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SUPPLEMENTAL DIGITAL CONTENT 2:

Statistical Results of the Various Testing Procedures*

Statistical Test FE AR

SZ PR TL SZ PR TL

Effect of CC (small-gap fracture)

Intact ROM 0.27  0.21 0.28  0.08 21.7  2.48 0.24  0.18 0.49  0.14 7.38  2.21 L5P ROM° 2.78  2.48 2.88  2.12 2.17  2.41 23.75  8.02 4.8  2.84 12.24  4.91 L5P + CC ROM° 1.47  0.82 1.21  0.73 18.35  4.77 0.99  0.8 2.11  1.55 8.62  3.39 P value: L5P versus

L5P + CC 0.15 0.07 0.03 0.15 0.02 0.02

Power 0.26 0.5 0.34 0.23 0.58 0.35

Effect of AP with short LP

F Intact ROM° 0.53  0.4 0.33  0.11 22.98  7.67 0.22  0.07 0.72  0.57 6.4  7.46

L5P + CC + AP ROM°

0.42  0.08 0.56  0.29 16.08  3.47 0.6  0.18 0.99  0.34 9.37  2.35 L5P + CC ROM° 1.93  1.88 2.08  2.21 17.83  5.42 2.4  1.4 2.35  0.66 9.96  2.38 P value: L5P + CC +

AP versus L5P + CC

0.15 0.16 0.22 0.05 0.01 0.04

Power 0.43 0.33 0.09 0.81 0.98 0.07

Effect of AP with long L

PF Intact ROM° 0.53  0.4 0.33  0.11 22.98  7.67 0.22  0.07 0.72  0.57 6.4  7.46

L4P + CC + AP ROM°

0.41  0.12 0.34  0.14 6.09  2.32 0.6  0.34 0.76  0.36 4.97  1 L4P + CC ROM° 1.16  1.05 5.3  8.78 10.51  12.43 1.8  1.1 1.92  0.84 5.81  1.12 P value: L4P + CC +

AP versus L4P + CC

0.21 0.27 0.48 0.05 0.02 0.33

Power 0.35 0.24 0.12 0.64 0.81 0.24

Effect of number of

Intact ROM° 0.51  0.35 0.32  0.09 20.71  8.36 0.22  0.06 0.65  0.52 7.92  3.93 T1 + AP ROM° 1.03  0.13 0.42  0.17 21.68  7.9 0.65  0.28 0.33  0.13 9.79  2.5 T2 + AP ROM° 0.74  0.33 0.35  0.16 23.07  7.87 0.52  0.2 0.38  0.23 9.19  2.38 P value: T1 + AP

versus T2 + AP

0.08 0.24 0.18 0.13 0.54 0.04

screw

s Power 0.52 0.11 0.06 0.16 0.07 0.07

*Large-gap fracture unless otherwise noted; average raw relative angular motions ( standard deviation) reported for each construct; P = 0.05 for all 2-tailed, matched Student t tests; power analysis was 2-tailed and assumed normal distribution for 2 sample sizes of the particular test; boldface font indicates statistical

significance.

FE, flexion-extension motion applied by motion simulator; AR, axial rotation motion applied by motion simulator; SZ, sacral fracture zone relative primary motion (see Fig. 1, rotation X in FE); PR, pelvic ring relative primary motion; TL, total lumbopelvic complex, from L4 to left iliac wing, relative primary motion;

ROM, range of motion; P, to pelvis; CC cross-connector; AP, anterior plate; T1, single screw; T2, 2 screws;

LPF, lumbopelvic fixation.