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Lutz-P Nolte

Publications and source records attributed to Lutz-P Nolte.

6 recordsLinked to original sources
PubMed2006

Establishment of a novel intervertebral disc/endplate culture model: analysis of an ex vivo in vitro whole-organ rabbit culture system.

STUDY DESIGN: Ex vivo in vitro study evaluating a novel intervertebral disc/endplate culture system. OBJECTIVES: To establish a whole-organ intervertebral disc culture model for the study of disc degeneration in vitro, including the characterization of basic cell and organ function. SUMMARY OF BACKGROUND DATA: With current in vivo models for the study of disc and endplate degeneration, it remains difficult to investigate the complex disc metabolism and signaling cascades. In contrast, more controlled but simplified in vitro systems using isolated cells or disc fragments are difficult to culture due to the unconstrained conditions, with often-observed cell death or cell dedifferentiation. Therefore, there is a demand for a controlled culture model with preserved cell function that offers the possibility to investigate disc and endplate pathologies in a structurally intact organ. METHODS: Naturally constrained intervertebral disc/endplate units from rabbits were cultured in multi-well plates. Cell viability, metabolic activity, matrix composition, and matrix gene expression profile were monitored using the Live/Dead cell viability test (Invitrogen, Basel, Switzerland), tetrazolium salt reduction (WST-8), proteoglycan and deoxyribonucleic acid quantification assays, and quantitative polymerase chain reaction. RESULTS: Viability and organ integrity were preserved for at least 4 weeks, while proteoglycan and deoxyribonucleic acid content decreased slightly, and matrix genes exhibited a degenerative profile with up-regulation of type I collagen and suppression of collagen type II and aggrecan genes. Additionally, cell metabolic activity was reduced to one third of the initial value. CONCLUSIONS: Naturally constrained intervertebral rabbit discs could be cultured for several weeks without losing cell viability. Structural integrity and matrix composition were retained. However, the organ responded to the artificial environment with a degenerative gene expression pattern and decreased metabolic rate. Therefore, the described system serves as a promising in vitro model to study disc degeneration in a whole organ.

Animals↗
PubMed2006

Ligament balancing in TKA: evaluation of a force-sensing device and the influence of patellar eversion and ligament release.

Ligament balancing in total knee arthroplasty may have an important influence on joint stability and prosthesis lifetime. In order to provide quantitative information and assistance during ligament balancing, a device that intraoperatively measures knee joint forces and moments was developed. Its performance and surgical advantages were evaluated on six cadaver specimens mounted on a knee joint loading apparatus allowing unconstrained knee motion as well as compression and varus-valgus loading. Four different experiments were performed on each specimen. (1) Knee joints were axially loaded. Comparison between applied and measured compressive forces demonstrated the accuracy and reliability of in situ measurements (1.8N). (2) Assessment of knee stability based on condyle contact forces or varus-valgus moments were compared to the current surgical method (difference of varus-valgus loads causing condyle lift-off). The force-based approach was equivalent to the surgical method while the moment-based, which is considered optimal, showed a tendency of lateral imbalance. (3) To estimate the importance of keeping the patella in its anatomical position during imbalance assessment, the effect of patellar eversion on the mediolateral distribution of tibiofemoral contact forces was measured. One fourth of the contact force induced by the patellar load was shifted to the lateral compartment. (4) The effect of minor and major medial collateral ligament releases was biomechanically quantified. On average, the medial contact force was reduced by 20% and 46%, respectively. Large variation among specimens reflected the difficulty of ligament release and the need for intraoperative force monitoring. This series of experiments thus demonstrated the device's potential to improve ligament balancing and survivorship of total knee arthroplasty.

Aged↗
PubMed2003

Posterior thoracic extrapedicular fixation: a biomechanical study.

STUDY DESIGN: In vitro biomechanical testing of thoracic spine specimens using a standardized three-dimensional spine flexibility protocol. OBJECTIVES: To compare the mechanical stability of the intrapedicular and extrapedicular technique for pedicle screw placement. The hypothesis was that extrapedicular screw placement provides an equally rigid construct. SUMMARY OF BACKGROUND DATA: Pedicle screws provide rigid fixation of instabilities in the lumbar and lumbosacral spine. Anatomic considerations and the potential risk of neurologic complications are the main reasons to hesitate using pedicle screws in the thoracic spine. Extrapedicular fixation would allow safer insertion due to an increased distance to the spinal canal. METHODS: Twelve human cadaveric thoracic spines (six intra-, six extrapedicular) were instrumented with the USS system, using computed tomography-based computer navigation to ensure accurate placement. The specimens were tested in flexion-extension, torsion, and lateral bending. The ROM was measured using an optoelectronic system, and the two methods were compared before and after implantation of the USS construct and before and after fatigue testing of the construct. RESULTS: The ROM of the instrumented spine was reduced to less than 50% that of its original ROM. There were no statistically significant differences in the ROM reduction between the intra- and the extrapedicular technique. Cyclic fatiguing of the construct did not significantly increase the ROM. CONCLUSIONS: The extrapedicular technique provides a construct for stabilization of the thoracic spine that is as rigid as the conventional intrapedicular technique, but has the advantage of a safer surgical screw insertion.

Adult↗
PubMed2002

Anterior fixation in the osteoporotic spine: cut-out and pullout characteristics of implants.

A new concept for the anchorage of anterior fixation implants in the osteoporotic thoracic and lumbar spine is presented. The SpiralBlade has been proposed as a suitable device for use in the osteoporotic spine, due to its broad, flat surface, which should provide resistance against cut-out of the implant through the vertebral body under dynamic loading. The cut-out and pullout characteristics of this implant were tested. The SpiralBlade was tested with and without a supplementary insertion guide screw. Two other commercial implants were tested for comparison: the VentroFix and the MACS-TL HMA (hollow monoaxial) screw. All implants were tested in osteoporotic human cadaveric vertebrae, using a modified in vitro testing protocol which simulated a full corpectomy model. Dynamic cyclic loading of 100 N, 200 N and 400 N was applied to the implant for 1000 cycles at each load level, and the subsidence of the vertebral body relative to the implant was measured. Following cyclic testing, the pullout strength of the implant was measured. No significant differences were found in the cut-out performance between the SpiralBlade with guide screw and the VentroFix. The SpiralBlade inserted without a guide screw was prone to cutting-out and a substantial loss of angular alignment of the vertebral body. Cut-out of the HMA screw was significantly greater than with the other implants. Two HMA screws fractured during testing. The VentroFix, with an average pullout force of 1166 N, has a significantly higher resistance to pullout than the SpiralBlade with guide screw (417 N), the SpiralBlade (332 N) and the Aesculap HMA screw (298 N). The SpiralBlade may be an alternative to anterior screw fixation in the osteoporotic spine, offering the same cut-out resistance with one implant rather than two screws.

Aged↗