63.1 Goals of Procedure

The primary goal of reverse total shoulder arthroplasty (RTSA) for proximal humerus fractures is to provide pain relief and range of motion sufficient for the performance of activities of daily living. A secondary goal is to perform a reliable procedure with a low chance of a secondary option (i.e., avoid hardware failure or avascular necrosis [AVN] associated with treatment of certain types of proximal humerus fractures).

63.2 Advantages

Multiple recent studies have supported functional advantages for RTSA over hemiarthroplasty in the treatment of three- and four-part proximal humerus fractures. The latter is fraught with a poor potential for tuberosity healing that can lead to substantial compromise in outcome. ¹ With RTSA, tuberosity malunion and nonunion are better tolerated by patients because the implant design allows for some preservation of active forward elevation and joint stability. ² At the same time, RTSA is actually associated with a higher rate of tuberosity healing compared to hemiarthroplasty, likely because of the medialized center of rotation, which decreases tension upon the tuberosity repair. ³ If tuberosity healing occurs, external rotation is usually retained and improves patients’ function with activities away from the body. ⁴

63.3 Indications

Whenever possible, we believe in joint preservation and aim to treat a proximal humerus fracture with conservative treatment or open reduction and internal fixation (ORIF). RTSA is considered for displaced three- and four-part fractures, head split, and fracture dislocations in patients older than 65 years ( Fig. 63.1 ). Several factors are used to determine if the fracture is repairable including bone quality, potential vascularity, and medical comorbidities. Bone quality is estimated based on cortical thickness with less than 4 mm combined proximal diaphyseal thickness corresponding to osteoporosis. ⁵ While AVN is difficult to predict in the long term, vascularity at the time of injury is likely compromised in the setting of a metaphyseal extension of the humeral head of less than 8 mm and loss of the medial hinge. ⁶ Finally, we consider medical factors such as smoking status and medical comorbidities. If vascularity is potentially compromised but the patient is in good health and has good bone quality and health, we will consider ORIF. On the other hand, if bone quality is poor and functional demand is low, we proceed with arthroplasty and choose between hemiarthroplasty and RTSA based on age. In general, for patients older than 65 years, we proceed with RTSA and for younger patients we perform hemiarthroplasty (which is rare given that most younger patients have good bone quality). Tuberosity healing is a critical step to achieve satisfactory outcomes when utilizing either a constrained or an unstrained arthroplasty for treatment of three- and four-part proximal humerus fractures ( Fig. 63.2 ). ⁷

63.4 Contraindications

Contraindications for RTSA are comparable to unconstrained arthroplasties implanted for fracture cases. Active infection is an absolute contraindication for prosthesis implantation. Young patients with good bone stock, two-part surgical neck fractures, fractures amenable to ORIF, and significant medical morbidities are relative contraindications for RTSA. Furthermore, axillary nerve palsy and acromion fractures are contraindications specific to RTSA.

63.5 Preoperative Preparation/Positioning

A thorough history and physical examination are essential to determine if the patient is a candidate for RTSA. Information such as previous history of shoulder pain and inability to raise arm overhead before the injury allow the surgeon to discuss potential function postoperatively. Neurovascular assessment is critical, as an axillary nerve palsy in the setting of RTSA could result in prosthetic instability and poor function with forward elevation. Concomitant fractures need to be considered in the preoperative workup. Acromion fractures, either traumatic or pathologic, may have higher chance of developing nonunion after RTSA secondary to lengthening of deltoid and displacement forces placed across fracture site.

Essential radiographic assessment includes true glenohumeral anteroposterior (AP; Grashey’s), scapular Y, and axillary views. A CT scan can be obtained to evaluate fracture pattern, bone quality, and rotator cuff fatty infiltration. However, we find that with good-quality radiographs, a CT scan is not necessary in most cases as the comminution and displacement requiring RTSA is usually obvious.

