Biomedical subjects

C Krettek

Publications and source records attributed to C Krettek.

At least 37 records · Page 2Linked to original sources

PubMed2006

Navigated percutaneous pelvic sacroiliac screw fixation: experimental comparison of accuracy between fluoroscopy and Iso-C3D navigation.

Percutaneous sacroiliac screw fixation is technically demanding and can result in complications mainly related to imaging problems. Furthermore, the conventional technique performed using fluoroscopic control is associated with a long radiation exposure. The purpose of this study was to evaluate the accuracy of two navigation technologies used in traumatology; fluoroscopy and Iso-C3D navigation. A total of 40 screws were placed (20 with Iso-C3D, 20 with 2D fluoroscopy) at levels S1 and S2. With both technologies, all S1 screws could be placed correctly, but four (10%) incorrect placements were seen at S2 with fluoroscopy navigation. With all Iso-C3D navigated drillings, no perforation was seen. Iso-C3D navigation therefore proved superior to 2D fluoroscopy navigation for sacroiliac screw fixation in an experimental set-up designed to assess accuracy.

Bone Screws↗

PubMed2006

The influence of distance on registration in ISO-C-3D navigation: a source of error in ISO-C-3D navigation.

Computer-assisted treatments have become increasingly common. Consequently, there is an increased desire for navigation methods with simplified workflow. Anatomic-based pair-point registration is often mentioned as a source of error. Alternatively, the use of preoperatively implanted markers for registration remains complex. The self-acting registration of Iso-C-3D at the moment of data acquisition can reduce essential errors. The aim of this study was to evaluate the effect of reference placement on accuracy, and to determine the maximum acceptable distance between the reference and a given isocentre. This study demonstrates the interdependence of the reference distance on the region of interest (ROI). The mean error of registration amounts to 0.04 mm (0.04-0.05 mm) up to a distance of 200 mm and beyond 0.25 mm (0.24-0.26) for distances beyond 200 mm. The accuracy was significantly lower (p<0.0001) with a distance more than 200 mm. For optimal accuracy when utilizing navigation for pelvic and long bone surgery, the reference base should not been placed at a distance more than 200 mm from the isocentre of interest.

Humans↗

PubMed2006

Preliminary clinical experience using a newly developed minimal-invasive reference base in computer assisted foot surgery.

In recent years, many new tools and techniques have been developed in computer assisted orthopaedic surgery primarily with an industry led effort in software innovation and development. Only a few research and clinical projects have focused on intraoperative difficulties. A common operative challenge in computer assisted orthopaedic surgery is the positioning of the reference base. Rigid fixation of a dynamic reference base is essential in navigated surgery of the extremities. The aim of this study was to develop a minimal-invasive screw which could be placed effectively and efficiently with rotational stability during computer assisted orthopaedic surgery. The minimal-invasive screw was initially evaluated in an artificial bone experiment. After successful results with the artificial bone experiment, it underwent testing in seven human cadaver thighs with ISO-C3D navigated drilling. Finally the screw was transferred into a clinical application during five foot surgeries. In 10 ISO-C3D navigated drillings, the lesions were targeted 100% of the drillings. A screw dislocation was not observed. In comparison to conventional one or two pin fixation systems, the newly designed small screw did not have any observed side effects such as artifacts. In addition, the screw generated less heterodyning than a conventional fixation system. The small screw design is an advantage in theatre. We believe the minimally-invasive screw allows the surgeon to use a tool that helps avoid common pitfalls from conventional fixation systems, and it may improve efficiency.

Bone Screws↗

PubMed2005

Influence of cyclic mechanical strain and heat of human tendon fibroblasts on HSP-72.

Heat shock protein 72 (HSP-72) is a member of a superfamily of different proteins that are synthesized as a cytoprotective response following cellular stress. Mechanical strain is an important component in ligament and tendon healing. Up to the present point of time, the influence of mechanical strain on the expression of HSP-72 is unknown. Tendon fibroblasts from the patellar tendons of nine individuals were isolated and amplified in vitro. First, the effect of 15 or 60 min of heat exposition was studied immunohistochemically and by Western blotting. In a second experiment, the effects of 15 and 60 min of cyclic longitudinal stretching were investigated. Samples were taken after 2, 4 and 8 h. The heat exposition experiments indicate that HSP-72 accumulates in the nucleus and that there is a transient upregulation. This effect is more prominent after 60 min of heat exposure. The same reaction was found after stretching stimulation, however, to a lesser extent. There was a transient up regulation of HSP-72 after short-term stretching and a biphasic increase after 60 min of stretching. Upregulation of HSP-72 by heat and mechanical stress is a response in human fibroblasts which involves a nuclear translocation. The response differs with regard to the time points beyond 2 h after the application of either stress.

