Image Guided Endoscopic Sinus Surgery: First Experience from Kashmir Valley

Abstract

Image guidance is best suited to paranasal sinus surgeries as these demand a high degree of anatomical precision because of close proximity to orbit and cranial cavity which at times is challenging in patients with frequent anatomical variations. This study is aimed to describe our first experience of using image guided endoscopic sinus surgery in Kashmir valley in terms of real time correlation between the operative field and the preoperative imaging; to evaluate its utility in disease clearance and to evaluate patient reported outcome measures using (pre and post-op) VAS, SNOT-22, Lund Mackey endoscopic and radiological scores. This prospective observational study was conducted from September 2016 to August 2018. Patients with the specific inclusion and exclusion criteria were operated using image guidance system. Pre and post operative SNOT-22, VAS, Lund Mackey endoscopic and radiological scoring were compared. Operative time, Instrument accuracy and complications were noted. Out of twenty cases enrolled in this study majority (14) patients (70%) were cases of uncomplicated chronic rhinosinusitis with nasal polyposis. Mean number of sinuses operated were 7.8 ± 2.14. Set up time for installing navigation system in first 10 cases was on an average 17 ± 1.67 min and in second 10 cases it was 12 ± 1.42 min. Mean operative time recorded was 112 ± 17.32 min. Accuracy of our system was 1.25 ± 0.73 mm (0.50–1.80) and average blood loss was 100 ± 23.54 ml. There was statistically significant reduction in postoperative VAS score, SNOT-22 score, Lund Mackey endoscopic and radiological scoring. Revision FESS was done in 12 cases and most common intraoperative absent nasal landmark was middle turbinate in these cases. No orbital or intracranial complication was seen. Minor complications were seen. Image guided surgery is a valuable tool worth use in difficult and revision cases. It makes the surgeon comfortable and saves patient from any major complication.

Introduction

Image guided surgery (IGS) or computer assisted surgery establishes a real time correlation between the operative field and preoperative imaging [1]. Unlike GPS system in a car, Navigation tools don’t tell surgeons where they can go; rather, it gives a very precise knowledge where they are. Image guided systems use computerized tracking devices to monitor the position of endoscopic instruments relative to the patient’s anatomical landmarks. This identification is called as Navigation or Localization. The location of these instruments is depicted on a 3D video display of the preoperative computed tomography (CT) in axial, coronal and sagittal frames simultaneously (triplanar) [2]. Preoperative CT images entered into a computer are linked to the operative field by a variety of methods such as an articulated mechanical arm, an electromagnetic probe, an infrared optical probe, or sonic probe. Points on a three dimensional computer model of the patient reconstructed from the preoperative CT scan are matched with identical points of a patient’s position on the operating table. These points are represented by x–y–z coordinate. The display of the images incorporates a marker and that identifies the surgical location. So the computer system acts as a navigator providing localization. Imaging assists the surgeon in navigating through diseased and/or surgically revised complex anatomy [3].

Navigation accuracy is contingent upon the IGS registration process that establishes the correlation between specific landmarks and stored imaging data. Several registration techniques have been proposed including the use of external fiducial markers, anatomical landmarks or contour- based registration. Surface registration that utilizes unique facial contours reduces the preparation time of conventional registration and is clinically convenient. Navigation system has gone from being a curious novelty to a near necessity. It has become an integral part of the armamentarium for performing endoscopic sinus surgery and beyond. It acts as a road map in tracking various structures during surgery thus reducing surgical time and apprehension of the surgeon in dealing with critical areas. Surgery in the paranasal sinuses (PNS) demands a high degree of anatomical precision and is well suited for image guidance because of restricted 2D view, anatomical variations of the sinuses and proximity to orbit and cranial cavity [4]. It is generally agreed that IGS can effectively orient the surgeon to the anatomy of the operating field for FESS procedures and provide additional support or validation for challenging surgeries with extensive mucosal disease, altered anatomy, a hemorrhagic endoscopic field, revision surgery, and or sinonasal neoplasm’s. The American Academy of Otolaryngology—Head and Neck Surgery has adopted by consensus the following set of classical indications for image guided surgery (IGS) that include: revision sinus surgery; extensive nasal polyposis; skull base defects; diseases abutting the cranial base, orbit, optic nerve or carotid artery; distorted anatomy of development, postoperative or traumatic origin; pathology involving posterior ethmoid, frontal or sphenoid sinus [5].

