Introduction
Scapula is a large triangular flat bone in the posterolateral aspect of upper part of thorax extending from 2nd to the 7th rib. It has 3 borders, lateral medial & superior borders. Superior border is the thinnest & shortest of all and begins from the superior angle and passing horizontally lateral wards, it ends into a notch, the suprascapular notch, which seperates it from the root of the corocoid process.1
The inferior belly of omohyoid muscle takes origin from the medial end of the notch. A transverse scapular ligament [TSL] bridges across the notch to form a suprascapular foramen which transmits the suprascapular nerve to the supraspinous fossa. The suprascapular vessels, however reach the fossa above the foramen & its ligament.2 The notch is bridged by the superior transverse ligament or tranverse scapular ligament which is attached to the root of the corocoid process & medially to the summit of the notch. The ligament is sometimes ossified, the foramen thus completed, transmits the suprascapular nerve, whereas the suprascapular vessels pass backwards above the ligament.3
Later to this course, the suprascapular nerve & suprascapular artery together pass through the spinoglenoidal notch being covered by spinoglenoidal ligament as shown in the Figure 1. The compression of the suprascapular nerve can be due to the ossified transverse scapular ligament, congenital abnormalities or fracture of the scapula.4
The ossified suprascapular ligament may be of various patterns,it can be a partial or completely ossified, the ligament could be a trifurcated or can have anomalous bands of it. A thorough imaging and knowledge of anatomy of the course of the nerve is helpful in surgeries of decompression of the suprascapular nerve.5 Hence the aim of the present study is to know the course and variations in the suprascapular nerve which can be compressed by ossified transverse scapular ligament [TSL] leading to the nerve entrapment and other neurovascular deficits.
Similar studies on the ossified transverse scapular ligament have been done. In a study by Shiksha Jangde6(2015) incidence of complete ossification was 4.1% of the bones studied. In a study by Sachin Patil7 (2019) the suprascapular ligament was ossified completely in 3.54% bones studied. Marcos Rassi et al8 (2012) showed in their study that suprascapular block is an effective therapautic method used by anaesthesiologists both for regional anaesthesia & post operative analgesia of the surgeries on shoulder. They concluded that the suprascapular nerve block is an extremely effective procedure in the shoulder pain therapy.8
All the data indicate that a thorough knowledge of the course of suprascapular nerve and nature of the notch whether partially or completely ossified is to be evaluated before the surgical decompression and release of the nerve in case of neuropathies and compression of the suprascapular nerve by the ossified suprascapular ligament.
Materials and Methods
The study was a gross anatomy -- bone study done on the dry scapula bones collected from dept of Anatomy which was there for undergraduate students study.
The study was done between 2019 – 2021 over 3years, the study included 127 scapula bones,81 right scapulae and 46 left sided scapulae of unknown sex. The broken & malformed scapulae were excluded from the study. The superior border of the scapula was carefully studied for the presence of the ossified transverse scapular ligament[TSL], presence of any other foramen in the supraspinous fossa, the findings were recorded accordingly and tabulated.
Results
Following are the results of the study done.
Figure 3
A. & B.: Show the ossified Suprascapular ligament on RIGHT side; C.& D: Show the ossified Suprascapular ligament on LEFT side
Figure 4
A & B) Showing the Accessory foramen in the supraspinous fossa. Also in fig (a) there is a small bony spike depicting the partially ossified transverse scapular ligament.[TSL]
The number of specimens studied – 127 scapulae, out of which right sided scapulae were 81[n – 81] and left sided scapulae were 46 [n – 46].
Ossified transverse scapular ligament [TSL] was seen in 6 out of 81 right sided scapulae studied.(Figure 3)
In the left sided scapulae 4 out of 46 scapulae had ossified TSL.(Figure 3)
The results were tabulated and 10 out of 127 dried scapulae had ossified transverse scapular ligament ie 7.87% which was closely corresponding with the studies of other Indian workers on scapulae, as depicted in Table 2.
Accessory foramen were seen in supraspinous fossa in 3 out of 127 scapulae studied, partially ossified TSL was seen in 1 scapula. (Figure 4a)
Table 1
Showing presence of Ossified Transverse scapular ligament [TSL]
A comparision was made regarding correlating the works of various authors on the ossification of TSL over the years. The list is tabulated in Table 2, which showed variation in the occurance of the ossification of TSL based geographical differences, sample size and most of the studies had taken bones of unknown sex only the sides of the scapulae was taken into account which showed slight prepondarance to right side, considering right handedness is common.
