The most common dislocation of the human body is the shoulder joint. The shoulder joint dislocates in anterior direction for as much as 95% in patients with shoulder dislocation.
Cases of shoulder joint dislocation commonly present with severe pain and poor range of motion at the shoulder in addition to dislocation of the joint.
It is essential to perform neurovascular examination and document the findings at the time of presentation and after reduction of the anomaly, both, in order to look for axillary nerve injury, since it occurs in almost 40% of the cases.
X-ray films, antero-posterior and lateral with/without axillary view are sufficient in most cases to reach a diagnosis. The outline of the glenoid fossa and the humeral head are incongruent in X-rays for anterior dislocation and also inferior dislocation of the shoulder. Posterior dislocations are challenging to identify on antero-posterior view since the congruency does not appear to be disrupted, as the head of humerus moved directly to the posterior position. It can be easily diagnosed using the axillary/ trans-scapular Y view, where the malalignment of the humerus is clearly visualized. Therefore, it is recommended that the trans-scapular Y view should be ordered routinely in all cases with suspected shoulder joint dislocation.
Additional diagnostic tests include:
All acute cases of shoulder dislocation require immediate reduction of the joint   . The goal of reduction is relaxation of shoulder muscles. Once the appropriate direction of the anomaly has been determined, conscious sedation or an intra-articular analgesic may be administered prior to the reduction procedure. In order to verify the reduction, radiographs must be obtained after the procedure has been completed. Methods to achieve reduction include:
There should be limited use of physical therapy in an acute case. One to three weeks of sling immobilization and swathing of the arm in externally rotated position is advised, as it is thought to the benefit the torn soft tissues    . The movement of fingers, hand, elbow and wrist of the arm in sling, along with the movement of parascapular muscles should be encouraged to begin early rehabilitation, and must be continued after the sling has been discontinued.
Surgery must be considered in all cases presenting with recurrent instability of the shoulder joint   . The operative intervention aims at reattachment of the torn tissues to their site of attachment at the bone. The most common site for a tear in the ligament is at the glenoid. Ligaments may get stretched secondary to recurrent shoulder dislocations, therefore making it necessary to correct any laxity in the tissues intra-operatively. The procedure is usually performed by arthroscopy, but an open incision may also be used.
It is commonly managed by closed reduction under conscious sedation or intra-articular block. The following techniques can be used for reduction:
Posterior dislocation is usually reduced by longitudinal traction.
Reduction of the joint is achieved by applying traction-countertraction to the abducted arm. A closed reduction will not be successful if the head of humerus is trapped within a torn inferior capsule (also called as buttonhole deformity), and such circumstances will warrant an open reduction.
Dislocation is mostly managed with relocation. If the duration between dislocation and relocation is short, the risk of complications will be less. The next step in treatment is immobilization of the joint for 7-10 days in patients older than 30 years and 3 weeks for patients less than 30 years. This period should involve keeping the joints of the arm, wrist and fingers active to maintain range of motion .
Young patients may benefit from early intervention with arthroscopy, labral repair and debridement, since cases of a younger age group with anterior dislocation of the shoulder joint have a recurrence rate of 85% . There is limited evidence supporting primary surgical correction for young adults that engage in intensive physical activities, but none for other age groups or types of injuries.
The age of the patient is considered as the most significant factor to assess the risk for re-dislocation of the shoulder joint. The risk is higher for individuals that sustained the first dislocation of the shoulder at a younger age, with the rate of recurrence being almost 90% in cases that had the first dislocation in teenage. The rate of recurrence falls to 10-15% in cases forty years old and older. The re-dislocation frequently occurs with a period of two years of the first dislocation.
Although the arthroscopic procedure for the repair of shoulder dislocation, called the Bankart repair (ABR), is an effective modality, re-injuring the same joint with the arm in 90° elevation and 90° external rotation within a year of the procedure was found to be a major risk factor for re-dislocation. It was also found that having less than four suture anchors and large Hill Sachs lesions considerably increased the risk for a re-dislocation after the procedure.
In patients with anterior dislocation of the shoulder, a primary non-operative treatment is usually followed by recurring deficits in the function of the joint. Young males have been found to have the greatest risk for joint instability while females have a considerably lower risk. Clinical trials, using novel tools to determine the prevalence of functional deficits and recurring instability in shoulder joint, may be considered for a follow-up period of two years after primary dislocation of the joint.
The axillary nerve is frequently injured in association with dislocation of the shoulder joint. It courses inferior to the head of humerus and distally wraps around the surgical neck of humerus. If injured, a complete recovery of the nerve injury occurs within 3-6 months after resolution of the joint dislocation.
The shoulder joint is stabilized by the rotator cuff muscles, glenohumeral ligaments, negative intra-articular pressure, joint capsule and the bony/cartilaginous anatomy. Although there are multiple ligaments that contribute to the stabilization of the shoulder joint, the most significant of all is the inferior glenohumeral ligament. It is commonly injured when the shoulder dislocates anteriorly. Typically, there is a stretch injury of the capsule/ligament and/or tearing of the capsule/ligament where it attaches to the bone.
