D-lactate is a promising biomarker for the diagnosis of periprosthetic joint infection.

Introduction: Reliable biomarkers for the diagnosis of periprosthetic joint infection (PJI) are of paramount clinical value. To date, synovial fluid leukocyte count is the standard surrogate parameter indicating PJI. As D-lactate is almost solely produced by bacteria, it represents a promising molecule in the diagnostic workflow of PJI evaluation. Therefore, the purpose of this study was to assess the performance of synovial fluid D-lactate for diagnosing PJI of the hip and knee. Materials and Methods: These are preliminary results of a prospective multicenter study from one academic center. Seventy-two consecutive patients after total hip arthroplasty (THA) or total knee arthroplasty (TKA) were prospectively included. All patients received a joint aspiration in order to rule out or confirm PJI, which was diagnosed according to previously published institutional criteria. Synovial fluid D-lactate was determined spectrophotometrically at 450 nm. Receiver operating characteristic (ROC) analysis was performed to assess the diagnostic performance. Results: Eighteen patients (25%) were diagnosed with PJI and 54 patients (75%) were classified as aseptic. Synovial fluid D-lactate showed a sensitivity of 90.7% (95% CI: 79.7%-96.9%) and specificity of 83.3% (95% CI: 58.6%-96.4%) at a cut-off of 0.04 mmol/L. The median concentration of D-lactate was significantly higher in patients with PJI than in those with aseptic conditions (0.048 mmol/L, range, 0.026-0.076 mmol/L vs. 0.024 mmol/L, range, 0.003-0.058 mmol/L, p < 0.0001). The predominat microogranisms were staphylococci, followed by streptococci and gram-negative bacteria. Conclusion: D-lactate bears a strong potential to act as a valuable biomarker for diagnosing PJI of the hip and knee. In our study, a cutoff of 0.04 mmol/L showed a comparable sensitivity to synovial fluid leukocyte count. However, its specificity was higher compared to conventional diagnostic tools. The additional advantages of D-lactate testing are requirement of low synovial fluid volume, short turnaround time and low cost.

With the exception of the Hill-Sachs interval, CT and MRI show no significant differences in the diagnostic value of the HSL measurement regardless of the measurement technique.

PURPOSE: The aim of the current study was to compare the diagnostic precision and reliability of different methods in measuring Hill-Sachs lesions (HSLs) using MRI and CT. METHODS: A total of 80 consecutive patients with a history of anterior shoulder instability were retrospectively included. The preoperative CT and MRI scans of the affected shoulders were analysed. To investigate the ability of the Franceschi grading, Calandra classification, Richards, Hall, and Rowe grading scale, Flatow percentage and "glenoid track" assessment according to Di Giacomo et al. to quantify the extent of humeral bone loss, the results of each measurement method obtained with MRI were compared with those achieved with CT. In addition, the intra- and inter-rater reliabilities of each measurement method using CT and MRI were calculated and compared. RESULTS: A significant difference was found between CT and MRI in the determination of the Hill-Sachs interval (HSI) (p = 0.016), but not between the results of any of the other measurement techniques. With the exceptions of the Franceschi grade and Calandra classification, all measurement methods showed good or excellent intra- and inter-rater reliabilities for both MRI and CT. CONCLUSIONS: While the determination of the HSI with MRI was more accurate, all other analysed techniques for measuring the amount of humeral bone loss showed similar diagnostic precision. With regard to the intra- and inter-rater reliabilities, all measurement techniques analysed, with the exception of the Franceschi and Calandra classifications, provided good to very good reliabilities with both CT and MRI. LEVEL OF EVIDENCE: III.

The tibial cut in total knee arthroplasty influences the varus alignment, the femoral roll-back and the tibiofemoral rotation in patients with constitutional varus.

