Robot-aided motion planning for knee joint rehabilitation with two robot-manipulators.

In this paper, we propose a simultaneous design method of motion and external force trajectories for knee joint rehabilitation based on the biomechanical analysis of the lower limb. In this method we assume to use two robots manipulators which provide forces and moments at shank and thigh. We developed a 7 degree of freedom musculoskeletal model of lower limb with 19 muscles. The valuation function of rehabilitation efficiency e has been maximized by Genetic Algorithm (GA) that refers to the musculoskeletal model and tunes motion trajectory of the robots and forces acting on the shank and thigh.

Robot-aided rehabilitation task design for inner shoulder muscles.

In this paper, we propose a simultaneous design method of motion and external force trajectories for shoulder inner muscles in the robot-aided rehabilitation system, based on a biomechanical analysis of patient's body. The rehabilitation efficiency evaluation function was maximized by Genetic Algorithm (GA), where the structure of spline curves parameters are pre-defined, and the structural parameters are explored to design smooth rehabilitation motion and external force trajectories.

Incidence of symptomatic autonomic dysreflexia varies according to the bowel and bladder management techniques in patients with spinal cord injury.

STUDY DESIGN: A retrospective, multicenter study. OBJECTIVES: To investigate the relationship between bowel and bladder management methods and symptomatic autonomic dysreflexia (AD) during hospitalization in patients with spinal cord injury (SCI). SETTING: Twenty-eight Rosai hospitals in Japan. METHODS: The study subjects were 571 patients with SCI who had been admitted to 28 Rosai hospitals between April 1997 and March 2007 for rehabilitation therapy and fulfilled the following criteria: (1) SCI at or above sixth thoracic level, (2) discharged from hospital after more than 4 months of admission for initial injury and (3) lack of pressure ulcers, deep venous thrombosis, ureteral and renal stones or heterotopic ossification throughout hospitalization to exclude possible influence of these complications on cardiovascular reflexes. The study subjects were examined for the incidence of symptomatic AD according to age, sex, ASIA Impairment Scale, injury level, bowel and bladder management techniques at discharge. RESULTS: The Rosai Hospital registry included 3006 persons with SCI during 1997-2007, and 571 patients fulfilled the above criteria. The highest incidence of symptomatic AD was diagnosed in subjects using reflex voiding and in those using manual removal of stool. By contrast, the lowest incidence of symptomatic AD was in those on continent spontaneous voiding and continent spontaneous defecation. CONCLUSION: Medical staff should evaluate the presence of AD in patients with SCI at or above the T6 level under bladder and bowel management such as reflex voiding and manual removal of stool.

A new walking orthosis for paraplegics: hip and ankle linkage system.

For paraplegics, two major disadvantages of hip-knee-ankle-foot orthotic systems that have a medial single hip joint are the short stride and horizontal rotation of the pelvis. The authors consider the pelvic rotation is caused by two factors; one is the lack of a mechanism to assist hip flexion, and the other is fixed ankle joints that cause instability when the step length becomes longer. Users must rotate their pelvis to initiate a swing in their legs and to achieve stability by making their two legs as parallel as possible in order to avoid losing balance. To overcome those disadvantages, the authors developed a new orthosis named "HALO" (Hip and Ankle Linked Orthosis), which has a linking mechanism that connects both ankle joints with a medial single hip joint. This new orthosis allows users to keep both feet always parallel to the floor while walking, and assists the swinging of the leg when the contralateral ankle is flexed dorsally by loading. Gait analysis revealed that the pelvic rotation with "HALO" either in parallel bars or with Lofstrand crutches was within 20 degrees, which was within the physiologically normal level.

Normal hip joint contact pressure distribution in single-leg standing--effect of gender and anatomic parameters.

A practical and easy-to-use analysis technique that can study the patient's hip joint contact force/pressure distribution would be useful to assess the effect of abnormal biomechanical conditions and anatomical deformities on joint contact stress for treatment planning purpose. This technique can also help to establish the normative database on hip joint contact pressure distribution in men and women in different age groups. Twelve anatomic parameters and seven biomechanical parameters of the hip joint in a normal population (41 females, 15 males) were calculated. The inter-parameter correlations were investigated. The pressure distribution in the hip joint was calculated using a three-dimensional discrete element analysis (DEA) technique. The 3D contact geometry of the hip joint was estimated from a 2D radiograph by assuming that the femoral head and the acetabular surface were spherical in shape. The head-trochanter ratio (HT), femoral head radius, pelvic height, the joint contact area, the normalized peak contact pressure, abductor force, and the joint contact force were significantly different between men and women. The normalized peak contact pressure was correlated both with acetabular coverage and head-trochanter ratio. Change of abductor force direction within normal variation did not affect the joint peak contact pressure. However, in simulated dysplastic conditions when the CE angle is small or negative, abductor muscle direction becomes very sensitive in joint contact pressure estimation. The models and the results presented can be used as the reference base in computer simulation for preoperative planning in pelvic or femoral osteotomy.

