Publications by authors named "Rainer Burgkart"

113 Publications

In-house 3D-printed surgical guides for osseous lesions of the lower jaw: an experimental study.

Eur J Med Res 2021 Mar 15;26(1):25. Epub 2021 Mar 15.

Department of Oral and Maxillofacial Surgery, Kepler University Hospital GmbH, Johannes Kepler University Linz, Krankenhausstr. 9, 4021, Linz, Austria.

Background: The accuracy of computer-assisted biopsies at the lower jaw was compared to the accuracy of freehand biopsies.

Methods: Patients with a bony lesion of the lower jaw with an indication for biopsy were prospectively enrolled. Two customized bone models per patient were produced using a 3D printer. The models of the lower jaw were fitted into a phantom head model to simulate operation room conditions. Biopsies for the study group were taken by means of surgical guides and freehand biopsies were performed for the control group.

Results: The deviation of the biopsy axes from the planning was significantly less when using templates. It turned out to be 1.3 ± 0.6 mm for the biopsies with a surgical guide and 3.9 ± 1.1 mm for the freehand biopsies.

Conclusions: Surgical guides allow significantly higher accuracy of biopsies. The preliminary results are promising, but clinical evaluation is necessary.
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http://dx.doi.org/10.1186/s40001-021-00495-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7958719PMC
March 2021

Suspension button constructs restore posterior knee laxity in solid tibial avulsion of the posterior cruciate ligament.

Knee Surg Sports Traumatol Arthrosc 2021 Mar 6. Epub 2021 Mar 6.

Department of Sports Orthopaedic Medicine, Klinikum Rechts Der Isar, TU Munich, Ismaninger Str. 22, 81675, München, Germany.

Purpose: Dislocated tibial avulsions of the posterior cruciate ligament (PCL) require surgical intervention. Several arthroscopic strategies are options to fix the fragment and restore posterior laxity, including two types of suspension button devices: adjustable (self-locking) and rigid knotted systems. Our hypothesis was that a rigid knotted button construct has superior biomechanical properties regarding laxity restoration compared with an adjustable system. Both techniques were compared with standard screw fixation and the native PCL.

Methods: Sixty porcine knees were dissected. The constructs were tested for elongation, stiffness, yield force, load to failure force, and failure mode in a material testing machine. Group N (native, intact PCL) was used as a control group. In group DB (Dogbone™), TR (Tightrope™), and S (screw), a standardized block osteotomy with the osteotomized fragment attached to the PCL was set. The DB and TR groups simulated using a suspension button system with either a rigid knotted (DB) or adjustable system (TR). These groups were compared to a screw technique (S) simulating antegrade screw fixation from posterior.

Results: Comparing the different techniques (DB, TR, S), no significant elongation was detected; all techniques achieved a sufficient posterior laxity restoration. Significant elongation in the DB and TR group was detected compared with the native PCL (N). In contrast, screw fixation did not lead to significant elongation. The stiffness, yield load, and load to failure force did not differ significantly between the techniques. None of the techniques reached the same level of yield load and load to failure force as the intact state.

Conclusion: Arthroscopic suspension button techniques sufficiently restore the posterior laxity and gain a comparable construct strength as an open antegrade screw fixation.
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http://dx.doi.org/10.1007/s00167-021-06510-1DOI Listing
March 2021

Oncological Outcome and Prognostic Factors of Surgery for Soft Tissue Sarcoma After Neoadjuvant or Adjuvant Radiation Therapy: A Retrospective Analysis over 15 Years.

Anticancer Res 2021 Jan;41(1):359-368

Department of Orthopedics and Sports Orthopedics, Technical University of Munich, Klinikum rechts der Isar, Munich, Germany;

Background/aim: Surgical resection for soft tissue sarcomas (STSs) is the gold standard for a curative oncologic therapy in combination with neoadjuvant or adjuvant radiation therapy (NRT/ART). The aim of this study was to determine prognostic factors influencing the survival of patients with STS undergoing NRT or ART considering various parameters in a retrospective, single-centre analysis over 15 years.

Patients And Methods: We included 119 patients (male 59) and the median follow-up period was 69 months (4-197). The patients received NRT (n=64) or ART (n=55). We recorded the histopathologic subtype of STS, tumour grade, localization, tumour margins, complications, survival, local recurrence, and metastases. Survival analysis was performed using the Kaplan-Meier method.

Results: The overall survival rate was 68.9% at 5 years. The localization (epifascial/subfascial), resection margin and type of radiation therapy (NRT/ART) had no significant impact on survival. Tumour grade, tumour size, local recurrence and metastases were significantly correlated with patient survival (p<0.05). Local recurrence was significantly higher in patients with ART (p=0.044).

Conclusion: Tumour grade and tumour size were independently associated with disease-specific survival, and patients with local recurrence and metastases had lower survival rates.
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http://dx.doi.org/10.21873/anticanres.14784DOI Listing
January 2021

Thickness of the Stifle Joint Articular Cartilage in Different Large Animal Models of Cartilage Repair and Regeneration.

Cartilage 2020 Dec 3:1947603520976763. Epub 2020 Dec 3.

Experimental Rheumatology Unit, Department of Orthopedics, Jena University Hospital, Waldkliniken Eisenberg GmbH, Eisenberg, Germany.

Objective: Regulatory guidelines for preclinical cartilage repair studies suggest large animal models (e.g., sheep, goat, [mini]-pig, or horse) to obtain results representative for humans. However, information about the 3-dimensional thickness of articular cartilage at different implantation sites in these models is limited.

Design: To identify the most suitable site for experimental surgery, cartilage thickness at the medial femoral condyle (MFC), lateral femoral condyle (LFC), and trochlea in ovine, caprine, and porcine cadaver stifle joints was systematically measured using hematoxylin-eosin staining of 6 µm paraffin sections and software-based image analysis.

Results: Regarding all ventral-dorsal regions of the MFC, goat showed the thickest articular cartilage (maximal mean thickness: 1299 µm), followed by sheep (1096 µm) and mini-pig (604 µm), with the highest values in the most ventral and dorsal regions. Also for the LFC, the most ventral regions showed the thickest cartilage in goat (maximal mean thickness: 1118 µm), followed by sheep (678 µm) and mini-pig (607 µm). Except for the mini-pig, however, the cartilage thickness on the LFC was consistently lower than that on the MFC. The 3 species also differed along the transversal measuring points on the MFC and LFC. In contrast, there were no consistent differences for the regional cartilage thickness of the trochlea among goat and sheep (≥780 µm) and mini-pig (≤500 µm).

Conclusions: Based on their cartilage thickness, experimental defects on goat and sheep MFC may be viable options for preclinical cartilage repair studies, in addition to well-established horse models.
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http://dx.doi.org/10.1177/1947603520976763DOI Listing
December 2020

Cartilage T Relaxation Times and Subchondral Trabecular Bone Parameters Predict Morphological Outcome After Matrix-Associated Autologous Chondrocyte Implantation With Autologous Bone Grafting.

Am J Sports Med 2020 12 17;48(14):3573-3585. Epub 2020 Nov 17.

Department of Radiology, Klinikum Rechts der Isar, School of Medicine, Technical University of Munich, Munich, Germany.

Background: Quantitative magnetic resonance (MR) imaging techniques are established for evaluation of cartilage composition and trabecular bone microstructure at the knee. It remains unclear whether quantitative MR parameters predict the midterm morphological outcome after matrix-associated chondrocyte implantation (MACI) with autologous bone grafting (ABG).

Purpose: To assess longitudinal changes and associations of the biochemical composition of cartilage repair tissue, the subchondral bone architecture, and morphological knee joint abnormalities on 3-T MR imaging after MACI with ABG at the knee.

