|
Year |
2002 |
|---|---|
|
Question Number |
229. |
|
Category |
Sports Medicine |
Question
Preconditioning an anterior cruciate ligament graft can reduce the amount of stress relaxation by as much as
1- 10%
2- 20%
3- 50%
4- 75%
5- 90%
Figures
Answer (click for answer)
Preferred Response: 3
In the study quoted, a primate model was used to evaluate acute viscoelastic relaxation in the patellar tendon. Thirty-five patella-patellar tendon-tibia (P-PT-T) complexes were harvested from normal primate knees (Cynomolgus monkeys), and were divided into five groups for mechanical comparison. Specimens were subjected to two 10-min relaxation tests separated by a 1-30-min unloaded interval. The first test provided baseline relaxation data as well as serving as preconditioning for the second test. Results indicate that preconditioning significantly reduces the tension lost in a graft due to viscoelastic relaxation by as much as 50%. The effect of preconditioning is reduced with increasing recovery time (the time between preconditioning and the second relaxation test), but the effect is still significant after 30 min of unloading. No differences were observed in the relaxation behavior of specimens that were cyclicly or isometrically preconditioned, nor were differences observed between irradiated and nonirradiated specimens. These results suggest that preconditioning can reduce acute tension loss in a graft due to viscoelastic relaxation and that simple isometric preconditioning is just as effective as cyclic stretching.
Reference: Buckwalter JA, Einhorn TA, Simon SR (eds): Orthopaedic Basic Science: Biology and Biomechanics of the Musculoskeletal System, ed 2. Rosemont, IL, AAOS, 2000, pp 581-616.
Graf BK, Vanderby R Jr, Ulm MJ, Rogalski MP, Thielke RJ: Effect of preconditioning on the viscoelastic response of primate patellar tendon. Arthroscopy 1994;10:90-96.