Anterior Instability: Preoperative Issues

Background

Traumatic instability of the shoulder joint is generally associated with a Bankart lesion, in which the anteroinferior glenoid labrum and inferior glenohumeral ligament (IGHL) detach from the glenoid. ^, Although open or arthroscopic surgery is the standard treatment approach for shoulder instability, there are several preoperative complications that directly influence patient outcome and surgical success. The most pertinent include the presence of glenoid bone loss, Hill–Sachs lesions (HSL), Bankart lesions, humeral avulsion of glenohumeral ligaments (HAGL), and anterior labroligamentous periosteal sleeve avulsion (ALPSA). As a result, surgeons must be able to properly identify these factors before surgical intervention and adjust treatment strategies accordingly. All of this is important to prevent complications such as recurrence after surgical intervention.

History and Physical Examination

A thorough history is a crucial first step in assessing a patient with suspected shoulder instability. Evaluation should begin with age, gender, antecedent function, hand dominance, degree of activity, and level of sports participation. Although these questions are seemingly standard, the answers may exclude the patient from surgery or provide evidence of preoperative complications. The history should also include specific information regarding age of first instability event, number of dislocations or subluxations, mechanism of injury, required manual reductions, positioning during injury, and prior intervention attempts. These details may provide insight into the risk of attritional bone loss and injury recurrence. For example, patients with glenoid bone loss typically describe a high-energy mechanism of injury and a prolonged history of instability symptoms. Furthermore, the age of first dislocation is an important prognostic indicator because approximately 90% of patients under the age of 20 years and 10% of patients over the age of 40 years can experience recurrence. Overall, the history provides critical information for determining the presence of preoperative complications before imaging and helps focus the physical exam.

The physical examination of a patient with shoulder instability is equally essential and includes direct comparison to the contralateral shoulder. General appearance can reveal muscular atrophy, surgical scars, and asymmetry. Palpation of the anterior and posterior glenohumeral, acromioclavicular, and sternoclavicular joints may identify point tenderness. However, location of pain is not a specific indicator of glenohumeral instability. Structure, function, neurovascular status, strength, and range of motion (ROM) should also be tested during the physical examination. Limited ROM may indicate additional pathology, diagnoses, or need for treatment. Specifically, significant stiffness must be addressed before surgical intervention to avoid progressive loss of motion. Shoulder stability must also be assessed to determine the presence of joint laxity, specifically within the various glenohumeral ligaments, because preexisting joint laxity has been associated with recurrence and postoperative failure rates. Elbow hyperextension, metacarpophalangeal hyperextension, and the thumb-to-forearm test should be particularly noted.

Additional evaluation of glenohumeral joint laxity may include the “sulcus sign” and “load and shift” tests. The sulcus sign test assesses the integrity of the rotator interval, which is comprised of the superior glenohumeral ligament (SGHL) and the coracohumeral ligament. The humerus is pulled inferiorly with the arm in 0 degrees of abduction and graded by the degree of subluxation. If the sulcus sign disappears when the test is repeated in external rotation, the rotator interval is considered competent. Laxity of the anterior and posterior capsule restraints can also be assessed by differing degrees of arm abduction during the anterior load and shift test. While the patient is supine, a small compressive load is applied to the humeral head for centralization within the glenoid fossa, and an anterior force is applied to translate the humeral head anteriorly. The arm is manipulated to neutral, 45 degrees, and 90 degrees of abduction to test the SGHL, middle glenohumeral ligament, and IGHL, respectively. Both maneuvers are useful in providing insight into the presence of instability and the possibility of a Bankart lesion. ^,

The apprehension test is also useful in evaluating patients with anterior instability, aiding in diagnosis, and determining risk of recurrence. Progressive external rotation is applied to the shoulder with 90 degrees abduction and 90 degrees flexion of the elbow. Pain occurs in patients with either anterior instability or impingement and does not necessarily indicate a positive result. However, a sense of impending instability that is relieved by changing the direction of applied force from anterior to posterior is considered a positive relocation sign. The apprehension test has been heavily correlated with recurrent dislocation, with recurrence in 71.4% of patients with a positive sign and 36.8% of patients with a negative sign. Although not a perfect predictor of recurrence, the apprehension test is useful for categorizing patients as being at high or low risk of subsequent anterior shoulder dislocation. Furthermore, a positive apprehension test between 30 and 90 degrees of abduction strongly indicates bone loss and dictates preoperative imaging to further qualify the glenoid deficiency.

It is important to recognize factors that may predispose a patient to having a higher chance of recurrence after surgical intervention. All of these factors, either solo or in sum, are additive to the development of instability pathology. This includes: (1) increase in glenoid bone loss; (2) increase in humeral head Hill–Sachs size and/or orientation; (3) increase in size of the labrum tear; (4) turning an off-track lesion into an on-track lesion; (5) increase in frequency of ALPSA tears; 6) and additional cartilage injury. These patient factors based on history are presented in Box 24.1 .

All of these may indicate a pathological finding as described and contribute to lesser success rates with certain types of surgical intervention. Besides patient history, there are also important examination factors that contribute to proper preoperative workup, counseling, and surgical procedure selection ( Box 24.2 ).