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Biomedical subjects

K Zuber

Publications and source records attributed to K Zuber.

17 recordsLinked to original sources
PubMed2006

Muon-pair production by atmospheric muons in CosmoALEPH.

Data from a dedicated cosmic ray run of the ALEPH detector were used in a study of muon trident production, i.e., muon pairs produced by muons. Here the overburden and the calorimeters are the target materials while the ALEPH time projection chamber provides the momentum measurements. A theoretical estimate of the muon trident cross section is obtained by developing a Monte Carlo simulation for muon propagation in the overburden and the detector. Two muon trident candidates were found to match the expected theoretical pattern. The observed production rate implies that the nuclear form factor cannot be neglected for muon tridents.

Journal Article↗
PubMed2001

Loads acting in an intramedullary nail during fracture healing in the human femur.

The form and function of the musculo-skeletal system is closely related to the forces acting in its components. Significant forces are present in the long bones, but their magnitudes have so far only been estimated from mathematical models. Fracture fixation by means of metal implants provides an opportunity to measure the implant-born forces and to estimate the long bone forces before healing occurs. The load changes during fracture healing may provide additional information. Therefore, a telemetrized, interlocking femoral nail for wireless transmission of forces and moments acting across the fracture site was developed. The design was based on the geometry and material of a 16 mm AO nail with a circular, closed cross-section allowing full protection of the electronic circuits from the body fluids. After careful testing, it was implanted in a 33-year-old patient who had sustained a multifragmentary fracture of the left femur. Measurements at a rate of approx. 0.4 Hz were performed in different patient postures between the 2nd and 26th postoperative week. Significant axial forces and bending moments were measured during several activities such as sitting, unsupported leg elevation and partial weight bearing in a standing position. Forces orthogonal to the nail axis remained small. The reductions of the implant loads due to fracture consolidation were in the order of 50%. Dynamization of the nail did not change the forces. Even though the telemetry system did not allow for dynamic measurements and the results presented here provide data from one subject only, the new information will be useful with respect to implant design, biomechanics of fracture fixation and evaluation of healing progression.

Adult↗
PubMed1993

Treatment of severe spondylolisthesis by reduction and pedicular fixation. A 4-6-year follow-up study.

Ten consecutive patients with severe spondylolisthesis were treated with reduction and pedicular fixation (four Internal Fixator instrumentations, six Cotrel-Dubousset instrumentations). There were six Grade III spondylolisthesis and four spondyloptoses at the L5/S1 level. All patients had complete clinical and radiographic evaluation with an average follow-up of 56 months (range, 43-75 months). The percentage of slippage averaged 78.5% preoperatively and 39.6% postoperatively. The slip angle averaged 43 degrees preoperatively and 17 degrees postoperatively. Four patients with spondyloptosis were treated with combined posterolateral and interbody fusion and had solid fusion without loss of reduction. Five of six patients in whom reduction and stabilization was performed by a single posterolateral fusion demonstrated loss of reduction, nonunion, and implant failure. Four of these patients were reoperated. Ultimately all patients had resolution of pain, solid fusion, and no further slip progression. Reduction, pedicular fixation, and combined posterolateral and interbody fusion is a technically demanding procedure, which should be reserved for selected patients. Pedicular fixation systems may only allow permanent reduction and stabilization of high-grade spondylolisthesis in conjunction with a combined interbody and posterolateral fusion.

Adolescent↗
PubMed1993

National survey of ovarian carcinoma. I. A patient care evaluation study of the American College of Surgeons.

BACKGROUND: The Commission on Cancer of the American College of Surgeons recently finished a national survey of patients with ovarian cancer patients. The goal was to compare the patterns of care over a 5-year period. METHODS: Data were collected from 25 consecutive patients whose disease was diagnosed first at 904 hospitals with cancer programs in 1983 and 1988. RESULTS: There was a total of 12,316 patients, of whom 80% were 45-85 years old. Contrary to popular belief, only 8.2% of patients were nulliparous; 85% of patients had one to five children. Of significance, 18.2% of patients with ovarian cancer had undergone a previous hysterectomy with ovarian preservation. Primary surgical treatment was used in 94.9% of patients and consisted of: oophorectomy, 81.9%; hysterectomy, 55.1%; and omentectomy, 59.0%. However, only 12-25% of patients had biopsies of the diaphragm, paracolic gutters, colon, small bowel, pelvic and paraaortic lymph nodes, and cul-de-sac to permit adequate surgical staging. The primary surgeons were: gynecologic oncologists, 21%; obstetrician-gynecologists, 45%; general surgeons, 21%; and others, 13%. CONCLUSIONS: These data indicate that additional resources are needed to improve the care of patients with ovarian cancer.

