Variations in the Shape and Dimension of the Suprascapular Notch in Dried Human Scapula-An Osteological Study with its Clinical Implications
Apurba Patra, Manjeet Singh, Harsimarjit Kaur
1. Senior Resident, Department of Anatomy, Government Medical College Patiala, India. 2. Professor and HOD, Department of Orthopaedics, MMIMSR, Mullana, India. 3. Associate Professor, Department of Anatomy, Government Medical College Patiala, India.
Correspondence Address :
Dr. Apurba Patra,
House no:15 E, Rajindra Medical Complex
New Lalbagh Colony Patiala, India.
: The suprascapular notch is a depression on the superior border of scapula which gives passage to the suprascapular nerve to enter the supraspinatus fossa. During its course there is a chance of entrapment of the nerve while in the notch due to its variant shapes and dimensions which leads to suprascapular nerve entrapment syndrome.
Aim: The purpose of the study was to determine the variations of the shape and dimensions of suprascapular notch of scapula because these parameters may be the causative factors in nerve compression.
Materials and Methods: A total 110 dried human scapula of both sides were included in the study. First they were grossly examined for variations in shape of the notches. Then vertical and transverse dimensions of the notches were measured with the help of digital vernier calliper.
Results: As per classification by shape we found 43 ‘J’ shaped (39.09%), 35 ‘U’ shaped (31.81%), 10 ‘V’ shaped (9.09%), indentation in eight cases (7.27%), absent in five (4.54%), partial ossification of STSL in four (3.63%) and complete ossification in five (4.54%) scapulae. The results were also analysed according to Natsis classification after excluding the Scapulae with indentation and partial ossification of ligament. Five (5.1%) scapulae Type I, sixty six scapulae (67.34%) had Type II, 14 scapulae (14.28%) had Type III, five (5.1%) had Type IV and none (0%) had Type V. We also found eight scapulae (8.16%) with transverse diameter equal to the vertical diameter (Td=Vl).
Conclusion: The present study showed various types of suprascapular notches. Out of these Iqbal type ‘U’ and Natsis type II were most predominant. In both the cases chance of suprascapular nerve compression is less as more space is available to the nerve. The present study also showed five cases of completely ossified STSL where chances of impingement are higher. Since, these anatomical variations are not uncommon in population so there is a need for clinicians to have precise anatomical knowledge of SSN before making proper diagnosis and planning for surgical interventions of suprascapular nerve entrapment syndrome. We hope our study will be helpful in providing anatomical knowledge to the clinicians.
|Keywords : Nerve decompression, Rotator cuff dysfunction, Suprascapular nerve, Superior Transverse Scapular Ligament (STSL)|
The suprascapular notch (SSN) is a depression present on the lateral aspect of superior border scapula just medial to the coracoid process. In few cases this notch is transformed into a foramen due to ossification of superior transverse scapular ligament (STSL) and serves as a bony tunnel for suprascapular nerve. The SSN is the main site of suprascapular nerve compression, which may result in significant dysfunction of rotator cuff. This pathology was first described as suprascapular nerve entrapment syndrome by Kopell and Thompson (1). This disease is characterized by dull aching pain over the posterolateral region of the shoulder, atrophy of the supraspinatus and infraspinatus muscles and weakness during external rotation and initiation of shoulder abduction (2),(3). The shape and size of the SSN is the most important causal factor in the etiopathogenesis of suprascapular nerve entrapment syndrome (4),(5). A narrow SSN may predispose an individual to this entrapment neuropathy (6). According to previous literatures a V-shaped notch is more likely to be associated with nerve entrapment (7). Therefore, sound knowledge of the anatomy and morphology of the suprascapular region, especially variations in shape and size of SSN and ossification of STSL, are particularly important in various surgical techniques associated with arthroscopic suprascapular nerve decompression (8),(9),(10). A precise anatomical knowledge of the shoulder-girdle region is of great importance in order to avoid iatrogenic neurological complications while performing open, arthroscopic or arthroscopically assisted surgical procedures. In our opinion this osteological study provides a comprehensive anatomical and morphological description of SSN based on its specific geometrical parameters and describes almost all its variations.
|MATERIAL AND METHODS|
It was an observational study, total 110 dried human scapulae were collected from bone room of Anatomy Department of Government Medical College, Patiala and grossly examined over a period of six months in the year of 2014, irrespective of age, sex, gender, race and left or right sidedness. Defective and broken scapulae were excluded from the study. The following observations were made –
1. Various shapes of SSN 2. Absence of SSN and 3. Presence of suprascapular foramina instead of SSN (Ossification of superior transverse scapular ligament). 4. Vertical and transverse dimensions of suprascapular notch.
