Intrasurgeon and intersurgeon variability in shoulder arthroplasty planning was examined using planning data from 9 surgeons on 49 cases. Results showed: - Intrasurgeon variability in implant choice, version and inclination corrections varied within each surgeon between initial and repeat planning. - Intersurgeon variability was high, with wide differences between surgeons in implant choices and version/inclination corrections for the same cases. - While average differences were small, individual case differences could be large. Consistency was highest when surgeons followed set planning rules. - Variability exists because there is no consensus on ideal reconstructive goals, and surgeons can achieve similar outcomes through different approaches. Clinical implications of variability require further study.

1. Implant Usage Variability
with Exactech GPS
Moby Parsons, MD
Exactech Clinical Evaluators’ Meeting
Nashville, TN, 8/2/2019

2. Introduction
• Planning software is widely available and gaining popularity as most
systems now offer this option
• As yet no consensus on “explicit/understood principles” by which to
guide planning
• Acceptable residual retroversion
• When to bail to RTSA in the cuff-intact shoulder
• Relevance of posterior subluxation in guiding correction
• Parameters for augment use
• Etc…

3. Introduction
• Other parameters that must be considered
• Percent backside contact
• Minimizing bone loss
• Achieving fixed degree of version correction
• Optimizing impingement free range of motion
• Preventing peg or cage perforation.
Trends but no
consensus on
which of
these is most
important

4. Which is Better or Are They Both Right?
More in line with FA
Shifted anteriorly to accommodate cage in vault
More retroverted (? is -5 normal)
More centered on face
8° Augment Standard

5. Natural Retroversion -9°
8° Augment Standard
Less bone loss to correct version
Cage abuts back of vault (? Deflection)
More bone removal anterior glenoid
Better cage position in vault

6. Objective
• Determine inter- and intrasurgeon variability for both ATSA and RTSA
for a cohort of real cases representing a spectrum of pathology
• Version
• Inclination
• Implant type/size
• Face position

7. Methods
• 50 cases submitted for actual planning
• 1 excluded due to extreme deformity = 49 cases
• 9 surgeons planned all 49 cases for both ATSA and RTSA
• No specific guidelines given: do what you think is best
• 4-6 weeks later planning repeated with same cases
• Each Round: 441 ATSA; 441 RTSA
• Total: 882 ATSA; 882 RTSA

8. Intrasurgeon Variability = within surgeons
• Differences in baseplate selection between Rounds 1 and 2
• Differences in version and inclination correction
• Differences in glenoid face position
• Pearson Correlation Coefficients
• -1 = negative correlation
• 0 = no correlation
• 1 = positive correlation
Usually 0.5 is the “meaningful” threshold

9. Bland Altman Plots: compare 2 measurements
of the same variable
• Y axis: difference between rounds 1 and 2
• X axis: average of rounds 1 and 2
SD x 1.96
SD x 1.96
Outliers
Limits of Agreement: the wider the
spread the less agreement between
measurements
Variability Around
The Mean

10. Intersurgeon Variability = between surgeons
• Differences in baseplate selection for each case
• Differences in version and inclination correction for each case
• Average thresholds for augmentation
• Interclass Correlation Coefficients
• -1 = negative correlation
• 0 = no correlation
• 1 = positive correlation

11. Results: Intrasurgeon Variability
ATSA Variable Estimate CI Lower CI upper
Version 0.17 0.08 0.26
Inclination 0.53 0.46 0.60
RTSA Variable Estimate CI Lower CI upper
Version 0.34 0.25 0.42
Inclination 0.30 0.22 0.39

12. Intrasurgeon Variability ATSA
23
17
0
5
10
15
20
25
30
35
40
Surgeon
1
Surgeon
2
Surgeon
3
Surgeon
4
Surgeon
5
Surgeon
6
Surgeon
7
Surgeon
8
Surgeon
9
Average
% Different Implant and Size Between Rounds for ATSA
% Different Implant % Different Size

