GLENOID CAVITY: CHARACTERISTICS, FUNCTION, PATHOLOGIES, DISORDERS - ANATOMY AND PHYSIOLOGY - 2025

The glenoid cavity is a concavity of the shoulder blade or scapula. The head of the humerus fits perfectly into it, forming the glenohumeral joint or also called the scapulohumeral joint. This joint is also known as the first shoulder joint.

This joint is very unstable and, therefore, the function of the deltoid muscle is to lift the humeral head towards the acromion, while the supraspinatus muscle does not allow the head of the humerus to leave the glenoid cavity.

Graphic representation of the glenoid cavity of the scapula. Source: Henry Vandyke Carter / Henry Vandyke Carter Edited image.

In turn, in the middle arches of movement of the shoulder, the rotator cuff acts as a dynamic stabilizer, which is responsible for pushing the humeral head against the glenoid cavity.

In the same way, the movements of the shoulder above 60 ° and in the rotation, the joint is stabilized by the inferior glenohumeral complex. This complex is formed by the joint capsule in conjunction with the inferior glenohumeral ligament.

Among the pathologies that involve the glenoid cavity are: the instability of the shoulder whose cause is multifactorial, the arthrosis of the glenohumeral joint, fracture of the glenoid cavity and the Bankart lesion, among others.

characteristics

The glenoid cavity is a shallow concavity, pear-shaped, being longer than it is wide, with a broader base.

According to Romero and collaborators, the average measurement of the glenoid cavity in the cephalo-caudal area is 3.70 cm and the antero-posterior diameter is approximately 2.71 cm.

These data coincide with those obtained by Kose et al in 2018, who evaluated 100 patients, whose average of the cephalo-caudal area was 38.15 mm for the dominant side and 37.87 mm for the non-dominant side, while that the anteroposterior diameter was 28.60 mm for the dominant side and 28.00 mm for the non-dominant side.

This means that both glenoid cavities are not the same, with significant differences between them.

This information can be very useful in total shoulder prosthetic replacements, especially in correcting the current problems of loosening of the glenoid prosthetic device and the associated glenohumeral instability.

On the other hand, the glenoid cavity has a ring of fibrocartilaginous tissue called the labrum or glenoid rim. The labrum, together with the joint capsule and the glenohumeral ligaments, is called the capsulolabral complex. It allows the concavity to be a little deeper, thus providing stability to the glenohumeral joint.

The shallow depth of the glenoid cavity gives it an advantage over the rest of the joints, since it allows the shoulder to have a fairly wide range of motion, being the joint that has the greatest capacity for movement. However, this same characteristic provides a disadvantage, since it makes it more vulnerable to suffering dislocations.

Function

Its main function is to permanently receive and accommodate the head of the humerus, offering it the ability to move. Therefore, it is not a static relationship, but on the contrary, it is very dynamic.

It also serves as an insertion point for certain muscles, such as: the long head of the biceps is fixed on the upper edge of the glenoid cavity and the long head of the triceps that rests on the lower edge of the same socket.

Related pathology or disorder

- Instability of the glenohumeral joint

The instability of the glenohumeral joint can be caused by: lesion in the capsulolabral complex, excessive gleno anteversion or capsular hypermobility. On the other hand, there are studies that show that there are anatomical factors that can influence to increase the predisposition to have an unstable shoulder.

The anatomical parameters that are relevant in this regard are: the horizontal glenohumeral index, the glenoid inclination and the angle of anteversion of the scapula.

Glenohumeral joint instability can begin with a subluxation and end with a complete dislocation. This involvement is very common, representing 95% of all dislocations, being more common in men than in women.

It should be noted that an unstable shoulder causes pain, limiting certain movements.

Treatment

Treatment for glenoid cavity instability 100% surgical, as long as the number of dislocations is above three episodes.

The options are, the placement of special prostheses or the osteosynthesis or reconstruction of the fractures of the glenoid cavity.

Physical exploration

To detect instability of the glenohumeral joint, several tests can be performed on the patient:

Test

It is a rather uncomfortable test for the patient. An attempt is made to place the arm abducted at 90 °, while inducing external rotation in retropulsion.

