Biomedical subjects

O Schwarzenbach

Publications and source records attributed to O Schwarzenbach.

13 recordsLinked to original sources

PubMed1999

Treatment of thoracolumbar burst fractures without neurologic deficit by indirect reduction and posterior instrumentation: bisegmental stabilization with monosegmental fusion.

This study retrospectively reviews 20 sequential patients with thoracolumbar burst fractures without neurologic deficit. All patients were treated by indirect reduction, bisegmental posterior transpedicular instrumentation and monosegmental fusion. Clinical and radiological outcome was analyzed after an average follow-up of 6.4 years. Re-kyphosis of the entire segment including the cephaled disc was significant with loss of the entire postoperative correction over time. This did not influence the generally benign clinical outcome. Compared to its normal height the fused cephalad disc was reduced by 70% and the temporarily spanned caudal disc by 40%. Motion at the temporarily spanned segment could be detected in 11 patients at follow-up, with no relation to the clinical result. Posterior instrumentation of thoracolumbar burst fractures can initially reduce the segmental kyphosis completely. The loss of correction within the fractured vertebral body is small. However, disc space collapse leads to eventual complete loss of segmental reduction. Therefore, posterolateral fusion alone does not prevent disc space collapse. Nevertheless, clinical long-term results are favorable. However, if disc space collapse has to prevented, an interbody disc clearance and fusion is recommended.

Adolescent↗

PubMed1999

Anterior cervical interbody fusion with plate fixation for chronic spondylotic radiculopathy: a 2- to 8-year follow-up.

In retrospectively analyzing 35 consecutive patients with chronic spondylotic radiculopathy treated by nerve root decompression, interbody fusion (Robinson technique), and plating, we studied the perioperative complication rate as well as the long-term clinical and radiologic outcomes of an additional plate fixation in degenerative cervical disorders. After an average of 54 months (range 24-102 months), all cases were reviewed for the purpose of this study. There were no perioperative or postoperative complications related to the plate fixation. In particular, there was no infection, graft extrusion, or neurologic deterioration. A solid fusion was obtained in all cases with a single-level fusion and in 87% of the cases with a multilevel fusion. The overall fusion rate was 94%. The clinical outcome of the patients with chronic radiculopathy was comparable with that in the literature, with only three patients (8.6%) having a poor result. This study demonstrated that plate fixation can be a useful adjunct in patients undergoing interbody fusion for cervical spondylotic radiculopathy. Plate fixation seems to reduce the rate of nonunion without additional hazards for the patient. This report should form the basis for a prospective randomized trial to answer the question more conclusively of whether an additional plate fixation is superior to uninstrumented cervical fusion in degenerative disorders.

Adult↗

PubMed1998

Laparoscopic assisted spine surgery.

BACKGROUND: Evaluation of the technical aspects and clinical outcome of laparoscopic assisted interbody fusion (LAIF) using the BAK technique. METHOD: 17 patients with chronic low back pain due to degenerative disc disease at L5-S1 and L4-L5 were treated with LAIF using the BAK technique. Surgical time, blood loss and intraoperative problems were assessed. The short-term clinical and radiological outcome was measured. RESULTS: The technical part of the procedure depends on a learning curve. However, in collaboration with a laparoscopic surgeon no complications related to the technique occurred. The limits of the technique are due to the anatomical situation at the L4-L5 level. 14/17 patients had an improvement in their lower back pain. CONCLUSION: The technique of LAIF is demanding. The L5-S1 level can be addressed with ease; however, transabdominal fusion of L4-L5 is not recommended. Patient selection remains the keystone. LAIF is the least invasive measure in order to stabilize and fuse a motion segment.

Humans↗

PubMed1997

Accuracy of computer-assisted pedicle screw placement. An in vivo computed tomography analysis.