This study which is the first from our place is aimed to describe our first experience of using image guided endoscopic sinus surgery in Kashmir valley in terms of operative time, accuracy of instrument, complication rate and post operative reduction in VAS/SNOT-22/Lund Mackey endoscopic and radiological scores.

Materials and methods

This prospective study was conducted in the postgraduate Department of ENT & Head and Neck Surgery of Government Medical College, Srinagar over a period of 2 years from September 2016 to August 2018. Patients with the following inclusion and exclusion criteria were enrolled in the study;

Inclusion Criteria

• Patients of chronic rhinosinusitis with recurrent nasal polyposis.

• Patients of chronic rhinosinusitis with bilateral pan-polyposis (primary).

• Patients with complicated acute or chronic rhinosinusitis.

• Patients with CSF rhinorrhoea.

Exclusion Criteria

• Patients aged < 10 years or > 70 years of age.

• Patients with malignant sinonasal disease.

• Patients with medical co-morbidities rendering them unfit for general anesthesia.

Patients fulfilling the above criteria were subjected to detailed history including recording of Sinonasal Outcome Test (SNOT-22) and Visual Analogue Scale (VAS) score (Table 1). Preoperative diagnostic nasal endoscopy (DNE) was done in all cases and findings were scored by Lund and Mackey Endoscopic Scoring System.

Table 1.

VAS symptom score calculating table

Symptom (score by visual analogue method)	Score/points given	Baseline	Post-operative (3 months)	Post-operative (6 months)
Facial pain	(1–10)
Headache	(1–10)
Nasal blockage	(1–10)
Nasal discharge	(1–10)
Olfactory disturbance	(1–10)
Overall discomfort	(1–10)

0: symptom not present, 0–10: degree of symptom severity with 10 indicating greatest severity

Noncontrast computed tomography of paranasal sinuses were done in selected patient as per Navigation Protocol.

The following steps were used in image guided surgery:

• Image guided surgery begins with obtaining a CT scan of PNS.

  The CT scan acquisition protocol is based on predetermined Navigation protocol which consists of a helical, 1 mm—thickness axial CT scan, 512 × 512 image matrix and 0° gantry tilt done within 2 weeks of surgery. Contiguous scans were done without fiducial land marking.

  The scans were planned from horizontal portion of mandible to the superior aspect of frontal sinuses including ears, maxillary teeth with tip of the nose as the anterior most landmark. This allows registration of the imaging to the patient’s anatomy in the operating room.

• Loading of CT.

  The imaging data so taken was transferred via CD-ROM to the operating room, where it was loaded into the workstation on the day of surgery. The images were brought up on the image guided surgery system prior to surgery and checked for image quality and accuracy. The computer software restructures the computed tomography images and displays them on the screen in different planes (axial, coronal and sagittal). A three dimensional anatomy is thus built.

• Equipment utilized

  The equipment utilized was Stealth station S7 system.

  The application software reformats patient specific CT and displays them. The optical tracker utilizes laser to track the position of optical markers. Electromagnetic (AXEIM) system instruments designed for use contain embedded sensing coils.

  Other equipment used for navigation were:

  • Head tracker, straight and curved suction, ostium seeker.
  • Passive planer blunt registration probe.
  • 2.7/4 mm rigid 0° endoscope; 4 mm 45/70° endoscope.
  • Standard FESS instruments.
  • 4 mm medtronic microdebrider.
  • Three chip camera.
  • Storz light source.
  • HD monitor with recording facilities.

• The process of registration and navigation (Fig. 1).

• Camera tracking: head tracker with divot and light reflecting Glions is strapped on the head.

  Both head tracker and registration probe are brought in the vicinity line of the Infrared cameras mounted on the work station. A green or yellow signal on the screen confirms the presence of instruments within the optical field.

• Registration of instruments Specific instruments are registered by placing the tip of instrument in the divot with the attached glions towards the camera.

• Registration of patients reference points The passive probe is touched to the patients nose for the first point, the mid of the forehead (2 cm above the Nasion) for second point and to 3 cm left on the patients head for third point.

