Surgical Approach

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CHAPTER 26 Surgical Approach

Two surgical approaches have been described for implantation of a reverse prosthesis. The anterior superior approach was initially used because it makes use of the rotator cuff defect. More recently, the deltopectoral approach has been used for insertion of a reverse prosthesis. We perform all reverse prostheses through the deltopectoral approach, which is our preferred approach for five reasons:

1. Deltoid violation A reverse prosthesis relies on the deltoid muscle to power elevation of the arm. The anterior superior approach violates the deltoid muscle, which may be a problem.

2. Level of humeral resection Glenoid exposure when using the anterior superior approach may require more resection of the proximal humerus than when using the deltopectoral approach. During the anterior superior approach, the humerus is retracted inferiorly to obtain access to the glenoid. If glenoid exposure is inadequate after appropriate soft tissue release, the only solution to enhance glenoid exposure is resection of more of the proximal humerus. More bone resection may make proper deltoid tensioning difficult and lead to weakness in elevation.

3. Glenoid component positioning It is generally agreed that the reverse glenoid component should be placed inferiorly on the glenoid face to help prevent impingement of the humeral component on the scapula and subsequent scapular notching. The need to retract the humerus inferiorly to access the glenoid with the anterior superior approach creates more difficulty in getting the glenoid component aligned with the inferior aspect of the glenoid face. Debate exists on whether inferior tilt should be introduced during glenoid reaming so that the glenoid component is positioned to better avoid scapular notching. However, it is agreed that superior tilt should be avoided. Using the anterior superior approach risks inadvertently placing the glenoid component in a superiorly tilted position, which risks glenoid failure (Fig. 26-1).

4. Extensile exposure The deltopectoral approach can easily be extended into an anterolateral approach to the humerus, whereas the axillary nerve limits distal extension of the anterior superior approach. Review of a consecutive series of 100 reverse prostheses performed at Texas Orthopedic Hospital demonstrated that the underlying etiology necessitated a more extensile exposure than what could be obtained with an anterior superior approach in 36 cases (18 nonunion/malunion, 17 revision, 1 fixed dislocation requiring anterior glenoid reconstruction with iliac crest autograft).

5. Familiarity One third of our shoulder replacements involve the use of a reverse prosthesis. The other two thirds use an unconstrained device implanted through a deltopectoral approach. We are very comfortable performing unconstrained shoulder arthroplasty through a deltopectoral approach and do not substantially change this approach when implanting a reverse prosthesis.

Figure 26-1 A, Radiograph of a reverse prosthesis implanted through an anterior superior approach with the glenoid component inadvertently inserted with a superior tilt. B, This malpositioned implant eventually failed.

TECHNIQUE FOR THE DELTOPECTORAL APPROACH

The deltopectoral approach used for implantation of a reverse prosthesis is nearly identical to the deltopectoral approach used for unconstrained shoulder arthroplasty described in Chapter 8. The skin incision, subcutaneous dissection, development of the deltopectoral interval, identification of the conjoined tendon and coracoid process, and retractor placement proceed as detailed in Chapter 8 and shown in Figures 8-1 through 8-6.

With the arm abducted and externally rotated, the apex formed by the insertion of the coracoacromial ligament and the conjoined tendon onto the coracoid process is identified. The coracoacromial ligament is sectioned just lateral to its insertion on the coracoid with a needle tip electrocautery to enhance exposure of the superiorly migrated humeral head (Fig. 26-2). This is in contrast to the surgical approach used for unconstrained shoulder arthroplasty, in which the coracoacromial ligament is preserved to act as a static restraint to anterior superior migration. When we use a reverse prosthesis, the prosthetic design eliminates the need for this static restraint.

Figure 26-2 A and B, Release of the coracoacromial ligament with the electrocautery.

The conjoined tendon is retracted medially to expose the anterior aspect of the glenohumeral joint. The anterior humeral circumflex vessels (the “three sisters”) are suture-ligated together just as in cases of unconstrained shoulder arthroplasty. The arm is then placed in forward flexion and neutral rotation, and the axillary nerve is identified by direct visualization after blunt dissection. This ensures protection of the nerve throughout the procedure.

In cases in which the subscapularis is intact, it is handled identically to cases of unconstrained shoulder arthroplasty. Two stay sutures of no. 2 polyester are placed in the subscapularis tendon near the musculotendinous junction. The glenohumeral joint is often already accessible through a large rotator cuff tear superiorly (Fig. 26-3). The anatomic neck of the humerus is identified, and a scalpel is used to transect the subscapularis tendon and joint capsule along the anatomic neck of the humerus. The electrocautery replaces the scalpel at the inferior portion of the subscapularis to cauterize the previously ligated anterior humeral circumflex vessels. A humeral head retractor is placed in the glenohumeral joint and is used to retract the humeral head posteriorly. A circumferential release of the subscapularis tendon is performed, with release of the superior, middle, and inferior glenohumeral ligaments just as in unconstrained shoulder arthroplasty. The subscapularis is then tucked into the subscapularis fossa with forceps and held with a glenoid rim retractor. In contrast to cases of unconstrained arthroplasty, no sponge is placed in the subscapularis fossa because insertion of screws for fixation of the glenoid base plate risks entrapment of the sponge with screws as they penetrate the anterior scapular cortex (Fig. 26-4). If the subscapularis tendon is not present, the remaining subscapularis bursa is excised to expose the glenohumeral joint, and the humeral head retractor and glenoid rim retractor are inserted. If present, the intra-articular portion of the long head of the biceps tendon is handled as described in Chapter 5 (tenotomy or tenodesis).