Study Design: Case series; Level of evidence, 4.

Methods: Knees of 18 patients (28.7 ± 8.4 years [mean ± SD]; 5 women) were examined preoperatively and 3, 6, 12, and 24 months after MACI and ABG using 3-T MR imaging. Cartilage composition was assessed using T relaxation time measurements. Subchondral bone microstructure was quantified using a 3-dimensional phase-cycled balanced steady-state free precision sequence. Trabecular bone parameters were calculated using a dual threshold algorithm (apparent bone fraction, apparent trabecular number, and apparent trabecular separation). Morphological abnormalities were assessed using the MOCART (magnetic resonace observation of cartilage repair tissue) score, the WORMS (Whole-Organ Magnetic Resonance Imaging Score), and the CROAKS (Cartilage Repair Osteoarthritis Knee Score). Clinical symptoms were assessed using the Tegner activity and Lysholm knee scores. Statistical analyses were performed by using multiple linear regression analysis.

Results: Total WORMS ( = .02) and MOCART ( = .001) scores significantly improved over 24 months after MACI. Clinical symptoms were significantly associated with the presence of bone marrow edema pattern abnormalities 24 months after surgery ( = .035). Overall there was a good to excellent radiological outcome found after 24 months (MOCART score, 88.8 ± 10.1). Cartilage repair T values significantly decreased between 12 and 24 months after MACI ( = .009). Lower global T values after 3 months were significantly associated with better MOCART scores after 24 months ( = .04). Moreover, trabecular bone parameters after 3 months were significantly associated with the total WORMS after 24 months (apparent bone fraction, = .048; apparent trabecular number, = .013; apparent trabecular separation, = .013).

Conclusion: After MACI with ABG, early postoperative quantitative assessment of biochemical composition of cartilage and microstructure of subchondral bone may predict the outcome after 24 months. The perioperative global joint cartilage matrix quality is essential for proper proliferation of the repair tissue, reflected by MOCART scores. The subchondral bone quality of the ABG site is essential for proper maturation of the cartilage repair tissue, reflected by cartilage T values.
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http://dx.doi.org/10.1177/0363546520965987DOI Listing
December 2020

Preoperative Evaluation of Myxofibrosarcoma: Prognostic Value and Reproducibility of Different Features on MRI.

Anticancer Res 2020 Oct;40(10):5793-5800

Department of Orthopaedics and Sports Orthopaedics, Technical University of Munich, Klinikum rechts der Isar, Munich, Germany

Background/aim: Myxofibrosarcoma (MFS) is characterized by an infiltrative growth pattern. This study aimed to determine the correlation between overall survival (OS) and morphological features of MFS as well as examine the reproducibility of these findings on preoperative magnetic resonance imaging (MRI).

Patients And Methods: Fifty-eight MFS patients underwent preoperative MR imaging with the following features analysed: i) tumour size, ii) localization, iii) margins, iv) morphology, v) signal characteristics, vi) contrast enhancement, vii) presence and extent of perilesional oedema, and viii) presence of the tail sign.

Results: Only circumscribed perilesional oedema was associated with a significantly better survival compared to diffuse oedema (p=0.010), which was found in the majority of cases. The tail sign was found in less than 50% of the cases. Cohen's kappa coefficients confirmed a relatively high interrater variability.

Conclusion: Perilesional diffuse oedema on MR imaging of MFS is significantly correlated with a poor overall survival. The interrater variability in interpretation of MR examinations varies from slight to substantial agreement. Preoperative MR imaging with detailed planning of the resection seem to be a logical approach to achieve negative resection margins and recurrence-free survival.
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http://dx.doi.org/10.21873/anticanres.14596DOI Listing
October 2020

Revision Arthroplasty Through the Direct Anterior Approach Using an Asymmetric Acetabular Component.

J Clin Med 2020 Sep 21;9(9). Epub 2020 Sep 21.

Department of Orthopaedic Surgery, University of Wuerzburg, Koenig-Ludwig-Haus, Brettreichstrasse 11, 97074 Wuerzburg, Germany.

Despite increasing numbers of primary hip arthroplasties performed through the direct anterior approach (DAA), there is a lack of literature on DAA revision arthroplasty. The present study was performed in order to evaluate outcomes and revision rates after revision through the DAA using an asymmetric acetabular component with optional intra- and extramedullary fixation. In a retrospective cohort study, we analyzed prospectively collected data of 57 patients (61 hips, 43 female, 18 male) who underwent aseptic acetabular component revision through the DAA with the abovementioned implant system between January 2015 and December 2017. The mean follow-up was 40 months (12-56). Survival rates were estimated using the Kaplan-Meier method. All complications were documented and functional outcomes were assessed pre- and postoperatively. Kaplan-Meier analysis revealed an estimated five-year implant survival of 97% (confidence interval CI 87-99%). The estimated five-year survival with revision for any cause was 93% (CI 83-98%). The overall revision rate was 6.6% (n = 4). Two patients had to undergo revision due to periprosthetic infection (3.3%). In one patient, the acetabular component was revised due to aseptic loosening four months postoperatively. Another patient suffered from postoperative iliopsoas impingement and was treated successfully by arthroscopic iliopsoas tenotomy. Two (3.3%) of the revised hips dislocated postoperatively. The mean Harris Hip Score improved from 35 (2-66) preoperatively to 86 (38-100) postoperatively ( < 0.001). The hip joint's anatomical center of rotation was restored at a high degree of accuracy. Our findings demonstrate that acetabular revision arthroplasty through the DAA using an asymmetric acetabular component with optional intra- and extramedullary fixation is safe and practicable, resulting in good radiographic and clinical midterm results.
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http://dx.doi.org/10.3390/jcm9093031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7564155PMC
September 2020

Antimicrobial peptides in human synovial membrane as (low-grade) periprosthetic joint infection biomarkers.

Eur J Med Res 2020 Aug 17;25(1):33. Epub 2020 Aug 17.

Clinic of Orthopedics and Sports Orthopedics, Klinikum rechts der Isar, Technical University of Munich, Ismaninger Strasse 22, 81675, Munich, Germany.

Background: Safe diagnosis of periprosthetic joint infection (PJI) is of utmost importance for successful exchange arthroplasty. However, current diagnostic tools show insufficient accuracy in the clinically common and challenging chronic low-grade infections. To close this diagnostic gap, reliable (bio)markers display the most promising candidates. Antimicrobial peptides (AMPs) are part of the innate immune response towards microbial growth. Recently we could show significant intraarticular levels of human cathelicidin LL-37 and β-defensin-3 (HBD-3) with high diagnostic accuracy in PJI synovial fluid. Consequently, these promising biomarkers were evaluated in PJI synovial membrane and synoviocytes, which may significantly facilitate histological diagnosis of PJI to improve outcome of septic joint replacement.

Methods: In this prospective single-center controlled clinical study (diagnostic level II), consecutive patients with total hip (THR) and knee (TKR) replacements were included undergoing primary arthroplasty (n = 8), surgical revision due to aseptic loosening (n = 9) and septic arthroplasty with coagulase-negative staphylococci (n = 8) according to the criteria of the Musculoskeletal Infection Society (MSIS). Semiquantitative immunohistochemical (IHC) analysis of LL-37, HBD-3 and HBD-2 in synovial membrane and isolated synoviocytes based on Total Allred Score (TS) and Immunoreactive Remmele and Stegner score (IRS) was performed. For statistical analysis, SPSS 26.0/R3.6.3 (p < 0.05) was used.

