Biomedical subjects

Kazuo Yonenobu

Publications and source records attributed to Kazuo Yonenobu.

At least 19 recordsLinked to original sources

PubMed2007

Surgical treatment of cervical kyphosis in Larsen syndrome: report of 3 cases and review of the literature.

STUDY DESIGN: A retrospective case series. OBJECTIVE: To review the surgical results for midcervical kyphosis in 3 cases with Larsen syndrome, and to discuss the choice of surgical treatments. SUMMARY OF BACKGROUND DATA: Cervical kyphosis is the most hazardous and serious manifestation of Larsen syndrome due to the risk of life-threatening paralysis, and thus usually requires surgical treatment. However, little information has been reported concerning surgical treatments for this challenging condition. METHODS: Three patients with Larsen syndrome were surgically treated for midcervical kyphosis at our institution. RESULTS: An infant with mild cervical kyphosis was successfully treated with posterior arthrodesis using a halo immobilization, and anterior vertebral growth with a mature posterior fusion mass resulted in spontaneous correction of the kyphosis. In the remaining 2 infants with myelopathic symptoms due to severe and structural kyphosis, anterior decompression and fusion via a lateral approach followed by posterior fusion with segmental spinal instrumentation and halo immobilization resulted in improved neurologic symptoms and solid fusion. CONCLUSIONS: Posterior spinal fusion is only indicated for patients with mild and flexible cervical kyphosis, and anterior decompression and circumferential arthrodesis is required for patients with severe kyphotic deformity, who usually develop myelopathic symptoms. Anterior surgery for such a small patient with severe kyphosis involves much higher risk of spinal cord injury during decompression maneuvers and difficulty in stabilization of the reconstructed cervical spine. Therefore, all patients with Larsen syndrome should be screened with radiographs at the first visit to detect cervical kyphosis early so that posterior alone fusion is possible.

Cervical Vertebrae↗

PubMed2006

Adrenocorticotropic hormone and dehydroepiandrosterone sulfate levels of rheumatoid arthritis patients treated with glucocorticoids.

To assess adrenal function with respect to the presence or absence of steroid therapy, we investigated differences in the blood levels of adrenocorticotropic hormone (ACTH) and dehydroepiandrosterone sulfate (DHEAS) in relation to steroid (prednisolone) administration in 123 patients with rheumatoid arthritis (RA). Levels of ACTH and DHEAS were significantly lower in the steroid-treated group than in the non-treated group (ACTH: 11.79 pg/ml vs 27.92 pg/ml) (DHEAS: 418.12 ng/ml vs 883.91 ng/ml) (P<0.0001). We observed no steroid dose-related differences in ACTH levels. However, DHEAS levels showed a slight decrease at a prednisolone dose of 2.5 mg/day, with a significant decrease being observed at a dose of 5 mg/day when statistical adjustments were made for age and sex (P<0.0001). At doses of 7.5 mg/day or greater, DHEAS levels were significantly lower than those for 5 mg/day (P<0.0006). These results suggest that low-dose prednisolone reduces adrenal function in patients with RA. We recommend that doses of prednisolone should be limited to 5 mg/day or less in consideration of adrenal function when treating RA patients. The measurement of ACTH and DHEAS may be useful for evaluating adrenal function in patients with RA.

Adrenal Glands↗

PubMed2006

A biomechanical study of activities of daily living using neck and upper limbs with an optical three-dimensional motion analysis system.

In activities of daily living such as eating meals, the neck and upper limbs move in coordination. However, no methods have been established to analytically and quantitatively capture motion of the neck and limbs during these activities. We used a Vicon 512 system to simultaneously measure ranges of motion (ROMs) for the cervical spine, shoulders, elbows, and forearms. Correlations between the motion analyzer and the universal goniometer were >0.76. Repeatability of measurements using this analyzer were <or=3 degrees for all values. This system is thus highly accurate and can be useful for motion analysis of the neck and upper limbs. The sum of flexion angles for the cervical spine, shoulders and elbows were almost constant for each activity, at 261 degrees for shampooing, 207 degrees for washing the face, and 185 degrees for eating a meal.

