Reverse Shoulder Arthroplasty for Cuff Deficiency: Rationale and Mechanics


Chapter 39

Reverse Shoulder Arthroplasty for Cuff Deficiency


Rationale and Mechanics



Jonathan Clark, Brent Stephens, Jonathan Streit, and Mark Frankle

Introduction


Since being approved by the U.S. Food and Drug Administration in 2003, reverse shoulder arthroplasty (RSA) has become the standard of treatment for elderly patients with irreparable rotator cuff tears and arthritis. By 2020, it is projected that over 80,000 RSA procedures will be performed every year. A firm grasp on both patient selection and surgical technique will help guide surgeons as they treat this growing patient population. This chapter guides the surgeon in treating patients with rotator cuff tears not amenable to repair.

Procedure



Patient History



Patient Examination





  1. • The surgeon should focus on active and passive range of motion in forward flexion, abduction, external rotation (at side and in 90 degrees of abduction), and internal rotation. These motions should be assessed in both the standing and supine positions.
  2. • Evaluate for loss of external rotation manifested by Hornblower’s or external rotation lag sign.


    1. • Combined loss of active elevation and external rotation is an indication to perform a latissimus dorsi transfer in addition to RSA.

  4. • Test subscapularis strength/integrity via Napoleon’s/belly press test.
  5. • Note the appearance of shoulder shrug with attempted abduction, because this is a sign of pseudo paralysis (see Fig. 39.2).
  6. • Cervical flexion, extension, and rotation should be performed in a seated position.


    1. • Pain with any of these movements warrants further studies of the cervical spine.

Pearls





  1. • Pseudoparalysis of the shoulder has no clear definition, but it can be seen as a combination of physical exam findings:


    1. • Elevation less than 90 degrees
    2. • Appearance of shoulder shrug with attempted abduction
    3. • Pain




  5. image
    FIG. 39.1 In cases of an intact rotator cuff (A), the resultant force of the rotator cuff musculature (blue arrows) acts to center the humeral head in the glenoid and allow the force generated by the deltoid (green arrow) to rotate the arm with resulting force depicted by the gold arrow. In a deficient rotator cuff (B), there is no restraint to superior translation of the humeral head (gold arrow), so the deltoid contraction (green arrow) creates a shear force across the glenohumeral joint, leading to superior migration of the humeral head. A reverse prosthesis (C) creates a stable fulcrum that allows the deltoid to rotate the humerus around the fixed glenosphere even in the absence of the stabilizing effects of the rotator cuff (D). J Bone Joint Surg Am 2011;93(10):973–984.

  6. • Upper cervical radiculopathy (particularly involving C4 or C5) can mimic pseudo paralysis.


    1. • Radiculopathy may be distinguished by pain that extends beyond the elbow.
    2. • Patients may have pain with flexion/extension of the spine.
    3. • Any upper extremity neurologic deficit leading to deltoid dysfunction is an independent risk factor for poor outcome after RSA for massive cuff tear.

  8. • Previous rotator cuff surgery can result in deltoid dysfunction.
  9. • An electromyogram should be ordered when questions exist about axillary nerve activity.

Imaging





  1. • X-ray


    1. • Humeral head frequently has superior migration in relation to the glenoid (see Fig. 39.3).
    2. • Loss of acromiohumeral distance is seen with posterosuperior cuff tears.
    3. • Anterior subluxation may be noted on the axillary view in cases of anterior cuff tear.
    4. • Evaluate for os acromiale or acromial fracture.

  3. • Computed tomographic scan


    1. • Allows for better understanding of bony anatomy.


    3. image
      FIG. 39.2 (A–C) Pseudoparalysis of the right shoulder manifesting as shoulder shrug on attempted abduction. The green arrows indicate atrophy of the affected rotator cuff muscles, often seen in the setting of chronic massive tearing of the rotator cuff.

    4. • Note the version of the glenoid, translation of the humeral head (anterior, centered, posterior), and presence of osteophytes or loose bodies.
    5. • Superior migration of humeral head is noted in association with posterosuperior cuff tears, whereas anterior subluxation is seen with anterior cuff tears.
    6. • Look for the presence of os acromiale or acromial fractures.
    7. • Evaluate for the presence of fatty atrophy in the rotator cuff musculature. This is graded according to the Goutallier classification.

  5. • Magnetic resonance imaging (MRI)


    1. • Improves understanding of rotator cuff integrity.
    2. • Also allows for grading of degree of fatty infiltration.
    3. • Can demonstrate teres minor atrophy, which may be an indication to add a latissimus dorsi transfer at the time of RSA (see Fig. 39.4).
    4. • Isolated teres minor atrophy is seen on 3.3%–5.5% of shoulder MRI scans. This can be a unique pathological process or may be related to quadrilateral space syndrome.


Treatment Options



Surgical Anatomy


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Mar 28, 2020 | Posted by in ORTHOPEDIC | Comments Off on Reverse Shoulder Arthroplasty for Cuff Deficiency: Rationale and Mechanics

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