Adolescent↗

PubMed2005

Eversion or subluxation of patella in soft tissue balancing of total knee arthroplasty? Results of a cadaver experiment.

Correct postoperative leg alignment and stability of total knee prosthesis over the full range of movement are critical factors for successful TKA. This is achieved by correct implantation of prosthesis and soft tissue handling. However, the surgical approach and how to displace the patella are still controversial. We have carried out a cadaver study looking at the effect of patella eversion or subluxation on limb axis alignment during balancing of the knee in three different standard surgical approaches; subvastus, midvastus, or medial parapatellar. For each approach, five knees were studied. Leg alignment was visualised by the Ci CT-free DePuy/BrainLAB navigation system. Using a navigation system alignment was determined in the AP axis in both extension and 90 flexion, with the patella everted as well as subluxated. Eversion of the patella gave a more valgus axis reading than subluxation in both extension 0.58 (SD: 0.03, range 0.54 -0.60 ) and 90 flexion 0.48 (SD: 0.11, range 0.38 -0.60 ). The effect was greatest using the medial paraptellar approach. Surgeons should be aware that everting the patella influences the AP alignment when soft tissue balancing in total knee replacement.

Arthroplasty, Replacement, Knee↗

PubMed2005

Femoral avulsion fracture of the posterior cruciate ligament in association with a rupture of the popliteal artery in a 9-year-old boy: a case report.

Ruptures of the posterior cruciate ligament (PCL) and especially proximal bony avulsion fractures in children are very rare. This in combination with a rupture of the popliteal artery is extremely rare. Thus, an exact incidence is not available from the literature. Overall, these injuries are severe and often lead to chronic knee instability. We report a case of a 9-year-old boy who suffered a traumatic displacement of the left knee with a rupture of the popliteal artery. Prior to transfer to our department, he was treated by a saphenous vein bypass graft and by a transfixation of the knee using two oblique percutaneous pins. We performed magnetic resonance imaging (MRI) scan of the knee which revealed a femoral avulsion fracture of the PCL. Other ligaments and menisci were intact. A transosseous femoral fixation using non-absorbable stitches was carried out. A 1-year follow-up after surgery demonstrates intact peripheral perfusion and sensation, straight axes of both legs and a physiological gait. Minimal differences of the length and circumference of both legs could be measured. The posterior laxity (Lachman-test) was about 5/8 mm (right/left knee) and 2/5 mm (right/left knee) in 90 degrees flexion. The range of motion (extension/flexion) was 5/0/140 degrees -/5/100 degrees (right-left knee). Intact cruciate ligaments were confirmed by MRI. Minimal experience exists in treatment of combined injuries to the PCL and the popliteal artery in children.

Bone Nails↗

PubMed2005

Infection resistance of unreamed solid, hollow slotted and cannulated intramedullary nails: an in-vivo experimental comparison.

Infection continues to be a problematic complication of fracture treatment, particularly in severe open fractures. The implant design and material as well as implantation technique play an important role in the pathogenesis of local infection. The aim of our study was to determine if the local resistance to infection of a cannulated IM nail is less than that of a solid nail and more similar to that of a hollow nail. In 65 female White Zealand rabbits, the intramedullary cavity was inoculated with matching concentrations of Staphylococcus aureus, and one of the three nails was inserted. The solid nail had a greater than twofold higher resistance to infection (23%) compared to that of the other two nails (hollow, 65%; cannulated, 61%) which was statistically significant (p<0.02). No difference in infection resistance was detected between the hollow slotted and cannulated nail designs (p=1). Although these experimental results may be clinically considered, direct extrapolation to clinical infection rates is ill advised.

Animals↗

PubMed2005

Robot-assisted fracture reduction: a preliminary study in the femur shaft.

Reduction in femoral shaft fractures can be difficult to achieve with minimally invasive techniques. Malalignment and high intra-operative radiation exposure can result. The hypothesis was that robot-assisted fracture reduction could improve the quality of reduction while reducing the amount of radiation exposure. A robot system was developed that allows fracture manipulation with a joystick as input device. The system provides the surgeon with haptic and metric feedback. Fifteen synthetic femurs were broken and reduced by simulated open (group A) and closed techniques (group B). These techniques were compared with the robot-assisted reduction with (group C) and without (group D) haptic and metric information. An image intensifier was simulated with two orthogonal cameras. All reduction techniques showed minor malalignment. In group C, the alignment was: procurvatum/recurvatum 0.6 degrees (0-2.0 degrees); varus/valgus 0.8 degrees (0-3.0 degrees); and axial rotation 0.8 degrees (0-3.1 degrees). A significant difference was seen between the groups (two-way ANOVA, p < 0.001). Axial rotation was significantly lower in group C than in group B (1.9 degrees; p < 0.001). The residual varus and valgus deviation was higher in group C compared with group A (0.4 degrees, p = 0.03). The median number of simulated radiographs was significantly less in group C (35) compared with group D (72; p < 0.001) and group B (49; p = 0.01). Robot-assisted fracture reduction of the femur provides high precision in alignment while reducing the amount of intraoperative imaging. Further research in this field is worthwhile.

