Michael Müller

Background: Despite the general success of total knee arthroplasty (TKA), addressing periprosthetic joint infection (PJI) and the resulting long-term complications is a growing medical need given the aging population and the increasing demand for arthroplasty. A larger proportion of patients face revision surgery because of the long-term complication of aseptic loosening despite clearance of the infection. The pathomechanisms leading to prosthetic loosening are not understood as it has been widely assumed that the bone stock recovers after explantation revision surgery. While clinical observations suggest a reduced osteogenic potential in patients with PJI, knowledge regarding the relevant biology is sparse. In the present study, we investigated the inflammatory impact of PJI on the bone and bone marrow in the vicinity of the joint. Additionally, we evaluated changes in the local inflammatory environment in a 2-stage exchange at both explantation and reimplantation. Methods: In this study, we analyzed 75 human bone and bone-marrow specimens (obtained from 65 patients undergoing revision arthroplasty with cement for the treatment of PJI) for markers of inflammation. Samples were analyzed using hematoxylin and eosin overview staining, fluorescent immunohistochemical staining, flow cytometry, and polymerase chain reaction (PCR). Results: Leukocyte prevalence was significantly elevated at explantation (femur, +218.9%; tibia, +134.2%). While leukocyte prevalence decreased at reimplantation (femur, −49.5%; tibia, −34.2%), the number of cells remained significantly higher compared with the control group (femur, +61.2%; tibia, +54.2%). Expression of inflammatory markers interleukin (IL)-1α (femur, +2,748.7%; tibia, +1,605.9%), IL-6 (femur, +2,062.5%; tibia, +2,385.7%), IL-10 (femur, +913.7%; tibia, +897.5%), IL-12 (femur, +386.1%; tibia, +52.5%), IL-18 (femur, +805.3%; tibia, +547.7%), and tumor necrosis factor (TNF)-α (femur, +296.9%; tibia, +220.9%) was significantly elevated at prosthesis explantation in both femoral and tibial specimens. Expression remained significantly elevated at reimplantation for all inflammatory markers except IL-12 compared with the control group. Conversely, there were only limited inflammatory changes in the bone marrow environment. Conclusions: The present study demonstrated a strong and lasting upregulation of the proinflammatory environment in the joint-surrounding osseous scaffold in patients with PJI. Our data suggest that modulating the inflammatory environment has substantial potential to improve the clinical outcome in affected patients.

Intra-operative fractures in knee revision surgery are relatively rare and have not been well studied. They may occur during joint exposition, removal of the prosthesis or cement, or implantation of trial or original components. The fractures affect both the metaphyseal area and diaphysis of the tibia and femur. Tibial fractures are slightly more common than femur fractures. On the femur, the medial condyle is most frequently affected, followed by the femur diaphysis. The use of non-cemented stems is associated with a greater risk of intra-operative diaphyseal fractures than that of cemented stems. Overall, women and patients with an osteopenic bone structure have a higher risk of fractures. It is common that fractures are diagnosed post-operatively. In these cases, conservative therapy may be successful, depending on the stability of the prosthesis and bones. The most common surgical fixation options are cerclages and screws, followed by stem extensions for bridging the fracture. Plate fixation or use of strut grafts are also sensible therapy options. Overall, intraoperative fractures have a high healing potential with stable and good joint function. The revision rate is still 15%, which is most often caused by peri-prosthetic infection.

Systemic juvenile idiopathic arthritis (SJIA) is a severe childhood-onset inflammatory disease characterized by arthritis accompanied by systemic auto-inflammation and extra-articular symptoms. While recent advances have unraveled a range of risk factors, the pathomechanisms involved in SJIA and potential prognostic markers for treatment success remain partly unknown. In this study, we included 70 active SJIA and 55 healthy control patients from the National Center for Biotechnology Information to analyze for differentially expressed genes (DEGs) using R. Functional enrichment analysis, protein-protein interaction (PPI), and gene module construction were performed for DEGs and hub gene set. We additionally examined immune system cell composition with CIBERSORT and predicted prognostic markers and potential treatment drugs for SJIA. In total, 94 upregulated and 24 downregulated DEGs were identified. Two specific modules of interest and eight hub genes (ARG1, DEFA4, HP, MMP8, MMP9, MPO, OLFM4, PGLYRP1) were screened out. Functional enrichment analysis suggested that complex neutrophil-related functions play a decisive role in the disease pathogenesis. CIBERSORT indicated neutrophils, M0 macrophages, CD8+ T cells, and naïve B cells to be relevant drivers of disease progression. Additionally, we identified TPM2 and GZMB as potential prognostic markers for treatment response to canakinumab. Moreover, sulindac sulfide, (-)-catechin, and phenanthridinone were identified as promising treatment agents. This study provides a new insight into molecular and cellular pathogenesis of active SJIA and highlights potential targets for further research.

