Itzhak Siev-ner - Academia.edu (original) (raw)
Papers by Itzhak Siev-ner
Studies in Mechanobiology, Tissue Engineering and Biomaterials, 2009
... springerlink.com © Springer-Verlag Berlin Heidelberg 2009 ... 35, 11751187 (2007) Portnoy, S... more ... springerlink.com © Springer-Verlag Berlin Heidelberg 2009 ... 35, 11751187 (2007) Portnoy, S., Yizhar, Z., Shabshin, N., Itzchak, Y., Kristal, A., Dotan-Marom, Y., Siev-Ner, I., Gefen, A.: Internal mechanical conditions in the soft tissues of a residual limb of a transtibial amputee. ...
Annals of Biomedical Engineering
Fitting of a prosthetic socket is a critical stage in the process of rehabilitation of a trans-ti... more Fitting of a prosthetic socket is a critical stage in the process of rehabilitation of a trans-tibial amputation (TTA) patient, since a misfit may cause pressure ulcers or a deep tissue injury (DTI: necrosis of the muscle flap under intact skin) in the residual limb. To date, prosthetic fitting typically depends on the subjective skills of the prosthetist, and is not supported by biomedical instrumentation that allows evaluation of the quality of fitting. Specifically, no technology is presently available to provide real-time continuous information on the internal distribution of mechanical stresses in the residual limb during fitting of the prosthesis, or while using it and this severely limits patient evaluations. In this study, a simplified yet clinically oriented patient-specific finite element (FE) model of the residual limb was developed for real-time stress analysis. For this purpose we employed a custom-made FE code that continuously calculates internal stresses in the resid...
Journal of Biomechanics
Active transtibial amputation (TTA) patients are at risk for developing pressure ulcers (PU) and ... more Active transtibial amputation (TTA) patients are at risk for developing pressure ulcers (PU) and deep tissue injury (DTI) while using their prosthesis. It is therefore important to obtain knowledge of the mechanical state in the internal soft tissues of the residuum, as well as knowledge of the mechanical state upon its surface. Our aim was to apply patient-specific MRI-based non-linear finite element (FE) models to quantify internal strains in TTA prosthetic users (n=5) during load-bearing. By further employing a strain injury threshold for skeletal muscle, we identified patients susceptible to DTI. The geometrical characteristics of the residuum of the TTA participants varied substantially between patients, e.g. the residuum lengths were 7.6, 8.1, 9.2, 11.5 and 13.3cm. We generally found that internal strains were higher in the bone proximity than in the muscle flap periphery. The highest strains, which in some patients exceeded 50% (engineering strain) for compressive, tensile an...
Transtibial amputation (TTA) patients face ongoing morphological changes in their residual limb. ... more Transtibial amputation (TTA) patients face ongoing morphological changes in their residual limb. The residuum volume changes due to weight gain or loss, diurnal edema, and muscle atrophy. Consequently, the TTA prosthetic-user is fitted with a new prosthetic socket approximately every four years. Despite new innovations in socket and liner materials and design, contemporary prosthetics are not yet equipped to confront these changes. The TTA residual limb is therefore subjected to high superficial and internal stresses which may cause injury. Appending the hazardous condition of natural volume change of the residuum is the initial geometrical state of the truncated bones. The primary surgical considerations in TTA are the tibial length, the bevelment of the distal end of the tibia and the location of the surgical scar. These risk factors may significantly affect the well being of the TTA residuum. Previous studies assumed that the criteria for a well-fitted socket were low interface s...
Individuals with a spinal cord injury (SCI) are susceptible to deep tissue injury (DTI) which is ... more Individuals with a spinal cord injury (SCI) are susceptible to deep tissue injury (DTI) which is a pressure-related-necrosis that onsets in the gluteus muscles under the ischial tuberosities (IT). The condition may exacerbate to widespread tissue necrosis and sepsis [1], but early detection is currently not feasible because the injury starts and progresses under intact skin. In SCI patients, local elevated mechanical strains and stresses are formed around the IT, and are not relieved through motion [2]. The excessive tissue strains and stresses, combined with ischemia and hindered diffusion, induce and promote muscle cell death [3]. Recently, we developed a real-time, patient-specific finite element (FE) modeling method and experimental system with a clinical orientation of providing early detection of sub-dermal mechanical conditions that potentially lead to DTI. We presented this system and initial data from healthy adults during the 2006 Summer Bioengineering Conference [4]. Here...