63.6 Operative Technique

A single-shot interscalene block is performed prior to induction of anesthesia. The patient is placed in the beach-chair position on a specialized positioner (Tenet; Smith & Nephew; Memphis, TN) at approximately 45 to 60 degrees upright. The operative side is positioned slightly to edge of the table to allow for full extension and adduction of the humerus. The operative arm is prepped, draped, and placed in a hydraulic arm holder (SPIDER; Smith & Nephew) to facilitate positioning. A Betadine occlusive drape is placed over the surgical site to eliminate the axilla from the operative field.

In displaced fractures and particularly in fracture dislocations, anatomy becomes distorted and the surgeon must search for reliable landmarks. A standard deltopectoral approach is used. The skin incision is 4 to 6 inches in length and extends from the coracoid tip toward the deltoid insertion. The dissection is carried medially to identify the cephalic vein, which is then retracted laterally with the deltoid. Once the deltopectoral interval is opened, the tip of the coracoid is the first crucial landmark that should become apparent. In fact, if one has trouble defining the interval, the coracoid tip is a good guide to finding the interval at the superior aspect of the incision. Dissection then carries lateral to the coracoid. The clavipectoral fascia is incised and the conjoined tendon is lightly retracted medially. The coracoacromial ligament is followed superolaterally to the acromion in order to establish the subdeltoid space and a Browne deltoid retractor is placed here to retract the deltoid laterally.

The next major structure that provides guidance is the biceps tendon, which is easiest to find passing beneath the pectoralis major tendon (PMT). For this reason, the superior border of the PMT is incised for 5 to 10 mm. The biceps tendon is then tenodesed to the lateral segment of the incised PMT with 2–0 Vicryl sutures. Then, the biceps is tenotomized with an electrocautery just above the tenodesis and the biceps sheath is opened to visualize the bicipital groove, which distinguishes the lesser from the greater tuberosity. The biceps release continues proximally with a curved scissors to open the rotator interval by working toward the base of the coracoid (i.e., the supraspinatus tendon is protected by avoiding cutting posteriorly) and the biceps are released from its origin. An inverted mattress suture (Fiber-Wire; Arthrex, Naples, FL) is placed in both the subscapularis and the posterosuperior rotator cuff at the bone–tendon junction. In the setting of a four-part fracture, the tuberosities will be separated. With a three-part fracture, the bicipital groove can be osteotomized with a saw or osteotome to separate the tuberosities. Finally, the humeral head is removed and saved for bone grafting later in the procedure.

Attention is now turned to further securing the greater tuberosity. Two no. 5 FiberWire sutures are passed from outside to in through the bone–tendon interface, one superiorly through the supraspinatus and one more inferiorly through the infraspinatus. As these are to be used as cerclage sutures, the limbs are tagged without removing the needle in order to facilitate for subsequent passage through the subscapularis. Passing sutures and securing control of the tuberosities is much easier if completed prior to component implantation, which decreases the working space.

Glenoid exposure in the fracture setting is usually less challenging because the displaced tuberosity fragments can be retracted. A two-pronged thin glenoid retractor is placed anteriorly along the glenoid neck, a Darrach or Fukuda retractor is placed posteroinferiorly along the glenoid to retract the greater tuberosity and proximal humeral shaft, and a mini-Hohmann retractor is placed superiorly. The remaining proximal biceps stump and the labrum are excised and the cartilage is removed from the glenoid.

Our preferred RTSA implant uses a baseplate with a combination postcentral screw (Univers Revers; Arthrex; Fig. 63.3 ). Preparation of the glenoid is performed in a cannulated fashion. While three baseplate sizes are available (S, M, and L), we nearly always place a small baseplate since this size is adequate for stability and allows for multiple glenosphere size options. Therefore, a small guide is selected, placed at the inferior aspect of the glenoid, and a guide pin is advanced into the glenoid vault. A two-step reaming process is used to create a central bone socket with an inlay to accommodate the baseplate. The baseplate is impacted into place with a cannulated impactor through which a central compression screw is placed. Two polyaxial peripheral locking screws are then placed, one inferiorly and one superiorly. A circumferential reamer is then used over the top of the baseplate to clear bone and soft tissue for the subsequent placement of the glenosphere, which is then impacted into place. Most commonly, a 36-mm glenosphere with 4 mm of lateralized offset is placed in fracture cases. For large males, we occasionally use a 39 + 4 mm glenosphere. For small females older than 80 years, we may use a neutral 36-mm glenosphere as lateralization of the glenosphere increases deltoid force requirements, which may not be ideal in older frail patients.

