Vitamin D Deficiency Is Frequent in Patients with Rapidly Destructive Osteoarthritis-Data from a Single-Center Analysis.

BACKGROUND: Rapidly destructive osteoarthritis (RDO) of the hip joint is characterised by the rapid destruction of the femoral head with or without acetabular involvement. There has been increasing interest in this disease over the past years; however, the entity is still poorly understood, and its pathophysiology remains unknown. Yet, there is ample evidence today that increased bone metabolism might play a role in the onset and progression of the disease. Vitamin D is of utmost importance to maintain a balanced bone metabolism. However, whether vitamin D deficiency is involved in disease development remains to be elucidated. Further, the vitamin D status of patients with RDO has not yet been analysed. For this reason, the objective of this study was to assess the vitamin D status of patients with RDO. Moreover, the aim was to clarify whether there is a difference in the vitamin D status of patients with RDO compared with patients with primary osteoarthritis (OA). METHODS: In this single-centre analysis, the 25(OH)D, PTH, and calcium levels of 29 patients who presented with RDO between 2020 and 2022 were assessed. RESULTS: Altogether, 97% of patients (28/29) were vitamin D deficient, a further 3% (1/29) were vitamin D insufficient, and not a single patient presented with a sufficient vitamin D status. Notably, the vitamin D levels of RDO patients (mean = 11.04 ng/mL) were significantly lower than the vitamin D levels of patients with OA (mean = 22.16 ng/mL, p = 0.001). CONCLUSION: In conclusion, we found a widespread and high rate of vitamin D deficiency in patients with RDO. Hence, we believe that 25(OH)D status should routinely be analysed in these patients.

Zirconium as a Promising Synovial Biomarker for Loose Cemented Knee Prosthesis.

BACKGROUND: Aseptic loosening is the most common mode of failure after total knee arthroplasty. Despite this, the diagnosis often remains challenging and mainly relies on imaging modalities. Until today, no biomarker exists to aid in diagnosing loosening of the implants. As zirconium (Zr) is often found in bone cement, where it serves as radiopacifier, this study aimed to establish Zr as a synovial biomarker for loosened cemented knee prostheses. METHODS: A total of 31 patients scheduled for revision of a cemented knee prostheses were included. In all patients, the initial used cement contained Zr. After arthrotomy, specimens of synovial fluid were taken and levels of Zr were measured by inductively coupled plasma mass spectrometry. Depending on the necessary amount of force for explantation, the implants were graded "loose" or "well-fixed". Preoperative radiographs were evaluated by 2 independent physicians. RESULTS: The concentration of Zr in the synovial fluid differed significantly (P < .001) between the "loose" (mean 170.9 µg/L, range 0 to 1941 µg/L) and the "well-fixed" (mean 0.6 µg/L, range 0 to 6 µg/L) implants. The receiver operating characteristic analysis revealed 0.25 µg/l as an optimal cutoff value leading to a sensitivity of 0.84, a specificity of 0.92, a positive predictive value of 0.94, and a negative predictive value of 0.79. There was no significant difference in the diagnostic performance compared to radiographs (P = .66). CONCLUSIONS: Zirconium proved to be a reliable novel synovial biomarker for diagnosing aseptic loosening of knee prothesis fixed with cement containing Zr. This biomarker should not be interpreted in isolation, but in combination with existing diagnostic tools.

Does Body Mass Index (BMI) Affect the Reconstruction of Biomechanical Parameters in Patients Undergoing Total Hip Replacement (THR) through the Direct Anterior Approach (DAA)?

