Motion preservation surgery for scoliosis with a vertebral body tethering system: a biomechanical study

Abstract

Purpose There is a paucity of studies on new vertebral body tethering (VBT) surgical constructs especially regarding their potentially motion-preserving ability. This study analyses their effects on the ROM of the spine. Methods Human spines (T10-L3) were tested under pure moment in four different conditions: (1) native, (2) instrumented with one tether continuously connected in all vertebrae from T10 to L3, (3) additional instrumented with a second tether continuously connected in all vertebrae from T11 to L3, and (4) instrumented with one tether and one titanium rod (hybrid) attached to T12, L1 and L2. The instrumentation was inserted in the left lateral side. The intersegmental ROM was evaluated using a magnetic tracking system, and the medians were analysed. Please check and confirm the author names and initials are correct. Also, kindly confirm the details in the metadata are correct. The mentioned information is correct Results Compared to the native spine, the instrumented spine presented a reduction of less than 13% in global ROM considering flexion–extension and axial rotation. For left lateral bending, the median global ROM of the native spine (100%) significantly reduced to 74.6%, 66.4%, and 68.1% after testing one tether, two tethers and the hybrid construction, respectively. In these cases, the L1-L2 ROM was reduced to 68.3%, 58.5%, and 38.3%, respectively. In right lateral bending, the normalized global ROM of the spine with one tether, two tethers and the hybrid construction was 58.9%, 54.0%, and 56.6%, respectively. Considering the same order, the normalized L1-L2 ROM was 64.3%, 49.9%, and 35.3%, respectively. Conclusion The investigated VBT techniques preserved global ROM of the spine in flexion–extension and axial rotation while reduced the ROM in lateral bending.

Comparison of long-term results of anterior surgical correction of Lenke type 5 idiopathic scoliosis using dynamic and rigid fixation in patients with complete or near-complete skeletal maturity

“…Unfortunately, there are no biomechanical studies providing evidence for greater strength of double cords, although such an assumption was made by Baroncini et al 37 A recent biomechanical study demonstrated that single or double cords did not significantly differ in restricting global and L1-L2 spinal range of motion in flexion or extension (<10%) and left or right axial rotation (<14%). 30 In addition, it was shown, that intervertebral discs and facet joints do not undergo degenerative changes after an average of 29 months of follow-up in dynamic correction surgery. 38 …”

“… 5 , 29 Dynamic correction allows for preserved mobility in the instrumented region, which has been confirmed by biomechanical studies. 30 Furthermore, dynamic correction allows patients to return to their usual physical activity and sports within a relatively early timeframe. 31 …”

Posterior Vertebral Body Tethering: A Preliminary Study of a New Technique to Correct Lenke 5C Lumbar Curves in Adolescent Idiopathic Scoliosis

“…The main advantage of vertebral body tethering is to keep spine mobility. A lot of studies demonstrate that this mobility helps to compensate sagittal issues and that a loss of lumbar mobility could lead to functional disability [11,12,16,17,[22][23][24][25][26]. The posterior Wiltse approach respects spine mobility as much as an anterior approach.…”

Mechanical Fatigue Performance of Patient-Specific Polymer Plates in Oncologic Mandible Reconstruction

“…Frequency was adjusted to 3 Hz. The total number of cycles was set to 250,000 (and 500,000 for titanium) which roughly represents the amount of chewing cycles per year [ 16 ] and was recorded at a frequency of 100 Hz [ 18 ]. Testing was stopped in case of plate or screw failure or significant deformation of osteosynthesis materials; cycles were then recorded up to the point of failure.…”