PURPOSE: Different alignment types for a better outcome after TKA were described. However, it is not clear how kinematic alignment influences knee joint kinematic. The purpose of this study was to analyze whether adapted tibial cuts in constitutional varus knees affect knee joint kinematics regarding femoral roll-back, varus/valgus angle, and femorotibial rotation. METHODS: Seven cadaveric knees with constitutional varus alignment were examined in the native state and after implantation of a cruciate retaining (CR)-TKA with 0°, 3° and 6° tibia cuts using an established knee joint simulator. The effects of varus alignment on femorotibial rollback and rotation was determined. In addition, the native knee joint and different tibial cuts in CR-TKA were compared with Student's t test. RESULTS: Total knee replacement with a 3° and 6° varus tibia cut had the greatest varus deviation to the native knee (mean 1.6° ± 0.09°, respectively); while, knees with a 0° (mean 0.2° ± 0.01°) tibia cut were most similar to the constitutional varus knee joint. The femoral roll-back in the medial compartment was increased in the native knee (5.7-12.5 mm). A 6° varus cut had a restricted translation in the medial compartment (2-3.2 mm). In the lateral compartment, the extensive translation was observed with a 0° varus cut, followed by 3° and 6° and the native knee. All cuts showed significantly different mean values. Only the cuts at 3° and at 6° in the medial compartment and the cuts at 0° and at 3° in the lateral compartment did not differ significantly. In respect to tibiofemoral rotation, 0° and 3° varus cuts across all loads had the least difference to the native knee (3.4°), with a 0° varus cut showing a higher absolute internal rotation of the tibia than the native knee. Changes in knee kinematics of the tibiofemoral rotation showed significantly different mean values. CONCLUSION: The potentially improved outcome parameters in TKA with adapted tibia cuts in constitutional varus knees cannot be completely explained by the changes to knee kinematics. Mechanical alignment seems to result in more balanced load distribution and kinematics more closely resembling the native knee. From a kinematic point of view, it is not recommended to place the tibia in more than 3° of varus. LEVEL OF EVIDENCE: Biomechanical study.

Degeneration alters the biomechanical properties and structural composition of lateral human menisci.

OBJECTIVE: Because the literature relating to the influence of degeneration on the viscoelasticity and tissue composition of human lateral menisci remains contradictory or completely lacking, the aim of this study was to fill these gaps by comprehensively characterising the biomechanical properties of menisci with regard to the degree of degeneration. DESIGN: Meniscal tissue from 24 patients undergoing a total knee replacement was collected and the degeneration of each region classified according to Pauli et al. For biomechanical characterisation, compression and tensile tests were performed. Additionally, the water content was determined and infrared (IR) spectroscopy was applied to detect changes in the structural composition, particularly of the proteoglycan and collagen content. RESULTS: With an increasing degree of degeneration, a significant decrease of the equilibrium modulus was detected, while simultaneously the water content and the hydraulic permeability significantly increased. However, the tensile modulus displayed a tendency to decrease with increasing degeneration, which might be due to the significantly decreasing amount of collagen content identified by the IR measurements. CONCLUSION: The findings of the current study may contribute to the understanding of meniscus degeneration, showing that degenerative processes appear to mainly worsen viscoelastic properties of the inner circumference by disrupting the collagen integrity.

Optimizing Manufacturing and Osseointegration of Ti6Al4V Implants through Precision Casting and Calcium and Phosphorus Ion Implantation? In Vivo Results of a Large-Scale Animal Trial.

BACKGROUND: Uncemented implants are still associated with several major challenges, especially with regard to their manufacturing and their osseointegration. In this study, a novel manufacturing technique-an optimized form of precision casting-and a novel surface modification to promote osseointegration-calcium and phosphorus ion implantation into the implant surface-were tested in vivo. METHODS: Cylindrical Ti6Al4V implants were inserted bilaterally into the tibia of 110 rats. We compared two generations of cast Ti6Al4V implants (CAST 1st GEN, n = 22, and CAST 2nd GEN, n = 22) as well as cast 2nd GEN Ti6Al4V implants with calcium (CAST + CA, n = 22) and phosphorus (CAST + P, n = 22) ion implantation to standard machined Ti6Al4V implants (control, n = 22). After 4 and 12 weeks, maximal pull-out force and bone-to-implant contact rate (BIC) were measured and compared between all five groups. RESULTS: There was no significant difference between all five groups after 4 weeks or 12 weeks with regard to pull-out force (p > 0.05, Kruskal Wallis test). Histomorphometric analysis showed no significant difference of BIC after 4 weeks (p > 0.05, Kruskal-Wallis test), whereas there was a trend towards a higher BIC in the CAST + P group (54.8% ± 15.2%), especially compared to the control group (38.6% ± 12.8%) after 12 weeks (p = 0.053, Kruskal-Wallis test). CONCLUSION: In this study, we found no indication of inferiority of Ti6Al4V implants cast with the optimized centrifugal precision casting technique of the second generation compared to standard Ti6Al4V implants. As the employed manufacturing process holds considerable economic potential, mainly due to a significantly decreased material demand per implant by casting near net-shape instead of milling away most of the starting ingot, its application in manufacturing uncemented implants seems promising. However, no significant advantages of calcium or phosphorus ion implantation could be observed in this study. Due to the promising results of ion implantation in previous in vitro and in vivo studies, further in vivo studies with different ion implantation conditions should be considered.