OBJECTIVE: Direct anterior approach total hip replacement (DAA-THR) is gaining increased interest due to its tissue-sparing nature and rapid recovery. Obesity has been shown to be a significant parameter influencing cup positioning in DAA-THR. It was the intention of this retrospective study to examine how obesity would influence the restoration of native hip biomechanical parameters during DAA-THR. MATERIALS AND METHODS: A total of 74 patients from a high-volume university orthopedic center after unilateral DAA-THA were included. Patients were retrospectively allocated to a study group (BMI > 30 kg/m2) and a control group (BMI < 30 kg/m2). Furthermore, propensity-score matching for baseline parameters was performed, leaving 30 patients in each group. Biomechanical parameters of the hip (i.e., femoral offset (FO), abductor lever arm (ABL), acetabular offset (AO), center of rotation (COR), stem alignment (SA), body weight lever arm (BWL), cup inclination (CI), and leg length discrepancy (LLD) were evaluated on standardized plain radiographs, and parameters were compared to the native contralateral hip. RESULTS: Mean BMI in the study group was 35.07 ± 5.13 kg/m2 and 25.43 ± 2.64 kg/m2 in the control group. There was a significant decrease of the ABL only in the study cohort (p = 0.01). CI and SA did not differ between both cohorts. FO was slightly increased compared to the native hip in both groups. There was a marginally higher but non-significant proportion of improper FO restoration in the study group (19 vs. 16 patients, p = 0.60). CONCLUSIONS: Obesity, as quantified by BMI, only has a limited impact on the adequate reconstruction of native biomechanical parameters of the hip during DAA-THR. ABL was the only parameter to be significantly decreased in the overweight patients after DAA-THR. Therefore, special care should be taken on proper acetabular reaming and consequent seating of the cup in the obese patient to avoid excessive lateral positioning.

Accuracy of Positioning and Risk Factors for Malpositioning Custom-Made Femoral Stems in Total Hip Arthroplasty-A Retrospective Multicenter Analysis.

Total hip arthroplasty (THA) is commonly performed using off-the-shelf implants. In the case of a severe mismatch between the anatomy of the proximal femur and the geometry of the stem, the use of custom-made stems might become necessary. The goal of this study was to investigate the precision of the implantation of custom-made stems of one manufacturer (CTX stem, AQ Implants) and to determine risk factors for malpositioning. All patients receiving a custom-made CTX stem between 2014 and 2020 at six high-volume academic centers were retrospectively recruited. The achieved position of the stem, as determined by stem version, stem coronal angle, and implantation depth on radiographs, was compared to the plan. The influence of radiographic and demographic parameters on the position was investigated. The results revealed a high variability of the achieved implant position in relation to the preoperative plan. While the stem coronal angle only differed slightly from the intended position, the stem version and the implantation depth showed a high frequency and amount of deviation. Right stems showed significantly higher positions than planned. Surgeons must be aware of this potential problem when implanting custom-made stems.

Rotational alignment of the lower extremity in the presence of total knee endoprosthesis: Reproducibility of torsion analyses using ultra-low-dose photon-counting CT.

PURPOSE: Leg torsion analysis can provide valuable information in symptomatic patients after total knee arthroplasty. However, extensive beam-hardening and photon-starvation artifacts limit diagnostic assessability and dose reduction potential. For this study, we investigated the reproducibility of rotational measurements in ultra-low-dose photon-counting CT with spectral shaping via tin prefiltration. MATERIAL AND METHODS: Employing a first-generation photon-counting CT, eight cadaveric specimens were examined with an established three-level scan protocol (hip: Sn 140, knee: Sn 100, ankle: Sn 100 kVp). In three body donors with unilateral knee endoprostheses, additional modified settings were applied (Sn 140 kVp at knee level). Protocols were executed with three dose levels (hip-knee-ankle, high-quality: 5.0-3.0-2.0 mGy, low-dose: 0.80-0.30-0.26 mGy, ultra-low-dose: 0.25-0.06-0.06 mGy). Six radiologists performed torsion analyses, additionally reporting their diagnostic confidence. Intraclass correlation coefficients (ICC) were calculated to assess interrater reliability. RESULTS: No significant differences were ascertained for femoral (p = 0.330), tibial (p = 0.177), and overall leg rotation measurements (p = 0.358) among high-quality, low-dose, and ultra-low-dose protocols. Interrater reliability was excellent for torsion of the femur (ICC 0.915, 95% confidence interval 0.871-0.947), tibia (0.960, 0.938-0.976), and overall leg (0.967, 0.945-0.981). In specimens with total knee endoprostheses, absolute rotational measurements were unaffected by dose level and tube voltage despite superior diagnostic confidence on the ipsilateral and contralateral sides with modified settings (p < 0.001). CONCLUSIONS: Combining the advantages of photon-counting CT and spectral shaping, reliable leg torsion analyses are feasible with ultra-low radiation exposure even in the presence of total knee endoprostheses.

