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L Kinzl

Publications and source records attributed to L Kinzl.

At least 55 records · Page 3Linked to original sources
PubMed2002

[Sources of error and risks in CT based navigation].

Based on the experience of 4 cervical, 102 thoracic/lumbar pedicle screw and 14 transiliosacral screw implantations all problems and complications were collected. Problems noted within the data collection in the preoperative CT were an incomplete acquisition of the surgical target (n = 3), an exceeding of the processable scan slices (n = 1) and a non focused field of view. Transmission of the CT datas often were documented as incomplete (n = 16). Segmentation of the CT dataset turned out to be the significant problem with incorrect differentiation of the bone-soft tissue transition (n = 2), where as the choice of the matching points and the trajectories did not provoke any mistakes in the planning modus. The intraoperative matching of both corresponding datasets was insufficient (n = 7), while the assignment of the CT dataset to the correct vertebral was not a major problem (n = 1). Navigation was not possible (n = 2) due to an instability of the spinal process. All fiducial based matching procedures (pelvis) were carried out without any problems. During intraoperative navigation potential complications resulted from deformation of instruments (n = 1) and interaction of instruments and the data reference base (n = 2). Further, the CT-based navigation of fractured vertebrae or unstable iliosacral joints is not safe, because dislocations between acquisition of the dataset and operation will lead to misguidance.

Artifacts↗
PubMed2002

[MACS-TL polyaxial screw XL. A new concept for increasing stability of ventral spondylodesis in the presence of dorsal injuries].

The influence of additional dorsal structure damage on anterior stabilization of thoracolumbar fracture is still unknown. Screw cement enhancement is a possibility to reinforce the stability of anterior instrumentation. A new anchorage system has been developed for fixation of anterior stabilization devices, adapted through geometric optimization and the possibility of optional additional cementation after screw insertion in cases of poor bone quality. Is this enhancement strong enough to support a single anterior procedure such as the thoracoscopic technique and still compensate for dorsal instability? A biomechanical in vitro study simulating an anterior corpectomy, strut grafting, and overbridging stabilization with a dorsal laminectomy as dorsal structure damage was performed, and the primary stability parameters were evaluated with and without screw cement enhancement. The additional cementation enhanced the primary stability of the anterior instrumentation and compensated for dorsal instability.

Aged↗
PubMed2002

Correlation of bone mineral density with strength and microstructural parameters of cortical bone in vitro.

The aim of this study was to evaluate the influence of microstructural parameters, such as porosity and osteon dimensions, on strength. Therefore, the predictive value of bone mineral density (BMD) measured by quantitative computed tomography (QCT) for intracortical porosity and other microstructural parameters, as well as for strength of cortical bone biopsies, was investigated. Femoral cortical bone specimens from the middiaphysis of 23 patients were harvested during total hip replacement while drilling a hole (dia. 4.5 mm) for the relief of the intramedullary pressure. In vitro structural parameters assessed in histological sections as well as BMD determined by quantitative computed tomography were correlated with yield stress, and elastic modulus assessed by a compression test of the same specimens. Significant correlations were found between BMD and all mechanical parameters (elastic modulus: r = 0.69, p < 0.005; yield stress: r = 0.64, p < 0.005). Significant correlations between most structural parameters assessed by histology and yield stress were discovered. Structural parameters related to pore dimensions revealed higher correlation coefficients with yield stress (r = -0.69 for average pore diameter and r = -0.62 for fraction of porous structures, p < 0.005) than parameters related to osteons (r = 0.60 for osteon density and average osteonal area, p < 0.005), whereas elastic modulus was predicted equally well by both types of parameters. Significant correlations were found between BMD and parameters related to porous structures (r = 0.85 for porosity, 0.80 for average pore area, and r = 0.79 for average pore diameter in polynomial regression, p < 0.005). Histologically assessed porosity correlated significantly with parameters describing porous structures and haversian canal dimensions. Our results indicate a relevance of osteon density and fraction of osteonal structures for the mechanical parameters of cortical bone. We consider the measurement of BMD by quantitative computed tomography to be helpful for the estimation of bone strength as well as for the prediction of intracortical porosity and parameters related to porous structures of cortical bone.

