Beard, D. J.

Chen, M

Gibbons, Christopher L. M. H.

Gill, H. S.

Monk, A. P.

Murray, D. W.

This paper describes a motion analysis ultrasound system (MAUS) designed for the in-vivo study of the kinematics of patellofemoral joints (PFJ) in both normal and replaced knees. This system utilises non-iodising radiation to effectively acquirekinematic data during weight-bearing activities. Validation studies on a phantom established that the measurement accuracy of the system was 1.43 mm. A clinical validation trial is included

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        Citation for published version:Monk, AP, Chen, M, Gibbons, CLMH, Beard, DJ, Gill, HS & Murray, DW 2013, 'Measurement of in-vivo patellakinematics using motion analysis and ultrasound (MAUS)' Paper presented at IEEE International Symposium onMedical Measurements and Applications, Gatineau, Quebec, Canada, 4/05/13 - 5/05/13, .Publication date:2013Document VersionPeer reviewed versionLink to publication© 2013 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all otheruses, in any current or future media, including reprinting/republishing this material for advertising or promotionalpurposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of anycopyrighted component of this work in other worksUniversity of BathGeneral rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Download date: 13. May. 2019Measurement of in-vivo Patella Kinematics UsingMotion Analysis and Ultrasound (MAUS)AP Monk∗, M Chen†, S Mellon∗, CLMH Gibbons∗, DJ Beard∗, HS Gill‡ and DW Murray∗∗NDORMS, University of Oxford, Windmill Road, Oxford, UK OX3 7HE†School of Computing and Mathematics, University of Derby, Kedleston Road, Derby, UK DE22 1GB‡Dept of Mechanical Engineering, University of Bath, Claverton Down, Bath, UK, BA2 7AYAbstract—This paper describes a motion analysis ultrasoundsystem (MAUS) designed for the in-vivo study of the kinematicsof patellofemoral joints (PFJ) in both normal and replaced knees.This system utilises non-iodising radiation to effectively acquirekinematic data during weight-bearing activities. Validation stud-ies on a phantom established that the measurement accuracy ofthe system was 1.43 mm. A clinical validation trial is included.I. INTRODUCTIONTotal knee replacement (TKR) is the standard treat-ment for end-stage osteoarthritis when conservative mea-sures have failed. Despite excellent reported survivorship, thepatellofemoral joint is the leading site for complications. It ispossible that this might be due to abnormal kinematics. Whilstthere is a wealth of data regarding sagittal plane kinemat-ics, previous attempts to study coronal plane patellofemoralkinematics have suffered from methodological drawbacks.Studies involving the use of fluoroscopy, CT and MRI haveencountered difficulties with the patella being obscured by thecomponents and/or metal artefact [16] [18].This paper describes a novel technique for measuring coro-nal plane kinematics by combining Motion Analysis with Ul-traSound (MAUS). We also present our two pre-clinical studieson ascertaining the accuracy of the measurement technique.II. PREVIOUS WORKThe kinematics of PFJ have been studied both in-vitro andin-vivo. The former relies on the use of cadaveric or post-mortem specimens [1] [13] [19]. During such kinematic as-sessments of the knee joint, the experimental procedure usuallyaims to represent simplified physiological loading in order tosimulate realistic positions of the femur, tibia and patella.This has traditionally been achieved via the application ofload through the quadriceps tendons following intra-medullaryfixation of the femur and the tibia to a rig [11] [14].In-vivo measurements of everyday activities such as squat-ting, normal gait and stepping activity provide more relevantphysiological data [17], as pain is most frequently experiencedduring these common weight-bearing routines. However, ac-quiring in-vivo motion data is often complicated by the prac-ticality of imaging the knee anatomy. Planar radiographs and3D tomography (CT, MRI) can produce detailed images ofthe knee joint but they impose a high degree of restriction onthe range of weight-bearing activities feasible within the con-fined space. Furthermore, both x-ray and magnetic resonancedevices are inappropriate for subjects with prosthetic kneejoint. Radiation dosage from x-ray based imaging techniquesis also a concern for many clinical practices. Nonetheless,these image modalities have been shown to be successful inmeasuring PFJ kinematics in native knees [9] [15].The use of ultrasound for assessing anatomical PFJ ab-normalities is well established [2] [10] [12]. The advantagesof ultrasound are that it does not involve ionising radiationand