Biomedical subjects

S Hanusek

Publications and source records attributed to S Hanusek.

7 recordsLinked to original sources

PubMed2006

Does tibial rotation correlate with femoral anteversion? Implications for hip arthroplasty.

The aim of the study was to assess the magnitude and variability of rotation of ipsilateral femur and tibia and to identify the existence of rotational correlations. Femoral rotation (FR) and tibial rotation (TR) were measured with computed tomography in 151 consecutive patients when total hip arthroplasty was planned. Median FR was 14 degrees (range, -23 degrees to 91 degrees ) and median TR was 38 degrees (range, 15 degrees -76 degrees ). Femoral rotation was significantly higher in females, in left femora, in the presence of secondary osteoarthritis, and in hip dysplasia. Tibial rotation was significantly higher in females. Femoral rotation and TR positively correlated (r = 0.2963, P = .0001). The magnitude of TR and FR was found to be dependent on each other. Disregarding the variability and magnitude of TR may result in asymmetrical foot positioning after correction of FR during total hip arthroplasty.

Adult↗

PubMed2002

Movement mapping as dynamic preoperative surgical planning in total hip replacement. A precondition to navigation?

The purpose of the present study was to develop and present a computer program for preoperative simulation of implant components placement in total hip alloarthroplasty, and its influence on the possible range of motion (ROM). We evaluated a computer simulation for preoperative estimation of range of motion (movement mapping) in total hip replacement. The computer program was based on Borland C++. The system had an open data port, so the data could be transferred to an Excel spreadsheet for statistical evaluation. With the developed virtual computer simulation, a practical model was established. The model showed range of motion patterns which correspond to clinical experience. ROM was best at a shaft anteversion between 20 degrees and 30 degrees. ROM had its maximum with a CCD angle of 120 degrees -130 degrees. Acetabular cup anteversion was optimal between 10 degrees and 20 degrees, and cup inclinations were optimal below 40 degrees. The presented movement mapping system seems to be a reliable option for dynamic preoperative planning, which may be a prerequisite for the use of intraoperative navigation systems.

Acetabulum↗

PubMed2000

[Virtual simulation for optimizing the range of motion in hip alloarthroplasty using an adapted thrust-plate prosthesis model].

The purpose of the present study was to increase the free range of motion in conventional trust-plate prosthesis design and to optimize the trust-plate contact as well as the osteointegration area below the trust-plate. For the first part of the study, the two-dimensional geometry of the osteotomy plane was demonstrated in 25 CT-reconstructed femora after performing a virtual cut at a CCD angle of 135 degrees. In the second part, we constructed a prototype of an anatomic adapted trust-plate prosthesis (A-TPP) with an optimized trust-plate and corpus geometry based on the three-dimensional data of three human cadaveric femurs (age 67-75 years). In the final step, we documented the range of motion with computer-aided movement-mapping and compared the conventional TPP with the A-TPP. The results showed a wide variance in osteotomy geometry in the 12 femurs. With the A-TPP, we were able to obtain a much better fit in the trust plate surface. The movement-mapping showed a much higher range of motion in the A-TPP implant. With the A-TPP, the implant surface area for osteointegration could also be significantly increased.

Adolescent↗

PubMed2000

[Computer-assisted prosthesis selection and implantation control].

Using CT-based 3D-data of human femora, it is possible to simulate the THR very realistically by a newly developed fit program. The evaluation of OP simulations of different prostheses systems on more than 200 femora showed that a large number of hip joints can only be reconstructed unsatisfactorily by standard stems regarding intramedullary fit and joint geometry. This could be minimized by optimized off-the-shelf prostheses, but there is still a remainder that can only be satisfactorily reconstructed by customized devices. The decision of choosing a standard or custom device for each individual case can be made by the same fit program using CT-data of the femur. Planning with conventional X-rays only shows major restrictions. With the results of our evaluation, "standard stems" have been developed respecting the fixation principles of our CTX-custom device system and with optimized head positions using statistical methods. The selection of the right size regarding the criteria of fixation and joint geometry is examined preoperatively with the help of the same fit program. If standard prostheses cannot fulfill the requirements, we see the indication for a custom-made stem. In this way the quality of custom-made prostheses can be transferred to the application of standard devices. The operative results confirm our expectations of the exact planning and implantation technique. The CTX combination system consisting of off-the-shelf stems and customized devices will reduce the costs for optimized techniques. In comparison with other new 3D-methods like robotics or navigation, our development has an advantage: this technology including the fit program is accomplished preoperatively in order to simplify the operative technique. In future, combinations of our advanced planning methods as well as implantations of custom prostheses using navigation systems and/or robotics seem to be possible and may be helpful for special cases.

