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Response of Charité total disc replacement under physiologic loads: prosthesis component motion patterns
Patrick O'Leary1, Michael Nicolakis, Mark A Lorenz
1Musculoskeletal Biomechanics Laboratory, Department of Veterans Affairs, Edward Hines Jr. VA Hospital, 5th Ave. and Roosevelt Rd., Hines, IL 60141, USA.
The Spine Journal : Official Journal of the North American Spine Society
|November 18, 2005
Summary
Total disc replacement (TDR) restores motion but alters spinal biomechanics under load. Charité TDR shows varied component motion and load-displacement patterns, necessitating further study on wear and load sharing.
Area of Science:
- Spine biomechanics
- Orthopedic implant technology
- Biomedical engineering
Background:
- Total disc replacement (TDR) aims to alleviate discogenic pain and preserve spinal motion.
- The Charité TDR's floating core design theoretically mimics healthy disc kinematics under load.
- Limited data exists on TDR's response to physiologic compressive preload and component motion.
Purpose of the Study:
- To evaluate if Charité TDR restores normal lumbar motion segment load-displacement behavior under physiologic loads.
- To investigate the relative motion of Charité TDR components within the lumbar spine.
Main Methods:
- Biomechanical analysis of five human lumbar spine specimens (L1-sacrum).
- Testing under flexion and extension moments with 0 N and 400 N compressive preloads.
- Optoelectronic measurement of segmental motion and video-fluoroscopy assessment of prosthesis component kinematics.
Main Results:
- Charité TDR significantly increased lumbar segment range of motion and segmental lordosis.
- Four distinct patterns of prosthesis component motion were observed, including angular motion, lift-off, core entrapment, and translation.
- Physiologic preload altered load-displacement curves, showing regions of both reduced and increased angular change compared to intact segments.
Conclusions:
- Charité TDR restores near-normal motion quantity but alters motion quality under preload.
- Predominant motion occurred between the upper end plate and core, with varied component interactions observed.
- Implant factors and preload magnitude influence TDR function; further research on wear and load sharing is required.