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T Hüfner

Publications and source records attributed to T Hüfner.

At least 19 recordsLinked to original sources
PubMed2007

[Cost-benefit analysis of intraoperative 3D imaging].

BACKGROUND: With intraoperative 3D imaging, inevitable corrections may be done already during the operation, and a second procedure can be avoided. The purpose of this study was to perform a cost-benefit analysis during the first year of intraoperative 3D application in order to provide a cost transparency for the surgeon within the current DRG system. METHODS: On the basis of internal data and the literature, the annual operating costs of the ISO-C(3D) were calculated at 27,940 euros (purchase price, depreciation, maintenance, repair), the costs of an average revision as a secondary operation at 2,385 euros (costs avoided with the ISO-C(3D), Siremobil, Siemens, Erlangen, Germany), and the dynamic costs of an intraoperative 3D scan were averaged to 131.08 euros (draping, additional time, personnel). RESULTS: In the year 2003 intraoperative 3D scanning was done in 126 patients, and intraoperative revision was performed in 24 (19%) due to the additional intraoperative 3D information provided by the Siremobil. In 11 (8.7%) patients the implant position was corrected and in 13 (10.3%) patients the reduction was improved. Taking only fixed costs into consideration, 29,311.52 euros could be saved, and when fixed and dynamic costs are taken into account 12,795.44 euros could be saved. Since the parameters for each hospital are different, the following formula for an individual computation is suitable. For the calculation of the cost the following mathematical relationship results: (annual fixed costs) + (costs per scan x number of cases) - (revision costs x revision rate [p]) x number of cases [N]) = 0. DISCUSSION: Although the costs of an ISO-C(3D) are considerably high, an economic benefit can also accrue with frequent application and high rates of avoided revision. However, if the rate of avoided revision adds up to only 5%, a substantial deficit may result.

Cost-Benefit Analysis↗
PubMed2006

[A new parallel drill guide for navigating femoral neck screw placement. Development and evaluation].

BACKGROUND: Trauma navigation applications employ conventional mechanical surgical instruments for the simulation of drilling trajectories. Few complex mechanical targeting instruments, such as guides with fixed angles or with multiple parallel cannulas, have been adapted into trauma navigation systems. We have integrated a complex mechanical tool, the parallel drill guide (PDG) for the minimally invasive treatment of femoral neck fractures, into a trauma navigation module. The combined advantage of a complex yet commonly used mechanical tool with the benefits of fluoroscopic navigation was evaluated. MATERIAL AND METHODS: To adapt the conventional PDG to a fluoroscopic navigation system, the instrument was fitted with a non-detachable reflective marker array. Navigation engineers developed custom software to enable visualization of the navigated PDG. A comparison of conventional versus navigated PDG techniques was performed on plastic bone models and cadavers. No software or mechanical failures occurred with the navigated PDG procedures. RESULTS: While the total operative time was 30% more with navigation compared with conventional techniques, the total radiation time for the navigated group was reduced by more than 60%. This study demonstrates the successful integration of a cannulated parallel drill guide with a fluoroscopic navigation system. CONCLUSION: The continuous display of the complex PDG mechanical instrument, with multiple parallel virtual trajectories, enables safe and accurate parallel screw placement. The integration of complex mechanical instrumentation with navigation for the accurate placement of hardware represents an attractive direction in multiple trauma applications.

Bone Screws↗
PubMed2006

[Precision in orthopaedic computer navigation].

Navigation has become increasingly integrated into orthopaedic surgery, especially in the area of endoprosthetic procedures. Simplification of the instrumentation along with the use of imageless systems has increased the ease of use for the orthopaedic surgeon. Principle navigation systems enable an accuracy of corrections and alignments within intervals of 1 mm or 1 degrees . Consequently, potential intra- and interobserver failures during the registration procedure typically range within a few millimetres or degrees. Analysis of the actual algorithms used for the registration process of the lower extremity mechanical axis and the articular surfaces reveal valid and reproducible results. With the help of navigation, it is possible to achieve a higher degree of precision in total hip and knee implant placement, including a distinct reduction in variance as compared to conventional techniques. Similarly, application of navigation during a high tibial osteotomy or at the osteotomy of the distal radius also enables a more precise correction of the axis of the affected extremity, in addition to improved reproducibility. Despite these promising early results, large prospective clinical studies comparing conventional techniques versus computer assisted navigation are thus far only available for total knee arthroplasty. Whether navigated prosthesis placement can truly extend the longevity of an implant will require continued observation in the years to come. In addition, further prospective studies are required to determine the benefit of navigation in other orthopaedic procedures.

