Dominic Simon

Topical vancomycin in primary total knee arthroplasty remains an investigational and controversial strategy because clinical evidence regarding infection prevention and wound complications is conflicting. This pilot study explored whether prolonged exposure to vancomycin-containing serum lubricant was associated with altered gravimetric wear of vitamin E-stabilized ultra-high-molecular-weight polyethylene (UHMWPE) tibial inserts. Eight identical bicondylar total knee arthroplasty systems were evaluated in two condition-specific four-station simulator runs: serum control and vancomycin-containing lubricant. In each run, three inserts underwent dynamic loading for 5.0 million cycles and one insert served as the shared load-soak control. For the exposed condition, 1 g of crystalline vancomycin was dissolved in 10 mL of distilled water and added to the serum lubricant to achieve a final lubricant volume of 300 mL, corresponding to a nominal vancomycin concentration of 3.33 mg/mL. The complete lubricant was renewed every 0.5 million cycles. Inserts were preconditioned in serum without vancomycin, and serial micro-CT handling was performed only in the vancomycin condition. The mean measured wear rate was 2.21 ± 0.92 mg/million cycles in the vancomycin-containing lubricant condition and 6.80 ± 3.07 mg/million cycles in the serum control condition, corresponding to a mean between-condition difference of − 4.59 mg/million cycles. All three wear-rate estimates for the serum control condition exceeded those obtained with vancomycin-containing lubricant. Because the two conditions were evaluated in separate simulator runs and differed in preconditioning and micro-CT handling, the observed between-condition difference cannot be attributed specifically to vancomycin. These findings should therefore be interpreted as preliminary descriptive evidence and do not permit conclusions regarding non-inferiority, clinical safety, or infection-prevention efficacy.

Background: Periprosthetic joint infections (PJIs) remain a significant complication following total hip arthroplasties (THAs), affecting patient outcomes and healthcare costs. The accurate classification of PJIs is crucial for guiding treatment decisions and improving patient management. The TNM classification system, commonly used in oncology, has previously been adapted for PJI to enhance our understanding of infection severity and is progressively used as PJI-TNM. Purpose: This study evaluates the applicability of the PJI-TNM classification in a cohort of 185 periprosthetic hip joint infections, including 84 acute and 101 chronic cases. Methods: In this retrospective study, we analyzed 84 cases of acute and 101 cases of chronic periprosthetic hip joint infections. Each case was independently classified according to the PJI-TNM framework by three observers. A second round of scoring was performed 90 d later to assess the intra-observer concordance. The objective was to evaluate the utility of this classification in distinguishing between acute and chronic infections, predicting outcomes, and informing treatment strategies. Furthermore, intra- and inter-observer reliability were evaluated. Results: For acute PJIs we found a high inter-observer and intra-observer reliability for both the first and second evaluation (κ 0.78 and 0.89, respectively). In addition, the intra-observer analysis showed a very good correlation (κ 0.86–0.96). For chronic PJIs the intra-observer reliability was κ of 0.85–0.96, whereas inter-observer reliability was lower with κ of 0.75–0.85. Conclusion: The PJI-TNM classification demonstrated strong intra-observer and substantial inter-observer reliability across both acute and chronic infections, supporting its use as a robust and reproducible framework for PJI classification.

Aims: The effect of femoral head length on implant survival in total hip arthroplasty (THA) has been little studied so far. Longer heads may increase taper corrosion and reflect intraoperative complexity. This study evaluated factors associated with the use of extra-long heads (≥ XL) and their impact on implant survival. Methods: We analyzed 562,001 primary THA from the German Arthroplasty Registry. Subgroup analyses were performed by hospital annual primary THA volume (≤ 250, 251–500, ≥ 501), surgical indication (primary osteoarthritis [OA] vs. femoral neck fracture [FNF]), and fixation method (cemented vs. cementless). Logistic regression identified factors associated with ≥ XL head use, and implant survival was compared between head lengths using Kaplan–Meier analysis in both subgroups and the overall cohort. Results: The use of ≥ XL femoral heads decreased with increasing hospital volume (5.4% low, 4.5% medium, 3.0% high; p < 0.001). Rates were higher in FNF than OA across all volumes (8.1% vs. 4.7% in low-volume hospitals; 5.0% vs. 2.7% in high-volume hospitals). Cemented fixation was independently associated with higher odds of ≥ XL head use (OR 1.14, 95% CI 1.09–1.18, p < 0.001), with additional predictors including male sex (OR 2.13, 95% CI 2.06–2.19), BMI ≥ 40 (OR 1.94, 95% CI 1.77–2.12), higher Elixhauser comorbidity score (OR 1.09, 95% CI 1.04–1.15), and surgery for FNF (OR 1.92, 95% CI 1.83–2.02), while treatment at high-volume hospitals was associated with lower odds (OR 0.56, 95% CI 0.54–0.58). Kaplan–Meier analysis revealed higher cumulative revision rates with ≥ XL heads (7.2% vs. 4.5% at 9 years), consistent across all subgroups. Conclusion: The use of femoral heads ≥ XL was independently associated with lower hospital THA volume, femoral neck fracture, cemented fixation, male sex, higher BMI, and greater comorbidity burden. Their implantation was also linked to higher revision rates, suggesting that ≥ XL heads may serve as a surrogate marker for increased revision risk after primary THA.

