Axial-transmission acoustics have shown to be a promising technique to measure individual bone pr... more Axial-transmission acoustics have shown to be a promising technique to measure individual bone properties and detect bone pathologies. With the ultimate goal being the in-vivo application of such systems, quantification of the key aspects governing the reliability is crucial to bring this method towards clinical use. This work presents a systematic reliability study quantifying the sources of variability and their magnitudes of in-vivo measurements using axial-transmission acoustics. 42 healthy subjects were measured by an experienced operator twice per week, over a four-month period, resulting in over 150000 wave measurements. In a complementary study to assess the influence of different operators performing the measurements, 10 novice operators were trained, and each measured 5 subjects on a single occasion, using the same measurement protocol as in the first part of the study. The estimated standard error for the measurement protocol used to collect the study data was ∼ 17 m/s (∼...
1, 2 Daniel Baumgartner, 3 Georg Osterhoff, 3 Clément M.L.Werner, 4 Hans Gerber and 1 Philippe Fa... more 1, 2 Daniel Baumgartner, 3 Georg Osterhoff, 3 Clément M.L.Werner, 4 Hans Gerber and 1 Philippe Favre 1 Laboratory for Orthopaedic Research, Department of Orthopaedics, Balgrist, University of Zurich, Switzerland 2 Zurich University of Applied Sciences, Institute for Mechanical Systems, Winterthur, Switzerland, email: [email protected] Division of Trauma Surgery, University Hospital Zurich, Switzerland 4 Institute for Biomechanics, ETH Zürich, Switzerland
Background: Surgery for disc herniations can be complicated by two major problems: painful degene... more Background: Surgery for disc herniations can be complicated by two major problems: painful degeneration of the spinal segment and re-herniation. Therefore, we examined an absorbable polyglycolic acid (PGA) biomaterial, which was lyophilized with hyaluronic acid (HA), for its utility to (a) re-establish spinal stability and to (b) seal annulus fibrosus defects. The biomechanical properties range of motion (ROM), neutral zone (NZ) and a potential annulus sealing capacity were investigated. Methods: Seven bovine, lumbar spinal units were tested in vitro for ROM and NZ in three consecutive stages: (a) intact, (b) following nucleotomy and (c) after insertion of a PGA/HA nucleus-implant. For biomechanical testing, spinal units were mounted on a loading-simulator for spines. In three cycles, axial loading was applied in an excentric mode with 0.5 Nm steps until an applied moment of ± 7.5 Nm was achieved in flexion/extension. ROM and NZ were assessed. These tests were performed without and with annulus sealing by sewing a PGA/HA annulus-implant into the annulus defect. Results: Spinal stability was significantly impaired after nucleotomy (p < 0.001). Intradiscal implantation of a PGA-HA nucleus-implant, however, restored spinal stability (p < 0.003). There was no statistical difference between the stability provided by the nucleus-implant and the intact stage regarding flexion/extension movements (p = 0.209). During the testing sequences, herniation of biomaterial through the annulus defect into the spinal canal regularly occurred, resulting in compression of neural elements. Sewing a PGA/HA annulus-implant into the annulus defect, however, effectively prevented herniation. Conclusion: PGA/HA biomaterial seems to be well suited for cell-free and cell-based regenerative treatment strategies in spinal surgery. Its abilities to restore spinal stability and potentially close annulus defects open up new vistas for regenerative approaches to treat intervertebral disc degeneration and for preventing implant herniation.
The aim of this study was to determine the mean distances of facial movements in 24 healthy indiv... more The aim of this study was to determine the mean distances of facial movements in 24 healthy individuals aged between 22 and 70 years, using the digitised three-dimensional video-analysis system developed by Frey et al. The subjects were divided into three groups of eight. The first group consisted of individuals aged between 20 and 30 years (mean^s.d. ¼ 25.0^2.33 years). Subjects in the second group were aged between 40 and 50 years (mean^s.d. ¼ 46.8^2.53 years), and the third group consisted of subjects aged between 60 and 70 years (meanŝ .d. ¼ 63.6^3.07 years). In all groups the sexes were equally represented. No subject had had treatment to the face, nor did they have paralysis, scars or diseases of the skin. Males showed larger movements of the face than females, on average by 1.40^0.73 mm (15.08%). Subjects aged between 60 and 70 years demonstrated the largest movements of the face. The evaluation of facial movements in 24 healthy volunteers showed that sex and age affect facial dynamics. Thus study generated three-dimensional standard values for healthy facial movements.
