Reaction time and brake pedal force after total knee replacement: timeframe for return to car driving.

PURPOSE: This prospective cohort study aimed to examine objective and subjective parameters in patients who underwent total knee replacement (TKR) to assess from when on driving a car can be deemed safe again. METHODS: Thirty patients (16 women, 14 men, age 66 ± 11 years) who received TKR of the right knee and 45 healthy controls (26 women, 19 men, age 32 ± 9 years) were asked to perform an emergency braking manoeuvre using a driving simulator. Brake pedal force (BPF), neuronal reaction time (NRT), brake reaction time (BRT), and subjective parameters (pain, subjective driving ability) were measured preoperatively as well as 5 days, 3-4, and 6 weeks after TKR. RESULTS: Preoperative NRT was 506 ± 162 ms, BRT 985 ± 356 ms, and BPF 614 ± 292 N. NRT increased to 561 ± 218 ms, BRT to 1091 ± 404 ms and BPF decreased to 411 ± 191 N 5 days after TKR. Three weeks after surgery, NRT was 581 ± 164 ms and BRT 1013 ± 260 ms, while BPF increased to 555 ± 200 N. Only BPF showed significant differences (p < 0.01). In week 6, all parameters were restored to baseline levels; patients showed significant pain decrease and evaluated their driving ability as "good" again. CONCLUSION: BPF was the only parameter displaying a significant postoperative decrease. However, preoperative patients' baseline levels and subjective confidence in driving ability were only reached 6 weeks after the operation. These results indicate that a minimum waiting period of 6 weeks should be considered before patients can safely participate in road traffic at their individual preoperative safety level again. LEVEL OF EVIDENCE: II.

Contamination of Irrigation Fluid During Primary Total Knee Arthroplasty.

PURPOSE: During surgical procedures, some amount of irrigation fluid leaks from the surgical site and accumulates on the sterile drapes. Whether these fluid collections show bacterial contamination over time in primary total knee arthroplasty remains unclear. METHODS: In this study, we included 100 patients. We collected the samples of irrigation fluid before skin incision and every 30 minutes after the start of surgery. In addition, at the end of surgery, we evaluated the suction tip for bacterial contamination. After 3 months, we clinically evaluated all patients for periprosthetic joint infection. RESULTS: Although the drapes were found to be sterile after 30 minutes, fluid residues on the surgical drapes show a contamination rate of 22% after 60 minutes and thus a marked correlation between advanced duration of surgery and bacterial contamination. The suction tip was contaminated with bacteria in 22% of cases. The spectrum of pathogens typical of periprosthetic joint infection could be demonstrated. CONCLUSION: Fluid surgical drape reservoirs were abacterial during the first 30 minutes but showed marked bacterial contamination over time. For total knee arthroplasty, we recommend regular replacement of the suction tip every 30 minutes. In addition, irrigation fluid reservoirs should not be withdrawn by suction 30 minutes after skin incision.

Improved early outcome after TKA through an app-based active muscle training programme-a randomized-controlled trial.

PURPOSE: The purpose of this prospective randomized-controlled trial (RCT) was to evaluate if an app-based feedback-controlled active muscle training programme can be used to improve the outcome in the immediate postoperative period after total knee arthroplasty (TKA). METHODS: Sixty patients, with a median age of 65.9 years (range 45-84), awaiting primary TKA were randomized into a control and training group. Both groups followed an identical postoperative protocol. In addition, the training group postoperatively performed an app-based feedback-controlled active muscle training programme multiple times daily. Outcome measures were active and passive range of motion (ROM), pain at rest and in motion, knee extension strength, the timed "Up and Go", 10-m Walk Test, 30-s Chair Stand Test, Knee Injury and Osteoarthritis Outcome Score (KOOS), Knee Society Score (KSS), and clinical data. RESULTS: The training group performed an average of 18.4 training sessions, which led to significantly higher ROM, less pain at rest and in motion, higher strength, and significantly higher functional scores. More training correlated with a better outcome. CONCLUSIONS: The use of an app-based feedback-controlled active muscle training programme can improve the clinical outcome after TKA, especially ROM and reduce pain. Clinically relevant is that the training programme could be considered an alternative to continuous passive motion after total knee arthroplasty. LEVEL OF EVIDENCE: II.

