Evaluation of Recurrent Instability.

Last updated Friday, November 16, 2007

Figure 10

Figure 11

Figure 12

The history (traumatic)

TUBS history

Most patients presenting with TUBS are between the ages of 14 and 34 (see figure 10). These patients characteristically have difficulty throwing overhand, but many patients also have problems sleeping, putting their hand behind their head, and lifting a gallon to head level (See table 1 and figure 11). Their general health status as revealed by the SF 36 self assessment questionnaire is better on average than that of a comparable group of patients with atraumatic instability (see figure 12).

The initial dislocation

The most important element in the history is the definition of the original injury. As is evident to anyone who has attempted to recreate these lesions in a cadaver, substantial force is required to produce a traumatic dislocation--in most cadaver specimens, it is impossible to duplicate the Bankart injury mechanism because the humerus fractures first! In characteristic anterior traumatic instability, the structure that is avulsed is the strongest part of the shoulder's capsular mechanism: the anterior inferior glenohumeral ligament. In order to tear this ligament, substantial force needs to be applied to the shoulder when the arm is in a position to tighten this ligament. Thus the usual mechanism of injury involves the application of a large extension-external rotation force to the arm elevated near the coronal plane. Such a mechanism may occur in a fall while snow skiing, while executing a high speed cut in water skiing, in an arm tackle during football, with a block of a volleyball or basketball shot, or in relatively violent industrial accidents in which a posteriorly directed force is applied to the hand while the arm is abducted and externally rotated. Awkward lifting on the job and rear-end automobile accidents would not be expected to provide the conditions or mechanism for this injury. Direct questioning and persistence are often necessary to elicit a full description of the mechanism of the initial injury, including the position of the shoulder and the direction and magnitude of the applied force. Yet this information is critical to establishing the diagnosis.

An initial traumatic dislocation often requires assistance in reduction, rather than reducing spontaneously as is usually the case in atraumatic instability. Radiographs from previous emergency room visits may be available to show the shoulder in its dislocated position. Axillary or other neuropathy may have accompanied the glenohumeral dislocation. Any of these findings individually or in combination support the diagnosis of traumatic as opposed to atraumatic instability.

Traumatic instability may occur without a complete dislocation. In this situation, the injury produces a traumatic lesion, but this lesion is insufficient to allow the humeral head to completely escape from the glenoid. The shoulder may be unstable because, as a result of the injury, it manifests apprehension or subluxation when the arm is placed near the position of injury. In these cases there is no history of the need for reduction nor radiographs with the shoulder in the dislocated position. Thus the diagnosis rests to an even greater extent on a careful history that focuses on the position and forces involved in the initial episode.

The initial dislocation

The most important element in the history is the definition of the original injury. As is evident to anyone who has attempted to recreate these lesions in a cadaver, substantial force is required to produce a traumatic dislocation--in most cadaver specimens, it is impossible to duplicate the Bankart injury mechanism because the humerus fractures first! In characteristic anterior traumatic instability, the structure that is avulsed is the strongest part of the shoulder's capsular mechanism: the anterior inferior glenohumeral ligament. In order to tear this ligament, substantial force needs to be applied to the shoulder when the arm is in a position to tighten this ligament. Thus the usual mechanism of injury involves the application of a large extension-external rotation force to the arm elevated near the coronal plane. Such a mechanism may occur in a fall while snow skiing, while executing a high speed cut in water skiing, in an arm tackle during football, with a block of a volleyball or basketball shot, or in relatively violent industrial accidents in which a posteriorly directed force is applied to the hand while the arm is abducted and externally rotated. Awkward lifting on the job and rear-end automobile accidents would not be expected to provide the conditions or mechanism for this injury. Direct questioning and persistence are often necessary to elicit a full description of the mechanism of the initial injury, including the position of the shoulder and the direction and magnitude of the applied force. Yet this information is critical to establishing the diagnosis.

An initial traumatic dislocation often requires assistance in reduction, rather than reducing spontaneously as is usually the case in atraumatic instability. Radiographs from previous emergency room visits may be available to show the shoulder in its dislocated position. Axillary or other neuropathy may have accompanied the glenohumeral dislocation. Any of these findings individually or in combination support the diagnosis of traumatic as opposed to atraumatic instability.

Traumatic instability may occur without a complete dislocation. In this situation, the injury produces a traumatic lesion, but this lesion is insufficient to allow the humeral head to completely escape from the glenoid. The shoulder may be unstable because, as a result of the injury, it manifests apprehension or subluxation when the arm is placed near the position of injury. In these cases there is no history of the need for reduction nor radiographs with the shoulder in the dislocated position. Thus the diagnosis rests to an even greater extent on a careful history that focuses on the position and forces involved in the initial episode.

Subsequent episodes of instability

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