can be used to image the knee joint in the presenceof metallic prostheses. Previous attempts have been made toquantify coronal plane patella movements during flexion andextension using ultrasound; however these were compromisedby measurement errors of up to 6.4 mm (2×SD) due toissues with securing the probe to the leg via bracing [6] [16].The remainder of this article will focus on discussing themethodology of our ultrasound based motion analysis and itsvalidation.III. METHODSA. OverviewA multiple camera motion capture system was used tocapture images of reflective markers mounted on subjectslower limbs and an ultrasound probe. A spatial mappingbetween the ultrasound image and the motion capture systemwas established. Therefore, the ultrasound could be used todetermine the locations of the patella and bony landmarks ontibial and femoral segments, during a squat exercise.The MAUS technique can be geometrically described by anumber of coordinate systems in which anatomical landmarksare measured (see Figure 1). Gait was measured in referenceto the motion system; whereas the bony landmarks weremeasured in-vivo in the ultrasound image coordinate system.It is often more desirable to describe measurements in acommon coordinate system referred to as the global coordinatesystem. Since both gait and the ultrasound probe were trackedin the VICON coordinate system, it was designated as theglobal coordinate frame. The ultimate aim of the system is totransform the ultrasound measurement into the global space,thus unify the gait data with the in-vivo landmark data.B. Calibration and Tracking of Ultrasound ProbeUltrasound probe calibration is a process in which theunknown transformation from the image space to the globalFig. 1. The spatial relationship between the ultrasound image and the motioncapture lab is related by a tracked ultrasound probe.Fig. 2. The point based calibration phantom used in MAUS; (a) Top viewof the box containing fiducial markers; (b) Reflective fiducial markers; (c)Ultrasound image of the markers.coordinate system is calculated. This was achieved by cross-referencing fiducial markers, whose coordinates were knownin both global and ultrasound systems. These correspondingcoordinates are related to each other by a transformationconsisting of a rotation and translation. Hsu et al. discussedand reviewed computational techniques involved in calibratingfreehand ultrasound for the purpose of 3D reconstruction [7][8].The MAUS system used a calibration phantom consistingof 10 reflective markers for this purpose (see Figure 2a).The markers were fixed within a box consisting of a gridof holes of 2 mm diameter at 10 mm intervals on its base-plate and arranged in a 3-3-4 interlaced formation (Figure 2b).This particular arrangement was adopted to ensure the planeformed by the markers can be unambiguously oriented. Sincethese markers were reflective and detectable under the opticalmotion capture system, their global coordinates can be directlylocalised.Once the position of each calibration marker was deter-mined, the calibration box remained stationary. The box wasthen filled with water to allow the propagation of ultra-sound. The ultrasound image of fiducial markers was obtainedthrough the surgical membrane at the front of the box (seeFigure 2c). Each marker in the image was delineated andits centroid used as its image space position. The positionand orientation of the ultrasound probe was simultaneouslyrecorded via a sync trigger when the ultrasound image wascaptured. This resulted in the following set of known values:• Coordinates of each calibration marker in the global spacep¯.• Coordinates of each calibration marker in the ultrasoundimage space q¯.• Position and orientation of the ultrasound probe in theglobal space denoted by a 4×4 affine transformation M.For ultrasound, the relationship between the reconstructed p¯′and q¯ can be written as:p¯′ = sx 0 00 sy 00 0 1Rq¯ + t¯ (1); where sx and sy are the image scaling factors. All points inthe image space are assumed to be on the xy plane, thus thescaling factor for z is 1. The extrinsic 3×3 rotation matrix Rand translation vector t¯ were solved using the iterative closestpoint (ICP) method. Further optimisation was performed onall parameters by minimising the cost function (Equation 2)by using the Levenberg-Marquardt algorithm.c(sx, sy,R, t¯) = ‖p¯′ − p¯‖2 (2)Since we were interested in tracking the pose of theultrasound image plane, the transformation D between thearbitrarily attached tracking sensor and the image plane canbe calculated by using Equation 3.D = M[R t¯0 1]−1(3)C. Reconstruction of the Lower LimbThe primary purpose of calibrating the ultrasound probewith a stationary phantom is to enable the