Background: During rapid movements of the arm the transversus abdominis muscle (TA) is typically ... more Background: During rapid movements of the arm the transversus abdominis muscle (TA) is typically activated before the prime mover (deltoid), to stabilise the spine before the impending postural disturbance. This feedforward activity is compromised in patients with low back pain (LBP), although the phenomenon has not been investigated widely, because of the invasiveness of the assessment technique [fine-wire intramuscular electromyography (iEMG)]; we examined whether ultrasound tissue Doppler imaging (TDI) could represent a non-invasive alternative. Methods: 14 subjects (8M, 6F;23.0±2.0 yrs) performed 10 repetitions each of rapid shoulder flexion, extension and abduction, whilst surface EMG recordings from medial deltoid, and iEMG and M-mode TDI tissuevelocity recordings from the contralateral TA, internal (IO) and external (EO) oblique muscles were made. Muscle onsets were determined by visual inspection of blinded EMG and TDI signals using custom-built software (MATLAB) and expressed relative to the deltoid onset (values −150ms to + 50ms = feed-forward). Results: The TDI-determined onsets were later than those of iEMG by 32.5 (SD 32.8) ms for TA, 17.9 (SD 23.3) ms for IO, and 15.8 (SD 25.3) ms for EO. The methods showed moderately high, significant correlations: r = 0.55 (TA); r = 0.61 (IO); r = 0.56 (EO) (each p< 0.0002). Conclusion: The mean differences between the methods were likely due to electromechanical delay. The SDs of the differences were comparable to those for repeated measurements with either technique. TDI appears to be a valid means of assessing abdominal muscle feed-forward activity, and should allow this phenomenon to be investigated in larger numbers of LBP patients. Support: NFP53–405340–104787/1.
Although total knee arthroplasty (TKA) has become a standard surgical procedure for relieving pai... more Although total knee arthroplasty (TKA) has become a standard surgical procedure for relieving pain, knowledge of the in vivo knee joint kinematics throughout common functional activities of daily living is still missing. The goal of this study was to analyse knee joint motion throughout complete cycles of daily activities in TKA subjects to establish whether a significant difference in joint kinematics occurs between different activities. Using dynamic videofluoroscopy, we assessed tibio-femoral kinematics in six subjects throughout complete cycles of walking, stair descent, sit-to-stand and stand-to-sit. The mean range of condylar anterior-posterior translation exhibited clear task dependency across all subjects. A significantly larger anterior-posterior translation was observed during stair descent compared to level walking and stand-to-sit. Local minima were observed at approximately 308 flexion for different tasks, which were more prominent during loaded task phases. This characteristic is likely to correspond to the specific design of the implant. From the data presented in this study, it is clear that the flexion angle alone cannot fully explain tibio-femoral implant kinematics. As a result, it seems that the assessment of complete cycles of the most frequent functional activities is imperative when evaluating the behaviour of a TKA design in vivo.
Videofluoroscopy has been shown to provide essential information in the evaluation of the functio... more Videofluoroscopy has been shown to provide essential information in the evaluation of the functionality of total knee arthroplasties. However, due to the limitation in the field of view, most systems can only assess knee kinematics during highly restricted movements. To avoid the limitations of a static image intensifier, a moving fluoroscope has been presented as a standalone system that allows tracking of the knee during multiple complete cycles of level- and downhill-walking, as well as stair descent, in combination with the synchronous assessment of ground reaction forces and whole body skin marker measurements. Here, we assess the ability of the system to keep the knee in the field of view of the image intensifier. By measuring ten total knee arthroplasty subjects, we demonstrate that it is possible to maintain the knee to within 1.8 ± 1.4 cm vertically and 4.0 ± 2.6 cm horizontally of the centre of the intensifier throughout full cycles of activities of daily living. Since con...