Results: The AMPs LL-37 and HBD-3 were significantly elevated (up to 20×) in synovial membranes from PJI compared to aseptic loosening or primary arthroplasty. The area under the curve (AUC) in a receiver operating characteristic curve analysis was equal to 1.0 for both scores revealing excellent diagnostic accuracy. Isolated synoviocytes as cellular AMP source showed comparable results with a significant LL-37/HBD-3-increase up to 3 × in PJI. In contrast, local HBD-2 levels were negligible (p > 0.23) upon PJI with a lower diagnostic accuracy (AUC = 0.65) in analogy to our previous findings with synovial fluid.

Conclusions: Our results implicate AMPs as promising and specific biomarkers for the histological diagnosis of PJI.
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http://dx.doi.org/10.1186/s40001-020-00434-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7429885PMC
August 2020

Effects of focal metallic implants on opposing cartilage - an in-vitro study with an abrasion test machine.

BMC Musculoskelet Disord 2020 Apr 21;21(1):261. Epub 2020 Apr 21.

Department of Orthopaedic Sports Medicine, Klinikum rechts der Isar, Technische Universität München, Ismaninger Str. 22, 81675, Munich, Germany.

Background: For focal cartilage defects, biological repair might be ineffective in patients over 45 years. A focal metallic implant (FMI) (Hemi-CAP Arthrosurface Inc., Franklin, MA, USA) was designed to reduce symptoms. The aim of this study was to evaluate the effects of a FMI on the opposing tibial cartilage in a biomechanical set-up. It is hypothesized that a FMI would not damage the opposing cartilage under physiological loading conditions.

Methods: An abrasion machine was used to test the effects of cyclic loading on osteochondral plugs. The machine applied a compressive load of 33 N and sheared the samples 10 mm in the anteroposterior direction by 1 Hz. Tibial osteochondral plugs from porcine knees were placed in opposition to a FMI and cycled for 1 or 6 h. After testing each plug was fixed, stained and evaluated for cartilage damage.

Results: After 1 h of loading (n = 6), none of the osteochondral plugs showed histologic signs of degradation. After 6 h of loading (n = 6) three samples had histologic signs of injury in the tangential zone (grade 1) and one had signs of injury in the transitional and deep zones (grade 2). Exploration for 6 h resulted in significant more cartilage damage compared to the shorter exploration time (p = 0.06). However, no significant difference between saline and hyaluronic acid was evident (p = 0.55).

Conclusion: Under physiologic loading conditions, contact with a FMI leads to cartilage damage in the opposing articular cartilage in six hours. In clinical practice, a thorough analysis of pre-existing defects on the opposing cartilage is recommended when FMI is considered.
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http://dx.doi.org/10.1186/s12891-020-03292-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7175572PMC
April 2020

Peri-Prosthetic Joint Infection of the Knee Causes High Levels of Psychosocial Distress: A Prospective Cohort Study.

Surg Infect (Larchmt) 2020 Dec 13;21(10):877-883. Epub 2020 Apr 13.

Klinikum rechts der Isar, Clinic for Orthopaedic and Sportorthopaedic, Technical University of Munich, School of Medicine, Munich, Germany.

Peri-prosthetic joint infection (PJI) is a major complication of knee arthroplasty that can cause long-term disability. In addition to its physical impact, there is a clear psychological burden that has not been measured yet. We hypothesized that the psychosocial burden of PJI can be assessed quantitatively using standardized questionnaires and may be correlated with treatment stage. Thirty-one patients were enrolled in this longitudinal prospective cohort study from August 2015 to November 2016. Participants had clinically established knee PJI after primary total knee replacement in osteoarthritis according to the Musculoskeletal Infection Society criteria and underwent a standardized two-stage protocol. After explantation of the prosthesis and implantation of a polymethylmethacrylate knee spacer, patients were treated with organism-specific intravenous antibiotics for two weeks, followed by oral antibiotics for four weeks; and then reimplantation was performed in all cases. Psychometrically validated standardized questionnaires were used to measure psychosocial stress via self-assessment at four time points: (1) Before explantation of the prosthesis; (2) after explantation; (3) after the antibiotic treatment before reimplantation; and (4) three months after reimplantation (follow-up). The Patient Health Questionnaire (PHQ)-4, Short Form (SF)-12 (including PSK and KSK), Questions about Life Satisfaction (FLZ) and Fear of Progression (PA-F-KF) (titles and abbreviations in German) scores were interpreted according to cut-off values for depression, fear of progression, anxiety, and quality of life. Eighteen patients (58.1%) showed a PHQ-4 score above the cut-off value for depression at least once, with the highest score before reimplantation (time point 3). On the SF-12, the mean subtest mental scale (PSK) score was 42.6 (± 14.5), and the mean subtest physical scale (KSK) score was 26.9 (± 7.5) over the four time points, which was significantly lower than that of the general German population (PSK 53.1, KSK 44.0; p < 0.05). The SF-12 scores did not change significantly over time. On the FLZ, health was least satisfactory, followed by recreational activities and work. On the PA-F-KF, patients had the greatest fear of being dependent on outside help, drastic medical interventions, and infection progression. The mean PA-F-KF value was 31.24 (± 9.60; values ≥34 are regarded as critical). Peri-prosthetic joint infection is a measurable, relevant psychosocial stressor for patients. Their quality of life and fear of the disease progressing are comparable to those of oncology patients. Routine screening should be conducted to identify affected patients early for appropriate treatment, improving long-term outcomes. Orthopaedic surgeons who treat patients with PJI should initiate by psychologists as well in order to maintain the patient's long-term quality of life.
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http://dx.doi.org/10.1089/sur.2019.368DOI Listing
December 2020

Polydioxanone Threads for Facial Rejuvenation: Analysis of Quality Variation in the Market.

Plast Reconstr Surg 2019 12;144(6):1002e-1009e

From the Departments of Plastic Surgery and Hand Surgery and Orthopedics and Sportsorthopaedics, Klinikum rechts der Isar, Technische Universität München; the Biotechnology Research Center, Costa Rica Institute of Technology; the College of Pharmacy, University of Florida; and the Section for Plastic and Reconstructive Surgery, Kepler University Hospital.

Background: Beside botulinum-toxin injections and hyaluronic acid fillers, thread lifts have established themselves as the third column of minimally invasive facial rejuvenation. Most commonly, barbed threads for this approach are made out of polydioxanone, a material known for decades from application in resorbable sutures. The clinical efficacy and the putative material safety of polydioxanone have fueled the popularity of thread lifts.

Methods: The present study highlights significant variation among six commercially available threads in microstructure, tensile strength, elasticity, anchoring capacity in human tissue, and biocompatibility.

Results: Despite their license to be marketed and sold in the European Union, some products performed significantly worse than others on material testing, and even displayed cytotoxic characteristics.

Conclusion: The results of this study are highly relevant for clinicians and may be linked to various typical side effects of polydioxanone threads for facial rejuvenation.
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http://dx.doi.org/10.1097/PRS.0000000000006289DOI Listing
December 2019

Smart antimicrobial efficacy employing pH-sensitive ZnO-doped diamond-like carbon coatings.

Sci Rep 2019 11 21;9(1):17246. Epub 2019 Nov 21.

Chair for Experimental Physics 1, University of Augsburg, Augsburg, 86159, Germany.

One of the main challenges in endoprosthesis surgeries are implant-associated infections and aseptic-loosenings, caused by wear debris. To combat these problems, the requirements to surfaces of endoprostheses are wear-resistance, low cytotoxicity and antimicrobial efficacy. We here present antimicrobial coatings with a smart, adaptive release of metal ions in case of infection, based on ZnO-nanoparticles embedded in diamond-like carbon (DLC). The Zn ion release of these coatings in aqueous environments reacts and adapts smartly on inflammations accompanied by acidosis. Moreover, we show that this increased ion release comes along with an increased toxicity to fibroblastic cells (L929) and bacteria (Staphylococcus aureus subsp. aureus, resistant to methicillin and oxacillin. (ATCC 43300, MRSA) and Staphylococcus epidermidis (ATCC 35984, S. epidermidis). Interestingly, the antimicrobial effect and the cytotoxicity of the coatings increase with a reduction of the pH value from 7.4 to 6.4, but not further to pH 5.4.
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http://dx.doi.org/10.1038/s41598-019-53521-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6872652PMC
November 2019

Bioactive coating of zirconia toughened alumina ceramic implants improves cancellous osseointegration.

