7.1 Which Surgical Approach Is Most Beneficial in RSA?

The superior or anterosuperior (AS) approach was the original recommended approach for reverse shoulder arthroplasty (RSA) by Grammont. As the procedure became more popular and indicated in more complex situations, many shoulder surgeons utilized the deltopectoral (DP) approach in an effort to gain better access to the proximal humerus. While some surgeons feel that the superior approach affords better and less invasive exposure to the glenoid surface, the controversy remains as to which is the best approach. The following debate will enlighten the readers and help them choose the best surgical approach for their patients.

7.2 Deltopectoral Approach

Several surgical techniques for RSA have been described, including the transacromial approach first described by Grammont, as well as the modified AS, DP, and clavicle osteotomy approaches. The two most common approaches are the DP and AS largely due to the considerable complications associated with the transacromial and clavicle osteotomy approaches. ¹ Each has its strengths and limitations, although this chapter focuses on why the DP is the more attractive option.

In order to fully appreciate the pros and cons of each approach, one must keep in mind the technical goals of performing an RSA. Experience with the device has taught us that it is important to place the glenosphere low on the glenoid in order to minimize inferior scapular notching. It is also important to place the glenosphere in either neutral or inferior tilt as superior tilt can lead to instability and glenosphere loosening. Since RSA is often used as a salvage operation in the setting of a previously failed arthroplasty, it is important to have access to the humeral shaft to facilitate humeral-sided revision surgery. Finally, and most importantly, function following RSA is solely dependent on the integrity of the deltoid and therefore preservation of its origin and insertion is of paramount importance in the RSA procedure. What is not clear from the literature is the role of the subscapularis in the postoperative RSA. The DP approach is superior to the AS approach in achieving every important technical goal of the RSA procedure.

The DP approach has been the workhorse of shoulder surgery since its inception. It was first described by Charles Neer in 1974 for use in shoulder arthroplasty. ² It follows a true internervous plane between the pectoralis major, which is innervated by the upper and lower pectoralis nerves, and the deltoid, which is innervated by the axillary nerve. The approach is also extensile in that it can be extended down the humerus to the elbow, where it can be continued to the approach originally described by Henry. ³

The skin incision for the DP approach typically begins just lateral to the tip of the coracoid and extends distally to just lateral to the long head of the biceps tendon. Once the skin incision is made, the fatty strip containing the cephalic vein is identified. The cephalic vein can be retracted either laterally with the deltoid or medially with the pectoralis. However, there are fewer crossing vessels when the vein is retracted laterally. The surgeon typically encounters one set of crossing vessels at the level of the tip of the coracoid that can predictably be identified and coagulated. The underlying clavipectoral fascia is released and the biceps is either tenotomized or tenodesed. The subscapularis, if intact, is either tenotomized or reflected with a lesser tuberosity osteotomy, exposing the capsule for the remainder of the procedure. At the conclusion, the subscapularis is repaired if there is sufficient tissue to justify. ² , ⁴

Proponents of the AS approach espouse theoretical advantages that include better frontal exposure of the glenoid, preservation of the subscapularis tendon, and ease of axial preparation of the humerus. However, drawbacks of the AS approach include weakening of the anterior deltoid, less extensile humeral exposure, and improper glenosphere position with excess height and superior tilt leading to increased scapular notching due to difficulty in visualizing the inferior glenoid. ⁴ , ⁵ In contrast, the DP technique offers deltoid muscle preservation since the shoulder is approached through an internervous plane, greater access to inferiorly place the glenoid component, extensile humeral exposure, and the ability to perform a latissimus dorsi transfer. The only theoretical disadvantage of the DP approach is sacrifice of the subscapularis, if it is present to begin with. ⁴ , ⁵

The true impact of these theoretical costs and benefits has been examined in several studies. The most frequent problem reported after RSA is radiographic scapular notching. This phenomenon is likely due to mechanical impingement of the medial rim of the humeral cup against the scapular neck in adduction, and has been reported in 35 to 76% of patients with cuff tear arthropathy ¹ , ⁶ and may be associated with worse clinical outcomes, ⁷ although this is controversial. ⁶ In a biomechanical cadaveric study of the reverse Delta III prosthesis, Nyffeler et al found that placing the glenosphere distally beyond the inferior glenoid rim resulted in significant improvement, allowing for the greatest amount of adduction before impingement occurred. ⁸ The results of this study suggest that less notching might occur with inferiorly placed glenospheres, a concept borne out in a clinical study by Simovitch et al. ⁹ Theoretically, visualization of the inferior positioning of the glenoid component is worse through a superior approach, ¹ with studies by Lévigne et al, ⁶ Melis et al, ¹⁰ and Molé et al ⁵ confirming a significantly higher rate of notching through the AS, compared to the DP, approach. Another study by Gillespie et al showed glenosphere superior tilt and humeral valgus associated with the AS approach, but found no difference in the rate of scapular notching. ⁴

