The scapula, commonly known as the shoulder blade, is a flat, triangular-shaped bone that plays a crucial role in the upper body's skeletal structure and movement. It is strategically positioned on the posterolateral aspect of the thoracic wall, spanning from the second to the seventh rib, which allows it to contribute significantly to the shoulder's range of motion and stability [1]. This broad attachment provides ample surface area for muscle attachments, facilitating various movements of the shoulder and arm. The superior border of the scapula extends between the superior and lateral angles and is distinguished as the thinnest and shortest among the three borders of the bone. Despite its delicate structure, this border serves important anatomical functions and landmarks [1]. One such landmark is the suprascapular notch, a prominent indentation located near the base of the coracoid process along the superior border. This notch serves as a passageway for vital neurovascular structures and is transformed into the suprascapular foramen by the presence of the transverse scapular ligament, also known as the suprascapular ligament. The transformation of the suprascapular notch into a foramen by the transverse scapular ligament is significant because it creates a protected pathway for the suprascapular nerve to traverse into the supraspinous fossa, ensuring proper innervation of the supraspinatus and infraspinatus muscles which are essential for shoulder movement and stability [2]. The suprascapular vessels, on the other hand, pass above this ligament, supplying blood to the surrounding muscular and osseous structures [3]. Variations in the anatomy of the superior transverse scapular ligament are quite common and can include phenomena such as calcification, partial or complete ossification, and the presence of multiple ligamentous bands. These variations can alter the size and shape of the suprascapular foramen, potentially impacting the structures that pass through it. Interestingly, in some animal species, this notch is naturally bridged by bone rather than ligament, highlighting the diversity of anatomical adaptations across different organisms [2]. Clinical implications arise when considering the relationship between the suprascapular notch and the structures it transmits. Activities involving overhead abduction of the shoulder joint can exert significant traction on the suprascapular nerve. Repeated or excessive traction may lead to compression of the nerve against the superior border of the scapula, resulting in neuropathic symptoms such as pain, weakness, or atrophy in the muscles it supplies. Anatomical variations, such as a narrow or absent suprascapular notch, have been frequently reported in patients experiencing suprascapular nerve entrapment syndromes, underscoring the importance of understanding these variations for accurate diagnosis and effective treatment [4]. The origin and pathway of the suprascapular nerve further emphasize its susceptibility to entrapment. Arising as a substantial branch from the superior trunk of the brachial plexus at Erb’s point, the nerve courses obliquely through the posterior cervical triangle towards the scapular region. Along its path, it travels laterally, passing deep to the trapezius and omohyoid muscles before entering the supraspinous fossa through the suprascapular notch, situated inferiorly to the superior transverse scapular ligament [3,4]. Any anomalies or constrictions along this pathway, particularly at the suprascapular notch, can predispose individuals to nerve compression and associated clinical symptoms. Rangachary et al. have conducted extensive studies identifying six distinct types of anatomical variations of the suprascapular notch, providing a detailed classification system that aids clinicians and anatomists in recognizing and understanding these differences [5,6]. Type I variation is characterized by the complete absence of a notch, resulting in a smooth superior border of the scapula. Such variations, especially when combined with anomalies in the superior transverse scapular ligament, can significantly increase the risk of suprascapular nerve entrapment due to altered or restricted passageways for the nerve [5,6,7]. Recognizing these variations is crucial during surgical procedures and in the diagnosis of shoulder pain etiologies to prevent inadvertent nerve damage and to tailor appropriate therapeutic interventions. In the context of the Indian population, there is a notable scarcity of comprehensive data regarding the complete absence of the suprascapular notch and its prevalence. This gap in knowledge underscores the necessity for focused anatomical studies to document and compare the incidence rates of such variations within this demographic. Understanding these patterns is vital not only for enhancing anatomical knowledge but also for improving clinical outcomes through better-informed surgical approaches and diagnostic processes. Therefore, the present study is designed to meticulously document and analyze the occurrence of a completely absent suprascapular notch and to elucidate its clinical significance, thereby contributing valuable insights to both anatomical science and medical practice

Sixty adult scapulae of unknown age and gender were analyzed in this cross-sectional study in the anatomy department of the Bhagwan Mahaveer Institute of Medical Sciences in Pawapuri, Nalanda, Bihar (India). Among that, thirty scapulae belong to the right side and thirty to the left. Each scapula was observed for the absence of the suprascapular notch.

