Jure Urbančič1, Constance Gléron2, Gregorio Benites3, Martin Škrlec4,
Domen Vozel5
real-life time Consumption in image-guided
endonasal endoscopic Procedures
Dejanska poraba časa pri navigacijski kirurgiji nosu in obnosnih votlin
aBstraCt
KEY WORDS: navigation, FESS, image-guidance
BACKGROUNDS. Endoscopic endonasal surgery has evolved from the work of Messerklinger,
Draf and Wigand. Its unprecedented development has taken over vast depths of the nose,
paranasal sinuses, and skull base. The use of preoperative CT and MRI images allows
safer and faster access to complex structures. The study aims to provide adequate infor-
mation regarding the usage times and the possible correlation between image-guidan-
ce systems use and the duration of the surgery for specific procedures. METHODS. We
analysed the intraoperative data regarding the use of image-guidance systems, identi-
fied problems with its use and different influencing factors, and analysed the added value
of its use from the surgeons perspective. RESULTS. We confirmed the relation between
the complexity of the process and the prolongation of the surgery. Complex cases will
demand an increased number of image-guidance systems position verifications, which
will prolong the time of image-guidance systems handling during the procedure. To fur-
ther explain the data, we propose three timelines representing the three typical surgi-
cal scenarios. DISCUSSION. The time used for image guided systems and the absolute
difference in operating times at various endoscopic endonasal procedures implies that
the main reason for prolonged surgery is probably extensive surgical work and is not
always directly related to image guided systems use itself.
iZvleČek
KLJUČNE BESEDE: navigacija, FESS, usmerjanje s pomočjo slikovnih preiskav
IZHODIŠČA. Endoskopska kirurgija nosne votline se je razvila iz dela Messerklingerja,
Drafa in Wiganda. Njen razvoj je povezan tudi z razvojem kirurške tehnologije, kot je
1 Asist. Jure Urbančič, dr. med, Katedra za otorinolaringologijo, Medicinska fakulteta, Univerza v Ljubljani, Zaloška
cesta 2, 1000 Ljubljana, Univerza v Ljubljani, Vrazov trg 2, 1000 Ljubljana; Klinika za otorinolaringologijo in
cervikofacialno kirurgijo, Univerzitetni klinični center Ljubljana, Zaloška cesta 2, 1000 Ljubljana; jure.urbancic@kclj.si
2 Constance Gléron, štud. med., Klinika za otorinolaringologijo in cervikofacialno kirurgijo, Univerzitetni klinični center
Ljubljana, Zaloška cesta 2, 1000 Ljubljana; Université de Lausanne, Faculté de Biologie et de Médecine, Rue du Bugnon 21,
1005 Lausanne
3 Gregorio Benites, štud. med., Medicinska fakulteta, Univerza v Ljubljani, Vrazov trg 2, 1000 Ljubljana; Faculty of Medicine,
National University of Trujillo, Roma Avenue 338, Trujillo
4 Martin Škrlec, dr. med., Klinika za otorinolaringologijo in cervikofacialno kirurgijo, Univerzitetni klinični center Ljubljana,
Zaloška cesta 2, 1000 Ljubljana
5 Asist. dr. Domen Vozel, dr. med., Medicinska fakulteta, Univerza v Ljubljani, Vrazov trg 2, 1000 Ljubljana; Klinika za
otorinolaringologijo in cervikofacialno kirurgijo, Univerzitetni klinični center Ljubljana, Zaloška cesta 2, 1000 Ljubljana
383Med Razgl. 2022; 61 Suppl 2: 383–397
ORL 2022_Mr10_2.qxd  2.9.2022  13:00  Page 383
allowed continuous intraoperative axial,
coronal and sagittal views of the exact
location of the instrument tip (11–13).
