EFFECT OF AUTOGRAFT TYPE ON RECOVERY OF KNEE EXTENSOR MECHANISM FUNCTION FOLLOWING ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION

Abstract

Background:While multiple studies have shown clear benefits of autograft over allograft for anterior cruciate ligament reconstruction (ACLR) in young athletes, disagreement remains regarding the optimal autograft choice. Recovery from ACLR may be influenced by autograft type, which can include iliotibial band (IT), hamstring tendon (HT), quadriceps tendon (QT), or patellar tendon (PT) depending on skeletal maturity and surgeon preference.Hypothesis/Purpose:This study compared knee joint function among pediatric athletes with different types of ACLR autografts. We hypothesized that knee extensor function would recover faster for graft types that did not disrupt the knee extensor mechanism (i.e., IT and HT vs. PT and QT).Methods:This retrospective study examined 138 pediatric athletes (73 female; mean age 15.5, SD 2.2, range 8-21 years) who had undergone sports biomechanical testing in our motion analysis laboratory following recent unilateral ACLR (mean 7.7, range 3-18 months post-surgery). All reconstructions used autografts including 20 IT, 26 HT, 37 QT, and 55 PT. Lower extremity sagittal plane kinematics and kinetics were measured during vertical drop jump landing (41 cm height) and 45° cutting. Maximum knee flexion angles, internal knee extensor moments, and energy absorption during the landing phase (initial contact to peak knee flexion) of each movement were compared among graft types and sides (ACLR vs. contralateral) using linear mixed models with sex, age, and time since surgery as covariates.Results:Knee flexion was significantly lower on the operated vs. contralateral side for HT, QT, and PT during drop jump and for QT and PT during cutting (p<0.001). All graft types exhibited lower knee extensor moments and energy absorption on the operated side (p<0.05). This asymmetry was most pronounced for QT and PT and least pronounced for IT (Figure 1.1). Loading on the operated limb decreased from IT to HT to QT and PT, while loading on the contralateral limb increased similarly. Asymmetry of kinetics was significantly lower for IT compared with both QT and PT during both movements (p<0.01). Similar patterns were observed for HT but were not always statistically significant. No differences in asymmetry were observed between IT and HT or between QT and PT.Conclusion:Young athletes with IT and HT autografts exhibit greater engagement of the knee extensors during dynamic loading than peers with PT or QT autografts in the 18 months following ACLR. This may be due to extensor mechanism donor site morbidity associated with PT and QT grafts.Tables/Figures:Figure 1.1:.Comparison of operated (red) and contralateral (blue) limbs by graft type (model predicted average and 95% confidence interval)