Tilman Pfitzner

Functional Comparison of Chronological and In Vitro Aging: Differential Role of the Cytoskeleton and Mitochondria in Mesenchymal Stromal Cells

Mesenchymal stromal cells (MSCs) are of high relevance for the regeneration of mesenchymal tissues such as bone and cartilage. The promising role of MSCs in cell-based therapies and tissue engineering appears to be limited due to a decline of their regenerative potential with increasing donor age, their limited availability in human tissues and the need of in vitro expansion prior to treatment. We therefore aimed to determine to which degree in vitro aging and chronological aging may be similar processes or if in vitro culture-related changes at the cellular and molecular level are at least altered as a function of donor age. For that purpose we established MSCs cultures from young (yMSCs) and aged (aMSCs) rats that were cultured for more than 100 passages. These long-term MSCs cultures were non-tumorigenic and exhibited similar surface marker patterns as primary MSCs of passage 2. During in vitro expansion, but not during chronological aging, MSCs progressively lose their progenitor characteristics, e.g., complete loss of osteogenic differentiation potential, diminished adipogenic differentiation, altered cell morphology and increased susceptibility towards senescence. Transcriptome analysis revealed that long-term in vitro MSCs cultivation leads to down-regulation of genes involved in cell differentiation, focal adhesion organization, cytoskeleton turnover and mitochondria function. Accordingly, functional analysis demonstrated altered mitochondrial morphology, decreased antioxidant capacities and elevated ROS levels in long-term cultivated yMSCs as well as aMSCs. Notably, only the MSC migration potential and their antioxidative capacity were altered by in vitro as well as chronological aging. Based on specific differences observed between the impact of chronological and in vitro MSC aging we conclude that both are distinct processes.

[C-reactive protein. An independent risk factor for the development of infection after primary arthroplasty].

BACKGROUND Infection is a severe complication after primary arthroplasty of the hip (THA) or knee joint (TKA). Based on its high sensitivity, the C-reactive protein (CRP) concentration has become a valuable tool in the diagnosis of infection, although it has only moderate specificity. Because of this, it remains unclear whether a preoperative increased CRP without clinical symptoms is a risk factor for infection after primary arthroplasty. MATERIAL AND METHODS In a retrospective analysis, we investigated individuals with infection after primary THA or TKA and matched them with patients without infection after similar operations. Matching criteria were age, gender, and present diseases. The average age of the 50 included individuals was 67.4 (range 48-81) years, with eight men and 17 women in each group. In addition to preoperative CRP, specific patient and surgery data and microbiological and histopathologic findings were obtained. RESULTS The average preoperative CRP concentration in the infected patient group was 1.3+/-2.5 mg/dl, in contrast to 0.4+/-0.7 mg/dl in the noninfected group. A threshold of 0.5 mg/dl was appropriate for discriminating between the two groups [13/25 (52%) in the infection group vs. 3/25 (12%) in the control group, p=0.003]. Independent from the patient group, CRP concentrations were significantly increased in individuals with diabetes mellitus (1.2+/-1.5 vs. 0.7+/-2.0 mg/dl, p=0.03). CONCLUSION An increased preoperative CRP concentration without clinical findings of infection is a risk factor for prosthetic infection after primary THA or TKA with a threshold concentration of 0.5 mg/dl. Latent local or systemic infections or aseptic inflammation with subsequent local immune suppression seem to be responsible. We recommend evaluating CRP before every THA and TKA. For values beyond 0.5 mg/dl, an exploration for infection should be done. Otherwise, the patient should be informed about the increased risk of infection.