Sci Rep 2019 11 13;9(1):16692. Epub 2019 Nov 13.

Julius Wolff Institut, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.

Bioactive coatings have the potential to improve the bony integration of mechanically loaded orthopedic ceramic implants. Using the concept of mimicking the natural bone surface, four different coatings of varying thickness on a zirconia toughened alumina (ZTA) ceramic implant were investigated regarding their osseointegration in a drill-hole model in sheep. The hypothesis that a bioactive coating of ZTA ceramics would facilitate cancellous bone integration was investigated. The bioactive coatings consisted of either a layer of covalently bound multi phosphonate molecules (chemical modification = CM), a nano hydoxyapatite coating (HA), or two different bioactive glass (BG) coatings in micrometer thickness, forming a hydroxyl-carbonate apatite layer on the implant surface in vivo (dip-coated 45S5 = DipBG; sol-gel 70S30C = SGBG). Coated surfaces were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. After 12 weeks, osseointegration was evaluated via mechanical push-out testing and histology. HA enhanced the maximum push-out force (HA: mean 3573.85 ± 1119.91 N; SGBG: mean 1691.57 ± 986.76 N; p = 0.046), adhesive shear strength (HA: mean 9.82 ± 2.89 MPA; SGBG: mean 4.57 ± 2.65 MPA; p = 0.025), and energy release rate (HA: mean 3821.95 ± 1474.13 J/mm; SGBG: mean 1558.47 ± 923.47 J/mm; p = 0.032) compared to SGBG. The implant-bone interfacial stiffness increased by CM compared to SGBG coating (CM: mean 6258.06 ± 603.80 N/mm; SGBG: mean 3565.57 ± 1705.31 n/mm; p = 0.038). Reduced mechanical osseointegration of SGBG coated implants could be explained histologically by a foreign body reaction surrounding the implants.
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http://dx.doi.org/10.1038/s41598-019-53094-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6853946PMC
November 2019

Modified suture-bridge technique for tibial avulsion fractures of the posterior cruciate ligament: a biomechanical comparison.

Arch Orthop Trauma Surg 2020 Jan 26;140(1):59-65. Epub 2019 Sep 26.

Department of Orthopaedic Sports Medicine, Klinikum Rechts Der Isar, Technical University Munich, Ismaningerstr. 22, 81675, Munich, Germany.

Purpose: Displaced tibial posterior cruciate ligament (PCL) avulsion fractures require surgical fixation in order to provide an adequate bone healing and to avoid a loss of posterior stability. The purpose of this study was to compare the biomechanical properties of a recently established modified suture bridge technique to a well-established transtibial pullout technique. It was hypothesized that the suture bridge technique shows lower elongation and higher load to failure force compared to a transtibial pullout fixation.

Methods: Twelve fresh-frozen human cadaveric knees were biomechanically tested using an uniaxial hydrodynamic material testing system. A standardized bony avulsion fracture of the tibial PCL insertion was generated. Two different techniques were used for fixation: (A) suture bridge configuration and (B) transtibial pullout fixation. In 90° of flexion elongation, initial stiffness and failure load were determined.

Results: The suture-bridge technique resulted in a significant lower elongation (4.5 ± 2.1 mm) than transtibial pullout technique (12.4 ± 3.0 mm, p < 0.001). The initial stiffness at the beginning of cyclic loading was 46.9 ± 3.9 N/mm in group A und 40.8 ± 9.0 N/mm in group B (p = 0.194). Load to failure testing exhibited 286.8 ± 88.3 N in group A and 234.3 ± 96.8 N in group B (p = 0.377).

Conclusion: The suture bridge technique provides a significant lower construct elongation during cyclic loading. But postoperative rehabilitation must respect the low construct strength of both techniques because both fixation techniques did not show a sufficient fixation strength to allow for a more aggressive rehabilitation.
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http://dx.doi.org/10.1007/s00402-019-03278-5DOI Listing
January 2020

Why hand hygiene is not sufficient: modeling hygiene competence of clinical staff as a basis for its development and assessment.

GMS J Med Educ 2019 15;36(4):Doc39. Epub 2019 Aug 15.

Technical University of Munich, School of Medicine, Klinikum rechts der Isar, TUM Medical Education Center, Munich, Germany.

Adhering to hygiene standards in daily clinical work is an important characteristic of qualitatively high-value medical care. In this regards, hand hygiene is often focused on in the literature. From the viewpoint of medical education research, we argue that this focus is too narrow to explain how staff who are working clinically with patients implement and adhere to standards of hygiene across a wide variety of tasks of their daily clinical routine. We present basic features of a differentiated concept of , which includes specialized knowledge, corresponding inner attitudes, and action routines that are customized to the needs of specific situations. Building on that, we present a current simulation-based course concept aimed at developing hygiene competence in medical education. Furthermore, we describe a test instrument that is designed according to the principle of a and that appears promising for the assessment of hygiene competence. The course and the measurement instrument are discussed in regards to their fit to the competence model and the related perspectives for research and teaching.
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http://dx.doi.org/10.3205/zma001247DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6737265PMC
February 2020

Varus alignment increases medial meniscus extrusion and peak contact pressure: a biomechanical study.

Knee Surg Sports Traumatol Arthrosc 2020 Apr 5;28(4):1092-1098. Epub 2019 Sep 5.

Department of Orthopaedic Sports Medicine, Hospital Rechts Der Isar, Technical University of Munich, Ismaningerstr. 22, 81675, Munich, Germany.

Purpose: Assessment of medial meniscus extrusion (MME) has become increasingly popular in clinical practice to evaluate the dynamic meniscus function and diagnose meniscus pathologies. The purpose of this biomechanical study was to investigate the correlation between MME and the changes in joint contact pressure in varus and valgus alignment. It was hypothesized that varus alignment would result in significantly higher MME along with a higher joint contact pressure in the medial compartment.

Methods: Eight fresh-frozen human cadaveric knees were axially loaded, with a 750 N compressive load, in full extension with the mechanical axis shifted to intersect the tibial plateau at 30% and 40% (varus), 50% (neutral), 60% and 70% (valgus) of its width (TPW). Tibiofemoral peak contact pressure (PCP), mean contact pressure (MCP) and contact area (CA) were determined using pressure-sensitive films. MME was obtained via ultrasound at maximum load.

Results: MME was significantly increased from valgus (1.32 ± 0.22 mm) to varus alignment (3.16 ± 0.24 mm; p < 0.001). Peak contact pressure at 30% TPW varus alignment was significantly higher compared to 60% TPW valgus (p = 0.018) and 70% TPW valgus (p < 0.01). MME significantly correlated with PCP (r = 0.56; p < 0.001) and MCP (r = 0.47, p < 0.01) but not with CA (r = 0.23; n.s.).

Conclusion: MME was significantly increased in varus alignment, compared to neutral or valgus alignment, with an intact medial meniscus. It was also significantly correlated with PCP and MCP within the medial compartment. However, valgus malalignment and neutral axis resulted in reduced MME and contact pressure. Lower limb alignment must be taken into account while assessing MME in clinical practice.