Essentially two types of image-gui-
dance systems (IGS) are available, electro-
magnetic and optical. Both have proven
benefits and drawbacks (14–16). Smaller and
more compact systems with more straight-
forward or advanced software solutions
were gradually adapted to use in otorhino-
laryngology or neurosurgery (17). IGS-
-guided systems were first regarded as
a tool with the potential to help increase
postoperative results by reducing the sur-
geon’s workload. A new term for a surgeon’s
feeling of safety was introduced when it was
suddenly realised that IGS is helpful but
may not alter the operating strategy (18).
The new mindset was nevertheless alrea-
dy in place, and progress from open surgical
procedures to endoscopic − morbidity spa-
ring procedures was enormous (19, 20).
Massive development was also made in
improved endoscopes, new surgical instru-
ments and visualisation (21). Specifically,
the use of IGS may even shorten the sur-
gery time in ESS. Nevertheless, it demands
additional expertise and time to prepare to
use the devices and instruments (22).
Streamlined solutions involving IGS sho-
384 J. Urbančič, C. Gléron, G. Benites, M. Škrlec, D. Vozel real-life time Consumption in image-guided …
uporaba prej narejenih posnetkov CT ali MRI za orientacijo v operativnem polju. Namen
raziskave je prikaz vpliva obsega kirurškega postopka na navigacijo in njuna časovna ocena.
METODE. Analizirali smo med posegi zbrane podatke in primerjali dolžino posega za upo-
rabo navigacije. Poiskali smo morebitne težave pri nastavitvah in ustaljeni uporabi navi-
gacije, napovedne dejavnike za podaljšano dolžino posega in ocenili dobrobit uporabe
navigacije s stališča kirurga. REZULTATI. Potrdili smo povezavo zapletenosti posega z dol-
žino posega. Daljši in zapletenejši poseg sicer zahteva večkratno uporabo navigacije, a je
zapletenost posega vseeno boljši napovedni dejavnik za njegovo dolžino. Obenem pred-
lagamo tudi tri časovnice, ki ponazarjajo potek uporabe navigacije med samim posegom.
RAZPRAVA. Čas uporabe navigacije in razlike v absolutni dolžini posega pri različnih endo-
skopskih operacijah v nosu nakazuje, da je razlog za dolžino posega pravzaprav količina
čistega kirurškega dela in ne sama uporaba navigacijske tehnologije.
BaCkgroUnDs
Endoscopic sinus surgery (ESS) has evolved
from the work of pioneers like Messerklinger,
Draf and Wigand and has become a criti-
cal surgical strategy for a growing number
of indications (1–3). In the 80s, the need for
a radiologic definition of paranasal sinus
anatomy arose, and CT was ideal for the pur-
pose (4). Reports of severe intraoperative
complications were not rare, even when
experienced surgeons were equipped with
detailed anatomical knowledge and three-
-plane CT imaging (5, 6).
Some authors were even advocating
using a microscope instead of an endosco-
pe for reasons of obscured view and lack of
magnification in life-threatening emer-
gencies (7). But endoscopic surgery was far
from finished. New, bold ideas kept emer-
ging, like the radical endoscopic removal
of malignant disease (8). When anatomic
landmarks were missing, and the orienta-
tion in the labyrinth of the nose became
increasingly difficult, a new computer-
-aided surgery (CAS) model seemed a pro-
mising though costly advancement (9).
The basic concept was transferred from
neurosurgery. Navigational systems with
headframes were used to set the coordina-
tes for stereotactic surgery (10). CT images
ORL 2022_Mr10_2.qxd  2.9.2022  13:00  Page 384
wed the added benefit of lower time con-
sumption and better ergonomics, and a need
for additional training (23). The surgical
equipment’s availability, reliability, and
proper function have been given a pivotal
role in reducing preventable errors and
decreasing complications (24). Nevertheless,
some authors may still be reluctant to
identify the IGS as a critical component of
the endoscopic technique for the most
challenging procedures such as sinonasal
malignancies (25, 26).