On gross examination, the SSN was classified into three distinct types as proposed by Iqbal et al., (11) namely the V-shaped SSN, defined as having medial and lateral sidewalls converged into a narrow base; a U-shaped SSN, defined as having approximately parallel sides with a rounded base; a V-shaped SSN and J shaped SSN. To classify the notch as proposed by Natsis et al., (5) the vertical and transverse dimensions of SSN were also measured using digital vernier calliper. The Scapulae with indentation and partial ossification of ligament were excluded from the measurement. Transverse diameter is the distance between the two edges of the notch and vertical diameter is the distance between the deepest point of the base of the notch to the midpoint of the line joining the two edges.
In this study three different types of notches were observed along with partial or complete ossification of STSL. Depending on the shape of the notch, scapulae were grouped (Table/Fig 1) following the Iqbal classification (11). Of these scapulae, 43(39.09%) showed ‘J’ shaped (Table/Fig 2), 35(31.81%) ‘U’ shaped (Table/Fig 3), and 10(9.09%) ‘V’ shaped (Table/Fig 4) suprascapular notches. In eight (7.27%) cases an Indentation (Table/Fig 5) was seen instead of notch and five (4.54%) scapulae were without discrete notch (Table/Fig 6), four (3.63%) bones with ‘U’ shaped notches showed partial ossification (Table/Fig 7) and five (4.54%) bones showed complete ossification (Table/Fig 8).
Depending on the dimensions of SSN, scapulae were grouped as proposed by Natsis et al. This study observed five scapulae (5.1%) without a discrete notch (Type I), 66 scapulae (67.34%) showed notches where transverse diameter was more than vertical diameter (Type II), in 14 scapulae (14.28%) vertical diameter was more than transverse diameter (Type III) and five scapulae (5.1%) had ossification of the transverse scapular ligament (Type IV) (Table/Fig 9).
Apart from those classified in the Natsis classification, our study also found one more type in eight scapulae (8.16%) where transverse diameter was equal to the vertical diameter.
Knowledge of detail anatomy of SSN is necessary for proper diagnosis and treatment of shoulder girdle disorder. Though there are various literatures describing SSN, very few of them highlight on both of its qualitative and quantitative anatomy. In the present study an effort has been made to classify SSN based on its shape and dimensions.
Various authors have classified SSN based on certain parameters and gross examination of its shape. Ticker et al., (12), Bayramoglu et al., (14), Sinkeet et al., (14) have classified SSN on the basis of morphological appearance into two types - ‘U’ and ‘V’ and found ‘U’ shaped notch to be the most common variety. Iqbal et al., (11) classified SSN into three types - ‘U’, ‘V’, J’ based on their shapes on gross examination. Soni et al., (15) reported five types of SSN as ‘U’, ‘V’, ‘J’, indentation and absence of notch. The present study predominantly showed Iqbal type ‘U’ shaped notches. The results of the present study compared with those of previous studies based on shape are tabulated in (Table/Fig 10).
Nastis et al., (5) classified SSN based on vertical and transverse diameter measurements and Polguj et al.,(20) assessed SSN using three geometrical parameters such as maximal depth, superior and middle transverse diameter and included one more type of SSN in his classification where Td=Vl as found in our study also. The present study predominantly showed Natsis type II suprascapular notches where the transverse diameter is more than the vertical diameter. In both the predominantly found ‘U’ shaped and Natsis type II SSNs in our study, there are less chances of suprascapular nerve entrapment syndrome as more space is available for the suprascapular nerve (Table/Fig 11).
In our study, the frequency of scapulae with a bony foramen was 4.54% of all cases, which was higher than that seen by Sinkeet et al., (14) (3%), Tubbs et al., (26) (3.7%), Rengachary et al., (6) (4%) and Sangam et al., (27) (1.93%). However it was lower than that described by Natsis et al., (5) (7.3%), Bayramoglu et al., (14) (12.5%), Mistry et al., (28) (19.44%), Vasudha et al., (17) (6%) and Kannan et al., (29) (10%). Ossification of superior transverse scapular ligament narrows the space for the suprascapular nerve which irritates it during different shoulder movements thereby increasing the likelihood of suprascapular nerve entrapment. (Table/Fig 12).
The suprascapular nerve is very intimately related to the SSN while passing through it. Variations in shape and size can be considered as a possible aetiological factor in nerve impingement. Moreover, ossification of STSL converts the notch into foramen and reduces the space available to the nerve leading to suprascapular nerve entrapment syndrome characterized by pain during initiation of shoulder abduction. The present study showed various types of suprascapular notches. Out of these Iqbal type ‘U’ and Natsis type II were most predominant. In both these cases chance of nerve compression is less as more space is available to the nerve. The present study also showed five cases of completely ossified STSL where chances of impingement is higher. Since these anatomical variations are not uncommon in population so there is a need for clinicians to have precise anatomical knowledge of SSN before making proper diagnosis and planning of surgical interventions. We hope our study will be helpful in providing anatomical knowledge to the clinicians.
|TABLES AND FIGURES|
Welcome : Guest
Users Online :