Excellent mid- to long-term survival of tantalum metal cones in a case series of revision knee arthroplasty with severe bony defects.

PURPOSE: Severe metaphyseal bone defects remain a challenge and represent a growing problem in revision total knee arthroplasty (RTKA). The purpose of this study was to examine the survival of first-generation tantalum metal cones (TMC) and to assess clinical and radiographic data obtained from mid- to long-term follow-ups (FU) after RTKA with severe bony defects. METHODS: This retrospective case series included 100 consecutive patients of the same centre, who underwent RTKA surgery with TMC for tibia and/or femur bone defects between January 2011 and December 2015. Fourteen patients had died and six were lost for FU, leaving a total of eighty patients (one hundred and twelve TMC) for final evaluation. Clinical parameters including the Knee Society Score (KSS), visual analogue scale (VAS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and range of motion (ROM) were determined preoperatively based on the patients' medical charts, and assessed again during the final FU after an average of 6.1 (5-9) years postoperative. Standardised postoperative X-rays were analysed during the final FU visit for osseointegration of the cones, and any signs of implant loosening were assessed with the modified Knee Society Radiographic review criteria. Perioperative and postoperative complications, reoperations, as well as implant and cone re-revisions were analysed. Survivorship analysis was performed with (a) cone-related revision for any reason and (b) implant component revision for any reason. RESULTS: Previous RTKA had to be performed due to 64 (80%) aseptic and 16 (20%) septic failures. At the final FU, 75 (94%) tibia and 76 (95%) femur TMCs and implants were clinically stable. One patient experienced loosening of cones and implants at the femur and tibia but denied re-revision surgery. There were eight (10%) reoperations including two early wound healing problems, two inlay changes, two periprosthetic fractures, one debridement, antibiotics and implant retention (DAIR), and one secondary patella replacement. The six (7.5%) re-revisions included two aseptic loosening's of the opposite implant without TMC, one arthrodesis for recurrent instability, and three deep infections managed by two two-stage exchanges, and one amputation for persistent infection. At re-revision, all TMC cones were osteointegrated without signs of loosening. The determined clinical parameters showed significant (p < 0.001) postoperative improvement, and objective KSS was rated as excellent in 51%, and as good in 22% of patients at the final FU. The estimated 8-year Kaplan-Meier survival was 95% for TMC and 92.5% for implant components. CONCLUSION: Tantalum metal cones (TMC) demonstrate a secure fixation for treatment of severe femoral and tibial metaphyseal bone defects during RTKA. This fixation concept showed excellent mid- to long-term clinical and radiographic outcomes with promising 8-year survival rates for cones and implant components. LEVEL OF EVIDENCE: Retrospective cohort study, Level IV.

The Significance of Entropy in Grain Boundary Segregation.

The role of entropy in materials science is demonstrated in this report in order to establish its importance for the example of solute segregation at the grain boundaries of bcc iron. We show that substantial differences in grain boundary chemistry arise if their composition is calculated with or without consideration of the entropic term. Another example which clearly documents the necessity of implementing the entropic term in materials science is the enthalpy-entropy compensation effect. Entropy also plays a decisive role in the anisotropy of grain boundary segregation and in interface characterization. The consequences of the ambiguous determination of grain boundary segregation on the prediction of materials behavior are also briefly discussed. All the mentioned examples prove the importance of entropy in the quantification of grain boundary segregation and consequently of other materials properties.

The Contribution of Different Femur Segments to Overall Femoral Torsion.

