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Biomedical subjects

M C Zimmerman

Publications and source records attributed to M C Zimmerman.

At least 37 records · Page 2Linked to original sources
PubMed1992

The mechanical properties of the canine lumbar disc and motion segment.

A study was initiated to measure the mechanical properties of the canine lumbar spine disc and motion segment at two specific levels. Compressive stiffness was determined to be 717.8 N/mm at L2-3 and 949.0 N/mm at L5-6. Torsional stiffness was found to be 1.04 Nm/deg at L2-3 and 1.72 Nm/deg at L5-6. These data were then compared to human lumbar spine disc and motion segment properties that have been reported in the literature. After normalizing for size differences, the canine lumbar disc showed a similar axial modulus (14.03 MPa for L2-3 and 16.30 MPa for L5-6) and a significantly higher torsional modulus (30.80 MPa for L2-3 and 26.17 MPa for L5-6) when compared to human values. The relative contributions of ligaments, posterior elements, and intervertebral disc to overall stability of the motion segment was found to be similar in canines and humans. As has been shown in human spine research, the posterior elements including the facet joints were found to be significant structures in providing torsional rigidity of the canine spine.

Animals↗
PubMed1992

Shear stability of an elastomeric disk spacer within an intervertebral joint: a parametric study.

A parametric study was conducted to compare the resistance to shear force provided by three surgical implantation techniques and three endplate designs for use with a polymeric lumbar intervertebral disk spacer. While under an axial load, the implant was pushed out laterally through the surgical window created for implantation. Force at 0.3 mm displacement, slope of the initial portion of the force-displacement graph, and maximum force were measured. The results indicate that implants with pegs, inclined planes, or domes on the surfaces of the disk will add significantly to the shear stability of the implant while maintaining the simplicity of a single part device.

Animals↗
PubMed1991

Effects of environmental exposure on carbon polysulphone composites.

In vivo and in vitro studies were designed to characterize the material degradation associated with implantation of carbon fibre-reinforced polysulphone (C/PS). Composite plates were compression moulded for both studies, and a fibre orientation of 0 degrees with the long axis and a fibre volume fraction of approximately 55% were used. The in vitro experiment involved soaking three groups of four plates each at 4, 12 and 26 wk in 0.9% saline solution at 37 degrees C. The plates were measured for weight gain after each time period and mechanically tested non-destructively in four-point bending to determine modulus. The in vivo experiment involved implanting three groups of eight composite plates (24 total) subcutaneously in the abdomens of 12 rabbits (two implants/animal). Implants were harvested at 4, 12 and 26 wk after implantation and evaluated for changes in weight or modulus of elasticity. In vitro results showed a statistically significant (P less than 0.05 paired t-test) increase in weight for all time periods: 0.41, 1.25 and 0.93% weight gain for the 4, 12 and 26 wk periods respectively. In vivo results were similar to those in vitro: 0.66, 1.06 and 1.15% weight gain for the 4, 12 and 26 wk periods respectively (P less than 0.05 paired t-test). There was no statistically significant difference between the pre- and post-implantation modulus of elasticity for any time period in vivo or in vitro. However, in both studies, on average, the modulus tended to increase with environmental exposure.

Animals↗
PubMed1991

Biomechanical comparison of fixation devices in experimental scaphoid osteotomies.

This study determined the force, bending rigidity, and bending moment at failure of three types of internal fixation systems for the scaphoid bone. A pair of parallel, 0.045-inch Kirschner wires were compared on a paired, bilateral basis with either a Herbert screw or a 3.5 millimeter cannulated screw in repairing a transverse waist osteotomy in cadaver scaphoids. The mean values at failure of the Herbert screw and the cannulated screw versus the paired, parallel Kirschner wires for force (65 N and 77 N versus 23.7 N), rigidity (0.47 Nm2 and 0.54 Nm2 versus 0.16 Nm2) and bending (0.98 Nm and 1.15 Nm versus 0.36 Nm) were approximately three times greater. These differences were statistically significant when compared on a paired basis. This experiment demonstrates that the Herbert screw and cannulated screw are significantly stronger in resisting bending forces than paired, parallel Kirschner wires.

Biomechanical Phenomena↗
PubMed1991

Development of a prosthetic intervertebral disc.