STUDY DESIGN: A computer-assisted planning and visualization system (the Orthopaedic Surgery Planning System) was tested for pedicle screw insertion in vivo. OBJECTIVES: To evaluate the system's applicability for regular intraoperative use and its accuracy for pedicle screw placement in vivo. SUMMARY OF BACKGROUND DATA: Pedicle screw placement poses considerable anatomic and biomechanical risks. The reported rates of screw misplacement with conventional insertion techniques are unacceptably high. It previously has been shown in vitro that computer assistance offers the potential to decrease the number of screws perforating the pedicular cortex. METHODS: The accuracy of 162 pedicle screws inserted with the Orthopaedic Surgery Planning System was assessed by means of postoperative computed tomography evaluation. Reconstructions of the horizontal, frontal, and sagittal planes were analyzed. Cortex perforations were graded in steps of 2 mm. RESULTS: The cortex was perforated in 2.7% of pedicles. Complete preoperative computed tomography scanning of the levels to be operated on is essential to allow for a precise image reconstruction. Initial difficulties in applying the system contribute to the malplacements. A learning curve for general handling of the Orthopaedic Surgery Planning System was observed. CONCLUSIONS: The system provides a safe and reproducible technique for pedicle screw insertion. Other applications in the field of spine surgery are under evaluation.

Bone Screws↗

PubMed1997

Reliability of pedicle screw assessment utilizing plain radiographs versus CT reconstruction.

The position of 119 pedicle screws was assessed on plain antero-posterior and lateral radiographs taken immediately post-operatively and at 3 months' follow-up. The readings of five independent observers were compared with the "gold standard" of CT reconstructions. The position of only 41% of implants (range 14%-56%) was assessed correctly on the plain radiographs (47% on follow-up films). Two-thirds of CT-detectable perforations were missed. As shown with perforations of the anterior cortex, detectability increased significantly with magnitude of perforation. No specifically difficult anatomic level or direction of malplacement could be identified. Interobserver variation was considerable. Plain radiographs were shown to be of limited use in assessing the position of pedicle screws.

Bone Screws↗

PubMed1997

Dens fractures in the elderly. Results of anterior screw fixation in 19 elderly patients.

Type 2 dens fractures in the elderly may be regarded as fragility fractures due to osteoporosis and are prone to nonunion with closed treatment. We investigated the outcome of direct anterior screw fixation of these fractures in 19 patients over 65 years of age. The type of injury, radiological appearance over time and the clinical outcome were analyzed, with an average follow-up of 4.5 years. Surgery and postoperative treatment were tolerated well in all patients. In 16 cases, bony union was achieved after 3-6 months. 2 pseudarthroses, which required no treatment, occurred. At follow-up, 15 patients had no symptoms. 10 of the patients had diminished rotation. We conclude that anterior screw fixation is a successful therapy in most cases of type 2 dens fractures in the elderly.

Aged↗

PubMed1996

Image-guided computer-assisted spine surgery: a pilot study on pedicle screw fixation.

As the pedicle offers a strong point of attachment to the spine, several instrumentation systems using screws that go through the pedicle into the vertebral body have been developed to provide internal stability. All pedicle screw systems share the risk of damage to adjacent neural structures as a result of improper screw placement. A computer-assisted system allowing precise preoperative planning and real-time intraoperative interactive image localization has been implemented for spine instrumentation to optimize transpedicular spine fixation. A validation study was performed in an in vitro set-up drilling 20 pedicle pilot holes in lumbar vertebrae. An analysis in 77 histological cuts showed an ideal location in 70 with no case of injury to the pedicle cortex. We discuss initial clinical experience on cases of posterior lumbar stabilization. Interactive computer-assisted spine surgery provides an accurate and safe approach for transpedicular screw fixation and may provide a useful tool for optimization of spine surgery.

Bone Screws↗

PubMed1995

Computer-aided fixation of spinal implants.

Medical imaging provides an important basis for modern diagnosis as well as for preoperative planning of surgical procedures. However, information gained cannot be transferred directly into the operating room. Furthermore, the safety and accuracy of the surgical intervention would be improved by interactive navigation of surgical instruments. These features are provided by the system for computer-aided fixation of spinal implants described in this paper.

Computer Simulation↗

PubMed1995

Clinical evaluation of a system for precision enhancement in spine surgery.