BACKGROUND: Femoral torsion is a critical parameter in hip and knee disorders. The unproven assumption is that the femoral neck exclusively contributes to the overall torsion of the femur. PURPOSE/HYPOTHESIS: The aim of this study was to measure femoral torsion at different levels in patients with abnormally high or low femoral torsion and to compare the results with healthy volunteers. Our hypothesis was that the pattern of torsion distribution among the different femoral levels varies between patients with abnormal torsion and healthy volunteers. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Magnetic resonance images of patients with a history of patellar instability and torsion of the femur ≥25° (11 patients, 16 femurs) and ≤0° (14 patients, 22 femurs) were analyzed. Our controls were 30 healthy volunteers (60 femurs). To assess femoral torsion, 4 lines were drawn: a first line through the center of the femoral head and neck, a second line through the center of the femur at the top of the lesser trochanter, a third line tangent to the posterior aspect of the distal femur just above the attachment of the gastrocnemius, and a fourth line tangent to the posterior condyles. Three investigators performed the measurements; 1 performed the measurements twice. RESULTS: All femur segments showed significantly different torsion among the high-torsion, low-torsion, and control groups. Regarding the pattern of torsion distribution, on average, all levels contributed to the torsion. The ratio between the average neck and shaft torsion shifted toward a higher value in the high-torsion group, mostly because of a lack of external torsion in the shaft, and toward a lower value in the low-torsion group, owing to both a lack of internal torsion of the neck and increased external torsion in the shaft. CONCLUSION: We established a difference between neck, mid, and distal femoral torsion with reproducible measurements. Our data suggest that all 3 levels of the femur contribute to the total femoral torsion, with a different pattern among patients with high torsion and patellar instability.

Interstitial and substitutional solute segregation at individual grain boundaries of α-iron: data revisited.

Theoretical calculations (usually density-functional-theory methods performed at 0 K) confirm the formerly assumed substitutional phosphorus segregation in α-iron. In contrast, the enthalpy-entropy compensation effect predicts that phosphorus should segregate interstitially. To resolve this discrepancy, we recalculated the values of the segregation enthalpy and entropy for the interstitial segregation of phosphorus according to the Guttmann model of segregation in multicomponent systems. This recalculation is based on earlier measured experimental data and shows that only slight changes in the values of the standard enthalpy and entropy of phosphorus, carbon and silicon segregation are obtained. Consequently, all dependences constructed previously remain qualitatively the same. By thermodynamic considerations based on the enthalpy-entropy compensation effect we quantitatively show that there is an alteration of the position of phosphorus at grain boundaries in α-Fe with increasing temperature: while substitutional segregation is preferred at 0 K, interstitial segregation occurs at temperatures of practical interest.

The position of the tibia tubercle in 0°-90° flexion: comparing patients with patella dislocation to healthy volunteers.

PURPOSE: The aim of this study was to measure the tibia tubercle trochlea groove distance (TT-TG) as a function of knee flexion. Our hypothesis was that there is a different pattern in healthy volunteers and patients with patella instability (PFI). METHODS: Thirty-six knees of 30 patients with at least one dislocation of the patella and 30 knees of 30 healthy volunteers as control group were analysed with magnetic resonance imaging by three different observers. The TT-TG was measured in steps of 15° between 0° and 90° of knee flexion. Furthermore, the alignment of the leg (MA), the femur torsion (FTor) and the tibia torsion (TTor) was calculated. RESULTS: The TT-TG was higher in patients compared to volunteers and in extension compared to flexion. This difference was statistically significant (p<0.05). Most of the patients with a TT-TG above 20 mm in extension showed a high decrease in flexion to normal values. In some patients, this compensating mechanism fails. MA, FTor and TTor were not different in patients and control group (n.s.). CONCLUSION: The TT-TG distance is dynamic and decreased significantly during flexion in knees with PFI and healthy volunteers. However, there were a small number of patients in the PFI group where this compensation mechanism did not work. Therefore, the decision to perform a tibia tubercle osteotomy should not be based on one single measurement in extension or 30° of knee flexion. LEVEL OF EVIDENCE: II.

Systematic analysis of painful total knee prosthesis, a diagnostic algorithm.