reconstructionof scanned anatomical landmarks into the global coordinatespace. Given an ultrasound scanned landmark obtained attime t, its reconstructed 3D position p¯ was computed byEquation 4;p¯ = MtD sx 0 00 sy 00 0 1 q¯ (4)where denotes the pose of the ultrasound probe at time t; q¯ isthe location of a landmark in image space; sx, sy and D arethe calibrated parameters.The lower limb was divided into four orientable segments,i.e. pelvis, femur, tibia and patella. Each segment was con-structed by a collection of landmarks including both recon-structed ultrasound landmark and skin-based markers. Figure 3shows the skin markers attached to a subject. These markerswere primarily used to determine the gait stance, e.g. inducingflexion angle.The reconstruction of the patella position was achieved byusing four ultrasound-scanned markers around the peripheralof the patella (see Figure 4).IV. RESULTS AND DISCUSSIONA. Accuracy Assessment and ValidationThe accuracy of the measured kinematic data is influencedby the following factors:1) Systemic accuracy of the motion capture system: Themean results across all sessions of data collection dur-ing was 0.28 mm (SD=0.05 mm). The samples wereFig. 3. A reference set of skin markers attached to the subject for gaitanalysis.Fig. 4. The ultrasound-scanned landmarks used for defining the geometryof the patella.obtained from each sensor using a calibration wand withknown geometric configuration (see Table I).2) Algorithmic accuracy of the calibration process: Theresidual error was calculated based on the RMS dis-tances between the computed fiducial markers and theiractual positions in the global coordinate system (seeTable II). From sixteen independent calibration trials,the overall error was 1.428 mm.3) Observer measurement error: Two clinicians who werefamiliar with the operation of ultrasound scanner wererecruited as two independent observers. Each observerrepeated measurements of the position of 7 anatomicallandmarks, in four different positions on four subjects(see Figure 5). Observers using the ultrasound systemwere able to produce more accurate and consistentkinematic measurements compared to methods based onclamps and skin-markers (see Figure 6).B. Pre-clinical ValidationThe main motivation of implementing this system was toexamine the coronal plane PFJ kinematics of both native andreplaced knees. The MAUS technique was validated on acohort of 11 subjects including native and replaced knees.Each subject performed a squatting exercise during the dataVICON Motion Capture System ErrorSensor Sample Count Spatial Error (mm)1 4166 0.2432 4095 0.2503 4733 0.2714 1004 0.2755 1994 0.4546 6400 0.2167 1330 0.3448 2277 0.3929 4332 0.21510 3776 0.25311 4167 0.204Mean 0.28 mm(SD=0.05)TABLE IVICON MOTION CAPTURE SYSTEM ERROR MEASURED FROM EACHSENSOR.Fig. 5. A clinician using the MAUS system to measure the position of patellaof a patient.RMS errorsPosition x(mm) y(mm) z(mm)1 0.322 0.774 1.1715.439 0.394 1.2042.095 1.006 3.8360.142 0.085 0.8462 0.541 0.490 4.6640.469 0.040 4.8192.045 0.301 6.5040.052 0.273 1.5933 1.051 2.367 1.3350.637 2.724 0.7410.676 0.324 2.1460.835 0.427 1.6374 2.179 0.435 3.4133.162 0.406 2.7890.301 0.316 0.8120.243 0.256 0.232Mean 1.262 0.664 2.359Total Error = 1.428 mmTABLE IIULTRASOUND PROBE CALIBRATION ERRORS MEASURED FROM 16INDEPENDENT TRAILS IN 4 DIFFERENT SPATIAL POSITIONS.collection session. The kinematics were analysed at sevendiscrete flexion angles at full extension, 20, 30, 45, 60 and 90.Our initial observations confirmed the difference in kinematicpattern in native and replaced knees (see Figure 7).Fig. 6. Inter- and intra-observation study shows accurate and repeatable in-vivo measurement of patella displacement versus knee flexion. MAUS demon-strates better accuracy compared to patella clamp [18] and skin movementartefact [3] [4] [5].Fig. 7. Mediolateral movements of the patella measured in the coronal plane.V. CONCLUSIONThis study has demonstrated the implementation and appli-cation of an ultrasound based motion analysis technique forin-vivo measuring the motion of the patella in relation to distalfemur and proximal tibia. We specifically devised a calibrationmethod using reflective fiducial markers to facilitate the inte-gration with existing motion capture system. The system hasbeen validated both on phantom using fiducial markers and onsubjects with native and replaced knees. The 3D reconstructionhas enabled clinicians to study the kinematics of PFJ inplanes that were restricted in other imaging modalities. Afull clinical trial using this measurement technique is currentlybeing conducted.Currently the reconstruction of ultrasound-scanned land-marks is performed as an offline process. In our future work,this reconstruction algorithm can be systematically integratedwith the VICON software system. The integration can lead toa further improvement in the temporal alignment of gait andultrasound data.ACKNOWLEDGMENTThe authors would like to thank the gait laboratory atNuffield Orthopaedic Centre in Oxford for providing themotion capture facility.REFERENCES[1] Y. S. Anouchi, L. A. Whiteside, A. D. Kaiser, and M. T. Milliano, “Theeffects of axial rotational alignment of the femoral component on kneestability and patellar tracking in total knee arthroplasty demonstratedon autopsy specimens.” Clin Orthop Relat Res, vol. 187, no. 287, pp.170–177, 1993.