• Tracking A pattern is drawn with the registration probe corresponding to surface markings of patients paranasal sinuses (PNS) starting from tip of the nose, covering the complete nose i.e. nasal bones, left and right eyebrows and rest of the forehead region making continuous contact between probe and patients skin (called Dragging). Green and yellow spheres/circles illustrate the regions within which the localization error deviates 1 mm or less (green) and 2 mm or less (yellow). Red spheres illustrate failed tracking.

• Checking accuracy Once the registration is complete and the instruments are calibrated by the system, accuracy is verified by testing various known landmarks on the patients face and in the nares. The coordinates are stored and used throughout the procedure to monitor any changes in the accuracy of the device.

• Above steps done correctly, the system becomes ready for navigation.

• Intraoperative navigation.

  Whenever the surgeon selects a point from the patients anatomy using the tip of one of the optical probes [for example. Maxillary sinus ostium (Fig. 2) or Sphenoid sinus (Fig. 3)], the computer uses the saved data to identify the corresponding point on the computed tomography images. The point is then displayed on the monitor within all the different images planes (axial, coronal, sagittal).

  The surgeon then knows exactly where the tip of the probe is located in the patient’s anatomy and can thus perform safe surgery. It is important to understand that only preoperative scanning provides the computed tomography data for the operation. This means that tissue changes occurring during surgery do not show on the screen.

  Lund Mackay CT scoring was done 2 weeks before surgery (baseline) and at 6 months post operatively. Details of the previous surgery/number and absence of landmarks noted Details about the set up time for installing navigation system, mean no of sinuses operated, blood loss, operative time and accuracy of navigation along with complications were recorded.

  All patients were followed for 6 months in three follow ups:

  • At first follow up (1st month): Nasal endoscopy done.
  • At second follow up (3rd month): SNOT 22, VAS, 2nd look endoscopy with recording of Lund and Mackey Endoscopic Scoring.
  • At third follow up (6th months): All above plus NCCT Nose and PNS and recording of Lund and Mackey endoscopic and radiological Scores.

Fig. 1.

Different steps of set up of IGS. (1) Navigation system optical tracking used: Stealth Station S7. (2) head tracker with divot and light reflecting glions attached. (3) Registration of patients reference points. (4) Tracking

Fig. 2.

Registration probe in maxillary sinus ostium. Computer uses saved data to identify corresponding point on CT images. The point is then displayed on triplanar images

Fig. 3.

Registration probe in sphenoid sinus. Computer uses saved data to identify corresponding point on CT images. The point is then displayed on triplanar images

Statistical Method

The recorded data was compiled and entered in a spreadsheet (Microsoft excel) and then exported to data editor of SPSS version 20.0 (SPSS Inc, Chicago, Illinois, USA). Continuous variables were expressed as mean ± SD and categorical variables were summarized as frequencies and percentage. Graphically the data was presented by bar and pie diagrams. Paired t test was employed for comparing various parameters before and after surgical intervention. A value of less than 0.05 was considered statistically significant. All P values were two tailed.

Observations and Results

Twenty patients were enrolled within study as per inclusions criteria. Maximum number of 6 patients (30%) were in the age group 40–49 followed by 4 patients (20%) in the age group of 10–19. Three patients each (15%) were in the age groups of 30–39 and 50–59. Youngest patient in the study was aged 10 years and eldest patient was aged 69 years. The age distribution ranged from 10 to 69 years with mean age as 38.1 years. Total number of male patients were 11 (55%) and total number of female patients were 9 (45%).

In this study 14 patients (70%) were cases of uncomplicated chronic rhinosinusitis (CRS) with nasal polyposis out of which 12 patients were revision cases and 2 were fresh cases with panpolyposis. 4 patients (20%) were cases of preseptal orbital cellulitis (complicated Rhinosinusitis) out of which 3 had acute Rhinosinusitis (ARS) and 1 had CRS with polyposis. 1 patient was a case of CRS with potts puffy tumor and another 1 patient (5%) was a case of CSF Rhinorrheaeoa. Total number of CRS patients were 16 (Table 2).

Table 2.

