Comparing 3D Computer-Assisted Planning With and Without Patient-Specific Instrumentation

Re:  “Comparison of 3D computer-assisted planning with and without patient-specific instrumentation for severe bone defects in reverse total shoulder arthroplasty” by Yelton MJ et al.  JSES 2024. 

This important study evaluates the effectiveness of patient-specific instrumentation (PSI) compared to standard 3D preoperative planning alone in reverse shoulder arthroplasty (RSA) for patients with severe glenoid bone defects. PSI is one of the most commonly used methods to translate a preoperative plan into surgical execution, though other technologies—including computer navigation, mixed reality, and robotics—are emerging alternatives. In general, PSI requires a several week lag time for 3D printing of the guide.  Regardless of the method, the shared goal of these technologies is accurate in vivo replication of the preoperative plan to optimize patient outcomes and reduce complications.

The Challenge of Severe Glenoid Bone Loss

Severe glenoid bone loss presents a significant surgical challenge, and patients with such deformities theoretically stand to benefit the most from precision-enhancing tools. Prior research has demonstrated that glenoid component placement becomes increasingly difficult with advanced bony wear.¹ This retrospective study analyzed 45 cases using the Stryker Blueprint 3D planning software (Stryker, Kalamazoo, MI): 22 employed PSI, while 23 did not. All patients received glenoid bone grafting, either via the BIO-RSA technique or structural grafts. In the non-PSI group, printed planning images were referenced intraoperatively held by an assistant, whereas the PSI group utilized custom guides for pin placement with the remainder of the case being similar between the groups.

Study Results: Comparing Implant Accuracy

Postoperative CT scans assessed the accuracy of component placement, specifically deviation from the planned inclination and version. Interestingly, PSI did not improve implant accuracy. Mean version deviation was greater in the PSI group (8.4° vs. 5.4°), although it only trended toward statistical significance (p = 0.054). Inclination deviation was similar between groups (5.5° PSI vs. 6.9° non-PSI). Moreover, both groups showed a high percentage of significant outliers defined as >10° deviation (20% inclination outliers and 27% version outliers), with no notable difference between the PSI and non-PSI groups. These findings contrast with existing literature demonstrating lower deviation with computer navigation² and suggest that PSI may not confer a measurable advantage in complex bony cases.

Future Outlook: PSI vs. Emerging Technologies

While prior studies on PSI have also failed to show consistent improvements in implant placement—especially in cases involving mild or moderate deformities³ —some evidence supports PSI over traditional 2D planning.⁴ As of 2025, the accurate execution of the preoperative plan remains a key goal in shoulder arthroplasty. Computer navigation has been shown to be most effective while robotics, which shows promise, is relatively new to the field.^5,6 Computer navigation has over six years of clinical use, offering improved precision with minimal additional cost or operative time.⁷

Recent outcomes studies suggest navigation may reduce complications and improve early functional results. For example, Holzgrefe et al.⁸ reported a trend toward fewer complications at two years, with similar ROM and patient-reported outcomes. Youderian et al. noted improved outcomes in reverse arthroplasty with navigation, though this benefit was not observed in retroverted aTSA cases.⁹ They also noted that navigation had functional benefits—including improved internal/external rotation and higher patient-reported scores (SST, Constant Score, Shoulder Arthroplasty Smart Score) in all included cases.

In summary, this study suggests that PSI does not significantly improve implant positioning compared to conventional 3D planning in complex RSA cases with glenoid bone loss. As surgical technologies evolve, further research is needed to confirm whether improved implant accuracy translates to better clinical outcomes and fewer complications.

 

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References:

1. 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. 2022 Jan 15;6(2):200-208.
2. Larose G, Greene AT, Jung A, Polakovic SV, Davis NZ, Zuckerman JD, Virk MS. High intraoperative accuracy and low complication rate of computer-assisted navigation of the glenoid in total shoulder arthroplasty. J Shoulder Elbow Surg. 2023 Jun;32(6S):S39-S45.
3. Iannotti JP, Weiner S, Rodriguez E, Subhas N, Patterson TE, Jun BJ. et al. Three-dimensional imaging and templating improve glenoid implant positioning. J Bone Joint Surg Am. 2015;97:651-8.
4. Kwak J-M, Jeon I-H, Kim H, Choi S, Lee H, Koh KH. Patient-specific instrumentation improves the reproducibility of preoperative planning for the positioning of baseplate components with reverse total shoulder arthroplasty: a comparative clinical study in 39 patients. J Shoulder Elbow Surg. 2022;31:1488-98.
5. Can Kolac U, Paksoy A, Akgün D. Three-dimensional planning, navigation, patient-specific instrumentation and mixed reality in shoulder arthroplasty: a digital orthopedic renaissance. EFORT Open Rev. 2024 Jun 3;9(6):517-527.
6. Twomey-Kozak J, Hurley E, Levin J, Anakwenze O, Klifto C. Technological innovations in shoulder replacement: current concepts and the future of robotics in total shoulder arthroplasty. J Shoulder Elbow Surg. 2023 Oct;32(10):2161-2171.
7. Velasquez Garcia A, Abdo G, Sanchez-Sotelo J, Morrey ME. The Value of Computer-Assisted Navigation for Glenoid Baseplate Implantation in Reverse Shoulder Arthroplasty: A Systematic Review and Meta-Analysis. JBJS Rev. 2023 Aug 24;11(8).
8. Holzgrefe RE, Hao KA, Panther EJ, Schoch BS, Roche CP, King JJ, Wright JO, Wright TW. Early clinical outcomes following navigation-assisted baseplate fixation in reverse total shoulder arthroplasty: a matched cohort study. J Shoulder Elbow Surg. 2023 Feb;32(2):302-309.
9. Youderian AR, Greene AT, Polakovic SV, Davis NZ, Parsons M, Papandrea RF, Jones RB, Byram IR, Gobbato BB, Wright TW, Flurin PH, Zuckerman JD. Two-year clinical outcomes and complication rates in anatomic and reverse shoulder arthroplasty implanted with Exactech GPS intraoperative navigation. J Shoulder Elbow Surg. 2023 Dec;32(12):2519-2532.