to be taken to ensure proper positioning of the im-
plant. If the apical part of the implant is placed too lateral,
it could perforate the orbit. If the inclination of the im-
plant is placed too vertical, it could enter the ethmoidal
sinus. For an implant directed too horizontally, no bony
structures will be encountered and th e implant could end
up in the nasopharynx.
2.2. Drill Guide
Using stereolithography technology (Materialise,
Leuven, Belgium), the finalized treatment plan was then
used to fabricate the jaw model and a surgical drill guide
with bone or mucosal support (SurgiGuide®, Materialise,
Figure 2. Postoperative radiographic view of a long implant
with distal skull base anchorage.
L. Vrielinck et al. / Case Reports in Clinical Medicine 2 (2013) 405-410
Copyright © 2013 SciRes. OPEN ACCESS
Leuven, Belgium). The aim was to create an individual-
ized drill guide that is suited to the patient’s anatomy. A
CAD/CAM program used the shape of the bone and the
3D information of the planned drill paths to design the
drill guide, which is then produced by stereolithography
(Figure 3(a)). Its special design consists of a resin (USP
Class 6 approved) backbone with cylindrical openings
into which stainless steel tubes can be fitted (Figure
3(b)). The inner diameter of the steel tubes is 0.2 mm
greater than the diameter of the corresp onding drill. Each
cylinder’s position and direction corresponds exactly to
the position and direction of the planned implants. Drill-
ing into the bone is performed as a two-step procedure
using two drills of different diameters (2.9 mm and 3.5
mm). Consequently, two sets of 10 mm steel tubes are
provided (3.1 mm and 3.7 mm), 0.2 mm wider than the
diameter of the corresponding twist drill. Prior to surgery,
simulation of the intended operation is carried out on the
stereolithographic maxillary model using the surgical
drill guide. Since the designed drill guide can only be
used to drill the implant trajectories, theoretically the
implant must be placed freehand. In reality, it is very
difficult to find the distal entry point into the sphenoid
sinus or skull base when the distal entry point cannot be
Figure 3. (a) Surgical drill guide with mucosa sup-
port in place; (b) Steel tubes with different internal
diameters (3.1 and 3.7 mm) used for drilling the
implant trajector ies.
visualised directly; therefore a second guide was de-
signed with exactly the same supporting surface as the
drill guide, but with larger tubes for insertion of the im-
plant (Figure 4).
2.3. Surgical Protocol
All patients were treated under general anaesthesia
with nasal intubation. The surgical drill guide was fitted
in the jaw and fixated with four or five 20 mm osteosyn-
thesis screws (Leibinger, Freiburg, Germany). Following
installation of the steel tubes in the drill guide, drilling
was performed until the burr penetrated the basilar part
of the spheno id bone. Ho wever, care must be taken not to
drill deeper than originally planned. The surgical drill
guide was then removed before implants were placed and
replaced by the implant insertion guide. The tubes in the
guide were of sufficient width to allow passage of the
implant and implant insertion tool (Figure 4). After the
implant was placed at the correct depth, the implant in-
serting tool was detached and the implant inserting guide
was removed, leaving the implant in place. The implants
used in treating our patients were Branemark zygoma
fixtures, which varied in length from 30 to 52.5 mm. The
fixture head had to b e p os itioned accurately by ob serving
the screw that locked the fixture mount to the fixture.
The screw position duplicated the future abutment screw
position exactly. Finally, the fixture mounts were re-
moved and replaced by cover screws. Antibiotics (clin-
damycin, 900 mg/day) were prescribed for 10 days post-
operatively. To minimize postoperative pain, analgesics
(codeine phosphate and paracetamol) were prescribed for
all patients. In the majority of cases, the need for pain
medication was limited to one or two days. Patients were
instructed to carefully rinse their mouth with chlorhexi-
dine after each meal. After one to two weeks, a clinical
examination was conducted to evaluate the healing pro-
gress. After wound healing, the existing prosthesis of th e
patient was adapted or relined, avoiding contact between
the prosthesis and the coronal part of the implant. After a
healing period of 6 months, the implants were exposed
under local anaesthesia and healing abutments were placed
Figure 4. Implant insertion guide.