Operating time has been identified as
a potential risk factor in skull base surge-
ry (27). The study’s main aim was to pro-
vide adequate information regarding the
usage times and the possible correlation
between IGS use and the duration of the
surgery for specific procedures. To our
knowledge, there is a lack of data regarding
the real-life impact of using the IGS in
a broad spectrum of endoscopic endonasal
procedures. Mainly, since the use of IGS
also influences changes in the surgeon’s
actions (28). We compared the effects
through different endonasal endoscopic
procedures, taking into consideration the
effectiveness of the surgery and identifying
specific problems regarding handling
during set-up or operational use.
MetHoDs
The study was designed as a retrospective
quality control study of surgical cases
where IGS was routinely used for a nose
and paranasal sinuses procedure in gene-
ral anaesthesia performed in a single ter-
tiary referral centre from 1st March 2013
to the 31st December 2016. Cases were stra-
tified into subgroups of malignant disea-
se, frontal disease, inverted papilloma (IP),
chronic rhinosinusitis with nasal polyps
(CRSwNP), group of guided biopsies, and
abscess drainage and isolated sphenoid
disease and cerebrospinal fluid (CSF) leak
repairs, including gliomas or meningo-
celes. Type of treatment, the involvement
of the skull base and time of surgery was
extracted from the institutional database.
A control group of patients with CRSwNP
was randomly selected from the same data-
base. According to hospital policy, all
patients had priorly signed an informed
consent to allow the recordings of their pro-
cedures for educational, research, and qua-
lity control use. The patient’s data was
anonymised immediately after synchro-
nising the documentation from the hospi-
tal information system, while surgical
appliances and surgeon’s notes were ano-
nymised after the procedure. Perceived
precision, orientation, surgical score and
surgical confidence were also routinely
measured (29).
The data was re-evaluated using the
timeline embedded in the recording of the
endoscopic procedure. Recordings were
done with the Karl Storz AIDA® video
system (Karl Storz AG, Tuttlingen, Germany)
in 720p25 quality, the Sony HD Recorder
(Sony Europe Limited, Weybridge, United
Kingdom) in 1080p25 quality or the Elgato
Capture HD60 (Corsair Components Inc.,
Freemont, USA) attached to a personal
computer in 1080p60 quality. Brainlab
Kolibri optical navigation with Ent 2.1.1
software (Brainlab AG, Munich, Germany)
and standard tip registration technique
with four points (lateral orbital rims, gla-
bella, and premaxillary area) was used.
We had excluded cases with missing
data (time profiles and questionnaires),
patients where other surgical factors (mal-
function of non-IGS related equipment,
use of non-standard techniques or proce-
dures, if a young surgeon was performing
under surveillance) or when anesthesio-
logical factors (procedure stopped for vital
reasons) may have influenced the length of
the procedure. The surgeon uploaded all the
patient data, planned the registration points,
applied the headband or navigational pole
for the head clamp, prepared the instru-
ments and concluded registration.
385Med Razgl. 2022; 61 Suppl 2:
ORL 2022_Mr10_2.qxd  2.9.2022  13:00  Page 385
Preoperative planning was performed
immediately after uploading the patient
data. It consisted of defining different points
or trajectories through the proposed surgi-
cal path. Precision was checked with a navi-
gational tooltip, first running over the external
nose and second by touching the inferior and
middle turbinate under endoscopic control.
The result was successful when the precision
was confirmed by touching anatomical points
on the IGS and observing the real-time
endoscopic picture. To acquire the correct
type of data, navigation was always used to
verify the position and not for continuously
navigating the approach (navigated drill or
similar instrument).
The intraoperative performance of the
IGS, the preoperative planning, registration,
calibration of various IGS instruments pro-
blems, systemic problems with the IGS, sur-
gical orientation, precision and confidence
regarding the use were collected via a sur-
gical questionnaire. A well-defined scale is
mandatory to show a significant percenta-
ge of surgical strategy changes and their
magnitude. The moment when a surgeon
confirms a catastrophic situation would
understandably present the most highly
scaled strategy change (table 1).
