Abstract
BackgroundPretension of the viscoelastic graft by cyclic knee motion has been confirmed to decrease the graft creep and improve the outcome of anterior cruciate ligament (ACL) reconstruction. The purpose of the present study was to investigate the effect of cyclic knee motion on the elongation of the four-strand hamstring tendon autograft in situ and to explore the stable level cycle, in which the tendon length achieved a stable level.MethodsThe study was performed with 53 consecutive patients undergoing transtibial ACL reconstruction with four strand hamstring tendon from Aug 2013 to Apr 2015. 43 males and 10 females were included with mean age of 29 ± 10 years. The pretension of the tendons was operated by cyclical knee motion ranging from 0 to 110°after the femoral fixation with Endo-button. The tendon length after 10, 20, 30 and 40 cycles was measured respectively and compared by repeated measure ANOVA. Then multivariate logistic regression was used to investigate the effect of the patients’ parameters (age, gender, height, body weight, tendon length, etc.) on the elongation of the graft and the stable level cycle.ResultsThe mean lengthening of the graft at 10, 20, 30 and 40 times was 3.0 ± 1.4 mm, 4.3 ± 1.5 mm, 4.8 ± 1.7 mm and 4.8 ± 1.8 mm respectively. No significant correlation was found between the elongation and the patients’ parameters. There was significant difference of the tendon length from 0 to 30 cycles (F = 264.8, df = 1.95, p<0.001). However, the tendon length achieved a stable level after 30 cycles and the median elongation from 30 cycles to 40 cycles was 0 (0–1) mm with no significant difference (F = 2.039, p = 0.159). The male and female tendon length achieved to a stable level at 20 cycles and 30 cycles respectively but with no significant difference (p = 0.074).ConclusionsThe four-strand hamstring tendon was elongated after cyclic knee motion and the elongation achieved a stable level after 30 cycles for the transtibial technique. Both of the tendon elongation and the stable level cycle were not correlated with patients’ gender, age, preoperative duration, graft diameter and length.
Highlights
Pretension of the viscoelastic graft by cyclic knee motion has been confirmed to decrease the graft creep and improve the outcome of anterior cruciate ligament (ACL) reconstruction
The relative lengthening percentage to the intra-tunnel tendon (ITT) was calculated to exclude the influence of tendon length
Using Greenhouse-Geisser correction, significant difference was shown for the tendon elongation (F = 264.8, df = 1.95, P
Summary
Pretension of the viscoelastic graft by cyclic knee motion has been confirmed to decrease the graft creep and improve the outcome of anterior cruciate ligament (ACL) reconstruction. Anterior cruciate ligament (ACL) rupture is one of the most common sports injuries of the knee joint, leading to pain, swelling, giving way and instability [1]. ACL reconstruction restores joint stability but the outcome was affected by many factors, of which the initial strength of the graft is important [2]. The viscoelastic creep is associated with collagenous soft tissues under sustained tensile load and the graft elongation that occurs after fixation is a key factor in mechanical failure [6]. Applying tension to the ACL graft has been a technically important aspect of ACL reconstruction to prevent post-implantation graft creep [8, 9]
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