The Direct Anterior Approach (DAA) as a Standard Approach for Total Hip Arthroplasty (THA) in Coxa Profunda and Protrusio Acetabuli? A Radiographic Analysis of 188 Cases.

INTRODUCTION: The direct anterior approach (DAA) represents a well-recognized soft tissue sparing technique for primary total hip arthroplasty (THA). The feasibility and suitability of the DAA in cases of complex acetabular deformities, namely coxa profunda (CP) and protrusio acetabuli (PA), remain to be determined. METHODS: A total of 188 cases of CP (100 cases) and PA (88 cases) hips undergoing primary THA via the DAA were retrospectively analyzed. Surgical and radiographic parameters were evaluated and potential complications were assessed. Finally, successful implantation was defined if surgical and radiographic parameters were well within established values of non-complex primary THA. RESULTS: In 159 hips, the medial border of the acetabular component was transferred laterally to the ilioischial line, corresponding to a fully treated acetabular protrusion. In 23 (12.23%) cases, mild, and in 5 (2.66%) cases, moderate residual acetabular protrusion remained after THA. Postoperatively, 11.40% (PA group) and 9.00% (CP group) had a leg length discrepancy (LLD) greater than 10 mm. The mean operative time was significantly less than 60 min. A linear relationship between the BMI and operative time was observed, with an additional 0.9 min of operative time per BMI unit. Overall, complications were rare and did not differ between the two groups. CONCLUSION: The results of this study suggest that the DAA is a suitable approach for primary THA in patients with coxa profunda and acetabular protrusion if performed by experienced surgeons familiar with the DAA. Obese patients with acetabular protrusion may pose a significant limitation to the DAA and caution should be advised in cases of obesity.

Handmade spacers for two-stage exchange at the hip.

OBJECTIVE: Two-stage exchange with implantation of a temporary spacer is the gold standard treatment for chronic periprosthetic joint infection of the hip. This article describes a simple and safe technique for handmade spacers at the hip. INDICATION: Periprosthetic joint infection of the hip. Septic arthritis of the native joint. CONTRAINDICATIONS: Known allergy against components of polymethylmethacrylate bone cements. Inadequate compliance for two-stage exchange. Patient unfit to undergo two-stage exchange. Bony defect situation at the acetabulum impeding stable reduction of the spacer. Bone loss at the femur jeopardizing stable fixation of the stem. Soft tissue damage with need for plastic temporary vacuum-assisted wound closure (VAC) therapy. SURGICAL TECHNIQUE: Tailoring bone cement with antibiotics. Preparation of a metal endoskeleton. Molding of spacer stem and head by hand. Customizing spacer off-sets to bony anatomy and soft tissue tension. Implantation assuring rotational stability at the femur with a bone cement collar. Confirmation of correct position by intraoperative radiography. POSTOPERATIVE MANAGEMENT: Restricted weight-bearing. Range of motion as possible. Reimplantation after successful treatment of infection.

Demographics and Trends for Inbound Medical Tourism in Germany for Orthopedic Patients before and during the COVID-19 Pandemic.