Indications of IGS

S. no.	Indication	No. of patients	Percentage
1	CRS with nasal polyposis
	Revision	12	70
	Fresh	2
2	Complicated rhinosinusitis (pre-septal orbital cellulitis)	4	20
	Associated with ARS	3
	CRS with polyposis	1
3	CRS with potts puffy tumour	1	5
4	CSF rhinorrhoea	1	5

Preoperative and post operative radiological scoring at 6 months by Lund and Mackey (LM) was compared. It showed marked improvement in patients with CRS (n = 16) and ARS (n = 3). Total (mean) preoperative LM score in CRS was 334 (20.87 ± 5.41) which reduced to 44 (2.75 ± 2.21). P value was < 0.001 which is statistically significant. Total (mean) preoperative LM score in ARS group (n = 3) was 23 (8.3 + 0.58) which reduced to 1 (0.33 ± 0.57). P value was < 0.005 which is statistically significant. There was no change in preoperative and postoperative radiological scoring in the patient who presented with CSF rhinorrhoea as there was no paranasal sinus involvement.

Preoperative and postoperative Lund and Mackey endoscopic scoring of patients with CRS (n = 16) showed marked improvement. Total Lund and Mackey endoscopic score preoperatively was 150 (mean 9.37 ± 2.25), post operative Lund and Mackey endoscopic score after 3 and 6 months of follow up was 22 (mean 1.38 ± 0.81) and 9 (mean 0.56 ± 0.51) respectively. P value at postoperative 3 and 6 months were statistically significant with P value of < 0.001. In the ARS group (n = 3) post operative endoscopic score dropped from 12 to 0 at both 3 and 6 months. In CSF rhinorrhoea group no post operative leak was seen at 3 and 6 months and endoscopic score dropped to zero from initial score of 2.

In this study preoperative total SNOT-22 scoring of patients with CRS (n = 16) was 748 (mean 46.75 ± 9.40). Post operative total SNOT-22 score at an interval of 3 months and 6 months was recorded to be 91 (mean 5.69 ± 1.58) and 45 (mean 2.81 ± 0.91) respectively. P value at 3 and 6 months of follow up were < 0.001 which are statistically significant.

Preoperative and postoperative visual analogue score VAS was compared in all patients. Total preoperative VAS scores of all patients (n = 20) was 507 (mean 25.35 ± 10.16) and total VAS score after 3 months and 6 months follow up was 73 (mean 3.65 ± 1.57) and 62 (mean 3.15 ± 1.69) respectively. At 6 months of follow up there was 85% reduction in VAS symptom score. P value at 3 and 6 months follow up were < 0.001 which are statistically significant (Table 3).

Table 3.

Pre and post operative scoring

	Pre-op	Post-op (3 months)	Post-op (6 months)
Lund and Mackey radiological score (mean)
CRS (16)	334; 20.87 + 5.41	X	44; 2.75 + 2.21 (P value < 0.001)
ARS (3)	23; 8.3 + 0.58	X	1; 0.33 + 0.57 (P value < 0.005)
CSF rhinorrhea (1)	0	x	0
Lund and Mackey endoscopic scoring system
CRS (16)	150; 9.37 + 2.25	22; 1.38 + 0.81 (P value < 0.001)	9; 0.56 + 0.51 (P value < 0.001)
ARS (3)	12	0	0
CSF rhinorrhea (1)	2	0	0
SNOT22
CRS (16)	748; 46.75 + 9.40	91; 5.69 + 1.58 (P value < 0.001)	45; 2.81 + 0.91 (P value < 0.001)
ARS (3)	X	X	X
CSF rhinorrhea (1)	x	x	x
VAS
CRS (16)  ARS (3)  CSF rhinorrhea (1)	507; 25.35 + 10.16	73; 3.65 + 1.57 (P value < 0.001)	62; 3.15 + 1.69 (P value < 0.001)

Post-op CT scan was done at 6 month follow up only

In this study in 12 patients (60%) of revision FESS, inferior turbinate was absent in 1 patient (8.33%). Middle turbinate was absent in 10 patients (83.33%). Uncinate process was absent in 12 patients (100%) and bulla ethmoidalis was absent in 10 patients (83.33%). Among the revision cases 6 patients (50%) were operated once, 5 (41.66%) were operated twice and 1 patient (8.33%) was operated thrice (Table 4).

Table 4.

