On the suitability of additively manufactured gyroid structures and their potential use as intervertebral disk replacement - a feasibility study.

Introduction: Intervertebral disk degeneration is a growing problem in our society. The degeneration of the intervertebral disk leads to back pain and in some cases to a herniated disk. Advanced disk degeneration can be treated surgically with either a vertebral body fusion or a disk prosthesis. Vertebral body fusion is currently considered the gold standard of surgical therapy and is clearly superior to disk prosthesis based on the number of cases. The aim of this work was the 3D printing of Gyroid structures and the determination of their mechanical properties in a biomechanical feasibility study for possible use as an intervertebral disc prosthesis. Material and methods: Creo Parametric 6.0.6.0 was used to create models with various Gyroid properties. These were printed with the Original Prusa i3 MK3s+. Different flexible filaments (TPU FlexHard and TPU FlexMed, extrudr, Lauterach, Austria) were used to investigate the effects of the filament on the printing results and mechanical properties of the models. Characterization was carried out by means of microscopy and tension/compression testing on the universal testing machine. Results: The 3D prints with the FlexHard and FlexMid filament went without any problems. No printing errors were detected in the microscopy. The mechanical confined compression test resulted in force-deformation curves of the individual printed models. This showed that changing the Gyroid properties (increasing the wall thickness or density of the Gyroid) leads to changes in the force-deformation curves and thus to the mechanical properties. Conlcusion: The flexible filaments used in this work showed good print quality after the printing parameters were adjusted. The mechanical properties of the discs were also promising. The parameters Gyroid volume, wall thickness of the Gyroid and the outer wall played a decisive role for both FlexMed and FlexHard. All in all, the Gyroid structured discs (Ø 50 mm) made of TPU represent a promising approach with regard to intervertebral disc replacement. We would like to continue to pursue this approach in the future.

T1ρ relaxation mapping in osteochondral lesions of the talus: a non-invasive biomarker for altered biomechanical properties of hyaline cartilage?

BACKGROUND: To evaluate T1ρ relaxation mapping in patients with symptomatic talar osteochondral lesions (OLT) and healthy controls (HC) at rest, with axial loading and traction. METHODS: Participants underwent 3-T ankle magnetic resonance imaging at rest and with 500 N loading and 120 N traction, without axial traction for a subcohort of 17/29 HC. We used a fast low-angle shot sequence with variable spin-lock intervals for monoexponential T1ρ fitting. Cartilage was manually segmented to extract T1ρ values. RESULTS: We studied 29 OLT patients (age 31.7 ± 7.5 years, 15 females, body mass index [BMI] 25.0 ± 3.4 kg/m2) and 29 HC (age 25.2 ± 4.3 years, 17 females, BMI 22.5 ± 2.3 kg/m2. T1ρ values of OLT (50.4 ± 3.4 ms) were higher than those of intact cartilage regions of OLT patients (47.2 ± 3.4 ms; p = 0.003) and matched HC cartilage (48.1 ± 3.3 ms; p = 0.030). Axial loading and traction induced significant T1ρ changes in the intact cartilage regions of patients (loading, mean difference -1.1 ms; traction, mean difference 1.4 ms; p = 0.030 for both) and matched HC cartilage (-2.2 ms, p = 0.003; 2.3 ms, p = 0.030; respectively), but not in the OLT itself (-1.3 ms; p = 0.150; +1.9 ms; p = 0.150; respectively). CONCLUSION: Increased T1ρ values may serve as a biomarker of cartilage degeneration in OLT. The absence of load- and traction-induced T1ρ changes in OLT compared to intact cartilage suggests that T1ρ may reflect altered biomechanical properties of hyaline cartilage. TRIAL REGISTRATION: DRKS, DRKS00024010. Registered 11 January 2021, https://drks.de/search/de/trial/DRKS00024010 . RELEVANCE STATEMENT: T1ρ mapping has the potential to evaluate compositional and biomechanical properties of the talar cartilage and may improve therapeutic decision-making in patients with osteochondral lesions. KEY POINTS: T1ρ values in osteochondral lesions increased compared to intact cartilage. Significant load- and traction-induced T1ρ changes were observed in visually intact regions and in healthy controls but not in osteochondral lesions. T1ρ may serve as an imaging biomarker for biomechanical properties of cartilage.