Data preparation was done using
Microsoft Excel 2016 and Microsoft Office
386 J. Urbančič, C. Gléron, G. Benites, M. Škrlec, D. Vozel real-life time Consumption in image-guided …
Timeline (Microsoft, Redmond, USA). All
statistical analysis was performed using
SPSS v. 20.0. (IBM, Armonk, USA). Since no
patient data was used after the initial iden-
tification of cases, no national ethics com-
mittee opinion was needed according to the
institutional ethics board opinion.
statistics
We calculated the mean time used for regi-
stration, mean time of the procedure and
mean time of intraoperative use. We com-
pared the values regarding specific proce-
dures and the involvement of the skull base
using the Mann-Whitney U test, Kruskal-
-Wallis test, and analysis of variance
(ANOVA). Statistical significance was assu-
med at p<0.05. For non-normally distribu-
ted data, weused the non-parametric test.
The homogeneity of variance was tested
with Levene’s test of equality. Groups were
compared with a univariate analysis of
variance, and the difference was determined
by one-way ANOVA using the Bonferroni
adjustment. We checked the linear rela-
tionship of elapsed time (mean time to the
end of registration vs mean duration of the
procedure and mean time of intraoperati-
ve use vs mean duration of the procedure).
We created a linear regression model inc-
luding selected variables. The probable cor-
table 1. Definition of categories in the surgeons’ questionnaire. IGS – image-guidance systems, VAS – visual
analogue scale.
Registration, calibration and orientation issues 0. None
1. Minor, not an issue
2. Minor, but issue on time and performance
3. Major issue, with limited usage of device
4. IGS usage impossible
Precision and orientation score 0. Unsatisfactory … 10 – Excellent
(self-assessed VAS)
Same procedure as without use of IGS 0. Not … 10 – Certainly, by all means
(self-assessed VAS)
Was the strategy changed during use of IGS VAS > 5 positive
(self-assessed VAS)
ORL 2022_Mr10_2.qxd  2.9.2022  13:00  Page 386
relation of the number and duration of
intraoperative image-guidance use with
the total surgical time was assessed. A mean
number of calibration attempts, boot time,
a mean number of intraoperative applica-
tions, mean precision of the IGS as per-
ceived by the surgeon, mean intraoperative
orientation score and mean response, and
whether the surgeon would perform the
same surgery without IGS were calculated.
Group means were compared by one-way
ANOVA using the same criteria for homo-
geneity of variance. Multiple comparisons
using Bonferroni adjustment were made to
identify statistically significant pairs. Scaled
answers were reflected, log10 values were
used in the ANOVA test.
resUlts
Out of 117 cases, 51 met the defined criteria
for the study. All were operated by one expe-
rienced surgeon. Detailed group characte-
ristics are presented in table 2.
Most of the procedures (74.5%) did not
involve the skull base. In 82.4% of the cases,
CT of the nose and paranasal sinuses was
used as a source of navigational data. The
extension of the procedures (CRSwNP with
IGS and without IGS) was the same
(p=0.056). Detailed times in stratified sub-
groups are presented in table 3, pairwise
comparison in table 4 and cumulative IGS
usage data in table 5.
The mean procedure time in malignant
disease is statistically different from all other
387Med Razgl. 2022; 61 Suppl 2:
table 2. Group characteristics. N  – number of patients, SD  – standard deviation, CRSwNP – chronic
rhinosinusitis with nasal polyps, CSF – cerebrospinal fluid, IGS – image-guidance systems.
Patient’s data n (%)
Sex
Female 22 (43.2)
Male 29 (56.9)
Age (years) 51.1 (0.1–81.5, SD 19.2) 
Procedure
Malignant disease 12 (23.5)
Frontal disease 13 (25.5)
Inverted papilloma 9 (17.6)
CRSwNP 5 (9.8)
Guided biopsies and abscess drainage 8 (15.7) 
CSF leak repairs (glioma, menigoceles) 4 (7.8)
Skull base procedures
Yes 13 (25.5)
No 38 (74.5)
Source of IGS data
CT of the nose and paranasal sinuses 42 (82.4)
CT and MR of the nose and paranasal sinuses 6 (11.8)
Other (CT of the head, orbit) 3 (6.0)
ORL 2022_Mr10_2.qxd  2.9.2022  13:00  Page 387
388 J. Urbančič, C. Gléron, G. Benites, M. Škrlec, D. Vozel real-life time Consumption in image-guided …
ta
bl
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3.