Level Of Evidence: Controlled laboratory study.
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http://dx.doi.org/10.1007/s00167-019-05701-1DOI Listing
April 2020

Integrated additive design and manufacturing approach for the bioengineering of bone scaffolds for favorable mechanical and biological properties.

Biomed Mater 2019 09 9;14(6):065002. Epub 2019 Sep 9.

Experimental Trauma Surgery, Technical University of Munich, Ismaninger Str. 22, D-81675 Munich, Germany.

Additive manufacturing (AM) presents the possibility of personalized bone scaffolds with unprecedented structural and functional designs. In contrast to earlier conventional design concepts, e.g. raster-angle, a workflow was established to produce scaffolds with triply periodic minimal surface (TPMS) architecture. A core challenge is the realization of such structures using melt-extrusion based 3D printing. This study presents methods for generation of scaffold design files, finite element (FE) analysis of scaffold Young's moduli, AM of scaffolds with polycaprolactone (PCL), and a customized in vitro assay to evaluate cell migration. The reliability of FE analysis when using computer-aided designed models as input may be impeded by anomalies introduced during 3D printing. Using micro-computed tomography reconstructions of printed scaffolds as an input for numerical simulation in comparison to experimentally obtained scaffold Young's moduli showed a moderate trend (R  = 0.62). Interestingly, in a preliminary cell migration assay, adipose-derived mesenchymal stromal cells (AdMSC) migrated furthest on PCL scaffolds with Diamond, followed by Gyroid and Schwarz P architectures. A similar trend, but with an accelerated AdMSC migration rate, was observed for PCL scaffolds surface coated with calcium-phosphate-based apatite. We elaborate on the importance of start-to-finish integration of all steps of AM, i.e. design, engineering and manufacturing. Using such a workflow, specific biological and mechanical functionality, e.g. improved regeneration via enhanced cell migration and higher structural integrity, may be realized for scaffolds intended as temporary guiding structures for endogenous tissue regeneration.
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http://dx.doi.org/10.1088/1748-605X/ab38c6DOI Listing
September 2019

Varus alignment aggravates tibiofemoral contact pressure rise after sequential medial meniscus resection.

Knee Surg Sports Traumatol Arthrosc 2020 Apr 3;28(4):1055-1063. Epub 2019 Aug 3.

Department of Orthopedics and Sports Orthopedics, Technical University of Munich, Hospital Rechts der Isar, Munich, Germany.

Purpose: Arthroscopic partial meniscectomy of medial meniscus tears and varus alignment are considered independent risk factors for increased medial compartment load, thus contributing to the development of medial osteoarthritis. The purpose of this biomechanical study was to investigate the effect of lower limb alignment on contact pressure and contact area in the knee joint following sequential medial meniscus resection. It was hypothesized that a meniscal resection of 50% would lead to a significant overload of the medial compartment in varus alignment.

Methods: Eight fresh-frozen human cadaveric knees were axially loaded with a 750 N compressive force in full extension with the mechanical axis rotated to intersect the tibia plateau at 30%, 40%, 50%, 60% and 70% of its width. Tibiofemoral mean contact pressure (MCP), peak contact pressure (PCP), and contact area (CA) of the medial and lateral compartment were measured separately using pressure-sensitive films (K-Scan 4000, Tekscan) in four different meniscal conditions, respectively, intact, 50% resection, 75% resection, and total meniscectomy.

Results: Medial MCP was significantly increased when comparing the intact meniscus to each meniscal resection in all tested alignments (p < 0.05). Following meniscal resection of 50%, MCP was significantly higher with greater varus alignment compared to valgus alignment (p < 0.05). Similarly, medial PCP was higher at varus alignment compared to valgus alignment (p < 0.05). Further resection to 75% and 100% of the meniscus resulted in a significantly higher medial PCP at 30% of tibia plateau width compared to all other alignments (p < 0.05). Medial CA of the intact meniscus decreased significantly after 50%, 75% and 100% meniscal resection in all alignments (p < 0.05). Lateral joint pressure was not significantly increased by greater valgus alignment.

Conclusion: Lower limb alignment and the extent of medial meniscal resection significantly affect tibiofemoral contact pressure. Combined varus alignment and medial meniscal resection increased MCP and PCP within the medial compartment, whereas valgus alignment prevented medial overload. As a clinical consequence, lower limb alignment should be considered in the treatment of patients undergoing arthroscopic partial meniscectomy with concomitant varus alignment. In patients presenting with ongoing medial joint tenderness and effusion, realignment osteotomy can be a surgical technique to unload the medial compartment.
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http://dx.doi.org/10.1007/s00167-019-05654-5DOI Listing
April 2020

Modern Total Knee Arthroplasty (TKA): With Or Without a Tourniquet?

Surg Technol Int 2019 11;35:336-340

Charité-University Medicine Berlin, Center of Joint Replacement, OCM/SANA Campus Munich, Munich, Germany.

Background: Since arthritis of the knee is one of the most common pathologies in industrialized nations, there has been a growing interest in fast-track total knee arthroplasty (TKA). However, while one of the main concerns is the role of a tourniquet, the available data are inconclusive.

Aim: This study sought to assess the link between postoperative outcomes and use of a tourniquet in TKA. Our goal was to determine whether it is justified to forego tourniquet use as indicated by the fast-track concept.

Methods: The participants (n = 108) in this retrospective, non-randomized study were assigned into two groups after they satisfied the inclusion criteria: primary gonarthrosis or secondary gonarthrosis without previous arthrotomy. TKA was performed without (Group I, n = 55) or with (Group II, n = 53) a tourniquet. The postoperative outcome was evaluated in terms of postoperative pain, based on a numeric rating scale (NRS) and the need for pain medication, and postoperative function, based on range of motion (ROM) and walking tests.

Results: Overall, no significant correlations were observed between tourniquet use and postoperative pain according to the NRS. Group I required less oxycodone, but more non-opioids. There was no significant difference in the improvement in pre- to postoperative ROM with regard to tourniquet use. The final walking distance was significantly longer in Group I.

Conclusions: These results suggest that there is no strongly significant link between the postoperative outcome and the use of a tourniquet. However, further studies will be needed to determine whether a tourniquet may have some other impact on TKA.
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November 2019

Prognostic Factors and Outcomes for Patients With Myxofibrosarcoma: A 13-Year Retrospective Evaluation.

Anticancer Res 2019 Jun;39(6):2985-2992

Department of Orthopaedic Surgery, Rechts der Isar Hospital, Technical University of Munich, Munich, Germany.

Background: Soft-tissue sarcomas are rare entities that are divided into approximately 50 histological subtypes. Myxofibrosarcoma (MFS) represents approximately 20% of all soft-tissue sarcomas, especially in elderly patients in their sixth to eighth decades of life. The treatment for soft-tissue sarcomas varies from primary surgical resection to neoadjuvant or adjuvant radiotherapy or cytotoxic chemotherapy. The aim of this study was to evaluate the prognostic factors affecting survival of patients with MFS, taking into account gender, tumour grade, state of the resection margin, local recurrence, use of radiotherapy, presence of metastases and blood levels of haemoglobin and C-reactive protein in a retrospective, single-centre analysis with a minimum follow-up period of 60 months (range=60-156 months).

Patients And Methods: The study included 34 patients (male/female=20/14). Tumour localization, tumour grade, tumour margins, local recurrence, the use of radiotherapy, the presence of metastasis, and the blood levels of haemoglobin and C-reactive protein preoperatively and during follow-up were evaluated.