This article is a preliminary report of a 10-year investigation of the development of an intervertebral disc prosthesis. Spinal fusion is a method for the treatment of chronic, disabling low-back pain that does not respond to nonoperative treatments. Spinal fusion, however, has various adverse effects, and the results of spinal fusion are often unpredictable. The goal of this research project was to develop disc prostheses that have mechanical properties very similar to those of natural, normal discs. Two types of disc prosthesis, one with fiber-reinforced polyurethane and the other with multicomponent, non-fiber-reinforced polymers (C-Flex), have been designed and manufactured. The fiber-reinforced disc was made of polyurethane end-plates with A100 hardness, a homogenous nucleus with A40, and 12 layers of multidirectional (0, +45 degrees), fiber-reinforced anulus with A40 polyurethane. The design and modeling of the multicomponent polymers (non-fiber-reinforced) was made of C-Flex endplates with A90 hardness, a nucleus with A35 occupying 35% of the volume, and an anulus with 70A. Mechanical testing of these disc prostheses demonstrated similar mechanical properties to those of natural, normal discs.

Biocompatible Materials↗
PubMed1991

Computer-assisted instruction in otolaryngology: the use of a database for examination review.

A database of questions and answers has been developed to assist residents in reviewing current topics in otolaryngology-head and neck surgery. Each question/item has an associated answer, general category, specific category, and reference that allows cross-referencing on the computer system. The user can search the database for categories of interest and obtain a specific subset of questions. This allows an efficient means of knowledge acquisition and review for Board examinations. Additional data entry is also facilitated to expand the database as desired. Currently there are more than 2300 items in the database.

Computer-Assisted Instruction↗
PubMed1991

Gunshot wounds to the extremities. Experience of a level I trauma center.

Gunshot wounds to the extremities are more common today, largely because civilian handgun injuries have increased. Such injuries, which are usually caused by low-velocity missiles, should be treated differently from those caused by high-velocity (military) missiles. Bone involvement, including fractures and joint injuries, necessitates orthopaedic management. At the University of Medicine and Dentistry of New Jersey-New Jersey Medical School's (UMDNJ-NJMS) University Hospital, a level I trauma center, 44 gunshot wounds (32 lower-extremity and 12 upper-extremity) with orthopaedic complications were treated between January 1986 and December 1988. The protocol/questionnaire used by the UMDNJ-NJMS is presented here to assist the orthopaedic surgeon in the evaluation and treatment of these problematic injuries.

Adolescent↗
PubMed1990

Preliminary characterization of bioresorbable and nonresorbable synthetic fibers for the repair of soft tissue injuries.

Preliminary characterizations of two new synthetic fibers were performed to determine their potentials for use in soft tissue scaffolding devices. A slowly bioresorbing random copolymer of dimethyltrimethylene carbonate (DMTMC) and trimethylene carbonate (TMC) was the first fiber evaluated. The second was a nonresorbable high-strength synthetic fiber of highly oriented polyethylene. Their in vitro mechanical behavior was evaluated by loading fibers in uniaxial tension to determine mechanical properties in dry and wet (saline) environments. The polyethylene fiber had a dry strength of approximately 2.0 GPa, an ultimate strain of 3 to 4%, a tangent modulus of 57 GPa, and was not affected by the saline environment. The bioresorbable fiber had a dry strength of approximately 500 MPa, an ultimate strain of 35%, and tangent modulus of 5.4 GPa. The in vitro resorption of the bioresorbable fibers produced a 15% loss in strength over a 10-week period. In vitro cell-fiber compatibility studies were conducted to assay material biocompatibility and fiber substrate efficacy. Fibroblasts proliferated and migrated on both the polyethylene and bioresorbable fibers at rates similar to those previously found for other compatible fibers, thus demonstrating the new materials to be similar in their in vitro biocompatibility profiles. Morphological assessment with SEM also confirmed that these materials were suitable substrates for cell attachment. A rabbit Achilles tendon repair model using oriented polyethylene or bioresorbable fiber tows was evaluated after 12 and 26 weeks of implantation. The mechanical performances of both types of tendon repairs were similar to those found in previous studies using carbon or PET fibers. The polyethylene fibers elicited a low-grade chronic inflammatory tissue response. The bioresorbable fibers were still intact at 26 weeks and remained relatively inert in the host tissue, eliciting a minimal foreign body response.

Animals↗
PubMed1990

The evaluation of cortical bone remodeling with a new ultrasonic technique.

