Ischial tuberosity: new donor site for bone grafts in animal cleft research.

In the context of cleft repair in animal research in rat models, different areas can be used for bone grafting. The aim of the present study was to present the tuberosity of the ischium as a new donor site and to evaluate its quality in relation to an artificial alveolar cleft. Four weeks after creating experimental alveolar clefts in seven Wistar rats, the repair was performed in the now twelve-week-old male animals using bone blocks grafted from the ischial tuberosity. Two days before surgery and two as well as twenty-eight days after surgery, microCT scans were performed, and the grafted bone blocks were analyzed regarding height, width, thickness, and volume. Additionally, bone mineral density (BMD) and bone volume fraction (BV/TV) were measured in the repaired cleft. The mean bone volume of the graft was about 19.77 ± 7.77mm3. Immediately after jaw reconstruction the BMD and BV/TV were about 0.54 ± 0.05 g/cm3 and 54.9 ± 5.07% for the transplant and about 1.13 ± 0.08 g/cm3 and 94.5 ± 3.70%, respectively, for the surrounding bone. Four weeks later the BMD and BV/TV were about 0.57 ± 0.13 g/cm3 and 56.60 ± 13.70% for the transplant and about 11.17 ± 0.07 g/cm3 and 97.50 ± 2.15%, respectively, for the surrounding bone. A hip fracture was found in four of the animals after surgery. The ischial tuberosity offers large bone blocks, which are sufficient for cleft repair in the rat model. However, the bone quality regarding BMD and BV/TV is less compared with the surrounding bone of the alveolar cleft, even after a period of 4 weeks, despite recognizable renovation processes.

Wheelchair Tilt-in-Space and Recline Functions: Influence on Sitting Interface Pressure and Ischial Blood Flow in an Elderly Population.

Pressure ulcers (PUs) result from localised injury to the skin and underlying tissue and usually occur over a bony prominence as a result of pressure, often in combination with shear forces. Both pressure magnitude and duration are thought to be key risk factors in the occurrence of PUs, thus exposing wheelchair-bound subjects to high risk of PU development. As a result, wheelchairs that incorporate tilt-in-space and recline functions are routinely prescribed to redistribute pressure away from their ischial tuberosities. The goal of this study was to analyse the role of full-body tilt and recline angles in governing sitting interface pressure and blood circulation parameters in elderly subjects and thereby investigate the efficacy of tilt-in-space wheelchairs for aiding pressure relief activity. Sitting interface pressure and ischial blood flow parameters were examined in 20 healthy elderly subjects while seated in a tilt-in-space and recline wheelchair. Five different angles of seat tilt (5°, 15°, 25°, 35°, and 45°) were assessed in combination with three different angles of backrest recline (5°, 15°, and 30°). The results of the study show that when compared to the upright reference posture, every position (except 15°T/5°R) resulted in a significant decrease in sitting interface pressure. Ischial blood flow also showed significant increases at four different positions (45°T/15°R, 15°T/30°R, 35°T/30°R, and 45°T/30°R) but only at larger tilt-in-space and recline angles. The results therefore suggest that small tilt-in-space and recline angles are indeed able to reduce sitting interface pressures, whereas changes in ischial blood flow only occur at larger angles. In the literature, cell deformation is thought to be dominant over tissue ischemia in the development of tissue necrosis and PUs. Therefore, together with our findings it can be concluded that frequently undertaking small adjustments in tilt-in-space and recline angle might be important for preventing cell deformation and any associated cell necrosis. Larger angles of tilt-in-space and recline seem to support blood flow returning to the tissues, which is likely to play a positive role in healing damaged tissue.

Repair of Sacral and Ischial Region Defects With Lateral Sacral Artery Perforator Flaps.

BACKGROUND: Reconstructive choices for the defects of the sacral and ischial regions include various steps of the reconstructive ladder from primary closure to free flaps. This study aimed to present repair of sacral and ischial region defects with lateral sacral artery perforator (LSAP) flaps. METHODS: We enrolled a total of 18 patients with sacral and ischial region defects reconstructed with LSAP flaps in the study between September 2014 and October 2015. The patients were evaluated in terms of age, sex, neurological situation, etiology, defect size, defect region, flap size, perforator number, and postoperative complications. RESULTS: No patient had hematoma, seroma, and complications of the donor area. In the postoperative period, 2 patients were observed to have short-term complications (11.1%) including a partial flap loss (5.5%) due to distal venous failure (flap survival rate, 95%) and a wound site infection (5.5%). Duration of follow-up of the patients ranged between 26 and 38 months. Recurrence was observed from long-term complications of 4 patients' pressure sores (22%). CONCLUSIONS: The LSAP flap has not been frequently described in the literature. We believe that LSAP flap is a flap of choice that should be considered preferably for sacral and ischial defects, which can be reliably elevated over pedicles and has short surgery duration and low surgical morbidity.