Activities of Daily Living↗

PubMed2006

Indication of posterior lumbar interbody fusion for lumbar disc herniation.

OBJECTIVE: To examine whether lumbar disc herniation with massive extrusion and/or segmental instability can be an indicator for spinal fusion or not, by comparing the outcome of posterior lumbar interbody fusion (PLIF) and discectomy alone. METHODS: One hundred seventy-four patients with PLIF and 177 patients with discectomy were retrospectively analyzed. We hypothesized two criteria for fusion: massive herniation and segmental instability. The patients were divided into four groups according to our original criteria: group F-F (n = 96) consisted of the patients who fulfilled the criteria for fusion and underwent PLIF; group nF-F (n = 78) consisted of those who did not fulfill the criteria but had PLIF; group F-nF (n = 30) consisted of those who fulfilled the criteria but underwent discectomy; group nF-nF (n = 147) comprised those who did not fulfill the criteria and underwent discectomy. Each patient was evaluated clinically and radiologically at 5 years after operation. RESULTS: Groups F-F and nF-F had significantly superior results on low back pain compared with group F-nF (F-F vs F-nF, P < 0.05; nF-F vs F-nF, P < 0.01). The frequency of additional operation at the involved level was significantly higher in group F-nF (10.0%) than in group F-F (2.0%) (P < 0.05). Postoperative instability of the adjacent segment developed in 15 cases (8.6%) in groups F-F and nF-F and in 3 cases (1.7%) in groups F-nF and nF-nF (P < 0.01). CONCLUSION: Lumbar disc herniation with massive herniation or segmental instability can be well treated with PLIF.

Adult↗

PubMed2006

Soft-tissue balance evaluation system for total hip arthroplasty by intraoperative contact pressure measurement at the hip joint.

We developed a system for measurement of contact pressure at the hip joint surfaces that enables checking of the artificial hip joint condition during surgery. First, we constructed the pressure sensor that forms the artificial joint. We installed eight small pressure sensors to the spherical head component, a part of the ball-socket joint. Next, we developed software for recording and visualizing the detected pressures that were recorded every 1 ms. The pressure distribution was displayed with the 3D computer graphics in real-time. The system enabled intuitive recognition of pressure direction 3-dimensions. Next, using the system, we conducted measurements during total hip arthroplasty. Although it requires some improvements in its measurement accuracy, the system allows real-time acquisition of information on the artificial hip joint in real-time. Further improvements of the calibration method should enable more accurate measurements. As a complete system, it will be a useful tool for selecting an appropriate implant that fits a patient's hip joint or for estimating the risk of complications after surgery.

Arthroplasty, Replacement, Hip↗

PubMed2005

Wear analysis of retrieved ceramic-on-ceramic articulations in total hip arthroplasty: Femoral head makes contact with the rim of the socket outside of the bearing surface.

We investigated articular bearing surfaces retrieved from three patients with ceramic-on-ceramic total hip arthroplasties using high-quality alumina. The duration of implantation was 3.5, 3.0, and 2.5 years, respectively. Dislocation of the hip joint after implantation did not occur in any patients. The retrieved prostheses were examined by stereomicroscopy and scanning electron microscopy (SEM). In the main load-bearing area, no wear marks were seen in any sockets. However, in all three cases, stripe scars were observed at the rim of the alumina inlay under stereomicroscopy, despite the lack of indentation in the socket and the stem, which suggests impingement. Such scars were not observed on the load-bearing surface. Under SEM, the scars showed excessive wear, including material excavation, that has not been observed in conventional hip simulator experiments. These findings are similar to those of experiments in which a simulator was programmed to distract the femoral head from the socket. The present results suggest that the femoral head can separate from the socket without neck-socket impingement in vivo.

Aged↗

PubMed2005

Computer-assisted measurement of the size of ossification in patients with ossification of the posterior longitudinal ligament in the cervical spine.

