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Biomedical subjects

D van Roost

Publications and source records attributed to D van Roost.

10 recordsLinked to original sources
PubMed1999

Corrosion on an internal spinal fixator system.

STUDY DESIGN: Thirteen spinal fixators with 26 stabilization bridges and 52 pedicle screws and a mean length of implantation of 10 months were prospectively examined for corrosion. OBJECTIVES: To determine the type of corrosion and the correlation between the construction of the spinal fixator and the type of corrosion. SUMMARY OF BACKGROUND DATA: Evidence of fretting and crevice corrosion is seen in many stainless steel implants in retrieval studies. Such reactions have not been described in the literature on spinal fixator systems. METHODS: Macroscopic and microscopic alterations in the adjacent tissue were examined, and the corrosive alterations were documented photographically using stereoscopic optical light microscopy. The chemical composition of the implants was determined spectrographically. Microradiography and x-ray fluorescence analysis of the soft tissue were performed. RESULTS: At surgery, tissue discoloration was found in four cases. Histologic examination showed extensive fibrosis, foreign body reaction and inflammation associated with a small number of metal particles, indicating metallosis in five cases. Corresponding particles were detected by microradiography. Corrosion was found on 13 telescopic rods and on two pedicle screws. The alterations on the telescopic rods could be interpreted as crevice corrosion and the alterations in the pedicle screws as fretting corrosion. The two monobloc fixator bridges did not show signs of corrosion. In these implants, the neighboring tissue was macroscopically inconspicuous, and histologic examination showed minimal fibrosis or presence of metal particles. Spectrographic examination of the spinal fixators showed no structural imperfection. CONCLUSIONS: The construction constraints of a spinal fixator make it prone to corrosion. New spinal implants should be examined not only in vitro but also in vivo to ascertain whether corrosion and adjacent tissue reaction occur. Corrosion is one reason to explant the internal fixation system after fusion of the spinal fracture.

Adult↗
PubMed1997

Image guided microsurgery with a semifreehand neuronavigational device.

There is only limited experience with neuronavigators among the neurosurgical community so far. We evaluated such a prototype system in order to define indications for its succinct future use and to adjust it to daily clinical practice. We have employed an infrared light-linked computerized system (SPOCS; Aesculap/ISG) for preoperative planning and intraoperative navigation according to digitized images. A wired, penlike sensor-located "pointer" is used for navigation. Forty-eight patients (22 females, 26 males; aged 7-74 years) with a total of 53 intracranial lesions are included in the study. Fourteen lesions were smaller than 2 cm (26.4%), 33 were 2-4 cm (62.3%), and 6 were greater than 4 cm (11.3%). The documented accuracy was in the range of 3 mm or better in 33 patients throughout the whole operation and in an additional 7 through the most important surgical steps, with satisfactory results in all types of patient positioning except for the sitting position. In one patient the accuracy level decreased too early to perform useful intraoperative navigation. Technical dropouts early in the series led to abortion of the navigation in 7 instances but would currently no longer lead to abortion. There was no additional surgical morbidity associated with the use of the system. With more convenience in instrument design and development of techniques for real-time intraoperative reregistration, this kind of navigational device will play an increasingly important role for assistance during intracranial surgery. It proved to be helpful for planning of the craniotomy, intraoperative guidance on occasions of limited exposure and narrow visual field, localization and resection of small lesions in critical areas, and border definition of large lesions and for pure image guided resection of previously marked regions.

Adolescent↗
PubMed1996

Clinical, radiological, and therapeutic features of pleomorphic xanthoastrocytoma: report of three patients and review of the literature.

Two out of three patients with pleomorphic xanthoastrocytoma were initially misdiagnosed and correctly interpreted only at tumour recurrence, with progression to malignancy in one. The third patient presented with a remarkably long history of epilepsy. Pleomorphic xanthoastrocytoma is a low grade astrocytoma that is still confused with other tumours. Because pleomorphic xanthoastrocytoma can become malignant even after many years of benign behaviour, a long term follow up is necessary.

Adolescent↗
PubMed1994

Subdural and depth electrodes in the presurgical evaluation of epilepsy.

From 1987 to 1992, invasive EEG studies using subdural strips, grids or depth electrodes were performed in a total of 160 patients with medically intractable epilepsy, in whom scalp EEG was insufficient to localize the epileptogenic focus. Dependent on the individual requirements, these different electrode types were used alone or in combination. Multiple strip electrodes with 4 to 16 contacts were implanted in 157 cases through burrholes, grids with up to 64 contacts in 15 cases via boneflaps, and intrahippocampal depth electrodes in 36 cases using stereotactic procedures. In every case, localization of the electrodes with respect to brain structures was controlled by CT scan and MRI. Visual and computerized analysis of extra-operative recordings allowed the localization of a resectable epileptogenic focus in 143 patients (89%), who subsequently were referred for surgery, whereas surgery had to be denied to 17 patients (11%). We did not encounter any permanent morbidity or mortality in our series. In our experience, EEG-monitoring with chronically implanted electrodes is a feasible technique which contributes essentially to the exact localization of the epileptogenic focus, since it allows nearly artefact-free recording of the ictal and interictal activity. Moreover, grid electrodes can be used for extra-operative functional topographic mapping of eloquent brain areas.

Adolescent↗
PubMed1993

Anterior cervical discectomy and vertebral interbody fusion with hydroxy-apatite ceramic. Preliminary results.

Intervertebral plates of hydroxy apatite ceramic (HAC) have been used in three patients for cervical vertebral interbody fusion after anterior discectomy. In one case a pure HAC "Disc" was used, which proved to be too friable. Specially designed intervertebral plates, which were composed of an HAC-coated core of alumina ceramic, were used in the other two cases. Clinically and radiologically optimal results after 1-year- and 2-year-follow-up suggest that HAC-ceramic might be a very promising material for vertebral interbody fusion. Possible complications and pain due to bone removal from the iliac crest are avoided, and the operative procedure is simplified.

Adult↗
PubMed1989

Myelotomies for chronic pain.

The literature on myelotomy for the treatment of chronic pain was reviewed and a total of 635 published cases scrutinized. Two main modes of myelotomy can be distinguished 1) a longitudinal commissural section tuned to the segmental pain level and 2) a focused central lesion, irrespective of considerations of the metameric pain distribution, mainly carried out at a high cervical level. Of the longitudinal commissural myelotomy, a posteriorly restricted and a complete type can moreover be discerned. The pain relief decays with time after myelotomy of any kind. Central myelotomy scores better than complete commissural section for malignant pain in a statistically significant manner but its superiority over posterior commissurotomy cannot be statistically proven. Except of a girdle-shaped hypo-algesia, which is expected after the section of the decussating spinothalamic fibers in a complete commissurotomy, other--irregular--patterns of hypo-algesia have been observed, especially after central myelotomy. This unusual lesion, provoking unusual hypo-algesia patterns, together with phenomena like a preserved sharp-blunt-discrimination within the hypo-algesic area, points at a different sensory channel that might be severed in a central myelotomy as compared with an anterolateral chordotomy or a complete commissurotomy. This hypothesis is matched with recent physiological evidences.

Chronic Disease↗