Combined knowledge of the functional kinematics and kinetics of the human body is critical for un... more Combined knowledge of the functional kinematics and kinetics of the human body is critical for understanding a wide range of biomechanical processes including musculoskeletal adaptation, injury mechanics, and orthopaedic treatment outcome, but also for validation of musculoskeletal models. Until now, however, no datasets that include internal loading conditions (kinetics), synchronized with advanced kinematic analyses in multiple subjects have been available. Our goal was to provide such datasets and thereby foster a new understanding of how in vivo knee joint movement and contact forces are interlinked - and thereby impact biomechanical interpretation of any new knee replacement design. In this collaborative study, we have created unique kinematic and kinetic datasets of the lower limb musculoskeletal system for worldwide dissemination by assessing a unique cohort of 6 subjects with instrumented knee implants (Charité - Universitätsmedizin Berlin) synchronized with a moving fluoros...
Sportverletzung Sportschaden : Organ der Gesellschaft für Orthopädisch-Traumatologische Sportmedizin, 1994
Results from an in vivo assessment of the bending stiffness of human tibiae with a new method dem... more Results from an in vivo assessment of the bending stiffness of human tibiae with a new method demonstrate that bone mineral measurements are not a suitable predictor to evaluate changes of mechanical properties of long bones. In a study on 559 male military recruits, the bone mineral at tibial shaft resulted in a mean increase of +1.8% during 15 weeks of exercise. The bending stiffness however increased about 25%. An additional test 24 months later on a sample indicated that the increase of bone mineral content was only due to the natural maturation of bone. The bending stiffness however, decreased by about 6% demonstrating the earlier training effect. No correlation between bone mineral and bending stiffness could be found neither in absolute values nor in difference between the three measurements. At the same time first results of a normative study on children (9 to 18 years old, male and female) and on women (up to 80 years old) are presented.
X-Ray video fluoroscopy is nowadays a common technique to retrieve in vivo 3D kinematic data of t... more X-Ray video fluoroscopy is nowadays a common technique to retrieve in vivo 3D kinematic data of the knee joint during human motion activities. Unfortunately, since a fluoroscopic imaging system is designed to be stati onary during measurement, the knee joint moves out of field of view of the fluoroscope during level walking. Therefore, it beco mes unfeasible to retrieve scientifically
Axial-transmission acoustics have shown to be a promising technique to measure individual bone pr... more Axial-transmission acoustics have shown to be a promising technique to measure individual bone properties and detect bone pathologies. With the ultimate goal being the in-vivo application of such systems, quantification of the key aspects governing the reliability is crucial to bring this method towards clinical use. This work presents a systematic reliability study quantifying the sources of variability and their magnitudes of in-vivo measurements using axial-transmission acoustics. 42 healthy subjects were measured by an experienced operator twice per week, over a four-month period, resulting in over 150000 wave measurements. In a complementary study to assess the influence of different operators performing the measurements, 10 novice operators were trained, and each measured 5 subjects on a single occasion, using the same measurement protocol as in the first part of the study. The estimated standard error for the measurement protocol used to collect the study data was ∼ 17 m/s (∼...
1, 2 Daniel Baumgartner, 3 Georg Osterhoff, 3 Clément M.L.Werner, 4 Hans Gerber and 1 Philippe Fa... more 1, 2 Daniel Baumgartner, 3 Georg Osterhoff, 3 Clément M.L.Werner, 4 Hans Gerber and 1 Philippe Favre 1 Laboratory for Orthopaedic Research, Department of Orthopaedics, Balgrist, University of Zurich, Switzerland 2 Zurich University of Applied Sciences, Institute for Mechanical Systems, Winterthur, Switzerland, email: [email protected] Division of Trauma Surgery, University Hospital Zurich, Switzerland 4 Institute for Biomechanics, ETH Zürich, Switzerland
