The goal of this prospective observational cohort study is to provide epidemiological and prognostic data from a defined urban population and to improve understanding of risk factors and long-term outcomes following first-time anterior shoulder dislocation in patients aged 16 years and older presenting to the Oslo Accident and Emergency Outpatient Clinic.

The main questions the study aims to answer are:

• What is the incidence of first-time anterior shoulder dislocations in the Oslo region?
• What is the prevalence and extent of bipolar bone loss and soft tissue injuries measured by CT and MR after a first-time shoulder dislocation?
• Does bone loss increase the risk of recurrent shoulder instability?
• How do imaging findings and recurrence influence long-term shoulder function and quality of life?

Participants will:

• Undergo standard clinical evaluation and conventional radiographs as part of routine care and asked to participate and followed longitudinally
• Be offered additional CT and MRI imaging to assess glenoid and humeral bone loss and to evaluate soft tissue injuries.
• Complete electronic questionnaires (WOSI, EQ-5D-5L, pain score, Rowe score, return to sport/work) at 3 months, 1 year, 5 years, and 10 years.
• Be invited to long-term follow-up, including radiographs at 10 years to evaluate signs of osteoarthritis.

Traumatic anterior shoulder dislocation is a common injury, particularly among young and active individuals. Recurrence after a first-time anterior dislocation is frequent and varies substantially depending on age, activity level, and structural injury. Established risk factors include young age, male sex, hyperlaxity, participation in contact or overhead sports and concomitant bony or soft tissue injury. Despite the high recurrence risk in selected patient groups, most first-time dislocators are treated non-operatively in current Norwegian practice.

Subtle bony defects may be underdiagnosed on plain radiographs. Approximately one-third of patients sustain a bony Bankart lesion, and more than 70% present with a Hill-Sachs lesion. The size and location of the Hill-Sachs lesion, as well as its on-track/off-track classification, have implications for treatment strategy. CT with three-dimensional reconstruction is considered the most reliable method for assessing glenoid and humeral bone loss, while MRI enables detailed evaluation of associated soft tissue injuries, including labral and capsuloligamentous lesions.

The SALTO study is a prospective observational cohort including all eligible patients aged ≥16 years presenting with first-time anterior shoulder dislocation at a defined urban emergency clinic. The study will systematically assess bone loss using CT and characterize soft tissue injuries using MRI. Patients will be followed longitudinally with clinical data and patient-reported outcome measures to evaluate recurrence, shoulder function, and long-term shoulder function.

By correlating imaging findings with recurrent instability and long-term outcomes, the study aims to improve risk stratification after first-time anterior shoulder dislocation and identify patients who may benefit from early surgical intervention.

Inclusion Criteria

• Age ≥16 years
• Diagnosis of first-time traumatic anterior shoulder dislocation
• Resident in the Oslo region who presents to Oslo Accident and Emergency Outpatient Clinic for treatment or follow-up within two weeks after initial injury
• Ability to provide informed consent

Exclusion Criteria

• Previous shoulder dislocation requiring reduction (Patients uncertain about prior dislocation are excluded)
• Age < 16 years
• Chronic substance abuse affecting compliance
• Inability to understand Norwegian or English
• Adult not able to provide consent or severe medical or psychiatric condition precluding follow-up

All eligible patients presenting with first-time anterior shoulder dislocation at Oslo Accident and Emergency Outpatient Clinic (Oslo University Hospital, OUS) during the inclusion period will be asked to participate.

Individual participant data are stored in a secure research database (TSD, University of Oslo) containing sensitive health information. De-identified data may be considered for sharing with other researchers upon reasonable request and subject to approval by the data protection authorities and the study investigators.