Future directions in shoulder arthroplasty


Shoulder arthroplasty has advanced immeasurably since the first shoulder replacement was implanted by Péan in 1893. Implant designs continue to evolve and improve, as do the materials from which these designs are constructed. The reverse prosthesis has gained widespread use in the United States since 2004 and continues to evolve, with design changes introduced by many companies that manufacture a version of this semiconstrained device.

One of our personal interests in the future of shoulder arthroplasty focuses on patient-specific virtual surgery and the dynamic role of the scapula in shoulder arthroplasty.

Patient-Specific Virtual Surgery and Patient-Specific Instrumentation

Preoperative planning software enables surgeons to plan surgery virtually, including humeral and glenoid implantation. The software is typically formatted off nonarthrogram computed tomography scans to create three-dimensional reconstructions that allow glenoid morphology to be evaluated, including degrees of retroversion and percentage of humeral head subluxation ( Fig. 44.1 ). The surgeon can implant the glenoid component virtually to determine the appropriate size of the glenoid component, the backside radius of curvature, and the desired location to ensure appropriate version, seating, depth of reaming as well as to minimize glenoid perforation for anatomic shoulder arthroplasty and to find maximal bone purchase for reverse shoulder arthroplasty ( Figs. 44.2 and 44.3 ). A patient-specific guide can be created to provide reproducibility of guide-pin placement for instrumentation of the glenoid (see Fig. 44.3 ). Multiple preoperative planning software programs and patient-specific guides have been shown to improve the reproducibility of guide-pin placement for glenoid instrumention. More clinical data are needed to show an advantage in glenoid component survival or patient outcomes with or without a patient-specific guide. The future role of virtual surgery and patient-specific instrumentation will be to determine implant size and placement for each patient to optimize individual outcomes.

FIGURE 44.1, Preoperative planning software using computed tomography to determine retroversion (18 degrees; A) and superior inclination (12 degrees; B).

FIGURE 44.2, Preoperative planning software using computed tomography to determine axial (A) and coronal (B) virtual placement of the glenoid component. The green-highlighted glenoid component implies that there is no glenoid perforation, which would alternatively display as red with any glenoid perforation involving the peg(s) or keel.

FIGURE 44.3, Preoperative planning software with three-dimensional display of virtual placement of the glenoid component, with the red line indicating the entry point of the guide pin for glenoid component instrumentation (A); proposed anatomic sites on the native glenoid to place the “feet” of the patient-specific guide (B); and final three-dimensional display of the proposed guide with three anatomic “feet” located anteriorly on the guide and a single foot posteriorly on the guide (C).

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