Femoral Fractures↗

PubMed2005

[Ankylosing spondylitis. Therapy and complications of 34 spine fractures].

BACKGROUND: Spine fractures in ankylosing spondylitis (AS) are extremely unstable and associated with a high complication rate. The aim of this retrospective study was to evaluate the therapy and complications of these fractures in AS for a better understanding and management. PATIENTS AND METHODS: A total of 32 patients with 34 traumatic spine fractures were treated from 1981 to 2002. Cause of trauma, fracture site, and neurological examination were assessed. Analyses of the management of the treatment and complications were performed. RESULTS: Banal traumas resulted mostly in spinal fractures at the C 5/6 and C 6/7 level. Two patients were treated conservatively, while the others were stabilized operatively. Before therapy was undertaken, six patients suffered from a cervical radiculopathy, ten patients had an incomplete and two a complete paraplegia. After therapy, neurological status improved in eight patients, but one had a deterioration of neurological symptoms. CONCLUSIONS: Dorsal or combined dorsoventral stabilization of these fractures is necessary for better mobilization of these patients and to avoid further complications.

Adult↗

PubMed2005

[Indication for removal of tibial nails].

BACKGROUND: Tibial nail removal has been suggested as a routine procedure for both symptomatic and asymptomatic patients. The aim of this study was to define guidelines for the removal of tibial nails. PATIENTS AND METHODS: A retrospective study on the isolated removal of 69 tibial nails after fracture consolidation was done. A review of the patient charts and radiographs was performed. Forty-four patients (64%) were available for the follow-up interview. RESULTS: Preoperatively, 26 patients (59%) had local complaints. Of these 26 patients, 73% reported an improvement, and 8% reported an aggravation of their local complaints. Of the 18 patients who were asymptomatic before surgery, 17% reported long-term complaints at follow-up. CONCLUSION: We conclude that routine removal of tibial nails should be discussed critically in asymptomatic patients.

Adolescent↗

PubMed2005

[Cartilage cell transplantation as an alternative to endoprosthesis].

The incidence of cartilage lesions is high. Due to pain and loss of function, long-term therapy is often necessary. Isolated, full-thickness articular cartilage lesions with a diameter of 4 cm2 are indications for chondrocyte transplantation. Many outcome studies report good long-term results. In recent years, the cultivation of chondrocytes has changed. Histologic investigations show hyalin-like cartilage after transplantation. Large cartilage lesions facing each other are a therapeutic dilemma in young patients. Implanting unicondylar or bicondylar prostheses is sometimes the last resort for these patients, and there are several reports of good clinical outcome. Cartilage transplantation has until now been recommended for patients younger than 50. It is not an alternative to joint replacement.

Adult↗

PubMed2005

[Operative management of cervical spine injuries in patients with Bechterew's disease].

Cervical spinal injuries in patients with ankylosing spondylitis are complex in their nature and management. This condition is associated with a high risk of dislocation and neurological impairment related to osseous instability due to almost absent compensatory mechanisms of the adjacent vertebral segments. Multilevel stabilization and dorsoventral instrumentation is usually required. We report on two patients suffering from ankylosing spondylitis who presented at our institute with cervical spine injuries in whom primary treatment had consisted of single-site stabilization which resulted in secondary fracture dislocation and implant failure. Secondary management by combined dorsoventral stabilization resulted in more rigid fixation and uneventful healing in both cases. We recommend careful assessment and well-planned management in these cases.

Aged↗

PubMed2005

[Compound osteosynthesis as treatment for an osteoporotic LWK-1 burst fracture in a 76 year old female patient].

The surgical treatment of osteoporotic vertebral compression fractures is rarely necessary and is mostly done in fractures with neurological deficit. We present a case of compound osteosynthesis in an osteoporotic fracture of the first lumbar vertebra as a "salvage procedure" after a dislocation of a dorsal internal fixator in a 76 year old female sustaining incomplete paraplegia. In this case, an additional ventral stabilization using a vertebral body replacement was not practicable because of old age and previous pneumonia. We performed an additional compound osteosynthesis using bone cement because of insufficient stability when only using cement for augmentation of the pedicle screws.

Aged↗

PubMed2005

[Rhabdomyolysis after administration of diclofenac].

