Fig 1.
L1 fracture illustration shows that a middle portion of the L1 vertebral body was removed and a vertical osteotomy was made to create defect of the L1 for the fracture model.
A dead weight was dropped to the top of T11 with a rubber cushion protection to prevent direct impact on the T11 causing fracture.
Fig 2.
SSPI (Moss Miami System) combined with Trans-Endplate Pedicle Pillar System (TEPPS).
A, A pair of strain gauges mounted on the pedicle screw measures the screw bending moment. B, The pillar tip has a pin-foot that can be anchored into the endplate to avoid pillar sliding. The pillar was connected to the SSPI through a pillar connector.
Fig 3.
Pillar Insertion of the Trans-Endplate Pedicle Pillar System.
A, Spine sagittal plane of the pathway of the pillar insertion. B, Cross section of the pedicle (coronal plane) shows its oval shape. C, Longitudinal section of the pedicle and pillar after insertion. D, Pillar insertion landmarks: inferior pillar (right) was advanced obliquely from the intersection of the vertical line at the lateral border for the superior articular process with the horizontal line at the upper margin of the transverse process, and the superior pillar was inserted obliquely from the intersection of the vertical line at the lateral border for the superior articular process with the horizontal line at the low margin of the transverse process.
Fig 4.
Radiograph of SSPI+TEPPS (Moss Miami System Combined With Trans-Endplate Pedicle Pillar System).
Radiograph of fractured spine in L1 reveals SSPI+TEPPS instrumentation. Left, Lateral view shows the upper endplate pillar (1a) with its connector (2a) and the lower endplate pillar (1b) with its connector (2b). Right, Anteroposterior view shows the upper endplate pillar (1a) with its connector (2a) and the lower endplate pillar (1b) with its connector (2b).
Fig 5.
Custom-Made Spine Testing Apparatus.
A 7.5-Nm moment was applied to the spine during flexion/extension, lateral bending, and axial rotation. Segmental motion was measured using the Optotrak Certus video-based data acquisition system (Northern Digital Inc, Waterloo, Ontario, Canada).
Fig 6.
Sequence of the 4 Test Conditions.
From left to right: 1) intact spine; 2) fractured spine with SSPI fixation (SSPI-1); 3) fractured spine with SSPI+TEPPS (Moss Miami System combined with Trans-Endplate Pedicle Pillar System) fixation; and 4) fractured spine with SSPI fixation again with pillar withdrawn (SSPI-2).
Fig 7.
The mean peak spine motion from T12 to L2 in flexion/extension, lateral bending, and axial rotation for each of the 4 test conditions (intact; first test of SSPI-1 [Moss Miami System] alone; SSPI+TEPPS [Moss Miami System combined with Trans-Endplate Pedicle Pillar System]; and second test of SSPI-2 alone after removal of pillar). Asterisk (*) indicates a significant difference from intact spine (P < .001); pound sign (#) indicates a significant difference from SSPI+TEPPS (Moss Miami System combined with Trans-Endplate Pedicle Pillar System) fixation (P < .001); and dagger (†) indicates a significant difference from SSPI-1 (first test of SSPI System alone) (P < .001).
Fig 8.
Range of Motion in Flexion and Extension.
Mean of peak spine motion from T12 to L2 in flexion and extension for each of the 4 test conditions: (intact; first test of SSPI-1; SSPI+TEPPS; and second test of SSPI-2 alone). Asterisk (*) indicates a significant difference from the intact spine (P < .001), and pound sign (#) indicates a significant difference from SSPI+TEPPS (P < .001). For expansion of abbreviations, see Fig 6 legend.
Fig 9.
Bending Moment on Pedicle Screws During Flexion and During Lateral Bending.
Mean peak moment applied to pedicle screws during flexion and lateral bending. Asterisk (*) indicates a significant difference from intact spine (P < .001). For expansion of abbreviations, see Fig 7 legend.