Epidemiology

The glenohumeral joint is the most mobile joint in the body, making it particularly vulnerable to dislocation.[5] Anterior shoulder dislocations account for more than 95% of shoulder dislocations and are the most common major joint dislocation.[6] Posterior shoulder dislocations occur in 2% to 4% of cases, and inferior (i.e., luxatio erecta) dislocations in approximately 5% of cases. The incidence of shoulder dislocations has bi-modal peaks, the first in men between adolescence and 30 years, and the second in women aged 61-80 years.[7][8]

Studies have estimated the incidence of shoulder dislocation to be 23.9 per 100,000 person-years in the general population, with rates as high as 169 per 100,000 person-years among young, active, and military populations.[5]

Between 2012 and 2021, males aged 15-20 years represented the highest proportion of shoulder dislocations presenting to US emergency departments, predominantly resulting from participation in sports. Women experienced a relatively consistent incidence of dislocation throughout their lifespan. Women accounted for less than one third of shoulder dislocations presenting to emergency departments, but after age 63, the incidence rate of dislocations in women surpassed that observed in men. This discrepancy is poorly understood, but may be due to biological differences between men and women as they age, such as muscle bulk and tendon strength, as well as differences in the rate of falls between the sexes.[5]

There is a low incidence of shoulder dislocation in the paediatric population, with one study in Italy reporting an incidence of 0.3 per 100,000 inhabitants younger than 14 years; this may be explained by skeletal immaturity, because the mechanisms of injury generally associated with dislocation are more likely to cause proximal humerus fractures or physeal injury in patients whose physis has not yet closed.[5][9]

Dislocations of the finger joints are common hand injuries with the proximal interphalangeal joint being the most frequently affected site. The incidence rate of finger dislocations presenting to US emergency departments was 11.1 per 100,000 person-years between 2004 and 2008.[10] Males were predominantly affected (78.7%) at an incidence rate of 17.8 per 100,000 person-years. Most dislocations occurred in the 15- to 19-year age group (38.6 dislocations per 100,000 person-years) and 35.9% of cases took place at a sporting or recreational facility. Black males were found to be particularly at risk, as were basketball and football players. The rate in females was 4.65 per 100,000 person-years.

Acute patellar dislocation accounts for 2% to 3% of all knee injuries and is the second most common cause of traumatic knee haemarthrosis.[11] First-time lateral patellar dislocation has an incidence of approximately 23 per 100,000 person-years.[12] Two-thirds of patellar dislocations involve sports-related mechanisms and incidence rates are higher in young, physically active cohorts; in a study of young military personnel in Germany, the incidence of acute traumatic primary dislocation of the patella was estimated to be 77 per 100,000 people per year.[13][14] In the non-athletic population, women aged 10-17 years are more likely to have patellar dislocations. Women are also more likely to have a prior history of patellar instability and recurrent dislocation.[15] In addition, patients with a history of patellar instability and recurrent dislocation are more likely to have contralateral injuries.[16]

The elbow joint is the second most commonly dislocated large joint after the shoulder.[17] The estimated incidence of elbow dislocations in the US population is 5.21 per 100,000 person-years with 44.5% of dislocations being sustained during sports.[18] Adolescent boys are at the highest risk for elbow dislocation (8.91 per 100,000 person-years in boys aged 10-19 years).[17] Males tend to sustain this injury while participating in football, wrestling, and basketball, whereas gymnastics and skating activities are more likely in females.[18] With the rise in popularity of snowboarding, there has been an increase in elbow injuries. Elbow dislocations are significantly more common in snowboarders than skiers; 26% of elbow injuries in snowboarders are dislocations, compared with 5.3% in skiers.[17] Most elbow dislocations (80% to 90%) are posterior or posterolateral.[19]

Hip dislocations are high-energy injuries that are relatively uncommon.[4] They overwhelmingly occur in high-energy motor vehicle accidents. It is estimated that sports-related hip dislocations may account for 2% to 5% of all traumatic hip dislocations.[20] It should be noted that dislocation of a total hip arthroplasty, compared with dislocation of an otherwise normal hip, is usually a low-energy event with the patient flexing and internally rotating the hip.

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