Background: Surgery for disc herniations can be complicated by two major problems: painful degene... more Background: Surgery for disc herniations can be complicated by two major problems: painful degeneration of the spinal segment and re-herniation. Therefore, we examined an absorbable polyglycolic acid (PGA) biomaterial, which was lyophilized with hyaluronic acid (HA), for its utility to (a) re-establish spinal stability and to (b) seal annulus fibrosus defects. The biomechanical properties range of motion (ROM), neutral zone (NZ) and a potential annulus sealing capacity were investigated. Methods: Seven bovine, lumbar spinal units were tested in vitro for ROM and NZ in three consecutive stages: (a) intact, (b) following nucleotomy and (c) after insertion of a PGA/HA nucleus-implant. For biomechanical testing, spinal units were mounted on a loading-simulator for spines. In three cycles, axial loading was applied in an excentric mode with 0.5 Nm steps until an applied moment of ± 7.5 Nm was achieved in flexion/extension. ROM and NZ were assessed. These tests were performed without and with annulus sealing by sewing a PGA/HA annulus-implant into the annulus defect. Results: Spinal stability was significantly impaired after nucleotomy (p < 0.001). Intradiscal implantation of a PGA-HA nucleus-implant, however, restored spinal stability (p < 0.003). There was no statistical difference between the stability provided by the nucleus-implant and the intact stage regarding flexion/extension movements (p = 0.209). During the testing sequences, herniation of biomaterial through the annulus defect into the spinal canal regularly occurred, resulting in compression of neural elements. Sewing a PGA/HA annulus-implant into the annulus defect, however, effectively prevented herniation. Conclusion: PGA/HA biomaterial seems to be well suited for cell-free and cell-based regenerative treatment strategies in spinal surgery. Its abilities to restore spinal stability and potentially close annulus defects open up new vistas for regenerative approaches to treat intervertebral disc degeneration and for preventing implant herniation.
The aim of this study was to determine the mean distances of facial movements in 24 healthy indiv... more The aim of this study was to determine the mean distances of facial movements in 24 healthy individuals aged between 22 and 70 years, using the digitised three-dimensional video-analysis system developed by Frey et al. The subjects were divided into three groups of eight. The first group consisted of individuals aged between 20 and 30 years (mean^s.d. ¼ 25.0^2.33 years). Subjects in the second group were aged between 40 and 50 years (mean^s.d. ¼ 46.8^2.53 years), and the third group consisted of subjects aged between 60 and 70 years (meanŝ .d. ¼ 63.6^3.07 years). In all groups the sexes were equally represented. No subject had had treatment to the face, nor did they have paralysis, scars or diseases of the skin. Males showed larger movements of the face than females, on average by 1.40^0.73 mm (15.08%). Subjects aged between 60 and 70 years demonstrated the largest movements of the face. The evaluation of facial movements in 24 healthy volunteers showed that sex and age affect facial dynamics. Thus study generated three-dimensional standard values for healthy facial movements.
Background: During rapid movements of the arm the transversus abdominis muscle (TA) is typically ... more Background: During rapid movements of the arm the transversus abdominis muscle (TA) is typically activated before the prime mover (deltoid), to stabilise the spine before the impending postural disturbance. This feedforward activity is compromised in patients with low back pain (LBP), although the phenomenon has not been investigated widely, because of the invasiveness of the assessment technique [fine-wire intramuscular electromyography (iEMG)]; we examined whether ultrasound tissue Doppler imaging (TDI) could represent a non-invasive alternative. Methods: 14 subjects (8M, 6F;23.0±2.0 yrs) performed 10 repetitions each of rapid shoulder flexion, extension and abduction, whilst surface EMG recordings from medial deltoid, and iEMG and M-mode TDI tissuevelocity recordings from the contralateral TA, internal (IO) and external (EO) oblique muscles were made. Muscle onsets were determined by visual inspection of blinded EMG and TDI signals using custom-built software (MATLAB) and expressed relative to the deltoid onset (values −150ms to + 50ms = feed-forward). Results: The TDI-determined onsets were later than those of iEMG by 32.5 (SD 32.8) ms for TA, 17.9 (SD 23.3) ms for IO, and 15.8 (SD 25.3) ms for EO. The methods showed moderately high, significant correlations: r = 0.55 (TA); r = 0.61 (IO); r = 0.56 (EO) (each p< 0.0002). Conclusion: The mean differences between the methods were likely due to electromechanical delay. The SDs of the differences were comparable to those for repeated measurements with either technique. TDI appears to be a valid means of assessing abdominal muscle feed-forward activity, and should allow this phenomenon to be investigated in larger numbers of LBP patients. Support: NFP53–405340–104787/1.