Medical tourism is a rapidly growing sector of economic growth and diversification. However, data on the demographics and characteristics of the traveling patients are sparse. In this study, we analyzed the common demographic properties and characteristics of the inbound medical tourists seeking orthopedic medical care in Germany for the years 2010 to 2019 compared to a domestic group. At the same time, we examined how the COVID-19 pandemic outbreak of 2020 changed the field of medical tourism in Germany. Calculations were performed using administrative hospital data provided by the Federal Statistical Department of Germany. Data were analyzed from the years 2010 to 2020. A total of six elective orthopedic surgery codes (bone biopsy, knee arthroplasty, foot surgery, osteotomy, hardware removal, and arthrodesis) were identified as key service indicators for medical tourism and further analyzed. Factors including residence, sex, year, and type of elective surgery were modeled using linear regression analysis. Age and sex distributions were compared between patients living inside Germany (DE) or outside Germany (non-DE). Between 2010 and 2020, 6,261,801 orthopedic procedures were coded for the DE group and 27,420 key procedures were identified for the non-DE group. Medical tourists were predominantly male and significantly younger than the domestic population. The linear regression analysis of the OPS codes over the past years showed a significantly different slope between the DE and non-DE groups only for the OPS code "hardware removal". With the COVID-19 pandemic, an overall decline in performed orthopedic procedures was observed for the non-DE and the DE group. A significant reduction below the 95% prediction bands for the year 2020 could be shown for hardware removal and foot surgery (for DE), and for hardware removal, knee arthroplasty, foot surgery, and osteotomy (for non-DE). This study is the first to quantify inbound medical tourism in elective orthopedic surgery in Germany. The COVID-19 pandemic negatively affected many-but not all-areas of orthopedic surgery. It has to be seen how this negative trend will develop in the future.

Trends in Computer-Assisted Surgery for Total Knee Arthroplasty in Germany: An Analysis Based on the Operative Procedure Classification System between 2010 to 2021.

Alignment strategies for primary total knee arthroplasty (TKA) have changed significantly over time with a shift towards a more individualized alignment goal. At the same time, computer-assisted surgery (CAS) has gained interest for intraoperative control and accuracy in implant positioning and limb alignment. Despite the often discussed benefits and drawbacks of robotics and navigation for TKA, the routine use of these new devices on a day-to-day basis remains obscure. Therefore, nationwide hospital billing data based on the Operation Procedure Classification System (OPS) were retrieved from the Federal Statistical Office of Germany for the period from 2010 to 2021. OPS codes for primary total knee arthroplasty (OPS code: 5-822*) were further analyzed regarding the usage of computer navigation (additional OPS code: 5-988) or robotic devices (additional OPS code: 5-987). Gender and age at the time of surgery were also assessed. The results show a total of 2,226,559 primary TKAs were implanted between 2010 and 2021, of which 2,044,914 were performed conventionally (91.84% of all TKAs). A total of 170,276 TKAs were performed using navigation technique (7.65% of all TKAs) and another 11,369 TKAs were performed using robotics (0.51% of all TKAs). For the period from 2018 to 2021, a substantial increase in robot-assisted TKA (R-TKA) was observed, with an average increase rate of 84.74% per year, while the number of navigated TKAs declined (-3.67% per year). Computer-assisted surgery, and particularly robotics for TKA, are seeing growing popularity and stepwise translation into routine clinical use in Germany, with a steep increase rate of more than 80% per year since 2018. Nevertheless, the majority of TKAs are still performed using manual instrumentation, rendering conventional TKA the currently unchanged gold standard.

The influence of partial weight bearing on plantar peak forces using three different types of postoperative shoes.

BACKGROUND: Therapeutic shoes and partial weight bearing regimes are used after foot surgery to prevent the operated region from excessive load. It remains unclear to which extent partial weight bearing reduces the plantar peak forces. Therefore, we investigated the correlation of weight bearing and plantar peak forces in commonly used therapeutic shoes. METHODS: Three different weight bearing regimes (20 kg, 40 kg, full weight) were investigated in 20 healthy volunteers. Sensor insoles were used to measure peak forces of the forefoot, midfoot, heel and the complete foot using four kind of shoes (bandage shoe, forefoot relief shoe, short walker and standard sneaker). Peak forces were compared between shoes using one-way ANOVA. The influence of partial weight bearing relative to the peak forces was examined by linear regression analysis. RESULTS: All therapeutic shoes reduced significantly peak forces of the fore- and midfoot when compared to the reference shoe; the largest reduction was achieved by the forefoot relief shoe (-70 % at forefoot). Weight load and the resulting peak force showed a positive linear correlation for all regions and shoe types. Partial weight bearing significantly reduced the forefoot's force ratio compared to full weight bearing for all shoes except the forefoot relief shoe. CONCLUSIONS: Partial weight bearing is a strong instrument to reduce plantar peak forces of the forefoot, additionally to the proven offloading effect of therapeutic shoes.

