Morphometric Study of Suprascapular Notch and Its Variations in Dried Human Scapulae

The study was undertaken to see the variation of the suprascapular notch. The notch is present on the superior border of the scapula near the root of coracoid process. It is roofed by the superior transverse ligament and is converted into foramen for the passage of suprascapular nerve. The study was carried out on 121 scapulae in the department of Anatomy RMC Loni, Ahmednagar. The parameters included in the study were presence of notch, shape of notch, transvers length of notch, edge of notch, ossification of transverse ligament and other finding were also noted. The parameters were measured by Vernier calliper and appropriate statistical tests were applied. 
The supra-scapular notch was present in 82.64% of scapulae. U Deep shaped notch was most common shape followed by J shallow shaped notch. Round edge at the depth of the notch was more common. 
The knowledge of suprascapular notch variations is of great importance for surgeons performing suprascapular nerve decompression especially by means of endoscopic techniques. Our anatomical study helps the clinicians before planning a surgery.


I. INTRODUCTION
The scapula is a flat triangular bone that lies on the posterolateral aspect of chest wall between the second and the seventh ribs. The suprascapular notch (SSN) is present at the root of coracoid process and at the lateral end of superior border. This notch is converted into a foramen by the superior transverse scapular ligament and serves as a passage for the suprascapular nerve [1].
The suprascapular nerve is commonly susceptible to compression mainly at two major sites i.e., at the level of the suprascapular notch and at the base of the spine of scapula [2]. This suprascapular nerve entrapment syndrome was first described by Kopell and Thompson in 1959 and mentioned that smaller the size of the notch, greater the chance of nerve entrapment [3]. Abduction of the shoulder joint beyond 90 °C may exert traction on the suprascapular nerve, which leads to its compression against transverse scapular ligament.
The narrow suprascapular notches have been reported in patients with the nerve entrapment. Suprascapular nerve compression may present with vague pain radiating across the scapula, dull shoulder ache, limitations of shoulder joint movements and wasting of supraspinatus and infraspinatus [4]. The suprascapular notch serves as an important landmark during arthroscopic procedures [5]. So, we have decided to study the "Morphometric study of suprascapular notch and its variations in dried human scapulae." which may have an immense help to anatomists, osteologists, anthropologists and orthopedic.

II. MATERIAL AND METHODS
The presence of suprascapular notch was studied in 150 dried scapulae of unknown age sex and race, which were collected from the Department of Anatomy Rural medical college Loni. Damaged superior border and decayed scapulae were excluded. The scapulae were divided into right and left (right 65 and left 56). Morphological features of SSN and its variation was observed according to the shape of SSN.The non-metrical parameters of the notch were as follows: Presence or Absence of notch, Shape of the notch, Nature of edge at the depth of the notch and ossification of the transverse scapular ligament. Metrical parameters were transverse width at the upper and middle part of the notch, depth of notch was measured by Vernier calliper in mm. (Fig. 1). Also, transverse, and vertical diameter of the suprascapular foramen with ossified transverse scapular ligament was measured.

III. OBSERVATIONS AND RESULTS
It is evident from Table I that supra-scapular notch was present in 82.65% of scapulae.
The supra-scapular notch was present more on right scapulae as compared to left. It is evident from Table 2 that U Deep shaped notch was most common shape followed by J shallow shaped notch. V Shallow shaped notch was seen in 14.87% of scapulae. Round edge at the depth of the notch was more common as compared to sharp edge (Table III). Transverse scapular ligament was fully and partially ossified in 16.52% of scapulae while fully ossified in 9.09% of scapulae.  Mean Transverse Diameter of ossified foramen was 9.18 mm while vertical diameter was 9.63 mm. (Table VI). Different shapes of suprascapular notch:      In one specimen suprascapular foramen was further narrowed by presence of vertical ligamentous band extending from one end of the transverse scapular ligament to the depth of the notch.

IV. DISCUSSION
Previous researchers like Rangachari [4] classified the supra scapular notch into six types as well as the degree of ossification of superior scapular transverse ligament.
Type I [8%]: Notch is absent. The superior border makes a wide depression from the medial angle to the coracoid process.
Type   [15]. The V shaped suprascapular notch is vulnerable to the abrasion and entrapment of suprascapular nerve due to the narrow base.
One unique variation of shape of scapula was W shaped found in 0.86% (Fig. 6).
It is evident from Table III nature of edge at the depth of the notch was(i) sharp edged notch 43.80% and(ii) rounded edge was 47.10% No one observed the edge of the notch. The narrow sharp edge of notch at the bottom of the suprascapular notch may predispose to the symptoms of entrapment of supra scapular nerve syndrome.
Kothandaraman U and Lokanadha S found bony prominence within the suprascapular notch and its percentage was 3.5%10.
In fully ossified and partially ossified suprascapular notch converted into foramen and reduced all diameter which may compress the suprascapular nerve and gives rise to suprascapular never entrapment syndrome. Suprascapular nerve entrapment neuropathy may occur in the supra scapular notch. The sharp edge at the bottom of the notch may be contributing factor. The suprascapular nerve may be damaged due to the trauma to the scapula and shoulder there is pain in shoulder and wasting and weakness of supraspinatus and infraspinatus [16]. suprascapular nerve arises from the upper trunk of brachial plexus. It lies in the posterior triangle of neck; it passes under the omohyoid muscle and anterior border of trapezius to enter scapular notch and passes below the superior scapular transvers ligament it enters supraspinous fossa and supply the supraspinatus muscle. Then it enters infraspinous fossa through spino-glenoid notch, here it supplies the infraspinatus muscle. It also gives the branches to the shoulder joints. The nerve may entrap at suprascapular notch due to the narrowing of neck by cyst. Ossification of superior scapular transverse ligament, fracture of scapula at spino-glenoid notch, due to this reason vague pain radiating across the scapula, dull shoulder ache, limited movement of shoulder joint wasting of supraspinatus and infraspinatus muscles [19]. Suprascapular neuropathy is a big problem in individual who have been involved in overhead abduction [14] the morphological variation of suprascapular notch is not clear but Odita J. C. et. al. [18] stated that the ossification of the coracoid process epiphysis influences the shape of suprascapular notch. The variation of the notch gives rise the suprascapular nerve entrapment syndrome [17].

V. CONCLUSION
The knowledge of suprascapular notch variations is of great importance for surgeons performing suprascapular nerve decompression especially by means of endoscopic techniques. Our anatomical study helps the clinicians before planning a surgery.