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"Stadler, Christian"
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DEIT-Based Bone Position and Orientation Estimation for Robotic Support in Total Knee Arthroplasty—A Computational Feasibility Study
Total knee arthroplasty (TKA) is a well-established and successful treatment option for patients with end-stage osteoarthritis of the knee, providing high patient satisfaction. Robotic systems have been widely adopted to perform TKA in orthopaedic centres. The exact spatial positions of the femur and tibia are usually determined through pinned trackers, providing the surgeon with an exact illustration of the axis of the lower limb. The drilling of holes required for mounting the trackers creates weak spots, causing adverse events such as bone fracture. In the presented computational feasibility study, time differential electrical impedance tomography is used to locate the femur positions, thereby the difference in conductivity distribution between two distinct states s0 and s1 of the measured object is reconstructed. The overall approach was tested by simulating five different configurations of thigh shape and considered tissue conductivity distributions. For the cylinder models used for verification and reference, the reconstructed position deviated by about ≈1 mm from the actual bone centre. In case of models mimicking a realistic cross section of the femur position deviated between 7.9 mm 24.8 mm. For all models, the bone axis was off by about φ=1.50° from its actual position.
Journal Article
The relationship between product and international diversification: The role of experience
We establish prior diversification experience as a key determinant of the relationship between growth of product and international diversification. Prior diversification experience allows firms to overcome short-run constraints on simultaneous diversification growth imposed by the difficulty to transfer tacit knowledge, ambiguous competencies, and limited absorptive capacity. Studying U.S. and European firms, we find a positive relationship between growth in product and international scope for firms with high and a negative one for those with little prior diversification experience. Further, we find that product diversification experience has greater impact than international diversification experience.
Journal Article
Jungfraujoch: hardware‐accelerated data‐acquisition system for kilohertz pixel‐array X‐ray detectors
The JUNGFRAU 4‐megapixel (4M) charge‐integrating pixel‐array detector, when operated at a full 2 kHz frame rate, streams data at a rate of 17 GB s−1. To operate this detector for macromolecular crystallography beamlines, a data‐acquisition system called Jungfraujoch was developed. The system, running on a single server with field‐programmable gate arrays and general‐purpose graphics processing units, is capable of handling data produced by the JUNGFRAU 4M detector, including conversion of raw pixel readout to photon counts, compression and on‐the‐fly spot finding. It was also demonstrated that 30 GB s−1 can be handled in performance tests, indicating that the operation of even larger and faster detectors will be achievable in the future. The source code is available from a public repository. A new data acquisition and real‐time image analysis system with FPGAs and GPUs for kilohertz macromolecular crystallography applications is presented.
Journal Article
Gender differences in cementless short stem total hip arthroplasty: significantly higher femoral lengthening in female patients
Modern cementless short stems in total hip arthroplasty (THA) enable a precise reconstruction of the native pre-arthritic hip geometry. While gender differences have been reported for older generation straight hip stems, there are hardly reports regarding modern cementless short hip stems. Therefore, we aimed to evaluate the influence of gender differences in hip anatomy in cementless short stem THA. A total of 207 patients (109 females, 98 males) with unilateral THA and absence of contralateral joint space narrowing (Kellgren-Lawrence grade ≤ 2) were included. Acetabular height and offset as well as femoral height and offset were measured on pre- and 3-months-postoperative anteroposterior X-rays of the pelvis and compared to the contralateral hip. Additionally, implant position was evaluated on the postoperative radiograph. In male patients, the loss of acetabular offset was significantly greater than in females (p = 0.012), leading to a compensatory increase in femoral offset (p = 0.041). Femoral height discrepancy was significantly higher in females (p < 0.001), accounting for an increased global hip height discrepancy (p < 0.001). The mean acetabular anteversion was significantly greater in female patients (p < 0.001). Female patients are at higher risk of femoral lengthening in THA with a cementless short stem potentially caused by a further proximally conducted femoral neck osteotomy and show significantly higher cup anteversion angles. Therefore, surgeons should take special care to the level of neck resection and implant positioning in female patients.