Difficult to treat: are there organism-dependent differences and overall risk factors in success rates for two-stage knee revision?

OBJECTIVES: Failure after two-stage procedure for periprosthetic joint infection (PJI) is a rare, but devastating complication. Some authors assume a correlation of underlying organisms and recurrence rate. Methicillin-resistant Staphylococci (MRS) and other organisms (quinolone-resistant Gram-negative bacteria, rifampicin-resistant Staphylococcus, Enterococcus, and Candida) are meant to be "difficult to treat" (DTT) with an inferior outcome for two-stage revision. In addition to the type of bacteria, some more risk factors seem to be present. The aim of this study was (1) to detect a difference of reinfection rates between reinfection-causing groups of bacteria ["difficult to treat" (DTT), "easy to treat" (ETT) and methicillin-resistant staphylococci (MRS)] after a two-stage procedure, and (2) find overall risk factors for reinfection in a standardized long (spacer insertion for at least 6 weeks) two-stage procedure for periprosthetic knee infection. METHODS: One hundred and thirty-seven two-stage revisions for periprosthetic knee infection were performed at one tertiary referral center. Finally, 96 patients could be included for analyses. Possible risk factors (comorbidities, prior surgery, etc.) and the types of organisms were documented. Quinolone-resistant Gram-negative bacteria, rifampicin-resistant Staphylococcus, Enterococcus, and Candida were classified as "difficult to treat" (DTT). Methicillin-resistant Staphylococci were summarized as "MRS", all other organism are summarized as "easy to treat" (ETT). Statistical analyses included univariate analysis (t test, Fisher's exact test, Chi square test) and logistic regression analysis. RESULTS: There were no statistical significant differences in recurrent infection rates between organism groups (DTT vs. ETT, p = 0.674; DTT vs. MRS, p = 0.705; ETT vs. MRS, p = 0.537). Risk factors seem to be "need of revision after first stage" (p = 0.019, OR 5.62) or completed second stage (p = 0.000, OR 29.07), numbers of surgeries (p = 0.028) and alcohol abuse (p = 0.019, OR 5.62). CONCLUSIONS: Revision needed during or after a two-stage exchange, numbers of surgeries and alcohol abuse are risk factors for recurrence, a different recurrence rates between organism-groups cannot be shown. The absence of significant differences in recurrence rates points to the importance of the individuality of each periprosthetic infection case: a reduction of necessary surgeries (with a thorough debridement, appropriate antibiotic addition to spacers) and the control of comorbidities (alcohol abuse) appear to be essential components of a two-stage exchange.

Cartilage survival of the knee strongly depends on malalignment: a survival analysis from the Osteoarthritis Initiative (OAI).

PURPOSE: Progression of osteoarthritis over time is poorly understood. The aim of the current study was to establish a timeline of "cartilage survival rate" per subregion of the knee in relation to mechanical alignment of the lower extremity. The study hypothesized that there are differences in progression of osteoarthritis between varus, valgus and physiologic lower extremity alignment. METHODS: Based on hip-knee-ankle standing radiographs at baseline, 234 knees had physiologic (180° ± 3°, mean 179.7°), 158 knees had varus (< 177°; mean 174.5°) and 66 knees valgus (> 183°; mean 185.2°) alignment (consecutive knees of the OAI "Index Knee" group, n = 458; mean age 61.7; 264 females). The Osteoarthritis Initiative (OAI; a multi-center, longitudinal, prospective observational study of knee osteoarthritis [30] using MRIs) defines progressive OA as a mean decrease of cartilage thickness of 136 µm/year and a mean decrease of cartilage volume by 5% over 1 year (DESS sequences, MRI). A Kaplan-Meier curve was generated for osteoarthritis progression based on OAI criteria. RESULTS: Osteoarthritis progression based on volume decrease of 5% in varus knees occurred after 30.8 months (medial femoral condyle), after 37 months (medial tibia), after 42.9 months (lateral femoral condyle) and 43.4 months (lateral tibia), respectively. In a valgus alignment progression was detectable after 31.5 months (lateral tibia), after 36.2 months (lateral femoral condyle), after 40.4 months (medial femoral condyle) and 43.8 months (medial tibia), respectively. The physiological alignment shows a progression after 37.8 months (medial femoral condyle), after 41.6 months (lateral tibia), after 41.7 months (medial tibia) and after 43 months (lateral femoral condyle), respectively. CONCLUSION: Based on data from the OAI, the rate and location (subregion) of osteoarthritis progression of the knee is strongly associated with lower extremity mechanical alignment. LEVEL OF EVIDENCE: Level I (prognostic study).