Inclusion Criteria:

1. Dry Scapulae:

• Human dry scapulae, regardless of age, sex, or ethnicity, that are available for study.
• Scapulae that are well-preserved and have all the important parts intact, especially where the suprascapular notch is usually found.

1. Complete Scapulae:

• Scapulae that are whole and undamaged, allowing for easy identification of whether the suprascapular notch is present or absent.

Exclusion Criteria:

1. Damaged Scapulae:

• Scapulae that are broken, cracked, or worn out in a way that makes it hard to see the area where the suprascapular notch should be.

1. Non-Human Scapulae:

• Scapulae from animals, as the study is focused only on human bones.

1. Pathologically Altered Scapulae:

• Scapulae that have been affected by diseases or deformities that might change or hide the natural shape of the suprascapular notch.

1. Altered Scapulae:

• Scapulae that have been surgically altered or repaired in a way that could affect the study of the suprascapular notch.

In this study, an analysis was considered significant if the p-value was less than 0.05. Graph Pad Prism version 9 was used to statistically analyze the results. Representative photographs of the absence of a suprascapular notch were taken using a digital camera.

In our study, we examined 60 scapulae in total, with 30 from the right side and 30 from the left. We found that the majority of the scapulae, 55 out of 60 (91.67%), had a suprascapular notch. Specifically, 27 right scapulae (45%) and 28 left scapulae (46.67%) had the notch. On the other hand, only 5 scapulae (8.33%) were missing the notch 3 from the right side (5%) and 2 from the left side (3.33%). The incidence was more prevalent on the right-side scapula as compared to the left side scapula [Table 1 and Figure 1]. However, the statistical analysis showed no significant difference between the right and left scapulae regarding the presence or absence of the notch (Chi-square value = 0.218, P-value = 0.640).

Table 1: Sidewise allocation of scapulae

Figure 1: Right and left-sided scapula having a complete absence of the suprascapular notch

Figure 2: Sidewise allocation of the scapula (in percentage)

