A biomechanical assessment of ACL injury reconstructions to examine internal tibial rotation

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1 Southern Cross University 23rd Australasian Conference on the Mechanics of Structures and Materials 2014 A biomechanical assessment of ACL injury reconstructions to examine internal tibial rotation R Setunge L Perraton P Pivonka A Bryant H Mokhtarzadeh Publication details Setunge, R, Perraton, L, Pivonka, P, Bryant, A, Mokhtarzadeh, H 2014, 'A biomechanical assessment of ACL injury reconstructions to examine internal tibial rotation', in ST Smith (ed.), 23rd Australasian Conference on the Mechanics of Structures and Materials (ACMSM23), vol. II, Byron Bay, NSW, 9-12 December, Southern Cross University, Lismore, NSW, pp ISBN: epublications@scu is an electronic repository administered by Southern Cross University Library. Its goal is to capture and preserve the intellectual output of Southern Cross University authors and researchers, and to increase visibility and impact through open access to researchers around the world. For further information please contact epubs@scu.edu.au.

2 23rd Australasian Conference on the Mechanics of Structures and Materials (ACMSM23) Byron Bay, Australia, 9-12 December 2014, S.T. Smith (Ed.) A BIOMECHANICAL ASSESSMENT OF ACL INJURY RECONSTRUCTIONS TO EXAMINE INTERNAL TIBIAL ROTATION. R. Setunge* NorthWest Academic Centre, The, Australian Institute of Musculoskeletal Science, 176 Furlong Road, St Albans, VIC, 3021, Australia. rsetunge@student.unimelb.edu.au (Corresponding Author) L. Perraton Centre for Health, Exercise & Sports Medicine, The Level 7, Alan Gilbert Building, Building 104, The, VIC, 3010, Australia. l.perraton@student.unimelb.edu.au P. Pivonka NorthWest Academic Centre, The, Australian Institute of Musculoskeletal Science, 176 Furlong Road, St Albans, VIC, 3021, Australia. peter.pivonka@unimelb.edu.au A. Bryant Centre for Health, Exercise & Sports Medicine, The Level 7, Alan Gilbert Building, Building 104, The, VIC, 3010, Australia. albryant@unimelb.edu.au H. Mokhtarzadeh NorthWest Academic Centre, The, Australian Institute of Musculoskeletal Science, 176 Furlong Road, St Albans, VIC, 3021, Australia. mhossein@unimelb.edu.au ABSTRACT The Anterior Cruciate Ligament injury in the human knee joint has long been a debilitating injury, particularly amongst professional athletes, often requiring a reconstruction and an extensive rehabilitation period. Surgeons commonly use the single bundle reconstructions to replicate the biomechanical restraint and stability the ligament structure provides to the knee joint against anterior translation and excessive internal rotation of the tibia with respect to the femur. However after follow up of these patients during high demanding tasks, such as single legged landing there is still presentation of increased internal rotation at the knee and osteoarthritis 5-10 years following surgery. This suggests this surgical technique may not restore all the biomechanical support the natural ACL provides to the knee joint. The work presented here covers musculoskeletal computational modeling utilizing inverse kinematics predictions of knee rotation to calculate the internal rotation of the tibia. Using the model, gait analysis of ACL reconstructed subjects is compared with control healthy subjects to understand whether Internal Tibial Rotation (ITR) is fully restored in ACL single bundle reconstructions during a dynamic hop movement. KEYWORDS Anterior Cruciate ligament injury, internal tibial rotation, musculoskeletal computational modelling, single bundle reconstructions, landing. This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this license, visit 869