The tibial cut influences the patellofemoral knee kinematics and pressure distribution in total knee arthroplasty with constitutional varus alignment.

PURPOSE: The current literature suggests that kinematic total knee arthroplasty (kTKA) may be associated with better outcome scores in patients with constitutional varus alignment. The underlying patellofemoral kinematic changes (patella tilting and patella tracking) and patellofemoral pressure distribution have not yet been described. The present study compared the effects of different tibial cuts, as used in kTKA, on patellofemoral knee kinematics and the pressure distribution, in addition to comparisons with the natural constitutional varus knee. METHODS: Seven cadaveric knee joints with constitutional varus alignment were examined in the native state and after 0°, 3°, or 6° tibial cut cruciate-retaining (CR)-TKA using an established knee joint simulator. The effects on patella rotation/patella tilting, patellofemoral pressure, and patellofemoral length ratios (= patella tracking) were determined. In addition, the natural knee joint and different tibial cuts in CR-TKA were compared (Student's t test). RESULTS: In the patellofemoral joint, 6° CR-TKA was associated with the greatest similarity with the natural constitutional varus knee. By contrast, knees subjected to 0° CR-TKA exhibited the largest deviations of patellar kinematics. The smallest difference compared with the natural knee joint concerning patella tilting was found for 6° CR-TKA (mean 0.4°, p < 0.001), and the largest difference was noted for 0° CR-TKA (mean 1.7°, p < 0.001). Concerning patellofemoral pressure, 6° CR-TKA resulted in outcomes most similar to the natural knee joint, featuring a mean difference of 3 MPa. The largest difference from the natural knee joint was identified for 0° CR-TKA, with an average difference of 8.1 MPa (p < 0.001; total mean 17.7 MPa). Meanwhile, 3° and 6° CR-TKA induced medialization of the patella, with the latter inducing the largest medialization value of 4.5 mm at 90° flexion. CONCLUSIONS: The improved outcome parameters in kTKA described in the literature could be attributable to the similar kinematics of the patellofemoral joint relative to the normal state. The current study confirmed the similar kinematics between the native constitutional varus knee joint and knee joints subjected to 3° or 6° CR-TKA (patellofemoral rotation/patella tilting and patella pressure). Conversely, there was pronounced medialization of the patella following 6° CR-TKA. Patella pressure and patella tilting are described in the literature as possible causes of anterior knee pain after TKA, whereas medialization of the patella, which is also influenced by other causes, might play a subordinate role. LEVEL OF EVIDENCE: V, Biomechanical study.

Outcome of Irrigation and Debridement after Failed Two-Stage Reimplantation for Periprosthetic Joint Infection.

INTRODUCTION: Two-stage revision is the gold standard for the treatment of deep implant infection after knee or hip arthroplasty. Irrigation and debridement may be a treatment option for failed 2-stage revisions in cases where a reinfection occurs within 30 days or the symptoms exist not longer than 3 weeks and is appealing because of its low morbidity. We determined the incidence of recurrent infections following irrigation and debridement for failed two-stage revision hip and knee arthroplasty. METHODS: We performed a single center retrospective review of periprosthetic hip and knee infections treated with a two-stage procedure from 2002 to 2010. All patients that subsequently underwent irrigation and debridement for a subsequent infection were selected for the current study. RESULTS: 440 two-stage revisions were performed between 2002 and 2010. Fifty-one two-stage revisions failed (11.6%). Nineteen failed two-stage revisions were treated with irrigation and debridement; 12 (63.2%) patients remained free of infection at follow-up (mean follow-up: 39 months; range, 24-90 months), infection persisted in 6 patients (31.6%), and 1 patient died (5.3%). CONCLUSIONS: Success rates of irrigation and debridement for failed two-stage procedures are similar to the success rates of irrigation and debridement in primary implant infections. According to the current paper, irrigation and debridement are an acceptable treatment for acute reinfections after failed two-stage revision if performed within the first 30 postoperative days after failed two-stage procedure or if symptoms are present for less than 3 weeks in the presence of a susceptible organism.