Annals of Biomedical Engineering
The residual limb of transtibial amputation (TTA) prosthetic users is threatened daily by pressur... more The residual limb of transtibial amputation (TTA) prosthetic users is threatened daily by pressure ulcers (PU) and deep tissue injury (DTI) caused mainly by sustained mechanical strains and stresses. Several risk factors dominate the extent of internal tissue loads in the residuum. In this study, we developed a set of three-dimensional finite element (FE) models that were variants of a patient-specific FE model, built from magnetic resonance imaging scans. The set of FE modes was utilized to assess the impact of the following risk factors on the strain/stress distribution in the muscle flap: (i) the tibial length, (ii) the tibial bevelment, (iii) a fibular osteophyte, (iv) the mechanical properties of the muscle, and (v) scarring in different locations and depths. A total of 12 nonlinear FE model configurations, representing variations in these factors, were built and solved. We present herein calculations of compression, tension and shear strains and stresses, von Mises stresses, a...
IFMBE Proceedings, 2009
... J Wound Care 16:336-342. 2. Portnoy S, Yizhar Z, Shabshin N, Itzchak Y, Kristal A, Dotan-Maro... more ... J Wound Care 16:336-342. 2. Portnoy S, Yizhar Z, Shabshin N, Itzchak Y, Kristal A, Dotan-Marom Y, Siev-Ner I, Gefen A (2008) Internal mechanical conditions in the soft tissues of a residual limb of a trans-tibial amputee. J Biomech 41:1897-1909. ...
Brain research, Jan 19, 2015
Does the learning of a balance and stability skill exhibit time-course phases and transfer limita... more Does the learning of a balance and stability skill exhibit time-course phases and transfer limitations characteristic of the acquisition and consolidation of voluntary movement sequences? Here we followed the performance of young adults trained in maintaining balance while standing on a moving platform synchronized with a virtual reality road travel scene. The training protocol included 8.3-min long iterations of the road scene. Center of Pressure (CoP) displacements were analyzed for each task iteration within the training session, as well as during tests at 24h, 4 weeks and 12 weeks post-training to test for consolidation phase ("offline") gains and assess retention. In addition, CoP displacements in reaction to external perturbations were assessed before and after the training session and in the 3 subsequent post-training assessments (stability tests). There were significant reductions in CoP displacements as experience accumulated within session, with performance stabi...
International journal of sports medicine, 2012
The aim of the present study was to determine the association between joint range of motion (ROM)... more The aim of the present study was to determine the association between joint range of motion (ROM) and patellofemoral pain syndrome (PFPS) in young female dancers. The study population included 1 359 female dancers, aged 8-20 years. All dancers were clinically examined for current PFPS, and their joint ROM was measured at the lumbar spine and the lower extremities. 321 of the 1 359 dancers (23.6%) experienced PFPS. Prevalence of the syndrome increased with the dancer's age (p<0.001). Dancers with hypo ROM in hip external rotation, ankle plantar-flexion, ankle/foot pointe, hip abduction, hip extension, and limited hamstrings and lumbar spine were significantly less prone to developing PFPS compared to dancers with average ROM: 19.2% vs. 26.2% (p=0.014); 13.7% vs. 26.1% (p<0.001); 12.2% vs. 26.2% (p<0.001); 10.0% vs. 25.3% (p<0.001); 12.6% vs. 24.2% (p<0.001); and 9.3% vs. 28.2% (p<0.001), respectively. The group with the smallest prevalence of PFPS (10.2%) manife...
2009 Virtual Rehabilitation International Conference, 2009
The purpose of this poster is to present the development of functional and non-functional virtual... more The purpose of this poster is to present the development of functional and non-functional virtual environments for the investigation of dual tasking capabilities after traumatic brain injury.