Aged↗
PubMed2002

[Combined posterior and anterior endoscopic supported instrumentation of the thoracic and lumbar spine. Arguments, concepts and first clinical results].

The operative therapeutic principles of thoracic and lumbar spine injuries are based on reposition, decompression and stabilization of the unstable area. Secondary loss of correction and consecutive deformation have negative impact on the long-term results after defect fractures of vertebral bodies and will be minimized only by the reconstruction of all involved spinal columns. With dissemination of thoracoscopic techniques at the thoracic spine and minimal invasive retroperitoneal approaches at the lumbar spine a decrease of the morbidity was achieved with equal effectivity for recalibration and fusion. Our experiences with the first consecutive 42 patients, treated minimal invasive are presented. Indications for anterior thoracoscopic and minimal invasive instrumentations after posterior transfixation are remaining osseous defects of the end plates of more than a quarter of the volume of the involved vertebra in case of migration of the vertebral disc, wedging of the vertebral body after posterior reposition of more than 10 degrees and persisting anterior encroachment of the spinal canal of more than 30 %. The decision is based on radiographs and CT-scans, performed after posterior stabilization.

Bone Transplantation↗
PubMed2002

Operation planning of correction osteotomies in 3D.

This paper discusses an operation planning system for correction osteotomies. It is based on 3D data obtained from CT/MR of the bone and it allows to perform a 3D planning. The physician can individually determine anatomical landmarks for measuring geometric parameters of the bone like length, angle and torsion angle. In a virtual scene he or she can set a single cut or can remove/insert a wedge, dissecting the bones. The bone parts can be rearranged in 3D space. Optimization routines allow that the physician only defines the position of the cut, the orientation of the cut plane, the rearrangement of the bone and the optimization for the maximal overlap of the cortical bone can be processed automatically. The system is currently in use at the Trauma department at the University of Ulm. A case study shows the results by applying this system.

Bone Malalignment↗
PubMed2001

First histological observations on the incorporation of a novel calcium phosphate bone substitute material in human cancellous bone.

Calcium phosphates are frequently used as bone substitute materials because of their similarity to the mineral phase of bone, absence of antigenicity, and excellent osteoconductivity. However, in most currently available mineral substitutes, resorption occurs slowly if at all. In contrast, calcium phosphate cements have shown rapid resorption and remodeling in animal studies. In two prospective studies, a novel amorphous calcium phosphate cement (Biobon) was implanted in human patients for the first time. After 2-12 months, ten biopsies were obtained from nine individuals during secondary surgical interventions, for example, for implant removal. In all specimens, partial replacement of the material by new bone was observed, while residues of the cement were still visible. Undecalcified sections revealed extensive bone formation in immediate contact to the cement without fibrous interface. Polynucleated cells and superficial lacunae were indicative of resorptive activity, but inflammatory tissue response was absent. The new bone displayed regular trabecular and osteonal patterns. The histologic findings are in accordance with the excellent biocompatibility observed in the clinical follow-up. Though still incomplete, the resorbability of this cement appears superior to sintered calcium phosphates in these biopsy specimens. Presumably this is due to its amorphous crystalline structure. Biobon merits further studies as a promising substance for bone defect reconstruction in non-stress-bearing areas.

Aged↗
PubMed2001

Prediction of cortical bone porosity in vitro by microcomputed tomography.

The high importance of intracortical porosity for mechanical strength of cortical bone has been established. The contribution of other parameters of microstructure such as osteon dimensions for strength is in discussion. The aim of this study was to evaluate the predictive value of microcomputed tomography (mCT) for porosity and other microstructural parameters of cortical bone in cortical bone biopsies. Femoral cortical bone specimens from the middiaphysis of 24 patients were harvested during the procedure of total hip replacement at the location where normally one hole (Ø 4.5 mm) for the relief of the intramedullary pressure is placed. In vitro intracortical porosity and bone mineral density (BMD) measurements by mCT were compared with structural parameters assessed in histological sections of the same specimens. A strong correlation was found between intracortical porosity measured by mCT and histological porosity (r = 0.95, P <0.0001). Porosity measured by mCT was also a strong predictor for other parameters describing dimensions of porous structures. BMD?1 was associated with osteonal area (r = -0.76, P <0.0001). We consider the measurement of porosity by mCT as a very potent procedure for assessing intracortical porosity and parameters related to porous structures of cortical bone nondestructively in vitro.