Case: We describe the case of a 78‐year‐old multimorbid male patient with a history of right‐sided total hip arthroplasty in 1996 and homologous acetabular bone graft reconstruction according to Slooff in 2009. In December 2024, the patient presented with acute right hip pain due to acute on chronic loosening of the implant. Diagnostic workup revealed a low‐grade periprosthetic joint infection with Cutibacterium acnes . After preoperative optimization, the patient underwent implant explantation and conversion to a Girdlestone state. Histological analysis of the explanted Slooff augment showed nonvital and nonincorporated cancellous bone, lacking osteocytes within the bone lacunae, indicating the absence of viable bone and remodeling. Conclusion: Reconstruction of acetabular defects, particularly in cases of severe bone loss or medial wall protrusion, remains a significant challenge in revision total hip arthroplasty (rTHA). The Slooff technique, involving morselized homologous bone grafts impacted into the acetabular defect and stabilized with a cemented cup, has been widely adopted for such cases due to its relative simplicity and promising midterm outcomes. However, the biological and mechanical long‐term integration of such constructs, as observed in this case, remains a topic of ongoing debate.

Purpose: Children with chronic diseases are at a significant risk of radiation exposure. This cohort study evaluates the effectiveness and reliability of ultrasonography (US) for detecting femoral head decentration in children with cerebral palsy (CP) and developmental dysplasia of the hip (DDH), comparing it with traditional radiographic techniques to reduce radiation exposure. Methods: A total of 169 patients were enrolled in the study. Both hips were evaluated in 158 patients, resulting in a total of 327 hips. Patients underwent clinical and radiological assessments, including standardized US. Parameters measured included the ventral and lateral bony and cartilaginous ultrasonographic migration indices (bUMI and cUMI), which were compared with standardized radiographic indices (Reimers index (RI) and extrusion index (EI)). Results: The lateral bUMI (17.4%) was significantly lower than the lateral cUMI (25.9%). RI values were lower than EI values (16.8% vs. 27.7%). No significant differences were observed between the bUMI and RI, or between the cUMI and EI, indicating the reliability of US. All lateral parameters correlated well with the lateral centre-edge angle (LCE). Positive correlations were found between the lateral cUMI and the radiological indices, with high inter- and intra-rater reliability (ICC). Significant differences in lateral and ventral UMIs were noted when comparing DDH and CP patients. Conclusion: US is a reliable alternative to radiography for hip surveillance in detecting hip decentration in children with CP and DDH. It reduces radiation exposure while maintaining diagnostic accuracy. The findings support the adoption of US in clinical practice to improve early diagnosis and intervention.

Introduction: With the increasing number of primary total hip arthroplasties (THAs), the incidence of associated complications has risen, with periprosthetic joint infection (PJI) being among the most severe. The influence of surgical approach on infection risk remains debated; however, its effect on the microbiological profile of PJIs is not well examined. This study aimed to evaluate whether the primary surgical approach affects the spectrum of microorganisms involved in acute postoperative periprosthetic hip joint infections in a retrospective single-center cohort. Methods: A total of 76 patients who underwent revision surgery for PJI following THA between January 2013 and June 2024 were retrospectively reviewed. After applying exclusion criteria, patients were categorized based on the initial surgical approach: lateral vs. direct anterior/anterolateral. The microbiological spectrum was compared between groups using Fisher's exact test. Demographic characteristics and their associations with surgical approach and pathogen type were also analyzed. Results: No significant differences were found in the microbiological spectrum between surgical approaches. Similarly, there was no significant correlation between surgical approach and the occurrence of Gram-positive or Gram-negative organisms. Body mass index (BMI) was not associated with variations in pathogen distribution, suggesting that obesity does not influence the microbiological profile of PJI. Discussion: These findings suggest that the microbiological characteristics of acute postoperative PJI are independent of the primary surgical approach. Minimally invasive anterior techniques do not appear to carry an increased microbiological risk. Additionally, BMI does not influence the microbial spectrum of infection. Level of evidence: this is a retrospectively registered cohort study with a Level III level of evidence.