Table 2
Comparision of ossified suprascapular notch in other studies
|
S. No |
Name of authors : |
No of bones studied |
Incidence of ossification of notch in scapula bone |
|
1. |
Ticker et al4 [1998] |
79 |
5% |
|
2. |
Dunkelgrun et al.9 [2003] |
623 623 |
7.3% |
|
3. |
Silva et al. 10 [2007] |
221 |
30.76 % |
|
4. |
Sinkeet et al.11 [2010] |
138 |
2.9% |
|
5. |
Polguj et al12 [2011] |
86 |
7% |
|
6. |
Shiksha Jangde et al6 [2015] |
7 73 |
4.1% |
|
7. |
Sachin Patil et al7 [2019] |
118 |
3.54% |
|
8. |
Present study[2022] |
12 127 |
7.87% |
Discussion
The study of the ossified transverse scapular ligament [TSL] has been studied by various workers and the results also are varied depending on the sample size as well as the propensity of occurance of the variations in the samples collected in different areas. We shall go through the observations of various authors.
Various authors have classified the shape of suprascapular foramen based on its appearance into U shape, V shape & J shaped notches of scapula. Natsis et al13 [2007] have described the V shaped suprascapular notch based on vertical and transverse diameters measured by them.
Rengachary & workers14 [1979] have described 6 different types of suprascapular notches and opined that the suprascapular nerve entrapment is an acquired neuropathy secondary to the nature of work and occupation.
Type 1: lacks a discrete notch.
Type 2: is a wide Vshaped notch.
Type 3: is a wide Ushaped notch
Type 4: is a narrow Vshaped notch with partial ossification.
Type 5: is a narrow Ushaped notch with partial ossification.
Type 6: is a completely ossified suprascapular ligament converting the suprascapular notch into foramen.[ as seen in our study]
Knowing the course of the suprascapular nerve where its passing beneath the TSL at the superior border of the scapula, common cause of the nerve compression is by ossification of TSL, other reasons being direct trauma, fracture of scapula, ganglion cysts, lipomas of the back, occupation related straining as in manual labourers, stretch injuries & tumours as described by Paolo & workers.15
In a study by Thompson & workers16 on peripheral entrapments neuropathies in upper extremity describes the variation in the ligament bridging the suprascapular notch may irritate the suprascapular nerve & give rise to pain which is deep & poorly localised, which is the reason why the cause of pain & tenderness is difficult study to discover in any indivisual and muscle atrophy starts. In one of the study by Natsis and workers13 found narrowing of the suprascapular notch may be due to partial or complete calcification of TSL, presence of the bony ridge irritates or compresses the nerve giving rise to suprascapular nerve entra ment syndrome.
As described by Marcos Rassi and workers8 in their study on suprascapular nerve block stated that the suprascapular block is an effective therapautic method used by anaesthesiologists both for regional anaesthesia & postoperative analgesia of the surgeries on shoulder. They concluded that the suprascapular nerve block is an extremely effective procedure in the shoulder pain therapy, after arthroscopic procedures on the shoulder.
Conclusion
The occurances like ossification of TSL have different results in different studies done which is again varied depending on the samples collected in that particular area of the study. In our study the occurance of ossification of TSL in adult scapulae was seen in accordance with earlier studies. The compression of suprascapular nerve by the ossified TSL can be one of the causes of neuropathy in the region of back.
Partial or complete ossification of the TSL should be kept in mind while evaluating the case of long standing poorly localised pain around the shoulder which could be associated with slight muscle atrophy. But the knowledge of such types of variations is essential to the anatomists while dissection as the findings are of academic significance. These facts are helpful for the surgeons, orthopaedicians who are operating in this area. Also the understanding of the course of the suprascapular nerve is necessary to the anaesthetists to give the nerve block as post operative analgesia after the arthroscopic procedures on shoulder. It's useful for the radiologists to not confusing the ossified ligament for atypical bone growths or the tumour. A thorough knowledge of the nerve course and variations will help in the management of the neuropathies associated with it.
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