Modifications of femoral component design in multi-radius total knee arthroplasty lead to higher lateral posterior femoro-tibial translation.

PURPOSE: As the aims of changes in total knee arthroplasty (TKA) designs are to reinstate more natural kinematics, the current study evaluated the in vivo kinematics in patients who underwent a cruciate retaining gradually changing femoral radius ("G-CURVE") against a cruciate retaining conventional changing femoral radius ("J-CURVE") geometry TKA design. The hypothesis of the study is that the G-CURVE design would allow a substantial increase in the femoral rollback compared to the J-CURVE design. METHODS: Retrospective study design. Thirty patients were included (G-CURVE, n = 20; J-CURVE, n = 10). Single-plane fluoroscopic analysis and marker-based motion capture gait analysis was performed to analyse dynamic tibiofemoral motion during weight-bearing and unloaded activities at 24 month after index surgery. RESULTS: The analysis of the medial and lateral points on the tibia plateau during the unloaded flexion-extension and the weight-bearing lunge activities revealed a significant difference in femoral rollback in G-CURVE TKA above 60° (p = 0.001) and 30° (p = 0.02) of knee flexion, respectively. Moreover, the lateral condyle of the G-CURVE showed a higher extent of femoral rollback while the lateral condyle of the J-CURVE rolled forward. CONCLUSION: At 2 years post-operative, the G-CURVE TKA showed significant differences in femoro-tibial translation in comparison with the J-CURVE system, in vivo. The G-CURVE resulted in an increased lateral rollback and simultaneously in an elimination of the paradoxical medial roll-forward present in the J-CURVE design. Moreover, knee kinematics analysis showed significant differences between unloaded and weight-bearing conditions revealing the impact of load and muscle force. The analysis conducted in this study contributes to further understand the principal movement characteristics in widely used older designs in comparison with recently developed concepts to get a better overview on their potential benefits on in vivo kinematics. LEVEL OF EVIDENCE: III.

No improvement in reducing outliers in coronal axis alignment with patient-specific instrumentation.

PURPOSE AND HYPOTHESIS: Patient-specific instrumentation (PSI) uses 3D preoperative imaging to produce individualized cutting blocks specific to patients' anatomy and according to the preoperative plan with the aim to reduce the number of mechanical leg alignment (MLA) outliers, to improve implant positioning and to decrease surgery time. The primary purpose of this study was to investigate the efficacy of a specific PSI in comparison with standard instrumentation (SI) in reducing the number of MLA outliers. It was hypothesized that the number of MLA outliers would be significantly lower in the PSI group. METHODS: A multicenter randomized controlled trial was implemented. There were 59 patients in the PSI group and 66 in the SI group. The absolute number of outliers outside the ± 3° target neutral MLA was compared between the groups with a Chi-square test. As secondary outcomes, the Knee Society Score (KSS) and the Knee Injury and Osteoarthritis Outcome Score (KOOS) were compared between the groups preoperatively and at 90-day follow-up. RESULTS: There were 15 (26.3%) MLA outliers in the PSI group and 8 (12.3%) in the SI group. The number of outliers was not independent from the group ( X2 (1) = 3.8, p = 0.04; Relative risk = 1.5). Preoperatively, there were no significant differences between the groups when comparing their KSS and KOOS sub-scores. At 90 days postoperatively, the patients in the SI group showed better KOOS-Quality of Life (KOSS-QOL) in comparison with the PSI group (p < 0.0001). CONCLUSION: The use of PSI did not significantly reduce the number of MLA outliers in comparison with SI. There were no differences when comparing the achieved mean MLA of both groups. LEVEL OF EVIDENCE: Level I, prospective randomized controlled trial.

[Unicompartmental vs. Total Knee Arthroplasty for Medial Osteoarthritis]. / AE-Beitrag: Unikondylärer Ersatz vs. Totalendoprothese bei medialer Gonarthrose.