[Measurement of acetabular cup inclination in anteroposterior pelvic radiogram : An indicator of quality after primary total hip arthroplasty?] / Die Pfanneninklinationsmessung in der Beckenübersichtsaufnahme : Ein Qualitätsindikator nach Hüft-TEP-Primärimplantation?

BACKGROUND AND OBJECTIVE: Acetabular cup orientation, consisting of pelvic positioning, version and inclination, can influence short-term and long-term results after total hip arthroplasty (THA). The radiographic measurement of acetabular cup inclination represents an indicator of quality for the EndoCert certification in Germany. The purpose of this study was to determine the intrarater and interrater reliability of radiographic measurements of acetabular cup inclination after THA. MATERIAL AND METHODS: In this study four independent investigators with different levels of expertise retrospectively performed measurements on radiograms (anteroposterior pelvic radiogram) from 99 patients. The intraclass correlation coefficient (ICC) and Pearson's correlation coefficient were determined and were considered statistically significant with r > 0.8 and p < 0.05. RESULTS AND CONCLUSION: A high correlation was found for both intrarater and interrater reliability based on determination of Pearson's correlation coefficient and the ICC with r > 0.9 and p < 0.001 for all measurements. Based on these results the radiographic measurement of acetabular cup inclination can be considered as a simple measuring tool with high intrarater and interrater reliability. As cup orientation consists of inclination, version and positioning, the exclusive measurement of cup inclination for radiological quality assessment needs to be discussed critically.

Translation, validation, and cross-cultural adaption of the Western Ontario Meniscal Evaluation Tool (WOMET) into German.

PURPOSE: The Western Ontario Meniscal Evaluation Tool (WOMET) was developed in order to investigate the health-related quality of life of patients with meniscal pathologies. The aim of the present study was to translate and validate the WOMET into German. METHODS: A standardized forward backward translation of the WOMET into German was first performed. One hundred ninety-two patients with isolated meniscal tears completed the German version of the WOMET as well as the Western Ontario McMasters University Arthritis Index, and the Knee Osteoarthritis Outcome Score. Furthermore, reliability, construct validity, feasibility, internal consistency, ceiling, and floor effects were then calculated. RESULTS: Excellent feasibility (85.4% fully complete questionnaire), internal consistency (Cronbach's α = 0.92), and test-retest reliability (ICC, r = 0.90) were found. The standard error of measurement and the minimal detectable change were ±4.6 and 12.7 points, respectively. All predefined hypothesises were confirmed. No floor or ceiling effects were found. CONCLUSIONS: The presented German version of the WOMET is a valid and reliable tool for investigating the health-related quality of life of German-speaking patients with meniscal pathologies. LEVEL OF EVIDENCE: Cross-sectional study, Level II.

[Large Hibernoma of the Proximal Upper Arm and the Axilla - Literature Review and Case Description of a Very Rare Benign Soft Tissue Tumor]. / Großes Hibernom des proximalen Oberarms und der Axilla ­ Literaturüberblick und Fallbeschreibung eines sehr seltenen gutartigen Weichteiltumors.

Hibernomas are very rare benign soft tissue tumors arising from brown fat. Malignant transformation or metastases are unknown. Males seems to be affected more often. Most patients are aged 20 to 40, but patients with intraosseous hibernomas are older. In children, hibernomas are extremely rare. The tumors grow slowly and have usually been present for a few years on presentation. Hibernomas are typically located on the thigh, neck, axilla or in the peri- und interscapular region. Diagnostic work-up in symptomatic hibernomas usually includes conventional X-ray and magnetic resonance tomography (MRI) with contrast medium. Asymptomatic hibernomas are often found accidentally in the diagnostic work-up of other diseases. Important differential diagnoses are lipomas, well differentiated liposarcomas, rhabdomyomas, granular cell tumors and sebeceous adenomas. Incisional biopsy should be performed to allow definitive histological diagnosis before definitive therapy. According to the literature, histologically preserved hibernomas can be removed with curative intention and marginal resection. After complete tumor removal, local recurrence has not been described. The following article describes the case of a large hibernoma of the proximal arm, involving the axilla, and describes the epidemiology, clinical behavior, diagnostic work-up, therapy and prognosis of this very rare benign fatty soft tissue tumor, on the basis of a review of current literature.

