The uncinate process is a saber-shaped ethmoid bone that attaches to the lateral nasal wall through multiple bony and fibrous attachments. It is a thin bony process projecting posteroinferiorly from ethmoidal labyrinth.  It performs a functional role in the ventilatory physiology of the nasal cavity and the paranasal sinuses. During endoscopic sinus surgeries, the uppermost segment of unicinate process is a blind spot for surgeons.^1,2 The superior attachment of the uncinate process may alter the tract of frontal sinus outflow which predispose to development of frontal sinusitis.³The uncinate process is considered  to be as one of the most important surgical landmarks of the lateral nasal wall for endonasal sinus surgeries. Normal variations in the morphology of the uncinate process give rise to several patterns of drainage from the osteomeatal complex (Isobe, 1998). Pneumatization of the uncinate process is an anatomic variation that can impair sinus ventilation, especially in the anterior ethmoid, frontal recess, and infundibular regions . ⁴Any abnormal growth or excessive pneumatization of the uncinate process can narrow down and ultimately obstruct the outflow tract of multiple sinuses. It also has been implicated as a possible etiologic factor in some cases of recurrent sinusitis and headaches.⁴ However, pneumatization of the uncinate process is an uncommon variation.

The uncinate process, being one of the first structures encountered intraoperatively, hence given immense surgical importance now a days.⁵ Preoperative detection of anatomic variations of the uncinate helps  to avoid intra-operative damage to important structures like the nasolacrimal duct, medial orbital wall, sphenopalatine artery etc.^6,7 Special care should be taken in order to avoid aggressive traction and torque on the upper tip of the uncinate process during uncinatec­tomy, which may inadvertently damage the ethmoid roof. On the basis of superior attachment, uncinate process is classified as Type 1-Insertion of uncinate process into the lamina papyracea, Type 2-Insertion of uncinate process into the roof of the ethmoid (the skull base) and Type 3-Insertion of uncinate process into the middle turbinate. Common uncinate process anomalies include laterally or medially deviated uncinate process, hypertrophied uncinate process and

pneumatization of uncinate process. Rarely, the uncinate process may be entirely absent.

MATERIAL AND METHOD

This cross sectional observational study was conducted by Postgraduate Department of Anatomy in collaboration with Department of Radio-diagnosis and Imaging, Government Medical College, Srinagar . This study was done on 200 cases. In this study cases  with any history of trauma, previous surgery or pathology distorting normal anatomy in sinonasal region were excluded. The cases of age<20 years were excluded due to the developmental stages of the paranasal sinuses .Non-contrast CT scan Nose and Paranasal sinuses (NCCT Nose &PNS) was done using Siemens Somatom Emotion 16 slice Multidetector Spiral CT scan. The mode of attachment of the uncinate process was carefully studied so as to ascertain the pathway of drainage of frontal sinus. The images were analyzed to see the superior attachment of uncinate process in coronal plane. The superior attachment of uncinate process was classified as Type 1-Insertion of uncinate process into the lamina papyracea, Type 2- Insertion of uncinate process into the roof of the ethmoid (the skull base) and Type 3-Insertion of uncinate process into the middle turbinate. The superior attachment of uncinate process was noted in 400 sides and categorized. Besides  any variations in uncinate process were also studied. A pre structured proforma was used to collect relevant data. Photographs generated were photographed at appropriate window widths and window level to depict the anatomical variant.

Technical parameters of CT scan

RESULTS

In our study of 200 cases (400 sides), in majority i.e. 317 (79.25%) sides uncinate process was superiorly attached to Lamina papyracea (type 1), in 61 (15.25%) attached to skull base(type 2) and in 22 (5.50%) sides uncinate process was attached to middle turbinate(type 3) as shown in  table no.-I. In our study of 200 cases, pneumatized UP was found in 4 (2.00%) cases, 3 (1.50%) on left side and 1 (0.50%) on right side while only in 1(0.50%) case hypertrophied UP was found on left side as can be read from table no.-II

TABLE-I: SUPERIOR ATTACHMENT OF UNCINATE PROCESS ON NCCT NOSE & PNS (N=200, TOTAL NO OF SIDES=400)

TABLE-II: VARIATIONS IN UNCINATE PROCESS ON NCCT NOSE & PNS (N=200)

Computed tomography (CT) scan

The coronal computed tomography (CT) scan showing Type 3

uncinate process superior attachment (arrow)

DISCUSSION

Osteo meatal region is frequently prone for anatomical variations that results in osteomeatal obstruction and blockage of mucus drainage leading to chronic rhinosinusitis. One of such variation is different patterens in superior attachment of uncinate process that impairs ventilation of anterior ethmoid, frontal and infundibular sinus regions leading to chronic pathology warranting uncinectomy⁸. Injudicious removal of the uncinate process especially in cases with allergic rhinosinusitis can  result in exposure of the sinus mucosa to contaminated air  thereby causing persistent or even worsening of the mucosal disease in the ethmoid cavity and its dependent sinuses .⁹Some of authors are of opinion that uncinate process probably prevents direct ventilation of sinuses with contaminated inspired air .^10,11

In our study of 200 cases (400 sides), most common in 317(79.25%) sides uncinate process was superiorly attached to lamina papyracea (type 1), in 61 (15.25%) sides attached to skull base (type 2) and in 22 (5.50%) sides uncinate process was attached to middle turbinate (type 3). Our study makes trend of type 1>type2>type3. Isha Preet Tuli et al (2013)¹² evaluated 50 patients of chronic sinusitis (100 sides) in India. They reported Type I uncinate process in 79.8 %. Type II uncinate process was seen in 16.67 % and Type III was seen in 3.57 %.Another Indian study by Gnanavelraja C et al (2014)¹³ reported Type 1 uncinate process in 59%, Type 2 uncinate process in 24% and Type 3 uncinate process in 17.5%.The results of our study concerning superior attachment of uncinate process are quite consistent with the results made by above mentioned Indian studies. In all studies mentioned above the most common type of attachment was to lamina papyracea, similar to trend  as reflected in our study.

 In present study, pneumatized UP was found in 4 (2.00%) cases, 3 (1.50%) on left side and 1 (0.50%) on right side. Also a single case of hypertrophied UP (0.50%) was found on left side. Indian studies by Isha Preet Tuli et al (2013)¹² and Partha Sarathi Sarkar et al (2016)¹⁴ found pneumatization of uncinate process in 4% and 2.6% respectively on NCCT Nose and PNS. Also retrospective study done in Romania by Vasilica Baldea et al (2012)¹⁵  reported pneumatization of uncinate process in 3.41%. Asif A Wani et al (2009)¹⁶ studied CT scans of 150 patients with chronic rhinosinusitis and reported hypertrophied uncinate process in 14% cases. In 10% cases hypertrophied uncinate process was present unilaterally and in 4% bilaterally.Our observations concerning the pneumatization of uncinate process is in accordance to that observed by above mentioned authors while our observation concerning hypertrophied uncinate process is very less as compared to Asif A Wani et al (2009)¹⁶. It may be attributed to fact that  study done by them was conducted on symptomatic patients with chronic rhinosinusitis in which medical treatment for atleast 6months had failed while no such inclusion criterion were in our study.

CONCLUSION

 Accurate knowledge about the anatomical variants of the Uncinate process is critical for surgeons, especially with the advent of functional endoscopic sinus surgery(FESS). It is necessary for the surgeon to be cognisant of any of the uncinate process variations in the patient undergoing FESS especially when an uncinatectomy is contemplated.

REFERENCES

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