Background In end-stage medial osteoarthritis, the surgeon can decide whether to use unicompartmental or total knee arthroplasty for operative treatment of the patient. Despite the available literature there is a lack of evidence to suggest if one procedure can be rated as being superior to the other. With increasing demand for knee arthroplasty, treatment with the highest expectation of success will be of particular interest. The purpose of this manuscript was to analyse and compare the available literature on unicompartmental vs. total knee arthroplasty for the treatment of medial osteoarthritis. Material and Methods In this review of literature, the two procedures were compared regarding their clinical outcome, implant survival, and complication rates. Results Regarding the clinical outcome the unicompartmental knee arthroplasty was shown to be superior over total knee arthroplasty. However, studies were mostly retrospective and groups were also different preoperatively. Patients treated with unicompartmental knee arthroplasty had better preoperative range of motion and function scores. Unicompartmental and total knee arthroplasty showed comparably increased functional scores. Taking the implant survival as parameter, institutional registries, multicenter studies and arthroplasty registries found total knee arthroplasties to have a significantly better long-term survival in comparison to unicompartmental knee arthroplasty. However, data might be biased by the lower threshold to revise unicompartmental knee arthroplasty due to expected simple revision and more subjective indications for revision. Looking at the complication rate, one has to differentiate between general and implant-specific complications. While the unicompartmental knee arthroplasty was shown to be advantageous in terms of general complications and mortality, it was also shown to be inferior in terms of implant-specific complications. Conclusion The available literature does not show one procedure to be superior to the other. The trend to a better clinical outcome and a lower mortality rate is advantageous for unicompartmental knee arthroplasty, while the better long-term survival and a lower risk of implant-specific complications may make total knee arthroplasty preferable.

Inadequacy of Joint Aspiration for Detection of Persistent Periprosthetic Infection During Two-Stage Septic Revision Knee Surgery.

Despite the lack of validation, synovial aspiration remains a common practice during 2-stage septic revision total knee arthroplasty (TKA). The goal of this study was to investigate the diagnostic validity of synovial polymethylmethacrylate (PMMA) spacer aspiration of temporary knee arthrodesis to detect persistent periprosthetic joint infection before TKA reimplantation. This retrospective cohort study included 73 consecutive patients who underwent 2-stage septic revision TKA according to a standard protocol. After explantation surgery, including temporary arthrodesis with an intramedullary stabilized PMMA spacer, all patients had synovial aspiration 2 weeks before reimplantation to exclude persistent periprosthetic joint infection. Patients had a 2-week antibiotic holiday before aspiration. Sensitivity and specificity of the synovial PMMA spacer joint aspiration for the detection of periprosthetic joint infection were determined and referenced against intraoperative microbiologic and histologic samples obtained at second-stage surgery. Sensitivity of the synovial PMMA spacer aspiration was 21%. Because of poor diagnostic validity, synovial PMMA spacer aspiration cannot be recommended for routine exclusion of persistent periprosthetic joint infection before TKA reimplantation. Therefore, exclusion of persistent periprosthetic joint infection should be supplemented by other diagnostic methods, and it is not necessary to delay TKA reimplantation for PMMA spacer aspiration. [Orthopedics. 2017; 40(4):231-234.].

Preliminary results of a new surgical technique in total knee arthroplasty (TKA) using the native ligament tension for femoral implant positioning in varus osteoarthritis.

PURPOSE: Individual implant alignment in total knee arthroplasty (TKA) has seen growing interest over the past years. This study therefore aimed to develop a surgical technique for implant alignment based on native ligament tension, and to present the results obtained using this technique. METHODS: 25 patients were included in this prospective study. Patient-specific instrumentation (PSI) was used for the resection of the extension gap. Ligament tension was measured after the removal of all accessible osteophytes. In the event of asymmetry, the distal femur resection was adjusted up to 2.5° using an adjustable cutting block. The aim was to achieve a symmetrical extension gap without release, not a neutral leg axis. Femoral rotation was aligned on the basis of ligament tension. Patients were followed up to 3 months postoperatively. RESULTS: The postoperative whole-leg axis was 2.8° ± 1.6° varus. Patients achieved a flexion of 118° ± 9°, a Knee Score of 91.5 ± 3.2 and a Function Score of 86.8 ± 8.3 points. CONCLUSION: For the first time, the new surgical technique described here permits a ligament tension based femoral implant alignment together with PSI. It was shown to be safe, with encouraging clinical and radiological results. LEVEL OF EVIDENCE: Therapeutic study level IV.

Fixation of stem in revision of total knee arthroplasty: cemented versus cementless-a meta-analysis.