Total hip arthroplasty causes biomechanical changes in the normal femur including a redistribution and concentration of stress. These mechanical alterations in the femur cause local remodeling and resorption that affect the geometry and mechanical properties of the bone. Three complementary techniques were used to study the local adaptive remodeling of bone due to prosthesis implantation. A graphics package was used to obtain section geometrical information, an ultrasonic wave propagation technique to determine elastic properties, and a new scanning acoustic microscope (SAM) to map the acoustic impedance profile of each section. The effects of the implantation of two different types of hip prostheses were investigated, an uncemented bipolar prosthesis with an Austin-Moore type stem and a cemented Charnley prosthesis. Prosthesis implantation resulted in an increase in cortical area and mediolateral diameter and a decrease in anterio-posterior diameter. Both prostheses had a detrimental effect on local elastic properties as determined by acoustic velocity measurements. Finally, the SAM system provided information about local inhomogeneities in bone properties not obtainable by any other means. The acoustic impedance maps highlighted bone resorption and bone remodeling on a microstructural level.

Aged↗
PubMed1990

The sphenoid sinus--a site for metastasis.

While metastatic tumors to the nose and the paranasal sinuses overall are unusual, metastasis to the sphenoid sinus is exceedingly rare. Presented are 26 cases of metastasis to the sphenoid sinus. Seven were treated at UCLA between 1955 and 1988, and 19 additional cases were discovered from a search of the medical literature. The patients ranged from 14 months to 79 years of age. The most common tumor sites from which sphenoid metastases arose were the prostate and the lung. In 11 of the 26 cases, the sphenoid sinus metastasis was the first presentation of malignancy. Patients manifested signs and symptoms that were indistinguishable from those from primary tumors of the sinus. They included headache, facial pain, visual changes, and single or multiple cranial neuropathies. While cure of patients with sphenoid metastasis has not been reported, significant palliation with resolution of morbidity is possible in many patients with radiation therapy. Although metastasis to the sphenoid sinus is an uncommon entity, when present, signs and symptoms relating to this metastasis are frequently the first presentation of disease. As such, patients with sphenoid sinus symptoms suggestive of sphenoid sinus malignancy should be vigorously evaluated for the possibility of primary as well as metastatic tumor of the sinus.

Adenocarcinoma↗
PubMed1989

Maxillary ameloblastoma. A potentially lethal neoplasm.

Ameloblastomas are benign tumors derived from the odontogenic apparatus. Of these tumors, 80% originate in the mandible, while 20% originate in the maxilla. Six cases of maxillary ameloblastoma treated at the UCLA hospitals are presented; four of these cases showed extensive and destructive tumor growth involving vital structures, including the orbit, base of skull, and parasellar structures. Two of four patients with extensive disease died of their tumors, one, with extensive involvement of the base of the skull, became unavailable for follow-up, and, one year after diagnosis, one is alive with middle cranial fossa disease. A review of the medical literature provides further evidence of the locally aggressive behavior and potentially lethal nature of this tumor. No effective treatment has evolved for extensive ameloblastomas of the maxilla that have invaded surrounding vital structures. When tumor-free surgical margins are not possible, radiation therapy may offer palliation of disease.

Adolescent↗
PubMed1989

The evaluation of bone remodeling about orthopaedic implants with ultrasound.

Total hip arthroplasty causes biomechanical changes in the normal femur, including a redistribution and concentration of stress. These mechanical alterations in the femur cause local remodeling and resorption that affect the geometry and mechanical properties of the bone. Two complementary ultrasonic techniques were used to study the local adaptive remodeling of bone due to prosthesis implantation. An ultrasonic wave propagation technique was used to determine elastic properties and a new scanning acoustic microscope (SAM) mapped the acoustic impedance profile of each section. The effects of the implantation of two types of hip prostheses, an uncemented bipolar prosthesis with an Austin-Moore type stem and a cemented Charnley prosthesis, were investigated. Both prostheses had a detrimental effect on local elastic properties as determined by acoustic velocity measurements. The SAM system provided information about local inhomogeneities in bone properties not obtainable by any other means. The acoustic impedance maps highlighted bone resorption and bone remodeling on a microstructural level.

Aged↗
PubMed1989

Tension band wiring-bone grafting for spondylolysis and spondylolisthesis. A clinical and biomechanical study.