The Foot, 2009
Considerable disagreement exists whether trans-metatarsal amputations are indicated in persons wi... more Considerable disagreement exists whether trans-metatarsal amputations are indicated in persons with diabetes. A previous study reported that statistically the success rate of Syme&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s amputation in diabetic patients over 65 years of age resulted in a very poor results. The purpose of this study was to investigate the results of trans-metatarsal amputations, in patients with diabetes and to seek markers which could shed light upon the advantages/disadvantages of this procedure. The records of 46 patients covering a 10-year period (1996-2006) were used as a database. Twelve needed higher amputation level and another 10 needed a wound revision. All the patients that maintained the original amputation level walk without a need for a prosthesis and kept their previous abode. TMA in diabetic patients, although at a high risk for an extrasurgical procedure, once successful, the patient will regain his previous lifestyle.
The Foot, 1999
A 51-year-old male required the construction of enormous custom-made shoes due to extreme lymphoe... more A 51-year-old male required the construction of enormous custom-made shoes due to extreme lymphoedema. The lymphoedema developed as a late sequel of erysipelas. Aggressive conservative management of erysipelas and, if necessary, Charles operation should be considered in order to avoid the potentially catastrophic complications of this usually benign streptococcal infection.
The Foot, 1997
The study comprised of 10 patients (nine ballet-dancers and one athelete) who underwent excision ... more The study comprised of 10 patients (nine ballet-dancers and one athelete) who underwent excision of the OS trigonum, due to pain on full plantar-flexion. In each case, at surgery the retrotalar fat appeared to be under pressure and bulged through the incision site. Histological examination revealed extensive fibrosis of this fat. It is postulated, therefore, that impingement had occurred between the posterior lip of the tibia and the plantar flexed calcaneum. A subsequent ballet-dancer (not included in the nine), who experienced retrotibial pain, had no OS trigonum and whose bone scan was positive, underwent simple adipose tissue excision, with equally good results. A similarity is noted with Hoffa's syndrome and the question has arisen as to whether it is necessary to excise the OS trigonum or whether removal of the fat pad alone will suffice. 97
PM&R, 2010
The use of therapeutic modalities such as nitrous oxide; platelet-rich plasma therapy; stem cell ... more The use of therapeutic modalities such as nitrous oxide; platelet-rich plasma therapy; stem cell transplantation; and low-intensity, low-frequency ultrasound (LILFU) to enhance tendon regenerative capacity in patients with tendinous insufficiency is in its early stages. Of those alternatives, only LILFU studies have provided level 1 evidence of efficacy in bone healing . In vitro, low-intensity ultrasound, which exerts direct nonthermal effects on cell physiology, stimulates the expression of numerous genes involved in the healing process, including aggrecan, insulin-like growth factor, transforming growth factor, collagen, nitric oxide synthase, cytokines, and angiogenesis .
Medical Engineering & Physics, 2010
Transtibial amputation (TTA) prosthetic-users may risk the integrity of their residuum while tryi... more Transtibial amputation (TTA) prosthetic-users may risk the integrity of their residuum while trying to maintain everyday activities. Compression of the muscle flap between the truncated bones and the prosthetic socket may cause pressure ulcers and deep tissue injury (DTI). We hypothesize that mechanical stresses in the muscle flap are higher when walking over complex terrains than during plane gait, and so, the residuum could be at risk for DTI when walking over these terrains. Accordingly, we evaluated internal soft tissue stresses in the residuum at the vicinity of the tibia in 18 prosthetic-users (7 vascular, 11 traumatic). For this purpose, we developed a portable monitor that calculated subject-specific internal stresses in the residuum in real-time. Each subject was studied while walking on plane floor, grass, stairs and slope. We found that internal stresses were the highest while subjects descended a slope, during which internal peak and root mean square (RMS) stresses were approximately 40% and 50% greater than in plane gait, respectively. Peak and RMS stresses calculated while descending a slope were approximately 2 times higher for the sub-group of vascular subjects compared to traumatic, but were similar between the two sub-groups for other ambulation tasks. Overall, the present internal stress monitor is a practical tool for real-time evaluation of internal stresses in the residuum of TTA prosthetic-users in the clinical setting or outdoors. Pending integration of appropriate dynamic tissue injury thresholds, the device can be utilized for alerting to the danger of DTI.
