Measurement of dynamic bite force during mastication.

Efficient mastication of different types and size of food depends on fast integration of sensory information from mechanoreceptors and central control mechanisms of jaw movements and applied bite force. The neural basis underlying mastication has been studied for decades but little progress in understanding the dynamics of bite force has been made mainly due to technical limitations of bite force recorders. The aims of this study were to develop a new intraoral bite force recorder which would allow the study of natural mastication without an increase in the occlusal vertical dimension and subsequently to analyze the relation between electromyographic (EMG) activity of jaw-closing muscles, jaw movements and bite force during mastication of five different types of food. Customized force recorders based on strain gauge sensors were fitted to the upper and lower molar teeth on the preferred chewing side in fourteen healthy and dentate subjects (21-39 years), and recordings were carried out during voluntary mastication of five different kinds of food. Intraoral force recordings were successively obtained from all subjects. anova showed that impulse of bite force as well as integrated EMG was significantly influenced by food (P<0·05), while time-related parameters were significantly affected by chewing cycles (P<0·001). This study demonstrates that intraoral force recordings are feasible and can provide new information on the dynamics of human mastication with direct implications for oral rehabilitation. We also propose that the control of bite force during mastication is achieved by anticipatory adjustment and encoding of bolus characteristics.

Physical fitness and cognitive function in an 85-year-old community-dwelling population.

BACKGROUND: Little is known about the association between physical fitness and cognitive function in very elderly people (over 80 years of age). OBJECTIVES: To evaluate that relationship in 85-year-old community-dwelling individuals. METHODS: Out of 207 participants (90 males, 117 females) who were 85 years old and community-dwelling, 205 completed the Mini-Mental State Examination (MMSE) for evaluating cognitive function. The numbers of subjects who completed physical fitness measurements such as hand-grip strength, isometric leg extensor strength, one-leg standing time, stepping rate, and walking speed were 198, 159, 169, 168, and 151, respectively. RESULTS: There were significant associations in MMSE with hand-grip strength (right or left hand), isometric leg extensor strength, stepping rate, and walking speed by simple regression analysis. MMSE was still significantly associated with hand-grip strength (beta = 0.305, p = 0.005 for right side; beta = 0.309, p = 0.004 for left side), stepping rate (beta = 0.183, p = 0.046), and walking speed (beta = -0.222, p = 0.014) by multiple regression analysis after adjustments for the amount of education, gender, smoking, drinking, complication of stroke, body weight, body height, regular medical care, serum albumin, blood HbA1c, and marital status. By logistic regression analysis, the prevalence of a normal MMSE score (MMSE >or=24) was increased by 9% with each 1-kg increase in hand-grip strength of the left hand (OR 1.087, 95% CI 1.003-1.179, p = 0.042), and was increased by 6% with each step per 10 s in stepping rate (OR 1.060, 95% CI 1.000-1.122, p = 0.048). CONCLUSION: In a very elderly population of 85-year-olds, cognitive function was associated with some physical fitness measurements, independent of confounding factors.

Three-dimensional finite element analysis of unicompartmental knee arthroplasty--the influence of tibial component inclination.

Aseptic loosening and failure of a tibial component are recognized problems in unicompartmental knee arthroplasty (UKA). Excessive stress on the supporting cancellous bone is thought to contribute to the loosening and failure. Of factors that could influence supporting cancellous bone stresses, we focused on the inclination of a unicompartmental tibial component by analyzing the effect of coronal plane and sagittal plane inclination. Detailed geometrically accurate, three-dimensional finite element models were constructed from computed tomography (CT) data of a typical adult male proximal tibia. The material properties for the models were obtained directly from the CT data to simulate the inhomogeneous distribution of cancellous bone properties. Placing the component in slight valgus inclination in the coronal plane reduced the cancellous bone stresses. Posterior inclination in the sagittal plane caused a moderate increase in the stresses. Our results suggest that slight valgus inclination of a UKA tibial component may be preferable to varus or square inclination in the coronal plane. An excessive posterior slope of a tibial component should be avoided.

Does the self-centering mechanism of bipolar hip endoprosthesis really work in vivo?

