The lithotriptor and its potential use in the revision of total hip arthroplasty.
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Animals↗
Biomedical subjects
F P Magee
Publications and source records attributed to F P Magee.
Influence of marrow on ultrasonic velocity and attenuation in bovine trabecular bone.
Measurements of ultrasonic velocity and specific differential attenuation (SDA) were obtained on 24 bovine trabecular bone specimens from the femoral condyles. The measurements were obtained using two pairs of ultrasonic transducers, one with a low nominal center frequency (500 kHz) and the other pair with a high nominal center frequency (1 MHz). The ultrasonic velocity and specific differential attenuation associated with the bone samples were determined both with and without marrow, i.e., replacing the marrow with water in the pores of the trabecular bone. Significant increases (2.1% and 2.9%) in the velocity of ultrasound were observed after removal of the marrow, for the low and high frequency transducer pairs, respectively. In contrast, significant decreases (-6.5% and -8.8%) in SDA were observed after removal of the marrow, for the low and high frequency transducer pairs, respectively. The bone densities (BD) of the samples were also determined using single photon absorptiometry (SPA). Correlations between ultrasonic parameters and bone densities for samples both with and without marrow were found to be similar. For example, for the 1 MHz transducer pair, the correlation between BD and velocity was r = 0. 86 with marrow, and r = 0.89 without marrow. This study also compared the results obtained using a contact (no water bath) technique and an insertion (with a water bath) technique of ultrasonic measurements. For the high frequency transducer pair, the correlation coefficients between the two methods were r = 0.99 and r = 0.93, for the velocity and specific differential attenuation, respectively. Similar results were found for the low frequency transducer pair as well. In addition, approximately equal correlations between BD and ultrasonic velocity and SDA were also found, indicating that contact and insertion measurements provide essentially equivalent information.
Absorptiometry, Photon↗
IGF-II receptor number is increased in TE-85 osteosarcoma cells by combined magnetic fields.
Human osteosarcoma-derived osteoblast-like cells, TE-85, were used to assess the effect of a low frequency alternating magnetic field in combination with a controlled static magnetic field (combined magnetic fields, CMF) on insulin-like growth factor receptor regulation. In our culture system, application of a 15.3 Hz CMF induces a calculated maximum electrical potential in the culture media of 10(-5) V/m. Initial characterization of TE-85 cells demonstrated that (a) TE-85 cells contain both type I insulin-like growth factor (IGF-I) and IGF-II receptors and (b) dose dependence for IGF-stimulated cell proliferation were comparable to the affinities of the IGF's binding to membrane binding sites (i.e., receptors had dissociation constants in the low nanomolar concentration range). The studies with CMF exposure revealed that CMF treatment for 30 minutes increased the number of IGF-II receptors in a frequency-dependent manner without affecting the number of IGF-I receptors. The CMF-dependent increase in IGF-II receptor number was associated with a significant increase in the IGF-II dissociation constant. These results indicate that a membrane receptor levels can be altered by short-term exposure to low-energy, low-frequency electromagnetic fields and suggest a potential biochemical mechanism for electromagnetic effects on bone formation and remodeling.
Analysis of Variance↗
Combined magnetic fields increase insulin-like growth factor-II in TE-85 human osteosarcoma bone cell cultures.
In vitro exposure to low-energy, combined magnetic fields (CMF) increased the release of insulin-like growth factor (IGF)-II from human TE-85 osteosarcoma cells. Short-term CMF exposure of only 10 min increased IGF-II levels in conditioned medium 1 h post CMF exposure. IGF-II levels were measured with a radioreceptor assay using H-35 cells that contain abundant IGF-II but not IGF-I receptors. This assay also uses a recently validated BioGel P-10 acid gel filtration method to remove IGF binding protein before quantitation of either IGF-I or IGF-II. In addition to an increase in IGF-II levels, DNA synthesis, as an index of cell proliferation, was increased during the 24-h period post CMF exposure. A monoclonal antibody against IGF-II blocked the increase in cell proliferation following CMF exposure, whereas a control monoclonal antibody against osteocalcin did not attenuate the mitogenic action of CMF exposure. The effect of CMF exposure to increase both cell proliferation and IGF-II was cell-density dependent with greater stimulation by CMF observed at lower densities. Together, these data are consistent with the hypothesis that CMF exposure stimulates release/production of IGF-II from bone cells and that increased IGF-II then promotes an increase in cell proliferation.
Cell Count↗
Combined magnetic fields increased net calcium flux in bone cells.
