Morphological parameters for implantation of the screwless spring loop dynamic posterior spinous process stabilizing system

Abstract

Listen

Translate article

PurposeThis study aimed to quantify morphological characteristics of the posterior lumbar spinous process, which may affect stable implantation of screwless wire spring loops. MethodsVirtual implantations of a screwless wire spring loop onto pairs of lumbar spinous processes were performed for computed tomography (CT)-derived three-dimensional vertebral models of 40 Korean subjects. Morphological parameters of lumbar vertebrae 1 through 5 (L1–L5) were measured with regard to bone-implant interference. ResultsIn males, the transspinous process fixation lengths decreased from 57.8±3.0mm to 48.8±3.2mm as the lumbar joints descend from L1–L2 to L4–L5, with those in females about 4.1±0.4mm shorter (p<0.05) than in males through all lumbar joints. The fixation angle on the sagittal plane varied from 105.0° to 101.3° relative to the transverse plane as the vertebrae descend. The clenched thickness in females was the least (6.7±1.2mm) for the L2 lower spinous process and the greatest (8.1±2.2mm) for the L4 upper spinous process; this was 1.0±10.3mm less than that for males at corresponding levels (p>0.05). The ratio of the spinous process clenched thickness to the transspinous fixation length increased from 0.133±0.016 to 0.196±0.076 for the upper spinous processes as the lumbar joints descend. ConclusionsThe ratio of the spinous process clenched thickness to the transspinous fixation length varies, depending on gender and whether the clenched level is the upper or lower spinous process. These parameters related to the clenching fixation stability should be considered in development and implantations of the screwless wire spring loop.