Journal of Sports Sciences, 2012
Studies in Mechanobiology, Tissue Engineering and Biomaterials, 2009
... springerlink.com © Springer-Verlag Berlin Heidelberg 2009 ... 35, 11751187 (2007) Portnoy, S... more ... springerlink.com © Springer-Verlag Berlin Heidelberg 2009 ... 35, 11751187 (2007) Portnoy, S., Yizhar, Z., Shabshin, N., Itzchak, Y., Kristal, A., Dotan-Marom, Y., Siev-Ner, I., Gefen, A.: Internal mechanical conditions in the soft tissues of a residual limb of a transtibial amputee. ...
Annals of Biomedical Engineering
Fitting of a prosthetic socket is a critical stage in the process of rehabilitation of a trans-ti... more Fitting of a prosthetic socket is a critical stage in the process of rehabilitation of a trans-tibial amputation (TTA) patient, since a misfit may cause pressure ulcers or a deep tissue injury (DTI: necrosis of the muscle flap under intact skin) in the residual limb. To date, prosthetic fitting typically depends on the subjective skills of the prosthetist, and is not supported by biomedical instrumentation that allows evaluation of the quality of fitting. Specifically, no technology is presently available to provide real-time continuous information on the internal distribution of mechanical stresses in the residual limb during fitting of the prosthesis, or while using it and this severely limits patient evaluations. In this study, a simplified yet clinically oriented patient-specific finite element (FE) model of the residual limb was developed for real-time stress analysis. For this purpose we employed a custom-made FE code that continuously calculates internal stresses in the resid...
Journal of Biomechanics
Active transtibial amputation (TTA) patients are at risk for developing pressure ulcers (PU) and ... more Active transtibial amputation (TTA) patients are at risk for developing pressure ulcers (PU) and deep tissue injury (DTI) while using their prosthesis. It is therefore important to obtain knowledge of the mechanical state in the internal soft tissues of the residuum, as well as knowledge of the mechanical state upon its surface. Our aim was to apply patient-specific MRI-based non-linear finite element (FE) models to quantify internal strains in TTA prosthetic users (n=5) during load-bearing. By further employing a strain injury threshold for skeletal muscle, we identified patients susceptible to DTI. The geometrical characteristics of the residuum of the TTA participants varied substantially between patients, e.g. the residuum lengths were 7.6, 8.1, 9.2, 11.5 and 13.3cm. We generally found that internal strains were higher in the bone proximity than in the muscle flap periphery. The highest strains, which in some patients exceeded 50% (engineering strain) for compressive, tensile an...
Transtibial amputation (TTA) patients face ongoing morphological changes in their residual limb. ... more Transtibial amputation (TTA) patients face ongoing morphological changes in their residual limb. The residuum volume changes due to weight gain or loss, diurnal edema, and muscle atrophy. Consequently, the TTA prosthetic-user is fitted with a new prosthetic socket approximately every four years. Despite new innovations in socket and liner materials and design, contemporary prosthetics are not yet equipped to confront these changes. The TTA residual limb is therefore subjected to high superficial and internal stresses which may cause injury. Appending the hazardous condition of natural volume change of the residuum is the initial geometrical state of the truncated bones. The primary surgical considerations in TTA are the tibial length, the bevelment of the distal end of the tibia and the location of the surgical scar. These risk factors may significantly affect the well being of the TTA residuum. Previous studies assumed that the criteria for a well-fitted socket were low interface s...
Individuals with a spinal cord injury (SCI) are susceptible to deep tissue injury (DTI) which is ... more Individuals with a spinal cord injury (SCI) are susceptible to deep tissue injury (DTI) which is a pressure-related-necrosis that onsets in the gluteus muscles under the ischial tuberosities (IT). The condition may exacerbate to widespread tissue necrosis and sepsis [1], but early detection is currently not feasible because the injury starts and progresses under intact skin. In SCI patients, local elevated mechanical strains and stresses are formed around the IT, and are not relieved through motion [2]. The excessive tissue strains and stresses, combined with ischemia and hindered diffusion, induce and promote muscle cell death [3]. Recently, we developed a real-time, patient-specific finite element (FE) modeling method and experimental system with a clinical orientation of providing early detection of sub-dermal mechanical conditions that potentially lead to DTI. We presented this system and initial data from healthy adults during the 2006 Summer Bioengineering Conference [4]. Here...