During sports activities, the shoulder joint is quite often in an unusual position such as abduction and external rotation. This makes the ligaments vulnerable to injury from a fall or direct impact on the shoulder. Depending upon the strength of the force, there can be a fracture of the humerus or glenoid and/or the tendons/ligaments may get torn, leading to dislocation of the shoulder joint.
Major traumatic episodes are responsible for 95% cases of shoulder dislocation. In order to identify the etiology of dislocation, the severity and type of trauma has to be precisely determined. This in-turn is necessary for initiating appropriate treatment     .
95% cases of shoulder dislocation have anterior displacement of the joint. It occurs by abduction and external rotation along with trauma to surrounding structures, such as rotator cuff tear (especially in elderly), injury to the brachial plexus, greater tuberosity fracture and injury to the axillary nerve. Individuals less than 30 years of age commonly have shoulder joint instability, thus predisposing them to recurrent dislocation of the joint.
Posterior dislocations are frequently missed. The most common causes for posterior dislocation of the shoulder joint include electro-convulsive therapy (if performed without concurrent use of muscle relaxants), electric shock or seizures. The deformity due to this dislocation may not be apparent. The patient presents with the arm held in adduction and internal rotation, and passive external rotation is not possible upon flexion of the elbow. If the latter sign is present, an antero-posterior X-Ray of the shoulder must be ordered.
Inferior dislocations/Luxatio erecta
This is the rarest of the three types of shoulder dislocations. Inferior dislocation may result from a forced hyperabduction . The patient presents with the arm held above the head, often resting on it, with almost 180 degrees abduction. On physical examination, the head of the humerus is palpable in the axilla, the arm appears shortened, the rotator cuff may be torn and the joint capsule may be disrupted. Injury to the brachial artery is found in less than 5% of cases. Nerve injury, often involving the axillary nerve, is usually present but resolve spontaneously after reducing the joint.
As we look at the numeric data for cases with dislocation of a major joint, shoulder joint dislocations contribute close to half of this number     . 95-97% of cases present with anterior dislocation of the shoulder joint, another 2-4% with posterior dislocation, and approximately 0.5% with inferior dislocation .
The most frequently dislocated joint in human body is the shoulder joint   . The majority of cases have anterior dislocation, but a small fraction of cases also present with posterior, inferior and antero-superior dislocation of the shoulder. Cases with a history of shoulder dislocation are at a greater risk for another dislocation. This may be attributed to tissue laxity and/or poor healing. Other factors include concurrent tearing of the rotator cuff, glenoid fracture and advanced age of the patient.
Patients in their twenties and teenagers have a greater frequency of sustaining shoulder re-dislocation as compared to individuals aged fifties to sixties , which may be secondary to a higher activity level in the former group. These findings suggest that age may not be a significant risk factor for re-dislocation of the shoulder joint.
The shoulder joint is very mobile. It is stabilized by the rotator cuff muscles, glenohumeral joint capsule and the glenoid labrum. Shoulder joint instability can also occur due to tearing of the rotator cuff muscles, namely supraspinatus, infraspinatus, teres minor and subcapsularis. These muscles are located on the top of shoulder joint bones and the glenohumeral ligaments. Shoulder joint instability can occur due to large rotator cuff tears, even if the glenohumeral ligaments are intact. The joint can also become unstable if the nerves (especially the axillary nerve) innervating the shoulder muscles are injured.
Atraumatic dislocation of the shoulder joint can occur due to several reasons. Laxity of the ligaments in the shoulder joint may lead to atraumatic dislocation. Although the ligament laxity is bilateral, these patients may present with unilateral symptoms. Excessive retroversion of the humeral head and glenoid malformation are congenital deformities that can cause shoulder joint instability. Axillary nerve injury and cerebral palsy have also been associated with instability of the shoulder joint.
The bio-mechanical forces that can lead to dislocation of the shoulder include :
In order to avoid sustaining a dislocation of the shoulder, patients must refrain from immediate participation in strenuous sports activities. Any activity that puts the arm in abduction and external rotation, like combing of hair, must also be avoided.
Patients with dislocation of the shoulder joint account for almost half of the case number for all major joint dislocations. The dislocation of the shoulder joint may occur due to capsular ligament laxity or trauma to the joint. Various conditions may influence the joint stability and may lead to poor outcome in cases with dislocation of the shoulder joint .
The types of shoulder joint location are:
The most common dislocation of the three types is anterior shoulder dislocation and is the result of forced abduction, external rotation and extension .
Half of all cases with major joint dislocations are those with shoulder joint dislocation. Almost 95-97% patients with shoulder dislocation have anterior dislocation of the joint another 2-4% have posterior dislocation and rarely, inferior dislocation. The shoulder joint is has a wide range of motion and therefore is relatively less stable and more prone to dislocation. Anterior dislocation of the shoulder is treated by performing maneuvers, followed by approximately six weeks of immobilization to allow healing of the structures that form the joint. A good physical therapy is the key to achieving normal function of the joint after injury. Isometric exercises are emphasized during the physical therapy, in order to allow sufficient rest to the glenohumeral joint for faster healing. Early surgical intervention may benefit younger patients who sustained anterior dislocation of the shoulder, since their chances of sustaining shoulder dislocation again are very high.