[3-dimensional registration of micro-movements of vertebral implants by a specially adapted measuring system using magnetic transducers].
The aim of this study was to develop a biomechanical experimental set-up to quantify motion of ventrally inserted spinal implants at the implant/bone interface. The model we used was the vertebral column of the calf. Lumbar vertebrae L2 to L4 were "instrumented" with a screw-rod system. The adjacent vertebrae L1 and L5 were connected to a servohydraulic testing machine and axial compression applied. Shortening of the specimen and three-dimensional movement of the most cranial implant relative to the bone was recorded using 3 electromagnetic transducers. 100,000 cycles of axial loading varying between -0.5 kN and -1 kN were applied. Static shortening of the specimen of 8.5 mm and an elastic movement of 180 to 280 microns were measured. The greatest amplitude of single-plane motion was recorded in the sagittal plane in both static and elastic modes. Implant motion within each cycle was recorded accurately as load-displacement curves within a range of 1.35 to 30 microns. With this test set-up, primary stability of different spinal implant systems can be compared. The use of electromagnetic transducers permits three-dimensional implant motion analysis even when only a mono-axial servohydraulic testing machine is available.
Schramm
M
M
Orthopädische Universitätsklinik Friedrich Alexander Universität Erlangen-Nürnberg, Germany.
Fourlas
A
A
Pitto
R P
RP
Bär
K
K
D000818:Animals; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002417:Cattle; D019544:Equipment Failure Analysis; D006801:Humans; D008159:Lumbar Vertebrae / Q000503:physiopathology / Q000601:surgery*; D011183:Postoperative Complications / Q000503:physiopathology; D016059:Range of Motion, Articular / Q000502:physiology*; D012600:Scoliosis / Q000503:physiopathology / Q000601:surgery*; D012815:Signal Processing, Computer-Assisted; D013123:Spinal Fusion / Q000295:instrumentation*; D014159:Transducers
Dreidimensionale Aufzeichnung der Mikrobewegung von Wirbelkörperimplantaten durch ein speziell adaptiertes Messsystem auf Wirbelstrombasis.