Clinical and functional outcomes 2 years after ACL repair and InternalBraceTM ligament augmentation in comparison with ACL reconstruction and healthy controls

For patients with proximal anterior cruciate ligament (ACL) tears, primary ACL repair

with additional suture tape augmentation (ACL-IB, InternalBraceTM) has been introduced as an

alternative procedure to ACL reconstruction (ACL-R). The advantages of ACL repair over

ACL-R include preservation of the native ligament and lack of tendon harvesting. However,

evidence on the outcome of ACL-IB has only started to emerge. First studies on ACL-IB after

proximal ACL tears have reported promising results in patient-reported outcome measures and

in clinical knee examination comparable to ACL-R. Although ACL repair is thought to restore

proprioception and natural knee mechanics, evidence for such functional and biomechanical

benefits in patients after ACL-IB is limited or absent in the literature. In addition, there is insufficient

information on the extent of potential limitations after ACL-IB compared to healthy

subjects. Knowledge of these aspects is essential to understand the role of ACL-IB alongside

ACL-R and to establish this procedure as an alternative treatment option for proximal ACL

tears in orthopaedic surgery.

The aim of this thesis was to provide evidence on clinical and functional-biomechanical

outcomes 2 years after ACL-IB, and to directly compare these outcomes to sex- and agematched

patients 2 years after ACL-R using hamstring tendon autograft, and sex- and agematched

healthy controls. For this purpose, we assessed our participants in a comprehensive

test protocol, including patient-reported outcome measures and a clinical leg examination (clinical

outcomes); as well as functional tests of leg performance in knee muscle strength, knee

proprioception, dynamic postural control, and single-leg hops; as well as analyses of leg joint

kinematics and kinetics and leg muscle activation during walking and during forward singleleg

hop landing (functional-biomechanical outcomes). The clinical and functional-biomechanical

outcomes were compared between the legs within each group and between the involved

(operated) leg of patients and the non-dominant leg of controls.

Two years after ACL-IB, we found good results in clinical outcomes. Leg asymmetries

remained in performance and knee joint mechanics during single-leg hops. All outcomes were

comparable between ACL-IB and ACL-R. Patients after both ACL-IB and ACL-R did not return

to healthy levels. Compared to controls, they subjectively perceived functional impairments

of their injury, had a reduced quadriceps strength and altered knee biomechanics during

walking. Furthermore, only patients after ACL-IB had different knee mechanics during hop

landing and only patients after ACL-R had different semitendinosus muscle activation during

walking than controls.

Our study demonstrated that 2 years after surgery, patients undergoing less invasive ACLIB

can expect a comparable clinical and functional-biomechanical outcome to that of patients

undergoing ACL-R, without risking comorbidities of graft removal or changes in hamstrings

function. These results support ACL-IB as an alternative surgery to ACL-R for a subset of ACL

patients representing our cohort (i.e., proximal rupture, moderate knee-loading activity level).

In addition, we have shown that even preservation of native ACL fibres does not result in a

healthy clinical and functional-biomechanical outcome level. This suggests that the initial ACL

rupture causes changes that cannot be restored with surgery alone.