Remaining pain after total knee arthroplasty (TKA) is a common observation in about 20% of postoperative patients; where in about 60% of these knees require early revision surgery within five years. Obvious causes of this pain could be identified simply with clinical examinations and standard radiographs. However, unexplained painful TKA still remains a challenge for the surgeon. The management should include a multidisciplinary approach to the patient`s pain as well as addressing the underlying etiology. There are a number of extrinsic (tendinopathy, hip, ankle, spine, CRPS and so on) and intrinsic (infection, instability, malalignment, wear and so on) causes of painful knee replacement. On average, diagnosis takes more than 12 months and patients become very dissatisfied and some of them even acquire psychological problems. Hence, a systematic diagnostic algorithm might be helpful. This review article aims to act as a guide to the evaluation of patients with painful TKA described in 10 different steps. Furthermore, the preliminary results of a series of 100 consecutive cases will be discussed. Revision surgery was performed only in those cases with clear failure mechanism.

Tibial tubercle-posterior cruciate ligament distance: a new measurement to define the position of the tibial tubercle in patients with patellar dislocation.

BACKGROUND: In patients with patellar instability, a pathological tibial tubercle-trochlear groove (TT-TG) distance is a risk factor. However, the TT-TG distance gives no information about the location of the malformation. HYPOTHESIS: Not all patients with a pathological TT-TG distance (≥20 mm) had lateralization of the tibial tubercle. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 2. METHODS: Fifty-eight knees in 49 patients with 2 or more patellar dislocations and 60 knees in 30 volunteers with no history of dislocation were analyzed using magnetic resonance imaging (MRI). The tibial tubercle-posterior cruciate ligament (TT-PCL) distance was defined as the mediolateral distance between the tibial tubercle midpoint and the medial border of the posterior cruciate ligament. The distance was measured parallel to the dorsal aspect of the proximal tibia (dorsal tibia condylar line). Three observers performed the measurements. Significant differences in the TT-PCL distance between the patient and the control group were estimated using an unpaired t test. The inter- and intraobserver variability of the measurement was performed. RESULTS: The intraclass correlation coefficients for inter- and intraobserver variability of the TT-PCL distance were higher than 0.74 and 0.93, respectively. A statistically significant difference (P < .05) was found between the TT-PCL distance in the control group (mean [SD], 18.4 [3.35] mm) and in patients (21.9 [4.30] mm). The mean (SD) TT-TG was 18.9 (5.16) mm in the patient group and 11.9 (4.67) mm in the control group (P < .05). In the control group, 95% had a TT-PCL distance <24 mm. In the patient group, 22 of 58 knee joints (38%) had a TT-PCL distance ≥24 mm. Seventeen of 40 knee joints (43%) with a TT-TG distance ≥20 mm had a TT-PCL distance <24 mm. CONCLUSION: Only 57% of the patients with a pathological TT-TG distance (≥20 mm) had lateralization of the tibial tubercle in relation to the posterior cruciate ligament. The TT-PCL distance is an alternative method for determining the position of the tibial tubercle.

Early revision for isolated internal malrotation of the femoral component in total knee arthroplasty.

PURPOSE: In this prospective study, we determined whether corrective surgery for isolated rotational malalignment of femoral prosthesis components would benefit patients previously treated with total knee arthroplasty. The symptoms, amount of malrotation and type of constraint necessary for the revision prosthesis were investigated. METHODS: Seventy-two patients were screened with computed tomography; of these, 14 had isolated internal malrotation of the femoral component with no other malpositions and were included in the study. A complete exchange arthroplasty with the correction of the malrotated femoral component was performed within 3 years of primary arthroplasty. Mean follow-up was 57 months. RESULTS: At the time of revision, patients suffered either from instability in flexion with good range of motion (ROM) (flexion ≥ 90°) and pain on the lateral side of the distal femur and proximal tibia (n = 8) or from stiffness with pain on the medial side of the proximal tibial and poor ROM (flexion < 90°) (n = 6). One patient showed no patellar maltracking, six patients, patellar tilt and six patients, patellar subluxation. Median internal rotation of the femoral component was 7.1° (4.1-10.0°). A condylar-type revision implant with a posterior-stabilized insert was used in all patients. The corrective surgery resulted in an increase in the mean Knee Society Score from 52/65 to 85/84 points and an improvement in the mean Hospital for Special Surgery knee score from 63 to 83 points. CONCLUSIONS: Correction of isolated internal malrotation of the femoral component ≥ 4° improves patient outcome.