Rhabdomyolysis may develop after various traumatic and nontraumatic circumstances. The use of lipid-lowering statins as well as the abuse of stimulants such as methylendioxymethamphetamine (ecstasy) can lead to fatal rhabdomyolysis with acute renal failure. We describe a case of diclofenac-induced rhabdomyolysis after a cumulative dose of 200 mg per os with consecutive critical increase of the creatine kinase and myoglobin. Prescription of diclofenac should therefore be done with caution. In cases of emergent myalgias, immediate testing of creatine kinase and myoglobin is mandatory to exclude fatal rhabdomyolysis with acute renal failure.

Acute Kidney Injury↗

PubMed2005

[What is the influence of the approach to intraoperative measurement of the knee joint on total knee arthroplasty? A navigation-controlled study on a cadaver knee].

Correct postoperative leg alignment and stability of the total knee prosthesis over the full range of movement is one critical factor for successful TKA. The anatomic approach is still the subject of controversy. The aim of our study was to elucidate the influence of the surgical approach on the ligament balancing and the anterioposterior limb axis.On five cadaver knees we studied the influence of the subvastus, midvastus, medial parapatellar, rectus snip, and tuberosity osteotomy approaches on the anterioposterior leg axis in extension and the rotation of the femoral component in flexion. Measurements were performed and documented by CT-free Ci-Navigation-System. Ligament tension was measured with a tensor device. We found that the subvastus approach leads to less widening of the medial compartment than all other approaches in extension. In 90 degrees flexion we found a similar influence. The consecutive release from subvastus to midvastus to medial parapatellar approach leads to a further opening of 0.5-1 degrees valgus in extension as well as in flexion. An everted patella amplifies this influence. The surgeon has to be aware of the impact on the ligament situation in regard to the anatomic approach when ligament balancing and soft tissue releases are carried out. Patella eversion should be avoided when managing soft tissues.

Arthroplasty, Replacement, Knee↗

PubMed2005

[Force distribution in the wrist following scaphotrapeziotrapezoid arthrodesis].

Scaphotrapeziotrapezoid (STT) arthrodesis has been proposed to stabilise the radial column and to redirect the load away from the lunate. Midterm effects on force transmission are still unclear. Six patients who were treated with triscaphe arthrodesis were examined after an average of 5 years using CT osteoabsorptiometry of both wrists. STT arthrodesis had been performed in four cases with Kienböck's disease type IIIb and in two cases of scaphotrapeziotrapezoid arthritis. At all contralateral wrists peak mineralisations were found beyond the lunate fossa and in the scaphoid fossa of the distal radius. At the side with STT arthrodesis there was only one peak. In five cases this density maximum was beyond the scaphoid fossa and in one case half beyond the lunate and half beyond the scaphoid fossa. Triscaphe arthrodesis allows load transmission from the lunate to the radial column.

Arthritis↗

PubMed2005

[Treatment of chronic knee dislocation with an external fixator].

Chronic knee dislocations are rare but represent a therapeutic challenge. A staged concept is necessary to correctly address the pathological components. This article uses a case study to provide an algorithm for the successful treatment of chronic knee dislocations.

Adult↗

PubMed2005

[The development and biomechanical testing of a femoral press fit fixation for hamstring tendons].

PURPOSE: The purpose of this study was to investigate press fit femoral fixation of hamstring tendons and to compare the mechanical properties with press fit patellar tendon bone (PTB) fixation. METHODS: The PTB and hamstring tendons of 30 human cadavers (age: 55.8+/-18.0 years) were used as grafts. An outside-in press fit fixation with a knot in the semitendinosus and gracilis graft (SG-K) and an inside-out (SG-BI) and an outside-in fixation (SG-BO) with the tendons looped over a bone block were compared with a bone-patellar tendon (PT) press fit fixation in 30 bovine femora. The angle between the direction of force and bone tunnel was 60 degrees. The constructs underwent 20 cycles of loading between 60 and 260 N. Constructs were loaded until failure at a speed of 1 mm/sec. Graft fixation was analyzed in terms of maximum load to failure, stiffness and elongation during cyclic stretching. A video analysis of length changes was investigated. RESULTS: There was a significant difference in the maximum load to failure. The SG-BI fixation was inferior to the other three techniques (Mann-WhitneyU-test, P<0.01). There was no difference in stiffness between the techniques. Length changes of PT-fixation from the first to the fifth loading cycle were significantly smaller compared with all other groups (0.73+/-0.58 mm). There was no significant difference between the groups from the 15th to the 20th cycle of cyclic loading. CONCLUSIONS: Press fit fixation of hamstring grafts is technically challenging. However, pull-out forces for SG-O and SG-K were equivalent to BPT-graft fixation. Adequate preconditioning for all hamstring tendon press fit techniques is crucial.

Anterior Cruciate Ligament↗