Aged↗
PubMed2001

Spinal navigation in cervical fractures--a preliminary clinical study on Judet-osteosynthesis of the axis.

OBJECTIVE: To evaluate the accuracy of CT-based and computer-aided screw insertion into the pedicles of the axis using the method of Judet. Materials and Methods In two patients, four transpedicular implants of C2 were positioned using a computer-guided technique. One patient with iatrogenic destabilization of the posterior structures C3 and C4 and one patient with a hangman's fracture of the axis required pedicular fixation. In addition, intraoperative documentation of the additional time required for the navigation procedures was made. Finally, postoperative CTs of each patient provided further information about transpedicular implant localization. RESULTS: Image-guided implantation of screws was possible in all scheduled pedicles of the axis. In the postoperative CT scans, none of the inserted screws perforated the medial or lateral pedicle. All screws were accurately positioned within the pedicles, and no anterior perforation of the screws into the vertebral foramen was observed. CONCLUSIONS: Our initial results using computer-aided implantation of Judet screws showed that these screws were inserted correctly. However, it is important to realize that movements can occur in the vertebral arch and lateral mass during the time between preoperative CT and surgery. This possibility for movement should be taken into account when procedures such as CT-based insertion of image-guided screws into patients with fractures of the isthmus C2 are performed, because damage to neurovascular structures can result. Therefore, this navigation system should only be used by experienced surgeons who can, if necessary, continue the intervention with more conventional techniques. In addition, it is essential that the surgeon have a complete understanding of the principles of the tracking systems to prevent possible misinterpretation of computer-generated information.

Adult↗
PubMed2001

[Endoprosthesis in medial femoral neck fractures].

UNLABELLED: Alloarthroplasty of the hip joint in the elderly has improved significantly the outcome of femoral neck fractures. The indication for a hip replacement is based on the biological age of the patient and the type of fracture. In our hospital in a 5-years period (1996-2000) we treated operatively 305 patients with femoral neck fractures (248 medial, 57 lateral). Of these, 239 patients received a endoprosthesis (190 total hip joint replacements, 49 hemialloarthroplasty). The other 66 patients (most of them younger patients) were treated by osteosynthesis. The complication rate of the endoprosthetic hip replacement was low; five hematoma/seroma and two deep infections had to be treated operatively. In 21 patients (8.79%) we saw hip luxation; 17 could be treated by closed and four by open reduction. Reluxation was found in nine of these 21 patients. Only two patients (both over 80 years old) died between the first 2 postoperative weeks. Eighty percent of the patients were able to walk, half of them alone or with help outside their homes. Fifteen percent of the patients could be mobilized in a wheel chair; only 5% were confined to bed. CONCLUSION: For the treatment of femoral neck fractures in older patients, the cemented hip endoprosthesis is the method of choice.

Adult↗
PubMed2001

[Severe complications of Staphylococcus aureus infection in the child].

Life threatening complications can be caused by staphylococcal infection, even if they appear as a simple pustulosis, via hamatogenous dissemination. On the other hand the bacteria is able to penetrate the skin without pre-existing skin lesions and reach the adjacent soft tissue, as was the case with a 9 year old boy who had a contusion of the left shoulder and a consecutive life threatening septicemia.

Abscess↗
PubMed2001

[Problems of malunited fractures of the distal radius].

The essential problematic of the distal fracture of the radius lies in the quality of its reduction and retention. 35 patients with distal fractures of the radius and strain fractures of the styloid process of the ulna were followed up with regard to their functional and radiological results and their subjective symptoms. Patients with intra-articular fractures were found to have significantly poorer functional results compared to those with extra-articular fractures. 29 out of 35 patients developed a nonunion of the styloid process of the ulna in the form of a compensatory false position with a significant dorsal tilt of the articular surface of the radius. Their functional results were also significantly poorer than those of the other 6 patients. The patients whose radii were shortened by more than 2 mm also had significantly poorer functional results and a median dorsal tilt of 5 degrees of the articular surface. Where the dorsal inclination of the articular surface of the radius exceeded 5 degrees, a significant increase in the scapholunar angle, which averaged 62 degrees, was found. On the basis of these figures, we conclude that in the reduction of the distal fracture of the radius, shortening by not more than 2 mm and a dorsal inclination of the articular surface of the radius, taken laterally, of not more than 5 degrees should be tolerated in order to minimise functional impairments of the wrist.

