Linda Bühl

Several studies from the past 10 years have shown a significant subjective benefit after a surgical treatment in comparison to a conservative treatment of a proximal hamstring rupture.4-7 There is also a strong evidence of about 10% decrease in muscle strength in comparison to the non operated site4,13. Similar muscle strength between the operated and contralateral side was observed up to 10 years after repair.14 However, to the best of our knowledge there is a lack of evidence in possible development of biomechanical and functional limb asymmetries including muscle activity caused by these postoperative muscular imbalances. Our project will therefore concentrate on the biomechanics of gait and daily activity tasks and investigate differences between the operated and contralateral limb. Primarily we will quantify potential muscular deficits between limbs and compare these to the findings of the gait pattern. If proven right and limping does occur, it can, on the long run, cause earlier onset of skeletal degeneration and osteoarthritis.8-10 As the mean age of the patients examined in the studies with hamstring rupture is usually about 40 to 45 years6 and the average life expectancy is above 80 years11, potential muscular deficits may manifest as pathological gait that may predispose these patients to premature and potentially more severe degenerative processes. For instance, it is possible that the risk of hip osteoarthritis and/or lower back or iliosacral joint osteoarthritis is higher in patients after a hamstring rupture. Therefore, improving the understanding of biomechanical and functional outcome after hamstring repair is critical, and potential deficits may be prevented with additional physiotherapy addressing muscular imbalances. In the proposed pilot study, we will compile outcome data on the outcome of a new, intraoperative lateral positioning of the anchors on the tuber ischiadicum, as was used in all of our patients, in comparison to regular anatomical anchoring direct on top of the tuber ischiadicum.12 Based on our clinical experience many patients describe a local discomfort in seated position with traditional anchor positioning, and a lateral positioning could potentially prevent this complaint as the lateral area of os ischi is not exposed to the pressure when seated. With this pilot study we will not only provide new insights into the postoperative function of the hamstrings with corresponding gait pattern for the current patients, but also possibly prevent the discomfort while sitting by changing anchor placement in future patients. Further, the data obtained in this study will facilitate proper sample size calculations for future clinical trials.

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.

Injury of the anterior cruciate ligament (ACL) is one of the most common injuries of the knee. Since May 2016, patients with proximal ruptures of the ACL have been treated with direct repair and InternalBraceTM Ligament Augmentation at the University Hospital of Basel.

The remodelling of hamstring grafts used for ACL reconstruction is completed at the earliest 2 years after the surgery. The aim of this study is to assess the clinical, biomechanical and functional outcome 2 years after anterior cruciate ligament (ACL) repair and InternalBraceTM augmentation now in direct comparison to ACL reconstruction and to identify potential deficits compared to the contralateral healthy side as well as with a knee-healthy age-matched collective. In addition, socio-economic aspects such as return to work and sports and treatment cost will be compared between both techniques.