Quantification of joint loading in adults with haemophilia using multi-segment foot modelling
Haemophilia is a rare coagulation disorder mostly affecting men. It is characterized by the absence or deficiency of circulating factor VIII (haemophilia A) or factor IX (haemophilia B). In severe cases (factor level < 1%), it could result in abnormal, sometimes spontaneous bleedings and impaired blood coagulation. Up to 90% of these bleedings occur in the musculoskeletal system, with the ankle joint being most prone to recurrent bleeding episodes. Secondary arthropathy due to recurrent ankle joint bleeds, called haemophilic ankle arthropathy, is the most disabling complication in adults with haemophilia. Yet, the functional impact of haemophilic ankle arthropathy during gait in these patients is not welldefined and the potential role of joint loading on the pathophysiological cascade remains unclear.
Recent research emphasized the importance of musculoskeletal biomechanics in developing pathological/disruptive compensation mechanisms in the ankle and foot joints due to the pathophysiological cascade of haemophilic ankle arthropathy. Based on previous evidence, improvement of clinical decision-making processes in patients with haemophilic ankle arthropathy beyond current state-of-the-art can only be achieved when including dynamic biomechanical gait features assessed with 3D gait analysis. Of particular interest for these patients is the investigation of mechanical loading in the ankle and foot complex. The main objective of this project was therefore to unravel the biomechanical joint loading in adults with haemophilia using a skin marker-based multi-segment foot model.
In the first, methodological part of this doctoral thesis, we substantiated the use of such a multi-segment foot model in clinical motion analysis. A current methodological challenge in multi-segment kinetic models is the partitioning of shear forces across each foot joint. As no technical devices yet exist which allow the measurement of these shear forces with an appropriate spatial resolution, the shear force partitioning currently is based on an existing proportionality scheme. The scientific community therefore claimed that these estimations might lead to measurement errors. In chapter 2, we could reject this claim as we did not find any differences between kinetic measurements obtained with the proportionality scheme and those directly obtained using an adjacent force plate method. We could therefore reliably measure ankle and foot joint biomechanics in pathological gait.
We also quantified the clinical misinterpretations of earlier one-segment or rigid kinetic foot models (chapter 3). In this study it was found that one-segment kinetic foot models overestimate the ankle joint peak power generation on average 14% in pathological gait – due to an overestimation of the joint angular velocity - and future research should therefore use a multi-segment foot model to overcome this clinical misinterpretation. It is generally known that walking speed is often lowered in adult patients with haemophilia. In chapter 4 of this thesis, we confirmed that walking speed affects the multisegment foot kinetics and caution is warranted when interpreting the kinetic output of the ankle and foot joints in patients with haemophilic ankle arthropathy.
In the second clinical part of this doctoral thesis, we implemented the skin markerbased multi-segment foot model to investigate the impact of haemophilic ankle arthropathy on the ankle and foot joint biomechanics during walking. In chapter 5, we established a relationship between the structural ankle joint damage (based on MRI) and the ankle joint power output in patients with haemophilia. It could therefore be concluded in this study that patients with severe blood-induced ankle joint damage have a lowered tolerance towards ankle joint mechanical loading during walking. It was also found that the biomechanical load on the ankle joint is significantly altered in PwH compared to healthy subjects, potentially triggered by the arthropathy-induced ankle joint stiffness (chapter 6). Future longitudinal studies are required to confirm this hypothesis and to determine the treatment efficacy of conservative strategies to overcome these biomechanical alterations, such as therapeutic footwear or orthopedic devices. We explored the effect of conventional footwear on the biomechanical alterations in these patients and found that these increased the ankle joint mobility and simultaneously lowered the excessive mechanical loading during mid-stance of walking (chapter 7).
In conclusion, most of the biomechanical alterations during walking in patients with haemophilia were present whenever the ankle joint had existing blood-induced ankle joint damage. The clinical relevance of this project therefore dictates that haemophilia care should focus on protecting adults with haemophilia against recurrent ankle joint bleeds in order to maintain proper gait functionality. Conservative treatment strategies could be initiated with the aim to preserve or improve the ankle joint mobility, which would positively impact the ankle and foot joint biomechanics in these patients.