Acute Acromioclavicular Dislocation: Epidemiology, Natural History and Analysis of Prognostic Factors

Introduction:

Acromioclavicular (AC) joint dislocations are common injuries accounting for 9-12% of all injuries to the shoulder girdle. The injuries are graded according to Rockwoods classification type I-VI. There is consensus on the treatment of Rockwood type I and II which rehabilitates well with conservative treatment, and for high-grade injuries of types IV, V and VI, which usually requires surgery. However the treatment of the most common type, type III, has remained controversial for the last 30 years. To assess this problem, ISAKOS (International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine) Upper Extremity Committee in 2014 provided a modified Rockwood classification, suggesting a sub-classification of the debated type III in a stable type IIIA and an unstable type IIIB.

The purpose of this sub-classification is to identify and differentiate patients, who are expected to rehabilitate well with conservative treatment from those who would benefit from early surgical intervention, i.e. type IIIA and IIIB. Type IIIA is considered stable and is characterized by absence of scapula dyskinesia and no overriding of the clavicle to acromion. Type IIIB is characterized by presence of scapula dyskinesia and no overriding of the clavicle to acromion.

Aim:

To evaluate non-operative treatment of acute acromioclavicular (AC) joint dislocation and define prognostic factors to guide the choice of treatment in order to develop an individualized treatment algorithm.

Objectives:

1. To investigate whether a sub classification of Rockwoods type III in a stable type IIIA and an unstable type IIIB, as suggested by ISAKOS, is clinically relevant. Clinically relevant is defined as a difference in the WOSI score of >14%
2. To evaluate clinical, functional and radiological results, along with patient-reported health, 6 weeks, 3 months, 6 months and 1 year after acute AC dislocation
3. To investigate whether specific factors are of prognostic value to the result after non-operative management of acute AC dislocation
4. To investigate if Rockwoods classification of AC dislocations is of prognostic value for the rehabilitation after the injury.

Study design: The study is carried out as a prospective cohort study. 100 patients will be included.

Time schedule:

Recruitment of patients for the study is planned to begin in November 2018. It is expected that the inclusion will span 1 year, provided an average of 2 patients included per week. With a 1-year follow-up for each patient the total study period is expected to be 2 years.

Methods:

Recruitment:

100 patients with acute AC-joint dislocation from the Emergency Departments at three different hospitals in the Capital Region of Denmark (Hvidovre, Glostrup and Amager hospitals) will be included in the cohort. Patients with superior displacement of the clavicle to the acromion are of interest to the study.

At the Emergency Departments, the patients will receive the standard conservative treatment of collar'n cuff for 1-3 weeks.

To identify patients, all X-rays of the AC-joint and the clavicle obtained at the three hospitals will be evaluated weekly, identifying the presence and degree of potential AC dislocations. If the patient meet the inclusion criterias, he or she will be invited to participate in the cohort.

Follow-up:

Participants will be offered an appointment in the ambulatory for baseline evaluation. Follow-up measurements will be performed at 6 weeks, 3 months, 6 months and 1 year after the injury. The study's primary endpoint is at the 3 month mark.

At the follow-ups, participants will be evaluated clinically, functionally and radiologically. Primary outcome measure is the patient's self-reported shoulder-related quality of life, evaluated using WOSI (Western Ontario Shoulder Instability Index). As secondary outcomes patients will evaluate their functional limitations and pain with SPADI (Shoulder Pain and Disability Index), the cosmetic results with NRS (Numeric Rating Scale) and attend a clinical evaluation regarding range of motion (ROM), the presence of scapular dyskinesia, antero-posterior/superior-inferior instability of the clavicle and O'Briens test. Two radiographs of the AC-joint will be obtained to determine the coraco-clavicular distance as well as the degree of overriding of the clavicle to acromion.

It is expected that a number of patients in the cohort, due to sustainable pain and non-acceptable disability, will be offered surgical treatment. This group will be followed exactly like the group of conservatively treated patients. The two groups will be compared both according to their demographical data and their outcome.

Discontinuation:

Each patient can choose to withdraw from the trial at any time. A patient may also be withdrawn from the trial at any time based on the investigators' discretion.

Data Registration:

All relevant data is recorded and stored in a specially designed database; RedCap. The data registration has been approved by the Danish Data Protection Agency and The Ethical committee of the Capital Region of Denmark.

Statistics:

The cohort will be described descriptively regarding demographic parameters as well as primary and secondary outcomes. The change of the outcomes over time will be described using relevant statistics according to the characteristics of the variables and if necessary the normal distribution. A regression analysis will be used to evaluate the association between prognostic factors and recovery.

Sample size:

The sample size is calculated to detect if a clinical relevant difference in WOSI-score exists between a group with stable (type IIIA) and unstable (type IIIB) AC dislocations. The calculation is based on a clinical relevant difference in WOSI-score of 14%, a standard deviation, SD, of 20%, a significance level of 0,05 and a power of 90%. According to this calculation the study demands 88 patients but because of the risk of drop-out, 100 patients will be included.

Ethical considerations:

The project is approved by the National Committee on Health Research Ethics. The purpose of the study is to follow the natural history of a common injury, where guidelines for the treatment already exist. There is no intervention in the study - patients enrolled will receive the standard treatment in the Emergency Departments. They will be offered standardized physiotherapy and extra controls, which is considered an advantage for the patients as they receive a thorough follow-up and examination of the healing process. The disadvantages for the patients are: 1) Participation in the study is time-consuming: Patients need to attend 4 extra controls, each lasting approximately 1h. 2) Exposure to radiation: At each control, 2 x-rays of the shoulder will be obtained. However the radiation exposure is very small, only 0,1-0,3 mSv/ x-ray, equivalent to a few weeks of background radiation. It is believed that the potential benefits for both patients in the study and future patients with AC dislocations (thorough follow-up and individualized treatment,) exceed the the potential inconveniences (additional follow-up audits and light exposure to radiation).