The suprascapular notch is typically present in all scapulae, but various studies have documented different morphological variations and classifications of this notch across different populations. In 1979, Rangachary et al. [5,6] conducted a study on 211 American scapulae and classified the suprascapular notch into six types (Type I – Type VI) based on the notch's width at the superior border, the widest point within the notch, and its depth. They found that 8% of the scapulae they studied lacked a distinct suprascapular notch (Type I). Similarly, in our study, we observed an 8.33% incidence of a completely absent suprascapular notch, which closely aligns with Rangachary et al.'s findings. In a separate study, Sinkeet et al. (2010) [8] analyzed 138 scapulae from the Kenyan population and identified 3 scapulae without notches and 30 scapulae with a concave superior border (a wide depression extending from the medial superior angle to the base of the coracoid process) but lacking a distinct notch. Thus, 33 out of 138 (23.91%) scapulae in their study showed a complete absence of the notch, which is higher than the 8.33% incidence found in our study. These findings indicate that the incidence of a completely absent suprascapular notch varies across different populations, as shown in Table 2. For instance, it has been reported at a higher rate in the Chinese population (28%) [14], followed by the Kenyan population (23.91%) [8]. When comparing the incidence of a completely absent suprascapular notch in the Indian population, as detailed in Table 3, our study's 8.33% incidence is lower than the rates reported by Muralidhar Reddy Sangam et al. [9] (21.15%) and Usha Kannan et al. [10] (20%), but higher than those found by Vasudha T K et al. [11] (6%), Vandana and Sudha [12] (4.5%), and Pragna et al. [13] (6.25%). Cases of a completely absent suprascapular notch have also been documented by Ofusori et al. [15] in a Nigerian scapula and by Rekha B S [16] in an Indian scapula during a routine dissection. Although it has been suggested that a narrow, V-shaped suprascapular notch may increase the likelihood of suprascapular nerve entrapment, clinical studies have not found a direct correlation between notch type and nerve entrapment [17]. However, many authors have reported that variations in the morphology of the superior transverse scapular ligament, such as ossification [2], calcification [18], bifurcation [19], trifurcation [20], and/or hypertrophy [21], are associated with suprascapular nerve entrapment neuropathy. Among these factors, the complete absence of the suprascapular notch, along with morphological variations in the superior transverse scapular ligament, may also predispose individuals to suprascapular nerve entrapment neuropathy [5,6,15]. The suprascapular nerve originates from the lateral aspect of the superior trunk of the brachial plexus, receiving contributions from the 5th and 6th cervical roots, and occasionally from the 4th root as well. The nerve travels downward to reach the upper border of the scapula, where it enters the supraspinatus fossa through the suprascapular notch, passing beneath the superior transverse scapular ligament (STSL), with the suprascapular vessels lying above the ligament. The nerve continues obliquely along the floor of the supraspinatus fossa under the supraspinatus muscle, supplying it, and also providing sensory branches to the glenohumeral and acromioclavicular joints. It then makes a sharp turn around the lateral margin of the base of the scapular spine (spinoglenoid notch) with the suprascapular vessels passing below a spinoglenoid (or inferior transverse scapular) ligament, if present, to enter the infraspinatus fossa, where it innervates the infraspinatus muscle [3,22,23]. Suprascapular nerve entrapment can occur at any point along its course, but in cases where the suprascapular notch is absent, the nerve may be compressed by the superior transverse scapular ligament at the superior border of the scapula [5,6,15]. This compression can be especially severe when the ligament is ossified [2]. Patients with suprascapular nerve entrapment neuropathy typically experience deep, diffuse, and poorly localized dull or burning pain in the posterolateral aspect of the shoulder, which worsens with activity. This pain can often be elicited by palpation over the area of the scapular notch. In some cases, the pain may radiate to the affected extremity, the side of the neck, or the front of the chest. Patients may also report weakness in the affected shoulder, particularly during overhead activities, due to the weakness and atrophy of the supraspinatus and infraspinatus muscles resulting from the nerve's denervation [22,23,24].

Diagnostic investigations such as nerve conduction velocity (NCV) and electromyographic (EMG) studies, along with imaging techniques like X-ray, CT, MRI, and arthrography, can be useful in confirming the diagnosis. Electrophysiological studies and MRI are especially important when clinical findings suggest suprascapular nerve entrapment, as MRI can also reveal associated conditions like rotator cuff tears [23,24].

Table 2:  Comparative statement of Incidence of the absence of a suprascapular notch in the different populations studied by different authors.

Table 3:  Comparative statement of Incidence of the absence of a suprascapular notch in the Indian population by different authors.

Limitations of the study: One limitation of this study is that we were unable to consider the age and sex of the scapulae, as this information was not available. Additionally, the study was conducted with a limited number of dry scapulae. To gain a more comprehensive understanding, further research involving larger samples, as well as clinical, radiological, and cadaveric studies, is necessary.

This study highlights that the incidence of a completely absent suprascapular notch can vary across different populations and may be a potential risk factor for suprascapular nerve entrapment neuropathy. Understanding this anatomical variation is crucial for surgeons and clinicians, especially during surgical or arthroscopic shoulder procedures, as it can help prevent inadvertent injury to the suprascapular nerve.

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