In-vivo kinematics of the IVD allograft transplantation

Abstract

In a recent clinical trial of the Intervertebral disc (IVD) allograft transplantation, Ruan et al. (2007) observed remodelling of the allograft with good preservation of motion and stability of the spinal segment. It is hypothesized that remodelling of the allograft implant can restore the kinematics of the functional spinal unit. This study aims at studying the in-vivo kinematics of the patients that underwent IVD allograft transplantation. Five patients, average age 47 yrs, with cervical disc herniation underwent transplantation of fresh-frozen disc allografts after disc excision. Dynamic active flexion-extension radiographs were taken 2 months after surgery, and every 3 months thereafter to a minimum follow-up of 5 yrs. Measurement of the Center of Rotation (COR) was analyzed using an image analysis program developed in MATLAB. The results were compared to the data found in literature. Studies of the position of the COR following the operation showed that the COR position have initially deviated to the very posterior position in the early stages following surgery. However, at the final follow up all patients showed that the COR position have been restored close to the physiological position. Changes in the position of the COR at different stages following the transplantation were observed as opposed to artificial disc implants in which the position of the COR had deviated from the physiological position permanently. These changes in the position of the COR may suggest that the remodelling of the allograft may play a part in restoring the natural kinematics of the spine in the long term.