Which Knee Phenotypes Exhibit the Strongest Correlation With Cartilage Degeneration?

BACKGROUND: Although articular wear has been thoroughly investigated, the effects of abnormal limb alignment on cartilage degeneration over time remain poorly understood. An exact assessment of the correlation between lower limb alignment abnormalities and MRI-observed articular degradation may be helpful for understanding the progression of osteoarthritis and planning future treatment. QUESTION/PURPOSE: In patients with moderate to advanced osteoarthritis, (1) is there a correlation between overall alignment of the knee and the location of cartilage degradation over time, as measured by cartilage metrics on MRI? (2) Is there a correlation between tibial alignment and the location of cartilage degradation over time, as measured by cartilage metrics on MRI? (3) Is there a correlation between femoral alignment and the location of cartilage degradation over time, as measured by cartilage metrics on MRI? METHODS: Between April 2020 and September 2022, we retrospectively evaluated 3106 patients aged 45 to 79 years who were at risk of experiencing knee osteoarthritis. Of those, we considered as potentially eligible 600 symptomatic index knees with radiographic evidence of osteoarthritis-Kellgren-Lawrence Grades 2 or 3-at the baseline visit. Of those, 22% (134 of 600) were excluded because of a lack of proper alignment measurements, leaving 466 knees with measurements of radiologic alignment angles and quantitative MRI cartilage measurements of 16 subregions of the femorotibial compartment at baseline and 12 and 24 months, and 64 knees at the 48-month visit for investigation in the current study. Data regarding cartilage measurements of the patellofemoral compartment were not available for analysis. The knees were categorized into one of the possible 25 different phenotypes of the lower extremity established by previous research, based on the neutral, valgus, or varus distal mechanical angle of the femur and proximal tibial mechanical angle on full-limb radiographs. We applied ANOVA to estimate the effect size of the overall, femoral, and tibial alignments on the location of cartilage degradation over time, as measured by cartilage metrics on MRI. RESULTS: We found that the overall combinations of a valgus femur with valgus tibia or a valgus femur with varus tibia were associated with the highest loss of cartilage in the internal medial tibial subregion and anterior lateral tibial subregion (η 2 p = 0.39 and 0.17, respectively). For the tibia, we found that the combination of a valgus femur with valgus tibia was associated with an increase in the area of subchondral bone denuded of cartilage in the central lateral tibial subregion (η 2 p = 0.2). For the femur, we found that the combination of a valgus femur with valgus tibia was associated with loss of cartilage thickness in the central weightbearing lateral femorotibial compartment (η 2 p = 0.15). CONCLUSION: We found that certain alignment patterns are associated with rapid deterioration of cartilage and exposure of subchondral bone, even over short time periods. In particular, the valgus femur with valgus tibia and valgus femur with varus tibia phenotypes deserve special attention, because they exhibited a strong, atypical correlation with the internal medial tibial subregion and anterior lateral tibial subregion, respectively. This is important because valgus and varus malalignment cause isolated lateral and medial compartment disease, respectively. Therefore, these findings suggest that a more individualized approach for limb axis deformities is valuable, and hint at a more meticulous radiologic and clinical investigation, perhaps using different imaging modalities, especially when assessing the exact cartilage state and planning an intervention. Future studies, ideally biomechanical, might help in assessing the long-term effects of the various phenotypes on cartilage degradation and their relevance in reconstructive surgery. LEVEL OF EVIDENCE: Level II, prognostic study.

Tourniquet does not affect intraoperative kinematics during total knee arthroplasty: Results of a prospective study using a robotic assistance system.

PURPOSE: Tourniquet use during total knee arthroplasty (TKA) remains controversial. There are limited data demonstrating the effect of tourniquet use on flexion and extension gaps. The use of a tourniquet can theoretically affect the kinematics of the knee joint, specifically the extension and flexion gaps and the laxity, by mechanically compressing the soft tissues including the muscles above the knee joint. Therefore, this study was designed to prospectively evaluate changes in flexion and extension gaps with and without the use of a tourniquet. METHODS: The following prospective study included 50 consecutive patients who underwent TKA using a surgical robot. The inclusion criteria were advanced osteoarthritis (OA) and varus-alignment or valgus-alignment <3° (hip-knee-ankle angle, standing long-leg X-ray), and the exclusion criteria were BMI >35 kg/m2 and mechanical axis in >3° valgus. A CR-TKA was performed, and the medial and lateral gaps (in mm) throughout the full range of motion in 10° increments were recorded. The procedure was conducted both with and without an applied tourniquet (350 mmHg). RESULTS: No significant differences were observed in the medial joint space. By contrast, the lateral gap showed significant differences in 10-20° of flexion (with a tourniquet 1.9 mm vs. without a tourniquet 2.1 mm, p = 0.018), 20-30° (1.6 vs. 1.8 mm, p = 0.02), 100-110° (0.9 vs. 1.1 mm, p = 0.021), and 110-120° (0.8 vs. 1 mm, p = 0.038). Thus, at the above degrees of flexion on the lateral side, there was a decrease in the mean of 0.2 mm with the use of a tourniquet. CONCLUSION: Although the use of a tourniquet showed a detectable change in the lateral gap in four 10° segments of flexion, clinical relevance with an average difference of 0.2 mm is not achieved. Thus, the use of a tourniquet in TKA can still be advocated based on the presented data. LEVEL OF EVIDENCE: Level I.