Patients with spondylolysis or spondylolisthesis with persistent symptoms often require surgical treatment. The purpose of this article is to present a new surgical technique and clinical results of 13 patients with symptomatic spondylolysis/spondylolisthesis who were treated with tension band wiring (intra- or intersegmental) and bone grafting techniques. This article also presents the results of biomechanical effects of these tension band wiring methods on canine lumbar spines with experimental spondylolytic defects. Thirteen adult patients, three with spondylolysis, and ten with spondylolytic spondylolisthesis, were treated with intrasegmental or intersegmental wiring with bone grafting technique, and the clinical results were evaluated at the mean follow-up period of 20 months. Patients with spondylolysis were treated with intrasegmental wiring (transverse processes to the spinous process of the same segment) with bone grafting at the lytic defect. Patients with spondylolytic spondylolisthesis were treated with intersegmental wiring (transverse process of the segment with defect to the spinous process of the same segment and to the spinous process of the segment below) with bone grafting to the defect and one-level fusion. All 13 patients had a solid spinal fusion and/or healing of the defect at the follow-up evaluation. Eleven had excellent clinical results; one a good, and one a fair result. The results of the biomechanical study showed that the experimental spondylolytic defect produced a significant decrease in bending stiffness (flexion-extension), and the wiring techniques (both the intra- and intersegment) increased the bending stiffness to that of the normal intact spinal segment.

Adult↗
PubMed1989

The biomechanical evaluation of a new fixation technique for spondylolysis using single and double tension-band wiring.

Patients with spondylolysis or spondylolisthesis with persistent symptoms are often marked for surgical treatment. This paper presents the results of a biomechanical study which evaluated the effects of two tension-band wiring methods for this clinical anomaly. Experimental spondylolytic defects were created in canine cadaver lumbar spines, and both wiring techniques were evaluated in cantilever bending. The results demonstrated that experimentally created spondylolytic defects produce a significant decrease in bending stiffness (flexion/extension), and that both the intra- and intersegmental wiring techniques increase the bending stiffness to that of the normal intact spinal segment.

Animals↗
PubMed1989

Bone attachment to hydroxyapatite coated polymers.

Bone attachment to two classes of hydroxyapatite (HA) coated polymers was evaluated mechanically and histologically. Particulate HA was molded into the surface of thermoplastic implants and cast into the surface of thermoset implants. Coated and uncoated implants of both types were implanted in the distal femurs of rabbits for four and twelve weeks. After sacrifice, the bone/implant interface was evaluated mechanically via a push-out test with a servohydraulic test system. Paired statistical analysis revealed significantly greater shear strengths for coated vs. uncoated implants for both polymer systems at both time periods. Mixed mode of failure occurred with particle removal from the polymer surface and from the bone. One animal at each time period was saved for histology. Histology at both time periods indicated direct bone apposition to the HA coating as compared to a fibrous encapsulation about the uncoated implants. This was confirmed with backscatter scanning electron microscopy and scanning acoustic microscopy. Hydroxyapatite coatings significantly improve the bond strength between polymers and bone by allowing direct bone apposition and some mechanical interlocking with the bone.

Animals↗
PubMed1988

Granular cell tumors of the head and neck.

Granular cell tumors have a predilection to occur in the head and neck. Thirty granular cell tumors have been diagnosed during the past 26 years at UCLA; 13 of which presented in the head and neck. Of these 13 cases, 10 were correctly diagnosed on the primary pathological specimen, which included one fine-needle aspirate and three frozen sections. Four cases required diagnostic confirmation with electron microscopy or histochemistry. The tongue accounted for more than one third of the cases. Three lesions exhibited locally aggressive behavior, but none of the tumors metastasized. Initial treatment was wide local excision in all but one case; recurrence was noted in two cases. Fine-needle aspiration can be used to provide preoperative diagnosis of granular cell tumors. Wide local excision with histologically confirmed clear margins provides definitive treatment.

Adult↗
PubMed1987

Treatment of impending carotid rupture with detachable balloon embolization.

Acute carotid artery rupture is frequently heralded by prodromal arterial bleeding. This warning signal provides the physician with a brief interval in which to hemodynamically stabilize a patient, electively occlude the carotid, and consequently improve the patient's chance of survival. For three years, we have employed an initial nonoperative approach to patients with impending carotid rupture. A trial of endovascular balloon occlusion followed by detachable balloon embolization of the carotid artery has been utilized. Patients unable to tolerate temporary occlusion underwent a vascular bypass procedure followed by embolization. Six patients have undergone this approach, and all had permanent cessation of bleeding. None died as a result of the procedures. One patient developed permanent neurologic deficits. Balloon embolization offers improved results over elective ligation and should be considered as an alternative treatment for patients in this dire predicament.

Adult↗