Biodegradable composites with antibiotics and growth factors for dual release kinetics.

Bone infections are still a major problem in surgery. To avoid severe side effects of systemically administered antibiotics, local antibiotic therapy is increasingly being considered. Using a pressure-based method developed in our group, microporous ß-TCP ceramics, which had previously been characterized, were loaded with 2% w/v alginate containing 50 mg/mL clindamycin and 10 µg/mL rhBMP-2. Release experiments were then carried out over 28 days with changes of liquid at defined times (1, 2, 3, 6, 9, 14, 21 and 28d). The released concentrations of clindamycin were determined by HPLC and those of rhBMP-2 by ELISA. Continuous release (anomalous transport) of clindamycin and uniform release (Fick's diffusion) of BMP-2 were determined. The composites were biocompatible (live/dead, WST-I and LDH) and the released concentrations were all antimicrobially active against Staph. aureus. The results were very promising and clindamycin was detected in concentrations above the MIC as well as a constant rhBMP-2 release over the entire study period. Biocompatibility was also not impaired by either the antibiotic or the BMP-2. This promising approach can therefore be seen as an alternative to the common treatment with PMMA chains containing gentamycin, as the new composite is completely biodegradable and no second operation is necessary for removal or replacement.

Prediction of the Hamstring Graft Size for ACL Reconstruction Using Different Axial Layers in Preoperative MRI.

BACKGROUND: In ACL reconstruction, it is desirable to assess preoperatively whether a sufficient graft diameter can be achieved with the planned tendon graft. The present study investigated the effect of the location of the cross-sectional area (CSA) measurement of the hamstring tendons in preoperative MRI on the correlation of the CSA with the intraoperative graft diameter. In addition, we analyzed whether the measurement results of examiners with different skill levels were comparable. METHODS: A total of 32 subjects undergoing a single bundle ACL reconstruction using an autologous ipsilateral quadrupled hamstring graft (STGT) were included. The CSA of the semitendinosus and gracilis tendon was determined in preoperative MRI on six defined levels by three examiners. The intraclass correlation coefficient between the measurements of these observers was determined. The correlation between the sum of the CSA of both tendons (CSA STGT) and the graft diameter was investigated. RESULTS: The interrater reliability was excellent on most of the investigated levels. A significant correlation between CSA STGT and the graft diameter was seen on all levels. The strongest correlation was found on the level 10 mm above the joint line. CONCLUSIONS: The measurement of the CSA STGT in the preoperative MRI 10 mm above the joint line enabled a good assessment of the achievable graft diameter in ACL reconstruction, independent of the examiners' training level.

Medial malleolar osteotomy in the treatment of osteochondral lesions of the Talus - incidence and impact on functional outcome: a retrospective analysis based on data from the German Cartilage Register (KnorpelRegister DGOU).

BACKGROUND: There has long been discussion regarding the impact of medial malleolar osteotomies (MMO) as an adjunctive treatment for osteochondral lesions of the talus (OCLT). MMO may improve the visibility and accessibility of the talus, but they also pose a risk of periprocedural morbidity. There is a lack of research about the prevalence and consequences of MMO in the surgical treatment of OCLT. METHODS: This study retrospectively evaluated data from the German Cartilage Register (KnorpelRegister DGOU) from its implementation in 2015 to December 2020. The impact of MMO on patient-reported outcome measures (PROMs) was investigated. Wherever possible, subgroups were built and matched using a propensity score which matched a group undergoing OCLT without MMO. Matching included age, sex, weight, localization of the OCLT, the international cartilage repair society (ICRS) grading, surgical procedure and preoperative symptoms using the Foot and Ankle Ability Measure (FAAM) and the Activities of Daily Living Subscale (ADL). RESULTS: The prevalence of MMO in the operative treatment of OCLT was 15.9%. Most of the osteotomies were performed in OCL of the medial talar dome (76.8%) and in more serious lesions with an ICRS grade of III (29.1%) and IV (61.4%). More than half of the osteotomies (55.6%) were performed during revision surgery. A matched pair analysis of n = 44 patients who underwent AMIC® via arthrotomy and MMO vs. arthrotomy alone showed no significant differences in patient-reported outcome measures (PROMs, i.e. FAAM-ADL, and FAOS) at 6,12 and 24 months. CONCLUSIONS: MMO are mostly used in the treatment of severe (≥ ICRS grade 3) OCL of the medial talar dome and in revision surgery. Functional and patient-reported outcome measures are not significantly affected by MMO compared to arthrotomy alone. TRIAL REGISTRATION: The German Cartilage Register (KnorpelRegister DGOU) was initially registered at the German Clinical Trials Register ( https://www.drks.de , register number DRKS00005617, Date of registration 03.01.2014) and was later expanded by the ankle module.