MRI-demonstrated outcome of subchondral stress fractures of the knee after treatment with iloprost or tramadol: observations in 14 patients.

OBJECTIVE: To investigate the outcome of subchondral stress fractures (SSF) of the knee after treatment with the prostacyclin analogue Iloprost or the opioid analgesic Tramadol. DESIGN: Case series/retrospective review. SETTING: Tertiary care center. PATIENTS: Fourteen patients with at least a single subchondral stress fracture of the knee, surrounded by bone marrow edema, visible on T1-weighted and short tau inversion recovery magnetic resonance images. INTERVENTIONS: Nine patients had been treated with oral Iloprost (group 1; 11 SSF) and 5 patients with Tramadol (group 2; 5 SSF) for 4 weeks in the course of a double-blind, randomized clinical trial. MR images were obtained at baseline (1 day before the start of treatment), after 3 months, and after 1 year. MAIN OUTCOME VARIABLES: SSF volumes and their rates of change between baseline and follow-up examinations, as determined on T1-weighted images by computer-assisted quantification. RESULTS: After three months, the SSF volumes had decreased by a median of 42.2% in group 1 and increased by a median of 2.2% in group 2 (P = 0.008). After 1 year, the median decrease in SSF volumes was 100.0% in group 1 and 65.7% in group 2 (P = 0.017). CONCLUSION: This small case series suggests that healing of SSF is more pronounced after Iloprost treatment.

[Surgical treatment of knee joint osteoarthritis in the middle-aged patient]. / Gelenkerhaltende chirurgische Therapie der Gonarthrose im mittleren Lebensalter.

Several treatment options for the osteoarthritis of the knee in middle-aged patients to preserve the joint are available. Arthroscopic debridement is still a valuable treatment when detailed indications are considered. Microfracture procedure showed good and excellent results primarily at a follow-up of 2 years. Cartilage defects up to 4 cm2 should be treated by the mosaic-type osteochondral autologous transplantation. Autologous chondrocyte implantation (ACI) should be discussed when larger defects are presented in the younger patient. Existing osteoarthritis, ACI is not recommended. Up till now, there was no significant difference in outcomes comparing ACI and mosaicplasty or microfracture. Basic for successful surgical cartilage repair is a stable joint with a normal limb. An eventual additional osteotomy of the knee should be considered based on a standing, three-joint radiograph in every patient.

Treatment of deep infection of total knee arthroplasty using a two-stage procedure.

OBJECTIVE: Treatment of deep infection of total knee arthroplasty by two-stage reimplantation. Using an articulating spacer may reduce the disadvantages of a static spacer (ligament contracture, muscle atrophy, muscle contraction, arthrofibrosis, and bone loss). Restoration of pain-free loading and ability to walk. INDICATIONS: Late deep infection after total knee arthroplasty. DEFINITION: infection occurring at least 6 weeks after the initial arthroplasty. CONTRAINDICATIONS: Large metaphyseal bony defects of the distal femur and proximal tibia. Missing or insufficient extensor mechanism. SURGICAL TECHNIQUE: The articulating spacer is made intraoperatively by cleaning and autoclaving the explanted femoral component and the tibial polyethylene insert. These components are reinserted by "press-fit cementing" without cement interdigitation into the trabecular bone. The cement is loaded with antibiotic during the same operation (2-4 g antibiotics per 40 g of cement powder). POSTOPERATIVE MANAGEMENT: With the articulating spacer in place, partial weight bearing with crutches and continuous passive motion daily up to a flexion of 90 degrees are allowed. Usually, reimplantation with a standard revision system is scheduled for 6-12 weeks after spacer implantation. RESULTS: In a prospective study 33 consecutive patients were treated from February 2000 to July 2003. The average period of hospitalization after spacer implantation was 14 days (8-26 days). Three patients had recurrent infection (success rate 91%) after a mean follow-up period of 28 months (12-48 months). The average Hospital for Special Surgery Knee Score could be increased from 67 points (44-84 points) preoperatively to 87 points (53-97 points) after reimplantation. The complications were one temporary peroneal palsy, one dislocation of the spacer due to the absence of the extensor ligaments, and one fracture of the tibia due to substantial primary metaphyseal bone loss.