With the glenosphere implanted, attention is turned to the humerus, which is exposed with extension and external rotation. A Hohmann retractor is placed medially around the shaft of the humerus and a Fukuda retractor is usually used laterally (since the humeral head is absent). The implant system we use has an inlay metaphyseal cup with an option to choose between a 135- or a 155-degree humeral inclination. We routinely use the 135-degree option in order to limit scapular notching. The humerus is sequentially broached. Reaming is not necessary based on the proximal mediolateral fixation design. In approximately two-thirds of cases, the fixation design also allows us to achieve a press-fit fixation. However, if we have concern about bone quality, we place cement in order to avoid iatrogenic fracture of the shaft. Broaching is performed with the arm in approximately 20 degrees of retroversion using the forearm axis as a guide. In addition, the medial flare of the proximal neck provides a reference for version and we seek to match this flare when aiming for press-fit fixation.

Humeral height can be judged based using several factors. First, the excised humeral head can be used as a guide to estimate the amount of missing medial bone. In most cases of RTSA, this should only be a few millimeters and the medial aspect of the inlay cup should sit just above the medial proximal humeral shaft. Second, the PMT can be used as a guide as has been reported for hemiarthroplasty. ⁸ The lateral aspect of the humeral inlay usually sits at the level of the greater tuberosity. Therefore, 5 to 8 mm can be added to this to correspond to the humeral head height used for hemiarthroplasty (5.5 cm).

Once the humerus is prepped, a trial reduction is performed. The tuberosities are reduced to the shaft manually to provide a final confirmation of prosthesis height. It is important to understand that stability in a fracture setting will be slightly compromised until the tuberosities are repaired. In most cases, we use a standard polyethylene (3 or 6 mm) without an additional spacer. Overtensioning by placement of excessive spacers will decrease the chance of tuberosity healing.

Prior to placement of the final humeral component, two holes are placed in the shaft lateral to the bicipital groove with a 2.0-mm drill. A mattress suture is placed with a no. 2 Fiber-Wire such that the suture ends exit the shaft laterally. The no. 5 cerclage sutures are then retrieved and passed around the shaft so that they will surround the humeral component.

The final humeral component is then placed. In the case of cementation, a cement restrictor is placed and a hybrid cementation-impaction grafting technique, called the “black and tan” technique, is utilized. ⁴ Cement premixed with Gentamicin is prepared and delivered into the humeral diaphysis. Autogenous humeral head cancellous bone graft is used to create an interface between the area of tuberosity repair and proximal cement mantle.

Arguably the most important part of the case is tuberosity repair. Anakwenze et al in a recent meta-analysis compared active range of motion of RTSA with and without greater tuberosity repair in the fracture setting. ⁹ Both forward elevation (126 vs. 112 degrees, p < 0.0001) and external rotation (38 vs. 4 degrees, p < 0.0001) were greater with tuberosity repair. First, the two no. 5 cerclage suture ends are passed through the subscapularis just lateral to the lesser tuberosity moving from posterior to anterior. Next, a no. 2 FiberWire suture is passed through the supraspinatus and stem utilizing holes in the metaphyseal component (SutureCup). This suture is tied. This is repeated for the lesser tuberosity. Next, the suture ends from the humeral shaft are passed through the posterosuperior cuff in a figure-of-eight pattern to provide further vertical stability. Finally, the no. 5 cerclage sutures are tied and the tagging sutures for the tuberosities are tied together ( Fig. 63.4 ).