3D CT Preoperative Planning in Shoulder Arthroplasty: Differences in Industry Technician and Surgeon Planning

Given the increased use and availablilty of preoperative planning in shoulder arthroplasty, improved knowledge of how surgeons plan, the ability to execute the plan, and factors associated with planning is needed.


Joseph J. King, MD
UF Health Orthopaedics and Sports Medicine Institute

Hartzler and colleagues1 evaluated the rates of surgeon agreement compared to an industry technician team regarding the 3-dimensional preoperative plan for placement of shoulder arthroplasty components in 6,483 cases (aTSA and rTSA).  The industry technicians used some general principles to follow when creating the plan and were trained in this process.  Aditionally, all plans underwent a peer-reviewed process prior to be accepted by the team.  The patient-specific instrumentation used in this study utilized a reusable device with 5 points of contact on the glenoid surface.  This device targets the central glenoid pin used in this system.  This study focused on the central glenoid pin placement regarding version and inclination.

The authors demonstrated that there was a moderate rate of surgeon acceptance of the plan (66% version, 72% inclination, and 55% for both).  Notably, 45% of plans showed at least version or inclination were not accepted by the surgeon with 18% of cases having neither plan accepted by the surgeon.  While in a “majority” of cases the plan was accepted, this still shows a relatively high lack of acceptance of the plan that was generated using general guidelines.

Interestingly, the authors noted that on univariate analysis, as the surgeon’s case count increased, their acceptance of technician planned version decreased.  This suggests that with experience using the preoperative planning system or just surgeon experience caused the surgeons to not accept the standardized plan.  This highlights the fact that experienced surgeons likely use other factors besides the general guidelines when considering preoperative glenoid planning.  This study adds to the literature regarding surgeon variability in preoperative planning in differing clinical scenarios. 2,3

The authors demonstrated that there was a moderate rate of surgeon acceptance of the plan (66% version, 72% inclination, and 55% for both). 6

Increasing native glenoid version was another factor on univariate analysis that caused decreased surgeon agreement with the technician planned implant version.  Again, this shows that in difficult cases (with significant glenoid wear), other factors besides the general guidelines are used by surgeons for planning implant version.

Limitations of this study include the fact that only glenoid version and inclination were assessed.  Change in the inferior/ superior or anterior/ posterior position of the central pin as well as the planned depth of reaming was not assessed.  In addition, while understanding planning is important, in vivo execution of the plan and/or intraoperative acceptance of the patient specific instrumentation guide was not assessed.  Studies have shown that even with preoperative planning, the in vivo execution of the plan still can be off a significant amount of the time.4,5

Of note, some of the same authors found that different preoperative planning software leads to different measurements in native version and inclination whereas the surgeons in that study had relatively high inter-observer reliability, demonstrating that measurements of even native version and inclination by preoperative planning softwares differ.6

The authors do mention the risks of anchoring bias and authority bias when accepting or changing the plan in these scenarios.  They make a good point that maybe it is better to let the surgeon plan from the beginning without industry input to avoid these biases, although this was not evaluated in this study.  The authors caution surgeons to avoid blind acceptance of the industry technician preoperative plan in shoulder arthroplasty given the findings of this study.  I agree with this assessment as there are many factors to consider when planning including remaining glenoid bone stock, location of central pin vault penetration, backside support of the implant, ease of implant placement, and availablilty of glenoid augments, amongst other factors all play a role in surgeon preoperative planning.


  1. Hartzler RU, Denard PJ, Griffin JW, Werner BC, and Romeo AA. “Surgeon acceptance of an initial 3D glenoid preoperative plan: rates and risk factors.”  J Should Elb Surg.   30: 787-94.
  2. Greene A, Cheung E, Polakovic S, Hamilton M, Jones R, Youderian A, et al. Inter-surgeon variability in using 3D planning software for reverse total shoulder arthroplasty: an analysis of 360 cases. Orthop Proc. 101-B:64.
  3. Parsons M, Greene A, Polakovic S, Byram I, Cheung E, Jones R, Papandrea R, Youderian R, Wright T, Flurin PH, Zuckerman JD. Assessment of surgeon variability in preoperative planning of reverse total shoulder arthroplasty: a quantitative comparison of 49 cases planned by 9 surgeons. J Should Elbow Surg.  29(10): 2080-88.
  4. Hao KA, Sutton CD, Wright TW, Schoch BS, Wright JO, Struk AM, Haupt ET Leonor T, King JJ. Influence of glenoid wear pattern on glenoid component placement accuracy in shoulder arthroplasty.  JSES Int.  6(2): 200-8.
  5. Schoch BS, Haupt E, Leonor T, Farmer KW, Wright TW, King JJ. Computer navigation leads to more accurate glenoid targeting during total shoulder arthroplasty compared with 3-dimensional preoperative planning alone. J Should Elbow Surg.  29(11): 2257-63.
  6. Erickson BJ, Chalmers P, Denard P, Lederman E, Horneff G, Werner BC, Provencher M, Romeo AA. Does commercially available shoulder arthroplasty preoperative planning software agree with surgeon measurements of version, inclination, and subluxation?  J Should Elbow Surg.  30(2): 413-20.