PURPOSE: Revision of total knee arthroplasty (TKA) is growing rapidly all over the world. The introduction of intramedullary stems for additional stability in revision is well accepted by most of the surgeons, while the philosophy of stem fixation is still under controversy. A meta-analysis was performed to compare the survivorship of revised implants with regard to a cemented or cementless stem fixation. METHODS: Publications with patients who underwent revision TKA with minimum 24-month follow-up were systematically reviewed. Type of intramedullary stem fixation, failure rate for any reason, incidence of aseptic loosening and infection were extracted with follow-up interval specified. Random-effects meta-analysis was used to aggregate incidence data, which was compared between different fixation groups by fitting of logistic regression model. RESULTS: Seventeen observational studies were included in this meta-analysis. There was a similar likelihood of failure for any reason (risk ratio, RR 0.97), general reoperation (RR 1.02), aseptic loosening (RR 1.0) and infection (RR 1.0) in cemented stem fixation group compared to cementless stem fixation group with follow-up <60 months. When follow-up period extend to more than 60 months, the same likelihood was observed as 0.98, 0.96, 0.97 and 0.98, respectively. There was no significant difference in any of these comparisons of survival-related indices. CONCLUSION: There was no significant difference in failure for any reason, reoperation, aseptic loosening and infection between revision TKA with cemented or cementless stem fixation. Based on the available literature, no superiority of any type of stem fixation was found. If follow-up period was neglected, aseptic loosening would be the leading reason for pain and dysfunction of patient undertaken revision TKA. LEVEL OF EVIDENCE: Systematic review of Level IV, Therapeutic studies, Level IV.

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

PURPOSE: The 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. METHODS: The 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. RESULTS: Nine 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. CONCLUSIONS: Temporary 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 EVIDENCE: Retrospective case series, Level IV.

Influence of the tourniquet on tibial cement mantle thickness in primary total knee arthroplasty.

PURPOSE: The purpose of the study was whether the use of a tourniquet increases cement mantle thickness in primary total knee arthroplasty and influences the calculated blood loss and postoperative pain. METHODS: Ninety patients with a primary total knee arthroplasty (TKA) were enroled in this prospective randomised trial and divided into a group with (n = 45) and without tourniquet (n = 45). The radiological tibial cement mantle thickness was evaluated postoperatively in four zones on anteroposterior and two zones on lateral radiographs, and values were cumulated. Additionally, the calculated blood loss and postoperative pain levels were recorded. RESULTS: There was a median cumulative cement mantle thickness of 13 mm (range 8-19 mm) without tourniquet and of 14.2 mm (range 9-18 mm) with tourniquet (p = 0.009). The median calculated blood loss was 0.6 L (range 0.2-2.0 L) without and 0.9 L (range 0.3-1.5 L) (p = 0.02) with tourniquet. Patient-reported postoperative pain levels were significantly higher in the tourniquet group during mobilisation (p = 0.01) and at rest (p = 0.001). CONCLUSIONS: The use of a tourniquet in primary TKA increased the tibial cement mantle thickness but also increased the postoperative calculated blood loss and postoperative pain. Surgeons might take this into consideration for decision-making whether to use a tourniquet during TKA. LEVEL OF EVIDENCE: II.

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.

Small improvements in mechanical axis alignment achieved with MRI versus CT-based patient-specific instruments in TKA: a randomized clinical trial.