3 INTRODUCTION The Anterior Cruciate Ligament injury in the human knee joint has long been a debilitating injury, particularly amongst professional athletes, often requiring a reconstruction and an extensive rehabilitation period. The Anterior Cruciate Ligament (ACL) is one the ligaments, critical to the stability of the knee joint. Once torn, surgeons commonly use single bundle reconstructions to replicate the biomechanical restraint and stability the ligament structure provides to the knee joint against anterior translation and excessive internal rotation of the tibia (ITR) with respect to the femur. To date, however, studies following up these reconstructed individuals (ACLR) during highdemanding dynamic tasks have found the presentation of increased internal rotation at the knee, suggesting that the surgical technique may not restore all the biomechanical support the natural ACL provides to the knee joint (Stergiou et al 2007). Thus this study aims to develop musculoskeletal computational models utilizing inverse kinematics to calculate the internal rotation of the tibia. Using the model, gait analysis of ACL reconstructed subjects are compared with control healthy subjects to understand whether internal tibial rotation (ITR) is fully restored in ACL single bundle reconstructions during a dynamic hop movement compared to a control group. It is hypothesized that ITR will be significantly increased at the time points of footstrike, peak ground reaction force (grf) and max knee flexion in ACLR compared to Control. GAIT ANALYSIS In the past, the main limitations in studies assessing ACLR individuals have been in the difficulty in obtaining accurate biomechanical measures of joint forces, moments, and angles without invasive procedures. Thus recent biomechanical research has used in vivo gait analysis, a laboratory process using the electronics of reflective markers to integrate information from a variety of inputs to analyse the dynamics of gait. These analyses then become the inputs into computational simulations, allowing researchers to model the movement of humans using the actual ground reaction forces generated and calculate biomechanical variables such ITR in the form of knee flexion and rotation angles by inverse kinematics. A major strength of this method is that the ACL injury pathology can be studied in a multi factorial manner, accounting for the contribution of ground reaction forces, and excessive joint mobility such as (ITR) all thought to play a substantial role in the injury etiology. CONCEPT OF INVERSE KINEMATICS Inverse kinematics is a structural concept often used in 3D animations. The concept is defined as inverse since it determines joint angles of a figure made of pin jointed links by back calculation from a measurement of the overall position of the figure. The structure or figure made of rigid segments connected with joints, is called a kinematic chain. The kinematics equations of the figure define the relationship between the joint angles of the figure and its overall position. For example, if one segment of the figure moves, the kinematics equations define the movement of the rest of the segments. Solution of the inverse kinematics is undertaken by an iterative process since inverting the kinematics equations can be difficult. Once the joint angles are determined, the internal forces in the joints induced by an external force (in this problem the ground reaction force from the foot plate) can be determined using classical equilibrium and compatibility. METHOD Data Collection Eight subjects were recruited, 4 ACLR and 4 healthy control. ACLR subjects had reconstructions using an STGT graft between months prior to testing. Informed consent was obtained, ACMSM

4 complying with the s Human Ethical standards. Anthropometric measurements, including height, weight, knee width, ankle width, leg length and inter-anterior superior iliac spine distance were collected for all participants. Both ACLR and Control subjects were instructed to perform a single-legged hop landing onto one force plate embedded in the ground. Each subject completed 5 hop trials. Kinematics and Kinetic data, from the marker data of each hop trial was collected using a six camera motion capture analysis system (Vicon MX Oxford Metrics, UK). The Vicon software then created C3D files of the experimental kinematic and kinetic data obtained and these files were subsequently then pre-processed with a Matlab toolbox into OpenSim readable files. Method of Solution For each hop trial, a participant-specific musculoskeletal model was constructed in OpenSim, an open source 3D musculoskeletal modelling software developed by Stanford University (Delp et al., 2007). The generic model consisting of 27 degrees of freedom and 92 lower leg muscle-tendon units was scaled based on anthropometric data collected from the experiments as per the method of Delp et al An example of a patient specific model is shown in Figure 1 below. Figure 1. Example of a Patient-specific hop that can be converted into an OpenSim model The method of inverse kinematics was then applied at each time frame of experimental hop-motion captured. This method computed generalised coordinate values for each individual time frame, matching the experimental marker and coordinate values for each time step. In order to minimise the potential for marker error, weighting was given to specific markers where the distance between experimental markers and the markers on the model were minimised. The generalised coordinate value differences between experimental and program related calculation errors were also minimised. Mathematically this error minimisation was calculated as a weighted least squares problem, by the OpenSim software program. The solution minimized the sum of the squared differences between virtual and experimental markers as seen by equation 1 below. 2 exp exp 2 min q wi X X i ( q) + w j ( q j q j ) (1) i i mar ker s j unprescribedcoords q j = q j exp for all prescribed coordinates of j q is the vector of generalized coordinates being solved for. x i exp is the experimental position of marker i. x i (q) is the position of the corresponding marker on the model. q j exp is the experimental value for coordinate j. Prescribed coordinates were set to their experimental values. ACMSM