PURPOSES: To examine radiographically the component motion in a bipolar prosthesis and to determine whether the self-centering mechanism really works in vivo. METHODS: 38 patients with 41 bipolar hip endoprostheses (30 for coxarthrosis and 11 for osteonecrosis of femoral head) were included in this study. Two radiographs of each case were taken to evaluate the self-centering mechanism. The first anteroposterior radiograph of both hip joints was taken at the maximum abduction while the patient standing on the endoprosthetic leg. The second radiograph was taken after the patient returned to neutral position while standing on 2 legs. In the present study, the order in which the radiographs were taken differed from previously reported studies. The radiographs were analysed using the method similar to that of Drinker and Murray. The adductive motion from abduction to a neutral position is within the range of inner bearing oscillation. RESULTS: The outer head alignment changed from 23 degrees to 12 degrees in the patients with osteonecrosis. However, the valgus position of the outer head (36 degrees) remained unchanged in the patients with coxarthrosis standing on 2 legs in the neutral position. CONCLUSION: The self-centering mechanism of the bipolar endoprosthesis functioned in the patients with osteonecrosis, but did not work in the coxarthrosis group.

Debridement and continuous irrigation for the treatment of pyogenic arthritis caused by the use of intra-articular injection in the osteoarthritic knee: indications and outcomes.

PURPOSE: To discuss the indications and therapeutic outcomes of synovectomy, debridement, and continuous irrigation for the treatment of pyogenic arthritis caused by intra-articular injection used in the treatment of osteoarthritis of the knee. METHODS: Records of 41 patients with infectious arthritis of the knee who presented to our hospital from 1981 were reviewed. 11 of them had a history of intra-articular injection. They underwent synovectomy, debridement, and continuous irrigation using a Salem double-lumen tube after confirmation that one side of the femorotibial joint cartilage was basically healthy. RESULTS: The infection was successfully treated in 9 of the 11 patients. Of these 9 patients, one died after 3 years and 2 underwent total knee arthroplasty after 3 and 8 years. The remaining 6 patients were followed up for 5 to 15 years. Five of them had deteriorating arthropathy, and the condition was unchanged in the others. Two of these 6 patients had pain while walking, and their Japanese Orthopaedic Association scores were 70. The remaining 4 had good knee function and reduction of pain, with a mean Japanese Orthopaedic Association score of 91 and a mean range of motion of 131 degrees. CONCLUSION: Arthrodesis is frequently considered the treatment for osteoarthritis if the joint destruction has affected the weight-bearing surface. However, in our experience, even when inflammatory granulation develops in the cartilage surface of one side of the femorotibial joint, good results can still be obtained by synovectomy, debridement, and continuous irrigation. After the pyogenic arthritis has subsided, if osteoarthritis has advanced and bowleg has exacerbated, further treatment options are available, such as tibial resection and even joint replacement. Continuous irrigation should be considered a feasible treatment option for pyogenic arthritis.

The effect of macrophage-colony stimulating factor and other humoral factors (interleukin-1, -3, -6, and -11, tumor necrosis factor-alpha, and granulocyte macrophage-colony stimulating factor) on human osteoclast formation from circulating cells.

Macrophage-colony stimulating factor (M-CSF) is an essential requirement for human osteoclast formation, but its effect on the proliferation and differentiation of circulating osteoclast precursor cells is unknown. Other growth factors and cytokines are also known to support/stimulate osteoclast formation from mouse marrow precursors, but it is not certain whether these factors similarly influence human osteoclast formation. In this study, human monocytes were cocultured with osteoblast-like UMR-106 cells on coverslips and dentine slices for up to 21 days in the presence of 1,25 dihydroxyvitamin D(3) (10(-7) mol/L), dexamethasone (10(-8) mol/L), and various concentrations of either M-CSF or other humoral factors (interleukin [IL]-1beta, IL-3, IL-6, and IL-11; tumor necrosis factor-alpha [TNF-alpha]; and granulocyte macrophage [GM]-CSF). The effect on osteoclast formation was assessed by tartrate-resistant acid phosphatase (TRAP) and vitronectin receptor staining and lacunar bone resorption. The results of time-course and proliferation studies showed that M-CSF stimulated both the proliferative and differentiation stages of human osteoclast formation from circulating osteoclast precursors in a dose-dependent manner. A high concentration of M-CSF (100 ng/mL) did not inhibit osteoclast formation. IL-3 and GM-CSF were also capable of stimulating human osteoclast formation, although these growth factors were much less potent than M-CSF. IL-3- and GM-CSF-stimulated osteoclast formation was inhibited by an antibody specific for human M-CSF. Osteoclast formation and lacunar resorption was not seen when either TNF-alpha, IL-1beta, IL-6 (+ soluble IL-6 receptor), or IL-11 was substituted for M-CSF during coculture. These results confirm that M-CSF is essential for human osteoclast formation from circulating mononuclear precursors, and also shows that IL-3 and GM-CSF may support osteoclast differentiation via the stimulation of M-CSF production by human monocytes.