Although total knee arthroplasty (TKA) has become a standard surgical procedure for relieving pai... more Although total knee arthroplasty (TKA) has become a standard surgical procedure for relieving pain, knowledge of the in vivo knee joint kinematics throughout common functional activities of daily living is still missing. The goal of this study was to analyse knee joint motion throughout complete cycles of daily activities in TKA subjects to establish whether a significant difference in joint kinematics occurs between different activities. Using dynamic videofluoroscopy, we assessed tibio-femoral kinematics in six subjects throughout complete cycles of walking, stair descent, sit-to-stand and stand-to-sit. The mean range of condylar anterior-posterior translation exhibited clear task dependency across all subjects. A significantly larger anterior-posterior translation was observed during stair descent compared to level walking and stand-to-sit. Local minima were observed at approximately 308 flexion for different tasks, which were more prominent during loaded task phases. This characteristic is likely to correspond to the specific design of the implant. From the data presented in this study, it is clear that the flexion angle alone cannot fully explain tibio-femoral implant kinematics. As a result, it seems that the assessment of complete cycles of the most frequent functional activities is imperative when evaluating the behaviour of a TKA design in vivo.
Videofluoroscopy has been shown to provide essential information in the evaluation of the functio... more Videofluoroscopy has been shown to provide essential information in the evaluation of the functionality of total knee arthroplasties. However, due to the limitation in the field of view, most systems can only assess knee kinematics during highly restricted movements. To avoid the limitations of a static image intensifier, a moving fluoroscope has been presented as a standalone system that allows tracking of the knee during multiple complete cycles of level- and downhill-walking, as well as stair descent, in combination with the synchronous assessment of ground reaction forces and whole body skin marker measurements. Here, we assess the ability of the system to keep the knee in the field of view of the image intensifier. By measuring ten total knee arthroplasty subjects, we demonstrate that it is possible to maintain the knee to within 1.8 ± 1.4 cm vertically and 4.0 ± 2.6 cm horizontally of the centre of the intensifier throughout full cycles of activities of daily living. Since con...
Combined knowledge of the functional kinematics and kinetics of the human body is critical for un... more Combined knowledge of the functional kinematics and kinetics of the human body is critical for understanding a wide range of biomechanical processes including musculoskeletal adaptation, injury mechanics, and orthopaedic treatment outcome, but also for validation of musculoskeletal models. Until now, however, no datasets that include internal loading conditions (kinetics), synchronized with advanced kinematic analyses in multiple subjects have been available. Our goal was to provide such datasets and thereby foster a new understanding of how in vivo knee joint movement and contact forces are interlinked - and thereby impact biomechanical interpretation of any new knee replacement design. In this collaborative study, we have created unique kinematic and kinetic datasets of the lower limb musculoskeletal system for worldwide dissemination by assessing a unique cohort of 6 subjects with instrumented knee implants (Charité - Universitätsmedizin Berlin) synchronized with a moving fluoros...
Sportverletzung Sportschaden : Organ der Gesellschaft für Orthopädisch-Traumatologische Sportmedizin, 1994
Results from an in vivo assessment of the bending stiffness of human tibiae with a new method dem... more Results from an in vivo assessment of the bending stiffness of human tibiae with a new method demonstrate that bone mineral measurements are not a suitable predictor to evaluate changes of mechanical properties of long bones. In a study on 559 male military recruits, the bone mineral at tibial shaft resulted in a mean increase of +1.8% during 15 weeks of exercise. The bending stiffness however increased about 25%. An additional test 24 months later on a sample indicated that the increase of bone mineral content was only due to the natural maturation of bone. The bending stiffness however, decreased by about 6% demonstrating the earlier training effect. No correlation between bone mineral and bending stiffness could be found neither in absolute values nor in difference between the three measurements. At the same time first results of a normative study on children (9 to 18 years old, male and female) and on women (up to 80 years old) are presented.
X-Ray video fluoroscopy is nowadays a common technique to retrieve in vivo 3D kinematic data of t... more X-Ray video fluoroscopy is nowadays a common technique to retrieve in vivo 3D kinematic data of the knee joint during human motion activities. Unfortunately, since a fluoroscopic imaging system is designed to be stati onary during measurement, the knee joint moves out of field of view of the fluoroscope during level walking. Therefore, it beco mes unfeasible to retrieve scientifically
Uploads
Papers by Hans Gerber