Onset of instability

The onset of symptoms in the MDI patient is generally insidious in nature or from what would usually be considered a minor episode. However, it is important to keep in mind that a history of a defining traumatic event does not exclude someone from having MDI. Traumatic or athletic overuse, particularly in the overhead athlete, can result in the onset of symptoms in the MDI patient. So, too, can a period of inactivity. Consideration of the contributing nuisances that cause the onset of instability help to guide critical elements in the tenor of the rehabilitation process. Any instance that has any traumatic variation should initially concentrate on symptom management and reestablishing a nonpainful controlled ROM. The MDI element is focused on reestablishing neuromuscular control of the humeral head on the glenoid. Caution is placed on avoiding excessive stretching of the joint capsule through aggressive ROM activities. The goal is to return the patient’s symptom-free ROM and enhance strength, proprioception, dynamic stability, and neuromuscular control, particularly at the specific points of motion or directions that result in instability complaints.

Duration of symptoms

The longer symptoms have been present, the potentially more challenging the rehabilitation process becomes. Generally poorer rotator cuff and periscapular muscular control and performance are seen in longstanding symptomatic MDI patients. Often even the most basic traditional shoulder exercises are symptomatic and unsuccessful with these patients. The longer symptoms have been present, the potentially greater the level of difficulty in controlling dynamic upper limb movement. Positioning these patients often requires a nontraditional exercise approach that focuses on humeral head control in pain-free movements and exercises, allowing for the advancement of the patient to traditional exercises once the cycle of uncontrolled instability has been broken.

Primary direction of instability

The primary direction of instability will also play a role in program construction. Global capsular laxity is inherent to the MDI patient; however, most often they will exhibit greater symptoms and dysfunction in either an anteroinferior or posteroinferior direction.

Anteroinferior MDI patients most frequently exhibit instability complaints when the arm is moved into an abducted and externally rotated position. Conversely, patients with a predominantly posteroinferior instability component complain most often when their shoulder is brought into forward flexion and adduction. These patterns of symptom manifestation help in program creation. They guide the end range areas to avoid initially in order to control symptom exacerbation and the directions for greater focus later in the process to retrain proprioception and neuromuscular control to eliminate instability symptoms and complaints.

End-range neuromuscular control

The patient’s level of neuromuscular control, particularly at the end range of shoulder motion, is the next critical element to consider in the rehabilitation process. Neuromuscular control is best defined as the efferent, or motor, output in reaction to an afferent, or sensory, input. ^, The afferent input is the ability to detect the glenohumeral joint position and motion in space with resultant efferent response by the dynamic stabilizers as they blend with the joint capsule assisting in the stabilization of the humeral head on the glenoid. Instability results in the humeral head not centering itself within the glenoid, thereby compromising the surrounding static stabilizers and placing the dynamic stabilizers in a chronic position of inefficiency. The patient with poor neuromuscular control may exhibit excessive humeral head migration with the potential for reinjury, an inflammatory response, and reflexive inhibition of the dynamic stabilizers.

Several authors have reported that neuromuscular control of the glenohumeral joint may be negatively affected by joint instability. ^, Lephart et al. compared the ability to detect passive motion and the ability to reproduce joint positions in normal, unstable, and surgically repaired shoulders, reporting a significant decrease in proprioception and kinesthesia in the shoulders with instability when compared to both normal shoulders and shoulders undergoing surgical stabilization procedures. Smith and Brunolli reported a significant decrease in proprioception following a shoulder dislocation. Blasier et al. reported that individuals with significant capsular laxity exhibit a decrease in proprioception compared to patients with normal laxity. Zuckerman et al. noted that proprioception is affected by the patient’s age, with older subjects exhibiting diminished proprioception than a comparably younger population.

Combined, these investigations all point out reasons why the MDI patient will usually present with poor proprioception and neuromuscular control. This must be successfully addressed from the beginning of the rehabilitation process with humeral head control and periscapular activation exercises, then progression through the advanced phases of the process, where focus on end range dynamic control of the glenohumeral complex is essential.