Avulsion fracture of the ischial tuberosity treated with the suture bridge technique: a case report.

BACKGROUND: In cases of avulsion fracture of the ischial tuberosity in which the bone fragments are substantially displaced, nonunion may cause pain in the ischial area. Various surgical procedures have been reported, but achieving sufficient fixation strength is difficult. CASE PRESENTATION: We treated a 12-year-old male track-and-field athlete with avulsion fracture of the ischial tuberosity by suture anchor fixation using the suture bridge technique. The boy felt pain in the left gluteal area while running. Radiography showed a left avulsion fracture of the ischial tuberosity with approximately 20-mm displacement. Union was not achieved by conservative non-weight-bearing therapy, and muscle weakness persisted; therefore, surgery was performed. A subgluteal approach was taken via a longitudinal incision in the buttocks, and the avulsed fragment was fixed with five biodegradable suture anchors using the suture bridge technique. CONCLUSIONS: Although the majority of avulsion fractures of the ischial tuberosity can be treated conservatively, patients with excessive displacement require surgical treatment. The suture bridge technique provided secure fixation and enabled an early return to sports activities.

Adaptation of a MR imaging protocol into a real-time clinical biometric ultrasound protocol for persons with spinal cord injury at risk for deep tissue injury: A reliability study.

BACKGROUND: High strain in soft tissues that overly bony prominences are considered a risk factor for pressure ulcers (PUs) following spinal cord impairment (SCI) and have been computed using Finite Element methods (FEM). The aim of this study was to translate a MRI protocol into ultrasound (US) and determine between-operator reliability of expert sonographers measuring diameter of the inferior curvature of the ischial tuberosity (IT) and the thickness of the overlying soft tissue layers on able-bodied (AB) and SCI using real-time ultrasound. MATERIAL AND METHODS: Part 1: Fourteen AB participants with a mean age of 36.7 ± 12.09 years with 7 males and 7 females had their 3 soft tissue layers in loaded and unloaded sitting measured independently by 2 sonographers: tendon/muscle, skin/fat and total soft tissue and the diameter of the IT in its short and long axis. Part 2: Nineteen participants with SCI were screened, three were excluded due to abnormal skin signs, and eight participants (42%) were excluded for abnormal US signs with normal skin. Eight SCI participants with a mean age of 31.6 ± 13.6 years and all male with 4 paraplegics and 4 tetraplegics were measured by the same sonographers for skin, fat, tendon, muscle and total. Skin/fat and tendon/muscle were computed. RESULTS: AB between-operator reliability was good (ICC = 0.81-0.90) for 3 soft tissues layers in unloaded and loaded sitting and poor for both IT short and long axis (ICC = -0.028 and -0.01). SCI between-operator reliability was good in unloaded and loaded for total, muscle, fat, skin/fat, tendon/muscle (ICC = 0.75-0.97) and poor for tendon (ICC = 0.26 unloaded and ICC = -0.71 loaded) and skin (ICC = 0.37 unloaded and ICC = 0.10). CONCLUSION: A MRI protocol was successfully adapted for a reliable 3 soft tissue layer model and could be used in a 2-D FEM model designed to estimate soft tissue strain as a novel risk factor for the development of a PU.

Trunk Function and Ischial Pressure Offloading in Individuals with Spinal Cord Injury.

OBJECTIVE: To determine if there is a relationship between trunk function and offloading of the ischial tuberosities in individuals with Spinal Cord Injury (SCI). DESIGN: Prospective cross-sectional evaluation. SETTING: Sub-acute rehabilitation hospital. PARTICIPANTS: Fifteen non-ambulatory participants with complete or incomplete traumatic and non-traumatic SCI, American Spinal Injury Association Impairment Scale (AIS), Classification A-D. OUTCOME MEASURES: Isometric trunk strength using a hand held dynamometer, the ability to reach using the multidirectional reach test and offloading times of the ischial tuberosities using a customized pressure mat. RESULTS: Participants who were able to engage in the multidirectional reach test were defined as "Reachers", whereas individuals who were unable to engage in the multidirectional reach test were defined as "Non-Reachers". Trunk strength was significantly higher in Reachers compared with Non-Reachers (P < 0.05). Offloading times over the left and right ischial tuberosities were lower in Non-Reachers when compared with Reachers, however the results were statistically significant only for offloading over the right ischial tuberosity (P < 0.05). There was no correlation between trunk strength and pressure offloading times for both groups. CONCLUSIONS: Regardless of an individual's ability to engage in a reaching task, participants with spinal cord injury spent more time offloading the left ischial tuberosity compared with the right ischial tuberosity. The study highlights the need to identify factors that may contribute to offloading behavior in individuals with spinal cord injury who lack sufficient trunk strength.