Modifiable Individual Risks of Perioperative Blood Transfusions and Acute Postoperative Complications in Total Hip and Knee Arthroplasty.

BACKGROUND: The primary aim of this study was to identify modifiable patient-related predictors of blood transfusions and perioperative complications in total hip and knee arthroplasty. Individual predictor-adjusted risks can be used to define preoperative treatment thresholds. METHODS: We performed this retrospective monocentric study in orthopaedic patients who underwent primary total knee or hip arthroplasty. Multivariate logistic regression models were used to assess the predictive value of patient-related characteristics. Predictor-adjusted individual risks of blood transfusions and the occurrence of any perioperative adverse event were calculated for potentially modifiable risk factors. RESULTS: 3754 patients were included in this study. The overall blood transfusion and complication rates were 4.8% and 6.4%, respectively. Haemoglobin concentration (Hb, p < 0.001), low body mass index (BMI, p < 0.001) and estimated glomerular filtration rate (eGFR, p = 0.004) were the strongest potentially modifiable predictors of a blood transfusion. EGFR (p = 0.001) was the strongest potentially modifiable predictor of a complication. Predictor-adjusted risks of blood transfusions and acute postoperative complications were calculated for Hb and eGFR. Hb = 12.5 g/dL, BMI = 17.6 kg/m2, and eGFR = 54 min/mL were associated, respectively, with a 10% risk of a blood transfusion, eGFR = 59 mL/min was associated with a 10% risk of a complication. CONCLUSION: The individual risks for blood transfusions and acute postoperative complications are strongly increased in patients with a low preoperative Hb, low BMI or low eGFR. We recommend aiming at a preoperative Hb ≥ 13g/dL, an eGFR ≥ 60 mL/min and to avoid a low BMI. Future studies must show if a preoperative increase of eGFR and BMI is feasible and truly beneficial.

Diagnosis of Chronic Infection at Total Hip Arthroplasty Revision Is a Question of Definition.

PURPOSE: Contradicting definitions of periprosthetic joint infection (PJI) are in use. Joint aspiration is performed before total hip arthroplasty (THA) revision. This study investigated the influence of PJI definition on PJI prevalence at THA revision. Test quality of prerevision aspiration was evaluated for the different PJI definitions. METHODS: 256 THA revisions were retrospectively classified to be infected or not infected. Classification was performed according to the 4 different definitions proposed by the Musculoskeletal Infection Society (MSIS), the Infectious Diseases Society of America (IDSA), the International Consensus Meeting (ICM), and the European Bone and Joint Infection Society (EBJIS). Only chronic PJIs were included. RESULTS: PJI prevalence at revision significantly correlated with the applied PJI definition (p = 0.01, Cramer's V = 0.093). PJI prevalence was 20.7% for the MSIS, 25.4% for the ICM, 28.1% for the IDSA, and 32.0% for the EBJIS definition. For synovial fluid white blood cell count, the best ROC-AUC for predicting PJI was 0.953 in combination with the MSIS definition. CONCLUSION: PJI definition significantly influences the rate of diagnosed PJIs at THA revision. Synovial fluid white blood cell count is a reliable means to rule out PJI. In cases with a borderline high synovial white blood cell count before THA revision as the only sign of chronic PJI, an extended diagnostic work-up should be considered.

Influence of Tranexamic Acid on Elution Characteristics and Compressive Strength of Antibiotic-Loaded PMMA-Bone Cement with Gentamicin.

