Surgical Treatment of Recurrent Shoulder Dislocations

The glenohumeral joint has the greatest range of motion of any major articulation in the human body. This increased mobility leaves the joint vulnerable to dislocation and the development of instability and osteoarthritis, both of which can have drastic effects on work productivity and quality of life. Symptomatic instability following anterior glenohumeral dislocation is especially common among young people. In patients under 20 years of age, recurrent dislocation rates may be as high as 90%. The high incidence of recurrent dislocation negatively affects the individual and society in general. It may limit range of movement and can require multiple hospital visits for treatment and surgical procedures to prevent further dislocations. Chronic instability of the joint may prevent the individual from participating in sports and physical activity, and from returning to work, and leads to osteoarthritis. The development of osteoarthritis in young patients is devastating and leads to changes within the shoulder that are not easily repairable and results in the need for early shoulder replacements which are costly for both the healthcare system and for the patient themselves. It has been well-established in the literature that surgical management of anterior shoulder instability provides a lower recurrence rate and better rates of return to sport than non-operative treatment. Non-operative treatment of primary anterior shoulder instability has been found to have a high rate of progression to arthritis at a long term follow-up, due to recurrence.

Recurrence rates are influenced by multiple factors including age and gender of the patient, contact sport participation, ligamentous laxity, and the bone loss both on the glenoid and humerus. Of these factors, bone loss is the only modifiable factor. Glenoid defects, present in 22% of patients with acute dislocations, are found in 73% of recurrent dislocations. The management of glenoid bone deficiency in shoulder instability has been a challenge to surgeons for many years. Anteroinferior glenoid bone loss is a significant contributor to recurrent instability through alteration of both the glenohumeral joint contact area and congruency of the articular surfaces. Previous researchers outlined the additive effect of humeral and glenoid bone loss in contributing to shoulder instability and stressed the importance of bony procedures in creating a stable shoulder, particularly for the young active patient. For patients with large anterior glenoid defects (>25%) or other risk factors for recurrence, bone grafting procedures, including autogenous coracoid transfer to the anterior glenoid (i.e. Latarjet procedure) as well as iliac crest autograft and tibial allografts (i.e. arthroscopic anatomic glenoid reconstruction (AAGR)) have been described. These procedures have all been shown to be equally effective and reliable techniques for treating shoulder instability.

The most common pathology in recurrent shoulder instability is anteroinferior capsulolabral avulsion. In 1938, Bankart described the detachment of the anterior inferior labrum from the glenoid rim as a cause of anterior instability and presented his case report of 27 patients treated surgically. In recent years, technical advancements in arthroscopic shoulder surgery have radically altered the treatment of anterior shoulder instability. Arthroscopic techniques have been developed in an attempt to reduce common challenges of open repair including wide dissection, loss of external rotation and post-operative pain. Arthroscopic labral repair, now considered routine and reliable, is the treatment of choice for many cases of recurrent anterior shoulder instability in North America.

Although the results of arthroscopic anterior labral repair using current techniques have been shown to parallel results of open anterior stabilizations in most patients, it is recognized that arthroscopic labral repair is less effective in patients with risk factors for failure such as young age, hyperlaxity, competitive contact sport participation, and in particular glenoid or humeral bone loss. A recently published long-term study on patient outcomes following isolated arthroscopic Bankart repair found a high rate of recurrence and development of arthritis at a 9-12- year follow-up. The authors state that an isolated Bankart repair does not solve the issue of glenoid bone loss.

While bony procedures have traditionally been reserved for cases with bone loss of the glenoid or humerus (so-called Hill-Sachs lesions), there are some regions in which surgeons prefer this type of procedure regardless of the degree of bone loss. This is in part due to recent findings revealing that bone loss may be underestimated by current methods of preoperative measurement. Currently, there are three common methods used to assess bone loss. Preoperative CT and MRI are employed to quantify bone defects, and arthroscopic evaluation may also be used.

There is much controversy over the most accurate method of quantifying bone loss. CT evaluation of glenoid bone loss pre-operatively has been shown to underestimate bone loss.. The absence of a validated non-invasive pre-operative imaging modality has led many surgeons to utilize bony procedures more aggressively, despite limited findings of bone loss on pre-operative imaging. One survey revealed that, irrespective of the types of patients and lesions, 72% of French shoulder surgeons prefer bone block procedures for treating traumatic recurrent anterior shoulder instability. This is in stark contrast to the findings of a large international survey, in which 90% of shoulder surgeons in other countries preferred arthroscopic Bankart repair. Rates of recurrence after these two techniques vary widely in the literature, ranging from 0% to 30% for arthroscopic Bankart repair, with a mean of 9%, and from 2% to 14% for the open Latarjet bone block procedure, with a mean of 7%.

In recent years, trends toward minimally invasive shoulder surgery along with improvements in technology and technique have led surgeons to expand the application of arthroscopic treatment. Techniques have been developed to treat severe instability with or without associated bone loss using arthroscopic bone allograft and autograft augmentation. These approaches seek to provide a nearly anatomic reconstruction of the glenohumeral joint by treating the soft tissue and the bony lesions. Advantages of an arthroscopic approach include smaller incisions, less disruption of the subscapularis, and the ability to evaluate the joint for other intra-articular lesions. The view afforded by the camera may allow for more accurate placement of the graft in the joint.

Rates of instability recurrence after Bankart and bone block procedures vary widely in the literature, ranging from 0% to 30% for arthroscopic Bankart repair and from 2% to 14% for the bone block procedures . A recent systematic review cites the recurrence rates for these two procedures to be 19.5% and 8.7%, respectively. Patients with recurrent dislocations and 25% bone loss make up the majority of instability patients, as opposed to first-time dislocators and patients with >25% bone loss. There is no consensus on the best treatment type for patients with recurrent anterior shoulder instability with subcritical (<25%) bone loss. However, most of the evidence to support bone grafting over soft tissue repair in this patient population has been retrospective, and there has been no randomized controlled trial comparing Bankart with a bone block technique, data regarding newer arthroscopic bony glenoid augmentation is even more limited.

While a multi-site, double-blinded-randomized controlled trial would provide the best evidence for the preferred technique, the feasibility of such a project is unknown. The investigators therefore propose a pilot multi-site, double-blinded randomized controlled trial to compare the outcomes of arthroscopic Bankart repair with those of arthroscopic Bankart repair plus bony glenoid augmentation (i.e. AAGR). The goal of this pilot is to assess the feasibility of recruiting patients across multiple sites while adhering to study protocols before conducting a definitive RCT which requires more resources (financial and otherwise). Additionally, most of the data on the AAGR technique is from a single surgeon and the investigators need to ensure that the results and outcomes are generalizable across multiple surgeons and multiple sites.