van Neck-Odelberg Disease: A 3.5-Year Follow-Up Case Report and Systematic Review.

V an Neck-Odelberg disease (VND) is a benign skeletal overgrowth of the ischiopubic synchondrosis (IPS) in prepubescent patients. There is a paucity of long-term follow-up data and reviews on management decision-making. We report on a 15-year-old female, with a history of sickle-cell disease (HbSS), presenting with unilateral groin pain. Patient's physical examination, radiographs, and a literature-review determined a diagnosis of VND. Conservative treatment was issued. Clinical symptoms resolved at three months, followed by complete lesion resolution at three years. Additionally, a search of Medline (PubMed), EMBASE, and OVID databases was performed. Reports including VND/IPS diagnosis, treatment, or follow-up decisions were identified. Systematic-review found 17 relevant articles, reporting on 29 patients. Patients presented with groin (51.7%) or buttock (20.7%) pain, and were diagnosed using X-ray (n=23) and magnetic resonance imaging (MRI) (n=17). Twenty-five patients were treated conservatively, with two (8.0%) reports of surgical intervention. Average follow-up was 6.25 months. Our case report and systematic-review support conservative treatment for VND.

Análisis del comportamiento mecánico del tejido subyacente a las tuberosidades isquiáticas por medio del método del elemento finito / Analysis of mechanical behavior of the underlying tissue to the ischial tuberosities using finite element method

Las úlceras por presión son las complicaciones secundarias más comunes a una lesión medular, las cuales ponen en riesgo tanto la salud como la vida de quienes las padecen. Las úlceras por presión más comunes en lesionados medulares aparecen en la región pélvica, principalmente en las tuberosidades isquiáticas (TI's). Una estrategia usada en la clínica es medir la presión generada entre el paciente y la superficie donde se encuentra para evaluar el riesgo que representa dicha superficie para el desarrollo de úlceras por presión sin embargo, este tipo de mediciones superficiales no garantizan que la presión en los tejidos internos subyacentes a prominencias óseas sea inocua. Con el fin de estudiar los mecanismos de formación de úlceras por presión, se realizó el análisis de un modelo de pelvis y tejido subyacente por medio del Método de los Elementos Finitos (MEF). De esta manera se puede estudiar el comportamiento de las TI's sobre su tejido circundante, así como analizar los efectos biomecánicos que provocan las úlceras. Se construyó el modelo computacional por medio de un software de CAD (Computing Aided Design) de la pelvis a partir de cortes tomográficos. El modelo fue exportado al software COMSOL y se analizaron seis casos de estudio: un análisis de la pelvis sobre bloques de tejido sano y cinco casos más, los cuales simulan lesiones en el tejido con distintas profundidades, representando úlceras superficiales e internas. Los resultados mostraron que los puntos de máximo esfuerzo, en todas las pruebas, se localizan justo debajo de la TIs además se encontró que las lesiones internas presentan mayores esfuerzos y deformaciones, los cuales pueden ser precursores de daño en el tejido.

Pressure ulcers are the most common secondary complication to a spinal cord injury, which endanger both health and life of the patients who suffer them. The most common pressure ulcers in spinal cord injuries occur in the pelvic region, mainly in the ischial tuberosities (ITs). A strategy used in clinic is to quantify the pressure generated between the patient and the surface, in order to assess the risk posed by that surface for developing pressure ulcers. Despite this, this type of surface measurements does not guarantee that pressure in the internal tissues underlying to bony prominences, to be safe. In order to study the mechanisms of formation of pressure ulcers, an analysis of a model of the pelvis and its underlying tissue was performed using the Finite Element Method (FEM). By this means we can study the behavior of ITs on its surrounding tissue, and at the same time, we analyze the biomechanical effects those cause ulcers. The computational model of the pelvis was built from tomographic slices using CAD software (Computing Aided Design). The model was exported to the finite element software COMSOL and six study cases were analyzed: an analysis of the pelvis on healthy tissue blocks and five more cases, which simulate tissue injury with different depths, representing surface and internal ulcers. The results showed that the maximum stress points in all tests are located just below the ITs it was also found that internal injuries present higher stresses and strains, which can be precursors of tissue damage.