[Infections of the spine : Therapeutic strategies]. / Infektionen der Wirbelsäule : Therapiestrategien.

Spinal infections are relatively rare entities but the incidence is significantly increasing due to the rapidly growing numbers of interventions on the spine. Primary infections of intervertebral discs (spondylodiscitis) and vertebral bodies (spondylitis) are distinguished from secondary postinterventional infections. Treatment relies primarily on either conservative or surgical management. In the absence of indications for surgery, a conservative approach is indicated when the patient is neurologically intact and the bony destruction is minimal. Conservative therapeutic options are based on the microbiological diagnosis and use of antibiotics, immobilization, analgesics and orthotics. Indications for a surgical intervention are the presence of neurological deficits, intraspinal abscesses, extensive osseous destruction and failure of conservative management. Surgical therapy focusses on the decompression of neural structures, debridement and eradication of the focus of infection, pathogen identification, correction of the deformity and restoration of a physiological spinal profile. Following a postoperative infection a timely diagnosis including assessment of the extent of infection is crucial. In the case of a purely superficial infection, antibiotic prophylaxis and close monitoring is indicated. If findings are pronounced surgical revision, debridement together with antibiotic therapy and if necessary vacuum-assisted closure as well as revision ranging from exchange of implants to complete removal of osteosynthetic material are required. Spinal infections are severe conditions frequently with residual long-term sequelae, whether the patients are managed conservatively or surgically.

Antioxidative therapy in an ex vivo human cartilage trauma-model: attenuation of trauma-induced cell loss and ECM-destructive enzymes by N-acetyl cysteine.

OBJECTIVE: Mechanical trauma of articular cartilage results in cell loss and cytokine-driven inflammatory response. Subsequent accumulation of reactive oxygen (ROS) and nitrogen (RNS) species enhances the enzymatic degradation of the extracellular matrix (ECM). This study aims on the therapeutic potential of N-acetyl cysteine (NAC) in a human ex vivo cartilage trauma-model, focusing on cell- and chondroprotective features. DESIGN: Human full-thickness cartilage explants were subjected to a defined impact trauma (0.59 J) and treated with NAC. Efficiency of NAC administration was evaluated by following outcome parameters: cell viability, apoptosis rate, anabolic/catabolic gene expression, secretion and activity of matrix metalloproteinases (MMPs) and proteoglycan (PG) release. RESULTS: Continuous NAC administration increased cell viability and reduced the apoptosis rate after trauma. It also suppressed trauma-induced gene expression of ECM-destructive enzymes, such as ADAMTS-4, MMP-1, -2, -3 and -13 in a dosage- and time-depending manner. Subsequent suppression of MMP-2 and MMP-13 secretion reflected these findings on protein level. Moreover, NAC inhibited proteolytic activity of MMPs and reduced PG release. CONCLUSION: In the context of this ex vivo study, we showed not only remarkable cell- and chondroprotective features, but also revealed new encouraging findings concerning the therapeutically effective concentration and treatment-time regimen of NAC. Its defense against chondrocyte apoptosis and catabolic enzyme secretion recommends NAC as a multifunctional add-on reagent for pharmaceutical intervention after cartilage injury. Taken together, our data increase the knowledge on the therapeutic potential of NAC after cartilage trauma and presents a basis for future in vivo studies.

[Acetabular Osteolysis in Total Hip Replacement - When to Retain the Cup?]. / Azetabuläre Osteolysen bei Hüfttotalendoprothese - wann kann die Pfanne belassen werden?

Periacetabular osteolysis is a frequent long-term complication of cementless total hip arthroplasty. The decision whether to retain or to revise a cup in the presence of osteolysis remains a challenge. The options are regular clinical and radiological check-ups, isolated liner exchange with and without bone grafting, and complete cup revision. Thorough preoperative diagnostics, including a medical history, examination and imaging, are mandatory for correct decision making. In most patients, computed tomography is useful to assess periacetabular osteolysis. If the cup is well-fixed and positioned in an asymptomatic patient without progressive osteolysis and no implant defect or higher grade polyethylene wear and no signs of infection, continuous clinical and radiological monitoring is preferred. If imaging reveals cup loosening, malposition, osteolysis localised in a weight-bearing area, imminent or present periprosthetic fractures, rapid progressive osteolysis, implant defects or massive inlay wear, surgical treatment may be preferred. Cup revision is usually performed in such patients. If the cup is well-positioned and well-fixed in the X-ray, the procedure has to be discussed with the patient individually. Apart from patient-specific risk factors, the risk of further progression has to be assessed. Isolated liner exchange can be performed if the patient is asymptomatic and the cup proves to be stable intraoperatively. It is still unclear whether filling osteolyses through screw holes or osseous windows is of long-term benefit.

