Rockwood Adults CH34

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CHAPTER 34 • Glenohumeral Instability

Polar type I Traumatic structural

Glenohumeral Instability: MATSEN AND THOMAS CLASSIFICATION

TUBS a. T rauma

Less muscle patterning

b. U nidirectional c. B ankart lesion d. S urgery

AMBRII a. A traumatic

b. M ultidirectional c. B ilateral laxity d. R ehabilitation e. If surgery is necessary, then need to tighten

Polar type III Muscle patterning non-structural

Polar type II Atraumatic structural

1. I nferior Capsule 2. Rotator I nterval

Less trauma

of instability with a triangle diagram to highlight the interplay between these three groups. Polar group 1 includes patients who present with a significant traumatic event that is unidi- rectional and results in a Bankart lesion in the anteroinferior glenoid. Polar group 2 includes patients who experience no his- tory of shoulder trauma with capsular dysfunction and struc- tural damage to either the labrum or the cartilage. Both polar groups 1 and 2 do not have any abnormal muscle patterning on clinical examination or EMG testing. In polar group 3, the patients have no history of trauma and no structural damage to the labrum or glenoid cartilage. They will often have capsular dysfunction with bilateral shoulder presentations. There can be overlap between the three polar groups. Figure 34-26.  Stanmore classification system of shoulder instability; the diagnosis is made on the basis of clinical history, examination, and arthroscopic findings. Polar group 1 contains patients with traumatic event that is unidirectional resulting in a lesion on the MRI images. Polar group 2 patients experience no trauma but present with capsular dysfunction and structural damage to the labrum or cartilage. Group 3 polar patients have no history of trauma or structural damage within the shoulder joint. They typically will present with abnormal muscle patterning on clinical examination or EMG testing.

Matsen et al. 148 described a simple classification of shoulder instability with two groups of patients with shoulder instabil- ity. In their retrospective review of open anterior Bankart repair cases, 97% of their patients had a classic Bankart lesion from a traumatic event. Therefore, their first group is characterized by a history of traumatic event leading to unidirectional shoulder instability. These shoulders are often found to have a tear in the anteroinferior glenohumeral ligament. In the high-risk patients, including male, younger age, or those participating in contact sports, surgical stabilization was recommended after primary dislocation to help prevent recurrent instability and further damage to the intrinsic intraarticular structures of the shoulder. TUBS represents Traumatic Unidirectional Bankart lesion and Surgery. In the second group of patients, there was no history of trauma and they are much more prone to the development of MDI. The first line of treatment in these patients is rehabili- tation with the focus on rotator cuff and deltoid strengthening. If surgery is needed, the capsular laxity is managed with a shift done either arthroscopically or open. Both the inferior capsule and the rotator interval are closed during surgery to prevent recurrence of instability in this group of patients. Thus, the term AMBRII was developed for this second group of patients.

Glenohumeral Instability: POSTERIOR INSTABILITY ABC CLASSIFICATION

Glenohumeral Instability: STANMORE CLASSIFICATION Polar type 1—Traumatic and structural a. Acute

A (First time)

A1. Subluxation A2. Dislocation

b. Persistent c. Recurrent

B (Dynamic)

B1. Functional B2. Structural

Polar type 2—Atraumatic and structural a. Recurrent

C (Static)

C1. Constitutional C2. Acquired

Polar type 3—Muscle patterning and nonstructural a. Recurrent b. Persistent

The ABC classification of posterior shoulder instability was proposed by Moroder and Scheibel. 159 This system offers a sim- ple yet comprehensive classification of posterior shoulder insta- bility based on underlying pathophysiology, and the authors also proposed treatment methods based on a literature review (Table 34-2). The three main groups, ABC, are based on the type of

In the Stanmore classification system (Fig. 34-26), the diagnosis of instability is made on the basis of clinical history, examination, and arthroscopic findings. 133 Additionally, if mus- cle dysfunction is suspected, electromyography (EMG) testing should be obtained. The authors prefer to present this model