Bone and joint lesions in decompression sickness.

1 Of 450 divers, 268 (59.5%) has aseptic necrosis of bone; 81 had articular lesions. 2 In proportion to duration of diving experience and maximum depth of diving, incidence of bone necrosis increases. 3 The radiological lesions have been classified by modified Ohta-Matsunaga criteria. 4 Yearly progress of bone changes were mentioned. 5 Pathological appearances of aseptic necrosis of bone in divers are compared with different types of bone necrosis. 6 Experimental studies for aseptic necrosis were mentioned. 7 Etiology of bone necrosis is not yet clear, but some etiological factors were discussed. It was suggested that fat embolism was an important factor, because fat embolisms were seen in our pathological findings of the divers and compressed-air workers. 8 Periodic radiological examination of the bones of divers and compressed-air workers should be carried out. It is important to research the new modified decompression table to prevent bone necrosis. 9 Surgical treatment of bone necrosis was mentioned.

Isolated avulsion fracture of the tibial attachment of the posterior cruciate ligament.

Twenty-one patients with isolated avulsion fracture of the tibial attachment of the posterior cruciate ligament were treated in our hospital during the period 1965 to 1976. Twelve of the patients had fresh injuries and nine, injuries with delayed union or non-union. Twelve of the twenty-one patients were treated conservatively and nine, by surgical repair by means of staple fixation. Detachment of the posterior horn of the meniscus with an avulsed and displaced bone fragment was found in five of the nine patients operated on. All the patients were followed for an average of four years and eight months. Satisfactory results were obtained in every instance.

The effects of tibial component inclination on bone stress after unicompartmental knee arthroplasty.

Unlike the case with total knee arthroplasty, the femorotibial angle (FTA) after unicompartmental knee arthroplasty (UKA) does not directly depend on the inclination of the tibial component when the height of the joint line is maintained. This study analyzed the effects of the inclination of the tibial component in the coronal plane on the contact pressure of the implant-bone surface and the stresses on the proximal tibia. A two-dimensional, coronal plane model of the proximal tibia was subjected to finite-element analysis. Sixteen patterns of finite-element models of equal FTA were developed in which the inclination of tibial components ranged from 5 degrees valgus to 10 degrees varus in increments of 1 degrees. Stress concentration at the proximal medial diaphyseal cortex gradually increased as the inclination changed from valgus to varus. Maximum contact pressure on the metal-bone interface similarly changed and shifted from the lateral edge to the medial edge of the implant as the inclination changed to varus. It was found that even without changing FTA, the inclination of the tibial component might affect stress concentration and contact pressure in the proximal tibia after UKA. The results suggested that slight valgus inclination of the tibial component might be preferable to varus and even to 0 degrees (square) inclination so far as the stress distribution is concerned.

Atlantoaxial subluxation associated with ossification of posterior longitudinal ligament of the cervical spine.

STUDY DESIGN: Two case reports. OBJECTIVE: To demonstrate two rare cases of atlantoaxial subluxation associated with ossification of the posterior longitudinal ligament of the cervical spine, in which spastic quadriplegia developed. SUMMARY OF BACKGROUND DATA: There are only two reports of an association of diffuse idiopathic skeletal hyperostosis with atlantoaxial subluxation. This condition often accompanies ossification of the posterior longitudinal ligament of the cervical spine, but there is nothing in the literature about the association of ossification of the posterior longitudinal ligament with atlantoaxial subluxation. METHODS: Clinical and radiographic findings of these two cases were demonstrated. In both cases laminoplasty of the cervical spine was performed with occipitoaxial arthrodesis. RESULTS: The spastic quadriplegia of these two patients caused by myelocompression improved after surgical intervention. CONCLUSION: Ossification of the posterior longitudinal ligament of the cervical spine may cause atlantoaxial subluxation.

Muscle belly tear of the triceps.