Computer Simulation↗

PubMed1999

[Design features of an individual thrust plate prosthesis].

The purpose of the present study was to document the osteotomy plane for the thrust plate prosthesis, and to evaluate the question whether the geometry of the thrust plate itself correlates with the range of motion after implantation and whether the osteointegration area can be optimised. For the first part of the study, the two-dimensional geometry of the osteotomy was demonstrated in 12 computer-reconstructed femurs after performing a virtual cut at a CCD angle of 135 degrees. In the second part we constructed a prototype of an I-TPP with an optimised thrust plate and corpus geometry. In a final step, we documented the range of motion with computer-aided movement mapping. The results showed a wide variance in osteotomy geometry in the 12 femurs. With the I-TAP we were able to obtain a much better surface adaptation of the thrust plate. Movement mapping showed a much lower range of motion in the I-TPP implant.

Bone Plates↗

PubMedDate not supplied

[Assessment of implant position of CTX-custom-made stems with EBRA-FCA in 107 cases of total joint replacement].

AIM: The aim of this study was to assess the ratio of correct and malpositioned stems in a THR population with custom-made stems. Furthermore, any relation of the extent of deviation from the exact stem position and defined patient variables was evaluated. METHODS: Preoperatively, in three-dimensional virtual reality, CTX-individual hip stems were positioned in femora reconstructed from the individual patient's CT data until a stable cortical fit was achieved. Postoperative femoral stem position was measured with EBRA-FCA (EinzelBildRontgenAnalyse-Femoral Component Analysis). Differences of planned and actual depth of stem position were calculated for 107 CTX-custom-made hip stems implanted at one institution. RESULTS: Compared to preoperative planning 59 hip stems were placed too high, while 16 were placed exactly to within one millimeter and 32 were positioned too low. Deviations of postoperative stem position from preoperative planning did not correlate with previous femoral osteotomy found in one-third of femora or femoral anteversion exceeding 25 degrees as present in two-thirds of patients. CONCLUSION: In 71 % the intraoperative stem position did match the preoperative CTX-implant fitting into virtual patient femora. 29 % of implanted stems were malpositioned, i. e., deviations were greater plus or minus 5 mm to preoperative computer planning. None of the examined variables such as body mass index, previous femoral osteotomy, surgical approach, abnormal anteversion angle served as a predictive value for CTX-stem position in this cohort.

Bone Malalignment↗

PubMedDate not supplied

[Validation of computerized tomography antetorsion angle measurement of the femur].

AIM OF THE STUDY: Several CT-procedures exist to determine rotational variances of the femur. However, solely on the basis of few CT-scans and without a three-dimensional reconstruction of the femur, it is impossible to define the exact course of the femoral neck axis. Looking for determination of the exact course of the femoral neck axis, auxiliary constructions need to be called upon. Aim of the study was to validate several existing CT-procedures and analyse their respective error rates. METHOD: Fourty-five femora were CT-scanned and subsequently reconstructed three-dimensionally in this study. Femoral anteversion was measured using three different CT-methods in each of these femora and in addition, the respective anatomical anteversion was determined in each femur. In order to test the reliability of such methods, flexion of the femora around the center of the femoral head as well as a varus deformity of the longitudinal axis of the femora were simulated and anteversion measurements were repeated in such simulated positions. Results were statistically analysed using SPSS. RESULT: All tested CT-methods, when compared to the anatomical anteversion of a femur, showed differing anteversion-angles with statistical significance (p < 0.001). Equally, the results of the individual methods tested differed with significance. Due to a high correlation with the anatomical anteversion, all methods examined expressed trend of anteversion. Under simulated hip flexion, the "Ulmer Method" produced different values with statistical significance which were, however, without correlation to anteversion values in joint extension. With statistical significance, the "Essener Method" produced different anteversion values when the longitudinal axis of the femur was modified; however, these values highly correlated to anteversion values of femora with unchanged longitudinal axis. CONCLUSION: Our results lead us to conclude that the "Essener Method" being an interindividual method and independent from positioning, is the most suitable procedure as it allows for the correction of errors with respect to anatomical anteversion.

Femur↗