5 Following this minimisation of errors an optimum solution for joint motion was created in 3 degrees of freedom; x, y and z as per figure 2. The joint knee rotation angle was then calculated as the angle between the x and z plane as shown by the figure below. The joint knee flexion angle was calculated as the angle of the x and y planes. The knee rotation angle calculation includes both the inward and external rotation of the knee and as the study is focussing on the internal tibial rotation at the knee joint, ITR was defined as the positive increase in the knee rotation angle calculated. Y ϴkf Z ϴkr X Figure 2. Knee rotation angle (ϴkr) and Knee flexion (ϴkf) angle definitions of the with respect to the tibia on a scaled model of one participant during a hop trial Initial ground reaction force (GRF) from the kinetics data pre-processed and the max knee flexion from the inverse kinematics solution were then defined as 0% landing phase and 100% landing phases respectively. RESULTS AND DISCUSSIONS Figure 3a and 3b shown below represent the knee rotation against the percentage of landing in ACLR and Control subjects respectively. Comparison of the mean values of ITR of ACLR and Control demonstrate that ACLR has a reduced knee rotation (increased ITR). In fact, this can be as high as 40% for at the time point of maximum knee flexion. However, the p values indicate that the difference is statistically insignificant which is possibly due to the high standard deviations. It is therefore observed that at Foot-strike, Peak GRF and Max knee flexion no significant difference was seen in knee rotation (ITR) compared to control as demonstrated by Table 1. This may be due to the smaller sample size used in this study, implicating that future research should look to include more participants to minimise variation between the ACLR and Control groups in confounding variables. ACMSM

6 -2 Knee rotation (ITR) ACLR -5 Knee rotation (ITR) Control Degrees Degrees Landing phase % CONCLUSIONS landing phase (a) Knee rotation (ITR) ACLR (b) Knee rotation (ITR) Control Figure 3. Knee rotation (ITR) of ACLR and Control subjects Table 1. Mean and (Sd) of knee rotation (ITR) ACLR Control P value Foot-strike: -22.2(9.2) -28.6(11.3) 0.5 Knee Rotation (ITR) Peak Grf: Knee rotation (ITR) -2.3(14.2) -4.7(16.6) 0.8 Max Knee Flexion: Knee rotation (ITR) -4.1(12.0) -7.5(17.1) 0.6 Overall this paper disproves the primary hypothesis that a significant ITR increase would be seen in ACLR compared to control participants based on statistical tests. However there is likelihood with a larger sample size more of a statistically significant result may be seen. Nevertheless the aims of this study were met, as a quantitative biomechanical assessment of ACLR single bundle reconstructions examining ITR was completed. This ultimately highlights the practicality of using computational musculoskeletal modelling at the knee joint to access the functional capacity of different biomechanical properties post ACLR surgery. Indeed another preliminary analysis using the same data and computational musculoskeletal model indicated that muscle forces of ACLR and control have a significant difference. A subsequent study focussing on these muscles contributions to knee rotation and overall ACL injury recovery is currently being continued. ACKNOWLEDGMENTS Contributions of Laurence Fok and Mario Andrés Muñoz during the development of the computational models gratefully acknowledged. REFERENCES Delp, S. L., Anderson, F. C., Arnold, A. S., Loan, P., Habib, A., John, C. T., Thelen, D. G. (2007). OpenSim: open-source software to create and analyze dynamic simulations of movement. IEEE Transactions on Bio-Medical Engineering, 54(11), doi: /tbme Stergiou, N., Ristanis, S., Moraiti, C., & Georgoulis, A. D. (2007). Tibial rotation in anterior cruciate ligament (ACL)-deficient and ACL-reconstructed knees: a theoretical proposition for the development of osteoarthritis. Sports Medicine (Auckland, N.Z.), 37(7), ACMSM