Most techniques in segmental spinal fixation surgery rely on the identification of predefined targets with the help of anatomical landmarks and on intraoperative use of image intensifiers. However, because there is no direct link between the image information, the accessible spinal anatomy, and the action of surgical instruments several potential problems and possible complications are still involved. A novel system for spinal surgery has been designed allowing for the real-time, intraoperative localization of surgical instruments in medical images. In practice this was achieved by combining image-guided stereotaxis with advanced optoelectronic position sensing techniques. Modules were developed for image data processing, surgical planning and simulation, and various intraoperative procedures. A detailed validation of the system was performed indicating an overall accuracy to be better than the slice distance of the spinal image used. In an in-vitro setting 20 pilot holes for pedicle screws were prepared in human cadaveric lumbar spines. An analysis in 77 histological cuts showed an ideal location in 70 and only minor cortex engagement in seven sections. In vivo the system has been successfully applied in three posterior low lumbar stabilizations with overall 15 transpedicular screws. RELEVANCE--:This article focuses on the clinical evaluation of a computer-assisted surgery system and its application to the operating theatre for transpedicular fixation of the spine. The given approach effectively keeps the surgeon 'in the loop' and requires only minor modifications of the established surgical techniques and associated instruments. The results of this study indicate that advanced computer-assisted techniques may significantly improve the accuracy and safety of surgical interventions of the spine. The proposed technique may in future be adapted to other applications in orthopaedic surgery.

Journal Article↗

PubMed1994

[Surgical possibilities in the alleviation of degenerative vertebral instability].

The indications for operative treatment of degenerative lumbar instability are spondylolisthesis, spinal stenosis and degenerative disc disease. It is important that the indication is based upon a thorough clinical and radiological assessment of the patient. Psychometric tests should be included in the preoperative evaluation. The surgical technique consists for most of the cases of a dorso-lateral fusion. To increase the fusion rate, a pedicular segmental instrumentation system is used. The clinical results for the treatment of degenerative lumbar instability are in more than 80% acceptable. Best results are achieved in spinal stenosis and spondylolisthesis.

Humans↗

PubMed1990

[Spinal metastases and metastasis-induced pathological fractures of the spine].

The vertebral column is a common site of metastatic disease to the bone. The incidence is very high and varies with tumor type. Radiation therapy is effective in the treatment of most cases of spinal metastases. Pathologic fractures of the vertebral body occur in 30-50% of the patients affected, indicating an operative intervention. The ultimate aim of the operation is to increase the patients' quality of life. The tumor mass is normally located in the vertebral body. Therefore, only with an anterior approach can excellent decompression of the spinal cord and reduction of the tumorous tissue be achieved. In patients with advanced metastatic disease, however, in whom an anterior approach is not practicable, tumor decompression may be accomplished through a costotransversectomy combined with posterior stabilization of the spine. Laminectomy is rarely indicated, and then for posteriorly located tumor tissue, and should be combined with dorsal stabilization of the spine. With reference to a few actual cases, we present the approaches and stabilization methods currently in use at our clinic.

Adult↗

PubMed1989

Segmental bone grafting. Comparison of different types of graft in dogs.

We have compared the biological behaviour of eight types of segmental tibial grafts in dogs under different immunological conditions: autografts, allografts, allografts with short-term immunosuppression (4 weeks), and allografts with longterm suppression (20 weeks). Some grafts were revascularised by microsurgical anastomosis, others were not. The long-term immunosuppressed allografts are most similar to autografts in terms of perfusion pattern and graft-host interface healing. The difference between long-term immunosuppressed allografts and allografts which were not immunosuppressed was highly significant (P less than 0.01). The viability of long-term immunosuppressed allografts, as measured by fluorochrome-labelled osteons, did not reach the level of the autografts, but still differed significantly from the allografts which were not immunosuppressed. Immunosuppression, therefore, improves the survival and the quality of the graft, more so for long-term immunosuppressed grafts, and also in revascularised grafts.

Animals↗

PubMed1987

[Measuring blood flow in microsurgically revascularized, immunosuppressed segmental allogeneic bone transplants using laser Doppler flowmetry].

This paper presents Laser Doppler Flowmetry (LDF) as a method for measuring cortical bone blood flow. The goal of this study was to evaluate the efficacy of LDF as a means to determine cortical bone perfusion as an indicator of persistent patency of microvascular anastomoses. Cortical bone blood flow was measured in an experiment using free vascularized immunosuppressed bone allografts. Disulfine blue demonstrated patency in all grafts at 20 weeks sacrifice date, with 15 percent localized areas of nonperfusion, corresponding to areas of microscopic evidence of devitalization. LDF suggested four out of six anastomoses to be nonpatent at four weeks, and irregular evidence of patency at 20 weeks, depending the site of measurement. The small volume of tissue sampled by the probe limits LDF's ability to assess patency of a vessel supplying a whole graft. Comparing LDF with disulfine blue technique, we conclude that the LDF-results in our experiment did not allow general statements regarding the patency of microvascular anastomoses to large segments of cortical bone.

Animals↗