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ORL 2022_Mr10_2.qxd  2.9.2022  13:00  Page 388
389Med Razgl. 2022; 61 Suppl 2:
ta
bl
e 
4.
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pa
ris
on
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of
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ORL 2022_Mr10_2.qxd  2.9.2022  13:00  Page 389
procedures (p<0.001). The time taken for the
registration of the IGS is linearly correlated
to the duration of the surgery in malignant
disease (r2=0.51, p=0.009) as well as IP
(r2=0.50, p=0.04) (see also table 5). In regres-
sion analysis, we have also found a linear cor-
relation between the number of separate IGS
uses in malignant diseases (r2=0.60, p=0.005)
and the amount of total intraoperative IGS
usage and total duration of the procedures
(malignant diseases, r2=0.73, p<0.001 and IP,
r2=0.73, p=0.03). Scaled answers for the pre-
cision of the IGS, the intraoperative orienta-
tion score, and the estimate of the probability
of the same procedure without the IGS are
presented in figures 1–3. The percentage of
strategy changes is illustrated in figure 4.
390 J. Urbančič, C. Gléron, G. Benites, M. Škrlec, D. Vozel real-life time Consumption in image-guided …
table 5. Cumulative data (N=51) about the usage of the image-guided systems (IGS). N – number of patients,
SD – standard deviation, CRSwNP – chronic rhinosinusitis with nasal polyps, CSF – cerebrospinal fluid.
Cumulative data n (or otherwise indicated)
Boot time (s) 128 (SD 8.9)
Loading problems 0 (0.0%)
Navigational planning
No planning 24 (47.1%)
Up to two points 13 (25.5%)
Multiple points 10 (19.6%)
Complex planning (points & trajectories) 4 (7.8%)
Registration points 
Minor problems (not an issue of time and performance) 1 (2.0%)
No problems 50 (98.0%)
Number of registration attempts 1.14 (SD 0.5)
Navigational precision estimate 
Green 8 (15.7%)
Yellow 43 (84.3%)
Red 0 (0.0%)
Orientation issues during procedure
None 47 (92.2%)
Minor, not an issue of time and performance 1 (2.0%)
Minor issue on time and performance 2 (3.9%)
Major issue with limited usage of device 1 (2.0%)
Number of intraoperative uses (mean for group − SD) 6.1 (SD 3.8)
Malignant disease 10 (SD 4.2)
Frontal disease 8.7 (SD 2.2)
CSF leak repairs (glioma, menigoceles) 3.5 (SD 1.3)
CRSwNP 3.4 (SD 1.3)
Inverted papilloma 3.3 (SD 1.6)
Guided biopsies and abscess drainage 3 (SD 0.9)
ORL 2022_Mr10_2.qxd  2.9.2022  13:00  Page 390
391Med Razgl. 2022; 61 Suppl 2:
0
1
2
3
5
6
7
4
8
10
9
V
A
S
Glioma,
meningocele,
CSF leak repair
Malignant
disease
Inverted
papilloma
Biopsies &
abscess &
isolated sphenoid
CRSwNP Isolated frontal
disease & osteomas
of the frontal sinus
9 25.
9 10.
9 10. 8 70.
8 60.
8 00.
Figure 1. The mean precision of the image-guided systems (IGS) as perceived by the surgeon (visual ana-
logue scale (VAS) of 0 to 10 with standard deviation (SD)). Malignant vs isolated frontal disease and osteo-
mas of the frontal sinus p=0.01, inverted papilloma vs isolated frontal disease and osteomas of the frontal
sinus p=0.02, analysis of variance (ANOVA) (F(5,45)=3.885, p=0.005). VAS – visual analogue scale, CSF –
cerebrospinal fluid, CRSwNP – chronic rhinosinusitis with nasal polyps.
