CORR Insights®: What Are Practical Surgical Anatomic Landmarks and Distances from Relevant Neurologic Landmarks in Cadavers for the Posterior Approach in Shoulder Arthroplasty?

Where Are We Now?

Before reading the study by Bahk and Greiwe [1] in this month’s Clinical Orthopaedics and Related Research®, I wondered why we would modify or change the deltopectoral surgical approach for shoulder arthroplasty when it works so well. After reading the study, I reflected on the advantages, challenges, and potential complications of the deltopectoral approach. While this technique offers great exposure for the glenoid and the humerus for shoulder arthroplasty, to accommodate for this exposure, one of three things must occur with the subscapularis tendon: tenotomy, “peel”, or lesser tuberosity osteotomy (LTO).

Addressing the subscapularis tendon generally involves performing a tenotomy while also reapproximating the tendon to itself or the “peel technique,” which involves taking down both the capsule and tendon from the lesser tuberosity and reapproximating them through drill holes medial to the lesser tuberosity. In essence, we are medializing the tendon and improving external rotation. But those procedures come with a cost—anterior escape, which is caused by a lack of healing. That being said, the LTO technique was developed to be biomechanically stronger with bone-to-bone healing, and studies show [2-5] that healing rates do improve over the peel and tenotomy approaches. However, we are still left with a group of both nonunions (13%) and displacement of the osteotomy (7%), leading to the dreaded anterior escape and poor clinical outcomes with pain and bad shoulder mechanics in patients who undergo shoulder arthroplasty [2-5].

In the current study, Bahk and Greiwe [1] investigated a novel posterior approach for shoulder arthroplasty and noted the advantages, namely the avoidance of the subscapularis, which is an important anterior stabilizer for shoulder arthroplasty. In the standard deltopectoral anterior approach, the subscapularis must be violated either through the “peel” technique, tenotomy, or LTO. But these methods can potentially lead to instability and a poor clinical outcome. Additionally, the study details the anatomic landmark of importance for the posterior approach in shoulder arthroplasty, which is a more feasible approach for those surgeons less unfamiliar with the posterior structures of the shoulder.

By considering these two major points during the surgical decision-making process, one can anticipate (or predict) a more reproducible clinical outcome and decrease complication rate for both anatomic total shoulder arthroplasty or reverse total shoulder arthroplasty.

Where Do We Need To Go?

Once familiar with this new posterior approach, surgeons should have excellent visualization of both the humerus and glenoid, with the greatest advantage being the preservation of the subscapularis in its anatomic position. Although these are real advantages, there is a concern the posterior approach is not extensile. Surgeons must consider the possibility of a distal fracture requiring fixation with a plate or cables or with suture or wire.

Another concern is the posterior displacement of the humeral head in primary osteoarthritis of the shoulder. The pathoanatomy of shoulder osteoarthritis typically involves contracture of anterior capsular structures leading to displacement of the humeral head and posterior glenoid. Future studies should determine whether anterior capsular release from the subscapularis results in better centering of the humeral head on the glenoid at the conclusion of arthroplasty. Although I believe this would recenter the humeral head after anatomic or reverse shoulder arthroplasty, future studies should determine whether this would be the best approach.

How Do We Get There?

Once surgeons become familiar with this new posterior approach, it appears that they will have excellent visualization of both the humerus and glenoid. The advantage of this approach is the preservation of the subscapularis in its anatomic position, while also avoiding the complications associated with lesser tuberosity osteotomy, peel techniques, or tenotomy. But there are other concerns that we still need to study. In performing shoulder arthroplasty, there are times when there is a need for a more extensile approach for complications like proximal humerus fracture associated with humeral reaming or the placement of the humerus with a press fit technique. The ability to extend the incision safely for the placement of cerclage cables or other types fixation may not be possible with this new posterior approach.

A second concern with this posterior approach is the posterior displacement of the humeral head in patients with typical primary osteoarthritis of the shoulder. The pathoanatomy of primary shoulder osteoarthritis involves contracture of anterior structures such that the capsule and rotator cuff interval are adhered tightly to the subscapularis, leading to displacement of the humeral head posterior and posterior glenoid. Surgeons should address the anterior capsule release from the subscapularis in order to recenter the humeral head after either and anatomic or reverse shoulder arthroplasty.