BACKGROUND: Progression of ossification of the posterior longitudinal ligament in patients may lead to serious neurological deterioration. A government-funded study group established a manual method of measurement on plain radiographs to detect progression of the ossified lesion. However, this method did not gain wide acceptance because it was time-consuming and complicated, for which drawings of many lines and points are required. We have applied a computer-assisted measurement system to this task and have evaluated inter- and intraexaminer reliability, showing that it is quicker to use and more accurate than the manual method. METHODS: Eight board-certified spine surgeons, acting as the examiners, measured the sizes of the ossified lesions on nine lateral cervical spine radiographs using the computer-assisted measurement system. Following insertion of digitized radiographic image data into a computer, the corners of the vertebral bodies on the displayed images are marked by the examiners, and the software automatically sets reference lines and points. The examiners identify upper, lower, and posterior margins of the ossified lesions, and the software calculates the dimensions of the ossified lesions. Data obtained from eight examiners for length and thickness underwent rigorous statistical analysis by calculating the intraclass correlation coefficients with 95% confidence intervals (CIs) to determine interexaminer reliability and Pearson's correlation coefficients between the two measurements by the same examiner to determine intraexaminer reliability. RESULTS: The intraclass correlation coefficients were 0.927 and 0.968 with 95% CIs of 0.883-0.955 and 0.956-0.978 for measurements of length and thickness, respectively, of the ossified lesions. The Pearson's correlation coefficients for the two measurements by the same examiners were 0.943-0.985 for length and 0.957-0.991 for thickness. CONCLUSIONS: The inter- and intraexaminer reliability using this measurement system was excellent. The method can detect progression of ossification of the posterior longitudinal ligament (OPLL) on plain radiographs with high precision and could become a standard method for measuring the size of OPLL.

Cervical Vertebrae↗

PubMed2005

Huge pelvic mass secondary to wear debris causing ureteral obstruction.

We report an unusual granulomatous reaction of wear debris that produced a huge pelvic mass causing ureteral obstruction. A 72-year-old woman, who received a cemented total hip arthroplasty 30 years ago, was referred to the department of gynecology for examination of a pelvic mass. A computed tomography scan revealed a huge homogenous mass, measuring approximately 20 x 16 x 12 cm, including extensive osteolysis of the left pelvis around the acetabular component. Intravenous pyelogram revealed complete obstruction of the left ureter resulting in hydronephrosis of the left kidney. Histological examination from the biopsy specimen detected polyethylene wear debris in the mass.

Adult↗

PubMed2005

Gait analysis system for assessment of dynamic loading axis of the knee.

The purpose of this study was (1) to demonstrate a computer-assisted gait analysis system that can visualize the locus of the dynamic loading axis on the proximal tibia joint surface, and (2) to assess the accuracy of this system in a patient with bilateral knee osteoarthritis (OA). This system uses force plate data, CT skeletal structure data and motion capture data obtained from an infrared position sensor. The relative positions between bones and markers were used to calculate skeletal model movement based on movement of the markers. The locus of the dynamic loading axis on the knee joint was defined as the point on the proximal tibia joint surface that intersected with the loading axis of the lower limb, which passed through the centre of the femoral head and the centroid of multiple points surrounded by the distal tibia joint surface contour. To assess the accuracy of this system, open MRI was used to evaluate positions of skin markers against bones in six healthy volunteers. The locus in a patient was affected by differences between the varus knee with medial compartment OA on the non-operative side and the knee treated with high tibial osteotomy (HTO) on the opposite side. At knee flexion angles of 0 degrees, 15 degrees and 30 degrees, the mean value of measurement error for point locations on the locus was within 5.6% of joint width in the lateral direction (JWLD) on the proximal tibia joint. This system can provide clinically useful information for evaluation of the dynamic loading axis on the knee joint surface.

Aged↗

PubMed2005

Change in the locus of dynamic loading axis on the knee joint after high tibial osteotomy.