PURPOSE: The topical application of tranexamic acid (TXA) into the joint space during total joint arthroplasty (TJA) with no increase of complications, has been widely reported. We investigated the influence of TXA on antibiotic release, activity of the released antibiotic against a clinical isolate of S. aureus, and compressive strength of a widely used commercially prepared gentamicin-loaded cement brand (PALACOS R + G). METHOD: 12 bone cement cylinders (diameter and height = 6 and 12 mm, respectively) were molded. After curing in air for at least 1 h, six of the cylinders were completely immersed in 5 mL of fetal calf serum (FCS) and the other six were completely immersed in a solution consisting of 4.9 mL of FCS and 0.1 mL (10 mg) of TXA. Gentamicin elution tests were performed over 7 d. Four hundred µL of the gentamicin eluate were taken every 24 h for the first 7 d without renewing the immersion fluid. The gentamicin concentration was determined in a clinical analyzer using a homogeny enzyme immuno-assay. The antimicrobial activity of the eluate, obtained after day 7, was tested. An agar diffusion test regime was used with Staphylococcus aureus. Bacteria were grown in a LB medium and plated on LB agar plates to get a bacterial lawn. Fifty µL of each eluate were pipetted on 12-mm diameter filter discs, which were placed in the middle of the agar gel. After 24 h of cultivation at 37 °C, the zone of inhibition (ZOI) for each specimen was measured. The compressive strength of the cements was determined per ISO 5833. RESULTS: At each time point in the gentamicin release test, the difference in gentamicin concentration, obtained from specimens immersed in the FCS solution only and those immersed in the FCS + TXA solution was not significant (p = 0.055-0.522). The same trend was seen in each of the following parameters, after 7 d of immersion: (1) Cumulative gentamicin concentration (p < 0.297); (2) gentamicin activity against S. aureus (strongly visible); (3) ZOI size (mostly > 20 mm) (p = 0.631); and (4) compressive strength (p = 0.262). CONCLUSIONS: For the PALACOS R + G specimens, the addition of TXA to FCS does not produce significant decreases in gentamicin concentration, in the activity of the gentamicin eluate against a clinical isolate of S. aureus, the zone of inhibition of S. aureus, and in the compressive strength of the cement, after 7 d of immersion in the test solution.

Effect of Mobilization on the Day of Surgery After Total Hip Arthroplasty in Elderly, Obese, and Severely Diseased Patients.

BACKGROUND: Mobilization on the day of surgery after total hip arthroplasty (THA) is widely used. However, elderly, obese and severely diseased patients are often excluded from early mobilization. Therefore, it was our aim to investigate the effect of mobilization on the day of surgery with focus on these patients. METHODS: 167 patients underwent THA via direct anterior approach. Exclusion criterion was the use of wound drainage. The patients were randomly allocated to two groups. Day 0 group was mobilized 4 hours after surgery, day 1 group the day after surgery. Primary outcome was the time to readiness for discharge (TRD). Secondary outcome was the occurrence of adverse events (vertigo, nausea, vomiting, severe pain) on the day of surgery. Group comparisons were calculated with respect to elderly (age ≥75 years), obese (BMI ≥30 kg/m2) and severely diseased patients (ASA≥3). RESULTS: TRD was shorter in day 0 group (3.25 vs 3.99 days, P < .01). The rate of adverse events on the day of surgery was similar in both groups (0.28 vs 0.25, P = .73). TRD differences were higher within all subgroups (3.85vs4.81; 3.25vs4.39; 4.08vs5.11days) while the rate of immediate adverse events was reduced (0.15vs0.24; 0.25vs0.3; 0.25vs0.33). Within 90 days 3 patients of group 0 underwent revision surgery, none of group 1 (P = .12). CONCLUSION: Mobilization on the day of surgery reduces the TRD without increasing the rate of immediate adverse events, regardless of age, BMI and ASA score. Future studies are needed to investigate if early mobility increases the 90-days complication rate.

Perioperative predictability of unsatisfactory functional outcomes 6 months after hip arthroplasty.