9
7
5
3
1
0
2
6
4
8
10
V
A
S
Glioma,
meningocele,
CSF leak repair
Inverted
papilloma
CRSwNP Malignant
disease
Isolated frontal
disease & osteomas
of the frontal sinus
Biopsies &
abscess &
isolated sphenoid
9 70.
9 10. 9 00.
8 80.
8 10.
8 00.
Figure 2. The mean intraoperative orientation score as perceived by the surgeon (visual analogue scale (VAS)
of 0 to 10 with standard deviation (SD)). Glioma, menigocele, cerebrospinal fluid (CSF) leak repair vs. biop-
sies and abscess and isolated sphenoid p=0.04, analysis of variance (ANOVA) (F(5.45)=3.487, p=0.01). VAS –
visual analogue scale, CSF – cerebrospinal fluid, CRSwNP – chronic rhinosinusitis with nasal polyps.
ORL 2022_Mr10_2.qxd  2.9.2022  13:00  Page 391
392 J. Urbančič, C. Gléron, G. Benites, M. Škrlec, D. Vozel real-life time Consumption in image-guided …
9
7
5
3
1
0
2
6
4
8
10
V
A
S
Glioma,
meningocele,
CSF leak repair
Inverted
papilloma
CRSwNP Malignant
disease
Isolated frontal
disease & osteomas
of the frontal sinus
Biopsies &
abscess &
isolated sphenoid
9 70. 9 60.
9 10.
8 70.
7 00.
6 50.
Figure 3. Scaled answer whether the surgeon would perform same surgery without intraoperative IGS (visual
analogue scale (VAS) 0 to 10 with standard deviation (SD); 0 – no, 10 – yes, certainly). Isolated frontal disea-
se & osteomas of the frontal sinus vs. malignant disease p=0.02, isolated frontal disease & osteomas of
the frontal sinus vs. CRSwNP p=0.001, isolated frontal disease & osteomas of the frontal sinus vs. glio-
ma, meningocele, cerebrospinal (CSF) leak repair p=0.001, isolated frontal disease and osteomas of the
frontal sinus vs. inverted papilloma p=0.002, analysis of variance (ANOVA) (F(5,45)=7.380, p<0.000). VAS –
visual analogue scale, CSF – cerebrospinal fluid, CRSwNP – chronic rhinosinusitis with nasal polyps.
5030100 20 40
Glioma, meningocele,
CSF leak repair
Inverted papilloma
CRSwNP
Malignant disease
Isolated frontal disease &
osteomas of the frontal sinus
Biopsies & abscess &
isolated sphenoid
% of intraoperative strategy changes
0
0
12.5
25
33.3
38.5
Figure 4. The percentage of strategy changes with IGS use. CRSwNP – chronic rhinosinusitis with nasal
polyps, CSF – cerebrospinal fluid.
ORL 2022_Mr10_2.qxd  2.9.2022  13:00  Page 392
DisCUssion
The anatomic complexity that requires the
surgeon to use all knowledge, spatial orien-
tation, and surgical intuition to solve the
problem emphasises the importance of the
IGS. Even more so when surgeons deal with
increasingly difficult procedures involving
the frontal sinus, CSF leak repair, or onco-
logic procedures (15).
Observing the meantime of registration
shows the understandable tendency to take
longer to register when performing a more
complicated procedure. In linear regression,
for every minute of increase in registration
time, the duration of surgery increases by
18.1 minutes in malignant disease and 5.3
minutes in patients with IP. But not all of
the groups show a statistically significant
difference in the pairwise comparison of
mean values. Empowered with the analy-
sis results, three different groups can be elu-
ded, one with malignant pathology being
the most time-consuming (duration of the
procedure and IGS involvement), follo-
wing the complex frontal sinus procedures,
CSF leak repair, and IP. A correlation bet-
ween the time of registration and the dura-
tion of the surgery was found in malignant
cases and inverted papilloma. It can be
explained by the similarities in endoscopic
approach, instrumentation, and surgical
thinking (30, 31).
