Biomedical subjects
Publications and source records attributed to D A Nagel.
We have presented an unusual case of chondroblastoma mimicking a malignant tumor. Retrospective review of radiographs obtained 19 years before the diagnosis gave us a unique opportunity to follow the natural history of this atypical lesion.
Recent experiments have shown that in the sheep spine a displacement of 5.2 mm and a strain of 36% was present at the lumbosacral joint, where fusion almost never occurred when multiple, small (5 mm x 14 mm) cancellous and corticocancellous bone grafts were placed in an interlocking fashion across the decorticated lamina of the lumbar spine and sacrum. A displacement of 1.2 mm and a strain of 10% was found at the L5-L6 joint, where fusion always occurred when the same type of bone grafts were applied in the same manner (described above) over the decorticated lamina of L5 and L6. Firm fixation of the lumbosacral spine and bone graft has brought about an arthrodesis in this model, presumably because the displacement and strain had been limited to acceptable levels. Data are presented to support the concept that, because the spine is composed of bony elements separated by a disc with viscoelastic properties, the biomechanics of spinal fixation and fusion are different than the biomechanics of long bone fixation and fracture healing. These differences should be considered in the design and use of spinal fixation devices.
In a group of nine sheep (Group A), it was noted that when small, interlocking cancellous and cortical cancellous bone grafts are placed posteriorly on the lumbosacral spine, union always occurred in the interlumbar motion segments and almost never occurred at the lumbosacral joint. One of the main differences in these two areas is the amount of motion that occurs at each level with flexion and extension. Because nonunion following bone grafting for arthrodesis of the spine is a serious clinical problem, we have studied the amount of motion seen at the interlumbar and lumbosacral joints in sheep to ascertain how much motion is compatible with union and how much is associated with nonunion. In vivo studies were carried out in eight sheep (Group B), and five normal spine segments were studied in vitro to determine normal motion in this species. To simplify the complex in vivo motion that occurs at the lumbar motion segments, the simple linear displacement and strain of the fusion mass (consisting of fibrous tissue and bone grafts placed on and between the laminas posteriorly) was measured with the spine in flexion and extension. When the displacement and strain at the interlaminar level of the L6-S1 joint was measured, the linear displacement was found to be 5.2 mm and the associated linear strain 36%. The displacement at the L5-L6 interspace was 1.2 mm, and the strain 10%. The stiffness of the L5-L6 joint (which always fused) and the L6-S1 joint (which did not fuse, with one exception) were also studied. In a third group of four animals (Group C), internal fixation of the lumbosacral joint was attempted in addition to bone grafting.(ABSTRACT TRUNCATED AT 250 WORDS)
Three cases of benign giant-cell tumor (GCT) of bone with pulmonary metastasis are reported. In addition, 28 cases from the literature are reviewed. The patients were followed for a mean of 7.8 years (range from two to 29 years). The interval to metastasis ranged from zero to ten years with a mean of 3.2 years. Metastasis was not related to the number of previous operations. The local recurrence rate in the tumors that metastasized was 63%, suggesting that GCTs that metastasize may be an aggressive form of the tumor. The overall mortality rate was 16%. Persistent pulmonary disease does not carry a poor prognosis; surgical resection of accessible pulmonary nodules is recommended to provide histologic confirmation of the diagnosis, and prevent future complications secondary to local growth of the implants, as well as provide a potential cure. Chemotherapy has not improved survival and is associated with significant morbidity and is thus not recommended. Adjuvant radiation is recommended only for control of surgically unresectable lesions because of its potential association with sarcomatous degeneration in GCT.
Observations made during treatment of juvenile pseudarthrosis by pulsing electromagnetic fields (PEMF) suggested that bone growth might be altered. PEMF applied to immature rabbits under conditions of continuous stimulation (24 hours/day for 8 weeks) produced no major changes in bone growth. Continuous stimulation by PEMF induced a statistically significant increase (22%) in femoral articular cartilage glycosaminoglycan. Intermittent PEMF stimulation (12 hours with stimulation/12 hours without stimulation) for 18 weeks produced no significant change in bone growth or time of epiphyseal plate closure. No significant changes in the physical characteristics of growing bone were observed with any treatment.
