Summary

Comparing the effects of a sport-specific fatigue protocol on a validated biomechanical return-to-sports (RTS) protocol through the ambulant measurement of joint angles between post-ACLr patients and a healthy control group. Expanding current RTS test protocols with sport-specific movements and fatigue might add to the test’s discriminative value and a more substantiated RTS advice.

Abstract

There is a high risk of contralateral rupture or re-rupture after ACL reconstruction (ACLr), which increases near the end of a sports match or training session, implying a role for fatigue as a risk factor. In spite of this, patients are currently approved to return to sports (RTS) following a non-fatiguing knee stability protocol. The kinematic research which contributed to the formation of this protocol has been restricted to the use of laboratories, impeding the effective inclusion of sport-specific movement patterns and fatigue. However, advances in sensor technology now allow for mobile outdoor measurements, providing insight into the sport-specifically fatigued biomechanics of the ACLr knee.

Purpose

Comparing the effects of a sport-specific fatigue protocol on a validated biomechanical RTS protocol through the ambulant measurement of joint angles between post-ACLr patients and a healthy control group.

Methods

12 subjects 1 year post-ACLr (8 male, 4 female; age: 23.1 ± 4.8 years, height: 179.6 ± 8.1 cm, mass: 78.7 ± 13.3 kg, Tegner: 6.8 ± 0.7) and 12 healthy controls (HC) (6 male, 6 female; age: 25.5 ± 4.2 years, height: 179.4 ± 4.2 cm, mass: 72.5 ± 8.7 kg, Tegner: 7.4 ± 1.3) performed a base-line measurement of a validated hop-test protocol (drop-vertical jump, hop for distance and side-hop). A sport-specific fatigue protocol was imposed, where the subjects ran and pivoted 60 minutes on a 20m course, interspersed and concluded with the same hop-test protocol every 15 minutes. Wireless inertial magnetic measurement units (IMMUs) were placed at the sacrum, upper and lower legs to measure the range of motion (ROM) and the maximal joint angles of the lower extremities. Statistical analysis used repeated measures ANOVA (P < 0.05) with Bonferroni post hoc analysis.

Results

Baseline hop tests showed no differences between the ACLr and HC group. After 30-45 minutes, a significantly higher maximal knee valgus angle (F2,45 = 76.62, P < .001) was seen in both knees of the ACLr group when compared to the HC group while pivoting. Additionally, after 45 minutes of testing, the ACLr group showed significantly higher knee valgus angles during the landing phase of the drop vertical jump test for the contralateral knee when compared to the reconstructed knee (F2,45 = 3.14, P < .005).

Conclusion

Sport-specific fatigue protocols, while currently absent in validated RTS test protocols, reveal increased knee valgus angles in ACLr patients, which are associated with an increased risk for re-injury. Expanding current RTS test protocols with sport-specific movements and fatigue might add to the test’s discriminative value and a more substantiated RTS advice.