Orthopedics↗
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

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

[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

[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

[Soft tissue management in knees with varus deformity. Computer-assisted sequential medial ligament release].

BACKGROUND: Knees with severe varus deformities and contractures of the medial and lateral collateral ligaments and the posterior capsule require special soft tissue management to gain a stable knee over the full range of movement. The introduction of navigation systems into knee surgery has now made precise measurement of the leg axis and gap size possible. METHODS: Ten knee joints received a computer-assisted total knee replacement (Ci navigation system DePuy) I-Orthopaedics, Munich). The change of the leg axis and the size of the mediolateral gaps were measured and documented when performing a standardized medial ligament release sequence. RESULTS: We found a significant effect after each release step regarding the change of the leg axis as well as the gap width (p<0.001). The highest effect was seen for the 6-cm capsule release in extension and the release of the medial collateral ligament in 90 degrees flexion. CONCLUSION: Implementation of computer-assisted navigation facilitates visualization and quantification of the effect of the sequential medial soft tissue release in total knee arthroplasty.

Arthroplasty, Replacement, Knee↗
PubMed2005

[Intraoperative three-dimensional imaging with an isocentric mobile C-arm at the wrist].

In addition to conventional radiological C-arm image amplifiers used for intraoperative imaging, now a new mobile C-arm image amplifier with an option for three dimensional imaging (Iso-C 3D) is available to visualize reduction of fractures and position of implants. In a wrist-model three titanium pins were placed and three holes of different length were drilled. Distances between the pins and the depths of the drilled holes were calculated in conventional computer tomographic scans and Iso-C 3D scans in perpendicular, 30 degree and 90 degree position of the gantry and compared to actual distances and depths. There were no significant differences between the actual measured distances and those measured by CT scans and Iso-C 3D scans. Furthermore, gantry position had no significant effect upon the results. Iso-C 3D scans are as reliable as conventional CT scans for intraoperative controlling of implant positioning.

Analysis of Variance↗
PubMed2004

[Computer-assisted surgery for pelvic injuries].

For pelvic fractures, pre- and postoperative imaging includes spiral computed tomography, providing high resolution and accuracy. In conventional pelvic operations, these image data cannot be used directly. Intraoperative imaging is limited with fluoroscopy and visualization by the approaches. One solution in terms of precision and reduction of radiation exposure could be computer-assisted surgery (CAS). This method can be divided into navigation, which requires active registration, CT based navigation and registration-free fluoroscopy-based or Iso-C-3D-based navigation. Applications for CAS in the pelvis include sacroiliac screw osteosynthesis in pelvic ring fractures, navigated periacetabular screw fixation, and correction operations for malhealed pelvic ring fractures. Nowadays, CAS is still costly and frequently requires additional staff. However, it helps to reduce complications caused by implant placement. With the introduction of new health care requirements in Germany, this may be an economic argument as well. Current developments focusing on accurate navigated reduction will provide new indications for CAS, further decrease complication rates, and help to reduce the invasiveness of pelvis operations.

Acetabulum↗
PubMed2004

Pelvic emergency clamps: anatomic landmarks for a safe primary application.

The application of the pelvic clamp as a tool for emergency stabilization of unstable pelvic ring fractures has proved to be a life-saving procedure. Using correct technique, the pelvic clamp can be applied within a few minutes after the patient's admission. To avoid severe complications (eg, pin perforation into the pelvis) during the application, anatomic landmarks for the correct pin placement have to be defined. The surface landmarks that are presently recommended for the correct pin placement are not always reliably found due to deformation of the body surface caused by swelling and hematoma. Our experience with 43 emergency applications of the pelvic C-clamp showed that reliable anatomic landmarks on the bony surface of the innominate bone could be identified to ensure correct pin placement. The ideal insertion point of the pins is an anatomic region on the lateral cortex of the ileum, where an easily palpable "groove" is formed by angulations of the lateral cortex of the iliac wing. Being increasingly used as an entry point for percutaneous transiliosacral screw fixations of sacroiliac joint injuries and sacral fractures, this region, which is close to the sacroiliac joint, represents an ideal point for maximum compression of the posterior pelvic ring. With the described technique, this "groove" can be identified easily even in emergency situations by blunt palpation with an instrument, avoiding the time-consuming use of a fluoroscope in most cases.

Emergency Medical Services↗
PubMed2003

[Navigated reposition of transverse acetabulum fractures. A precision analysis].