Dual release of daptomycin and BMP-2 from a composite of ß-TCP ceramic and ADA gelatin.

BACKGROUND: Antibiotic-containing carrier systems are one option that offers the advantage of releasing active ingredients over a longer period of time. In vitro sustained drug release from a carrier system consisting of microporous ß-TCP ceramic and alginate has been reported in previous works. Alginate dialdehyde (ADA) gelatin gel showed both better mechanical properties when loaded into a ß-TCP ceramic and higher biodegradability than pure alginate. METHODS: Dual release of daptomycin and BMP-2 was measured on days 1, 2, 3, 6, 9, 14, 21, and 28 by HPLC and ELISA. After release, the microbial efficacy of the daptomycin was verified and the biocompatibility of the composite was tested in cell culture. RESULTS: Daptomycin and the model compound FITC protein A (n = 30) were released from the composite over 28 days. A Daptomycin release above the minimum inhibitory concentration (MIC) by day 9 and a burst release of 71.7 ± 5.9% were observed in the loaded ceramics. Low concentrations of BMP-2 were released from the loaded ceramics over 28 days.

Mortality after major lower extremity amputation and association with index level: a cohort study based on 11,205 first-time amputations from nationwide Danish databases.

BACKGROUND AND PURPOSE: Mortality after major lower extremity amputations is high and may depend on amputation level. We aimed to examine the mortality risk in the first year after major lower extremity amputation divided into transtibial and transfemoral amputations. METHODS: This observational cohort study used data from the Danish Nationwide Health registers. 11,205 first-time major lower extremity amputations were included from January 1, 2010, to December 31, 2021, comprising 3,921 transtibial amputations and 7,284 transfemoral amputations. RESULTS: The 30-day mortality after transtibial amputation was overall 11%, 95% confidence interval (CI) 10-12 (440/3,921) during the study period, but declined from 10%, CI 7-13 (37/381) in 2010 to 7%, CI 4-11 (15/220) in 2021. The 1-year mortality was 29% overall, CI 28-30 (1,140 /3,921), with a decline from 31%, CI 21-36 (117/381) to 20%, CI 15-26 (45/220) during the study period. For initial transfemoral amputation, the 30-day mortality was overall 23%, CI 22-23 (1,673/7,284) and declined from 27%, CI 23-31 (138/509) to 22%, CI 19-25 (148/683) during the study period. The 1-year mortality was 48% overall, CI 46-49 (3,466/7,284) and declined from 55%, CI 50-59 (279/509) to 46%, CI 42-50 (315/638). CONCLUSION: The mortality after major lower extremity amputation declined in the 12-year study period; however, the 1-year mortality remained high after both transtibial and transfemoral amputations (20% and 46% in 2021). Hence, major lower extremity amputation patients constitute one of the most fragile orthopedic patient groups, emphasizing an increased need for attention in the pre-, peri-, and postoperative setting.

Mechanical and histological properties of native medial menisci compared to allograph medial menisci in the osteoarthritic knee.