Das C-reaktive Protein

BACKGROUND Infection is a severe complication after primary arthroplasty of the hip (THA) or knee joint (TKA). Based on its high sensitivity, the C-reactive protein (CRP) concentration has become a valuable tool in the diagnosis of infection, although it has only moderate specificity. Because of this, it remains unclear whether a preoperative increased CRP without clinical symptoms is a risk factor for infection after primary arthroplasty. MATERIAL AND METHODS In a retrospective analysis, we investigated individuals with infection after primary THA or TKA and matched them with patients without infection after similar operations. Matching criteria were age, gender, and present diseases. The average age of the 50 included individuals was 67.4 (range 48-81) years, with eight men and 17 women in each group. In addition to preoperative CRP, specific patient and surgery data and microbiological and histopathologic findings were obtained. RESULTS The average preoperative CRP concentration in the infected patient group was 1.3+/-2.5 mg/dl, in contrast to 0.4+/-0.7 mg/dl in the noninfected group. A threshold of 0.5 mg/dl was appropriate for discriminating between the two groups [13/25 (52%) in the infection group vs. 3/25 (12%) in the control group, p=0.003]. Independent from the patient group, CRP concentrations were significantly increased in individuals with diabetes mellitus (1.2+/-1.5 vs. 0.7+/-2.0 mg/dl, p=0.03). CONCLUSION An increased preoperative CRP concentration without clinical findings of infection is a risk factor for prosthetic infection after primary THA or TKA with a threshold concentration of 0.5 mg/dl. Latent local or systemic infections or aseptic inflammation with subsequent local immune suppression seem to be responsible. We recommend evaluating CRP before every THA and TKA. For values beyond 0.5 mg/dl, an exploration for infection should be done. Otherwise, the patient should be informed about the increased risk of infection.

Preferred Use of Polyhexanide in Orthopedic Surgery

In orthopedic and trauma surgery, the most frequently used antiseptic is polyhexanide. Its favored application is based on prepossessing tissue compatibility in contrast to various antiseptics and a high antimicrobiological effect. Recent studies showed toxic effects of this antiseptic on human chondrocytes. The aim of this study was to further analyze the toxic and apoptotic effects of polyhexanide on primary human chondrocytes. The hypothesis of this study was that polyhexanide induces apoptosis on human chondrocytes. Primary human chondrocytes were isolated and cultured from human donors with osteoarthritis of the knee who underwent total arthroplasty and had no indication of infection. Polyhexanide at a standard concentration of 0.04% was added to the monolayer cultures. Early and late apoptotic cells were analyzed by flow cytometric detection of annexin V, active caspases, and 7AAD, and by fluorescence microscopy using annexin V and propidium iodide staining. Flow cytometric analysis demonstrated an increase of annexin V and active caspases expression of human chondrocytes after incubation with polyhexanide. Fluorescence microscopy demonstrated a high number of annexin V positive and propidium iodide negative early apoptotic cells. The data show that polyhexanide promotes apoptosis on primary human chondrocytes in vitro, which may indicate the use of polyhexanide in septic joint surgery.

[Patella height after total knee replacement: influence of the radiological setting].

BACKGROUND Acquired patella baja is a possible cause of painful total knee arthroplasty (TKA) and a poor functional outcome. Standardized lateral radiographs - often missing in the daily routine - are required for evaluating the patella height. It is unknown which patella index is insensitive to the radiological setting so that it can be used efficiently in the clinical routine. PATIENTS AND METHODS This prospective study included 25 patients after TKA. Their average age was 69.5+/-8.8 (51-80) years. In two cases (8%), resurfacing of the patella was performed. The modified Insall-Salvati index (mIS) and the Caton-Deschamps index (CD) were determined and compared on lateral radiographs with the patients knee extended while lying down, extended while standing, and 30 degrees flexed while lying down. RESULTS The average mIS in extension was 1.63+/-0.31 with the patient lying and 1.68+/-0.31 with the patient standing. In 30 degrees flexion and lying, it was 1.7+/-0.3. The mIS on the recommended radiographs (30 degrees flexion) correlated well with the mIS in extension while lying (R=0.48, p<0.001) and standing (R=0.99, p<0.001). The CD in extension was 0.78+/-0.21 while lying and 0.49+/-0.12 while standing; it was 0.48+/-0.15 in 30 degrees flexion. The CD on the recommended radiographs (30 degrees flexion) correlated satisfactorily with the CD in extension while standing (R=0.93, p<0.001) but not in extension while lying (not significant). CONCLUSION The mIS is less dependent on the radiological setting than the CD is. The mIS can be used efficiently for evaluating an acquired patella baja in radiographs performed in different, not standardized, conditions.

