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PD Dr. med. Christian Egloff

Department of Biomedical Engineering
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Klinische und funktionelle Resultate 2 Jahre nach VKB Naht mit Internal Brace Augmentation im Vergleich zur VKB Rekonstruktion unter Berücksichtigung sozioökonomischer Aspekte und Rückkehr zur Arbeitsfähigkeit

Research Project  | 4 Project Members

Der Stellenwert des Erhaltes des vorderen Kreuzbandes nach VKB Ruptur wird kontrovers diskutiert - insbesondere spielt dabei das Internal Bracing, also die Ligament Augmentation zusätzlich zur Naht, eine zentrale Rolle. In unserer Klinik haben wir mittlerweile über 60 Patienten mit dieser Technik operiert mit sehr guten klinischen Resultaten. Allerdings bleibt die Literatur bis dato objektive funktionelle und biomechanische Resultate dieses Verfahrens schuldig, die jedoch auch prognostisch, v.a. im Hinblick auf die Entstehung einer sekundären Kniegelenksarthrose, höchst relevant sind. Basierend auf den sehr erfreulichen klinischen Resultaten ist das Ziel der vorliegenden Studie daher, erstmalig eine umfassende objektive und quantitative klinische und funktionelle Untersuchung bei Patienten nach VKB Naht in direktem Vergleich mit der Goldstandard Technik, der VKB Rekonstruktion, und einem Kniegesunden Kontrollkollektiv durchzuführen. Die hier durchgeführten Tests werden somit wichtige neue Erkenntnisse liefern über den Funktionszustand sowie die Mechanik der Kniegelenke nach Internal Bracing und ob diese Patienten im direkten Vergleich zur Rekonstruktion ein geringeres Muskelkraftdefizit und eine verbesserte Gangfunktion aufgrund der erhaltenen Anatomie des genähten VKBs aufweisen, die als protektive Faktoren der Arthroseentstehung anzusehen sind. Die Studie bildet somit die Grundlage für weitere Untersuchungen zur Optimierung der Behandlung künftiger Patienten (inklusive einer optimierten Patientenselektion) und wird wichtige Erkenntnisse für die Optimierung der Rehabilitation nach primärer VKB Naht sowie nach Rekonstruktion liefern mit Relevanz im Kontext der Gonarthrose.

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

PhD Project  | 5 Project Members

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.

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Dose-response relationship of in vivo ambulatory load and cartilage biomarkers: the role of age, tissue health and inflammation

Research Project  | 4 Project Members

Articular cartilage is an avascular and aneural tissue that facilitates joint motion with minimal friction. Osteoarthritis (OA) is a joint disease that affects the whole joint resulting in severe articular cartilage degeneration with a prevalence worldwide of more than 10%. Although the molecular mechanisms that trigger the pathological changes in OA are largely unknown, the ability of chondrocytes to respond to load is believed to play a critical role in maintaining healthy tissue and in the initiation of OA. Different modes of ambulation have resulted in increases of specific blood markers, and immobilization during bed-rest lead to reductions in the same blood markers. However, the dose-response relationship between ambulatory load and mechanosensitive blood markers, its biological variation in healthy persons and in patients with a high risk of developing OA (e.g. with increasing age or after joint injury), and its relevance for cartilage degeneration are unknown. Based on reported differences in the magnitude of load-induced changes in blood markers of articular cartilage depending on the type of physical activity, we have previously tested an experimental framework of a systematic and controlled modulation of weight bearing during a walking stress test that we propose to employ in this study. We will address the following specific aims: Specific Aim 1: Investigate the in vivo dose-response relationship between ambulatory load and mechanosensitive blood markers of articular cartilage using controlled weight bearing during a walking stress test and age, tissue status and the presence of inflammation as experimental paradigms. Specific Aim 2: Investigate the prognostic ability of the individual in vivo dose-response relationship between ambulatory load and mechanosensitive blood markers of articular cartilage for articular cartilage degeneration. Healthy subjects and subjects with previous anterior cruciate ligament (ACL) injury aged 20 to 50 years will be clinically assessed, undergo magnetic resonance imaging (MRI) of both knees, and complete questionnaires on physical function and physical activity. Participants will wear an activity monitor for the 7 days before and during the experiment to record their physical activity level. Each participant will complete three walking stress tests (30 minutes walking) on separate days with repeated blood sampling to assess load-induced changes in levels of mechanosensitive blood markers (COMP, MMP-3, PRG-4, ADAMTS-4). In each test, one of three different ambulatory loads will be applied (80, 100 and 120% body weight (BW)). Inflammation will be assessed as IL-6 serum concentration. Tissue status of articular knee cartilage will be assessed as MRI T2 relaxation time and cartilage thickness at baseline and at 24-month follow-up. This study can be considered as proof-of-concept of a potential diagnostic test (walking stress test) for cartilage mechanosensitivity and will provide first evidence of the role of age, tissue status and presence of inflammation on the dose-response relationship between in vivo ambulatory load and mechanosensitive blood markers of articular cartilage and its relevance for prognosing cartilage degeneration. These results will allow to judge the importance of mechanosensitive blood markers for in vivo mechanobiology of articular cartilage. The results of this study will reveal if the proposed experimental framework may be suitable in the area of cartilage engineering and transplantation and for testing pharmacologic agents and load-modifying interventions aimed at changing tissue metabolism in the context of OA pathomechanics that can be further investigated in ex vivo, in situ and in animal models of OA.

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Muscle function and dynamic and postural stability in patients receiving hip or knee arthroplasty

Research Project  | 5 Project Members

Despite of reported strength deficits and the importance of balance, to date the potential contribution of strength deficits in patients before and after THA or TKA to compromised balance ability is unknown. Furthermore, the role of preoperative muscle function on functional outcome of THA and TKA is poorly understood. A correlation between compromised preoperative muscular function and postoperative outcome would suggest that preoperative physical therapy may be critical for preserving the muscular status and may help explain reported poorer outcome after late treatment when muscular function has already deteriorated. Answers to these questions are highly relevant for developing and improving preoperative treatment schemes and postoperative rehabilitation programs. In particular, understanding the role of strength deficits of specific muscles on dynamic and postural stability will be critical for defining optimal rehabilitation scheme, specifically targeting the muscles responsible for the balance ability and ultimately reducing the risk of falls. The project includes two studies differing in design and primary and secondary objectives but with overlapping patient populations.

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RetroBRACE II: Clinical and Functional Outcomes 2 Years After ACL Repair and InternalBrace Ligament Augmentation in Comparison With ACL Reconstruction

Research Project  | 5 Project Members

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.

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Gangbild nach Knie- bzw. Hüft-TE

Research Project  | 5 Project Members

In this study, we will first identify objective parameters describing gait asymmetry that can be used as outcome measures for future clinical trials. We propose that gait asymmetry can be assessed using a body-worn inertial sensor system (RehaGait®), and that these parameters differ between pre- to postoperative measurements in patients undergoing total arthroplasty and between patients with endstage knee or hip osteoarthritis (OA) and healthy subjects. In a second step we will show that joint biomechanics in the lower extremity of the affected and the contralateral side is influenced by OA and arthroplasty and that gait asymmetry is explained by muscle strength, muscle activity, joint moments and/or passive range of motion. We will include persons with endstage knee (n=50) or hip (n=50) OA and age matched healthy persons (n=50). Gait asymmetry assessed using a portable gait analysis will be compared to that assessed using established laboratory systems and compared between different patient groups and between patients and healthy subjects. Muscle strength, muscle activity, joint moments and range of motion will be tested and related to gait asymmetry. Potential confounders pain and health and functional status will be assessed.