Results: MFS constituted the most common high-grade sarcoma (G2/G3, 79.4%) in our cohort and was generally located in a lower limb (73.6%). Negative margins (R0) were detected in 67.6% of patients after surgical resection, and local recurrence occurred in 23.5% of all patients after a mean disease-free period of 19.4 months. Both parameters exerted no significant influence on survival. Radiotherapy was performed in a neoadjuvant or an adjuvant setting in 50% of patients (eight neoadjuvant, nine adjuvant). Metastasis occurred after a mean of 20.4 months in 38.2% of the patients. Higher C-reactive protein levels showed a trend towards being associated with worse survival, but the association was not significant (p=0.084); haemoglobin level had no influence on the survival rate (p=0.426). Tumour grade and metastasis were significant prognostic factors of survival (log-rank test p=0.041 and p=0.00007). Ten patients (29.4%) died due to MFS during our follow-up period.

Conclusion: The tumour grade and metastasis of MFS are independently associated with disease-specific survival, whereas negative surgical margins, local recurrence and blood levels of C-reactive protein and haemoglobin were not significant prognostic factors. The understanding of the molecular biological patterns that result in the metastasis of these tumours will help develop better treatment plans in the future.
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http://dx.doi.org/10.21873/anticanres.13430DOI Listing
June 2019

Tracking Stem Cell Implants in Cartilage Defects of Minipigs by Using Ferumoxytol-enhanced MRI.

Radiology 2019 07 7;292(1):129-137. Epub 2019 May 7.

From the Department of Radiology and Molecular Imaging Program at Stanford (MIPS) (A.J.T., H.N., O.L., K.Y., K.L., L.K., C.W., T.L., H.E.D.), Department of Comparative Medicine (S.F.), and Department of Pediatrics (H.E.D.), Stanford University School of Medicine, 725 Welch Rd, Room 1665, Stanford, CA 94305-5654; Department of Diagnostic and Interventional Radiology, University Medical Center Mainz, Mainz, Germany (A.J.T.); and Department of Orthopedics and Sportorthopedics, Klinikum Rechts der Isar, Technical University of Munich, Munich, Germany (L.K., J.T., R.B.).

Background Cartilage repair outcomes of matrix-associated stem cell implants (MASIs) in patients have been highly variable. Conventional MRI cannot help distinguish between grafts that will and grafts that will not repair the underlying cartilage defect until many months after the repair. Purpose To determine if ferumoxytol nanoparticle labeling could be used to depict successful or failed MASIs compared with conventional MRI in a large-animal model. Materials and Methods Between January 2016 and December 2017, 10 Göttingen minipigs ( = 5 male; = 5 female; mean age, 6 months ± 5.1; age range, 4-20 months) received implants of unlabeled ( = 12) or ferumoxytol-labeled ( = 20) viable and apoptotic MASIs in cartilage defects of the distal femur. All MASIs were serially imaged with MRI on a 3.0-T imaging unit at week 1 and weeks 2, 4, 8, 12, and 24, with calculation of T2 relaxation times. Cartilage regeneration outcomes were assessed by using the MR observation of cartilage repair tissue (MOCART) score (scale, 0-100), the Pineda score, and histopathologic quantification of collagen 2 production in the cartilage defect. Findings were compared by using the unpaired Wilcoxon rank sum test, a linear regression model, the Fisher exact test, and Pearson correlation. Results Ferumoxytol-labeled MASIs showed significant T2 shortening (22.2 msec ± 3.2 vs 27.9 msec ± 1.8; < .001) and no difference in cartilage repair outcomes compared with unlabeled control MASIs ( > .05). At week 2 after implantation, ferumoxytol-labeled apoptotic MASIs showed a loss of iron signal and higher T2 relaxation times compared with ferumoxytol-labeled viable MASIs (26.6 msec ± 4.9 vs 20.8 msec ± 5.3; = .001). Standard MRI showed incomplete cartilage defect repair of apoptotic MASIs at 24 weeks. Iron signal loss at 2 weeks correlated with incomplete cartilage repair, diagnosed at histopathologic examination at 12-24 weeks. Conclusion Ferumoxytol nanoparticle labeling can accelerate the diagnosis of successful and failed matrix-associated stem cell implants at MRI in a large-animal model. © RSNA, 2019 See also the editorial by Sneag and Potter in this issue.
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http://dx.doi.org/10.1148/radiol.2019182176DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6614913PMC
July 2019

Full biomechanical mapping of the ovine knee joint to determine creep-recovery, stiffness and thickness variation.

Clin Biomech (Bristol, Avon) 2019 07 24;67:1-7. Epub 2019 Apr 24.

Department of Orthopaedics and Sports Orthopaedics, Klinikum rechts der Isar, Technical University of Munich, Ismaninger Straße 22, 81675 Munich, Germany.

Background: Clinical cartilage repair strategies can be tested using the sheep model as suggest by the European Medicines Agency. To characterize variation within the joint a full biomechanical mapping is necessary. The aim of this study is to establish a loading model, to map regional differences within the knee and determine reference areas for area specific replacement techniques.

Methods: A porous indenter was selected to evaluate 22 defined test locations (femoral condyles, tibia plateau, patella, femoral groove) on ovine knees (n = 7). A high-dynamic force-controlled micro creep and creep-recovery indentation test system applied five loading (0.11 MPa) and unloading (5.6 kPa) cycles for 60 s each and recorded creep-recovery. Needle indentation was used to measure cartilage thickness and calculate total strain.

Findings: Steady state behaviour was observed from the third cycle and further evaluated. Little variation of stiffness in N/mm was found within the patella (4.3SD0.5) and femoral groove (8.1SD0.7) compared to larger variations in the femur (7.9SD2.0) and tibia (7.5SD3.2). Creep indentation showed values of 14.5%(SD2.7%) for the patella and 17.4%(SD3%) for the femoral grove opposed to 13.4%(SD4.3%) for the femoral condyles and 21.8%(SD6.6%) for the tibia plateau. Similar trends were observed analysing creep-recovery. Values were normalized to cartilage thickness which ranged between 0.36 mm and 1.14 mm.

Interpretation: Our setup allows a reliable evaluation of zonal differences. Homogenous biomechanical behaviour is found within the patella and femoral groove whereas significant biomechanical variation within the femoral condyles and tibia plateau indicates the need for site-specific cartilage repair products.
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http://dx.doi.org/10.1016/j.clinbiomech.2019.04.015DOI Listing
July 2019

Novel antimicrobial coatings based on polylactide for plastic biliary stents to prevent post-endoscopic retrograde cholangiography cholangitis.

J Antimicrob Chemother 2019 07;74(7):1911-1920

Klinik und Poliklinik für Innere Medizin II, Klinikum rechts der Isar der Technischen Universität München, München, Germany.

Background: Cholangitis is a common complication after endoscopic retrograde cholangiography (ERC).

Objectives: To evaluate antimicrobial coatings for biliary plastic stents in relation to efficacy against biliary pathogens, drug release and toxicity.

Methods: Biliary plastic stents were prepared by coating using a polylactide drug carrier. Stent coatings contained 4% (w/w) drug content of Resomer-octenidine (RO), Resomer-octenidine and citrate (ROC), Resomer-triclosan (RT) or Resomer-gentamicin (RG). Drug-release kinetics, antimicrobial efficacies of coated biliary stents against biliary pathogens and biocompatibilities were tested. Antimicrobial efficacy measurements included MIC testing, zone of inhibition (ZOI) assays and log reduction in bacterial suspensions.