Fractures, Malunited↗
PubMed2001

[Ambulatory prevention of thrombosis in traumatology].

There are no guidelines for the use of heparin in the prophylaxis of deep vein thrombosis in outpatients. In a prospective clinical investigation in 1996 and 1997, 1321 outpatients after trauma of the lower extremities were screened by duplex-color-coded-ultrasound in order to detect deep vein thrombosis. There were two separate groups: group A with drug prophylaxis of deep vein thrombosis (n = 723) and group B (n = 598) without. The classification A or B was mainly related to the ability of weight bearing (at least 20 kp) and of ankle mobility (at least 20 degrees). Patients who did not achieve both criteria were classified in group A and were treated with heparin until they attained a higher level of activity (B). Group A showed 30 deep vein thrombosis while group B had no thromboembolic complications. We conclude that outpatients achieving a level of activity close to a physiological situation will show no thromboembolic complications.

Adolescent↗
PubMed2001

[Arthroscopically-assisted reconstruction of the anterior cruciate ligament with autologous patellar tendon replacement-plasty. 5 years results].

This study presents the five-year follow-up-results (range 56 to 63 months) of 76 of 119 patients who had had arthroscopically assisted reconstruction of the anterior cruciate ligament with use of the central third patellar tendon for acute rupture (19 patients = group A) or chronic ACL insufficiency (57 patients = group B) between may 1991 and october 1993 in the Department of Trauma Surgery University Hospital Ulm. The average Lysholm knee score was 94.6 points (group A = 97.1, group B = 93.8 points). The IKDC-score rated 21.1% of all patients as A (group A = 31.6%, group B = 17.5%), 57.9% as B (group A = 52.6%, group B = 59.6%), 19.7% as C (group A = 15.8%, group B 21.7%) and one patient of group B as level D. 9 patients (= 11.8%, group A = 21.1%, group B = 8.8%) showed up to 10 degree extension loss (compared with contralateral knee), one patient of group A (1.3%) more than 10 degree. A flexion loss up to 15 degree was seen in 12 patients (= 15.8%, group A = 21.1%, group B = 14.0%), of more than 15 degree in 3 patients (= 3.9%, group A = 5.3%, group B = 3.5%). The average KT-1000-side-to-side difference was 2.5 mm with 90 N (group A 2.4 mm, group B = 2.5 mm), 2.8 mm with 133 N (group A = 2.7 mm, group B = 2.8 mm) and 3.2 mm (both groups) for manual maximum. There was no statistically significant difference in quadriceps and hamstring isokinetic strength (Cybex) of operated vs. unaffected limb for 60/s as well as 240/s. X-ray analysis showed arthrotic signs of minimum one compartment in 22.3% of all patients (group A = 26.3%, group B = 21.1%). In summary, we found better long-term results of IKDC-score in patients with autogenous patellar tendon graft for acute ACL-rupture vs. chronic ACL insufficiency. In Lysholm knee score and KT-1000 arthrometric measurement we just saw little but not statistically significant differences between the two groups. The isokinetic strength of quadriceps and hamstring were similar between operated vs. unaffected limb as well as between group A and B.

Adolescent↗
PubMed2001

[New methods in polytrauma surgery. Results of a Study Congress at castle Reisenburg 27/28 February 2000].

Recently, in Germany the academic environment has changed and an upheaval occurred that directly do affect academic research activities. Increasingly, the funding of scientific projects is not provided anymore by the universities themselves or the government, but has to be acquired as grants. While in the past, research was conducted by single departments, nowadays and more and more in the future scientific networks have to be established by combining 'local' and even 'distant' knowledge. With this changing background in mind representatives of different scientific institutions met at the Reisensburg castle to discuss the current state and future trends in four major research fields: "Epidemiology of Severe Trauma", "Head Injury", "Pathophysiology of Damage to the Chest", and "Posttraumatic Soft Tissue Injury".

Germany↗
PubMed2001

[Influence of prosthesis design on intramedullary pressure formation in femur shaft implants of cemented hip endoprostheses].