Background: Periprosthetic joint infection (PJI) is a common yet severe complication after total knee arthroplasty (TKA). Surgical intervention and antibiotic therapy are obligatory to achieve successful, infection-free outcome. Compared to the outcomes after primary TKA, prosthesis failure rates are drastically increased after PJI-dependent revision surgery. Recurrent PJI and aseptic loosening are the most common reasons for prosthesis failure after revision TKA. An open question is the influence of the patients’ gender on long-term prosthesis survival after revision surgery. Additionally, it is unknown whether gender-related parameters and risk factors or differences in treatment are responsible for potential differences in outcome after revision arthroplasty. Patients and Methods: In this report, 109 patients that received TKA revision surgery due to PJI were retrospectively analyzed. We used clinical, paraclinical and radiological examinations to study the influence of gender on the long-term complications aseptic loosening and recurrent PJI after PJI-dependent revision arthroplasty. Results: While overall prosthesis failure rates and risk of recurrent PJI did not differ between genders, the long-term risk of aseptic loosening was significantly elevated in female patients. Postoperative coronal alignment was significantly more varus for women later diagnosed with aseptic loosening. Besides coronal alignment, no gender-dependent differences in clinical presentation or treatment were observed. Conclusions: Female patients displayed a significantly increased risk for aseptic loosening after PJI-dependent revision TKA. The observed gender-dependent differences in long-term outcome in our study support theories surrounding the role of bone metabolism in the development of aseptic loosening. Our data suggest that further research on a female design for PJI-dependent revision prostheses is warranted.

The corona virus has spread worldwide since it first appeared in China and represents a pandemic of unprecedented magnitude. The pandemic has not only social and economic effects, but even more impressive effects on the health system. If the virus spreads uncontrollably and rapidly, there is a risk of an unpredictable increase of patients with COVID-19 disease requiring hospital treatment. The capacities of a hospital can quickly reach the limit and consequently patients can no longer be adequately treated. Therefore, in the acute phase of the pandemic, it is necessary to release all hospital resources for the treatment of COVID-19 patients. Strict hygiene regulations must also be observed in order to prevent the virus from spreading unexpectedly in the hospital in order to protect patients and hospital staff. Elective operations and outpatient clinics must be cancelled in the acute phase. Special hygiene measures must be observed for urgent and unpostponable operations. These relate to the admission of the patients, the accommodation in the ward and the operative care in the operating room. In the post-acute phase, a normal surgical program can be resumed step by step. In this phase, however, clear hygiene regulations must also be observed. Regular medical meetings taking into account the current pandemic situation and the occurrence of new infections must be carried out in the hospital and the occupancy of the ward and operating room adjusted accordingly. To what extent the situation for the treatment of patients in orthopedics and trauma surgery will normalize cannot be predicted at the present time.

(1) Background: Degeneration of the hip abductor mechanism, a well-known cause of functional limitation, is difficult to treat and is associated with a reduced health-related quality of life (HRQOL). The gluteus maximus muscle flap is a treatment option to support a severely degenerative modified gluteus medius muscle. Although several reports exist on the clinical outcome, there remains a gap in the literature regarding HRQOL in conjunction with functional results. (2) Methods: The present study consists of 18 patients with a mean age of 64 (53‒79) years, operatively treated with a gluteus maximus flap due to chronic gluteal deficiency. Fifteen (83%) of these patients presented a history of total hip arthroplasty or revision arthroplasty. Pre and postoperative pain, Trendelenburg sign, internal rotation lag sign, trochanteric pain syndrome, the Harris Hip Score (HHS), and abduction strength after Janda (0‒5) were evaluated. Postoperative patient satisfaction and health-related quality of life, according to the Short Form 36 (SF-36), were used as patient-reported outcome measurements (PROMs). Postoperative MRI scans were performed in 13 cases (72%). (3) Results: Local pain decreased from NRS 6.1 (0–10) to 4.9 (0–8) and 44% presented with a negative Trendelenburg sign postoperatively. The overall HHS results (p = 0.42) and muscular abduction strength (p = 0.32) increased without significance. The postoperative HRQOL reached 46.8 points (31.3–62.6) for the mental component score and 37.1 points (26.9–54.7) for the physical component score. The physical component results presented a high level of positive correlation with HHS scores postoperatively (R = 0.88, p < 0.001). Moreover, 72% reported that they would undergo the operative treatment again. The MRI overall showed no significant further loss of muscle volume and no further degeneration of muscular tissue. (4) Conclusions: Along with fair functional results, the patients treated with a gluteus maximus flap transfer presented satisfying long-term PROMs. Given this condition, the gluteus maximus muscle flap transfer is a viable option for selected patients with chronic gluteal deficiency.