BACKGROUND: Patient-specific instrumentation in TKA has the proposed benefits of improving coronal and sagittal alignment and rotation of the components. In contrast, the literature is inconsistent if the use of patient-specific instrumentation improves alignment in comparison to conventional instrumentation. Depending on the manufacturer, patient-specific instrumentation is based on either MRI or CT scans. However, it is unknown whether one patient-specific instrumentation approach is more accurate than the other and if there is a potential benefit in terms of reduction of duration of surgery. QUESTIONS/PURPOSES: We compared the accuracy of MRI- and CT-based patient-specific instrumentation with conventional instrumentation and with each other in TKAs. The three approaches also were compared with respect to validated outcomes scores and duration of surgery. METHODS: A randomized clinical trial was conducted in which 90 patients were enrolled and divided into three groups: CT-based, MRI-based patient-specific instrumentation, and conventional instrumentation. The groups were not different regarding age, male/female sex distribution, and BMI. In all groups, coronal and sagittal alignments were measured on postoperative standing long-leg and lateral radiographs. Component rotation was measured on CT scans. Clinical outcomes (Knee Society and WOMAC scores) were evaluated preoperatively and at a mean of 3 months postoperatively and the duration of surgery was analyzed for each patient. MRI- and CT-based patient-specific instrumentation groups were first compared with conventional instrumentation, the patient-specific instrumentation groups were compared with each other, and all three approaches were compared for clinical outcome measures and duration of surgery. RESULTS: Compared with conventional instrumentation MRI- and CT-based patient-specific instrumentation showed higher accuracy regarding the coronal limb axis (MRI versus conventional, 1.0° [range, 0°-4°] versus 4.5° [range, 0°-8°], p < 0.001; CT versus conventional, 3.0° [range, 0°-5°] versus 4.5° [range, 0°-8°], p = 0.02), femoral rotation (MRI versus conventional, 1.0° [range, 0°-2°] versus 4.0° [range, 1°-7°], p < 0.001; CT versus conventional, 1.0° [range, 0°-2°] versus 4.0° [range, 1°-7°], p < 0.001), and tibial slope (MRI versus conventional, 1.0° [range, 0°-2°] versus 3.5° [range, 1°-7°], p < 0.001; CT versus conventional, 1.0° [range, 0°-2°] versus 3.5° [range, 1°-7°], p < 0.001), but the differences were small. Furthermore, MRI-based patient-specific instrumentation showed a smaller deviation in the postoperative coronal mechanical limb axis compared with CT-based patient-specific instrumentation (MRI versus CT, 1.0° [range, 0°-4°] versus 3.0° [range, 0°-5°], p = 0.03), while there was no difference in femoral rotation or tibial slope. Although there was a significant reduction of the duration of surgery in both patient-specific instrumentation groups in comparison to conventional instrumentation (MRI versus conventional, 58 minutes [range, 53-67 minutes] versus 76 minutes [range, 57-83 minutes], p < 0.001; CT versus conventional, 63 minutes [range, 59-69 minutes] versus 76 minutes [range, 57-83 minutes], p < .001), there were no differences in the postoperative Knee Society pain and function and WOMAC scores among the groups. CONCLUSIONS: Although this study supports that patient-specific instrumentation increased accuracy compared with conventional instrumentation and that MRI-based patient-specific instrumentation is more accurate compared with CT-based patient-specific instrumentation regarding coronal mechanical limb axis, differences are only subtle and of questionable clinical relevance. Because there are no differences in the long-term clinical outcome or survivorship yet available, the widespread use of this technique cannot be recommended.

Intramedullary control of distal femoral resection results in precise coronal alignment in TKA.

INTRODUCTION: There is still a relevant rate of outliers in coronal alignment >3° when the conventional technique is used, potentially accompanied by a poorer long-term clinical outcome and a reduced longevity of the implant. Intraoperative implementation of preoperative planning and above all checking of the bone resections carried out are decisive for reinstating a straight leg axis. Intramedullary control of femoral resection has not been described to date. The objective of this study was to present a new technique for the intramedullary control of femoral resection and the results obtained using this method. METHODS: All patients who underwent primary total knee arthroplasty with the new intramedullary control of femoral resection were included in this retrospective study. The frequency of the need for correction of the saw cuts was documented. The radiological assessment included pre- and postoperative whole-leg standing radiographs. In the process, the whole-leg axis, AMA, entry point, LDFA and MPTA were evaluated preoperatively. On the postoperative radiographs, the whole-leg axis and the alignment of the femoral and tibial components were evaluated. RESULTS: One hundred and sixty-two total knee arthroplasties (TKAs) were included in the study. The average age was 68.7 years. The preoperative malalignment was on the average 8.2° ± 4.7° (23.8° varus to 17.3° valgus). The postoperative whole-leg axis was on the average 1.3° ± 1.1° (5.5° varus to 4.3° valgus). The femoral component showed a deviation from the mechanical axis of 0.1° ± 1.2° (4.3° varus to 3.7° valgus) and the tibial component a deviation from the mechanical tibial axis of 0.3° ± 1.2° (4.2° varus to 2.5° valgus). CONCLUSIONS: The new technique of intramedullary control of distal femoral resection, together with preoperative planning, leads to a precise alignment of the femoral component in the coronal plane. Thus, for the first time, a simple and effective tool for checking distal femoral resection is available for standardized use.

Limited use of antiseptics in septic surgery.