[Van Neck-Odelberg disease. Report of two cases]. / A van Neck-Odelberg-betegség bemutatása két eset kapcsán.

Osteochondritis ischiopubica or van Neck-Odelberg disease is characterized by atypical ossification of the ischiopubic synchondrosis. Clinical symptoms are usually pain, limping and limited range of motion of the hip joint. Radiologic images may be confused with the possibility of fracture, tumor or inflammation. In some cases it may be difficult to set up the accurate diagnosis, and during the diagnostic process it is essential that van Neck-Odelberg disease should be considered. In this paper the authors draw attention to this rare disorder and they present the history of two patients who posed diagnostic difficulties.

Biomechanical modeling to prevent ischial pressure ulcers.

With 300,000 paraplegic persons only in France, ischial pressure ulcers represent a major public health issue. They result from the buttocks׳ soft tissues compression by the bony prominences. Unfortunately, the current clinical techniques, with - in the best case - embedded pressure sensor mats, are insufficient to prevent them because most are due to high internal strains which can occur even with low pressures at the skin surface. Therefore, improving prevention requires using a biomechanical model to estimate internal strains from skin surface pressures. However, the buttocks׳ soft tissues׳ stiffness is still unknown. This paper provides a stiffness sensitivity analysis using a finite element model. Different layers with distinct Neo Hookean materials simulate the skin, fat and muscles. With Young moduli in the range [100-500 kPa], [25-35 kPa], and [80-140 kPa] for the skin, fat, and muscles, respectively, maximum internal strains reach realistic 50 to 60% values. The fat and muscle stiffnesses have an important influence on the strain variations, while skin stiffness is less influent. Simulating different sitting postures and changing the muscle thickness also result in a variation in the internal strains.

Effects of electrical stimulation-induced gluteal versus gluteal and hamstring muscles activation on sitting pressure distribution in persons with a spinal cord injury.

STUDY DESIGN: Ten participants underwent two electrical stimulation (ES) protocols applied using a custom-made electrode garment with built-in electrodes. Interface pressure was measured using a force-sensitive area. In one protocol, both the gluteal and hamstring (g+h) muscles were activated, in the other gluteal (g) muscles only. OBJECTIVES: To study and compare the effects of electrically induced activation of g+h muscles versus g muscles only on sitting pressure distribution in individuals with a spinal cord injury (SCI). SETTING: Ischial tuberosities interface pressure (ITs pressure) and pressure gradient. RESULTS: In all participants, both protocols of g and g+h ES-induced activation caused a significant decrease in IT pressure. IT pressure after g+h muscles activation was reduced significantly by 34.5% compared with rest pressure, whereas a significant reduction of 10.2% after activation of g muscles only was found. Pressure gradient reduced significantly only after stimulation of g+h muscles (49.3%). g+h muscles activation showed a decrease in pressure relief (Δ IT) over time compared with g muscles only. CONCLUSION: Both protocols of surface ES-induced of g and g+h activation gave pressure relief from the ITs. Activation of both g+h muscles in SCI resulted in better IT pressure reduction in sitting individuals with a SCI than activation of g muscles only. ES might be a promising method in preventing pressure ulcers (PUs) on the ITs in people with SCI. Further research needs to show which pressure reduction is sufficient in preventing PUs.

Can excessive lateral rotation of the ischium result in increased acetabular anteversion? A 3D-CT quantitative analysis of acetabular anteversion in children with unilateral developmental dysplasia of the hip.

