Anchorage of pedicle screw rod instrumentation in the elderly spine with poor bone quality remains challenging. Our study aims to evaluate how the screw bone anchorage is affected by screw design, bone quality, loading conditions, and cementing techniques. Micro-finite element (µFE) models were created from micro-CT (μCT) scans of vertebrae implanted with two types of pedicle screws (L: Ennovate and R: S4). Simulations were conducted for a 10 mm radius region of interest (ROI) around each screw and for a full vertebra (FV) where different cementing scenarios were simulated around the screw tips. Stiffness was calculated in pull-out and anterior bending loads.Aims
Methods
Loss of motion following spine segment fusion results in increased strain in the adjacent motion segments. However, to date, studies on the biomechanics of the cervical spine have not assessed the role of coupled motions in the lumbar spine. Accordingly, we investigated the biomechanics of the cervical spine following cervical fusion and lumbar fusion during simulated whiplash using a whole-human finite element (FE) model to simulate coupled motions of the spine. A previously validated FE model of the human body in the driver-occupant position was used to investigate cervical hyperextension injury. The cervical spine was subjected to simulated whiplash exposure in accordance with Euro NCAP (the European New Car Assessment Programme) testing using the whole human FE model. The coupled motions between the cervical spine and lumbar spine were assessed by evaluating the biomechanical effects of simulated cervical fusion and lumbar fusion.Objectives
Methods
We investigated the relationship between spinopelvic
parameters and disc degeneration in young adult patients with spondylolytic
spondylolisthesis. A total of 229 men with a mean age of 21 years
(18 to 26) with spondylolytic spondylolisthesis were identified.
All radiological measurements, including pelvic incidence, sacral
slope, pelvic tilt, lumbar lordosis, sacral inclination, lumbosacral
angle (LSA), and sacrofemoral distance, were calculated from standing
lateral lumbosacral radiographs. The degree of intervertebral disc
degeneration was classified using a modified Pfirrmann scale. We
analysed the spinopelvic parameters according to disc level, degree
of slip and disc degeneration. There were significant positive correlations between the degree
of slip and pelvic incidence (p = 0.009), sacral slope (p = 0.003)
and lumbar lordosis (p = 0.010). The degree of slip and the LSA
were correlated with disc degeneration (p <
0.001 and p = 0.003,
respectively). There was also a significant difference between the
degree of slip (p <
0.001) and LSA (p = 0.006) according to the
segmental level of disc degeneration. Cite this article:
Between January 1990 and December 2000 we carried out 226 SB Charité III disc replacements for lumbar disc degeneration in 160 patients. They were reviewed at a mean follow-up of 79 months (31 to 161) to determine the clinical and radiological outcome. The clinical results were collected by an independent observer, who was not involved in patient selection, treatment or follow-up, using a combination of outcome measures, including the Oswestry Disability Index. Pain was recorded using a visual analogue score, and the most recent radiographs were reviewed. Survival of the device was analysed by the Kaplan-Meier method and showed a cumulative survival of 35% at 156 months when radiological failure was taken as the endpoint. The mean improvement in the Oswestry disability index scores after disc replacement was 14% (6% to 21%) and the mean improvement in the pain score was 1.6 (0.46 to 2.73), both falling below the clinically significant threshold. Removal of the implant was required in 12 patients, four because of implant failure. These poor results indicate that further use of this implant is not justified.
