Joint kinesthesia in the highly trained knee.
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Dancing↗
Biomedical subjects
S D Cook
Publications and source records attributed to S D Cook.
Retrieval and analysis of intramedullary rods. A follow-up study.
From 1980 to 1983, 16 AO intramedullary femoral rods were retrieved and analyzed clinically, radiographically, and metallurgically. Cracking and/or fracture was observed in four of the 16 specimens. All cracks occurred at the point of maximum stress at the end of the slot. In two cases a structurally weaker weld zone coincided with this location. The weld zone and slot were also found to coincide in five of the uncracked rods. Two of the four cracked rods were removed because of pain, while only three of the 12 uncracked rods caused pain. Structural and material characteristics (i.e., the location of the weld at a point of maximum stress and significant variability in microstructure), rather than surgical technique or time in situ, were found to be responsible for the implant mechanical failures. Improvements should be made in fabrication techniques and material properties. For the present, careful assessment of a painful intramedullary rod and routine removal after healing are advisable.
Femoral Fractures↗
[Trial of a porous chromium-cobalt-molybdenum blade implant].
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Animals↗
Age-related decline in proprioception.
Joint-position sense of the knee was measured in 29 subjects with normal knee joints ranging in age from 20 to 82 years. Joint-position sense was determined by two common techniques that measure the threshold to detection of motion and the ability to reproduce passive knee positioning. Joint-position sense was found to deteriorate with increasing age as measured by both tests, with a correlation coefficient that was significant at the p less than 0.001 level for each test. The two tests were found to correlate at the p less than 0.025 level, indicating that the same biologic parameter was being measured by both tests. Deterioration of proprioception, or joint-position sense, as measured may be a sensitive indicator of subclinical degenerative joint disease of the knee, as well as a means of quantitating proprioception in suspected neuropathic joints.
Adult↗
Household pets among veterans with multiple sclerosis and age-matched controls. Pilot survey.
A pilot study was carried out among 22 Vietnam-era male US veterans with multiple sclerosis (MS) and 55 age- and sex-matched controls for prior exposure to dogs, cats, and animals with a distemperlike illness. No difference in dog ownership, or sick animals, and subsequent human illness was found in the group with MS or the control group. However, the distribution of dogs by indoor-outdoor status, as reported by patients with MS or controls, showed significant variation by tier of residence. Indoor dogs were more common in northern than southern latitudes, and this may be an important finding in light of the variation in the risk of MS with latitude.
Adult↗
Hepatitis A virus immunoglobulin M antibody in acute neurological disease.
Sera from 167 patients with Guillain-Barré syndrome, 224 patients with other neurological diseases, and 10 normal subjects were tested for hepatitis A virus-specific immunoglobulin M antibodies. Two patients with classic Guillain-Barré syndrome and 1 patient with acute myeloradiculopathy had high titers of virus-specific IgM antibody. All three patients had jaundice and laboratory evidence of liver involvement before the onset of the neurological disease. None of the other sera from patients with Guillain-Barré syndrome or control subjects were positive for hepatitis A virus.
Adult↗
Quantitative histologic evaluation of LTI carbon, carbon-coated aluminum oxide and uncoated aluminum oxide dental implants.
The response of mandibular bone to identical geometry LTI carbon, carbon-coated aluminum oxide, and uncoated aluminum oxide blade-type dental implants in baboons for 2 years was evaluated using histologic, microradiographic, and scanning electron microscopic methods. In addition, a quantitative histologic analysis was performed identifying the type, amount, and distribution of tissue surrounding the dental implant systems. This is the final phase of a study investigating the effect of implant elastic modulus and implant surface chemical composition on the performance of dental implants. Previous studies have utilized clinical and radiographic evaluations, postretrieval mechanical testing, and finite element stress analysis to evaluate the dental implant performance. The results of the histologic study revealed a direct implant-bone interface with no intervening soft tissue in 16 of the 21 implants (76%). A fibrous tissue interface was observed in 5 of 21 implants (24%). Quantitative histologic results for the implants with a direct implant-bone interface showed statistically larger crestal cortical plates (p less than 0.05) and greater area fraction crestal cancellous bone (p less than 0.05) in the LTI carbon implant compared to the carbon-coated and uncoated aluminum oxide implants. The carbon-coated and uncoated aluminum oxide implants demonstrated statistically greater area fraction cancellous bone at the inferior region of the implant (p less than 0.05) and thinned and reduced crestal cortical plates when compared to the LTI carbon implants. The results indicate that significant stress shielding of the crestal bone had occurred with the rigid carbon-coated and uncoated aluminum oxide implants when compared to the LTI carbon implants which had a material elastic modulus similar to cortical bone. Based upon the histologic results, it appears that the LTI carbon implants with the direct implant-bone interface exhibited a greater potential for long-term successful performance compared to the aluminum oxide substrate implants.