Can the frontal tibiofemoral alignment be assessed on anteroposterior knee radiographs?

BACKGROUND: The aim of total knee arthroplasty is, amongst others, the reconstruction of a physiological axis of the leg with a tibiofemoral angle in the frontal plane of an average of 6°. The aim of this study is to clarify how much of the bone length on the femur and tibia has to be reproduced on anteroposterior (AP) knee radiographs in order to determine the leg's alignment after a total knee arthroplasty. MATERIALS AND METHODS: We analyzed the postoperative hip-to-ankle (HTA) radiographs of 100 patients who had undergone a total knee arthroplasty at our institution. RESULTS: There were strong correlations between the measured values on HTA and 20 cm bone length [lateral distal femur angle (LDFA) r = 0.887, medial proximal tibial angle (MPTA) r = 0.874, tibiofemoral angle (TFA) r = 0.888], but not between the measurements on HTA and 10 cm (LDFA r = 0.267, MPTA r = 0.102, TFA r = 0.161). There were significant differences between all measurements both on HTA and 20 cm and on HTA and 10 cm, with the exception of the LDFA between HTA and 10 cm (p = 0.085) and of the MPTA between HTA and 20 cm (p = 0.227). The intra- and inter-observer correlations were both high. CONCLUSION: If preoperatively crude axis deviations are excluded, the tibiofemoral angle on AP knee radiographs can be determined with an accuracy of ±2.6° if at least 20 cm length of bone is reproduced (measured from the femoral and tibial joint line). Due to the high 95 % confidence intervals and bearing in mind that deviations greater than 3° may lead to inferior clinical results, however, it appears inappropriate to determine lower limb alignment with anteroposterior radiographs. LEVEL OF EVIDENCE: Level 2.

Complications associated with 133 static, antibiotic-laden spacers after TKA.

PURPOSE: Periprosthetic infection after total knee arthroplasty (TKA) is a devastating complication, with a two-stage revision currently the 'gold standard' treatment for chronic infections. There is, however, a lack of information about mechanical complications during this treatment. The purpose of this study was to determine: (1) the rate and type of mechanical complications encountered during a two-stage exchange revision for periprosthetic infection of the knee and (2) possible factors of influence. METHODS: Between 2000 and 2011, 133 patients received an antibiotic-laden cement spacer as part of a two-stage protocol. The overall frequency and types of complication were recorded (fissure/fracture of the tibia or femur, spacer fracture, subluxation of the patella, peroneus affection, wound healing disorder and mobilization under anaesthesia based on a constricted ROM). Also analysed were potential influencing factors (BMI, ASA classification, length of the interval with the enclosed spacer, revision needed after explantation, revision needed after reimplantation, complications after primary TKA, service life of the primary prosthesis) in terms of the overall outcome (possibility of reimplantation, complications during the two-stage protocol). RESULTS: The mean age at the time of the first stage operation was 70.1 ± 9.9 years. Overall, 20 of 133 patients suffered one of the complications mentioned above (15 %). Fracture/fissure of the tibia occurred in nine cases (6.8 %) and fracture/fissure of the femur in three (2.3 %). There were also three mobilizations under anaesthesia after TKA reimplantation, two affections of the peroneus nerve, one spacer fracture, one subluxation of the patella and one wound healing disorder. The influencing factors on the overall outcome were revision after reimplantation (reinfection, p = 0.002), revision after explantation (reinfection, p = 0.044), prior aseptic revision after primary TKA (reimplantation, p = 0.019), and prior two-stage revision (reimplantation, p = 0.002). CONCLUSION: A two-stage revision arthroplasty using a static cement spacer is an effective therapy for infected TKAs. The complication rate of 15 % (including restricted ROM after reimplantation) is acceptable. Influencing factors (revision needed after reimplantation, revision needed after explantation) can be demonstrated and should be avoided during the two-stage protocol.