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Biomedical subjects

M E Janssen

Publications and source records attributed to M E Janssen.

7 recordsLinked to original sources
PubMed2001

Outcomes of allogenic cages in anterior and posterior lumbar interbody fusion.

Interbody lumbar fusions provide a proven logical solution to diseases of the intervertebral discs by eliminating motion of the segment. Historically, there are many techniques to achieve spinal fusion in the lumbar spine. These include anterior, posterior, and foramenal approaches, often in combination with various internal fixation devices. The surgeon's choice of the approach and mechanical or biological implant is dependent on the patient's specific pathology and anatomy, in addition to the experience and training of the surgeon in similar conditions. In the past decade, new mechanical spine implants/spacers have been designed to provide restoration of disc height and improve stabilization of the spine. The ability to radiographically assess the "biology" of bone incorporation in these mechanical (metal) spacers has become a significant limitation. The femoral ring allograft (FRA) and the posterior lumbar interbody fusion (PLIF) spacers have been developed as "biological cages" that permit restoration of the anterior column with machined allograft bone biological cages. Test results demonstrate that the FRA and PLIF spacers have a compressive strength of over 25,000 N. The pyramid-shaped teeth on the surfaces and the geometry of the implant increase the resistance to expulsion at clinically relevant loads (1053 and 1236 N). The technique of anterior column reconstruction with both the FRA and the PLIF biological cages have been previously reported. Clinical outcomes and experience with the FRA spacer (137 patients) and the PLIF spacer (13 patients) were reported on and did not reveal any evidence of bone cage resorption or infectious inflammatory process. There was clinical migration with one PLIF spacer, which was later revised with an anterior approach and a FRA spacer. The radiographic outcomes demonstrated that 94% arthrodesis was achieved with the biological spacer and additional posterior instrumentation. The clinical success of every spine fusion procedure is dependent on many factors such as the extent of the instability, the pathology, type of graft used, the patient's pathology/anatomy and lifestyle.

Biocompatible Materials↗
PubMed2000

Biological cages.

Restoring a stable anterior column is essential to achieve normal spinal biomechanics. A variety of mechanical spacers have been developed and advocated for both anterior and posterior approaches. The ability to radiographically assess the "biology" of bone incorporation in these mechanical (metal) spacers is an inherent limitation. The femoral ring allograft (FRA) and posterior lumbar interbody fusion (PLIF) spacers have been developed as biological cages that permit restoration of the anterior column with a machined allograft bone (biological cage). Test results demonstrate that the FRA and PLIF Spacers have a compressive strength over 25,000 N. The pyramid shaped teeth on the surfaces and the geometry of the implant increase the resistance to expulsion at clinically relevant loads (1053 and 1236 N). The technique of anterior column reconstruction with both the FRA and the PLIF biological cages are discussed. Clinical experience with the PLIF biological cage (10 patients) and the FRA biological cage (90 patients) has not revealed any graft migration, infection, or subsidence. Additional posterior instrumentation may increase the stability of the motion segment, but the degree of stability necessary to achieve a biological union remains unclear. The incorporation of these biological cages can be monitored by conventional radiographic techniques. The method of insertion preserves the vertebral end-plates and can be performed by a minimally invasive or standard open procedure.

Adult↗
PubMed1994

A correlation of cervical magnetic resonance imaging and discography/computed tomographic discograms.

STUDY DESIGN: The morphology of sagittal T2-weighted magnetic resonance imaging (MRI) of the cervical spine was correlated with provocative discography and subsequent computed tomography (CT) discograms in 52 patients with discogenic pain. OBJECTIVES: The authors determined if the morphology of cervical spine discs, as seen on MRI, correlates with discography/CT discograms in patients with discogenic pathology. SUMMARY OF BACKGROUND DATA: Several studies have demonstrated a correlation between MRI and discography in the lumbar spine. No studies have attempted to show if this relationship exists in the cervical spine region. METHODS: The morphology of cervical T2-weighted MRI was characterized with regard to the disc nuclear signal and posterior anulus status. Provocative discography was evaluated with regard to positive or negative responses. Computed tomography was performed after discography on each patient. RESULTS: There was no correlation between pain response or morphology as seen on either discography or CT discography. A significant correlation was found between abnormality as seen on MRI and pain response on discography but the false-positive and false-negative rates were high. CONCLUSION: Our results suggest that several MRI patterns correlate well with positive or negative cervical discography responses while several other patterns are equivocal. Magnetic resonance imaging is a useful adjunct to cervical discography but there are some MRI patterns that cannot be considered pathologic, and discography is required to diagnose discogenic pain syndrome.

Adolescent↗
PubMed1994

Lumbar herniated disk disease: comparison of MRI, myelography, and post-myelographic CT scan with surgical findings.

One hundred eighty patients with suspected lumbar disk disease were evaluated preoperatively with magnetic resonance imaging (MRI), myelography, and post-myelogram computerized tomography (CT) scan. Sixty patients underwent surgery on 102 disk levels, allowing for anatomic confirmation of the diagnosis. Eight negative explorations were performed. The correlation between preoperative interpretations of each test and the observed surgical findings was analyzed statistically. Based on this analysis, MRI accurately predicted the operative findings in 98 of 102 disk levels (96%), while the accuracy of myelography (81%) and post-myelogram CT scan (57%) was significantly less. When myelography and CT scan were utilized jointly, the accuracy was 84%, a significant improvement over either test alone, as a diagnostic modality. There was only one false positive MRI study in the evaluation of lumbar herniated disk. The results of this study reflect that MRI is a clinically superior diagnostic test in the evaluation of patients with suspected lumbar disk herniation, and that it should be the diagnostic study of choice when available. Its noninvasive nature, multiplanar capabilities, and the lack of ionizing radiation are particularly desirable for patient and physician.

Adult↗
PubMed1988

Congenital absence of pericardium: an unusual cause of atypical angina.

Congenital defects of the pericardium are unusual. Patients may experience exertional chest pain, cardiac arrhythmias, syncope, sudden death, or incarceration of myocardium, or they may be entirely asymptomatic. We describe the case of a symptomatic pericardial herniation diagnosed by echocardiography and confirmed by cineangiography. Successful repair was accomplished using a polytetrafluoroethylene soft-tissue prosthesis.

Adult↗
PubMed1987

Endotoxin testing in blood.

A chromogenic assay is presented for the determination of endotoxin (LPS) in blood. The assay is based upon the LPS-dependent activation of Limulus amebocyte lysate (LAL), and the subsequent measurement of the activated enzyme with a chromogenic substrate. Handling and stability of the reagents, details of the assay method in tubes or microtiter-plates, recovery of LPS from spiked blood in platelet-rich plasma (PRP), platelet-poor plasma (PPP) and serum, as well as the possibility to store plasma samples will be discussed. A clinical evaluation of the assay is provided by S. van Deventer et al. in this volume.

Chromogenic Compounds↗