This study was designed to provide information on how the menisci change over the course of osteoarthritis, particularly with regard to their mechanical properties. The aim was to determine the difference between healthy menisci (fresh frozen meniscal transplants) and menisci harvested during total knee arthroplasty. The latter allows the grading of age-related and osteoarthritic changes in the menisci on macroscopic and microscopic levels. A total of 10 menisci from arthritic knee joints (medial) harvested during total knee arthroplasty were used and compared with 10 medial fresh frozen meniscal transplants. The mechanical measurements were carried out on a Mach-1 testing machine using indentation testing to determine the instantaneous modulus and the thickness of the menisci. The specimens were then embedded in paraffin, sectioned on a microtome, and stained with hematoxylin-eosin and safranin-O. All measurements were divided into the anterior horn, pars intermedia, and posterior horn. There was no significant difference in the instantaneous modulus for the posterior horn in the fresh frozen menisci with 0.27 ± 0.1 MPa compared to the arthritic menisci with 0.18 ± 0.03 MPa. No significant difference could be determined for the meniscus thicknesses. There was a significant difference in the safranin-O staining. There were also significant differences in the Pauli score: the arthrosis menisci showed a sum score that was, on average, four times higher than the sum score of the fresh frozen menisci. In the present study, it could be shown very well that there are significant differences in the mechanical properties as well as in the macroscopic and histopathological scores, such as the Pauli score, between the fresh frozen meniscus allografts considered healthy and osteoarthritic menisci resulting from total knee arthroplasty. With a degradation score of 3 (Pauli), the instantaneous modulus was reduced by more than 50% compared to healthy controls. More importantly, however, the fresh frozen menisci only show a grade 2 when converting the sum values into grades, where a grade 2 indicates slight degeneration. This is interesting because fresh frozen meniscus transplants were always considered healthy in previous publications and should, therefore, actually have a grade 1.

Response of Articular Cartilage to Hyperosmolar Stress: Report of an Ex Vivo Injury Model.

BACKGROUND: Physiological 0.9% saline is commonly used as an irrigation fluid in modern arthroscopy. There is a growing body of evidence that a hyperosmolar saline solution has chondroprotective effects, especially if iatrogenic injury occurs. PURPOSE: To (1) corroborate the superiority of a hyperosmolar saline solution regarding chondrocyte survival after mechanical injury and (2) observe the modulatory response of articular cartilage to osmotic stress and injury. STUDY DESIGN: Controlled laboratory study. METHODS: Osteochondral explants were isolated from bovine stifle joints and exposed to either 0.9% saline (308 mOsm) or hyperosmolar saline (600 mOsm) and then damaged with a sharp dermatome blade to attain a confined full-thickness cartilage injury site, incubated in the same fluids for another 3 hours, and transferred to chondropermissive medium for further culture for 1 week. Chondrocyte survival was assessed by confocal imaging, while the cellular response was evaluated over 1 week by relative gene expression for apoptotic and inflammatory markers and mediator release into the medium. RESULTS: The full-thickness cartilage cut resulted in a confined zone of cell death that mainly affected superficial zone chondrocytes. Injured samples that were exposed to hyperosmolar saline showed less expansion of cell death in both the axial (P < .007) and the coronal (P < .004) plane. There was no progression of cell death during the following week of culture. Histological assessment revealed an intact cartilage matrix and normal chondrocyte morphology. Inflammatory and proapoptotic genes were upregulated on the first days postexposure with a notable downregulation toward day 7. Mediator release into the medium was concentrated on day 3. CONCLUSION: This in vitro cartilage injury model provides further evidence for the chondroprotective effect of a hyperosmolar saline irrigation fluid, as well as novel data on the capability of articular cartilage to quickly regain joint homeostasis after osmotic stress and injury. CLINICAL RELEVANCE: Raising the osmolarity of an irrigating solution may be a simple and safe strategy to protect articular cartilage during arthroscopic surgery.

Validation of a Finite Element Simulation for Predicting Individual Knee Joint Kinematics.

Goal: We introduce an in-vivo validated finite element (FE) simulation approach for predicting individual knee joint kinematics. Our vision is to improve clinicians' understanding of the complex individual anatomy and potential pathologies to improve treatment and restore physiological joint kinematics. Methods: Our 3D FE modeling approach for individual human knee joints is based on segmentation of anatomical structures extracted from routine static magnetic resonance (MR) images. We validate the predictive abilities of our model using static MR images of the knees of eleven healthy volunteers in dedicated knee poses, which are achieved using a customized MR-compatible pneumatic loading device. Results: Our FE simulations reach an average translational accuracy of 2 mm and an average angular accuracy of 1[Formula: see text] compared to the reference knee pose. Conclusions: Reaching high accuracy, our individual FE model can be used in the decision-making process to restore knee joint stability and functionality after various knee injuries.

Non-unions and wound infections do not differ following intramedullary nailing and plate osteosynthesis for distal third femur fractures: a meta-analysis.