Temporary arthrodesis using fixator rods in two-stage revision of septic knee prothesis with severe bone and tissue defects

PurposeThe present study describes a new temporary arthrodesis procedure, which aims for septic knee prosthesis replacement, in particular for larger bone and soft tissue defects. Our technique offers high stability and full weight-bearing capacity of the knee joint.MethodsThe study included 16 patients with major bone defects (AORI type IIb or greater) after receiving a radical debridement and a septic two-stage revision total knee arthroplasty. After removing the infected prosthesis and debridement, two AO fixator rods were positioned into the intramedullary space of the femur and tibia. Subsequently, both rods were joined tube-to-tube and adjusted in the center of the knee joint. Finally, the whole cavity of the knee joint was filled with PMMA. The number of previous surgeries, bacterial spectrum, risk factors for further infection and reinfection rates was recorded. Immediately after the temporary arthrodesis, radiographs of the knee with the enclosed spacers were taken in order to compare to previous radiographs and avoiding to miss possible spacer loosening.ResultsNine of sixteen patients underwent more than two revision surgeries before receiving our new arthrodesis technique. No cases of spacer loosening were observed in all 16 patients; further, there were no peri-implant fractures, and four persistent infections were noted.ConclusionsTemporary arthrodesis using AO fixator rods offers a high stability without loosening. Its potential to replace conventional augmentation techniques should be taken into account, particularly in the case of larger bone and tissue defects. In clinical practice, the cemented spacer using AO fixator rods could be an alternative technique for temporary knee arthrodesis after septic debridement.Level of evidenceRetrospective case series, Level IV.

Intraoperative Navigation of Patient-Specific Instrumentation Does Not Predict Final Implant Position

UNLABELLED The purpose of this study was to determine if intraoperative navigation predicted final implant position of total knee arthroplasties (TKAs) performed with patient-specific instrumentation (PSI). We retrospectively reviewed 60 TKAs performed with PSI and imageless navigation. These values were compared to postoperative coronal alignment based on long-leg radiographs, as well as rotation and tibial slope based on CT scans. The intraoperative coronal position of the tibia as measured by the intraoperative navigation indicated a significantly higher deviation from the neutral mechanical axis than the actual final position (P=0.03). Similarly, tibial slope and femoral component rotation measured by intraoperative navigation significantly deviated from the final slope and femoral component rotation (P<0.0001). In conclusion, intraoperative navigation of PSI position showed a significantly high deviation from the true final implant position. LEVEL OF EVIDENCE Level III, therapeutic. See Instructions to Authors for a complete description of levels of evidence.

Femur positioning in navigated total knee arthroplasty.

Navigated total knee arthroplasty (TKA) results in better restoration of neutral mechanical axis than does the conventional technique. Nevertheless, coronal malalignment has not been eliminated. It is yet unknown whether errors in implant positioning occur more on the femoral side, more on the tibial side, or equally on both sides. The hypothesis of this study was that a predominance of coronal component malalignment exists on the tibial side in navigated tibia-first TKA.Fifty-seven consecutive navigated (OrthoPilot; B. Braun Aesculap, Tuttlingen, Germany) TKAs were included in this retrospective study. Pre- and postoperative digital whole-leg standing radiographs were analyzed. Coronal alignment was measured for the whole leg pre- and postoperatively. Lateral distal femur angle and medial proximal tibia angle were analyzed on the preoperative radiographs. On the postoperative radiographs, coronal alignment of the femoral and tibial components were measured separately in reference to the tibial and femoral mechanical axis. The coronal alignment improved from 8.2° ± 3.7° preoperatively to 1.1° ± 1.2° postoperatively, with 5 (8%) outliers outside the 3° window. The femoral component was malaligned (0.6° ± 0.6°), whereas the tibial component showed a significantly higher deviation from the mechanical axis of 1.0° ± 1.1° (P=.009). The femoral component was positioned more precisely than the tibial component. The latter influences gap management in the tibia-first technique and may thereby have a relevant effect on joint stability. Accuracy of the surgical technique and differences in the mathematical algorithm for the determination of landmarks are possible reasons for the difference in precision between the femoral and tibial component positioning.

