European Journal of Cardiovascular Medicine

The superior border of scapula  at its anterolateral end is seperated  from the root of the corocoid  process by  a notch called suprascapular notch.the notch can vary in shape and size.The notch is bridged by the superior transverse ligament or suprascapular ligament  which is attached  laterally to the root of corocoid process and medially to the limit of notch.the ligament is sometimes ossified.the foramen ,thus completed transmits the suprascapular nerve to the supraspinous fossa,where as the suprascapular vessels pass backwards above the ligament. ^[1]

The suprascapular nerve(SSN) is a branch of upper trunk of brachial plexus which  pass under cover of trapezius and the pass through the suprascapular foramen to reach supraspinous fossa then it supplies supraspinatus(motor),then glenohumeral ,acromioclavicular joints and coracohumeral ligament(sensory) .thyen it passes  under spinoglenoid ligament to enter infraspinous fossa to supply infraspinatus(motor).calification of superior transverse scapular ligament (STSL)may compress SSN  which can affect the muscles supplied by it so that abduction and external rotation at the shoulder joint  may be affected.many authors have concluded that partial or complete ossification of STSL is the most common predisposing factor for suprascapular nerve entrapment syndrome. since SSN is  comparatively immobile at  origin and at Suprascapular notch  repeated shoulder and scapular movemtds  can cause nerve strechiung and injury. ^[2,3]

Our study  intends to determine the different shapes of SSN,degree of ossification of STSL,commonest type of SSN, and clinical significance of various shapes.the study will be useful for clinicians for management of  suprascapular neuropathies.

AIMS&OBJECTIVES

Aim - The detailed morphological study of suprascapular notch in dry human scapulae.

Objectives

1. to study the shape of suprascapular  notch
2. Degrees of ossification of STSL.

• To take different parameters of each suprascapular notch

1. Superior transverse diameter (STD), maximum vertical diameter (MVD), and mid transverse diameter (MTD).
2. Classification of notch based on the various parameters, comparison with other studies and clinical correlation

The present study was conducted in about 120 dry human scapulae from the stock of bones in the department of anatomy, Karwar Institute of medical sciences and also collected from undergraduate students.The scapulae were randomly selected .the age, sex and race of the scapulae

were not known.   Scapulae were randomly selected irrespective of the side .Defective and broken scapulae were excluded from the study. Ethical committee approval was taken for the study. Detailed morphological study of suprascapular notch was studied under various parameters of suprascapular notch (SSN).

1. Degrees of ossification of STSL.
2. to take different parameters of each suprascapular notch -Superior transverse diameter(STD), maximum vertical diameter(MVD), and mid transverse diameter(MTD).

• Classification of notch based on the various parameters, comparison with other studies and clinical correlation.

1. The data was statistically analysed and concluded.

Based on observations suprascapular notch were classified (type I to Type VI).

       Fig.1-showing the measurements

• Maximum depth (MD): The distance between the superior corners of the notch to the deepest point of the suprascapular notch. In the fig 1 EF is MD.
• Superior transverse diameter (STD): It is the horizontal distance between superior corners of the SSN on the superior border of the scapula.AB=STD
• Middle transverse diameter (MTD): It is the horizontal distance between the opposite walls of the SSN at a mid- point of the MD and perpendicular to it.CD=MTD

Fig.2 showing classification of Rengachary et al

In this study, all the scapulae presented with suprascapular notch. The incidence of various types of suprascapular notch was classified into six types based on Rengachary classification which defines as following types [4]

 Type I- superior border of scapula forming Wide depression from medial angle to coracoid process

 Type II- blunted large   V shape affecting the middle third of superior border

Type III Symmetric U shape with parallel margins

Type IV-Very small and narrow V shape, often with a shallow groove for the suprascapular nerve

 Type V- minimal notch which is U shaped Partial ossified medial portion of the suprascapular ligament

 Type VI- Completely ossified suprascapular ligament converting into a foramen.

In our study, following table no. 1 shows percentages of different types of SSN found

The following table  no 2 shows the various dimensions of SSN measured in our study

Polguj et al also classified  the suprascapular notch based on the difference between the notch’s maximal depth(MD) and its superior transverse diameter(STD) as following types;

Type I; MD longer than STD

Type II; MD and STD equal

Type III: STD longer than MD

Type IV: A bony bridge joins the corners of the notch

Type V; without a discrete notch

Table no.3 showing classification of SSN according to POLGUJ ET AL

Fig, 4 showing type VI SSN                                                                                     Type IV SSN

Fig.6 showing type III SSN                                                                            Type V

Chart no. 1 classification according to rengachary et al.                                                                                                                             

Chart no.2 showing classification according to poulguj et al.

Maximum depth and superior transverse diameter and mid transverse diameter of SSN was found to be more in type 3 in our study.

In our study type 3 was the commonest followed by type 5 SSN according to Rengachary et al classification?

One unusual SSN was found in our study which showed double notches which may be due to presence of double suprascapular ligaments.

