Failure of tuberosity healing is the most common cause of poor functional outcome following hemiarthroplasty and each step in the articular replacement should be executed to optimize the tuberosity repair. Prosthetic head size and version can significantly affect tuberosity tension and thus healing. Following mobilization of the tuberosities, a prosthetic head is selected. The humeral head represents a portion of sphere. The native articular piece should be matched to a prosthetic trial based on radius of curvature, depth, and width. If the native head size falls between two trial sizes, the smaller option is chosen. Excessive offset from a head that is too big increases tension on the repaired tuberosities leading to pull off and also overtensions the joint capsule restricting motion.

The “jigsaw” method, described by Bigliani and Flatow, involves reconstructing the head–shaft relationship by reducing the native head anatomically on the shaft to create an intraoperative template for reconstruction [10] (Fig. 7.2a). It provides a reliable method for reproducing native head height. If the head piece is comminuted, it can be put together on the back table and held by K wires to produce the anatomic model. Calcar comminution can also be pieced together to recreate the native surgical neck. With the head anatomically reduced to the shaft, measurements of head height can be taken from fixed landmarks such as the pectoralis major tendon. Warner et al. established a distance of 5.6 cm from the top of the head to the upper border of the pectoralis major tendon as a reliable guideline [11]. The native head-neck reconstruction provides a more precise replication of native anatomy, although it should not deviate greatly from 5.6 cm. With the head-neck alignment defined, trials can be used to recreate this relationship (Fig. 7.2b). In situ measurements confirm proper height of the trail. If the prosthesis is placed too low, the rotator cuff and other portions of the myofascial sleeve will be too lax leading to inferior subluxation or dislocation. A prosthesis that is placed too high will lead to a painful overstuffed joint.

The jigsaw method can also help to recreate appropriate prosthetic version which is also critical to tuberosity healing. If the prosthesis is placed in excessive retroversion, internal rotation of the shoulder will create tension on the greater tuberosity whereas too much anteversion will tension the lesser tuberosity when the shoulder is externally rotated. Native retroversion can vary from 0° to 50° [12]. By recreating the native proximal humerus, native version can be accurately reproduced. Average retroversion is usually between 20° and 30° and if the reconstruction model varies too much from this guideline, the model should be reassessed [12]. Once the head height and version are established, a reduction with the trial prosthesis is performed. The tuberosities are provisionally reduced and fluoroscopic images taken (Fig. 7.3). The bone of the humeral shaft is typically osteoporotic and securing the stem with cement reduces the possibility of intraoperative fracture and later subsidence.

Union must occur between the greater and lesser tuberosity as well as between the tuberosities and the shaft. Fixation must therefore be in both the coronal as well as the sagittal planes. Wire is more durable than suture fixation, produces less slippage, and yields greater rates of healing but is more difficult to use [13]. A hybrid construct of both sutures and wires provides the benefits of both. Frankle et al. have shown that a circumferential medial cerclage decreases intrafragmentary motion and strain, and increases union rates [14]. A wire can be used for this cerclage while suture fixation can be used to fix the tuberosities to the shaft. A running, locking stitch of heavy nonabsorbable suture should be placed through the subscapularis and a second through the supra and infraspinatus. These sutures are used to secure each tuberosity to the stem. Additional heavy sutures are passed through bone tunnels in the shaft and then through cuff tendons such that they secure the tuberosities in the axial plane. The medial to lateral sutures are tied first followed by the inferior to superior sutures. This prevents over-reduction of the greater tuberosity below its ideal position of approximately 8 mm below the head. A cerclage wire through the stem and around the tuberosities is passed before the sutures are placed but is the final piece that is tightened. Bone graft from the excised head should be used routinely and may also increase rates of tuberosity healing. Intraoperative imaging is then used to confirm acceptable reduction of the tuberosities.