Purpose: The fixation method of distal, extra-articular femur fractures is a controversially discussed. To ensure better stability itself, earlier mobilization and to prevent blood loss - all these are justifications for addressing the femur via reamed intramedullary nailing (RIMN). Anatomical reposition of multifragmentary fractures followed by increased risks of non-union are compelling reasons against it. The purpose of this study was to systematically review the literature for rates of non-union and wound infection, as well as blood loss and time of surgery. Methods: According to the PRISMA guidelines we conducted this systematic review by searching the Cochrane, PubMed, Ovid, MedLine, and Embase databases. Inclusion criteria were the modified Coleman methodology score (mCMS) >60, age >18 years, and extra-articular fractures of the distal femur. Biomechanical and animal studies were excluded. By referring to title and abstract relevant articles were reviewed independently. In the consecutive meta-analysis, we compared 9 studies and 639 patients. Results: There is no statistically significant difference comparing superficial wound infections when RIMN was performed (OR = 0.50; 95% CI: 0.18 - 1.42; P = 0.19) as well as in deep wound infections (OR = 0.74; 95% CI: 0.19-2.81; P = 0.62). However, these results were not significant. We also calculated for potential differences in the rate of non-unions depending on the surgical treatment applied. Data of 556 patients revealed an overall number of 43 non-unions. There was no significant difference in rate of non-unions between both groups (OR = 0.97; 95% CI: 0.51-1.85; P = 0.92). Conclusion: No statistical difference was found in our study among RIMN and plate fixation in the treatment of distal femoral fractures with regard to the incidence of non-union and wound infections. Therefore, the indication for RIMN or plating should be made individually and based on the surgeon's experience.

Major lower extremity amputations - risk of re-amputation, time to re-amputation, and risk factors: a nationwide cohort study from Denmark.

BACKGROUND AND PURPOSE: Re-amputation after lower extremity amputation is frequent. The primary aim of our study was to investigate cumulative re-amputation risk after transtibial amputation (TTA), knee disarticulation (KD), and transfemoral amputation (TFA) and secondarily to investigate time to re-amputation, and risk factors. METHODS: This observational cohort study was based on data from the Danish Nationwide Health registers. The population included first-time major lower extremity amputations (MLEA) performed in patients ≥ 50 years between 2010 and 2021. Both left and right sided MLEA from the same patient were included as index procedures. RESULTS: 11,743 index MLEAs on 10,052 patients were included. The overall cumulative risks for re-amputation were 29% (95% confidence interval [CI] 27-30), 30% (CI 26-35), and 11% (CI 10-12) for TTA, KD, and TFA, respectively. 58% of re-amputations were performed within 30 days after index MLEA. Risk factors for re-amputation within 30 days were dyslipidemia (hazard ratio [HR] 1.2, CI 1.0-1.3), renal insufficiency (HR 1.2, CI 1.1-1.4), and prior vascular surgery (HR 1.3, CI 1.2-1.5). CONCLUSION: The risk of re-amputation was more than twice as high after TTA (29%) and KD (30%) compared with TFA (11%). Most re-amputations were conducted within 30 days of the index MLEA. Dyslipidemia, renal insufficiency, and prior vascular surgery were associated with higher risk of re-amputation.

Internal Rotation Measurement of the Knee with Polymer-Based Capacitive Strain Gauges versus Mechanical Rotation Measurement Taking Gender Differences into Account: A Comparative Analysis.