Journal Article
A neck-sparing short stem shows significantly lower blood loss in total hip arthroplasty compared to a neck-resecting short stem
Short stems are associated with a significantly lower blood loss (BL) compared to straight stems in total hip arthroplasty (THA). Different types of stems differ in design, fixation and level of femoral neck osteotomy. Therefore, we sought to evaluate the difference regarding the perioperative BL between two short stems with different designs in direct anterior approach (DAA). A total of 187 THA performed by a single surgeon were analysed. 107 patients received a neck-resecting (Group A) and 80 patients a neck-sparing short stem (Group B). Blood counts of the day before surgery and of two days after surgery were evaluated. Total blood volume and BL were calculated. Additionally, duration of surgery was analysed. The perioperative BL was significantly lower in Group B (451.4 ± 188.4 ml) compared to Group A (546.6 ± 232.7 ml;
p
= 0.002). The postoperative haematocrit (31.6 ± 3.7% vs. 30.4 ± 4.4%;
p
= 0.049) and haemoglobin-level (11.0 ± 1.3 g/dL vs. 10.4 ± 1.5 g/dL;
p
= 0.002) were significantly higher in Group B. Duration of surgery was significantly shorter in Group B (62.0 ± 11.4 min vs. 72.6 ± 21.8 min;
p
< 0.001). The use of a neck-sparing short stem leads to a significantly decreased BL compared to a neck-resecting short stem in DAA THA. A less extensively conducted capsular release necessary for optimal femoral exposition might lead to a lower perioperative BL and shorter durations of surgery.
Journal Article
Is there a difference in pelvic and femoral morphology in early periprosthetic femoral fracture in cementless short stem total hip arthroplasty via an anterolateral approach?
BackgroundThe pelvic and femoral morphology are associated with the occurrence of early periprosthetic femoral fractures (PFFs) in cementless total hip arthroplasty (THA). Differences exist depending on the performed approach and implanted stem design. Therefore, this study was conducted to analyze the pelvic and femoral morphology in cementless short stem THA via a minimally-invasive (MIS) anterolateral approach.MethodsA retrospective, single-center, multi-surgeon, comparative propensity-score matched study of a cohort of 1826 short stem THAs was conducted. A total of 39 PFFs within the first 90 days after surgery was matched on a 2:1 ratio to non-fracture patients. The morphology of the proximal femur was analyzed with canal flare index (CFI), canal-calcar ratio (CCR), canal-bone ratio (CBR), morphological cortical index (MCI), and femoral cortical index (CI). The pelvic morphology was analyzed with ilium–ischial ratio (IR), distance anterior superior iliac spine to the tip of the greater trochanter (AGT). Both groups were analyzed regarding several parameters for femoral and pelvic morphology in non-parametric testing and univariate regression analysis.ResultsA significantly higher AGT was detected in the fracture group (104.5 mm ± 18 versus 97.4 mm ± 9.8; p = 0.016). All other femoral and pelvic parameters did not differ between both groups, also when compared depending on the Vancouver type of the PFF.ConclusionsThe morphology of the proximal femur and the pelvis do not differ in several radiological parameters in patients sustaining a PFF in cementless short stem THA via an anterolateral approach compared with matched non-fracture group. The findings are controversial to other studies with different stem types and approaches. Future studies should focus on analyzing the influence of the pelvic geometry and the shape of the proximal femur in the occurrence of PFFs in different approaches with the same stem type and vice versa.Level of Evidence Level III case-controlled study
Journal Article
Periprosthetic femoral fractures in minimally-invasive anterolateral short stem versus transgluteal straight stem cementless total hip arthroplasty: What are the differences in the femoral and pelvic morphology?
Background
The occurrence of periprosthetic femoral fractures (PFFs) in cementless total hip arthroplasty (THA) might be associated with the proximal femoral morphology and the pelvis. PFFs in short stem THA are associated with an increased Canal Flare Index. PFFs in straight stem THA show a decreased Canal Flare Index. Therefore, this study aims to compare the femoral and pelvic geometry in PFFs between short stem and straight stem THA.