STIR vs. T1-weighted fat-suppressed gadolinium-enhanced MRI of bone marrow edema of the knee: computer-assisted quantitative comparison and influence of injected contrast media volume and acquisition parameters.

PURPOSE: To compare short tau inversion recovery (STIR) and T1-weighted (T1w) gadolinium (Gd)-enhanced fat-suppressed MRI of bone marrow edema (BME) of the knee, and investigate the influence of injected contrast media volume and variation of major acquisition parameters on apparent BME volume and signal contrast. MATERIALS AND METHODS: STIR and T1w Gd-enhanced fat-suppressed images were obtained from 30 patients with BME of the knee. Two groups of patients were examined with different MR scanners, acquisition parameters, and contrast media volumes. For both sequences, BME volume and signal contrast were assessed by computer-assisted quantification, and were compared through their arithmetic means and correlation coefficients (r(2)). The injected contrast media volume was also correlated with BME volume and signal contrast differences between sequences. RESULTS: A strong correlation between the STIR and Gd-enhanced T1w images was found for BME volume (r(2) = 0.96-0.99) and BME signal contrast (r(2) = 0.86-0.94). Despite the differences in MR acquisition parameters and injected contrast media volume, both sequences depicted an almost identical BME volume in both groups. Contrast media volume showed a moderate correlation (r(2) = 0.40) with BME volume differences. CONCLUSION: STIR is the optimum method for determining the size and signal contrast of BME. The injected contrast media volume appears to have only a limited influence on apparent BME volume.

Texture analysis for tissue discrimination on T1-weighted MR images of the knee joint in a multicenter study: Transferability of texture features and comparison of feature selection methods and classifiers.

PURPOSE: To investigate the reproducibility and transferability of texture features between MR centers, and to compare two feature selection methods and two classifiers. MATERIALS AND METHODS: Coronal T1-weighted MR images of the knees of 63 patients, divided into three groups, were included in the study. MR images were obtained at three different MR centers. Regions of interest (ROIs) were drawn in the bone marrow and fat tissue. Then texture analysis (TA) of the ROIs was performed, and the most discriminant features were identified using Fisher coefficients and POE+ACC (probability of classification error and average correlation coefficients). Based on these features, artificial neural network (ANN) and k-nearest-neighbor (k-NN) classifiers were used for tissue discrimination. RESULTS: Although the texture features differed among the MR centers, features from one center could be successfully used for tissue discrimination in texture data on MR images from other centers. The best results were achieved using the ANN classifier in combination with features selected by POE+ACC. CONCLUSION: The differences in texture features extracted from MR images from different centers seem to have only a small impact on the results of tissue discrimination.

The painful bone marrow edema syndrome of the hip joint.

In this issue of the WKW, Aigner et al have published that, for the first time, a conservative approach with iloprost has shown to be equally successful as the well-documented core decompression surgical approach in patients with BMES of the hip joint. The BME pattern on MR-imaging of the hip joint represents a common but unspecific finding, which may be associated with several diseases requiring different therapeutic strategies (Table 1). It is still controversial, whether BMES of the hip represents a distinct self-limiting disease also known as transient osteoporosis, transient marrow edema, or algodystrophy, or merely reflects a subtype of ON. Since prognosis and therapeutic consequences vary significantly, differential diagnosis between BMES, CRPS and ON is of clinical interest (Table 2). Both, BMES and ON show similar ON risk factors and a male prevalence, while classical CRPS has a history of trauma and a prevalence among females. Clinical presentation of BMES and ON is similar with typical mechanical pain and prevalence of the hip joint. In contrast, classical CRPS shows a diffuse and burning pain in combination with trophic and vasomotor signs, mainly in the hands and feet. Imaging patterns of BMES are more diffuse, across the entire femoral head, while focal and subchondral in ON. In both, the patterns are limited to the femoral head. In contrast to classical CRPS, the imaging changes are located in all periarticular bones, and the soft tissues are always affected. The histological bone marrow changes are similar in all three diseases, but with abundant new bone formation in BMES and CRPS, whereas in ON only limited new bone formation surrounds the focal necrosis with a sclerotic rim. Protected weight-bearing and treatment with iloprost for BMES, but operative treatment for ON, and a sophisticated physiotherapy for CRPS in combination with iloprost are the preferred treatment strategies in our institution.