BACKGROUND: Aiming at an early identification of patients with an unsatisfactory outcome after hip arthroplasty we investigated the pre-, intra- and early postoperative predictability. METHODS: Using logistic regression models at nine different time points we calculated the area under the curve of the receiver operating characteristic (ROC-AUC) to compare the predictability of an unsatisfactory outcome. RESULTS: The predictability of unsatisfactory outcomes increased significantly from a ROC-AUC (95% CI) of 0.73 (0.62-0.84) in the preoperative setting to 0.85 (0.77-0.94) on day 2 after surgery. CONCLUSION: Most of the patients with unsatisfactory outcomes can be identified during the first days after surgery.

Do not exchange the spacer during staged TKA exchange!

PURPOSE: The aim of this study was to investigate the reinfection rate and risk factors for septic failure after two-stage exchange for chronic periprosthetic joint infections of primary total knee arthroplasties. Reinfections should be classified as new infection or as infection recurrence after two-stage exchange. METHODS: We performed a retrospective study of 60 knees with chronic periprosthetic joint infections. Follow-up information was extracted from the departments electronic database. RESULTS: The reinfection rate after a mean follow-up of 35.6 months (1-135) was 20.0%. The only significant risk factor for reinfection was spacer exchange during two-stage exchange (OR = 10.42; p = 0.001). Of the 12 cases with reinfection 6 cases were classified as new infection and 2 as infection recurrence. CONCLUSIONS: Patient specific factors for reinfection remain furtive. If a spacer exchange is preformed, the risk of reinfection increases. Culture results indicate that the benefit of spacer exchanges during two-stage exchange is highly questionable, particularly because reinfection is an issue of new infection rather than of infection recurrence.

Impact of Tranexamic Acid on Chondrocytes and Osteogenically Differentiated Human Mesenchymal Stromal Cells (hMSCs) In Vitro.

The topical application of tranexamic acid (TXA) helps to prevent post-operative blood loss in total joint replacements. Despite these findings, the effects on articular and periarticular tissues remain unclear. Therefore, this in vitro study examined the effects of varying exposure times and concentrations of TXA on proliferation rates, gene expression and differentiation capacity of chondrocytes and human mesenchymal stromal cells (hMSCs), which underwent osteogenic differentiation. Chondrocytes and hMSCs were isolated and multiplied in monolayer cell cultures. Osteogenic differentiation of hMSCs was induced for 21 days using a differentiation medium containing specific growth factors. Cell proliferation was analyzed using ATP assays. Effects of TXA on cell morphology were examined via light microscopy and histological staining, while expression levels of tissue-specific genes were measured using semiquantitative RT-PCR. After treatment with 50 mg/mL of TXA, a decrease in cell proliferation rates was observed. Furthermore, treatment with concentrations of 20 mg/mL of TXA for at least 48 h led to a visible detachment of chondrocytes. TXA treatment with 50 mg/mL for at least 24 h led to a decrease in the expression of specific marker genes in chondrocytes and osteogenically differentiated hMSCs. No significant effects were observed for concentrations beyond 20 mg/mL of TXA combined with exposure times of less than 24 h. This might therefore represent a safe limit for topical application in vivo. Further research regarding in vivo conditions and effects on hMSC functionality are necessary to fully determine the effects of TXA on articular and periarticular tissues.

The human arthritic hip joint is a source of mesenchymal stromal cells (MSCs) with extensive multipotent differentiation potential.

