Technique

The DP approach has been described previously ( Fig. 1 ). In brief, an incision is made in the anterior portion of the shoulder approximating the DP interval. The cephalic vein is identified and is most often retracted laterally with the deltoid. Subdeltoid and subacromial adhesions are bluntly released and the clavipectoral fascia is incised. The biceps is then identified (if present), traced through the rotator interval, and tenotomized or tenodesed. When present, the subscapularis is detached from the lesser tuberosity by using a tendon peel approach, a tenotomy that leaves a cuff of tissue for later repair, or is reflected with a lesser tuberosity osteotomy. The capsule is released from the humerus past the 6 o’clock position. Humeral head osteophytes are removed and the humerus is prepared per the manufacturer-specific instrumentation. After the humerus is prepared, the glenoid is exposed in standard fashion and prepared. Once final components are placed, the shoulder joint is reduced, and wounds are closed over a deep surgical drain. The subscapularis is repaired at the conclusion of the procedure in most cases; however, this is based on surgeon preference and tendon integrity.

Typical skin incision for a DP approach.

Advantages

The DP approach has several advantages. The interval is an atraumatic, internervous, and intermuscular plane between the deltoid and pectoralis major. As such, it is an extensile approach that allows unencumbered access to the entire humerus. The deltoid origin is preserved and the muscle bellies are not violated. Given that a reverse arthroplasty is powered primarily by the deltoid muscle, reducing trauma to the deltoid has a theoretic advantage. In addition, the approach results in release of the anterior soft tissues and anterior dislocation of the humerus, which can improve visualization and access to the inferior humeral osteophytes. This approach allows better assessment of the native humeral anatomy and can provide access to the inferior capsule for release in particularly tight shoulders.

Disadvantages

The DP approach has several drawbacks. Although the role of the subscapularis in the function or stability of a reverse arthroplasty is controversial, several studies have associated subscapularis dysfunction with greater risk of instability. The DP approach requires a tendon peel, tenotomy, or an osteotomy of the subscapularis and may increase the risk of instability. In addition, visualization and instrumentation of the posterior glenohumeral structures, in particular the posterior glenoid and the greater tuberosity (in cases of fracture), can be difficult from an anterior approach. This difficulty could theoretically result in the baseplate being placed in an anterior or anteverted position. In addition, compared with the AS approach, the DP approach has been reported to have a higher incidence of nerve injury in anatomic shoulder arthroplasty. The same may be true for reverse arthroplasty.

Technique

The AS approach has previously been described. A 6-cm to 7-cm longitudinal or horizontal incision along the Langer lines is used, centered on a point just posterior to the anterolateral edge of the acromion ( Fig. 2 ). As an alternative, a longitudinal incision in line with the long axis can be used. Full-thickness soft tissue flaps are developed and the raphe between the anterior and middle thirds of the deltoid is identified. The deltoid is split between its anterior and middle thirds, starting at the anterolateral corner and extending distally for 3.5 to 4.0 cm. The anterior deltoid, roof of the subacromial bursa, and the coracoacromial ligament are detached from the anterior acromion in a single layer. A conservative acromioplasty can be performed, without shortening the overall length of the acromion. The biceps tendon is tenotomized or tenodesed, if present. The insertion of the subscapularis, assuming it is present, is preserved in all patients. The reverse prosthesis is then implanted according to the manufacturer’s recommendations. The deltoid, roof of the bursa, and the coracoacromial ligament are repaired in a single layer. Soft tissue to soft tissue figure-of-eight braided, nonabsorbable sutures are used at the acromioclavicular joint capsule and anterolateral acromial corner. Tendon-to-bone sutures are used through the acromion.

Typical skin incision for an AS approach.

Advantages

The main advantages of the AS approach are the quality of frontal exposure of the glenoid in the anteroposterior (AP) plane and the ability to preserve the subscapularis tendon. In theory, the ability to preserve the anterior soft tissues, including the subscapularis, reduces the risk of dislocation. Also in theory, preserving the anterior soft tissue structures provides a compressive effect that may reduce the need to lengthen the arm for stability, thus potentially reducing the incidence of neurologic damage or fracture of the acromion. In addition, as mentioned earlier, according to Lynch and colleagues, neurologic injury may be less likely with the AS approach. The improved visualization of the posterior aspect of the glenoid may allow more consistent glenoid preparation and baseplate placement in the AP direction. In addition, in the setting of a previous open or miniopen rotator cuff repair, the anterior deltoid can be evaluated directly and repaired or augmented with sutures, if necessary.

Disadvantages

The AS approach can make it difficult to place the glenoid baseplate in a neutral or an inferiorly tilted position. Although it is possible to start the guide pin for referencing the center of the glenoid baseplate at a point that is inferior enough to place the periphery of the baseplate at the inferior aspect of the native glenoid, it is difficult to angle the pin in some cases such that it is in neutral inclination because of the presence of the humerus. In theory, the inability to place the baseplate in an optimal position can result in increased rates of scapular notching. In addition, because the AS approach requires detachment and repair of the anterior deltoid, there is a risk of deltoid dehiscence or weakening (mechanical or neurologic damage to the distal branches of axillary nerve) that may manifest in postoperative pain or dysfunction. In addition, the AS approach is not extensile, which limits exposure of the humerus.

Review of the Literature

Successful results have been reported with reverse arthroplasties performed through both AS and DP approaches. No study has reported significant differences in patient-reported outcomes based on surgical approach. Despite this, some studies have highlighted differences in implant positioning, scapular notching, and postoperative complications.

Levigne and colleagues reported on 326 consecutive patients (337 shoulders) who underwent reverse arthroplasty (Grammont-designed prosthesis) via a DP approach (n = 267) or an AS approach (n = 70) at mean 47-month follow-up. The investigators correlated notching with arthroplasties implanted using an AS approach compared with a DP approach (86% vs 56%; P <.0001). They concluded that high positioning of the baseplate and superior tilting should be avoided and that it can be more difficult to avoid these positions when using an AS approach. Melis and colleagues similarly reported on 68 reverse arthroplasties (Grammont-designed prosthesis) at mean 9.6-year follow-up and reported that a scapular notch was observed in 60 shoulders (88%) and was associated with the superolateral approach ( P = .009). Mole and colleagues performed a multicenter study of reverse arthroplasty, comparing instability, function and pain scores, scapular notching, and complications in the AS (n = 227) and DP (n = 300) approaches. In 527 reverse arthroplasties with a minimum 2-year follow-up, the postoperative instability rate was greater with the DP (5.1%) than with the AS (0.8%) approach ( P <.001). Scapular notching occurred in 74% of AS approaches and 63% of DP approaches ( P = .03). Acromial fractures occurred in 5.6% of DP approaches and 2.2% of AS approaches ( P = .02). No differences in Constant-Murley score or active mobility were found.

Ladermann and colleagues performed a retrospective, multicenter, comparative study of 109 reverse arthroplasties implanted by the DP approach and 35 by the AS approach at minimum 1-year follow-up. The investigators did not report on their complications but noted that the humeral cut by the AS approach was lower, but this was partially corrected for by the use of a thicker polyethylene insert. Whatley and colleagues reported on 3 (1.5%; 3 of 199) patients with deltoid dehiscence after reverse arthroplasty through a DP approach. All 3 patients had undergone a previous open or miniopen rotator cuff repair. The investigators hypothesized that an AS approach during reverse TSA could be useful in assessing and possibly reinforcing a deltoid origin previously damaged or repaired during miniopen or open rotator cuff repair. Much less is known regarding the incidence of deltoid dehiscence during the AS approach for reverse TSA in the absence of previous surgery.