13. Intrasurgeon Variability ATSA
49 48
0
10
20
30
40
50
60
70
80
Surgeon
1
Surgeon
2
Surgeon
3
Surgeon
4
Surgeon
5
Surgeon
6
Surgeon
7
Surgeon
8
Surgeon
9
Average
% Different Version and Inclination Between Rounds
% Different Version % Different Inclination

14. Intrasurgeon Variability: ATSA
2.4
7.5
0
2
4
6
8
10
12
Surgeon
1
Surgeon
2
Surgeon
3
Surgeon
4
Surgeon
5
Surgeon
6
Surgeon
7
Surgeon
8
Surgeon
9
Average
Average and Max Version Diff b/t Rounds ATSA
Avg. Difference Max Difference

15. Different Thresholds for Augment Use ATSA
7.5
8.7
6.5
5
7.3
6.6
5.2
6.5
7.7
6.8
15.1
16
12.5
13
13.6
11.2 11.2
13.3
10
12.9
23.3
22.6
22
19.9
21.5
19.9
17.1
20.4
18.5
20.6
0
2
4
6
8
10
12
14
16
18
20
22
24
Surgeon
1
Surgeon
2
Surgeon
3
Surgeon
4
Surgeon
5
Surgeon
6
Surgeon
7
Surgeon
8
Surgeon
9
Average
Average Retroversion Angle for Implant Selection
Standard 8° Posterior Augment 16° Posterior Augment
Standard: -5 to -9°
8° Augment: -10 to -16°
16° Augment: -18 to -23°

16. Intrasurgeon Variability ATSA
36
27
37
0
10
20
30
40
50
60
Surgeon
1
Surgeon
2
Surgeon
3
Surgeon
4
Surgeon
5
Surgeon
6
Surgeon
7
Surgeon
8
Surgeon
9
Average
% Difference in Glenoid Face Position Between Rounds
Difference A/P Difference S/I Difference Depth

17. Intrasurgeon Variability Version RTSA
49%
26%
28%
0%
10%
20%
30%
40%
50%
60%
70%
Surgeon
1
Surgeon
2
Surgeon
3
Surgeon
4
Surgeon
5
Surgeon
6
Surgeon
7
Surgeon
8
Surgeon
9
Average
% Different Version, Inclination and Implant b/t Rounds
% Different Version % Different Inclination %Different Baseplate

18. Intrasurgeon Variability RTSA
2.2
8.1
0.0
2.0
4.0
6.0
8.0
10.0
12.0
Surgeon
1
Surgeon
2
Surgeon
3
Surgeon
4
Surgeon
5
Surgeon
6
Surgeon
7
Surgeon
8
Surgeon
9
Average
Difference in Avg. and Max Version Between Rounds
Avg Version Diff Max Version Difference

19. Heatmap of Intrasurgeon Variability
RTSA
Version
ATSA
Version
RTSA
Inclin
ATSA
Inclin
Pearson Correlation Coeffecients

20. Bland Altman: RTSA Version • Consistency decreases as
version moves from 0 to -5°
• ….but then increase around
-8 °

21. Version

22. Bland Altman: ATSA Inclination
• Consistency decreases as
inclination moves from 0 to 4°
• ….but then increase around 8 °
Average of Rounds Average of Rounds
• Tight Standard Deviation=
consistent planning to a rule

23. Inclination
RTSA inclination consistency is the highest

24. Intersurgeon Variability
ATSA Characteristic Method Kappa
Augment Light's Kappa 0.36
Size Light's Kappa 0.36
Version ICC (C,9) 0.8
Inclination ICC (C,9) 0.37
RTSA Characteristic Method Kappa
Baseplate Light's Kappa 0.25
Version ICC (C,9) 0.43
Inclination ICC (C,9) 0.42