Low energy electromagnetic fields (EMF) exhibit a large number of biological effects. A major issue to be determined is "What is the lowest threshold of detection in which cells can respond to an EMF?" In these studies we demonstrate that a low-amplitude combined magnetic field (CMF) which induces a maximum potential gradient of 10(-5) V/m is capable of increasing net calcium flux in human osteoblast-like cells. The increase in net calcium flux was frequency dependent, with a peak in the 15.3-16.3 Hz range with an apparent bandwidth of approximately 1 Hz. A model that characterizes the thermal noise limit indicates that non-spherical cell shape, resonant type dynamics, and signal averaging may all play a role in the transduction of low-amplitude EMF effects in biological systems.
Alkaline Phosphatase↗
Radiological and histological study of aseptic loosening using a cemented tibial hemiarthroplasty in the rabbit knee.
Fourteen mature New Zealand white female rabbits had a unilateral cemented, stemmed, titanium, condylar-type tibial hemiarthroplasty, using an anteromedial arthrotomy of the right knee. The articular cartilage and minimal bone were resected. There were two prosthetic groups of seven animals each: a well-fixed, non-loose group and a loose group. In the non-loose group, the implant was inserted into the cement bed and axially compressed until the PMMA had cured. In the loose group, the same volume of cement was allowed to cure on the implant ex vivo; the prosthesis was then implanted to ensure that it was loose fitting. Radiographs were performed at zero and 3 months and graded for new lucent lines. Histological analysis was performed using undecalcified coronal sections, surface stained with toluidine blue with the prosthesis in situ, and the cement mantle preserved. Back-scattered electron microscopy was also performed. The mean cumulative grading of new lucent lines was 0.3 +/- 0.1 for the non-loose group and 2.2 +/- 0.4 for the loose group (P < 0.005). Non-loose prostheses were surrounded by a thin fibrous membrane or bone. Loose prostheses were surrounded by a thicker, fibrous tissue layer, containing histiocytes and giant cells which were more prevalent around cement particles, especially near the prosthetic tip. These findings parallel the histology found at cemented prosthetic interfaces in humans. The results of this study suggest that the fibrohistiocytic membrane commonly found around loose cemented implants may be the result of, rather than the cause of, the loosening process.
Animals↗
Recent advances in electrical stimulation.
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Animals↗
Prostaglandin E2 production by the membrane surrounding loose and fixated cemented tibial hemiarthroplasties in the rabbit knee.
Sixteen mature New Zealand female rabbits had cemented, tibial hemiarthroplasty of the right knee (correction of hip) using a stemmed, fluted, titanium-alloyed, condylar type prosthesis. In the fixated prosthetic group (eight rabbits), a 1.5-cm3 doughy bolus of polymethylmethacrylate (PMMA) was used to cement the prosthesis firmly. In the loose group (eight rabbits), the cement was allowed to cure ex vivo on the implant; the prosthesis was then implanted and rotated to ensure that it was loose fitting. Roentgenograms performed postoperatively and at three months were graded for new lucent lines. The implant area was harvested aseptically and cultured during a three-day period, and the cumulative collection of tissue culture supernatants was assayed for prostaglandin E2 (PGE2). The mean cumulative grading of new lucent lines was 0.4 +/- 0.2 (mean +/- SEM) for the fixated prosthetic group and 2.3 +/- 0.5 for the loose prosthetic group. Specimens from the nonloose group produced 8.85 +/- 1.44 ng of PGE2 on the right prosthetic side, and 17.29 +/- 3.72 ng of PGE2 on the left, nonimplanted side. Specimens from the loose prosthesis group produced 52.35 +/- 16.28 ng of PGE2 on the right prosthetic side and 17.29 +/- 3.72 ng of PGE2 on the left, nonimplanted side. Increased PGE2 production relative to fixated prostheses was noted in the membranes surrounding loose prostheses. The left, nonimplanted sides were not statistically different. Roentgenographic and biochemical evidence indicates that a cemented tibial hemiarthroplasty implanted in the rabbit knee can provide a short-term model of arthroplasty loosening.
Animals↗
The effect of low-energy combined AC and DC magnetic fields on articular cartilage metabolism.
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Animals↗
Preliminary development of a hydroxyapatite-backed strain gauge.