The purpose of this study was to visualise the locus of the dynamic loading axis on the knee joint, and to evaluate changes in this locus during gait after high tibial osteotomy (HTO) in three patients who underwent HTO for medial compartment osteoarthritis (OA) of a varus knee. The bone structure of the lower limb and the relative position of skin markers were acquired from CT images. Motion capture data was acquired using spherical skin markers. Skeletal model movement during gait was calculated based on the movement of the markers. The locus of the dynamic loading axis on the knee joint was defined as the point on the proximal tibia joint surface that intersected with the loading axis of the lower limb, which passed through the centre of the femoral head and the centroid of multiple points surrounded by the distal tibia joint surface contour. This system was able to visualise the locus of the dynamic loading axis on the knee joint and not only lateral but also anterior-posterior direction movement. After HTO, the locus shifted from a medial and posterior area of the medial joint edge of the knee to a central area of the knee joint surface. This indicates that HTO shifted the dynamic loading axis. Lateral movement of the dynamic loading axis in the early stance phase of gait was reduced within a year after HTO.

Aged↗

PubMed2005

Acute arm paresis with cervical spondylosis: three case reports.

BACKGROUND: The mild type of anterior spinal artery syndrome (ASAS) is characterized by motor loss with an absent or insignificant sensory deficit due to a disturbance in the blood supply to the anterior horn of the spinal cord. The clinical symptoms of cervical spondylotic amyotrophy (CSA) are motor loss or atrophy with an absent or insignificant sensory deficit or a long tract sign; however, the pathophysiology has not been clarified. METHODS: Three patients who suffered from palsy of the deltoid and biceps brachii are presented. Magnetic resonance imaging confirmed the intrinsic cord disease as the cause of the paresis. We measured the central motor conduction time (CMCT) and the latencies of the tendon reflex (T waves) of the biceps and triceps and those of the F waves of the abductor pollicis brevis and abductor digiti minimi before, 2 weeks after, and 3 months after starting intravenous injections of prostaglandin E(1) (PGE(1)). RESULTS: In these 3 cases, restoration of muscle strength began after starting injection of PGE(1). The electrophysiologic diagnosis revealed a disturbance of the motor conduction, in the CMCT and the latencies of the T waves, in the paretic muscle, which is more severe than that in other muscles. The radiological diagnosis suggested damage in the spinal cord. Improvements in the disturbance of the motor conduction and those of symptoms were parallel. CONCLUSION: From symptomatologic or radiological viewpoints, it is difficult to differentiate CSA from ASAS with cervical spondylosis. This suggests that there have been patients with ASAS whom we have diagnosed as CSA, and we may add administration of PGE(1) to the treatment for the patients with CSA. The present 3 patients showed improvement of muscle strength after starting injections of PGE(1). Although this improvement was measured by an electrophysiologic method, the mechanisms of PGE(1) require further study.

Acute Disease↗

PubMed2005

Multicenter study investigating the postoperative progression of ossification of the posterior longitudinal ligament in the cervical spine: a new computer-assisted measurement.

OBJECT: Ossification of the posterior longitudinal ligament (OPLL) often progresses after surgery, and this may cause late-onset neurological deterioration. There have been few studies, however, to clarify any correlation between progression and clinical outcome, partly because of the lack of studies involving reliable and reproducible methods by which detection of progression is made possible. The authors conducted a multicenter study to investigate the occurrence of postoperative progression and to elucidate the possible risk factors in a large-scale patient population, and a novel computer-assisted measurement method was used to provide the basis for future clinical studies. METHODS: The authors analyzed lateral plain radiographs obtained immediately and at 1 and 2 years after surgery in 131 patients who underwent posterior decompression at 13 institutions. The x-ray films were transformed via scanner into digital images; the length and thickness of ossifications were measured using a new computer-assisted measurement system, and the incidence of progression was determined. Odds ratios for progression according to age group and types of OPLL were determined and compared to elucidate significant risk factors of progression. CONCLUSIONS: This is the first multicenter study to investigate the incidence of OPLL progression after posterior decompression by using a standardized measurement method. The rate of postoperative progression at 2 years was 56.5%, which was comparable with results reported in other studies. Progression occurred more frequently in younger-age rather than in older-age patient populations at both 1 and 2 years postoperatively. Mixed-type and continuous-type OPLL progressed more frequently than the segmental-type lesion at 2 years. The results of the present study could serve as basis for future studies to assess the efficacy of drug therapy to prevent OPLL progression.