A study conducted by Gopal K et al on dry human scapulae observed type II SSN as most common and Type V as least common in their study. Type I frequency was less in their study compared to other studies. ^[5]

Polguj et al conducted study on asymmetry of SSN  in CT images  of in 311 patients  and classified  5 types of SSN based on MD and STD measurements.in his study the most common type was type III in which STD   was longer than MD(66.9%) and least was type II(0.6%)in which is STD and MD will be equal.

Similar three dimensional CT scan study on SSN and superior angle of scapula by Raman K et al observed Type I of rengachery classification as the most common suggesting lower susceptabilty to SSN entrapment. ^[6,14]

A study conducted by Philip SE on 100 dry human scapulae observed U shaped notches (type III of Rengachery et al classification) as the most frequent type (38%)  followed by  v shaped notches(type II of Rengachery et al) of about 36 %.^[7]

A study by Natsis K et al found the equal frequency of  type II(having longest transverse diameter) and type III(having longest vertical diameter) in a study on 423 scapulae.the study favours wide blunted V shape and symmetrical U shape notches as common variety.  Type V in which they classified as notch with foramen was the least occurrence with 0.7%.^[8]

A study conducted by Saikia et al  on 258 scapulae observed U shaped notch as the most common(40.31%), J  shaped in 21.31%,V shape in 7.75 %,no notch in 17.44%.,slight indentation in 10.07%,and complete foramen in 3.1 %.^[9]

In a study by vasudha et al among 115 scapulae  observed the symmetrical U shape as the most common variety(34.7 8%)that coincides with type III.and least common was  SSN (0.86%)as narrow groove that is  type IV. ^[10]

A unique variation of SSN was observed in   a   3 dimensional  CT image of a patient which showed double suprascapular foramen with two bony ridges and  the nerve was passing in the upper suprascapular foramen.Similar variation with two ossified bony ridges and double foramen was observed in  a dry scapula. ^[11.12]

A study by sangam MR  et al on 104 dry scapulae found type III regachery type as most common(69.23%),in about 56.73% STD was greater than MD. A similar study  by nayak et al on 525  et al also showed type III (47.1%)as the most common type of SSN. Another study by  Islam A et alet al also showed U shaped notches (type III) as the most common followed by J shaped notches. ^{[13,17 ,18]}

A study  on 110 scapulae by Chaitra BR et al found type II (33%)as most common and type IV as least common.. Another study by Maniukm C et al  showed more deeper notches on right scapulae and in male scapulae, shallow notches on left side and in females. ^[15,16]

Dunkelgrun et al study also concludes U shaped notches have larger area comparatively than v shaped notch for the nerve. ^[19]

A study on 308  dry human  chineese scapulae observed type  J shaped notches (type  I-44.8%) as the most common followed by U shaped notches(41.9%). ^[20]

A study on Ugandan population showed a  comparatively higher incidence of ossified suprascapular ligament. ^[21]

The  description of suprascapular nerve entrapment syndrome at the site of the suprascapular notch was first showed by Koppel and Thomson.^[22]

In our study  on 120 scapulae type III  SSN of Rengachery claasification(U shaped)was the most common9 (71.5%) that correlates with most of the studies.followed by type V which is partially ossified ligament of about 8.3%.least type was type IV with narrow V shaped SSN(0.8%) .other than type III type I and II  were  more common in other studies but in our study it was type V which was second most common.other than type I ,type III was the common type with STD more than MVD .according to polguj et al classification  ,typeIII  was maximum with 45% in which STD is greater than MVD. In one scapula there was  indentation of suprascapular nitch in the middle both the sides which suggested attachment of two suprascapular ligaments and double notches.

In most of the previous studies , type III followed  by Type II and type I   were the frequently occuring type. and type IV,V,VI are less common.

Our study found that type III i.e, symmetrical U shaped SSN as the most common with 71.7 % that coincides with most of the studies.but in our study second most common was type V (partially ossified ligament)which is a unusual finding.  type IV was  least common i.e, narrow V shaped   similar to other studies.

Many studies on SSN found that type I ,II and III were comparatively more frequent than type IV,V and VI.This probably suggests that  wider  notches with lesser chances of  entrapment of nerve are comparatively more common than the narrow notches or  complete foramen with increased chances of  nerve compression.But the unusual finding in our study was that type V with partially ossified ligament was second most common type.

Our study concludes that persons  with  SSN of  narrow v or groove and partial or  complete foramen (alone or combination  of both)are more prone for suprascapular entrapment neuropathy although these varieties  are less common. Better interpretations can be made if combined with study on live persons using imaging techniques.

The knowledge of these variations should be kept in the  mind of clinicians in the diagnosis and treatment of suprascapular neuropathies.

 Conflicts of interest- none

ABBREVIATIONS

SSN - Suprascapular notch  SSn – Suprascapular nerve ,STSL - Superior transverse scapular ligament MD - Maximum depth STD - Superior transverse diameter MTD - Middle transverse diameter

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