The patient's feeling under this action is that the shoulder will be dislocated, that is, he feels that the head of the humerus is going to come out of the glenoid cavity and of course he resists this movement.

Relocation test

With the patient lying on his back, leaving the shoulder to be examined off the table, the patient's arm is placed in external rotation and 90 ° abduction. From this position we place the hand behind the patient's shoulder and, as the rotation is increased, the shoulder is pushed forward.

The moment the patient complains of pain, the opposite shoulder is pushed, that is, backwards. If this action causes the pain to be minimized or disappear, it is considered a positive test for glenohumeral instability.

Ant / post drawer

This test assesses anteroposterior laxity. With the patient seated, the patient is asked to fully extend the arm to the side of the body, then the shoulder is stabilized and, very carefully, an attempt is made to move the head of the humerus backwards and subsequently forwards.

The professional who performs the exam will be able to detect whether the movement of the shoulder is normal or abnormal.

Sulcust test

Evaluates inferior instability of the glenohumeral joint. For this test the patient must be seated. You are asked to extend your arm to the side of your body and then to flex your elbow.

Starting from this position, a downward pull is performed. If it is possible to detect a depression below the acromion, it is a sign that there is a lesion of the rotator interval, and in this case the test is considered positive.

Imaging scan

All imaging studies are valuable and each provides useful information, that is, they are complementary.

In this sense, radiology and Computerized Axial Tomography (CT) or arthro CT, offer precise information on bone lesions and guide towards the type of surgical treatment to follow.

Meanwhile, magnetic resonance imaging is useful to study soft tissues, as for example in the case of a tear in the fibrocartilaginous tissue (labrum).

- Osteoarthritis of the glenohumeral joint

It is usually the result of a fracture. It begins with a non-surgical treatment and if it does not resolve, you should go to surgery. These pre-surgical options include arthrodesis or total or inverted prosthesis.

- Glenoid cavity fracture

They are caused by trauma. This type of fracture requires surgical intervention, given its complexity. Idelberg classifies glenoid fractures into six categories according to the characteristics of the injury, such as extension of the fracture, structures involved or orientation of the fracture, among others.

- Bankart injury

The Bankart lesion is characterized by damage to the connective tissue that surrounds the glenoid cavity, which, as mentioned above, is called the labrum or glenoid ridge.

It usually occurs after trauma, such as a shoulder dislocation. It is also possible to tear from repetitive movements during sport. Tearing of the glenoid rim causes instability in the joint.

In this situation, the patient feels that the shoulder is going to slip out of place, in fact, it is possible. Also, the patient feels pain when moving the shoulder. In these cases, MRI is ideal for making the diagnosis.

In mild injuries it is possible to treat with physiotherapy, but in more severe cases surgery is necessary.

References

1. "Glenoid cavity (scapula)". Wikipedia, The Free Encyclopedia. 23 Sep 2017, 16:19 UTC. 6 Oct 2019, 22:52
2. Romero R, Alliegro E, Bautista D. Morphometry of the glenoid cavity of the scapula. Gac Méd Caracas 2015; 123 (4): 287-291. Available at: researchgate.net
3. García-Mata S, Hidalgo Ovejero A. Glenohumeral osteometry-scapulometry in recurrent anterior shoulder instabilities: etiopathogenic study of one of the static stabilizers using computed tomography. Anales Sis San Navarra 2 011; 34 (2): 175-191. Available at: scielo.isciii.es
4. Zamorano C, Muñoz S, Paolinelli P. Glenohumeral instability: what the radiologist should know. Rev. chil. radiol; 15 (3): 128-140. Available at: scielo.conicyt.cl
5. Kose O, Canbora K, Koseoglu H, Kilicoglu G, Turan A, Yuksel Y et al. Can We Use the Contralateral Glenoid Cavity as a Reference for the Measurement of Glenoid Cavity Bone Loss in Anterior Shoulder Instability ?. A Comparative Analysis of 3D CT Measurements in Healthy Subjects. Int. J. Morphol. 2018; 36 (4): 1202-1205. Available at: scielo.conicyt.