L. Vrielinck et al. / Case Reports in Clinical Medicine 2 (2013) 405-410
Copyright © 2013 SciRes. OPEN ACCESS
on the implants. Prosthetic rehabilitation was performed
as with regular platform implants. No special compo-
nents were needed. The prostheses connecting the skull
base and other implants were constructed with a passive
fit and all implants were joined together as soon as pos-
sible after they were exposed.
During the last fifteen years four patients have been
treated with long implants and skull base anchorage. An
overview of these patients is presented in Table 1 and
described below.
2.4. Case 1
The first patient was a 62-year-old female with an
atrophic upper jaw. Her first treatment occurred in 1995
and consisted of placing 4 regular implants in the maxil-
lary bone. After 2 years, all the implants failed. In 1999,
the patient underwent a secondary surgery containing
maxillary bone augmentation with iliac crest bone and
simultaneous placement of 4 regular implants, 2 zygoma
implants, and 2 tuberosity implants.
The tuberosity implants and left zygoma implant were
not osseointegrated and were removed after 6 months.
There was no good prosthetic solution for the upper jaw
for 3 implants; therefor e, at the end of 2000, the decision
was made to replace the left zygoma implants and place
2 pterygoid and one skull base implant (Figure 5). The
patient was followed for 12 years and the implants and
supra-structure remained stab le in the jaw.
2.5. Case 2
The second patient was a 69-year-old female with an
aggressive maxillary adenoid cystic carcinoma. She un-
derwent a right hemimaxillectomy operation in 2001
followed by post-operative radiotherapy. A year later, 7
implants were placed: 1 zygoma implant and 1 pterygoid
implant on the right side and 5 regular implants in the
remaining maxilla. In 2004, the right zygoma implant
and 2 regular implants were removed due to chronic in-
flammation. To obtain good support for the prosthesis,
one pterygoid and one skull base implant were placed
(Figures 6(a) and (b)). The implants remained stable and
functional for five years when the patient died from brain
2.6. Case 3
The third patient was a 61-year-old woman with ex-
tremely atrophic upper and lower jaws. The treatment
plan consisted of a sandwich osteotomy of the lower jaw
and a Lefort 1 osteotomy of the upper jaw with inter-
positional bone grafting. The operation took place in
1997. After 6 months, 5 implants in the lower jaw and 6
implants in the upper jaw were placed. After 2 years,
there was continuous failure of the upper jaw implants
and she gradually lost all these implants. To restore the
prosthetic retention again, 6 implants were placed: 2 zy-
goma implants, 2 pterygoid implants, and 2 paranasal
implants. At the end of 2001, the left paranasal implant
failed. There was no longer good prosthetic retention;
therefore, 2 skull base implants were placed. After 11
years of follow-up, the prosthesis and implants remain
stable and functional.
Figure 5. Postoperative OPG of patient 1.
Table 1. An overview of the case patients.
Case Age Sex Reason for treatment Problem Date of
treatment Implant
treatment Follow-up
time Condition at last
1 62 F
Failure of regular implants
and bone grafts
Bone defect in
premaxilla, atrophy
of lateral bones 26. 10. 20002 zygoma
2 pterygoid
1 skull base 12 years Implants present
and stable
2 69 F
Loss of regular and
zygoma implants after
hemimaxillectomy for
adenoid cystic carcinoma
Defect in
premaxilla, left
lateral bone defect 31. 01. 20054 standard
1 zygoma
1 skull base 5 years Implants present
and stable
3 61 F
Failure of regular implants
after interpositional bone
Bone defect in
premaxilla, atrophy
of lateral bones 2001 2 pterygoid
1 skull base 10 years Implants present
and stable
4 65 F
Failure of regular implants
after maxillary
Bone defect in
premaxilla, atrophy
of lateral bones 16. 05. 20022 pterygoid
2 skull base 11 years Implants present
and stable
L. Vrielinck et al. / Case Reports in Clinical Medicine 2 (2013) 405-410
Copyright © 2013 SciRes. OPEN ACCESS
Figure 6. (a) Postoperative PA of patient 2; (b)
Obturator to close maxilla defect.
2.7. Case 4
The fourth patient was a 65-year-old woman. The
maxillary augmentation procedure and placement of 6
implants were performed for the patient in another centre.
