Plain shoulder radiographs are useful to exclude glenohumeral osteoarthritis and advanced rotator cuff arthropathy adaptations (Hamada grade ≥ 3), both of which are contraindications for performing a muscle tendon transfer. Radiographs are often normal with posterosuperior cuff tears without cuff tear arthropathy adaptations. Radiographs are also helpful in the evaluation of bony deformity and preexisting hardware.

Computed tomography (CT) scans are primarily used to evaluate bony deformity and the degree of arthritic changes. Soft tissue quality such as rotator cuff muscle fatty infiltration can also be ascertained with CT scans. CT arthrography is another valuable modality that is comparable with MRI in determining the presence of cuff deficiency especially in the presence of prior hardware. Fatty atrophy and muscle quality can be evaluated on the sagittal CT images with the use of the Goutallier grading system.⁶ Irreparability is often associated with Goutallier grade 3 or 4.

Magnetic resonance imaging (MRI) is considered the gold standard imaging modality for assessing rotator cuff tears and muscle quality (Figure 18-1). T2-weighted images best appreciate the size of the rotator cuff tears, whereas T1-weighted images best evaluate the muscle quality and fatty infiltration. On the T2-weighted coronal sections, the degree of retraction can be measured for the supraspinatus, infraspinatus, and teres minor tears. The T1-weighted sagittal sections are best to evaluate the degree of fatty infiltration in the rotator cuff muscles. Muscle quality and fatty atrophy can be ascertained on MRI sagittal images by using the Fuchs grading system, which is adapted from the Goutallier on CT scans.⁷ The tangent sign of Zanetti can be measured on sagittal images, which consists of drawing a line from the coracoid to the scapular spine.⁸ Significant fatty atrophy of the supraspinatus is indicated by failure of the line to transect the supraspinatus. MRI with arthrogram is another imaging modality that can be helpful in evaluating the rotator cuff with a history of prior repair.

The procedure can be performed in either a beach chair position or a lateral decubitus position. The affected arm and back are then prepped and draped in the usual sterile fashion, and the patient receives appropriate antibiotics intravenously preoperatively as prophylaxis against infection. It is crucial to ensure adequate exposure to the back, with draping a few centimeters medial to the scapular medial border (Figure 18-2). The shoulder is positioned in slight flexion to make the scapula more prominent for accurate skin marking and subsequent lower trapezius tendon harvesting.

A horizontal incision of approximately 6 cm is made parallel and a few centimeters distal to the scapular spine. The incision should be 2 cm medial and 4 cm lateral to the medial scapular border.

Dissection is carried until the subcutaneous fat is encountered and skin flaps are elevated (Figure 18-3). Prior to cutting through the subcutaneous fat, one can visualize the anatomical region as a triangle to make the lower trapezius tendon harvest a facile procedure. The medial limb of the triangle is the lower trapezius tendon, and the lateral limb is the posterior deltoid. The floor of the triangle is the infraspinatus fascia. One should start by cutting through the fat overlying the floor of the imaginary triangle until the glistening fascia of the infraspinatus is encountered (Figure 18-4). Identifying the infraspinatus fascia ensures that one has not inadvertently cut through the lower trapezius tendon or the posterior deltoid. The surgeon can then undermine the lower trapezius tendon just medial and superficial to the exposed infraspinatus fascia, thus elevating the “medial limb of the triangle” (Figure 18-5). Subsequently, attention should be shifted toward releasing the insertion of the lower trapezius tendon from the medial scapular spine (Figure 18-6). The surgeon can start from the apex of the imaginary triangle, which is the most lateral and proximal part of the undermined lower trapezius tendon in the previous step. Afterward, one can reliably use electrocautery to elevate the lower trapezius from the medial scapular spine in a lateral-to-medial direction by staying on the bone on the scapular spine. It is important to remain on the center of the scapular spine while elevating to avoid cutting through the lower trapezius tendon inferiorly or cutting through the middle trapezius superiorly. Clearing superficial fascia and fat allows the surgeon to see a raphe between the lower and middle trapezius musculature, which can be opened to preserve the middle trapezius and its insertion. Once the whole lower trapezius insertion is elevated, the tendon and muscle are usually tethered to subcutaneous tissue peripheral and to the deep infraspinatus fascia (Figure 18-7). Releasing the tethering points must be performed gently, and one should minimize finger dissection to avoid bleeding. One should avoid dissecting medial to the scapular border on the deep aspect of the lower trapezius tendon as the spinal accessory nerve is one to two fingerbreadths away, whereas dissection superior to the lower trapezius tendon is always safe. One can finally confirm a successful harvest by looking at the deep surface of the harvested muscle tendon, and one should identify a clear tendinous structure. If one cannot see a clear tendinous structure, then the surgeons have either cut through the tendon itself or harvested part of the muscular middle trapezius combined with the lower trapezius. The latter scenario is less worrisome. Finally, the lower trapezius tendon end is whipstitched, which facilitates in tendon retraction at the end of the procedure when performing the Achilles tendon weave with the lower trapezius tendon (Figure 18-8).