7 CONCLUSIONS The main contributions of this paper are: firstly, to demonstrate the shortcomings of the conventional Sonic-Echo (SE) method and the Short Kernel Methods (SKM) for the condition assessment of timber utility poles (i.e. embedment length estimation), and secondly, to propose a simple method to improve the SE method. For the SE method, it has been shown that the conventional method (in which a constant wave velocity value is assumed, and the length estimation relies on a single sensor) is reliant on the sensor location and its distance from the impact location. In other words, it heavily relies on the time difference between the first arrival and the reflection peak. Therefore, it is proposed to employ a multi-sensors array system to enable the calculation of the actual wave velocity, and to obtain more reliable length estimation results. In the method proposed in this paper, the length of the pole is estimated without directly utilizing the time difference between the first wave arrival and reflection peaks. The velocity analysis results showed that the down-going and the reflection waves do not have exactly the same velocities. Application of the SKM for bending wave data analysis showed that the reflection peak detection is not an easy task and heavily relies on the experience of the test performer and the signal processor, and availability of prior knowledge of the inspected timber pole. While the presented investigation was conducted on numerical data with impact on top of a pole, in future, it is intended to study the method for impact from the side of a pole, as well as an experimental validation on real in-service timber utility pole will be conducted. REFERENCES Bendat, J. S. and Piersol, A. G., (1993), Engineering applications of correlation and spectral analysis, J. Wiley, United States. Chree, C., (1889), "The Equations of an Isotropic Elastic Solid in Polar and Cylindrical Co-ordinates their Solution and Application", Transactions of the Cambridge Philosophical Society, Vol. 14, pp Crews, K. H., A., (2000), "'Strength assessment of timber utility poles in Australia", New Zealand Timber Design Journal, Vol. 9. Davis, A. G., (1998), "Nondestructive Test Methods for Evaluation of Concrete in Structures", American Concrete Institute, Farmington Hills, Michigan, pp. 62. Francis, L. N., J., (2006), "'A Review Australian Timber Pole Resources for Energy Networks", Department of Primary Industries & Fisheries. Holt, J., Shunyi, C. and Douglas, R., (1994), "Determining lengths of installed timber piles by dispersive wave", Transportation research record, pp Huang, Y. H. and Ni, S. H., (2012), "Experimental study for the evaluation of stress wave approaches on a group pile foundation", NDT and E International, Vol. 47, pp Kent, H., (2006), "Options for the continued supply of power poles", Queensland Department of Primary Industries and Fisheries, Presentation for the March 2006 Australian Wood Pole Resources Workshop. Larry, M., Olson, D., Jalinoos, F. and Aquad, M. F., (1998),"Determination of Unknown Subsurface Bridge Foundation", International Water Resources Engineering Conference, Memphis, Tennessee, USA. Love, A. E. H., (2013), A treatise on the mathematical theory of elasticity, Cambridge University Press, United Kingdom. Paquet, J., (1968), "Etude Vibratoire des Pieux en Beton: Reponse Harmonique et Impulsionelle, Application au Controle", Annales de L'Institut Technique du Batiment et Des Travaux Publics, Annales. I.T.B., Vol Subhani, M., Li, J. C., Gravenkamp, H. and Samali, B., (2013), "Effect of elastic modulus and poisson's ratio on guided wave dispersion using transversely isotropic material modelling", Advanced Materials Research, Vol. 778, pp ACMSM