Triceps injury at the tendo-osseous junction of the olecranon is not uncommon, but a muscle belly tear of the triceps is extremely rare. Two cases of muscle belly tears of triceps are reported. One case was treated surgically and the other conservatively.

3M integral bipolar cup system for dysplastic osteoarthritis. Clinical and radiographic review with five- to seven-year follow-up.

Between 1995 and 1997 we undertook 40 bipolar hip arthroplasties in 35 patients with dysplastic osteoarthritis. The steep and shallow acetabulum was excavated and the bipolar socket was placed high with an adjustment of leg-length. At follow-up of between five and seven years, there were 19 excellent, 16 good and five fair results according to the scoring system of Merle d'Aubigné and Postel. The mean radiographic superior migration of the bipolar socket was 2.1 mm (0 to 10). Osteolysis was noted in three hips within three years of the operation. Abduction on weight-bearing was recorded in 24 hips and the bipolar system was found to be functioning predominantly between the inner bearing and the metal femoral head in 20.

Iliopsoas bursa of the rheumatoid hip joint. A case report and review of the literature.

Presented is the case of a 63-year-old woman, with a 30-year history of rheumatoid arthritis, whose hip was completely destroyed and accompanied with enlargement of the iliopsoas bursa. Preoperative diagnosis was confirmed by computed tomography, magnetic resonance (MR) imaging and arthrography. She was treated by resection of the iliopsoas bursa and total prosthetic replacement of the hip joint. The pathogenesis is uncertain. In the literature, enlargement of the iliopsoas bursa with rheumatoid arthritis, osteoarthritis, pigmented villonodular synovitis, and synovial chondromatosis had been reported. Nevertheless, a correct preoperative diagnosis of the enlargement of the iliopsoas bursa is very difficult. MR imaging with enhanced Gadolinium-DTPA (Gd-DTPA) is proposed as the most useful examination for preoperative diagnosis.

An assessment of histopathological criteria for infection in joint arthroplasty in rheumatoid synovium.

Intraoperative frozen section is reported to be a reliable means of identifying occult infection for preoperative evaluation of arthroplasty. The aim of this study was to determine whether the reported histopathological criteria--the existence of more than 10 polymorphonuclear cells (PMN) per high-power field--is valuable for determination of infection during the arthroplasty of patients with rheumatoid arthritis (RA). The permanent histological sections of RA synovium were analysed to study the degree of infiltration of PMNs. Furthermore, in order to examine the penetrative distribution of PMNs within the synovial tissues, immunohistochemical staining of PMNs was performed. In addition, the clinical history, from the postoperative period to the present, was investigated in 46 patients (60 joints). The presence of early- and/or late-stage postoperative infection, the development of postoperative fever, the progression of erythrocyte sedimentation rate (ESR) (more than 30 mm per hour) and the changes in CRP (more than 10 mg per litre) were further examined and compared with the histopathological tissue analyses and findings. The results demonstrated the presence of more than five PMNs per high-power field, excluding surface fibrin and inflammatory exudate in at least five separate microscopic fields in 10 joints (16.7%) of nine patients, out of 60 joints of 46 patients, in which no postoperative infection was evident. As to the magnitude of penetrative distribution of PMNs in 10 joints, there was a trend of deepening infiltration among the patients with intensive PMN infiltration. In addition, no development of postoperative fever, CRP or continuous indications of high ESR values were evident in this group. As the existence of more than 10 PMN per high-power field was not absolutely indicative of occult infection, investigation of frozen section during arthroplasty should be carefully managed.

[Study on tobramycin concentration in bone marrow (author's transl)].

Tobramycin (TOB) concentration in the bone marrow of tibia was examined 1, 2, 3 and 4 hours after intramuscular injection of 60 mg: TOB concentration in the bone marrow of tibia 1 hour after injection was 2.8 +/- 0.578 microgram/ml. Ratio to serum was 87.5%. TOB concentration in the bone marrow of tibia 2 hours after injection was 1.6 +/- 0.480 microgram/ml. Ratio to serum was 94.1%. TOB concentration in the bone marrow of tibia 3 hours after injection was 1.1 +/- 0.337 microgram/ml. Ratio to serum was 84.6%. TOB concentration in the bone marrow of tibia 4 hours after injection was 0.8 +/- 0.372 microgram/ml. Ratio to serum was 80.0%. Penetration capacity of TOB into the bone marrow of tibia was excellent.