Intraoperative findings, No of previous surgeries done in revision cases and Follow up duration

S. no.	Absent landmark	No. of patients	Percentage
Intraoperative findings (n = 12. 60% revision cases)
1	Inferior turbinate	1	8.33
2	Middle turbinate	10	83.33
3	Uncinate process	12	100
4	Bulla ethmoidalis	10	83.33

No.	No. of patients	Percentage
Previous no of surgery
1	6	50
2	5	41.66
3	1	8.33

Follow up was done in all cases for a minimum of 6 months while 5 patients enrolled in the beginning of study were followed for 18 months, 10 patients followed for 12 months. 15 patients followed up for 9 month.

Mean number of sinuses operated were 7.8 ± 2.14 (range 1–10). Set up time for installing navigation system in first 10 cases was on an average 17 ± 1.67 min and in second 10 cases it was 12 ± 1.42 min. Mean operative time was 112 ± 17.32 min. Accuracy of our system was 1.25 ± 0.73 mm (0.50–1.80) and average blood loss noted in our study was 100 ± 23.54 ml (100–200 ml) (Table 5).

Table 5.

Characteristic findings using image guided system

Parameter	Mean ± SD	Range
Sinuses operated on (n)	7.8 ± 2.14
Set up time	17 ± 1.67 min in first 10 cases	15–20 min
	12 ± 1.42 min in last 10 cases	10–15 min
Operative time (min)	112 ± 17.32	40–150
Accuracy at surgery (mm)	1.25 ± 0.73	0.50–1.80
Blood loss (ml)	100 ± 23.54	100–200

No major complication like orbital/intracranial/major hemorrhage was seen in any of the 20 patients under study. Minor complications like minor bleeding (< 200 ml) was seen in 3 patients (15%). 2 patients (10%) had postoperative Periorbital echymosis (mild), 2 patients (10%) had postoperative nasal synechiae, 1 patient (5%) operated for CRS with potts puffy tumour developed postoperative lateralization of middle turbinate which was subsequently resected under local anesthesia (Table 6).

Table 6.

Complications

	No. of patients	Percentage
Major complications
Orbital	0	0
Intracranial	0	0
Major hemorrhage	0	0
Minor complications
Minor bleeding (< 200 ml)	3	15
Periorbital echymosis (mild)	2	10
Infection	0	0
Facial pain	0	0
Stenosis of nasolacrimal duct	0	0
Synechiae formation	2	10
Lateralization of middle turbinate	1	5

In this study advantages of IGS noted include localization of operating instruments in relation to pathology/vital structures and saggital reconstruction with three dimensional imaging capacity which increases the safety of the patient, improves surgeon reassurance, reduces the chances of major intracranial or intraorbital complications especially in revision cases with distorted nasal anatomy and absence of crucial nasal landmarks. Image guided ESS also proved beneficial as a teaching tool for residents/paramedics. In this study disadvantages of IGS noted include increase in the duration of operative time and accuracy errors of 1–1.5 mm that are sometimes critical for accurate surgical navigation (Table 6).

Discussion

Functional Endoscopic Sinus Surgery (FESS) is the most popular method for treating medically refractory and revision sinonasal disease. However, there are some pitfalls with this technique that can result at times in serious complications especially when operating in revision cases with or without loss of landmarks. Under the assistance of navigation system, surgeon can overcome such problems. This study was conducted to share our first experience of using image guided system.

Maximum number of 6 patients (30%) were in the age group of 40–49 followed by 4 patients (20%) in the age group of 10–19. Youngest patient in our study was aged 10 while the oldest was aged 69 years. Mean age recorded was 38.1 years. A study by Eliashar et al. [1] on use of Image Guidance recorded the mean age of patients as 46 years and patients ranged in age between 21 and 24 years while another study by Dolati et al. [6] on use of Image Guidance in skull base tumors recorded a mean age of 57.8 years in their patients.

In this study on 20 patients, 14 patients (70%) were cases of uncomplicated chronic rhinosinusitis (CRS) with nasal polyposis out of which 12 (86%) were revision cases. 4 patients (20%) were cases of preseptal orbital cellulitis (complicated rhinosinusitis), 1 patient (5%) was a case of CRS with potts puffy tumor and another 1 patient (5%) was a case of CSF Rhinorrhoea. Rai et al. [5] in 2013 in their study titled “Navigation in endoscopic sinus surgery: the first Indian experience” listed indications for performing image guided sinus surgery as per American association of Otolaryngology. All the indications in our study were in accordance with the indications of this study. Masterson et al. [7] In their study of 132 patients who underwent 147 procedures using image guidance surgery over the 8 year period from 2001 to 2009 found the indications for surgery ranging from severe nasal polyposis and chronic rhinosinusitis to malignant tumors in the paranasal sinuses and skull base region. In contrast to our study a higher percent (37.04%) of patients with preseptal cellulitis were included in a study by Omar Ab El-Moneen et al. [8].

