Correlation of Preoperatively Planned Humeral Component Size and Actual Implanted Size: A Retrospective and Prospective Evaluation of Anatomic and Reverse Shoulder Arthroplasty

The aims of the study were to (1) evaluate the correlation of planned humeral component diameter with implanted humeral component diameter for reverse total shoulder arthroplasty (rTSA) and (2) to evaluate the correlation of planned humeral components with executed humeral components for stemless anatomic TSA.

Four shoulder surgeons participated in two phases of the study. In the retrospective arm, 3 months of TSA and rTSA cases which were completed with preoperative computed tomography-based planning, but without any humeral planning, were replanned using humeral planning, and the components from the virtual planning compared to the implanted components. In the prospective arm, 3 months of TSA and rTSA cases were prospectively planned by each surgeon. The planned and implanted components were similarly compared.

Ninety-seven rTSAs were included (50 retrospective, 48 prospective). In the retrospective analysis, in 60% of cases, the rTSA stem diameter was within one size of the plan; in 84%, it was within two sizes; in 90%, it was within 3 sizes. In the prospective analysis, the rTSA stem diameter was within one size in 73% of cases; in 90% within 2 sizes, and in 94% within 3 sizes (P > .05 all comparisons). The cup diameter was always within one size of the plan; it matched in 84% of the retrospective cases and 90% of the prospective cases (P > .05). Seventy-seven TSAs were included (33 retrospective, 44 prospective). For prosthetic head diameter, in the retrospective analysis, it was an exact match in 52% of patients, within one size in 85% and within two sizes in 100%. In the prospective analysis, the diameter was an exact match in 57%, within one size in 86% and within two sizes in 100% (P > .05 all comparisons). The thickness of the prosthetic component was a match to the plan in 88% of the retrospective cases and 86% of prospective cases (P > .05).

For the utilized planning software and implants, humeral planning for rTSA affords some predictability for stem diameter regardless of whether assessed retrospectively or prospectively, with 84%-90% of cases within two diameters of the plan. The inlay humeral cup diameter was an exact match to the plan in 84%-90% of cases. For stemless anatomic TSA, the humeral component diameter was an exact match to the plan in 52%-57%, but within one size in 85%-86% of cases. There were no significant differences if the planning was performed retrospectively or prospectively.