Real-time measurement and analysis of the mechanical response of the spine to manipulative therapy

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Real-time measurement and analysis of the mechanical response of the spine to manipulative therapy


Author: Tsung, Yuk-san Bonnie
Title: Real-time measurement and analysis of the mechanical response of the spine to manipulative therapy
Degree: Ph.D.
Year: 2006
Subject: Hong Kong Polytechnic University -- Dissertations
Spine -- Diseases -- Treatment
Manipulation (Therapeutics)
Real-time data processing
Department: Dept. of Rehabilitation Sciences
Pages: xxiv, 360 p. : ill. ; 30 cm
Language: English
InnoPac Record:
Abstract: Manual therapy is frequently employed in the clinical assessment and treatment of low back pain. Recent research has provided fundamental information about the biomechanical characteristics of techniques such as posteroanterior (PA) and rotational mobilisation. However, there is a need to develop a method of determining their biomechanical effects in real time so that clinical assessment can be made objectively and immediately. This would also provide useful feedback to students and would help them produce the desired biomechanical effects. A real-time measurement method was thus developed in this study for examining the mechanical effects of PA and rotational mobilisation. The loads applied during mobilisation were measured by a force plate mounted underneath the manipulation couch, and the resulting spinal motions were recorded by an electromagnetic tracking device (3 SPACE Fastrak, Polhemus, Cochester, VT, USA). The data obtained were acquired and analysed by specially developed software and then displayed in real time. The purpose of the present work was (1) to examine the stiffness properties of the spine during PA and rotational mobilisation using the method developed, and (2) to examine the effects of PA mobilisation on the stiffness and pain response of the lumbar spine. PA stiffness was generally defined as the ratio of the mobilisation force to the posteroanterior displacement of the vertebra being mobilised. This definition was unsatisfactory as it could be affected by the geometry of the spine and considers PA as a simple displacement of the vertebra in the posteroanterior direction. It was also found that the derived stiffness could be affected by extrinsic factors such as the firmness of the underlying mattress. Previous research showed PA mobilisation was essentially a three-point bending of the spine. It would therefore be more appropriate to derive the bending stiffness of the spine. The validity of measuring the PA stiffness with 3 point bending theory was tested with twenty healthy volunteers (20 males, mean age = 30.6 +- 5.4 years, mean height = 1.71 +- 0.06m, mean weight = 65.6 +- 7.8 kg). Grade III PA mobilisation force as described by Maitland (Maitland, 1986) was applied at each segment of lumbar spine. The mobilising force and spinal movement were measured with the real-time measurement system developed in current study. The bending stiffness of the spine was then determined with the moment area method. The data provided by the measurement system was considered to be sufficiently reliable (ICC ranging from 0.85 to 0.98). The mean PA force applied was 102.87 + 39.52N and the corresponding curvature change was 3.66 + 0.82. It was shown that there were no significant differences in bending stiffness among different spinal levels. The method of modelling the mobilising spine as a homogenous beam under three-point bending was then justified. An attempt was also made to quantify the load applied and resulting movements of spine during rotational mobilisation. Twenty healthy volunteers (14 males and 6 females, mean age = 28.4+-6.3 years, mean height = 1.71+-0.08m, mean weight = 62.5+-11.6 kg) were recruited. In the starting positions, the lumbar spines were found to be flexed, axially rotated to the right and laterally bent to the left. As the mobilisation grade increased, the spine was axially rotated further into the range. Rotational mobilisation was found to induce oscillatory moments and movements of the spine in all three anatomical planes. It is not limited to be a single plane movement as its name implied. The twisting moment and movement were generally accompanied by lateral bending moment and movement in the opposite direction. Rotational stiffness of the spine was also derived from the twisting moment and axial rotation movement data. The spine was found to exhibit different stiffness values with different grades of mobilisation (p<0.05). Finally, the effects of posteroanterior mobilisation on the bending stiffness and pain response of the lumbar spine of the low back pain (LBP) patient were examined. Both LBP and asymptomatic subjects were examined in this study. Nineteen LBP subjects (mean age = 39.05 +- 7.39, mean height = 1.67 +- 0.09m, mean weight = 62.96 +- 11.50 kg) and twenty normal subjects (mean age = 33.4 +- 5.11, mean height = 1.66 +- 0.08m, mean weight = 59.93 +- 9.14 kg) participated in this clinical study. PA stiffness of the spine was determined using the moment area method mentioned above. Subjects were provided with an electronic switch to indicate the onset of pain during mobilisation. The active ranges of motions of the lumbar spine were also assessed before and after mobilisation. PA mobilisation was found to produce significant reduction in the bending stiffness and increase in the lumbar curvature of the spine. The bending stiffness of the patients was reduced to a level that was similar to that of asymptomatic subjects before mobilisation. Significant increases in the active ranges of movements were also observed for both asymptomatic and back pain subjects. The back pain patients were able to tolerate larger magnitude of PA force at the onset of pain after mobilisation. The magnitude of pain was also found to be reduced significantly after mobilisation. The above findings suggest that the mechanical properties of the spine were altered after mobilisation, and the improvement in pain behaviour and spinal mobility might be related to the changes in mechanical properties of the spine. It is suggested that the real-time measurement method developed in this study may be used as a routine clinical tool. The experimental method could be made more economical by measuring the loads with manipulation couch fitted with three-dimensional load cells and the spinal movements with inertial sensors such as gyroscopes. Using the method developed, this study has provided new insights into the stiffness properties of the lumbar spine and important clinical information about the effects of mobilisation on PA stiffness, pain and spinal mobility.

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