Abstract
Objectives:
Anterior cruciate ligament reconstruction (ACLR) in adolescent patients is commonly performed utilizing hamstring (HT) or quadriceps (QT) tendon autografts. However, differences in jump landing biomechanics between these two graft types remains unclear. Understanding these differences can inform a graft-specific rehabilitation approach to improve jump landing biomechanics.
The purpose of this study was to compare symmetry of jump landing biomechanics during drop vertical jump among ACLR patients with HT and QT grafts.
Methods:
This retrospective study included 53 adolescents who underwent unilateral ACLR (HT=23 patients; 12 female/11 male, QT=30 patients ; 16 female/14 male, mean age 16.1±1.3). Motion analysis data were collected during drop vertical jump between 7 to 9 months post-surgery. Drop vertical jump was captured using a 20 camera optical motion capture system (Vicon Motion Systems, Oxford, UK) synchronized with two Bertec force plates (Bertec Corporation, Columbus, OH). Anthropometrics, jump height, and ground reaction time were recorded. Variables of interest included maximum hip and knee flexion angles and maximum knee and hip flexion moments were calculated using the Dynamic Plug-in Gait Model. Energy absorption (average negative power) during landing and energy generation (average positive power) at maximal height vertical jumping were calculated by summing the joint work in all three planes and then divided by the time from initial contact to take off. The percentage of hip and knee power was derived as a ratio of the average power at the individual joint divided by the sum of the average power within the limb at the hip, knee, and ankle. Inter-limb asymmetry of each motion analysis variable was calculated as Bilateral Asymmetry Index (AI) between each limb (surgical versus non-surgical). A majority of participants completed the Pediatric International Knee Documentation Committee (Ped-IKDC) Subjective Knee Evaluation Form at the drop vertical measurement. Participants were grouped by graft type into HT (hamstring tendon) group and QT (quadricpes tendon) group, and participant characteristics were compared between two groups. Anthropometric information, jump height and ground reaction time were compared between HT and QT group by using unpaired t test. Motion analysis variables of surgical limb in HT group versus QT group, and non-surgical limb in HT group versus QT group were compared by using Mann-Whitney test. Differences in AI of biomechanical variables and Ped-IKDC score were also compared between two groups using Mann-Whitney test.
Results:
There were no differences in anthropometrics, jump height, ground contact time between two groups. Compared to HT group, QT group demonstrated 1) smaller maximum knee angles in surgical limb, 2) lower hip flexion moments in operated and non-operated limbs, 3) lower knee flexion moments in operated limbs, 4) lower negative power percentage and lower positive power percentage at the knee in operated limbs, and 5) higher positive power percentage at the hip in operated limbs (p<0.05). Asymmetries relative to the non-surgical limb observed in QT groups were greater compared to that in HT groups for 1) maximum knee and hip flexion angles, 2) knee flexion moments, 3) negative power percentage and positive power percentage at the knee. Conversely, asymmetries were smaller in the QT groups for negative power percentage and positive power percentage at the hip (p<0.05). There were no differences in Ped-IKDC score between two groups.
Conclusions:
Adolescent patients who underwent ACLR using QT graft demonstrated greater offloading at the knee and compensated with the hip in the surgical limb during jump landings, compared to those with HT grafts. Graft choice of QT or HT graft in ACLR may influence the knee biomechanical asymmetries. Further studies are required to determine how long these asymmetries persist. A graft-specific approach during rehabilitation may be needed to provide optimal return to sport and reinjury rate success between graft types.