Long-term in vivo strain sensing would provide information about deformation changes adjacent to implants during bone remodeling. Biodegradation of the cyanoacrylate adhesive commonly used to attach strain gauges to bone has generally limited in vivo strain sensing to time periods less than one month. Hydroxyapatite (HA) which has been used to attach implants to bone in vivo, was attached to strain gauges using a solvent-thinned polysulfone solution. Three HA-polysulfone surface morphologies were tested in a preliminary bench-top test. The single layer pressed surface morphology, which responded most accurately during bench-top testing, was modified slightly and applied to two gauges which were implanted on the femur of a greyhound. Strain measurements from the HA-backed gauges in place for four months in vivo were compared to strains measured from the contralateral femur. Comparison of the results indicated these gauges were well-bonded and that they were sensing strain accurately. After embedding in PMMA, the femur having the HA-backed gauge and the control femur were sectioned at the level of one of the HA-backed gauges. Microradiographs of these sections indicated no adverse tissue response to the HA-backed gauge on the endosteal or periosteal surface.
Adhesives↗
Comparison of ultrasonically applied vs. intra-articular injected hydrocortisone levels in canine knees.
Phonophoresis of hydrocortisone is a commonly performed treatment for a wide variety of soft-tissue as well as intra-articular musculoskeletal disorders. There have been no previously reported studies indicating the degree of hydrocortisone penetration into joints achieved by means of phonophoresis. Twenty-four purebred greyhounds were used to compare intra-articular levels of hydrocortisone resulting from intra-articular injection, phonophoresis, and external application of hydrocortisone. A total of 40 samples from canine knees were analyzed by means of fluorescence polarization. Intra-articular hydrocortisone levels obtained with phonophoresis were extremely low in comparison with those obtained with intra-articular injection. There were no statistically significant differences in intra-articular hydrocortisone levels between the phonophoresis and external application treatments, or between either of these and placebo control measurements taken from knees of untreated dogs and from shoulders of treated dogs. It appears that phonophoresis is an ineffective method of obtaining hydrocortisone penetration into a joint in the canine model.
Animals↗
A long-term in vivo bone strain measurement device.
Bone remodeling resulting from implant insertion has been attributed to changes in the bone's strain state. Since remodeling takes several months, it was this study's purpose to develop a long-term in vivo strain sensor. Porous surfaced metal tabs were attached to a standard strain gauge. Two standard gauges and the porous tabbed gauge were attached to one femur and three standard gauges to the contralateral femur of a greyhound. Tissue ingrowth provided an attachment mechanism for the porous tabbed gauge in vivo. Gauge measurements were compared to those from the standard gauges. Post sacrifice testing allowed further comparisons. After histological preparation the femoral section shapes as well as the gauge locations were examined and photographed. The porous tabbed gauge remained bonded and sensed strain throughout the 8-week implantation period, while the standard gauges debonded and were unable to detect strain after 3 weeks. During testing, the measurements from the porous tabbed gauge were lower than those from the standard gauges. This was consistent with the histology which indicated that fibrous tissue had invaded the gauge's porous surface. Although the use of tissue ingrowth as an attachment mechanism seems to be worthwhile, a means of insuring bone ingrowth is necessary.
Animals↗
A canine composite femoral stem. An in vivo study.
To evaluate a carbon fiber/polysulfone composite femoral stem, a press-fit unilateral hemiarthroplasty was performed in 17 greyhounds. The implant was designed to have strength and elastic properties commensurate with the proximal canine femur. The implant geometry was such that the naturally occurring internal cancellous structures of the proximal femur would be preserved and participate in load transfer from the implant to the bone. Animals were killed at one, five, ten, 16, and 24 months. At necropsy all the femoral stems were well fixed and functioning. All implants maintained their structural integrity. Radiographs and computed tomography scans showed a constructive bone remodeling response. Histologic analysis revealed a benign host tissue response, with few inflammatory cells observed. Both bone and fibrous tissue were observed at the implant-host tissue interface. Implants fabricated from carbon/polysulfone composites have the potential for use in load-bearing applications. An implant with appropriate elastic properties provides the opportunity for the natural bone remodeling response to enhance implant stability. Naturally occurring internal cancellous structures can be utilized for load transfer by femoral components. Press-fit devices with no physical or chemical bone-bonding mechanisms can attain long-term successful functional performance.
Animals↗
Work-in-progress #1. The lithotriptor and its potential use in the revision of total hip arthroplasty.
