Relaxation Response Of Lumbar Segments Undergoing Disc Space Distraction: Implications To The Stability Of Anterior Lumbar Interbody Implants.

Relaxation Response of Lumbar Segments Undergoing Disc Space Distraction: Implications to the Stability of Anterior Lumbar Interbody Implants.
Havey RM, Voronov LI,Tsitsopoulos PP, Carandang G, Ghanayem AJ, Lorenz MA, Zindrick MR, Patwardhan AG.

Source

*Musculoskeletal Biomechanics Laboratory, Department of Veterans Affairs, Edward Hines Jr.VA Hospital, Hines, Illinois. †Department of Orthopaedic Surgery and Rehabilitation, Loyola University Medical Center, Maywood, Illinois.

Abstract

ABSTRACT: Studydesign. A biomechanical study of human cadaveric lumbar spine segments undergoing disc space distraction for insertion of anterior lumbar interbody implants.Objective. To measure thedistraction force and its relaxation over a period of up to 3 hours following disc space distraction as a function of the distraction magnitude and disc level.Summary ofBackground Data. Interbody implants depend on compressive preload produced by disc space distraction (annular pre-tension) for initial stabilization of the implant-bone interface.However, the amount of preload produced by disc space distraction due to insertion of the implant, and its subsequent relaxation have not been quantified.Methods. Twenty-twofresh human lumbar motion segments (age: 51±14.8 years) were used. An anterior lumbar discectomy was performed. The distraction test battery consisted of a tension stiffness testperformed before and after each relaxation test, two distraction magnitudes of 2- and 4-mm, and a recovery period before each distraction input. The distraction forces andlordosis angles were measured.Results. Peak distraction force was significantly larger for the 4-mm distraction (431.8±116.4 N) than for the 2-mm distraction (204.9±55.5 N) (p