BACKGROUND: The purposes of this study were to observe whether increased acetabular anteversion was a universal finding and whether excessive lateral rotation of the ischium was correlated with increased acetabular anteversion. METHODS: We retrospectively reviewed 90 patients with unilateral developmental dysplasia of the hip (DDH), including 77 female patients and 13 male patients with an average age of 18 months (range, 6 to 60 mo). A total of 31 children were involved in the normal control group, including 14 girls and 17 boys with an average age of 21 months (range, 7 to 48 mo). The acetabular anteversion angle (AA), pubic relative length (PRL), ischiac relative distance (IRD), lateral rotational angle of the ischium (IA), and pubic rotational angle were compared between the affected hips and the unaffected hips in the unilateral DDH group and between the right hips and left hips in the normal control group. RESULTS: No retroverted acetabulum was found in any hip. No significant differences in AA, IA, pubic rotational angle, IRD, and PRL were found between the left and right hips in the normal control group. However, the PRL was shorter in the affected hips than in the unaffected hips (P < 0.05). The average IA, AA, and IRD in the affected hips were larger than that in the unaffected hips (P < 0.05). The IA was positively correlated with AA and IRD in the DDH group. CONCLUSIONS: Increased acetabular anteversion in affected hips is a universal finding in unilateral DDH. The deficiency of the anterior wall in the acetabulum is not a unique reason for increased acetabular anteversion in unilateral DDH, because it is also correlated with excessive lateral rotation of the ischium. LEVEL OF EVIDENCE: IV.

Exposure to internal muscle tissue loads under the ischial tuberosities during sitting is elevated at abnormally high or low body mass indices.

Deep tissue injury (DTI) is a severe pressure ulcer characteristic of chairfast or bedfast individuals, such as those with impaired mobility or neurological disorders. A DTI differs from superficial pressure ulcers in that the onset of DTI occurs under intact skin, in skeletal muscle tissue overlying bony prominences, and progression of the wound continues subcutaneously until skin breakdown. Due to the nature of this silently progressing wound, it is highly important to screen potentially susceptible individuals for their risk of developing a DTI. Abnormally low and high values of the body mass index (BMI) have been proposed to be associated with pressure ulcers, but a clear mechanism is lacking. We hypothesize that during sitting, exposure to internal muscle tissue loads under the ischial tuberosities (IT) is elevated at abnormally high or low body mass indices. Our aims in this study were: (a) to develop biomechanical models of the IT region in the buttocks that represent an individual who is gaining or losing weight drastically. (b) To determine changes in internal tissue load measures: principal compression strain, strain energy density (SED), principal compression stress and von Mises stress versus the BMI. (c) To determine percentage volumes of muscle tissue exposed to critical levels of the above load measures, which were defined based on our previous animal and tissue engineered model experiments: strain>or=50%, stress>or=2 kPa, SED>or=0.5 kPa. A set of 21 finite element models, which represented the same individual, but with different BMI values within the normal range, above it and below it, was solved for the outcome measures listed above. The models had the same IT shape, size, distance between the IT, and (non-linear) mechanical properties for all soft tissues, but different thicknesses of gluteus muscles and fat tissue layers, corresponding to the BMI level. The resulted data indicated a trend of progressive increase in internal tissue loading, particularly in volumetric exposure to critical loading for BMI values outside the 17

Biomechanical effects of sitting with adjustable ischial and lumbar support on occupational low back pain: evaluation of sitting load and back muscle activity.

BACKGROUND: Compared to standing posture, sitting decreases lumbar lordosis, increases low back muscle activity, disc pressure, and pressure on the ischium, which are associated with occupational LBP. A sitting device that reduces spinal load and low back muscle activities may help increase sitting comfort and reduce LBP risk. The objective of this study is to investigate the biomechanical effect of sitting with a reduced ischial support and an enhanced lumbar support (Off-Loading) on load, interface pressure and muscle activities. METHODS: A laboratory test in low back pain (LBP) and asymptomatic subjects was designed to test the biomechanical effect of using the Off-Loading sitting posture. The load and interface pressure on seat and the backrest, and back muscle activities associated with usual and this Off-Loading posture were recorded and compared between the two postures. RESULTS: Compared with Normal (sitting upright with full support of the seat and flat backrest) posture, sitting in Off-Loading posture significantly shifted the center of the force and the peak pressure on the seat anteriorly towards the thighs. It also significantly decreased the contact area on the seat and increased that on the backrest. It decreased the lumbar muscle activities significantly. These effects are similar in individuals with and without LBP. CONCLUSION: Sitting with reduced ischial support and enhanced lumbar support resulted in reduced sitting load on the lumbar spine and reduced the lumbar muscular activity, which may potentially reduce sitting-related LBP.

Strains and stresses in sub-dermal tissues of the buttocks are greater in paraplegics than in healthy during sitting.