Revision total hip arthroplasty, particularly femoral component replacement, has proved extremely difficult and has met with frequent complications. Despite a variety of devices and techniques that have been developed to facilitate removal of the femoral stem, the procedure remains difficult. Extracorporeal shock wave lithotripsy (ESWL) is a new technique initially created to pulverize renal stones by means of repetitive shock waves delivered to a discrete area. It was felt that perhaps this technique might also be utilized to facilitate the removal of the femoral component and cement from the femoral canal in revision total hip arthroplasty. Using bone cement, cadaveric canine femora were implanted with stainless steel rods placed within the medullary canal. The implanted femora were treated with ESWL, sectioned, and examined, using scanning electron microscopy. Microfracturing of the cement and a disruption of the cement/bone interface were seen in the treated specimens. ESWL has the potential to be used prior to revision total hip arthroplasty to facilitate cement and component removal, although there are several questions that need to be answered prior to considering its clinical use.
Animals↗
In vivo strain analysis of the greyhound femoral diaphysis.
Subminiature single element and rosette strain gauges used for deformation measurement were prepared for surgical implantation using a technique published previously (Szivek JA, Magee FP. J Invest Surg. 1989;2:195-206). During surgery, gauges were placed on the anterior, lateral, and medial aspects of the mid-diaphysis of one femur in six greyhounds. Motion and gait analyses were performed to ensure uniform weight bearing prior to strain monitoring. In vivo strain measurements were obtained during normal gait at several speeds on a treadmill. After a 3-month holding period, strain gauges that were implanted on the contralateral femur were monitored. All animals were euthanized and both their femora explanted. Following embedding and histological preparation of the explanted femora, strain measurements were plotted on diagrams of the section shapes of the mid-diaphysis of each femur. Strain distribution diagrams indicated that peak strain levels and strain distributions changed during different phases of gait. Increases in gait speed increased the peak strain levels. In addition, the anterior rather than anterior-lateral aspect of the femur exhibited the highest strain during midstance. Measurements taken from rosette gauges indicated that the principal compressive strain direction was oriented slightly off axis to the long axis of the femur. Measurements from gauges placed along the length of the femur indicated an average strain change of 22.3 microstrain +/- 12.2% over a 2-cm length in the mid-diaphysis. These measurements provide a baseline describing the strain state of the greyhound femur and can be used in computer modeling.
Animals↗
Strain redistribution in the canine femur resulting from hip implants of different stiffnesses.
Bone remodeling adjacent to orthopedic implants has been attributed to bone strain changes. Although many animal studies have assessed bone remodeling near implants, the altered bone strains and even the strains in the intact bone prior to implantation have not been mapped extensively. Instead, bone changes are often correlated with implant stiffnesses. In this study, a benchtop loading system was developed using measurements from in vivo strain analysis to simulate physiologic loading of a canine femur. The effect on bone strains of three different stiffness canine hip implants with the same anatomic shape were compared by taking measurements from the proximal greyhound femur during loading. Peak compressive and tensile strains of the order of 200 to 400 microstrain were measured in the intact and implanted femora. The measurements indicate that during simulated in vivo loading, none of the implants substantially alter the normal strain state of the bone. If initial axial strains significantly affect the remodeling response of bone, the similarity of measurements with the different implants in place suggests that the same remodeling response would be expected to both the stiffest and least stiff implant, as has been noted in animal studies adjacent to the intermediate stiffness implant. It also suggests that this implant shape and initial bone implant interface condition can compensate for strain reductions expected near stiff straight-stemmed implants.
Animals↗
Bone remodeling and in vivo strain analysis of intact and implanted greyhound proximal femora.
Pre- and poststudy motion and gait analyses of eight size-matched male greyhounds confirmed uniform loading of their femora. Subminiature strain gages implanted on the intact inferior and anterior aspects of the femoral neck in six greyhounds indicated in vivo strain variations among test animals. Motion and gait analyses confirmed uniform loading of femora following unilateral hemiarthroplasty with cobalt-chromium hip implants. In vivo strain measurements adjacent to the implants indicated large variations among test animals. A consistent direction of strain change relative to the intact femur was noted, even though strain changes varied in magnitude. Image analysis of microradiographs indicated insignificant differences in the cortical areas of implanted and intact femora. Extensive new trabecular bone formation was noted along the implant in the endosteal cavity and correlated with a combination of implant placement and exercise level. Most of the bone was formed with centrally placed implants in exercised dogs, and the least with stems on the medial neck surface in rested dogs. Iliac crest biopsies indicated that bone formation rates slowed in rested animals and remained constant throughout the study in exercised animals. All implanted femora had a thin (< 1 mm thick) aligned fibrous tissue layer separating the implant from bone. It varied in thickness as a function of the aspect of the implant. Exercised dogs had a larger proportion of fibrous tissue on the anterior and posterior aspects, while rested dogs had a larger proportion of fibrous tissue on the medial and lateral aspects.
Animals↗