Theoretical stress analysis in wrist joint--neutral position and functional position.

A three-dimensional rigid body spring model (3D-RBSM) was used to analyse force distribution through the wrist joint. In the neutral position, 48% of the force was transmitted through the radioscaphoid fossa, 40% through the radiolunate fossa, and 12% through the triangular fibrocartilage complex. In the functional position, the wrist joint was slightly extended, resulting in significantly increased force through the lunate (53%). The lunate appears to bear more load than has been reported previously.

The hip in adults with classic bladder exstrophy: a biomechanical analysis.

We studied the untreated pelvic deformity in 14 adult patients with bladder exstrophy to determine the relative hip-joint force and stress and their effects on the clinical status of the hip. Pelvic radiographs were used for biomechanical analysis to calculate joint force and joint stress (force/area) relative to partial body weight, which allowed comparison between patients and age-matched controls. IOWA hip ratings were used for clinical evaluation, and hips were scored radiographically for degenerative joint disease. The mean relative joint force and joint stress was significantly higher for exstrophy patients (p < 0.001). In addition, the mean distance from the body center to the center of the femoral head was significantly increased (p < 0.001) in bladder exstrophy patients. An increase in diastasis correlated with an approximate 30% increase in the distance from the center of the femoral head to the body midline. The mean distance from the greater trochanter to the femoral head center was significantly less (p < 0.02) and the center-edge angle was significantly decreased in exstrophy patients (p < 0.05). Two patients' hips showed significant subluxation, and one of these showed degenerative hip disease in association with poor IOWA and radiographic scores. The force and stress on the hip joint are increased in untreated adult bladder exstrophy patients. Further longitudinal study is indicated to validate these findings and to determine whether clinically important degenerative changes are occurring. This could affect treatment recommendations in childhood.

Force transmission through the wrist joint in Kienböck's disease: a two-dimensional theoretical study.

This study quantifies the changes in force and pressure distributions across the wrist joint in different stages of Kienböck's disease using a 2-dimensional computer simulation model. Twenty-four cases classified as Lichtman's stage II, IIIA, or IIIB (8 cases in each category) were analyzed using the rigid body spring model technique. A 2-dimensional model in the posteroanterior plane of the wrist was loaded through the metacarpals under a total force of 142 N. The joint forces, peak pressures, and ligament tensions calculated on the involved side were normalized against the contralateral normal side values of the same patient. The results demonstrated that significant changes of the force transmission across the wrist joint occurred only from stage IIIA to IIIB, in which scaphoid rotation was prominent. On the basis of this study, scaphoid rotation plays an important role in affecting the wrist joint contact pressure distribution. This may be responsible for the progression of Kienböck's disease.

Biomechanical analysis of limited intercarpal fusion for the treatment of Kienböck's disease: a three-dimensional theoretical study.

Although several types of intercarpal fusion have been advocated for the treatment of Kienbock's disease, the clinical outcome of each procedure is still inconclusive. The joint load and ligament tension based on a three-dimensional model were measured to determine which intercarpal fusion procedures unload the lunate and whether they alter the force transmission through the entire wrist joint. Ten theoretical models of wrists were used to simulate three different operative procedures: capitate-hamate fusion, scapho-trapezial-trapezoidal fusion, and scaphocapitate fusion. A discrete element analysis technique was used to perform these investigations. The joint force and ligament tension of normal wrists and of simulated operative procedures were calculated according to the deformation of each spring element, simulating the articular cartilage and the carpal ligaments. Scaphocapitate and scapho-trapezial-trapezoidal fusions significantly decreased the joint force at the radiolunate joint and the lunocapitate joint compared with the intact wrist. In contrast, these fusions significantly increased this value at the radioscaphoid joint in comparison with the intact wrist. In the midcarpal joint, scaphocapitate fusion also increased the joint force at the scapho-trapezial-trapezoidal joints and at the triquetral-hamate joint, whereas scapho-trapezial-trapezoidal fusion increased it at the scapho-capitate joint. Capitate-hamate fusion yielded no significant changes of the joint forces through the entire wrist joint. In the analysis of ligament tension, scaphocapitate and scapho-trapezial-trapezoidal fusions significantly decreased the tension only in the dorsal scapholunate ligament. These findings demonstrate that scaph-ocapitate and scapho-trapezial-trapezoidal fusions are effective in decompressing the lunate. By contrast, capitate-hamate fusion is ineffective in reducing lunate compression. Although scaphocapitate and scapho-trapezial-trapezoidal fusions are recommended for the treatment of Kienbock's disease, clinicians should consider that the increase of force transmission through the radioscaphoid and the midcarpal joints may lead to early degenerative changes after these procedures have been performed.