A pressure-related deep tissue injury (DTI) is a severe pressure ulcer, which initiates in muscle tissue overlying a bony prominence (e.g. the ischial tuberosities, IT) and progresses outwards through fat and skin, unnoticed by the paralyzed patient. We recently showed that internal strains and stresses in muscle and fat of individuals at anatomical sites susceptible to DTI can be evaluated by integrating Open-MRI scans with subject-specific finite element (FE) analyzes (Linder-Ganz et al., Journal of Biomechanics, 2007); however, sub-dermal soft tissue strains/stresses from paraplegics are still missing in literature. We hypothesize that the pathoanatomy of the buttocks in paraplegia increases the internal soft tissue loads under the IT, making these patients inherently susceptible to DTI. We hence compared the strain and stress peaks in the gluteus muscle and fat tissues under the IT of six healthy and six paraplegic patients, using the coupled MRI-FE method. Peak principal compression, principal tension, von Mises and shear strains in the gluteus were 1.2-, 3.1-, 1.4- and 1.4-fold higher in paraplegics than in healthy, respectively (p<0.02). Likewise, peak principal compression, principal tension, von Mises and shear stresses in the gluteus were 1.9-, 2.5-, 2.1- and 1.7-fold higher for the paraplegics (p<0.05). Peak gluteal compression and shear stresses decreased by as much as 70% when the paraplegic patients moved from a sitting to a lying posture, indicating on the effectiveness of recommending such patients to lie down after prolonged periods of sitting. This is the first attempt to compare internal soft tissue loads between paraplegic and healthy subjects, using an objective standardized bioengineering method of analysis. The findings support our hypothesis that internal tissue loads are significantly higher in paraplegics, and that postural changes significantly affect these loads. The method of analysis is useful for quantifying the effectiveness of various interventions to alleviate sub-dermal tissue loads at sites susceptible to pressure ulcers and DTI, including cushions, mattresses, recommendations for posture and postural changes, etc.

Risk factors for a pressure-related deep tissue injury: a theoretical model.

Pressure-related deep tissue injury is the term recommended by the United States National Pressure Ulcer Advisory Panel to describe a potentially life-threatening form of pressure ulcers, characterized by the presence of necrotic tissue under intact skin, and associated with prolonged compression of muscle tissue under bony prominences. In this study, a theoretical model was used to determine the relative contributions of the backrest inclination angle during prolonged wheelchair sitting, the muscle tissue stiffness and curvature of the ischial tuberosities (ITs) to the risk for injury in the gluteus muscles that pad the IT bones during sitting. The model is based on Hertz's theory for analysis of contact pressures between a rigid half-sphere (bone) and an elastic half-space (muscle). Hertz's theory is coupled with an injury threshold and damage law for muscle-both obtained in previous studies in rats. The simulation outputs the time-dependent bone-muscle contact pressures and the injured area in the gluteus. We calculated the full-size (asymptotic) injured area in the gluteus and the time for injury onset for different sitting angles alpha (90-150 degrees), muscle tissue long-term shear moduli G (250-1,200 Pa) and bone diameters D (8-18 mm). We then evaluated the sensitivity of model results to variations in these parameters, in order to determine how injury predictions are affected. In reclined sitting (alpha=150 degrees) the full-size injured area was approximately 2.1-fold smaller and the time for injury onset was approximately 1.3-fold longer compared with erect sitting (alpha=90 degrees). For greater G the full-size injured area was smaller but the time for injury onset was shorter, e.g., increasing G from 250 to 1200 Pa decreased the full-size injured area approximately 2.5-fold, but shortened the time for injury onset 6.2-fold. For smaller D the time for injury onset dropped, e.g., decreased approximately 1.5-fold when D decreased from 18 to 8 mm. Interestingly, the full-size injured area maximized at D of about 12 mm but decreased for smaller or larger D. The susceptibility to sitting-acquired deep tissue injury strongly depends on the geometrical and biomechanical characteristics of the bone-muscle interface, and, particularly, on the radius of curvature of the IT which mostly influenced the size of the wound, and on the muscle stiffness which dominantly affected the time for injury onset.

Pressure changes under the ischial tuberosities of seated individuals during sacral nerve root stimulation.

Neuromuscular stimulation via the sacral nerve roots is proposed for prevention of ischial pressure ulcers following a spinal cord injury (SCI). Acute effects of sacral functional magnetic stimulation (FMS) on seat interface pressure changes were investigated in five nondisabled volunteers. Similar effects were demonstrated with functional electrical stimulation in people with SCI who used a sacral anterior root stimulator implant. The results indicated that sacral nerve root stimulation, either by FMS or implanted electrical stimulation, induced gluteus maximus contraction and mild pelvic tilt sufficient for clinically significant reductions in ischial pressures during sitting.