Registration time and total IGS usage
were quite distinctively lower for all other
procedures, including those requiring com-
parably long operating times (CSF leak
repair, IP, frontal disease). Frontal sinus sur-
gery is also the pathology where authors
393Med Razgl. 2022; 61 Suppl 2:
Figure 5. Proposed timeline scenarios for inverted papilloma (IP), malignant disease and chronic rhino-
sinusitis with nasal polyps (CRSwNP). OP – operative, IGS – image-guided systems.
ORL 2022_Mr10_2.qxd  2.9.2022  13:00  Page 393
394 J. Urbančič, C. Gléron, G. Benites, M. Škrlec, D. Vozel real-life time Consumption in image-guided …
Figure 6. The relationship of parameters affecting the time of procedure for malignant disease. IGS – image
guided systems.
Figure 7. The relationship of parameters affecting the time of procedure for inverted papilloma. IGS – image-
guided systems.
ORL 2022_Mr10_2.qxd  2.9.2022  13:00  Page 394
were most inclined to trust the IGS during
surgery. Reasonable conduct of the endo-
scopic procedure requires a degree of fami-
liarity with the anatomy and pathology of
the patient. The surgeon usually does not
blindly follow the advice of the IGS but uses
the device as an additional confirmation of
known or unknown (ad-hoc) anatomical
landmarks or simply as a validation tool
(32, 33). High rates of perceived precision
and high orientation scores during the use
of IGS are consistent with other published
research data (9, 15, 17, 22, 32, 34). High
dependence on IGS in virtually blinded pro-
cedures without orientation points is also
expected (15, 35, 36).
Other authors have shown that the
intraoperative time reduction in conven-
tional functional endoscopic surgery (FESS)
was about ten minutes per case (22). We
haven’t found a significant difference when
comparing the duration and the sheer
extent of the surgery (CRSwNP). But in
more difficult cases, we have found that the
time consumption at registration, and the
total duration of surgery is higher (table 3).
We have shown that every single use of
the IGS should prolong the surgery time in
malignant cases by 32.5 minutes (mean
number of uses 10). With every minute of
IGS use, the intraoperative time increases
by 14.93 minutes (malignant diseases, mean
time of use of 11.8 minutes) or 7.6 minu-
tes (inverted papilloma, mean time of use
of 3.1 minutes).
To explain the data further, we propo-
se a timeline representing the three typical
surgical scenarios (figure 5). The time bet-
ween pins is defined as IGS use and pure-
ly surgical work. The relationship between
both may not be the same in all the proce-
dures. The first scenario reflects the IGS
usage in IP, the second in malignant disea-
se, and the third in CRSwNP. The robustness
of proposed scenarios also relies on identi-
fying any aberrantly long usage of IGS. They
were specially produced by factors not
separately identified upfront. The need to
correct the optical pathway for IGS or even
for recalibration arises when accuracy falls
below acceptable. The added real-time con-
tributes to the IGS use and the surgeon’s
response to the new information.
Prolongation of the surgery may well
be an attribute of a complicated surgical
procedure, added difficult anatomy, and
raw extension of the disease. The surgical
work between individual IGS verifications
may be shorter in less complex situations
(figures 6 and 7), however, the most deman-
ding endoscopic surgery without IGS may
not be a viable option anymore.
Complex cases will demand an increa-
sed number of IGS position verifications,
which will prolong IGS handling time
during the procedure. Comparing the
time used for IGS and the absolute dif-
ference in operating times at various
endoscopic endonasal procedures implies
that the main reason for prolonged sur-
gery is probably extensive surgical work
and is not always directly related to IGS
use itself.
395Med Razgl. 2022; 61 Suppl 2:
ORL 2022_Mr10_2.qxd  2.9.2022  13:00  Page 395
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