Correlation between bone mineral density and intervertebral disc degeneration.

STUDY DESIGN: Intervertebral disc area, disc bulge ratio, and bone mineral density were measured in 86 postmenopausal women and the data analyzed. OBJECTIVE: To examine quantitatively the correlation between intervertebral disc degeneration and bone mass. SUMMARY OF BACKGROUND DATA: In results of previous studies, an inverse correlation between osteoporosis and spondylosis has been reported. In these studies, only radiographic findings were used to evaluate spondylosis; changes in the intervertebral disc itself were not investigated. METHODS: To determine bone mass, total-body bone mineral density, lumbar bone mineral density, and age-matched control values of bone mineral density were measured by dual-energy X-ray absorptiometry in all cases. To evaluate intervertebral disc degeneration, disc area and disc bulge ratio (calculated by measuring the areas protruding from lines connecting the middle points of the anterior and posterior borders of the vertebral bodies) were obtained from four discs, using magnetic resonance images of the lumbar spine. The correlation between bone mass data and disc area data was analyzed. RESULTS: Bone mineral density showed a significant decrease with increasing age. Disc area and disc bulge ratio had no relation to age. There was a negative correlation between total-body bone mineral density, lumbar bone mineral density, and age-matched control values versus disc area, and a positive correlation between all bone mineral density data and the disc bulge ratio. CONCLUSIONS: According to the results of the analysis by disc morphology and bone mass, especially total body bone mineral density, bone mass has an inverse correlation to intervertebral disc degeneration--i.e., reduction and disc bulge--which is important when considering degenerative spinal diseases and osteoporosis.

Virtual reality (VR) techniques in orthopaedic research and practice.

Modeling the musculoskeletal joint system using biomechanical analysis and computer graphics techniques allows us to visualize normal, diseased and reconstructed joint function. This model can be used to study the loading of bones and joints under theoretical and simulated activities. In this study, intact cadavers were imaged using MRI, CT scanning and cryo-sectioning techniques. Using sequential pixel information of bone and soft tissue boundaries collected from digital camera images, MRI and CT scans, the volumetric models of the musculoskeletal joint system are reconstructed. "Descriptive geometry" techniques which treat bones as rigid bodies and cartilage, ligament and muscles as deformable bodies were used to construct the model. Joint resultant forces and moments were determined using an inverse dynamics formulation, while ligament tension, joint contact pressure, and bone stresses are solved through a simplified Rigid Body Spring Modeling technique and the Finite Element Method. The results under static and dynamic loading activities can be visualized using interactive computer graphics. The advantages of such a model are the elimination of the need for large numbers of intact cadaveric specimens, and the unprecedented capability to study joint loading responses under normal, abnormal and surgically reconstructed states. Such a model and its analytical capability are ideal for pre-operative planning and computer-assisted orthopaedic surgery. This Visual, Interactive, Computational, and Anatomic Model(VICAM) and its associated analysis capability represent the next generation of technology which will have an enormous impact in orthopaedic research, education and patient care.

A computer simulation study of normal and abnormal hip joint contact pressure.

The contact pressure on 112 normal hip joints and 66 acetabular dysplastic hip joints was analysed using a three-dimensional rigid body spring model. Geometric models were made from conventional anteroposterior radiographs, with the assumption that the acetabular surface was spherical. In normal hips, the distribution of contact pressure was almost even over the joint surface, and the maximum contact pressure was relatively low. However, in a dysplastic hip joint, the pressure was concentrated on the anterolateral edge of the acetabulum and increased enormously not only with the reduction in lateral coverage but also with the reduction in the anterior coverage of the acetabulum. This result indicates that a three-dimensional analysis is indispensable for estimating the mechanical effect on acetabular cartilage.

Indications and results of vascularized pedicle iliac bone graft in avascular necrosis of the femoral head.

Several reports describe methods of treatment for avascular necrosis of the femoral head (ANFH) involving 0 to 2 mm of collapse. Some cases of ANFH have good prognoses, requiring only non-weight-bearing treatment. Other cases rapidly progress to collapse and complete destruction with enlargement of the necrotic area. The progression of the necrotic area is related to the activity of the original disease, steroid treatment, and the size and location of the necrotic area in the early stages of the disorder. In this report, a vascularized pedicle bone graft was used to treat ANFH, particularly those cases identified as Stage II on the system established by the Japanese Investigation Committee. Surgery involved curettage of necrotic bone, implantation of spongy bone, and application of a vascularized pedicle bone graft. Grafts were taken from the ilium and included the superficial circumflex iliac artery (SCIA). A bony canal was made in the anterior femoral neck, from which the necrotic bone was curetted and to which the bone graft was applied. The deep circumflex iliac artery (DCIA) was also used in combination with the SCIA. The postoperative weight-bearing period was six months. Follow-up periods lasted one to six years. Seventeen of 23 Stage II joints (19 cases) achieved satisfactory results at a mean of three years after surgery. Three Stage II joints and three Stage III joints continue to have significant problems. One of these six has been converted to a dual-bearing type endoprosthesis. The unsuccessful results generally occurred in patients who were treated with steroids.

