Analysing motion patterns in the cervical and lumbar spine. A new discrimination parameter of pathology

USE OF A MAGNETIC TRACKING DEVICE TO DETERMINE LUMROSACRAL MOME3’l-S DURING ASYMMETRIC LIFTING J.S. Day, G.A. Dumas Department of Mechanical Engineering, McLaughlin Hall Queen’s University, Kingston, ON, Canada INTRODUCTION: Magnetic tracking provides an inexpensive means to automatically track the position and orientation of multiple sensors. Until now there have been few efforts to use magnetic tracking in conjunction with link segment modeling. The objective of this work was to assess the use of a magnetic tracking device and link segment model to calculate three-dimensional external moments at LYSl during three lifting tasks. METHODS: A seven segment upper body model (upper arms, lower arms, 3 trunk segments and the load) was developed based on the inverse dynamics approach. Anthropometric data’ were used to determine the magnitude and position of the segment centres of gravity. Sensors were attached to each segment and located with respect to the centres so that each sensor could be used to track the position and orientation of one segment. Finally, the three dimensional equations of motion were applied in order to determine force and moment vectors at the location of I5/S 1. Two Polhemus Fast&s were used in this study. Each device was capable of tracking four sensors at a rate of 28 Hz. A long range transmitter was used to track the three trunk segments and the load. Upper and lower arm segments were tracked using a standard transmitter. All data were calibrated to correct for distortion of the magnetic field. Task I (symmetric lift) consisted of lifting a 1Skg box from the floor to a table at waist height. In the other two tasks, the subject lifted the same box from floor level through a 90 degree turn to his right and placed it on the same table. For Task II (twisting lift) the subject was asked to keep his feet planted in an intermediary position where he could reach both the beginning and end points. For Task III (turning) lift, the subject was asked to begin and end the lift facing the box and to move his feet during the task. RESULTS & DISCUSSION: Five lifts were recorded for one male volunteer (m=67kg; h=169cm). The maximum moments about each axis and the moments about each axis at the time of peak resultant moment were calculated in the body coordinate system (see figure). These results, tabulated below, are comparable to those reported previously2.3.

ANALYSiNG MOTION PAlTERNS IN TIiR CERVICAL AND LUMBAR SPINE. A NEW DISCRIMINATION PARAMETER OF PATHOLOGY V. Feipel , B. Rondelet , J.P. Le Pallet, F. Vogt, M. Rwze Universiti Libre de Bmxelles INTRODUCTION: In cervical and lumbar spine diseases, static (morphologic) diagnosis tools often do not provide useful information. Results of functional investigations reported in the literature provide evidence for hyper- and hypo-mobility in patients. This study aimed at comparing patterns of global cervical and lumbar spine motion in patients with various pathologies to asymptomatic volunteers. We used a reliable, non invasive and inexpensive technique, spatial electrogoniometry. METHODS: Cervical spine motion was investigated in 150 asymptomatic voIunteers and 42 patients. For the lumbar spine, 80 volunteers and 25 chronic low back pain (LBP) patients were analysed. Motion was tracked using a commercial three-dimensional electrogoniometer (CA 6000 Spine Motion Analyzer, Orthopedic Systems Inc., Union City, CA, USA) at a sampling rate of 100 Hz. The goniometer is attached to the subject using appropriate harnesses and/or a helmet. Four repetitions of maximal active movements (flexion-extension, right and left rotation, right and left bending) were executed by the subjects. Reproducibility was evaluated by a double testretest in ten volunteers. Maximal ranges of main motion and out-of-plane components and patterns of motion curves were analysed qualitatively and using fitting of sixth order polynomials. Determination coefficients (15) were compared between patients and volunteers. RESULTS: Motion ranges were in agreement with the ones reported in the literature. In comparable age groups, significant differences between volunteers and patients in motion ranges were rare. Only some out-of-plane components differed significantly. Motion patterns were, however, different. Figure 1 shows cervical spine lateral bending curves of patients and volunteers. Qualitatively, patients displayed less harmonic curves, with irregularities and a plateau-like appearance. Similar features were observed in LBP patients. Determination coefficients were significantly reduced in patients. I

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s.d. 3 10 12 4 2 6 5 5 17 1 CONCLUSION: Magnetic tracking provides a versatile, inexpensive method for the analysis of asymmetric lifting. REFERENCES: 1. ?atsiorsky et al, Advances in Sciences and Technology in the USSR: Contemporary Problems of Biomechanics, CRC Press, t990. 2. Plamondonet al, Clin. Biomech., 11, 101-I 10. 1996. 3. Kromodihardjo & Mital, J. Biomech. Engng. 109, 132-138, 1987. ACKNOWLEDGEMENTS: NSERC, URIF, DuPont Canada (Kingston) CORRESPONDENCE: G.A. Dumas, [email protected] phone (613) 545-2648, fax. (613) 545-6489

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Figure 1. Cervical spine lateral bending curves. DISCUSSION: Although cervical or lumbar spine motion ranges may remain within normal limits in patients, motion patterns differed qualitatively and quantitatively from the ones observed in asymptomatic volunteers. These alterations could, for instance, be related to modified proprioception. CONCLUSION: Cervical and iumbar spine motion pattern analysis may be used as a discrimination parameter in patients in which anatomic lesions are not clear. Other joints might benefit from similar analysis. CORRESPONDENCE: V. Feipel, Lab. Funct. Anat., U.L.B. (CP619). 808 route de Lennik, B1070 Brussels, Belgium Tel:++32-2-5556329/Fax:++32-2-5556378, [email protected]

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