With the conventional mechanical rotation measurement of joints, only static measurements are possible with the patient at rest. In the future, it would be interesting to carry out dynamic rotation measurements, for example, when walking or participating in sports. Therefore, a measurement method with an elastic polymer-based capacitive measuring system was developed and validated. In our system, the measurement setup was comprised of a capacitive strain gauge made from a polymer, which was connected to a flexible printed circuit board. The electronics integrated into the printed circuit board allowed data acquisition and transmission. As the sensor strip was elongated, it caused a change in the spacing between the strain gauge's electrodes, leading to a modification in capacitance. Consequently, this alteration in capacitance enabled the measurement of strain. The measurement system was affixed to the knee by adhering the sensor to the skin in alignment with the anterolateral ligament (ALL), allowing the lower part of the sensor (made of silicone) and the circuit board to be in direct contact with the knee's surface. It is important to note that the sensor should be attached without any prior stretching. To validate the system, an in vivo test was conducted on 10 healthy volunteers. The dorsiflexion of the ankle was set at 2 Nm using a torque meter to eliminate any rotational laxity in the ankle. A strain gauge sensor was affixed to the Gerdii's tubercle along the course of the anterolateral ligament, just beneath the lateral epicondyle of the thigh. In three successive measurements, the internal rotation of the foot and, consequently, the lower leg was quantified with a 2 Nm torque. The alteration in the stretch mark's length was then compared to the measured internal rotation angle using the static measuring device. A statistically significant difference between genders emerged in the internal rotation range of the knee (p = 0.003), with female participants displaying a greater range of rotation compared to their male counterparts. The polymer-based capacitive strain gauge exhibited consistent linearity across all measurements, remaining within the sensor's initial 20% strain range. The comparison between length change and the knee's internal rotation angle revealed a positive correlation (r = 1, p < 0.01). The current study shows that elastic polymer-based capacitive strain gauges are a reliable instrument for the internal rotation measurement of the knee. This will allow dynamic measurements in the future under many different settings. In addition, significant gender differences in the internal rotation angle were seen.

Effect of Vancomycin, Gentamicin and Clindamycin on Cartilage Cells In Vitro.

BACKGROUND: The treatment of grafts with vancomycin for ligament reconstruction in knee surgery is the current standard. However, high antibiotic concentrations have chondrotoxic effects. PURPOSE: To test the chondrotoxicity of clindamycin, gentamicin and vancomycin in comparable concentrations. In vitro and in vivo effective concentrations hugely vary from drug to drug. To allow for comparisons between these three commonly used antibiotics, the concentration ranges frequently used in orthopedic surgical settings were tested. STUDY DESIGN: Controlled laboratory study. METHODS: Human cartilage from 10 specimens was used to isolate chondrocytes. The chondrocytes were treated with clindamycin (1 mg/mL and 0.5 mg/mL), gentamicin (10 mg/mL and 5 mg/mL) or vancomycin (10 mg/mL and 5 mg/mL), at concentrations used for preoperative infection prophylaxis in ligament surgery. Observations were taken over a period of 7 days. A control of untreated chondrocytes was included. To test the chondrotoxicity, a lactate dehydrogenase (LDH) test and a water-soluble tetrazolium salt (WST-1) assay were performed on days 1, 3 and 7. In addition, microscopic examinations were performed after fluorescence staining of the cells at the same time intervals. RESULTS: All samples showed a reasonable vitality of the cartilage cells after 72 h. However, clindamycin and gentamicin both showed higher chondrotoxicity in all investigations compared to vancomycin. After a period of 7 days, only chondrocytes treated with vancomycin showed reasonable vitality. CONCLUSIONS: The preoperative treatment of ligament grafts with vancomycin is the most reasonable method for infection prophylaxis, in accordance with the current study results regarding chondrotoxicity; however, clindamycin and gentamicin cover a wider anti-bacterial spectrum. CLINICAL RELEVANCE: The prophylactic antibiotic treatment of ligament grafts at concentrations of 5 mg/mL or 10 mg/mL vancomycin is justifiable and reasonable. In specific cases, even the use of gentamicin and clindamycin is appropriate.

Influence of the COVID-19 Pandemic on Musculoskeletal Complaints and Psychological Well-Being of Employees in Public Services-A Cohort Study.

BACKGROUND: The COVID-19 pandemic resulted in unprecedented restrictions on public and private life. The aim of the study was to investigate the impact of the COVID-19 pandemic on the physical and mental health of employees in the public sector, especially patient-related professions. METHODS: For the data collection in summer 2021, an online questionnaire was used. Compared to a pre-pandemic point of time, the prevalence, frequency, and intensity of musculoskeletal pain, mental well-being, health status, and quality of life were recorded. RESULTS: The questionnaire was completed by 1678 employees (f: 1045, m: 617). A total of 1504 employees (89.6%) were affected by complaints. Compared to before the pandemic, the prevalence and intensity of musculoskeletal complaints and psychological distress increased significantly. Patient-related professions (n = 204) showed significantly higher levels of stress and discomfort in several aspects (p < 0.05). CONCLUSIONS: Due to the COVID-19 pandemic, there was an increase in musculoskeletal complaints and a decrease in psychological well-being. Preventive factors related to mental health were identified as male gender, a middle- to older-age group, employees with children, and working from home. Attention should be drawn to these findings and prevention strategies should be brought into focus to strengthen the employees' health. Special focus should be drawn to patient-related professions who are particularly confronted with pandemic-associated challenges.