Annals of Biomedical Engineering
The residual limb of transtibial amputation (TTA) prosthetic users is threatened daily by pressur... more The residual limb of transtibial amputation (TTA) prosthetic users is threatened daily by pressure ulcers (PU) and deep tissue injury (DTI) caused mainly by sustained mechanical strains and stresses. Several risk factors dominate the extent of internal tissue loads in the residuum. In this study, we developed a set of three-dimensional finite element (FE) models that were variants of a patient-specific FE model, built from magnetic resonance imaging scans. The set of FE modes was utilized to assess the impact of the following risk factors on the strain/stress distribution in the muscle flap: (i) the tibial length, (ii) the tibial bevelment, (iii) a fibular osteophyte, (iv) the mechanical properties of the muscle, and (v) scarring in different locations and depths. A total of 12 nonlinear FE model configurations, representing variations in these factors, were built and solved. We present herein calculations of compression, tension and shear strains and stresses, von Mises stresses, a...
IFMBE Proceedings, 2009
... J Wound Care 16:336-342. 2. Portnoy S, Yizhar Z, Shabshin N, Itzchak Y, Kristal A, Dotan-Maro... more ... J Wound Care 16:336-342. 2. Portnoy S, Yizhar Z, Shabshin N, Itzchak Y, Kristal A, Dotan-Marom Y, Siev-Ner I, Gefen A (2008) Internal mechanical conditions in the soft tissues of a residual limb of a trans-tibial amputee. J Biomech 41:1897-1909. ...
Brain research, Jan 19, 2015
Does the learning of a balance and stability skill exhibit time-course phases and transfer limita... more Does the learning of a balance and stability skill exhibit time-course phases and transfer limitations characteristic of the acquisition and consolidation of voluntary movement sequences? Here we followed the performance of young adults trained in maintaining balance while standing on a moving platform synchronized with a virtual reality road travel scene. The training protocol included 8.3-min long iterations of the road scene. Center of Pressure (CoP) displacements were analyzed for each task iteration within the training session, as well as during tests at 24h, 4 weeks and 12 weeks post-training to test for consolidation phase ("offline") gains and assess retention. In addition, CoP displacements in reaction to external perturbations were assessed before and after the training session and in the 3 subsequent post-training assessments (stability tests). There were significant reductions in CoP displacements as experience accumulated within session, with performance stabi...
International journal of sports medicine, 2012
The aim of the present study was to determine the association between joint range of motion (ROM)... more The aim of the present study was to determine the association between joint range of motion (ROM) and patellofemoral pain syndrome (PFPS) in young female dancers. The study population included 1 359 female dancers, aged 8-20 years. All dancers were clinically examined for current PFPS, and their joint ROM was measured at the lumbar spine and the lower extremities. 321 of the 1 359 dancers (23.6%) experienced PFPS. Prevalence of the syndrome increased with the dancer's age (p<0.001). Dancers with hypo ROM in hip external rotation, ankle plantar-flexion, ankle/foot pointe, hip abduction, hip extension, and limited hamstrings and lumbar spine were significantly less prone to developing PFPS compared to dancers with average ROM: 19.2% vs. 26.2% (p=0.014); 13.7% vs. 26.1% (p<0.001); 12.2% vs. 26.2% (p<0.001); 10.0% vs. 25.3% (p<0.001); 12.6% vs. 24.2% (p<0.001); and 9.3% vs. 28.2% (p<0.001), respectively. The group with the smallest prevalence of PFPS (10.2%) manife...
2009 Virtual Rehabilitation International Conference, 2009
The purpose of this poster is to present the development of functional and non-functional virtual... more The purpose of this poster is to present the development of functional and non-functional virtual environments for the investigation of dual tasking capabilities after traumatic brain injury.