Preoperative and postoperative radiological scoring (at 6 months) of patients with CRS (n = 16) was compared in our study and it showed the marked improvement in all patients. Total preoperative score was 334 (mean 20.87 ± 5.41) and total post operative score was 144 (mean 2.75 ± 2.21). P value was less than 0.001 which is statistically significant. Our results are more or less similar to a study by Deepti et al. [9] who in their study found that preoperative score was 15.05 ± 5.73 which dropped to 4.85 ± 4.64 postoperatively (P value < 0.001).

Pre and post operative Lund and Mackey endoscopic scoring of patients with CRS (n = 16) was compared and it showed marked improvement. Total score preoperatively was 150 (mean 9.37 ± 2.25), post operative score at 3 months and 6 months follow up was 22 (mean 1.38 ± 0.81) and 9 (mean 0.56 ± 0.51) respectively. P value was less than 0.001 at both follow ups which is statistically significant. Similar reduction in mean was noted by Deepti et al. [9] who in their study found that the mean dropped from 7.40 ± 2.89 to 2.85 ± 1.09 at 6 months follow up postoperatively.

Total SNOT 22 scoring of patients with CRS (n = 16) was 748 (mean 46 ± 9.40). Post operative total SNOT-22 score at an interval of 3 months and 6 months was recorded to be 91 (mean 5.69 ± 1.58) and 45 (mean 2.81 ± 0.91) respectively. P values at both follow ups were less than 0.001 which were statistically significant. Similar to our study, Smith et al. [10] in their study titled “Endoscopic sinus surgery compared to continued medical therapy for patients with refractory chronic rhinosinusitis” noted in 31 patients mean baseline SNOT-22 score as 57.6 and after 14.6 months of Endoscopic sinus surgery the mean dropped to 16.0 which was statistically significant.

Visual analogue scoring (VAS) was used to study the utility of Image guided surgery. Pre and postoperative (VAS) was compared in all patients. Total preoperative VAS score was 507 (mean 25.35 ± 10.16) and total VAS score after 3 months and 6 months follow up was 73 (mean 3.65 ± 1.57) and 62 (mean 3.15 ± 1.69) respectively. At 6 months of follow up there was 85% reduction in the VAS symptom score. P value at 3 and 6 months of follow up were < 0.001 which were statically significant. Lupoi et al. [11] in their study “SNOT-20 and VAS questionnaires in establishing the success of different surgical approaches in chronic rhinosinusitis” noted mean preoperative VAS score at baseline as 5.15 points which decreased to 2.36 points at 3 months follow up, 2.3 points at 6 months follow up and 2.56 at 1 year after endoscopic sinus surgery. P value for VAS was 0.011 (< 0.05) showing statistical relevance of endoscopic procedures in terms of improving Quality of life of patients with CRS. It showed 55% reduction of VAS symptom score at 6 months of follow up. There was more reduction in VAS scores in or study then seen in above study as image guided endoscopic sinus surgery helps in better clearance of disease and hence more reduction in VAS score.

In this study out of 12 patients (60%) who had undergone previous FESS, 6 patients (50%) were operated once, 5 patients (41.66%) were operated twice and 1 patient (8.33%) was operated thrice. A Study done by Bajaj et al. [12] titled “Functional endoscopic sinus surgery: Review of 266 patients” included 266 patients of CRS who underwent endoscopic sinus surgery including 41.7% patients of revision cases. In our study percentage of revision cases was more (60%) than above reported study as primary cases of CRS with minimal disease were excluded in our study.

Total no of revision cases in our study were 12 and out of them inferior turbinate was absent in 1 patient (8.33%), middle turbinate was absent in 10 patients (83.3%), uncinate process was absent in 12 patients (100%) and bulla ethmoidalis was absent in 10 patients (83.33%). A study done by Bewick et al. [13] studied 75 cases of revision FESS and noted resection of middle turbinate in 35% of cases, and absent uncinate process in 36% of cases. The difference in percentage of absent nasal landmarks in our study than the above reported study can be explained as number of patients in our study was less.