Digital measurement of anterolateral knee laxity using strain sensors.

PURPOSE: The ambition of the research group was to develop a sensor-based system that allowed the transfer of results with strain sensors applied to the knee joint. This system was to be validated in comparison to the current static mechanical measurement system. For this purpose, the internal rotation laxity of the knee joint was measured, as it is relevant for anterolateral knee laxity and anterior cruciate ligament (ACL) injury. METHODS: This is a noninvasive measurement method using strain sensors which are applied to the skin in the course of the anterolateral ligament. The subjects were placed in supine position. First the left and then the right leg were clinically examined sequentially and documented by means of an examination form. 11 subjects aged 21 to 45 years, 5 women and 6 men were examined. Internal rotation of the lower leg was performed with a torque of 2 Nm at a knee flexion angle of 30°. RESULTS: Comparison of correlation between length change and internal knee rotation angle showed a strong positive correlation (r = 1, p < 0.01). Whereas females showed a significant higher laxity vs. males (p = 0.003). CONCLUSIONS: The present study showed that the capacitive strain sensors can be used for reproducible measurement of anterolateral knee laxity. In contrast to the previous static systems, a dynamic measurement will be possible by this method in the future.

[Influence of the quadriceps muscles on the patellofemoral contact in patients with low flexion patellofemoral instability after MPFL reconstruction]. / Einfluss der Quadrizepsmuskulatur auf den patellofemoralen Kontaktmechanismus bei Patienten mit strecknaher patellofemoraler Instabilität nach MPFL-Rekonstruktion.

INTRODUCTION: MPFL reconstruction represents one of the most important surgical treatment options for recurrent patellar dislocations at low flexion angles associated with low flexion patellofemoral instability. Nevertheless, the role of quadriceps muscles in patients with patellofemoral instability before and after patellofemoral stabilization using MPFL reconstruction has not been fully elucidated. The present study investigates the influence of quadriceps muscles on the patellofemoral contact in patients with low flexion patellofemoral instability (PFI) before and after surgical patellofemoral stabilization using MPFL reconstruction using 3 T MRI datasets in early degrees of flexion (0-30°). METHODS: In this prospective cohort study, 15 patients with low flexion PFI before and after MPFL reconstruction and 15 subjects with healthy knee joints were studied using dynamic MRI scans. MRI scans were performed in a custom-made pneumatic knee loading device to determine the patellofemoral cartilage contact area (CCA) with and without quadriceps activation (50 N). Comparative measurements were performed using 3D cartilage and bone meshes in 0-30° knee flexion in the patients with patellofemoral instability preoperatively and postoperatively. RESULTS: The preoperative patellofemoral CCA of patients with low flexion PFI was 67.3 ± 47.3 mm2 in 0° flexion, 118.9 ± 56.6 mm2 in 15° flexion, and 267.6 ± 96.1 mm2 in 30° flexion. With activated quadriceps muscles (50 N), the contact area was 72.4 ± 45.9 mm2 in extension, 112.5 ± 54.9 mm2 in 15° flexion, and 286.1 ± 92.7 mm2 in 30° flexion without statistical significance. Postoperatively determined CCA revealed 159.3 ± 51.4 mm2 , 189.6 ± 62.2 mm2 and 347.3 ± 52.1 mm2 in 0°, 15° and 30° flexion. Quadriceps activation with 50 N showed a contact area in extension of 141.0 ± 63.8 mm2, 206.6 ± 67.7 mm2 in 15° flexion, and 353.5 ± 64.6 mm2 in 30° flexion, also without statistical difference compared with unloaded CCAs. Subjects with healthy knee joints showed an increase of 10.3% in CCA at 30° of flexion (p = 0.003). CONCLUSION: Although patellofemoral CCA increases significantly after isolated MPFL reconstruction in patients with low flexion patellofemoral instability, there is no significant influence of quadriceps muscles either preoperatively or postoperatively.

Fractures in Childhood and Young Adulthood According to Maternal Smoking in Late Pregnancy. A Danish Cohort Study.

