Locked Posterior Shoulder Dislocation (LPSD)

Fig. 32.1

“Through line” sign on an AP radiograph

A computed tomography (CT) scan is essential to determine the size and exact location of the reverse Hill-Sachs defect. Cicak [3] introduced a simple but effective method to determine and classify the size of bony defects of the humeral head in axial sequences of a CT scan (Fig. 32.2). Additionally, further lesions (e.g., of the glenoid) can be excluded.

Fig. 32.2

Determination of the size of the defect of the articular surface of the humeral head in axial sequences of a CT scan. The defect is marked with the white dashed line. According to Cicak it can be estimated by dividing the humeral head into a 25% (blue line) zone and a 50% (yellow line) zone. In this case the defect is about 30–40% of the articular surface

Magnetic resonance imaging (MRI) are helpful in chronic cases of LPSD to evaluate ligamentous injury or rotator cuff tears. For a primary diagnosis, MRI is generally not recommended.

32.4 Treatment

The choice of treatment depends on the size of the humeral defect, the time interval from dislocation to diagnosis, and the patient’s demands (Fig. 32.3). In cases where the reverse Hill-Sachs lesion is less than 20% of the articular surface and the duration of the dislocation is less than 3 weeks, closed reduction can be attempted. When the duration of the dislocation is more than 3 weeks, closed reduction is usually impossible and surgery is recommended. In those cases with a Malgaigne fracture of less than 20%, an arthroscopic reduction is considered to be the therapy of choice; further arthroscopic treatment, like tenodesis of the subscapularis tendon in case the reverse Hill-Sachs lesion appears to be engaging (modified McLaughlin procedure, Fig. 32.4), can be performed simultaneously. For Malgaigne fractures >20%, open surgery is usually required to reduce the dislocation and augment the humeral head through a deltopectoral approach.

Fig. 32.3

Treatment algorithm for LPSD

Fig. 32.4

Modified McLaughlin procedure as described from Krackhardt et al. The subscapularis tendon is attached to the reverse Hill-Sachs lesion and protects the humeral head from engaging at the posterior glenoid rim in internal rotation of the arm

32.4.1 Conservative Treatment

A locked posterior shoulder dislocation is often well tolerated due to little pain and little limitation of forward elevation allowing the performance of many activities of daily living. For this reason, nonoperative treatment must be considered in certain patients, including those with limited demands, uncontrolled seizures, or inability to comply with postoperative rehabilitation. Moreover, nonoperative management is considered first-line treatment in cases where closed reduction is performed early (within 3 weeks from dislocation), the shoulder appears stable with no further signs of re-dislocation, and the reverse Hill-Sachs lesion covers less than 20% of the articular surface of the humeral head.

In general, conservative treatment consists of immobilization of the shoulder in 10° of abduction and 15° of external rotation in a shoulder orthosis for 6 weeks; passive mobilization up to 60° of abduction and flexion can be performed during this time. Active-assisted mobilization starts 3 weeks after surgery. After 6 weeks, the range of motion is unrestricted, and further physiotherapy is advised to improve sensory-motor stability and scapulothoracic rhythm.

32.4.2 Operative Treatment

32.4.2.1 Bony Defect <20% of the Articular Surface of the Humeral Head

As mentioned above, a PLSD with a bony defect of less than 20% can be primarily treated conservatively. If after nonoperative treatment the shoulder remains unstable, arthroscopic treatment is required. Arthroscopic posterior shoulder stabilization involves an anatomic restoration of the posterior labrum, a vertical shift of the posterior capsule, and a tenodesis of the subscapularis tendon into the reverse Hill-Sachs lesion (modified McLaughlin procedure). in cases where the defect of the humeral head engages with the glenoid rim. In general, the tenodesis is performed using suture anchors to secure the subscapularis tendon into the humeral defect (Fig. 32.4).

32.4.2.2 Bony Defect 20–50% of the Articular Surface of the Humeral Head

A common treatment for bony defects of 20–50% is the transfer of the lesser tuberosity with the attached subscapularis tendon into the reverse Hill-Sachs lesion as described by Hughes and Neer [5]. They modified the method of McLaughlin [7] who originally described the transfer of the detached subscapularis tendon secured through drill holes in the humeral head. This modification allowed better bony filling of the defect and better reinsertion of the subscapularis tendon.

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