The patient lost 3 left implants due to in fection. She was
informed about the poor prognosis of the prosthesis due
to the unilaterally placed implants; however, she was
satisfied with the prosthetic solution she had. In 2002,
she lost another implant on the right side due to the un-
favourable forces of the prosthesis. At that time, a new
treatment plan was made with the placement of 4 stan-
dard implants, 2 pterygoid, and 1 skull base implant. The
implants and prosthesis were stable after 10 years of fol-
It is well known that the placement of long implants
with zygomatic or pterygoid anchorage is more complex
and difficult than conven tional oral implants. Man y max-
illofacial surgeons are not familiar with the anatomy of
the sphenoid bone and skull base region, which makes it
unlikely that these bone structures will be chosen as an-
chorage points for long implants. Implant placement in
this region demands excellent surgical skills, profound
anatomical knowledge, and good three dimensional
simulation skills using image-based implant planning
As a rule of thumb, two zygoma implants are com-
bined with three or four anterior standard implants (Fig-
ure 2). When a patient presents with anterior and poste-
rior bone atrophy, the current treatment plan involves
using the quad zygoma technique, which can be used as
long as enough anch orage is present in th e zygoma bone.
When combining zygoma and pterygoid implants, 0 - 2
standard implants may be added anteriorly [1,4,5,8,10,
11]. In cases with severe anterior bone loss and failed
anterior implants, there may not be a sufficient amount of
bone to provide anchorage for new implants. In such
cases, it is possible to obtain additional anchorage by
adding 1 or 2 skull base implants.
Placing skull base implants cannot be done without the
use of computer-assisted planning and guided surgery.
The time necessary to prepare the implant planning using
the Simplant® software depends on the user ’s experience.
Actual implant planning typically took between 30 min
and 1 h. Computer-assisted planning allows the surgeon
to use the maximum amount of sphenoid bone for im-
plant placement and also to identify and avoid adjacent
anatomical structures. This technique is precise enough
but the precision depends largely on the ability to posi-
tion the drill guide accurately on the underlying tissue
[10]. This technique is also highly dependent on the
user’s experience. In this aspect, more recent develop-
ments like navigation systems are important since this
allows for an intra-operative check of the drilling direc-
tion, which is not the case with a drill guide.
The skull base implant follows an intra-nasal trajec-
tory beside or through the nasal septum. Although the
implants may partially occlude the nasal passageway, no
complication has been recorded and none of the patients
complained of a nose obstruction. This may need further
attention if a patient has breathing problems before im-
plant placement. Intra-orally, the implant emerges in a
nearly mid-palatal position, allo wing for a fixed structure
like an overdenture. As a rule these implants are rigidly
splinted to the remaining other implants to achieve good
cross arch stabilisation. In most cases, a fixed removable
overdenture is used. This not only allows the chewing
function to be restored but also provides support for the
soft tissue of the face. It can also function as an obturator
for closing intra-oral defects.
The patients presented here are examples of extremely
complicated clinical cases with many previous recon-
struction procedures including: regular implants, bone
grafting, and zygomatic and pterygoid implants. Despite
these procedures, proper maxillary rehabilitation could
L. Vrielinck et al. / Case Reports in Clinical Medicine 2 (2013) 405-410
Copyright © 2013 SciRes. OPEN ACCESS
not be achieve d and patie nts searched for bett er treatment
options. In one of the patients, the tumour resection left
no room for a bone graft or implants. With the aid of the
skull base implant, this complex and challenging patient
was rehabilitated. The most significant and immediate
benefit of this approach is the ability to extend the pros-
thesis anchorage points into the mid-palatal area, thus
minimizing the can tilever forces on teeth and implants in
residual ridge tissue. The skull base implant supplements
this concept by creating effective retention in an ana-
tomical area that otherwise could be overlooked for im-
plant placement.
A skull base implant is a new concept of bone an-
chorage using long implants. It can be a solution for pa-
tients presenting with prosthetic and implant challenges
due to sequelae of a maxillectomy, failed reconstruction
combined with scaring and fibrosis due to previous
treatments, and a lack of bone in the maxilla. In most
cases, judicious use of the remaining bone (sometimes
distant to the maxilla) may be a solution for these pa-
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