Installation of navigation system took on an average 15–20 min in first 10 cases and in second ten cases it took 10–15 min. This set up time is by and large similar to that observed by Chu et al. [14] in their experience of 79 cases of endoscopic sinus surgery under navigation system. Mean set up time in their cases was 10.6 min. Samarakkody et al. [15] in their study stated that registering the probe and equipments requires at least 15 min of the operative time which is similar to our set up time.

Mean number of sinuses operated was 7.8 ± 2.14, mean operative time was 112 ± 17.32 min, and average blood loss was 100 ±23.54 (100–200). Similarly Chu et al. [14] concluded that the mean number of sinuses operated on was 5.8, mean operative time was 112.3 min and the mean blood loss was 102.5 ml. Our mean no of sinuses operated were different than theirs as in our study number of cases were less.

Most published reports suggest that the achievable target registration error is in the 1.5–2 mm range. We found the accuracy of our system was 1.25 ± 0.73 mm. Chu et al. [14] found accuracy was 1.08 mm. Eliashar et al. [1] found in their study that in 94% the Image Guided system provided accurate anatomical localization with less than 2 mm localization error (1–2 mm, mean 1.6 mm).

Minor complications were seen in our study. Minor bleeding less than 200 ml in 3 patients (15%), postoperative periorbital echymosis in 2 patients (10%),postoperative synechiae in 2 patients (10%) and in 1 patient (5%) with potts puff tumor middle turbinate got lateralized postoperatively which was subsequently resected under local anesthesia. No major complication like orbital/intracranial/major hemorrhage was seen in our study. On contrary a similar study by Masterson et al. on IGS found 4 (3.03%) patients had a major complication. Similarly Chu et al. [14] found major complication of major bleed in 4 patients (5.06%). No other major complication was seen in their study. Two patients (2.3%) developed minor bleed. In another study done by Eliasar et al. [1] out of 34 patients taken for navigation assisted procedures, 33 procedures (97%) remained uneventful. The low risk of complications especially major as seen in our study is further strengthened by the recent met analysis by Dalgorf et al. [16] who concluded that there is evidence from published studies that the use of IGS for sinus surgery is associated with a lower risk of major and total complications with non IGS sinus surgery in selected populations.

In this study advantages of IGS noted include: Localization of operating instruments in relation to pathology/vital structures and saggital reconstruction with three dimensional imaging capacities which increases the safety of the patients, improves surgeon’s reassurance, and reduces the chances of major intracranial or intraorbital complications especially in revision cases with distorted nasal anatomy and absence of crucial nasal landmarks. Image guided surgery also proved beneficial as a teaching tool for residents/paramedics. We also noted some disadvantage in this study which include: Expensive equipments, increase in the duration of operative time, need of satisfactory registration as critical for accurate surgical navigation and accuracy errors of 1–1.5 mm that are sometimes crucial for accurate surgical navigation.

Our study is not without shortcoming as expected with the first time use of IGS in our department. The sample size is quite low. Inexperience in using IGS could have biased our findings. The scores used are subjective and there are chances of errors in their documentation.

Conclusion

Image guided surgery has grown from being a curious novelty to a near necessity. Advantage of IGS noted include localization of operating instruments in relation to pathology/vital structures on three dimensional imaging capacity which increases safety of the patient, increases surgeons reassurance especially in revision cases with distorted nasal anatomy/absence of crucial nasal landmarks. The challenge for the surgeon is to determine which cases would benefit from its use both in the assessment of the patients disease and his/her own personal surgical expertise. Due to the preponderance of benefit over harm and taking into consideration the severity of potential surgical complication, this study finds IGS to be a valuable tool in carefully selected cases.

Funding

The research did not receive any fundings but is a postgraduate thesis of a candidate.

Availability of Data and Materials

This study is a postgraduate thesis done under the first author and is transparent without any manipulations or fraud statements.

Compliance with the Ethical Standards

Conflict of interest

None.

Consent to Participate

Proper consent taken from patient whenever needed.

Consent for Publication

No consent was required as everything was recorded in patients file, consent was taken in two patients whose endoscopy images we have submitted.

Ethical Approval

Approved by colleges ethical committee.