Results: Continuous drug release was observed in all antimicrobial stent coatings for at least 168 h with an initial peak within the first 24 h. RT-, ROC- and RG-coated stents resulted in the following log reductions in suspensions: Escherichia coli (-0.3, -7.4 and -6.6, respectively); Enterococcus faecalis (-0.05, -6.3 and -3.9, respectively); and Candida albicans (-0.04, -1.5 and -0.2, respectively). ROC had the highest log reduction in suspension and the most favourable time course of ZOI (≥2 mm, over 72 h) against all tested pathogens. Although RT coatings showed the lowest MICs, they had the lowest ZOIs after 24 h. Concerning RO, acceptable biocompatibility could only be reached by adding a citrate component. RG showed the largest ZOI after 24 h against E. coli (19.3 mm) and E. faecalis (5.1 mm), whereas the ZOI was lower against C. albicans (1.3 mm) compared with ROC (3.7 mm).

Conclusions: ROC corresponds most closely to the requirements of an ideal antimicrobial stent coating to prevent post-ERC cholangitis, showing the highest log reduction in pathogen counts, the most favourable time course of ZOI and high biocompatibility.
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http://dx.doi.org/10.1093/jac/dkz128DOI Listing
July 2019

Effect of Lower Limb Alignment in Medial Meniscus-Deficient Knees on Tibiofemoral Contact Pressure.

Orthop J Sports Med 2019 Feb 6;7(2):2325967118824611. Epub 2019 Feb 6.

Department of Orthopedics and Sports Orthopedics, Rechts der Isar Hospital, Technical University of Munich, Munich, Germany.

Background: Degenerative medial meniscal tears and subsequent partial meniscal resection compromise meniscal function and lead to an overload of the medial compartment. In addition, lower limb alignment plays a key role in load distribution between the medial and lateral knee compartments, and varus alignment is a potential risk factor for medial osteoarthritis.

Purpose/hypothesis: The purpose of this biomechanical study was to investigate the effect of valgus and varus alignment on peak pressure and contact area in knees with concomitant horizontal medial meniscal tears and subsequent leaflet resection. It was hypothesized that varus alignment in combination with meniscal loss leads to the highest peak pressure within the medial compartment.

Study Design: Controlled laboratory study.

Methods: Six fresh-frozen human cadaveric knees were axially loaded using a 1000-N compressive load in full extension with the mechanical axis rotated to intersect the tibial plateau at 40%, 45%, 50%, 55%, and 60% of its width (TPW) to simulate varus and valgus alignment. Tibiofemoral peak contact pressure and contact area of the medial and lateral compartments were determined using pressure-sensitive foils in each of 4 different meniscal conditions: intact, 15-mm horizontal tear of the posterior horn, inferior leaflet resection, and resection of both leaflets.

Results: The effect of alignment on peak pressure (normalized to the neutral axis) within the medial compartment in cases of an intact meniscus was measured as follows: varus shift resulted in a mean increase in peak pressure of 18.5% at 45% of the TPW and 37.4% at 40% of the TPW, whereas valgus shift led to a mean decrease in peak pressure of 8.7% at 55% of the TPW and 23.1% at 60% of the TPW. Peak pressure changes between the intact meniscus and resection within the medial compartment was less in valgus-aligned knees (0.21 MPa at 60% TPW, 0.59 MPa at 50% TPW, and 0.76 MPa at 40% TPW). Contact area was significantly reduced after partial meniscal resection in the neutral axis (intact, 553.5 ± 87.6 mm; resection of both leaflets, 323.3 ± 84.2 mm; < .001). This finding was consistent in any alignment.

Conclusion: Both partial medial meniscal resection and varus alignment led to an increase in medial compartment peak pressure. Valgus alignment prevented medial overloading by decreasing contact pressure even after partial meniscal resection. A horizontal meniscal tear did not influence peak pressure and contact area even in varus alignment.

Clinical Relevance: As a clinical consequence, partial meniscal resection should be avoided to maintain the original biomechanical behavior, and the mechanical axis should be taken into account if partial meniscectomy is necessary.
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http://dx.doi.org/10.1177/2325967118824611DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6378645PMC
February 2019

Optimising the tip-apex-distance in trochanteric femoral fracture fixation using the ADAPT-navigated technique, a longitudinal matched cohort study.

Injury 2019 Mar 13;50(3):744-751. Epub 2019 Feb 13.

Dept. for Trauma, Orthopaedics and Sportsmedicine, BG Clinic Hamburg and Dept. for Trauma and Orthopaedics, University Medical Centre Lübeck, Germany.

Introduction: The annual incidence of proximal femoral fractures is 100-150/100,000 and continues to increase with an aging population. Cut-out of hip screws after fracture fixation has been quoted as 8% in the literature. The tip-apex distance (TAD) is the strongest predictor for cut-out after operative fracture stabilisation. The aim of this study was to evaluate the novel ADAPT system (Adaptive Positioning Technology, Stryker, USA), a navigation device for intramedullary nailing of trochanteric fractures and its effect on optimising the TAD. This is the first clinical study to evaluate this new technology.

Methods: The study group of 36 consecutive patients with a pertrochanteric fracture underwent intramedullary nailing for fracture fixation using ADAPT technology, while the matched control group underwent conventional Gamma-3-nailing. Matching criteria included fracture classification, gender and age. We measured the operative time and the postoperative TAD in anteroposterior (AP) and lateral radiographs of the 72 patients.

Results: The mean TAD using ADAPT was 16.9 mm (range 8.4-33.7 mm) compared with 24.9 mm (range 14.6-40.2 mm) in the reference group treated without ADAPT. Using the ADAPT system significantly improved (p < 0.0005) the accuracy of lag screw placement but had no effect on operating time in fixation of femoral pertrochanteric fractures.

Conclusion: Working with the novel ADAPT system for positioning the lag screw using the Gamma-3-nail led to a statistically highly significant reduction of the TAD compared to the reference group (p < 0.001). The ADAPT system proved to be a very useful device in achieving higher surgical standards for the treatment of trochanteric fractures with intramedullary nailing. It enables higher accuracy in screw positioning and therefore better placement of the implant.
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http://dx.doi.org/10.1016/j.injury.2019.02.010DOI Listing
March 2019

3D grating-based X-ray phase-contrast computed tomography for high-resolution quantitative assessment of cartilage: An experimental feasibility study with 3T MRI, 7T MRI and biomechanical correlation.

PLoS One 2019 14;14(2):e0212106. Epub 2019 Feb 14.

Department of Radiology, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany.

Objective: Aim of this study was, to demonstrate the feasibility of high-resolution grating-based X-ray phase-contrast computed tomography (PCCT) for quantitative assessment of cartilage.

Materials And Methods: In an experimental setup, 12 osteochondral samples were harvested from n = 6 bovine knees (n = 2 each). From each knee, one cartilage sample was degraded using 2.5% Trypsin. In addition to PCCT and biomechanical cartilage stiffness measurements, 3T and 7T MRI was performed including MSME SE T2 and ME GE T2* mapping sequences for relaxationtime measurements. Paired t-tests and receiver operating characteristics (ROC) curves were used for statistical analyses.

Results: PCCT provided high-resolution images for improved morphological cartilage evaluation as compared to 3T and 7T MRI. Quantitative analyses revealed significant differences between the superficial and the deep cartilage layer for T2 mapping as well as for PCCT (P<0.05). No significant difference was detected for PCCT between healthy and degraded samples (P>0.05). MRI and stiffness measurements showed significant differences between healthy and degraded osteochondral samples. Accuracy in the prediction of cartilage degradation was excellent for MRI and biomechanical analyses.

Conclusion: In conclusion, high-resolution grating-based X-ray PCCT cartilage imaging is feasible. In addition to MRI and biomechanical analyses it provides complementary, water content independent, information for improved morphological and quantitative characterization of articular cartilage ultrastructure.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0212106PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6375589PMC
November 2019

Influence of Sutures on Cartilage Integrity: Do Meniscus Sutures Harm Cartilage? An Experimental Animal Study.

Arthroscopy 2019 05 8;35(5):1509-1516. Epub 2019 Feb 8.