25. Intersurgeon Variability ATSA
68
37
70
52
22
11
0
10
20
30
40
50
60
70
80
90
100
Surgeon
1
Surgeon
2
Surgeon
3
Surgeon
4
Surgeon
5
Surgeon
6
Surgeon
7
Surgeon
8
Surgeon
9
Average
Percent Implant Use by Surgeon
Standard 8° Posterior Augment 16° Posterior Augment

26. Intersurgeon Variability RTSA
68%
21%
67% 32%
32%
16%67%
27%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Percent Baseplate Use by Surgeon
% Standard Baseplate % 8° Posterior Augment % 10° Superior Augment % PostSupAugment
Surgeon 1 Surgeon 2 Surgeon 3 Surgeon 4 Surgeon 5 Surgeon 6 Surgeon 7 Surgeon 8 Surgeon 9 Average

27. Intersurgeon Variability ATSA
-1.80
-3.00
0.00
-1.60
-3.40
-1.60 -1.40
-2.10
-0.70
1.68 1.50
2.90 2.60 2.70
2.10 2.30
3.00
0.20
-4.00
-3.00
-2.00
-1.00
0.00
1.00
2.00
3.00
4.00
Surgeon
1
Surgeon
2
Surgeon
3
Surgeon
4
Surgeon
5
Surgeon
6
Surgeon
7
Surgeon
8
Surgeon
9
Average Planned ATSA Version and Inclination
Planned Version Planned Inc

28. 0
10
20
30
40
50
60
70
80
90
100
0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10
ATSA Correction by Surgeon
Surgeon 1 Surgeon 2 Surgeon 3 Surgeon 4 Surgeon 5 Surgeon 6 Surgeon 7 Surgeon 8 Surgeon 9
Two Peaks
• 0°
• 4/5°

29. Intersurgeon Variability RTSA
-1.6
-1.2
0
-2.3
-2.1
-2.8
-3.5
-2.9
-0.5
-0.1
0.1 0
-0.1 -0.1 -0.1
-0.9
2
0.1
-4.0
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
Surgeon
1
Surgeon
2
Surgeon
3
Surgeon
4
Surgeon
5
Surgeon
6
Surgeon
7
Surgeon
8
Surgeon
9
Average Planned Version and Inclination
Average Version Average Inclinication

30. 0
10
20
30
40
50
60
70
80
90
100
0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10
RTSA Correction by Surgeon
Surgeon 1 Surgeon 2 Surgeon 3 Surgeon 4 Surgeon 5 Surgeon 6 Surgeon 7 Surgeon 8 Surgeon 9
• Still a penchant for 0
• More variability across the spectrum

31. Baseplate Similarity Frequency by Case
Maximum N Average Average
Similar Version Inclination
18 2 -6.4 -4.3
17 1 -19.6 -4.0
16 2 -15.7 -9.8
14 2 -16.5 -8.0
13 6 -17.5 -1.7
12 6 -9.3 2.2
11 4 -12.8 5.1
10 9 -12.2 6.1
9 8 -9.4 5.2
8 3 -5.5 4.8
7 5 -8.1 7.2
6 1 -8.3 3.9
Variability is not a function of case complexity

32. Conclusions
• Both Intra and Intersurgeon variability are low for version and
inclination except in the case of Surgeon 3 who planned all cases to
0/0°
• Implant choice varied widely both within and between surgeons
• While average differences in version and inclination between rounds
were small, individual differences on a case by case basis were large
with variable consistency between surgeons

33. Conclusions
• Consistency was highest for measures were tend to agree most on
(superior baseplate tilt is bad)
• Consistency was highest for surgeons who have set rules for how they
plan cases (Surgeon 3: 0/0)
• We do not know whether inconsistency translates into different
outcomes

34. Conclusions
• Surgeons can achieve a relatively narrow range of reconstructive goals
using a wide variety of reconstructive options
• This data makes it currently unclear if we should be trying to establish
guidelines by which to achieve an ideal plan as we do not agree on
what that should be
• Clinical correlation will be difficult with such variability unless we
conform to specific rules like Surgeon 3

35. Thank You