[2] R. P. Barker, J. C. Lee, and J. C. Healy, “Normal sonographic anatomyof the posterolateral corner of the knee.” ARJ Am J Roentgenol, vol.192, no. 1, pp. 73–79, 2009.[3] A. Cappozzo, F. Catani, A. Leardini, M. G. Benedetti, and U. D.Croce, “Position and orientation in space of bones during movement:experimental artefacts,” Clinical Biomechanics, vol. 11, pp. 90–100,1996.[4] R. M. Ehrig, W. R. Taylor, G. N. Duda, and M. O. Heller, “A survey offormal methods for determining the centre of rotation of ball joints,” J.Biomech., vol. 39, pp. 2798–2809, 2006.[5] S. S. Gamage and J. Lasenby, “New least squares solutions for estimat-ing the average centre of rotation and the axis of rotation,” J. Biomech.,vol. 35, pp. 87–93, 2002.[6] L. Herrington, I. McEwan, and J. Thom, “Quantification of patellaposition by ultrasound scanning and its criterion validity.” UltrasoundMed. Biol., vol. 32, no. 12, pp. 1833–1836, 2006.[7] P. W. Hsu, R. W. Prager, A. H. Gee, and G. M. Treece, “Rapid, easyand reliable calibration for freehand 3d ultrasound,” Ultrasound Med.Biol., vol. 32, no. 6, pp. 823–835, 2006.[8] P. W. Hsu, G. M. Treece, R. W. Prager, N. E. Houghton, and A. H. Gee,“Comparison of freehand 3-d ultrasound calibration techniques using astylus,” Ultrasound Med. Biol., vol. 34, no. 10, pp. 1610–1621, 2008.[9] F. Iranpour, A. M. Merican, F. R. Baena, J. P. Cobb, and A. A. Amis,“Patellofemoral joint kinematics: the circular path of the patella aroundthe trochlear axis,” J. Orthop. Res., vol. 28, no. 5, pp. 589–594, 2010.[10] F. W. Joshi and R. P. Heatley, “Imaging patellofemoral joint usingultrasound: a preliminary report. a comparison between normal subjectsand patients with patellar maltracking,” Knee, vol. 5, pp. 129–135, 1998.[11] T. Luyckx, K. Didden, H. Vandenneucker, L. Labey, B. Innocenti,and J. Bellemans, “Is there a biomechanical explanation for anteriorknee pain in patients with patella alta? influence of patellar height onpatellofemoral contact force, contact area and contact pressure,” J. BoneJoint Surg. Br., vol. 91, no. 3, pp. 344–350, 2009.[12] C. Nofsinger and J. G. Konin, “Diagnostic ultrasound in sports medicine:current concepts and advances,” Sports Med Arthrosc, vol. 17, no. 1, pp.25–30, 2009.[13] S. Ostermeier, O. Buhrmester, C. Hurschler, and C. Stukenborg-Colsman, “Dynamic in vitro measurement of patellar movement aftertotal knee arthroplasty: an in vitro study,” BMC Musculoskeletal Disor-ders, vol. 6, no. 30, 2005.[14] A. J. Price, P. T. Oppold, D. W. Murray, and A. B. Zavatsky, “Simul-taneous in vitro measurement of patellofemoral kinematics and forcesfollowing oxford medial unicompartmental knee replacement,” J. BoneJoint Surg. Br., vol. 88, no. 12, pp. 1591–1595, 2006.[15] J. M. Scarvell, P. Smith, K. M. Refshauge, H. R. Galloway, and K. R.Woods, “Does anterior cruciate ligament reconstruction restore normalknee kinematics?: A prospective mri analysis over two years,” J. BoneJoint Surg. Br., vol. 88, no. 3, pp. 324–30, 2006.[16] Y. F. Shih, A. M. Bull, A. H. McGregor, and A. A. Amis, “Active patellartracking measurement: a novel device using ultrasound,” Am. J. SportsMed., vol. 32, no. 5, pp. 1209–1217, 2004.[17] A. von Porat, M. Henriksson, E. Holmstrom, and E. M. Roos, “Kneekinematics and kinetics in former soccer players with a 16-year-old aclinjury - the effects of twelve weeks of knee-specific training,” BMCMusculoskeletal Disorders, vol. 8, no. 35, 2007.[18] N. A. Wilson, J. M. Press, J. L. Koh, and R. W. Hendrix, “In vivononinvasive evaluation of abnormal patellar tracking during squattingin patients with patellofemoral pain,” JBJS (Am), vol. 91, no. 3, pp.558–566, 2009.[19] A. B. Zavatsky, “A kinematic-freedom analysis of flexed-knee-stancetesting rig,” J. Biomech., vol. 30, no. 3, pp. 277–280, 1997.

Measurement of <em>in-vivo</em> patella kinematics using motion analysis and ultrasound (MAUS)

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Measurement of <em>in-vivo</em> patella kinematics using motion analysis and ultrasound (MAUS)

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