Department of Sports Orthopaedics, Technical University of Munich, Klinikum rechts der Isar, Munich, Germany; Department of Sports Orthopaedics, Hessing Stiftung Augsburg, Augsburg, Germany. Electronic address:

Purpose: To evaluate whether different suture materials in meniscal repair may harm cartilage.

Methods: A preloaded linear friction testing setup including porcine knees with porcine cartilage, porcine meniscus, and different suture materials (braided nonabsorbable, absorbable monofilament) was used. Five groups with different tribological pairs were tested: cartilage on meniscus (control), cartilage on cartilage (control No. 2), and cartilage on different meniscus sutures (3 groups). Cartilage integrity was analyzed macroscopically by the India ink method and histologically using Giemsa-eosin-stained undecalcified methyl methacrylate sections. Cartilage lesions were classified by using a quantitative scoring system.

Results: The control groups did not show cartilage damage, either macroscopically or histologically. Loading cartilage with sutured menisci led to significant damage of the superficial radial and transitional zones with braided nonabsorbable (P = .03) and absorbable monofilament (P = .02) sutures at final examination. Menisci sutured with braided nonabsorbable material resulted in deeper damage to the cartilage. However, there were no significant differences between the suture materials. Sutures oriented perpendicular to surface motion led to a larger defect than parallel-oriented sutures.

Conclusions: Braided nonabsorbable and absorbable monofilament suture materials cause significant damage to cartilage during long-term cyclic loading in vitro. The extent of damage depends on suture orientation.

Clinical Relevance: This study provides data on the extent to which different suture materials in meniscus repair may harm cartilage.
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http://dx.doi.org/10.1016/j.arthro.2018.11.040DOI Listing
May 2019

Measuring large lipid droplet sizes by probing restricted lipid diffusion effects with diffusion-weighted MRS at 3T.

Magn Reson Med 2019 06 16;81(6):3427-3439. Epub 2019 Jan 16.

Department of Diagnostic and Interventional Radiology, Technical University of Munich, Munich, Germany.

Purpose: The in vivo probing of restricted diffusion effects in large lipid droplets on a clinical MR scanner remains a major challenge due to the need for high b-values and long diffusion times. This work proposes a methodology to probe mean lipid droplet sizes using diffusion-weighted MRS (DW-MRS) at 3T.

Methods: An analytical expression for restricted diffusion was used. Simulations were performed to evaluate the noise performance and the influence of particle size distribution. To validate the method, oil-in-water emulsions were prepared and examined using DW-MRS, laser deflection and light microscopy. The tibia bone marrow was scanned in volunteers to test the method repeatability and characterize microstructural differences at different locations.

Results: The simulations showed accurate and precise droplet size estimation when a sufficient SNR is reached with minor dependence on the size distribution. In phantoms, a good correlation between the measured droplet sizes by DW-MRS and by laser deflection (R = 0.98; P = 0.01) and microscopy (R = 0.99; P < 0.01) measurements was obtained. A mean coefficient of variation of 11.5 % was found for the lipid droplet diameter in vivo. The average diameter was smaller at a proximal (50.1 ± 7.3 µm) compared with a distal tibia location (61.1 ± 6.8 µm) (P < 0.01).

Conclusion: The presented methods were able to probe restricted diffusion effects in lipid droplets using DW-MRS and to estimate lipid droplet size. The methodology was validated using phantoms and the in vivo feasibility in bone marrow was shown based on a good repeatability and findings in agreement with literature.
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http://dx.doi.org/10.1002/mrm.27651DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6519235PMC
June 2019

Recommendations for iliosacral screw placement in dysmorphic sacrum based on modified in-out-in corridors.

J Orthop Res 2019 03 5;37(3):689-696. Epub 2019 Jan 5.

Department of Trauma-, Hand- and Reconstructive Surgery, University Hospital Jena, Germany.

(1) Can iliosacral osseous corridor diameters in sacral dysmorphism be enlarged by in-out-in screw placement at the posterior iliosacral recessus? (2) Are lumbosacral transitional vertebra (LSTV) the anatomical cause for sacral dysmorphism? (3) Are there sex-specific differences in sacral dysmorphism? 594 multislice CT scans were screened for sacral dysmorphism and 55 data-sets selected. Each pelvis was segmented manually and cylindrical iliosacral corridors (on the level of S1 and S2 vertebra) were semi-automatically determined. Corridor trajectories, -diameters and -lengths were measured. LSTV (Castellvi-type IIIb and IV) were found in 3 of 55 pelves and these lumbosacral variations are therefore not the anatomical basis for sacral dysmorphism. The prevalence of transsacral osseous corridors with diameters of <7.5 mm in axial CT images correlates with qualitative and quantitative criteria of sacral dysmorphism. Enlarging the osseous corridor diameters by penetration of the posterior iliosacral recessus increase the safe corridor diameters (females versus males) by 26% versus 15% at the level of S1- and 50% versus 48% at the level of S2-vertebra. Sex-specific differences for both corridors (osseous and in-out-in) were only found for the osseous corridor diameters at the level of S1 vertebra, being smaller in females (females versus males: 13.3 ± 3.6 mm versus 15.5 ± 3.8 mm, p = 0.04). Dysmorphic sacra can be reliably detected on standard axial CT slice images. Modified in-out-in corridors on the level of S1-vertebra allow screw placement in all patients, but is still demanding compared to non-dysmorphic sacra, due to the oblique corridor axis. Recommendations for intraoperative orientation for oblique screw placement are defined. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.
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http://dx.doi.org/10.1002/jor.24199DOI Listing
March 2019

Distal femoral torsional osteotomy increases the contact pressure of the medial patellofemoral joint in biomechanical analysis.

Knee Surg Sports Traumatol Arthrosc 2019 Jul 29;27(7):2328-2333. Epub 2018 Sep 29.

Department of Orthopaedic Sports Medicine, Hospital Rechts der Isar, Technical University Munich, Ismaningerstr. 22, 81675, Munich, Germany.

Purpose: Torsional osteotomy of the distal femur allows anatomic treatment of patellofemoral instability and patellofemoral pain syndrome in cases of increased femoral antetorsion. The purpose of this study was to investigate the effects of distal femoral torsional osteotomy on pressure distribution of the medial and lateral patellar facet.

Methods: Nine fresh frozen human knee specimens were embedded in custom-made 3D-printed casts and tested with a robotic arm. Torsional osteotomy could be simulated ranging from increased femoral antetorsion of 25° with a corresponding lateralization of the patella to an overcorrected value of 5° of femoral antetorsion. The peak and mean lateral and medial compartment pressure was measured in 0°, 15°, 30°, 45°, 60° and 90° flexion beginning with neutral anatomic muscle rotation.

Results: The medial aspect of the patella showed a significant influence of femoral torsion with an increase of mean and peak pressure in all flexion angles with progressive derotation from 15° external rotation to 5° internal rotation (p = 0.004). The overall pressure difference was highest in near extension and stayed on a constant level with further flexion. On the lateral facet, the derotation resulted in decrease of pressure in near extension; however, it had no significant influence on the mean and peak pressure through the different torsion angles (n.s.). Unlike on the medial facet, a significant consistent increase of peak pressure from 0° to 90° flexion could be shown (p = 0.022) on the lateral patella aspect.

Conclusion: Distal femoral torsional osteotomy to correct pathological femoral antetorsion leads to a redistribution of retropatellar pressure. External derotation leads to an increased peak pressure on the medial patellar facet and can impair simultaneous cartilage repair. However, as the lateral patellofemoral load decreases, it has a potential in preventing patellofemoral osteoarthritis.
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http://dx.doi.org/10.1007/s00167-018-5165-2DOI Listing
July 2019