Effect of hyperbaric oxygenation on femoral head osteonecrosis in spontaneously hypertensive rats.

We investigated the effects of hyperbaric oxygenation (HBO) on ischemic osteonecrosis and on ossification disturbance of the femoral heads in growing, spontaneously hypertensive rats (SHR). 10 male SHRs aged 5 weeks (Group A) and another 10 male SHRs aged 8 weeks (Group B) were treated with HBO at 2.8 atmosphere absolute (ATA) for 6 weeks in a total of 30 hours. The control animals, 10 male SHRs (Group C) and 10 male wistar Kyoto rats (WKY, Group D), were kept under normal laboratory conditions. All the rats were killed at the age of 17 weeks for microscopic examination. In Group A, there was no evidence of osteonecrosis, and only 2 femoral heads with ossification disturbance were observed. In Group B, there were 2 femoral heads with osteonecrosis and 1 with ossification disturbance. In contrast, there were 6 femoral heads with osteonecrosis and 4 with ossification disturbance in Group C. It was concluded that HBO prevented osteonecrosis and ossification disturbance of the femoral heads in SHR.

Progression of avascular necrosis of femoral head and choice of treatment.

Observations of the disease course mainly by X-ray were made in 52 patients (85 joints) with avascular necrosis of the femoral head to determine the prognosis and to decide on treatment. The progression of the necrotic area is related to the activity of the original disease, to the size of the necrotic area in the early stages of the disease, and to whether or not the patient received steroid treatment. On the basis of the size and location of the necrotic area, the disease process is divided into four stages, I to IV. The affected heads are also classified into six types according to their site and extent, the degree of flatness of their weightbearing surface, and the presence of cystic lesion. Preventive treatment and conservative observation or transtrochanteric anterior rotational osteotomy and vascularized pedicle bone graft are applicable to cases in Stages I and II. Total hip joint arthroplasties and salvage procedures are performed in Stages III and IV. The usefulness of 99mTc bone scintigraphy was unexpectedly disappointing for diagnosis of the stages of the disease. However, MRI was sensitive for the diagnosis in the early stages of the disease.

Three-dimensional evaluation of acetabular coverage of the femoral head in normal hip joints and hip joints with acetabular dysplasia.

Compared with the assessment by data processing-coupled CT scanning, three dimensional evaluations of the acetabular coverage of the femoral head from a plain X-ray picture of the hip joint is found to be a simpler and easier procedure. In addition, the calculated values agree well with those obtained by CT in reconstruction. Consequently, this method is of great value in evaluating the severity of diseases of the hip joint. The acetabular coverage of the anterior portion of the hip joint is decreased in the elderly even if the hip joint is normal. Because this decrease may result in primary arthrosis deformans, it should be studied further. Rotational acetabular osteotomy (RAO) is a far better method than Salter's for the early stage of coxarthritis. The present study concludes that it is vitally important to maintain the normal ratio of the anterior and posterior coverage and the shape of the acetabular coverage in the treatment of coxarthritis.

The natural course of osteoarthritis of the hip due to subluxation or acetabular dysplasia.

In 59 patients, 86 hips with subluxation or hip dysplasia were examined to determine the natural course of the condition and select suitable treatment. Thirty-three percent of the joints (13/39 hips) developed early osteoarthritis from pre-osteoarthritis within an average term of 9.2 years, while the remaining, sixty-six percent (31/47 hips) developed advanced-stage osteoarthritis from early osteoarthritis within an average term of 7.8 years. Patients were classified into advanced and non-advanced groups according to radiographic analysis of the advanced groups according to radiographic analysis of the advance of the disease and statistical analysis was performed. In pre-osteoarthritis, centre-edge angle, slope of the acetabular roof, acetabular head index, acetabular depth ratio and Japanese Orthopaedic Association (JOA) hip score were significant predictors, while in early osteoarthritis, a broken Shenton's line, cranial joint space and JOA score were significant. On the basis of multiple parameters, formulas for predicting development in patients with pre-osteoarthritis, those with early osteoarthritis, and all patients together were established, with an accuracy of 87%, 71%, and 68%, respectively.