In septic joint surgery, treatment with antiseptics is a standard procedure. Postinfectious degeneration of cartilage often results in early arthritis that necessitates joint replacement, even in young patients. It is still unclear whether antiseptics have only a toxic effect on chondrocytes or also induce late cell death through apoptosis. We hypothesized that commonly used antiseptics (polyhexanide, hydrogen peroxide, and chlorhexidine) induce different stages of apoptosis on human chondrocytes. Human chondrocytes were isolated and cultured. Polyhexanide, hydrogen peroxide, and chlorhexidine were added to the monolayer cultures. Early and late apoptotic cells were analyzed using flow cytometric detection of Annexin V, active caspases, and 7AAD, and fluorescence microscopy using Annexin V and propidium iodide staining. Flow cytometric analysis revealed an increase of Annexin V and active caspases expression of human chondrocytes after incubation with polyhexanide, hydrogen peroxide, and chlorhexidine. Fluorescence microscopy demonstrated a high number of apoptotic cells. Our data show that polyhexanide and chlorhexidine only promote the early stages of apoptosis without any differences in toxicity. Conversely, hydrogen peroxide induces early and later stages of apoptosis on primary human chondrocytes in vitro.

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.

In situ tele-thermographic measurements during PMMA spacer augmentation in temporary arthrodesis after periprosthetic knee joint infection.

Poly-Methylmethacrylate (PMMA) is widely-used in orthopaedic surgery in revision arthroplasty or as a spacer in temporary arthrodesis of periprostehtic knee joint infection during a two stage procedure. The intra-operative temperature behaviour, however, has not yet been quantified. It is known that high temperature induce thermally necrosis of surrounding bone tissue during polymerisation process. The aim was to evaluate the PMMA surface temperature during polymerisation phase in situ. We hypothesized, that temperature measured in vivo could become critical in terms of the induction of thermal bone necrosis during the polymerisation phase of PMMA. The PMMA surface was measured tele-thermographically in situ during knee arthroplasty revision surgery. Infrared pictures were analyzed for temperature peaks and changes. Measurements yielded maximum PMMA-surface-temperatures ranging from 101 to 110 degrees and a two-minute-plateau of > 100°. Hot PMMA during the polymerisation phase could potentially induce tissue (bone) necrosis. Therefore temperature of PMMA of more than 70 degrees should be avoided. Cooling of the PMMA is highly recommendable.

Increased BMP expression in arthrofibrosis after TKA.

PURPOSE: Because of the multiple possible aetiologies of painful total knee arthroplasty (TKA), the diagnosis and treatment of such patients are challenging. In a considerable number of patients, an intraarticular pathology is present, although not verifiable with clinical and diagnostic imaging techniques as in cases of primary arthrofibrosis. In these patients, the differentiation between intra- and extraarticular causes of pain remains difficult. Until now, little attention has been paid to changes of the synovial fluid and tissue in these knees. The objective of this study was to analyse the changes of the synovial environment in patients suffering from arthrofibrosis after TKA in comparison with knees with referred pain suffering from hip arthritis. The changes of the synovial environment probably provide additional diagnostic information to verify an intraarticular pathology. METHODS: The synovial fluid of 10 consecutive knees in 10 patients presenting with a primary arthrofibrosis after TKA without signs of infection, instability, malalignment, or loosening was analysed and compared to the synovial fluid of 10 knees with referred pain serving as controls. The BMP-2 concentration was measured in the synovial fluid, and the presence of cytokines leading to an overexpression of BMP-2 was detected by measuring the change of BMP-2 expression in a synoviocyte cell line following exposing to the synovial fluid of the patients. RESULTS: The concentration of BMP-2 in the synovial fluid was significantly higher in arthrofibrotic TKA knees (24.3 ± 6.9 pg/mL), compared with the control group 5.9 ± 4.8 pg/mL (P < 0.001). Corresponding to this finding, BMP-2 expression in synoviocytes was upregulated 11.5-fold (P < 0.05) by synovial fluid of patients suffering from arthrofibrosis after TKA, compared with the control group with referred pain. CONCLUSION: BMP-2 is overexpressed and its concentrations are consequently higher in patients suffering from arthrofibrosis after TKA. The synovial BMP-2 concentration may be a potential marker for differentiating between intra- and extraarticular causes of pain. LEVEL OF EVIDENCE: II.

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.

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.