Another common complication after RSA, instability has a postoperative incidence ranging from 0 to 9%. ¹ , ⁵ , ¹¹ , ¹² , ¹³ , ¹⁴ , ¹⁵ It has been suggested that the DP approach is associated with increased rates of instability, which is likely related to weakened anterior restraints due to release of the subscapularis and associated inferior and middle glenohumeral ligaments, predisposing to anterior instability. It has also been suggested that inferior displacement of the humerus due to the prosthesis places increased tension on the subscapularis repair, increasing the likelihood of subscapularis failure. ¹² In support of this idea, Edwards et al showed that dislocations occurred more frequently in those with irreparable tendons, ¹⁶ while others have reported subscapularis compromise in all cases of dislocation. ¹⁷ , ¹⁸ Reviews of the literature have indeed demonstrated a higher rate of instability with the DP approach, ¹ , ⁵ with Zumstein et al reporting that the DP approach was used in 97.3% of cases of instability ¹ and a multicenter study by Molé et al demonstrating a significantly higher rate of instability with the DP (5.1%) versus AS (0.8%) approach (p < 0.001). ⁵ Nevertheless, whether this difference is clinically meaningful is unclear. In a study by Wall et al using a DP approach, the authors found that while patients with subscapularis repair had greater improvement in internal rotation, repair was not significantly associated with postoperative complications or dislocations. ¹⁹ Furthermore, Clark et al reported that subscapularis repair in RSA had no significant effect on complication rate, dislocations, pain, or function. ¹¹ Although integrity of the subscapularis may contribute to postoperative instability, whether this difference is functionally compromising is not known; furthermore, it is likely that additional factors, such as inadequate deltoid tension and/or component impingement, play an important role.

Deltoid compromise is another theoretical disadvantage associated with the AS approach, although little is known about the extent of weakening or rate of dehiscence. In a small study by Gillespie et al, 16% (3 of 19) of patients in the AS group experienced deltoid dehiscence that required further surgery. ⁴ One method to minimize this risk is to opt for a transacromial approach rather than dividing the anterior deltoid, which in the multicenter study by Molé et al resulted in no identified tears of the deltoid postoperatively. ⁵ Although little is known about the long-term impact of splitting the deltoid, in their RSA study, Boileau et al report initially using a superior, transdeltoid approach before switching to a DP approach after just four cases, due to concerns about damaging the deltoid, whose optimal function is required for RSA success, as well as needing greater access to the humeral diaphysis. ¹²

In conclusion, studies have reported success with both DP and AS approaches for RSA. The DP approach is a standard internervous approach with which all shoulder surgeons are familiar, and it offers extensile exposure in the case of intraoperative complications or revision procedures while not disrupting the deltoid, whose optimal function is critical for the success of RSA. The AS approach, on the other hand, spares the subscapularis which has inconsistently resulted in lower dislocation events in the literature, although the functional implications of this benefit are not clear in RSA. However, the AS approach increases the chance of improper positioning of the prosthesis components, which can lead to scapular notching and eventual loosening. Further studies with longer-term follow-up are needed to determine the clinical impact of differences associated with these approaches, such as scapular notching and manipulation of the deltoid. Although one approach has not been clearly demonstrated to be superior to the other, in the face of current data and personal experience we believe that the DP approach offers a better balance of benefits and risks for RSA.

Related posts:

8 Indications and Techniques of BIO-RSA for Cuff Tear Arthropathy, Including Associated Soft Tissue Transfers for Loss of External Rotation Chapter 10 Reverse Shoulder Arthroplasty for Acute Fracture: Indications and Technique Chapter 11 Reverse Shoulder Arthroplasty for Fracture Sequelae: Indications and Technique 6 Preoperative Work-up and Surgical Approaches for Reverse Shoulder Arthroplasty Chapter 15 Reverse Shoulder Arthroplasty in Revision Shoulder Arthroplasty: What I Look for and How I Do It hapter 13 Reverse Shoulder Arthroplasty for Massive Anterosuperior Rotator Cuff Failure

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