Patellahöhenstand nach Kniegelenkendoprothesenimplantation

BACKGROUND Acquired patella baja is a possible cause of painful total knee arthroplasty (TKA) and a poor functional outcome. Standardized lateral radiographs - often missing in the daily routine - are required for evaluating the patella height. It is unknown which patella index is insensitive to the radiological setting so that it can be used efficiently in the clinical routine. PATIENTS AND METHODS This prospective study included 25 patients after TKA. Their average age was 69.5+/-8.8 (51-80) years. In two cases (8%), resurfacing of the patella was performed. The modified Insall-Salvati index (mIS) and the Caton-Deschamps index (CD) were determined and compared on lateral radiographs with the patients knee extended while lying down, extended while standing, and 30 degrees flexed while lying down. RESULTS The average mIS in extension was 1.63+/-0.31 with the patient lying and 1.68+/-0.31 with the patient standing. In 30 degrees flexion and lying, it was 1.7+/-0.3. The mIS on the recommended radiographs (30 degrees flexion) correlated well with the mIS in extension while lying (R=0.48, p<0.001) and standing (R=0.99, p<0.001). The CD in extension was 0.78+/-0.21 while lying and 0.49+/-0.12 while standing; it was 0.48+/-0.15 in 30 degrees flexion. The CD on the recommended radiographs (30 degrees flexion) correlated satisfactorily with the CD in extension while standing (R=0.93, p<0.001) but not in extension while lying (not significant). CONCLUSION The mIS is less dependent on the radiological setting than the CD is. The mIS can be used efficiently for evaluating an acquired patella baja in radiographs performed in different, not standardized, conditions.

BMP-2 Dependent Increase of Soft Tissue Density in Arthrofibrotic TKA.

Arthrofibrosis after total knee arthroplasty (TKA) is difficult to treat, as its aetiology remains unclear. In a previous study, we established a connection between the BMP-2 concentration in the synovial fluid and arthrofibrosis after TKA. The hypothesis of the present study was, therefore, that the limited range of motion in arthrofibrosis is caused by BMP-2 induced heterotopic ossifications, the quantity of which is dependent on the BMP-2 concentration in the synovial fluid. Eight patients with arthrofibrosis after TKA were included. The concentration of BMP-2 in the synovial fluid from each patient was determined by ELISA. Radiologically, digital radiographs were evaluated and the grey scale values were determined as a measure of the tissue density of defined areas. Apart from air, cutis, subcutis and muscle, the soft-tissue density in the area of the capsule of the suprapatellar pouch was determined. The connection between the BMP-2 concentration and the soft-tissue density was then investigated. The average BMP-2 concentration in the synovial fluid was 24.3 ± 6.9 pg/ml. The density of the anterior knee capsule was on average 136 ± 35 grey scale values. A linear correlation was shown between the BMP-2 concentration in the synovial fluid and the radiological density of the anterior joint capsule (R=0.84, p = 0.009). We were able to show that there is a connection between BMP-2 concentration and soft-tissue density in arthrofibrosis after TKA. This opens up the possibility of conducting a prophylaxis against arthrofibrosis in risk patients by influencing the BMP-2 pathway.