Instability-Impingement Complex

Instability-Impingement Complex

The scheme of instability and associated impingement noted by Jobe and associates uses a four-group classification system, with instability as the central theme. In the young athlete, participation in overhead sports such as throwing, swimming, tennis, and volleyball requires large ranges, forces, and repetitions. These demands result in microtrauma to the static and dynamic structures, laxity in the anterior capsule, anterior humeral head subluxation, and posterior capsule tightness. This combination has been described as the instability-impingement complex and is discussed in the following scheme.

Instability-Subluxation-Impingement-Rotator Cuff Tear

Individuals with pure compression impingement of the rotator cuff whose test results include positive impingement signs and negative signs of apprehension make up Group 1. Older recreational athletes are generally in this group, while younger athletes are rarely in this group. Group 1. Arthroscopic examination reveals a stable shoulder with an inferior surface rotator cuff tear and associated subacromial bursitis. The labrum and glenohumeral ligaments are normal. The principles of treatment are based on the results of the clinical examination and follow the general guidelines presented in Neer's model of compression cuff disease. Group 2 consists of individuals with impingement-associated instability with lip or capsule injuries, instability, and secondary impingement. Findings include positive compression, signs of apprehension and relocation, and arthroscopic findings of instability, labrum damage, and sub-surface rotator cuff tear. However, the results of instability are often so subtle, even when the patient is examined under anesthesia, that the underlying anomaly can be ignored. As with group 1 shock, most people respond to a conservative program that addresses specific deficits in mobility, strength, and endurance. Recognizing the underlying instability is the key to successful rehabilitation. If conservative treatment fails, surgery to stabilize the shoulder and debride any damage to the rotator cuff provides the best results. Isolated acromioplasty can exacerbate the underlying instability.

Individuals classified in group 3 have hyperelastic soft tissue that causes anterior or multidirectional instability and associated impingement. Hyperelasticity, evidenced by joint hyperextension, is the distinguishing feature between groups 2 and 3. In this case, the results of the signs of compression, apprehension and relocation are positive. Arthroscopic examination reveals an unstable shoulder, an attenuated but intact labrum, and an inferior surface rotator cuff tear. Jobe and Glousman highlighted the difficulty of clarifying the diagnosis in groups 2 and 3. Once the diagnosis is made and the underlying disease condition identified, appropriate rehabilitation measures are generally effective in returning the athlete to their sport. Group 4 consists of those individuals with pure anterior instability without associated conflict. The injury is caused by a traumatic event, resulting in an acute partial or complete dislocation. Clinical and arthroscopic examinations are compatible with an unstable shoulder, without impingement. Posterior Conflict As previously described, posterosuperior glenoid impingement (internal impingement) is an additional source of rotator cuff abnormality and is believed to be the leading cause of rotator cuff disease in athletes. In this case, the rotator


the sleeve is inserted between the greater tuberosity and the posterosuperior glenoid labrum. This disorder often occurs in pitchers and others involved in aerial activities. It is often associated with mild anterior instability, while patients with significant instability have no posterior impingement. Some researchers have challenged the hypothesis that this problem is found primarily in athletes and those with mild instability and have not found statistically significant relationships between contact position and injury mechanism, ROM, pitchers versus non-pitchers, or signs of impingement.

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