Adult↗

PubMed2005

Estimation of dislocation after total hip arthroplasty by 4-dimensional.

We constructed a 4-dimensional musculoskeletal model for patients who have undergone total hip arthroplasty (THA), which aimed to simulate the movement of the patient's inner body structure and estimate the complications that can arise with THA. The model reflects patient-specific characteristics of the bone geometry, implant alignment and hip movement. In order to estimate the direction of the muscle force and the length of the muscles, we developed a string-type muscle model that represents the route of the muscles. The strings expand and contract according to the movement of the origin and insertion location of the muscle. We developed models for the seven muscles related to movement of the hip joint. By using this model, clinicians will be able to predict the possibility of dislocation or recognize the actual causes of dislocation, as well as any possible influences the muscle may have on dislocation.

Arthroplasty, Replacement, Hip↗

PubMed2004

Four-dimensional model of the lower extremity after total hip arthroplasty.

We have developed a four-dimensional (4D) model of the lower extremities after total hip arthroplasty in patients. The model can aid in preventing complications such as dislocation and wearing of the sliding surface. The skeletal structure and implant alignment were obtained from CT data. We applied registration method using CAD data to estimate accurate implant alignment from scattered CT data. The reconstructed three-dimensional (3D) skeletal model was combined with motion capture data that were acquired by an optical tracking system. We displayed the patient's skeletal movement and analyzed several parameters that relate to complications. The patient's skeletal model was superimposed onto video footage that was taken by a synchronized and calibrated digital video camera. For validation of the measurement error in this system, we used open MRI to evaluate the relative movement between skin markers and bones. This system visually represents not only the 3D anatomical structure, but also 4D dynamic functions that include the time sequential transitions of components and their positions. The open MRI results indicated that the average error in hip angle was within 5 degrees for each static posture. This system enables clinicians to analyze patient's motions on the basis of individual differences. We found that our system was an effective tool in providing precise guidance of daily postoperative motions that was individualized for each patient. This system will be applicable for surgical planning, assessment of postoperative activities, and the development of new surgical techniques, materials, and prosthetic designs.

Adolescent↗

PubMed2004

Surface-based registration accuracy of CT-based image-guided spine surgery.

Registration is a critical and important process in maintaining the accuracy of CT-based image-guided surgery. The aim of this study was to evaluate the effects of the area of intraoperative data sampling and number of sampling points on the accuracy of surface-based registration in a CT-based spinal-navigation system, using an optical three-dimensional localizer. A cadaveric dry-bone phantom of the lumbar spine was used. To evaluate registration accuracy, three alumina ceramic balls were attached to the anterior and lateral aspects of the vertebral body. CT images of the phantom were obtained (1-mm slice thickness, at1-mm intervals) using a helical CT scanner. Twenty surface points were digitized from five zones defined on the basis of anatomical classification on the posterior aspects of the target vertebra. A total of 20 sets of sampling data were obtained. Evaluation of registration accuracy accounted for positional and rotational errors. Of the five zones, the area that was the largest and easiest to expose surgically and to digitize surface points was the lamina. The lamina was defined as standard zone. On this zone, the effect of the number of sampling points on the positional and rotational accuracy of registration was evaluated. And the effects of the additional area selected for intraoperative data sampling on the registration accuracy were evaluated. Using 20 surface points on the posterior side of the lamina, positional error was 0.96 mm +/- 0.24 mm root-mean-square (RMS) and rotational error was 0.91 degrees +/- 0.38 degrees RMS. The use of 20 surface points on the lamina usually allows surgeons to carry out sufficiently accurate registration to conduct computer-aided spine surgery. In the case of severe spondylosis, however, it might be difficult to digitize the surface points from the lamina, due to a hypertrophic facet joint or the deformity of the lamina and noisy sampling data. In such cases, registration accuracy can be improved by combining use of the 20 surface points on the lamina with surface points on other zones, such as on the both sides of the spinous process.

