3D CT planning is a resource-consuming preoperative exercise, the primary goal of which is to help guide the placement of the glenoid component in a pre-determined position. It is currently used in cases of complex pathoanatomy as well as in routine cases of glenohumeral arthritis.

The appropriate use and clinical effectiveness of this technology for different glenoid pathologies have not been rigorously evaluated.

The authors of The Influence of Computed Tomography Preoperative Planning on Clinical Outcomes after Anatomic Total Shoulder Arthroplasty: A Matched Cohort Analysis sought determine the effectiveness of 3D CT planning in improving the clinical outcomes of anatomic total shoulders (aTSA).

Using a multicenter shoulder arthroplasty registry, they identified patients having two year clinical followup after aTSA. The patients of seven surgeons were included. Surgeon preferences differed with respect to subscapularis management (peel vs lesser tuberosity), type of glenoid component (vault lock vs pegged vs keeled), use or non-use of 3D CT planning, and use or non-use of patient specific instrumentation (PSI).

Those cases in which 3D CT planning was used constituted a "study" group. Patients not having 3D CT planning were matched to the study patients 1:1 based on age +/- 3 years, sex, and preoperative ASES score within 10 points. Matching for other variables, such as the type of preoperative glenohumeral pathoanatomy, surgeon identity, technique of subscapularis management, and type of glenoid component used was not carried out because there were insufficient potential control patients.

The study group consisted of 84 patients with 3D CT preoperative planning (51 with PSI, 33 without) and 84 matched control patients without CT-based planning. A comparison of these two groups is shown below. Improvement from baseline for the ASES was statistically significantly greater in the CT-based planning group compared to matched controls; however the average amount of improvement (6.4) failed to meet the threshold for clinically significant improvement (the minimal clinically important difference for the ASES score is 17).

Within the 3D CT cohort, there were no significant differences in PROs or ROM between aTSAs performed with or without PSI.

The authors concluded that the clinical significance of these finding is unclear, as the differences failed to meet a clinically significant threshold.

Comment: One philosophy in total shoulder arthroplasty is to use 3D CT planning and patient specific software to guide "correction to normal anatomy" of preoperative glenohumeral pathoanatomy using eccentric removal of glenoid bone

and/or glenoid component augmentation.

Another philosophy is to ream the glenoid bone only to the extent needed to create a single concavity, accepting some glenoid retroversion and preserving as much glenoid bone stock as possible; this approach is based on intraoperative observation rather than on preoperative 3D CT planning.

Extensive clinical research will be required to find the balance between these two philosophies in optimizing the long term outcomes for patients with glenohumeral arthritis. Specifically, it will be important to determine whether certain patients with specific pathoanatomies may achieve clinical benefit from the added resources required for 3D CT planning.

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