Aluminum↗
The retention mechanics of LTI carbon, carbon-coated aluminum oxide, and uncoated aluminum oxide dental implants.
The in vitro mechanical behavior of identical geometry LTI carbon, carbon-coated aluminum oxide, and uncoated aluminum oxide blade-type dental implants has been evaluated using rosette type strain gauges and a LVDT system. The implants served as a distal abutment for a three-unit fixed prosthesis and functioned for a period of 2 years in female baboons. The comparison of the LTI carbon implants to the carbon-coated aluminum oxide implants allowed for a study of the effect of implant elastic modulus on the mechanical behavior, while the comparison of the carbon-coated and uncoated aluminum oxide implants allowed for a study of the effect of chemical composition at the tissue-implant interface. The results of the mechanical testing indicate that the implant displacement response of the LTI carbon implants was greater than that of the carbon-coated and uncoated aluminum oxide implants. Little difference in displacement response was observed for the carbon-coated and uncoated aluminum oxide implants. No clear trend in the strain response of the buccal mandibular bone was observed for the three implant systems. The greatest differences in strain response, however, was observed between the uncoated aluminum oxide implants and the LTI carbon and carbon-coated aluminum oxide implants.
Aluminum Oxide↗
Ambulatory function in total knee arthroplasty.
Through the use of gait analysis, this study attempts to characterize gait after total knee arthroplasty as a function of postoperative time to quantify the effectiveness of the surgery and to evaluate prostheses of several different designs. Gait analysis on 32 preoperative and 50 postoperative patients included measurement of velocity, cadence, stride length, and gait cycle. Postoperative data were collected at various intervals from 0.7 to 111 months after knee surgery (average postoperative time, 45.3 months). Linear regression analysis of velocity, cadence, stride length, gait cycle, and the ratio of contralateral to pathologic single limb support time as a function of postoperative time are reported with statistical error limits. Extrapolation of these results to zero postoperative time indicates that the patients who had had total knee arthroplasty had a slight improvement in all gait parameters compared to the preoperative control group. This was not statistically significant, however, except for cadence (P less than .05). Although velocity and stride length increased slightly toward more normal values with increased postoperative time, gait parameters at no time approached normal values.
Adult↗
A biomechanical analysis of the etiology of tibia vara.
To elucidate the cause of tibia vara, finite element analysis of the proximal tibia was used to investigate the stresses occurring in the physeal plate during one-legged stance in 2- and 5-year-old children. A modification of the method of Kettlekamp and Chao was used to assign forces to the medial and lateral plateaus and lateral ligament. Stresses were calculated in the physeal plate for the two age groups as a function of degree of varus and body weight. Our results show that increasing varus resulted in increasing compressive stress in the medial tibial physis to a level seven times normal at 30 degrees of varus. Further, tensile stresses determined in the lateral tibial physis were increased above normal. Changes were more marked in the obese child and in the 5 year old. Using the data from Strobino et al. it appears that in the 2 year old 20 degrees of varus resulted in forces sufficient to retard growth. In the 5 year old, however, 10 degrees of varus resulted in borderline forces in a child of normal weight, but forces exceeding those necessary to retard physeal growth were calculated in the model of the obese child. Our data are consistent with the hypothesis that Blount's disease is primarily the result of the proximal tibial epiphysis responding to physical phenomena.
Biomechanical Phenomena↗
Effect of articular disease and total knee arthroplasty on knee joint-position sense.
Joint proprioception in the human knee has been studied using two previously described tests. Threshold of detection of slow, constant, passive motion and ability to reproduce angles to which the knee was passively placed were accurately measured. A group of postoperative total knee arthroplasty (TKA) patients were examined. All patients also had documented articular disease in the unoperated knee. Results were compared to age-matched controls. In addition, a young control group was studied for comparison to both groups. A significant difference was seen between the young control group and the older control group in both tests performed. Age-matched controls and the postoperative patients demonstrated an even greater difference. There was, however, no difference between the operated and unoperated knee among the TKA patients. It is concluded that joint proprioception declines to some degree with normal aging. A more marked decline is associated with degenerative joint disease. Total joint replacement, however, did not lead to a further decrease in sensation.
Age Factors↗
Radiographic and histologic evaluation of intramedullary implants intended for biological fixation.
