Based on the relatively small sample size and no prior basis to assume the variables analyzed form a normal distribution, we used nonparametric tests to assess whether there were any statistically significant differences. To evaluate differences between preoperative and postoperative variables, a Wilcoxon signed-rank test was used, whereas a Wilcoxon rank-sum test was used to determine if any pre-, intra-, or postoperative variables correlated with outcomes. Medians and interquartile ranges were used to describe the central tendency and dispersion for the variables under study. Statistical significance was set at the 0.05.

The rationale behind this procedure has been outlined in detail in our previous work [1–4]. The natural horizontal balance of the shoulder involves four internal rotator muscles (latissimus dorsi, teres major, pectoralis major, and subscapularis) and only two external rotator muscles (infraspinatus and teres minor). As a superior rotator cuff tear extends posteriorly, the integrity of the external rotators is compromised. In this situation, the key muscle maintaining horizontal shoulder balance is the teres minor. When this muscle becomes torn, atrophied, or fatty infiltrated, there is no other muscle available to compensate for active external rotation.

An RSA medializes and lowers the humerus, placing the deltoid at maximal mechanical advantage to compensate for the deficient rotator cuff. While this results in restoration of active anterior elevation and abduction (vertical muscle balance), it is ineffective in restoring active external rotation (horizontal muscle balance) when both the infraspinatus and teres minor are functionally absent. In previous series, the presence of atrophy or fatty infiltration of the teres minor has proven to be a negative prognostic factor for outcomes of RSA in cuff tear arthropathy patients [12–15]. Performing an LD/TM transfer restores the horizontal balance of the shoulder by transforming two of the internal rotators into external rotators (Fig. 26.1). In other words, the ratio of internal versus external rotator muscles is improved from 4 versus 0 to 2 versus 2. Combining the two procedures (RSA + LD/TM transfer) simultaneously restores both planes of motion (Fig. 26.2).

All procedures were performed by the senior author (PB) or under his direction through a deltopectoral approach in the beach-chair position. The incision is extended distally from that of a standard RSA, allowing release of the upper half of the pectoralis major tendon. All patients with an intact biceps tendon at the time of surgery also underwent a biceps tenodesis. The latissimus dorsi and teres major tendons are identified posterior to the pectoralis and released from the humerus. Care is taken to identify and protect the radial and axillary nerves during mobilization of the transferred tendons. Four heavy non-absorbable sutures are used to capture the latissimus and teres major tendons to facilitate transfer and fixation. A “tunnel” is created through blunt dissection posterior to the humerus to allow for tendon passage. Our preference is to prepare the transfer prior to performing the RSA. Once the final RSA is implanted, the transferred tendons are secured to the humerus. The patient is then immobilized in a position of 30° abduction and 30° external rotation for six weeks.

Our early practice was to transfer the two tendons to the anterolateral aspect of the humerus, bringing the two tendons to the lateral border of the bicipital groove to maximize the possible excursion that could result in external rotation. However, we had several patients who complained of an overtensioning effect that significantly limited internal rotation and prevented them from performing basic daily functions, such as manipulating the zipper on their pants. In some female patients, we also noted that the two tendons were weak (particularly the teres major, which has very little tendon at its humeral insertion) and difficult to reattach to the bone. These concerns led us to modify our technique through the years by: (1) harvesting the two tendons with a periosteal flap to reinforce the tendon-to-bone repair, (2) securing the transferred tendons through transosseous drill holes to provide the additional security of a bone bridge, and (3) transferring the combined tendons to the lateral margin of the humerus, (i.e., a more posterolateral location) to decrease the restriction on internal rotation.