Hop testing after an Anterior Cruciate Ligament reconstruction (ACLR) is a common functional test to determine return to play status. Due to the difficulty in capturing knee and hip mechanics over a large area while hopping little is known of differences in kinematics that may persist. Advancements in inertial sensor technology allow for assessment of hip and knee mechanics outside the laboratory setting and could provide significant insights into how these functional tests are performed.
PURPOSE: To investigate hip and knee mechanics in ACLR patients and healthy controls in the sagittal and frontal plane during hop tests, using inertial magnetic measurement units (IMMUs).
METHODS: 5 ACLR patients (2 male, 3 female, 20.4 ± 2.1 yrs, 164.2 ± 10.7 cm, 69.1 ± 23.5 kg) one year post reconstruction, and 10 healthy controls (7 male, 3 female, 21.8 ± 2.0 yrs, 178.3± 10.2 cm, 73.5± 14.3 kg) performed a single leg hop and a triple hop for distance with the reconstructed or dominant leg while wearing a suit equipped with 8 IMMUs at the feet, tibia, upper legs, sacrum and sternum. Sagittal and frontal plane hip and knee angles (flexion, abduction) at initial contact (IC) were calculated. Independent Mann-Whitney U-tests were used to statistically compare the data.
RESULTS: Significant differences (p<0.05) in knee and hip flexion and knee abduction were observed at IC for the single leg hop and triple hop between groups (table 1).
CONCLUSIONS: Subjects who have had an ACLR employ landing strategy of less hip and knee flexion and abduction when performing a single leg and triple hop as compared to the mechanics of healthy control subjects. This results in a stiffer landing strategy that may predispose them to secondary injuries if not fully addressed.
Supported by a grant from the Dutch Fulbright Centre.