Painful bone marrow edema of the knee: differential diagnosis and therapeutic concepts.

Bone marrow edema (BME) is a common finding when patients with knee pain are evaluated by MRI. The typical MRI signal patterns for BME are nonspecific, however. This article categorizes painful BME of the knee joint into three distinct etiologic groups and briefly describes therapeutic approaches for each of the 12 different types of BME.

Computer-assisted quantitative analysis of bone marrow edema of the knee: initial experience with a new method.

OBJECTIVE: The purpose of this study was to describe a largely observer-independent computer-assisted method for accurate quantitative analysis of bone marrow edema. MATERIALS AND METHODS: Ten patients with bone marrow edema of the knee were included in the study. Coronal STIR images of the affected knees were obtained using a 1.0-T MR scanner. Size and signal intensity of the bone marrow edema were assessed on the basis of gray-scale value analysis and calculation of a threshold value for differentiating normal and edematous bone marrow. All measurements were carried out three times for statistical analysis. RESULTS: The intraobserver coefficient of variation was 0.89% for the volume and 0.94% for the signal intensity of the bone marrow edema, showing the small impact of manual interference on results produced with this method. CONCLUSION: A computer-assisted method for quantification of bone marrow edema has been described. Intraobserver variation was very low, indicating excellent reproducibility of results. Although the method is too time-consuming for clinical use, it is recommended for research purposes.

Cardiac systolic rotation and contraction before and after valve replacement for aortic stenosis: a myocardial tagging study using MR imaging.

OBJECTIVE: Aortic stenosis leads to the derangement of cardiac function and contraction mode because of chronic pressure overload that is relieved after surgical valve replacement. The purpose of this study was to determine the changes in left ventricular systolic rotation and contraction using MR tagging in patients with aortic stenosis before and after surgical valve replacement compared with age-matched healthy volunteers. MATERIALS AND METHODS: Twelve patients with aortic stenosis were examined with an electrocardiographically triggered two-dimensional tagging sequence at 1.5 T before and 12 months after surgical valve replacement for the evaluation of wall function of the apical, mid ventricular, and basal levels. Eight healthy volunteers in the same age group served as the control group. RESULTS: Before surgery, all patients showed a significant increase of apical rotation (22.2 degrees +/- 5.9 degrees vs 10.3 degrees +/- 2.5 degrees, p < 0.0001) and overall left ventricular torsion (25.1 degrees +/- 6.6 degrees vs 14.5 degrees +/- 3.7 degrees, p < 0.001); basal rotation was not significantly different (-2.9 degrees +/- 2.1 degrees vs -4.2 degrees +/- 1.9 degrees, p = not significant) compared with the volunteer group. Apical rotation and torsion were negatively correlated with left ventricular mass (r = -0.73, p < 0.01, and r = -0.61, p < 0.05, respectively) and end-diastolic volume (r = -0.73, p < 0.01 and r = -0.64, p < 0.03, respectively). One year after surgery, basal rotation was reduced in the patients with aortic stenosis compared with the patients in the control group (-1.9 degrees +/- 1.8 degrees, p < 0.01). In comparison with preoperative values, apical rotation (14.2 degrees +/- 3.6 degrees, p < 0.01) also decreased but was still elevated, and this resulted in a normalization of left ventricular torsion (16.1 degrees +/- 3.7 degrees, p < 0.01). CONCLUSION: Surgical valve replacement for aortic stenosis leads to normalization of the left ventricular torsion 1 year after surgery. Pressure overload before surgery is associated with an increase of systolic left ventricular wringing motion, possibly serving as a compensatory mechanism. This mechanism declines with increasing left ventricular hypertrophy and dilatation.