The Foot, 2009
Considerable disagreement exists whether trans-metatarsal amputations are indicated in persons wi... more Considerable disagreement exists whether trans-metatarsal amputations are indicated in persons with diabetes. A previous study reported that statistically the success rate of Syme&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s amputation in diabetic patients over 65 years of age resulted in a very poor results. The purpose of this study was to investigate the results of trans-metatarsal amputations, in patients with diabetes and to seek markers which could shed light upon the advantages/disadvantages of this procedure. The records of 46 patients covering a 10-year period (1996-2006) were used as a database. Twelve needed higher amputation level and another 10 needed a wound revision. All the patients that maintained the original amputation level walk without a need for a prosthesis and kept their previous abode. TMA in diabetic patients, although at a high risk for an extrasurgical procedure, once successful, the patient will regain his previous lifestyle.
The Foot, 1999
A 51-year-old male required the construction of enormous custom-made shoes due to extreme lymphoe... more A 51-year-old male required the construction of enormous custom-made shoes due to extreme lymphoedema. The lymphoedema developed as a late sequel of erysipelas. Aggressive conservative management of erysipelas and, if necessary, Charles operation should be considered in order to avoid the potentially catastrophic complications of this usually benign streptococcal infection.
The Foot, 1997
The study comprised of 10 patients (nine ballet-dancers and one athelete) who underwent excision ... more The study comprised of 10 patients (nine ballet-dancers and one athelete) who underwent excision of the OS trigonum, due to pain on full plantar-flexion. In each case, at surgery the retrotalar fat appeared to be under pressure and bulged through the incision site. Histological examination revealed extensive fibrosis of this fat. It is postulated, therefore, that impingement had occurred between the posterior lip of the tibia and the plantar flexed calcaneum. A subsequent ballet-dancer (not included in the nine), who experienced retrotibial pain, had no OS trigonum and whose bone scan was positive, underwent simple adipose tissue excision, with equally good results. A similarity is noted with Hoffa's syndrome and the question has arisen as to whether it is necessary to excise the OS trigonum or whether removal of the fat pad alone will suffice. 97
PM&R, 2010
The use of therapeutic modalities such as nitrous oxide; platelet-rich plasma therapy; stem cell ... more The use of therapeutic modalities such as nitrous oxide; platelet-rich plasma therapy; stem cell transplantation; and low-intensity, low-frequency ultrasound (LILFU) to enhance tendon regenerative capacity in patients with tendinous insufficiency is in its early stages. Of those alternatives, only LILFU studies have provided level 1 evidence of efficacy in bone healing . In vitro, low-intensity ultrasound, which exerts direct nonthermal effects on cell physiology, stimulates the expression of numerous genes involved in the healing process, including aggrecan, insulin-like growth factor, transforming growth factor, collagen, nitric oxide synthase, cytokines, and angiogenesis .
Medical Engineering & Physics, 2010
Transtibial amputation (TTA) prosthetic-users may risk the integrity of their residuum while tryi... more Transtibial amputation (TTA) prosthetic-users may risk the integrity of their residuum while trying to maintain everyday activities. Compression of the muscle flap between the truncated bones and the prosthetic socket may cause pressure ulcers and deep tissue injury (DTI). We hypothesize that mechanical stresses in the muscle flap are higher when walking over complex terrains than during plane gait, and so, the residuum could be at risk for DTI when walking over these terrains. Accordingly, we evaluated internal soft tissue stresses in the residuum at the vicinity of the tibia in 18 prosthetic-users (7 vascular, 11 traumatic). For this purpose, we developed a portable monitor that calculated subject-specific internal stresses in the residuum in real-time. Each subject was studied while walking on plane floor, grass, stairs and slope. We found that internal stresses were the highest while subjects descended a slope, during which internal peak and root mean square (RMS) stresses were approximately 40% and 50% greater than in plane gait, respectively. Peak and RMS stresses calculated while descending a slope were approximately 2 times higher for the sub-group of vascular subjects compared to traumatic, but were similar between the two sub-groups for other ambulation tasks. Overall, the present internal stress monitor is a practical tool for real-time evaluation of internal stresses in the residuum of TTA prosthetic-users in the clinical setting or outdoors. Pending integration of appropriate dynamic tissue injury thresholds, the device can be utilized for alerting to the danger of DTI.
Journal of Sports Sciences, 2012