Purpose: Meniscal tears are common knee injuries and a major risk factor for secondary osteoarthritis. Recently, there has been a paradigm shift toward meniscal preservation, reflecting the meniscus's vital role. In this context, tissue engineering approaches such as the development of meniscal scaffolds have gained attention. However, to reduce the immune response and improve biocompatibility, decellularization of allografts, while preserving the histoarchitectural and meniscal properties, is essential. The current study aimed to evaluate the effectiveness of decellularization and its impact on the biomechanical properties of the human meniscus. Methods: Twenty‐one human meniscus specimens were collected between July and December 2023 during total knee arthroplasty. Preoperative MRI was performed to verify meniscal integrity. The specimens were decellularized using a sodium dodecyl sulphate (SDS) protocol and compared to native meniscus samples in terms of cell count, assessed through hematoxylin and eosin staining, and biomechanical properties, specifically Young's modulus, measured using a universal testing machine (Zwick Z010). Results: The cell count in the decellularized menisci was 11 cells/mm² (SD = 13; 95% CI: 2–20), representing a significant reduction compared to the native meniscus samples, which had a cell count of 111 cells/mm² (SD = 42; 95% CI: 81–141; p < 0.01). Young's modulus of elasticity was 35.3 versus 36.8 MPa in the anterior region ( p = 0.8), 32.6 versus 35.6 MPa in the central region ( p = 0.7) and 36.5 versus 35.8 MPa in the posterior region ( p = 0.9) for native versus decellularized samples, respectively. Conclusions: This study demonstrated that the modified SDS‐based decellularization protocol effectively decellularizes the human meniscus. Moreover, the decellularized tissue retained biomechanical properties comparable to those of native meniscus tissue. Tissue decellularization is a promising technique in regenerative medicine, enabling the use of scaffolds for tissue repair, particularly in applications such as meniscus transplantation following meniscectomy. Level of Evidence: Level III, controlled laboratory study.

Introduction: Performing total joint replacements (TJR) in patients with solid organ transplantations (SOT) is associated with an increased risk of complications and reoperation. The aim of this study is to report on implant survivorship, patient survivorship, and complication rates for total knee arthroplasty (TKA) and total hip arthroplasty (THA) performed in heart, lung, liver and kidney transplant recipients. Materials and methods: Forty patients with heart, lung, liver, or kidney transplants who underwent primary THA or TKA between January 1, 2013, and July 31, 2023, were included. Implant survivorship, reoperation-free survivorship, patient survivorship, and complication rates were compared between the subgroups. Results: At a mean follow-up of 5.18 years, Implant survivorship and reoperation-free survival for the entire cohort at the last follow-up were 97.5% and 85%, respectively. Kaplan–Meier survival estimates demonstrated 5- and 10-year reoperation-free survival rates of 86.5% (95% CI: 76%–98.4%) and 57.6% (95% CI: 25.6%–100%), respectively. The lung transplant group had the shortest reoperation-free survival, although not statistically significant (p = 0.07), a significantly higher risk of reoperation, with a hazard ratio (HR) of 6.9 (95% CI: 1.1–41.2, p = 0.04) and both the lowest 5-year patient survivorship at 68.6% (p = 0.04) and the highest risk of death after TJR with a HR of 7 (95% CI: 1.2–45.5, p = 0.03). Conclusion: Patients with SOT exhibit excellent mid-term implant survivorship, with a rate of 97.5%. Lung transplant recipients show the lowest rates of both reoperation-free survival and overall patient survivorship compared to heart, kidney, and liver transplant recipients. Despite this, the 90-day complication rates are similar across all organ groups.

Background/Objectives: Musculoskeletal aging can clinically hardly be distinguished from degenerative disease, especially if symptoms are nonspecific, like lower back pain and reduced physical resilience. However, age-related changes are considered to be physiological until they cause osteoporotic fractures or sarcopenia-related restrictions. This radio-anatomic investigation examines whether findings in lumbar magnetic resonance imaging (MRI) mirror age- and sex-related musculoskeletal differences that help to identify the onset of sarcopenia. Methods: Lumbar MRI investigations from 101 women and 101 men were retrospectively evaluated for vertebral and muscular cross-sectional diameter sizes and T2-signal intensities (“T2-brightness”) in axial sections in the L5-level. The results were correlated with the individual’s age to find specific alterations that were indicative of sarcopenia or attributable to the aging process. Results: In women (average age 62.6 (34–85) years), musculoskeletal cross-sectional area sizes and diameters were significantly smaller (p < 0.00001) compared to those in men (average age 57.0 (21–90) years). The most pronounced structural age-related change was the increasing mean posterior paravertebral muscle brightness (MPPVB), which exceeded the mean vertebral brightness (MVB) earlier and to a greater extent in women than in men (p < 0.00001). The brightness difference (∆MVB − MPPVB) was found to indicate (pre-)sarcopenia at values below 25. Conclusions: Significant age-related deterioration in muscle quantity and quality was more obvious in women, correlated with the onset of menopause, and progressed to lower levels during aging.