The increase of intramedullary femoral pressure can lead to the intravasation of bone marrow and fat cells into the blood stream of the femoral vein and consequently into the pulmonary circulation. This effect is the same in intramedullary nailing and in the implantation of femoral stem prostheses. In a prospective study we evaluated the intraoperative, intramedullary pressure in the distal femur during the implantation of femoral stem prostheses with two different designs. In eight patients we implanted Müller straight stems and in another eight we implanted stem type Option 3000. Intramedullary pressure was recorded continuously by the implantation of a microtip pressure probe (piezoresistive principle, 50 Hz) in the distal femur. We found markedly higher pressure in Müller straight stem prostheses: range: 590-2,570 mmHg (median = 1,293, SD = 627 mmHg). Intramedullary pressure in stem prosthesis type Option 3000 was much lower: range: 59-574 mmHg (median = 289, SD = 219 mmHg). The differences were statistically significant (p = 0.0008). By changing the designs of femoral stem prostheses, the intramedullary pressure can be markedly reduced. In the case of elderly patients or those with pulmonary illness we recommend femoral stem prosthesis designs, which induce little increase in the intramedullary pressure, in order to reduce cardiopulmonary complications.

Bone Cements↗
PubMed2001

[Precision in standardized Iso-C-Arm based navigated boring of the proximal femur].

C-arm navigation is a new tool in computer assisted surgery. The aim of this study is to evaluate the accuracy of Iso-C-arm based drill holes in the proximal femur. In nine artificial proximal femura, two holes with an angle of 135 degrees and 100 degrees in relation to the shaft axis were drilled in the direction of the femoral head. The defined target of the 3.2 mm drillings was a 4 mm steel ball, which had previously been placed and fixed at the cranial center of the femoral head. All the drillings were standardized with a navigated drilling machine fixed to a frame which only allowed movement of the system in the direction of the drill. During navigation the positions of the drill before commencement and at the deepest point of the canal were recorded. After drilling all specimens were evaluated by CT, and the coordinates of the center of the start and the end of the drilled hole and the center of the ball were determined. Using vector calculation, the smallest distance between the straight line, defined by the center of the starting point and the end point of the drill hole, and the center of the ball was calculated. Additionally, the coordinates of the intersection between the perpendicular to the center of the ball and the straight line were determined (xv, yv, zv), to evaluate the direction of misplacement of the drilled canal in relation to the target. For the 135 degrees drill holes, a median of 2.5 mm for the smallest distance between the straight line, given by the center of the start and the end of the hole, and the center of the ball was investigated (range 1.6-3.7 mm). For the 100 degrees holes the median was 3.1 mm (range 1.8-4.2 mm). The main plane of deviation in all of the 135 degrees holes was posteriorly, whereas in the 100 degrees holes posterior deviation occurred in four cases, cranial in three cases, and in one case each caudal and anterior deviation occurred. In our opinion, the accuracy of fluoroscopy based navigation applied in the region of the proximal femur is sufficient and reproducible. This technique can be used for implant placement at the proximal femur in the future.

Equipment Design↗
PubMed2001

[Precision analysis of navigation-assisted implanted thoracic and lumbar pedicled screws. A prospective clinical study].

A prospective clinical trial was performed to study the accuracy of pedicle screw placement of consecutive computer-aided and conventional techniques. Concerning the clinical performance of the navigation system, the average time of matching has been 8.4 minutes per vertebrae. For evaluation of the results, only complete intraosseous placement of the pedicle screw has been defined as correct position. Any medial or lateral perforation of the cortical structure of the pedicle was recorded as malplacement. In the CT-controlled patients complete intrapedicular placement of the screw was obtained in 36 of 45 thoracic (80%) and in 22 of 27 navigated lumbar (81%) pedicles. In the conventional cohort group 27 of 34 (79%) thoracal and 43 of 52 (83%) lumbar screws were completely in. No radicular neurologic damage, caused by a malplaced transpedicular screw has been observed in both groups. In the presented study is shown, that the application of the computer-assisted freehand navigation can improve results concerning the precision of spinal screw placement. Although, the spinal navigator has to consider a learning curve for the clinical inauguration of the system and the qualification of the implant system for computer-assisted application.

Bone Plates↗