Purpose Several studies describe risk factors for primary periprosthetic joint infection (PJI) and general treatment outcome factors like microbe spectrum or patient-specific risk factors. However, these general and patient dependent findings cannot solely explain all cases of infection persistence after a prior septic revision. This study analyzes possible specific and patient independent reasons for failure after revisions for PJI in knee and hip arthroplasty. Methods In a prospective analysis all patients were included that were treated: (1) at our department, (2) with a two-stage exchange, (3) between 2013 and 2017, (4) due to an infection persistence after a previous revision for PJI. Possible reasons for infection persistence were identified using a checklist algorithm, based on international guidelines. Results 70 patients with infection persistence could be included (44 knee joints, 26 hip joints). The average age was 71 years, the CCI (Charlson Comorbidity Index) 2.8 and the ASA (American Society of Anesthesiologists) score 2.7. In 85% at least one possible reason for patient independent infection persistence could be identified analyzing the previous infection therapy: (1) 50% inadequate therapy concept (n = 35), (2) 33% inadequate surgical debridement (n = 23), (3) 30% inadequate antimicrobial therapy (n = 21), (4) 13% missed external bacterial primary focus (n = 9). After the individual failure analysis, all 70 patients were treated with a two-stage exchange in our department and in 94.9% infection freedom could be achieved (34.3 ± 10.9 months follow-up). Conclusions In the majority of failed revisions with subsequent infection persistence at least one possible patient independent failure cause could be identified. The entire previous therapy should be critically reviewed following failing revisions to optimize the outcome of septic revisions. By using a checklist algorithm, high rates of infection freedom were achieved.

Background: With increasing life expectancy, the demand for knee replacement is continuously rising. Despite the use of antibiotic prophylaxis and improved aseptic surgical techniques, periprosthetic joint infection (PJI) still occurs in 1% to 5% of patients after primary arthroplasty. An open question is the influence of PJI and resulting surgical procedures on the occurrence of long-term complications such as aseptic loosening. Patients needing multiple revision surgeries are especially at risk for decreases in bone mass and damage to the medullary cavity. Thus, we theorized that prior surgeries on the affected knee increase the risk of aseptic loosening in patients with PJI.Methods: We retrospectively analyzed the cases of 100 patients who underwent total knee replacement exchange surgery as a result of PJI. In addition to clinical, paraclinical, and radiographic examination, we assessed comorbidities and the number of prior surgeries.Results: Prosthetic survival was drastically decreased after PJI-related revision arthroplasty: during the first 7.3 years after reimplantation, 22% and 16% of all patients had aseptic loosening and recurrent PJI, respectively. The prevalence of aseptic loosening was 27.8% for female and 15.2% for male patients. A significant association between increasing patients’ American Society of Anesthesiologists (ASA) classification and prosthetic failure rates was found, as was a strong correlation between number of prior surgeries and aseptic looseningConclusions: In this study, we found notable rates of aseptic loosening and recurrent PJI following PJI-related revision arthroplasty. The difference in the rate of aseptic loosening among male and female patients supports theories of the role of bone metabolism in the development of aseptic loosening. The economic and clinical burdens of prosthetic failure make it paramount to gain a better understanding of bone metabolism in PJI. Additional research should address the need to optimize treatment strategies to increase prosthetic survival.Level of Evidence: TherapeuticLevel IV. See Instructions for Authors for a complete description of levels of evidence.

Background: Developmental dysplasia of the hip (DDH) can lead to pain and premature secondary osteoarthritis at an early stage. Joint-preserving osteotomy is an established solution to this problem. In contrast, a conservative approach would result in pain persistence, ultimately raising the patients question for a possible date of expected prosthesis implantation.The aim of the study was to identify the relationship between the dysplastic hip anatomy and the time of prosthesis implantation in order to enable prognostic predictions in younger patients with symptomatic DDH.Materials and methods: Data from 129 hips who received THA due to secondary DDH osteoarthritis were evaluated. The preoperative hip anatomy was evaluated for AI and LCE angle. Multiple linear regression analyses were then used to correlate the influence of these parameters with the patient’s age at the time of surgery. In addition, a graphical relationship was derived by the method of power least squares curve fitting with second-degree polynomials.Results: The mean age for THA was 54.3 ± 11 years. The time of surgery correlated significantly with LCE (0.37) and AI (− 0.3) (p < 0.001). The mean age of patients with LCE angle ≤ 10° was 41.9 ± 14.0 years, for LCE 11–20° 52.7 ± 9.5 years, and for LCE 21–30° 57.0 ± 10.3 years. The following formula could then be determined for the calculation of the potential patient age at the time of THA as a function of LCE angle: age pTHA = 40.2 + 0.8 × LCE angle − 0.01 × (LCE angle)².Conclusion: A significant correlation between the extent of dysplasia and the time of prosthesis implantation was identified. In particular, the LCE and the AI correlated strongly with the time of implantation. The more dysplastic the angles were, the sooner the THA was necessary. Using the calculations presented in this study, the probable age of prosthesis implantation can be prognosticated and included in a counseling session about treatment options for DDH.