BACKGROUND: Fractures account for the most frequent cause of hospitalization during childhood and numbers have increased over time. Of all fractures in childhood and young adulthood, 66% are recurrent fractures, suggesting that some people are predestined for fractures. The aim of this study was to investigate the association between maternal smoking during late pregnancy and the risk of fractures in the children. METHODS: The study included 11,082 mothers and their children from the cohort "Healthy Habits for Two" born between 1984 and 1987. Information about maternal smoking during pregnancy came from questionnaires filled out in pregnancy, while information about fractures was derived from the Danish National Patient Registry. Over a follow-up of 24 years (1994-2018), Cox regression with multiple failures was used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) for fractures in childhood and young adulthood according to maternal smoking in late pregnancy. Information about body mass index (BMI) and smoking status in young adulthood was included as time variant covariates. RESULTS: During an age span of 8-32 years, 6,420 fractures were observed. Of the mothers, 39.1% smoked during late pregnancy. Compared to children of mothers who did not smoke, children of mothers who smoked 1-9 cigarettes per day and 10+ cigarettes per day had an increased risk of fractures (HR 1.14 [CI: 1.06; 1.21] and HR 1.14 [CI: 1.07; 1.22], respectively). After adjusting for BMI and smoking status in young adulthood, the findings were slightly strengthened, showing an increased risk of fractures of 23 and 25% in children of mothers smoking 1-9 cigarettes per day and 10+ cigarettes per day, respectively. CONCLUSION: Maternal smoking during late pregnancy was associated with a higher risk of fractures in the child. This result indicates that exposure to cigarette smoke in utero may play a role in lifelong bone health.

Composite material consisting of microporous beta-TCP ceramic and alginate-dialdehyde-gelatin for controlled dual release of clindamycin and bone morphogenetic protein 2.

The aim of this study was to produce a composite of microporous ß-TCP filled with alginate-gelatin crosslinked hydrogel, clindamycin and bone morphogenetic protein (BMP-2) to prolong the drug-release behaviour for up to 28 days. The most promising alginate-di-aldehyde(ADA)-gelatin gel for drug release from microcapsules was used to fill microporous ß-TCP ceramics under directional flow in a special loading chamber. Dual release of clindamycin and BMP-2 was measured on days 1, 2, 3, 6, 9, 14, 21 and 28 by high performance liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA). After release, the microbial efficacy of the clindamycin was checked and the biocompatibility of the composite was tested in cell culture. Clindamycin and the model substance FITC-protein A were released from microcapsules over 28 days. The clindamycin burst release was 43 ± 1%. For the loaded ceramics, a clindamycin release above the minimal inhibitory concentration (MIC) until day 9 and a burst release of 90.56 ± 2.96% were detected. BMP-2 was released from the loaded ceramics in low concentrations over 28 days. The release of active substances from ß-TCP and hydrogel have already been extensively studied. Directional flow loading is a special procedure in which the ceramic could act as a stabilizer in the bone and, as a biodegradable system, enables a single-stage surgical procedure. Whether ADA-gelatin gel is suitable for this procedure as a more biodegradable alternative to pure alginate or whether a dual release is possible in this composite has not yet been investigated.

Effect of 20 µm thin ceramic coatings of hydroxyapatite, bioglass, GB14 and Beta-Tricalciumphosphate with copper on the biomechanical stability of femoral implants.

In the present work, we test four thin coatings for titanium implants, namely, bioglass, GB14, Beta-Tricalciumphosphate (ß-TCP) and hydroxyapatite (HA) with and without incorporated copper ions for their osteointegrative capacity. A rabbit drill hole model for time intervals up to 24 weeks was used in this study. Implant fixation was evaluated by measuring shear strength of the implant/bone interface. Quantitative histological analysis was performed for the measurements of bone contact area. Implants with and without copper ions were compared after 24 weeks. Thin coatings of GB14, HA or TCP on titanium implants demonstrated high shear strength during the entire test period of up to 24 weeks. Results confirmed osteointegrative properties of the coatings and did not reveal any negative effect of copper ions on osteointegration. The integration of copper in degradable osteoconductive coatings with a thickness of approx. 20 µm represents a promising method of achieving antibacterial shielding during the entire period of bone healing while at the same time improving osteointegration of the implants.