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UNLABELLED: Five fresh human cadavera were tested to determine range-of-motion measurements at the interspace of the first and second lumbar vertebrae after progressive disruption of the joint followed by internal and external stabilization. The disruption progressed from posterior to anterior, leaving the anterior longitudinal ligament and anterior part of the annulus fibrosus intact. Flexion-extension range of motion was most sensitive to progressive disruptions and was significant following disruption of the facets. The Taylor-Knight brace was effective for limiting lateral motion, fair for limiting flexion-extension, and not effective for rotation. The three-point hyperextension brace was fairly effective for flexion-extension only. The body cast was effective in limiting all motions. Wire loops partially cut through the spinous processes in all cases with extreme flexion. Harrington distraction rods were effective in limiting motion if under proper tension, but they dislodged in three of the five specimens. CLINICAL RELEVANCE: Data from this study show that flexion of the second lumbar vertebra on the first of 20 degrees or a lateral bend of 10 degrees seen on a routine roentgenogram without vertebral fracture indicates that all posterior ligaments and at least part of the annulus fibrosus must be disrupted. Because internal fixation failed on occasion, we strongly urge the use of external fixation and careful mobilization of the patient to prevent flexion and rotation if internal stabilization is used for disruptions of the upper lumbar spine. The body cast was the most effective in limiting motion of the external fixation devices tested.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Twenty patients with tibial fractures had measurements of tissue pressure in the anterior compartment acutely and for the first 72 hours following injury. Measurements were made using a mercury monometric indicator similar to that described by Whitesides. Patients with fractures of the proximal third of the tibia, those with displacement of the fracture fragments greater than 50%, and those whose injury was the result of high-energy trauma developed higher compartment pressures and we conclude that such patients should be observed closely for the development of a compartment syndrome. In normotensive patients in this series fasciotomy was not necessary for tissue pressures less than 50 mm Hg in the absence of any sensory or motor compromise.
Human knee specimens were subjected to anterior-posterior, medial-lateral, varus-valgus, and torsional displacement tests. Loads were recorded for the intact joint and for the joint with all soft tissues cut except for the cruciate ligaments. The effect of condylar interference was determined for anterior-posterior, medial-lateral, and torsional displacements. The variation in load with flexion angle was considerable for medial-lateral (0-90-deg flexion) displacements, and less for varus-valgus (0-45-deg flexion) displacements. The cruciates were found to carry almost the entire anterior-posterior load; they carried a significant percentage of the medial-lateral load which varied considerably with flexion angle. A small, but not insignificant percentage of the varus-valgus load was carried by the cruciates and the variations with flexion angle were small. In torsion, the cruciates resisted only internal rotation. In the tested displacement ranges, condylar interference had a small effect on the medial-lateral load but did not affect anterior-posterior or torsional loads.
UNLABELLED: Using a standardized strain of Escherichia coli 06 and a rabbit knee-joint model, we determined the following values: (1) the effective concentrations of amikacin and carbenicillin in vitro against Escherichia coli 06 when used singly or in combination; (2) the levels of each of these antibiotics in serum and synovial fluid after an intramuscular injection; (3) the effectiveness of amikacin in preventing intra-articular infection when it is administered thirty minutes before and six hours after an intra-articular inoculation of the same strain of Escherichia coli; and (4) the synergistic effects of amikacin and carbenicillin in combination both in vitro and in vivo when used together as a single dose six hours after intra-articular bacterial inoculation. Amikacin was much more effective when administered before joint inoculation and the minimum effective (inhibitory) concentrations of amikacin in vitro and in vivo were approximately the same. A synergistic effect of amikacin and carbenicillin in combination was more clearly evident in vitro than in vivo. CLINICAL RELEVANCE: In vitro tests such as determinations of the minimum inhibitory concentration and the minimum bactericidal concentration, and the serum bactericidal test, can provide valuable guides for the determination of minimum goals for antibiotic therapy. These in vitro tests were related to concentrations of antibiotics in tissue assessed by in vivo bacterial challenge tests and were found to be predictive of efficacy in vivo.
A fracture of the scapula is frequently associated with other significant injuries. In the case described, a motorcycle accident victim sustained multiple injuries, including a scapular fracture associated with a tear of the subclavian artery, demonstrated by angiography and confirmed at operation. A literature review revealed no similar case.
A compartment syndrome of the forearm can be a devastating injury if not relieved promptly by early fasciotomy. Of five patients who developed compartment syndromes, compartment pressures were measured in four and found to average 69 mm Hg. Tissue pressure measurements provided early objective evidence of the presence of the compartment syndrome and contributed significantly to the ultimate functional recovery. We would advise repeating the measurement for pressures in excess of 30 mm Hg in the upper extremity, and fasciotomy for pressures in excess of 40 mm Hg when accompanied by any neurovascular compromise.
Vertebral osteomyelitis is a frequent consequence of disseminated coccidioidomycosis. In a 25-year-old man, the sequela was a single level unilateral osseous bridge between the second and third lumbar vertebra. A review of previous cases has disclosed one case with a similar roentgenographic picture. The occurrence of a single level unilateral reactive process should arouse suspicion of a localized chronic bone infection.
A spectrum of new and commonly used antibiotics was examined with regard to their ability to penetrate into joint fluid in normal and E. coli infected rabbit knee joints. In order to carry out this investigation a new, simple method of measuring antibiotics in very small amounts of synovial fluid was developed. Cephalothin, cefazolin, cefoxitin, carbenicillin, amikacin, and gentamicin all penetrated into synovial fluid effectively achieving peak concentrations within 30 minutes to one hour. Synovial fluid antibiotic concentrations at 2 hours were equal to or higher than simultaneous serum levels. This relationship persisted thereafter. Penetration of antibiotics into infected joints was dependent primarily on serum concentration and was not altered importantly by the presence of acute chronic or previous infection. Antibiotic doses employed were equivalent to clinical usage on a weight basis. Penetration of all antibiotics studied was satisfactory for use against their normally intended pathogens.