Adult↗
PubMed1992

[Bilateral femoral fracture at the site of bilateral hip prostheses. A case report].

Fracture of the femoral shaft after hip arthroplasty is a serious problem. In most cases, minimal trauma is responsible for the fracture. Predisposing factors include severe osteoporosis, loosening of the prosthetic stem and perforations of the cortex. The incidence in our patient material in 2.3% after total hip arthroplasty and 2.9% after revision. Operative treatment may consist in osteosynthesis with compression plates, screws, or cerclage wires with or without revision of the arthroplasty. We give a case report covering treatment and 2-year follow-up for a bilateral proximal femoral fracture in a 72-year-old farmer with bilateral total hip replacements. Both fractures were treated similarly, with replacement of the femoral components by a cementless Wagner revision stem prosthesis and cerclage wiring of the fragments. No classic osteosynthesis was required to manage the fractures.

Aged↗
PubMed1991

Treatment of cervical spine injuries with anterior plating. Indications, techniques, and results.

This study analyzed 86 patients who sustained a cervical spine injury and who had 93 anterior surgical interventions of the cervical spine. The average age of the patients was 39 years, the mean follow-up 40 months. Twenty-two patients had predominantly vertebral body fractures (burst or tear-drop fractures) and were treated by bisegmental anterior bone grafting and plating. Sixty-four patients had predominantly posterior lesions, either discoligamentous or osteoligamentous, and were treated by unisegmental bone grafting and plating. Forty-three patients were neurologically intact. There were no relevant complications except in one patient, who needed reoperation because of a secondary redislocation due to a technically insufficient osteosynthesis. The technique of anterior bone grafting and plating is shown to be straight-forward, atraumatic, and reliable for predominantly anterior lesions as well as for posterior injuries when performed properly. This clinical experiences does not support experimental data and earlier clinical work, which advocate posterior surgery over anterior surgery and assert that anterior surgery should not be done in predominantly posterior lesions.

Adult↗
PubMed1990

[Femoral fractures following total hip prosthesis].

Fractures of the ipsilateral femur after hip arthroplasty are a serious problem. In most cases, minimal trauma is responsible for the fracture. Predisposing factors, such as severe osteoporosis, loosening of the stem of the prosthesis, or cortex perforations, are often found. Such fractures occurred between 1979 and 1989 in 30 patients, i.e. 2.3% of our patients who had received primary prosthesis and 2.9% of those who had undergone revision. The patients' ages at the time of fracture ranged from 41 to 88 years (mean 63 years), 33% of the patients in these group being female. The time lapse from implantation of the prosthesis to the fracture varied between 1 month and 11 years (mean 4.4 years). The fracture was at the level of the proximal trochanteric region in 3% of these patients, between the trochanteric line and the tip of the prosthesis in 20%, and below the tip of the prosthesis in 70%. Operative treatment was performed in 29 patients. Fractures were fixed with a compression plate in 19 (63%), and in 3 the plate fixation was reinforced with intramedullary cement. In 2 osteoporotic patients with supracondylar fractures the osteosynthesis ruptured and a successful revision operation with cement was performed. In 3 others internal fixation was combined with replacement of the prosthesis; 3 patients received a Wagner revision prosthesis and 1 a long-stem Protek tumor prosthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

The arthroscopic meniscal repair. Techniques and clinical experience.

Conservative meniscal repair should limit resection to only pathologic portions of the meniscus. The periphery of the meniscus is well vascularized, enabling healing of longitudinal tears. Sutures that perforate the meniscus vertically usually lead to stable healing. In arthroscopic meniscal surgery, isolated tears are sutured from within the joint, usually using techniques related to specially developed instrumentation. Our system uses three curved cannulas of various radii and a specific needle of 1.2 mm thickness, and can be operated by one hand while the joint is distracted with an AO/ASIF femoral distractor. In our series of 54 arthroscopic meniscal repairs, 42 (78%) healed without reinjury. Retears occurred in 12 patients, and were refixed again using the same techniques. Our experience has led us to conclude that the type of meniscal tear most suitable for arthroscopic repair is a vertical longitudinal lesion that involves the vascularized zone; abrading the synovial surfaces is helpful, as is positioning the sutures tightly together; the repair should be checked at 4 months by arthroscopy or by arthrogram; and a combination of nonabsorbable and resorbable sutures is most satisfactory. We believe that with experience arthroscopic meniscal repair becomes a less involved procedure than open repair, and that in the future such repair will be successfully extended to the more centrally located lesions.

Adolescent↗