BACKGROUND: While multiple in vitro studies examined mesenchymal stromal cells (MSCs) derived from bone marrow or hyaline cartilage, there is little to no data about the presence of MSCs in the joint capsule or the ligamentum capitis femoris (LCF) of the hip joint. Therefore, this in vitro study examined the presence and differentiation potential of MSCs isolated from the bone marrow, arthritic hyaline cartilage, the LCF and full-thickness samples of the anterior joint capsule of the hip joint. METHODS: MSCs were isolated and multiplied in adherent monolayer cell cultures. Osteogenesis and adipogenesis were induced in monolayer cell cultures for 21 days using a differentiation medium containing specific growth factors, while chondrogenesis in the presence of TGF-ß1 was performed using pellet-culture for 27 days. Control cultures were maintained for comparison over the same duration of time. The differentiation process was analyzed using histological and immunohistochemical stainings as well as semiquantitative RT-PCR for measuring the mean expression levels of tissue-specific genes. RESULTS: This in vitro research showed that the isolated cells from all four donor tissues grew plastic-adherent and showed similar adipogenic and osteogenic differentiation capacity as proven by the histological detection of lipid droplets or deposits of extracellular calcium and collagen type I. After 27 days of chondrogenesis proteoglycans accumulated in the differentiated MSC-pellets from all donor tissues. Immunohistochemical staining revealed vast amounts of collagen type II in all differentiated MSC-pellets, except for those from the LCF. Interestingly, all differentiated MSCs still showed a clear increase in mean expression of adipogenic, osteogenic and chondrogenic marker genes. In addition, the examination of an exemplary selected donor sample revealed that cells from all four donor tissues were clearly positive for the surface markers CD44, CD73, CD90 and CD105 by flow cytometric analysis. CONCLUSIONS: This study proved the presence of MSC-like cells in all four examined donor tissues of the hip joint. No significant differences were observed during osteogenic or adipogenic differentiation depending on the source of MSCs used. Further research is necessary to fully determine the tripotent differentiation potential of cells isolated from the LCF and capsule tissue of the hip joint.

Revision knee arthroplasty with rotating hinge systems in patients with gross ligament instability.

PURPOSE: The clinical and radiographic outcomes after revision total knee arthroplasty (TKA) for instability with two rotating hinge knee prostheses were compared. METHODS: Fifty-one patients revised for TKA instability were prospectively randomized to either the Link Endo-Model (N = 26) or the EnduRo (N = 25). Clinical and radiographic outcome scores were compared pre-operatively and at 12 months' follow-up. Failure mechanisms were recorded. RESULTS: Age, BMI, operation, and tourniquet-time did not differ significantly between groups. Radiographic evaluation demonstrated correct implant alignment. The Endo-Model was implanted with a higher slope (p = 0.0001) and the mechanical lower extremity axis was straighter (p = 0.0323). Except for the patient function Knee Society Score and the Physical Health Component Summary Score in the EnduRo group, all clinical scores (range of motion/knee function Knee Society Score/Oxford Knee Score/Visual Analog Scale/Mental Health Component Summary Score) improved significantly for both prosthesis designs during the follow-up period. The Visual Analog Scale and Mental Health Component Summary score were significantly better (p = 0.045 and p = 0.0148) in the Endo-Model group at the 12 months' follow-up. In the EnduRo group 2 patients (8%) and in the Endo-Model group 1 patient (3.8%) had to be revised for infection. CONCLUSION: Both prosthetic designs provide significant improvement in pain and function scores after TKA revision for gross instability. We found slight advantages in favor of the Endo-Model; however, no design yielded superior results throughout the study.

Development, validation and utility of a simulation model of the nociceptive flexion reflex threshold.

OBJECTIVE: A variety of algorithms is used for nociceptive flexion reflex threshold (NFRT) estimation, but their estimation accuracy is unknown. We developed a computer based simulation model of the NFRT to quantify and compare the accuracy of available estimation algorithms. METHODS: This simulation model is based on basic characteristics of the NFRT and specified by data collected from 60 healthy volunteers. We validated the model by comparing simulated data with data obtained independently in another volunteer population. The model was used to quantify the accuracy of previously published NFRT estimation algorithm for three NFRT variabilities representing sensory deprivation, distraction and general anaesthesia. RESULTS: The dynamic staircase algorithm obtained most accurate NFRT estimates during all NFRT variabilities. The number of stimuli applied can be chosen higher to increase estimate precision or lower to reduce measurement time. CONCLUSIONS: Our simulation model is a valid tool to measure the accuracy of NFRT estimation algorithms. It can be applied to analyse and develop algorithms. The dynamic staircase algorithm shows the highest precision in NFRT estimation and is recommended for NFRT studies. SIGNIFICANCE: Using optimized NFRT estimation algorithms increases precision in clinical and experimental NFRT studies and might therefore reduce the measurement effort necessary.