High-load preconditioning of human soft tissue hamstring grafts: An in vitro biomechanical analysis.
OBJECTIVE
In order to minimize viscoelastic elongation of ACL reconstruction grafts, preconditioning protocols have been employed in clinical practice prior to final graft fixation. The purpose of this study was to evaluate two separate high-load static preconditioning protocols of double-looped semitendinosus-gracilis grafts and compare these results to both a current clinical protocol and a control group with no preconditioning protocol applied. It was hypothesized that a high-load, static preconditioning protocol would minimize graft elongation during a simulated progressive early rehabilitation compared to both the "89 N" clinical protocol and control groups.


METHODS
Grafts were randomly allocated into four preconditioning study groups: (1) control (no preconditioning), (2) clinical protocol (89 N for 15 min), (3) high-load, short duration (600 N for 20 s), and (4) high-load, long duration (600 N for 15 min). After preconditioning, grafts were cyclically loaded between 10 and 400 N at 0.5 Hz for 450 cycles to simulate early postoperative rehabilitation. Graft displacement (elongation) was recorded during both preconditioning and cyclic loading.


RESULTS
Increased preconditioning load magnitude and duration significantly reduced graft elongation during cyclic loading (p < 0.05) which corresponded to an inverse relationship with increased elongation during preconditioning. The "600 N for 15 min" protocol resulted in significantly less elongation during simulated early rehabilitation than both the control group and the "89 N for 15 min" protocol (p < 0.001, p < 0.05).


CONCLUSIONS
Graft elongation during simulated early rehabilitation was significantly reduced by a high-load preconditioning protocol applied for an extended period of time compared to a current common clinical protocol and grafts that were not preconditioned. In addition, the amount of elongation during simulated early rehabilitation was similar between grafts preconditioned using the current clinical practice protocol and the high-load/short-duration protocol, implying that the latter could potentially induce the same viscoelastic changes in soft tissue grafts as the current clinical practice. The "600 N for 20 s" preconditioning protocol may provide similar postoperative results as the clinical protocol, "89 N for 15 min", and also reduce or maintain operative time. A high-load preconditioning protocol that reduces graft elongation may benefit patients undergoing ACL reconstruction, especially for cases of failed primary reconstruction, genu recurvatum, and increased tibial slope, where maintaining graft length is imperative to restore knee stability.
Department of BioMedical Engineering, Steadman Philippon Research Institute, 181 W. Meadow Drive, Suite 1000, Vail, CO, 81657, USA.
W Charles
WC
Lockwood
Department of BioMedical Engineering, Steadman Philippon Research Institute, 181 W. Meadow Drive, Suite 1000, Vail, CO, 81657, USA.
Daniel Cole
DC
Marchetti
Department of BioMedical Engineering, Steadman Philippon Research Institute, 181 W. Meadow Drive, Suite 1000, Vail, CO, 81657, USA.
Kimi D
KD
Dahl
Department of BioMedical Engineering, Steadman Philippon Research Institute, 181 W. Meadow Drive, Suite 1000, Vail, CO, 81657, USA.
Jacob D
JD
Mikula
Department of BioMedical Engineering, Steadman Philippon Research Institute, 181 W. Meadow Drive, Suite 1000, Vail, CO, 81657, USA.
Brady T
BT
Williams
Department of BioMedical Engineering, Steadman Philippon Research Institute, 181 W. Meadow Drive, Suite 1000, Vail, CO, 81657, USA.
Matthew M
MM
Kheir
Department of BioMedical Engineering, Steadman Philippon Research Institute, 181 W. Meadow Drive, Suite 1000, Vail, CO, 81657, USA.
Travis Lee
TL
Turnbull
Department of BioMedical Engineering, Steadman Philippon Research Institute, 181 W. Meadow Drive, Suite 1000, Vail, CO, 81657, USA. drlaprade@sprivail.org.|The Steadman Clinic, Vail, CO, USA. drlaprade@sprivail.org.
Robert F
RF
LaPrade
D000293:Adolescent; D000328:Adult; D000368:Aged; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001696:Biomechanical Phenomena; D002648:Child; D002985:Clinical Protocols; D000071976:Gracilis Muscle / Q000502:physiology* / Q000637:transplantation; D000070632:Hamstring Tendons / Q000502:physiology* / Q000637:transplantation; D006801:Humans; D008875:Middle Aged; D057234:Preoperative Period; D013314:Stress, Mechanical; D013710:Tendons / Q000502:physiology* / Q000637:transplantation; D019737:Transplants; D055815:Young Adult
ACL reconstruction; Gracilis; Hamstring grafts; Knee joint; Preconditioning; Semitendinosus