Analysis of Variance↗

PubMed2004

Management of cervical spinal lesions in rheumatoid arthritis.

We review the management of cervical spinal lesions in rheumatoid arthritis. Surgical treatment for cervical lesions presents several potential problems, such as spinal cord injury during surgery, prolonged and painful postoperative immobilization, poor outcome incompatible with surgical invasiveness, and a high failure rate of arthrodesis. The introduction of spinal instrumentation techniques to surgery for cervical lesions has solved some of these problems. Rigid spinal fixation using screws, rods, and wires has made surgery more reliable, and has freed patients from painful postoperative immobilization methods such as the Halo vest. However, the effects of surgical treatment have not been clearly examined using methods of evidence-based medicine. There is a need for clinical studies of treatment for cervical lesions, in order to help establish better methods for the management of cervical spinal lesions.

Journal Article↗

PubMed2004

Fibroblast growth factor-2 promotes the repair of partial thickness defects of articular cartilage in immature rabbits but not in mature rabbits.

OBJECTIVE: To investigate cartilage response to fibroblast growth factor-2 (FGF-2) with increasing age in vivo, we examined the effect of FGF-2 on partial thickness defects of immature and mature rabbits. DESIGN: Sixty-nine Japanese white rabbits (34 immature rabbits, 35 mature rabbits) were examined. We made experimental partial thickness defects in articular cartilage of the knees. Then, we injected FGF-2 into the knees eight times, immediately after surgery and every 2 days for 2 weeks. A single dose of FGF-2 was 10 ng/0.1 ml or 100 ng/0.1 ml. In the control group, 0.1 ml saline was injected on the same time schedule. The rabbits were sacrificed at intervals following surgery that ranged from 2 to 48 weeks. The specimens were stained with toluidine blue and examined microscopically. We used a modified semiquantitative scale for evaluating the histological appearance of repair. RESULTS: In immature rabbits, the cartilage repair in the FGF-2 (100 ng)-treated group was significantly better than that of the other groups. The defects were almost completely repaired with chondrocytes that showed a round to polygonal morphology, and large amounts of extracellular matrix with intense metachromatic staining. In mature rabbits, however, there was apparently no effect from FGF-2 in either group. CONCLUSIONS: Application of FGF-2 facilitated cartilage repair in partial thickness defects in immature rabbits, but not in mature ones.

Aging↗

PubMed2004

A novel system of four-dimensional motion analysis after total hip arthroplasty.

We have developed a novel system of four-dimensional motion analysis after total hip arthroplasty (THA) that can aid in preventing dislocation by assessing safe range of motion for patients in several daily activities. This system uses skeletal structure data from CT and motion capture data from an infrared position sensor. A 3-D model reconstructed from CT data is combined with the motion capture data. Using this system, we analyzed hip motion when getting up from and sitting down in a chair or picking up an object while sitting in a chair in 17 patients (26 hips) who underwent THA. To assess the accuracy of this system's measurements, open MRI was used to evaluate positions of skin markers against bones in five healthy volunteers in various postures. No impingement between bones and/or implants was found in any subjects during any activities. However, mean angle at the point of maximum hip flexion was different for each patient. The open MRI results indicated that average error in hip angle of the present system was within 5 degrees for each static posture. The functional position of the pelvis during daily activities must be taken into account when assessing the real risk of dislocation. The present system enables dynamic analysis involving not only alignment of components and bones of each patient, but also individual differences in characteristics of daily motions. Further investigation using this system can help determine safe ranges of motion for preventing hip dislocation, improving the accuracy of individualized guidance for patients regarding postoperative activities.

Adolescent↗