Up to now navigated reduction control based on computed tomography (CT) image data could not be used commercially. With newly developed software, a transverse fracture of the acetabulum was reduced with navigation control in a laboratory test. The results were compared to visual and tactile control in a foam pelvis and specimen. Measurements were done with another magnet-based navigation system. The residual dislocation was measured with translation (mm) and rotation (degrees). Compared with visually controlled reduction, navigated reduction led to a residual dislocation of 0.7 mm and 0.9 degrees. Navigated reduction based on CT image data is also accurate for reduction of joint fractures under laboratory conditions. Further improvements of the software are planned for later in vivo use.

Acetabulum↗
PubMed2003

[Integration of modern technologies in therapy of sarcomas of the pelvis. Computer-assisted hemipelvectomy and implantation of a "custom-made" Bonit gentamycin coated partial pelvic prosthesis].

The resection of primary malignancies in the pelvis is technically demanding as organs and structures are to be preserved and reconstruction of the defect as well as the postoperative function and rehabilitation are dependent on an optimal prosthesis. We present two patients with a sarcoma of the pelvis where for the first time a structured concept of technology integration led to a press-fit implantation of a hemipelvic prosthesis. This concept includes the design and production of a "custom-made" prosthesis as a hemipelvic substitute and the coating of this prosthesis with Bonit, a second-generation calcium phosphate, and gentamycin in watery solution. The tumor resection was done with computer-assisted surgery based on computed tomographies (CT) of the pelvis model done by rapid prototyping rather than on the CT of the patients' pelvis. With this procedure the presurgically simulated resection could be executed precisely with complete resection of the tumors and an accuracy which allowed an exact implantation of the prosthesis. The course was uneventful with primary healing and no sign of an infection or loosening after 6 months.

Bone Neoplasms↗
PubMed2003

[Navigated Iso-C(3D)-based drilling of a osteochondral lesion of the talus].

Retrograde drilling of osteochondral lesions has obtained acceptable results in the initial stage. Intraoperatively not all lesions are accessible with the arthroscopic technique, despite being readily identifiable with modern imaging preoperatively. As an alternative, open surgical treatment is recommended to achieve good results. The use of computer-assisted navigated retrograde drilling of osteochondral lesions has been described with promising results as a new technique. Computed tomography (CT)- and fluoroscopy-based navigation systems in current use are limited in their flexibility. The drawbacks of fluoroscopy are lack of three-dimensional imaging intraoperatively. CT-based navigation still requires intraoperative cumbersome registration, extra preoperative planning, and imaging with further technical resources. In the current case report, we describe a patient with an osteochondral lesion of the posteromedial talus. In addition to the current method of arthroscopic evaluation and treatment, we also introduce an alternative technique of using Iso-C(3D)-based navigation-assisted retrograde drilling of the lesion. The advantages of this technique are an actual intraoperative three-dimensional imaging for the use of navigation without the need for anatomical registration and an immediate postoperative control of surgical treatment. The results of this case report demonstrate accurately navigated drilling with the described system. The accuracy was confirmed with immediate intraoperative Iso-C(3D) and postoperative CT scans. Our results indicate that the use of an Iso-C(3D) navigation system is a possible alternative to arthroscopic or open drilling for osteochondral lesions of the talus. To provide further evidence for the use of Iso-C (3D)-based drilling, current studies will start at our institution.

Adult↗
PubMed2003

[Navigated osteosynthesis of the proximal femur. An experimental study].

Screw position in femoral head has been considered the most important predictive factor for mechanical failure in pertrochanteric osteosynthesis, and correct positioning is assisted by fluoroscopic control. Although fluoroscopy leads to precise and reproducible results, it is associated with scattered radiation to the patient and surgical staff. Computer-assisted surgery (CAS) may be an alternative in means of achieving precise screw insertion with a low radiation dose. We designed a laboratory study in which artificial proximal femora were submitted to insertions of a dynamic hip screw (DHS) and an anti-rotational screw (ARS). Three set-ups were tested: (1) conventional implantation with two simultaneous C-arms using a guide wire; (2) drilling and implantation controlled by CAS solely with a 3.2-mm drill bit, then insertion of a guide wire and drilling for the dynamic hip screw; (3) after navigated drilling (3.2 mm) a fluoroscopic control was performed. Five variables were used comparing methods and surgeons: operation time, radiation time, tip-apex distance (TAD), and the insertion neck-shaft angles of DHS and ARS. Considering TAD as a precision parameter, CAS led to screw insertion as accurate as with fluoroscopic control, with a reduction of radiation time up to 93%.

Analysis of Variance↗