Presence of neurovascular symptoms

Neurovascular symptoms of numbness and paresthesia can be present in the MDI patient, particularly one who participates in overhead activity and sports. ^, When present, these symptoms must be addressed and managed in conjunction with addressing the lack of dynamic control of the glenohumeral joint and scapulothoracic complex.

Arm dominance and bilaterality of symptoms

The involvement of the dominant versus nondominant arm and/or the presence of bilateral symptoms also must be considered in the rehabilitation process. Arm dominance significantly influences the successful outcome of shoulder instability patients with the success rates of patients returning to overhead sports after a traumatic dislocation of their dominant arm being shown to be extremely low. ^, While this is not a direct corollary to the MDI patient, it provides some insight into the difficulty of returning the MDI athlete to overhead sport. Patients that frequently perform an overhead motion or sport—such as tennis, volleyball, or a throwing sport—must be rehabilitated with elements that include sport-specific, end-range dynamic stabilization exercises, neuromuscular control drills, and plyometric exercises in the overhead position once pain-free ROM and adequate strength have been achieved.

Concomitant pathologies

The next factor involved is the consideration of concomitant pathologies, including other tissues that may have been affected in an injury as well as the patient’s premorbid tissue status. Disruption of the anterior capsulolabral complex from the glenoid commonly occurs during a traumatic injury, resulting in an anterior Bankart lesion; these injuries can render the MDI patient even more unstable. ^,

Additional possible concomitant injuries that may occur and affect the rehabilitation process include Hill-Sachs lesion, reverse Hill-Sachs lesion, glenoid bone loss, bone bruise, bony defect of the glenoid, type V superior labrum anterior posterior lesion, and injury to the rotator cuff. Significant or problematic bone loss is unusual in the vast majority of MDI patients.

These concomitant lesions will significantly affect the course of rehabilitation and program development to protect the healing tissue after injury or following surgery. The tissue with the greatest susceptibility for compromise or reinjury must always be the primary considering factor in the formulation of a rehabilitation program in the presence of concomitant injury.

Patient age

Because patients with MDI are typically in their teens to 20s, special consideration should be paid to this factor in the development of a rehabilitation program. Education of both the patient, parents, and/or significant other along with any other stakeholders is crucial to program success. Everyone must understand the expected course and the critical elements of compliance and receive a clear explanation of the requirements to address the MDI component effectively. Psychological factors of this variable are often significant and cannot be overlooked when creating a successful program. Not only must the program requirements be clearly articulated, but it is also imperative that the patient be positively supported and encouraged. Patient buy-in is essential to the successful implementation of a rehabilitation program in the younger, chronically affected MDI patient.

Previous treatment

Previous treatment, whether nonoperative or operative, should be considered in program construction. The MDI patient may have undergone multiple previous attempts in resolving the symptoms; many of these are often unsuccessful or of limited positive results. These attempts must be understood, both for their successes and failures. Program construction should be focused on fashioning a program that creates an alternative direction in rehabilitation geared to reestablish dynamic upper limb control and to provide the MDI patient with a positive psychological framework to approach a new round of rehabilitation that is different from the previously unsuccessful interventions.

Patient goals

The last, and possibly most critical, factors to consider in the MDI rehabilitation process are the level of participation and type of activities the patient desires to return to once asymptomatic control and dynamic stability have been obtained. Patients who desire to return to strenuous and aggressive activities, especially overhead or contact sports, must understand the potentially prolonged nature of MDI rehabilitation and the need for continued ongoing stabilization training. The challenges should not be understated and the importance of a commitment to participation in the entire program must be emphasized. Rehabilitative success for the MDI patient involves not only regaining dynamic humeral head control but also retraining end-range neuromuscular function in previously symptomatic movements to return to higher level function. This is no short-term, easy feat and will require the dedication of both the patient and the clinician to successfully attain the desired function level.