Three mechanisms of direct biological attachment of implants to bone were examined using femoral intramedullary implants. The implant systems studied were; low temperature isotropic (LTI) pyrolytic carbon, carbon coated porous Co-Cr-Mo alloy and 45S5 bioglass coated Co-Cr-Mo alloy. A detailed radiographic examination revealed that all three implant systems caused significant remodeling of the femurs resulting in an hour-glass appearance. The implants were also associated with a densification of cancellous bone proximal and distal to the ends of the implant. Histologically, all three implant systems exhibited a direct bone-implant bond at the majority of the interfaces. The LTI pyrolytic carbon implants were associated with a higher incidence of fibrous tissue encasement in the proximal cancellous bone region. Active bone remodeling was observed within the pores of the porous Co-Cr-Mo alloy implants even after 8 months in situ.
Alloys↗
Femoral head stresses following cortical bone grafting for aseptic necrosis. A finite element study.
A two-dimensional finite element model was used to compare the femoral head stress distribution of an intact femur with that of a femur following core biopsy and biopsy with cortical grafting. There was a decrease in superior and lateral femoral head stresses of up to 50% by an incorporated and properly placed cortical graft. Core biopsy and cortical grafting short of the subchondral plate produced stress-concentrating effects. A medially placed cortical graft did not stress-relieve the superolateral femoral head. Thus, if cortical grafting is to be undertaken, the graft should extend from the lateral cortex to the subchondral plate, transfixing the length of the necrotic segment. Because of deleterious effects on femoral head stress distribution, core biopsy without cortical grafting should be discouraged or only very cautiously used.
Bone Transplantation↗
A quantitative histologic study of osteoporosis produced by nutritional secondary hyperparathyroidism in dogs.
Nutritional secondary hyperparathyroidism (NSH) was induced in adult beagle dogs through nutritional control by a diet high in phosphorus (1.20%) and low in calcium (0.12%). A control group was fed a diet containing 0.42% phosphorus and 0.54% calcium. A statistically significant increase in iPTH level was observed at ten and 20 weeks. The femoral heads of experimental (NSH) animals showed increased osteoclastic activity and an approximately 20%-30% reduction in volume fraction cancellous bone. No abnormal osteoid seam was found in the cancellous bone of the experimental animals, and no statistically significant differences were observed in either the calcium-to-phosphorus or mineral-to-matrix ratios of the bone tissue for the two groups. Data obtained from histologic sections on the number of trabecular bone intercepts per unit length and thickness of trabeculae in the femoral head indicated a uniform, rather than specific loss of bone mass in the experimental sections. Histologic sections from the proximal femoral shaft revealed increased endosteal and periosteal diameters in the experimental group compared with the control group.
Animals↗
Bilateral sequential tibial and fibular fatigue fractures associated with aluminum intoxication osteomalacia. A case report.
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Aluminum↗
Distemper and multiple sclerosis in Sitka, Alaska.
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Adult↗
The influence of implant geometry on the stress distribution around dental implants.
A three-dimensional finite element stress analysis has been used to investigate the influence that variations in the infrastructural geometry of a blade-type dental implant have on the stress distribution around LTI carbon and aluminum oxide implants. The finite element model was constructed based upon an analysis of serial sections of a retrieved implant specimen. In addition to the implant, the finite element model contained a three-unit fixed bridge connected to a natural molar with periodontal membrane. The removal of the bridge allowed for the study of freestanding implants and molar. Variations of the implant blade geometry were found to produce significant changes in the stress distributions around bridged and freestanding aluminum oxide implants. Very little effect, however, was observed around the LTI carbon implants. A comparison of the stresses around the freestanding molar and the stresses around the bridged and freestanding implants was made to determine the implant design that came closest to reproducing the stress state around the modeled molar. The LTI carbon system that best achieved this stress state was found to be a full-blade implant used in conjunction with a tooth as an abutment in a fixed bridge. The aluminum oxide system that best achieved this stress state was found to be of the post or short-blade design used as a freestanding implant.
Aluminum Oxide↗
Parameters affecting the stress distribution around LTI carbon and aluminum oxide dental implants.
Three-dimensional finite element stress analysis was used to study the effects that implant neck geometry and the tissue properties at the implant-bone interface have on the stress distribution around free-standing blade- and post-type LTI carbon and aluminum oxide dental implants. Implants having neck flares of 13 degrees and 26 degrees were studied. In addition, to simulate fibrous encapsulation of the implant as opposed to a direct bone apposition retention mechanism, a soft tissue interposing layer between implant and bone was also modeled. The results of the study indicate that a reduction in neck flare from 26 degrees to 13 degrees was a positive design change for blade- and post-type LTI carbon implants and blade-type aluminum oxide implant but not for post-type aluminum oxide implant. The results of the study indicate the presence of fibrous tissue surrounding the implants may be indicative of a failing system and may be the result of either hypophysiological stress (aluminum oxide implants) or hyperphysiological stress (LTI carbon implants).
Aluminum↗