Methods
A retrospective comparative propensity-score matched study was performed. An institutional database of 5358 THAs was screened for early PFFs within the first 90 days after surgery. All cases of 136 PFFs in primary cementless THA were collected and matched, resulting in 67 PFFs in the straight stem and 37 PFFs in the short stem group. Both groups were analyzed regarding several parameters for femoral and pelvic morphology.
Results
A significantly lower distance from the anterior superior iliac spine to the greater trochanter (AGT) was detected in the straight stem group (96.4 vs. 104.8 mm,
p
= 0.024). All other femoral and pelvic parameters did not differ between both groups. Postoperative Vancouver A PFFs were significantly higher in straight stem THA, while postoperative Vancouver B PFFs were significantly higher in short stem THA.
Conclusion
The morphology of the proximal femur and the pelvis do not differ in several radiological parameters in patients sustaining a PFF between cementless short stem implanted via an anterolateral approach and straight stem THA implanted via a transgluteal approach. While there are differences in the Vancouver types of PFFs, these differences do not reflect any difference in the morphology of the proximal femur and the pelvis.
Journal Article
Forensic differentiation between peripheral and menstrual blood in cases of alleged sexual assault—validating an immunochromatographic multiplex assay for simultaneous detection of human hemoglobin and D-dimer
Sexual assault is a serious offense and identification of body fluids originating from sexual activity has been a crucial aspect of forensic investigations for a long time. While reliable tests for the detection of semen and saliva have been successfully implemented into forensic laboratories, the detection of other body fluids, such as vaginal or menstrual fluid, is more challenging. Especially, the discrimination between peripheral and menstrual blood can be highly relevant for police investigations because it provides potential evidence regarding the issue of consent. We report the forensic validation of an immunochromatographic test that allows for such discrimination in forensic stains, the SERATEC PMB test, and its performance on real casework samples. The PMB test is a duplex test combining human hemoglobin and D-dimer detection and was developed for the identification of blood and menstrual fluid, both at the crime scene and in the laboratory. The results of this study showed that the duplex D-dimer/hemoglobin assay reliably detects the presence of human hemoglobin and identifies samples containing menstrual fluid by detecting the presence of D-dimers. The method distinguished between menstrual and peripheral blood in a swab from a historical artifact and in real casework samples of alleged sexual assaults. Results show that the development of the new duplex test is a substantial progress towards analyzing and interpreting evidence from sexual assault cases.
Journal Article
Failed Attempt to Recommend Noise Cancelling Headphones for Knee Arthroplasty Surgeons—Results of a Pilot Study
Background and Objectives: Noise exposure during total knee arthroplasty (TKA) has been demonstrated to exceed thresholds that are deemed as over-exposure by industry noise level standards. With orthopedic surgeons being at risk of suffering from Noise Induced Hearing Loss, the purpose of this pilot study was to evaluate the viability of the use of industry grade active noise cancelling headphones (ANCH) during TKA. Material and Methods: In this prospective pilot study, 10 TKA were performed. In five of these cases, surgeon, assistant, scrub nurse and anesthetist wore ANCH with automatic noise level dependent noise attenuation above 82 dB. A validated 14-item questionnaire was used after each case to evaluate the quality of communication, performance, teamwork and mental load. In seven cases a calibrated sound level meter was used to measure the operating theatre noise. Peak sound level (LApeak), A-weighted continuous sound level (LAeq) and A-weighted noise exposure averaged for an 8-h time-period (LEPd) were calculated. Results: There was no perceived benefit of ANCH for the surgeons (p = 0.648), assistants (p = 0.908) and scrub nurses (p = 0.251). There was an overall improvement observed by anesthetists (p = 0.001). A worse communication while wearing ANCH was reported by surgeons but not by the rest of the team. Average LApeak was 90.6 ± 3.2 dB(C), LAeq was 61.9 ± 1.0 dB(A) and LEPd was 53.2 ± 1.2 dB(A). Conclusions: Industry grade ANCH seem to provide no benefit for surgeons, assistants and scrub nurses during TKA, while anesthesiologists seem to benefit from the use of ANCH during TKA. Due to the limitations of this pilot study, further studies with larger study populations are necessary to adequately investigate the use of ANCH during TKA.
Journal Article