Association between posterior tibial slope and anatomic spinopelvic parameters: a retrospective cross-sectional study.

PURPOSE: Only a few publications considered the influence of the spinopelvic parameters on below-hip anatomy. There is a lack of evidence about the relationship between the anatomic spinopelvic parameters and the posterior tibial slope (PTS). Therefore, the aim of this study was to analyze the association between fixed anatomic spinopelvic parameters and PTS. METHODS: Adult patients presenting with lumbar, thoracic, or cervical complaints together with knee pain at a single hospital between 2017 to 2022 with available standing full-spine lateral radiograph and lateral knee radiograph were retrospectively reviewed. The measured parameters included the pelvic incidence (PI), the sacral kyphosis (SK), the pelvisacral angle, the sacral anatomic orientation (SAO), the sacral table angle, the sacropelvic angle and the PTS. Pearson's correlations and linear regression analyses were conducted. RESULTS: A total of 80 patients (44 women), median age 63 years were analyzed. A strong positive correlation was identified between PI and PTS (r = 0.70, p < 0.001). A strong negative correlation was observed between PI and SAO (r = - 0.74, p < 0.001). A strong positive correlation was observed between PI and SK (r = 0.81, p < 0.001). A univariable linear regression analysis showed that PTS can be deduced from PI according to the following formula: PTS = 0.174 × PI - 1.138. CONCLUSION: This study is the first to support a positive correlation between the PI and the PTS. We demonstrate that knee anatomy is individually correlated to pelvic shape and therefore influences spinal posture.

Impact of hyaluronic acid injection on the knee joint friction.

PURPOSE: The purpose of this in vitro study was to investigate whether or not hyaluronic acid supplementation improves knee joint friction during osteoarthritis progression under gait-like loading conditions. METHODS: Twelve human cadaveric knee joints were equally divided into mild and moderate osteoarthritic groups. After initial conservative preparation, a passive pendulum setup was used to test the whole joints under gait-like conditions before and after hyaluronic acid supplementation. The friction-related damping properties given by the coefficient of friction µ and the damping coefficient c (in kg m2/s) were calculated from the decaying flexion-extension motion of the knee. Subsequently, tibial and femoral cartilage and meniscus samples were extracted from the joints and tested in an established dynamic pin-on-plate tribometer using synthetic synovial fluid followed by synthetic synovial fluid supplemented with hyaluronic acid as lubricant. Friction was quantified by calculating the coefficient of friction. RESULTS: In the pendulum tests, the moderate OA group indicated significantly lower c0 values (p < 0.05) under stance phase conditions and significantly lower µ0 (p = 0.01) values under swing phase conditions. No degeneration-related statistical differences were found for µend or cend. Friction was not significantly different (p > 0.05) with regard to mild and moderate osteoarthritis in the pin-on-plate tests. Additionally, hyaluronic acid did not affect friction in both, the pendulum (p > 0.05) and pin-on-plate friction tests (p > 0.05). CONCLUSION: The results of this in vitro study suggested that the friction of cadaveric knee joint tissues does not increase with progressing degeneration. Moreover, hyaluronic acid viscosupplementation does not lead to an initial decrease in knee joint friction.

Individual Phenotype Does Not Impact the Outcome of Mechanical Aligned Total Knee Arthroplasties for Valgus Osteoarthritis.

Background and Objectives: There is an ongoing discussion about the best alignment targets in total knee arthroplasty (TKA). Mechanical alignment has been the standard in TKA for years. Alongside the development of various classification systems to describe the native alignment of the knee (knee phenotype), kinematic alignment restoring the individual phenotype of the knee has been advocated more recently. Alignment in TKA becomes even more challenging in knees with preoperative deformities such as valgus osteoarthritis. Materials and Methods: The study retrospectively evaluated 158 knees in 135 patients who underwent TKA with a mechanical alignment target for valgus osteoarthritis. Pre- and postoperative hip knee angle, lateral distal femur angle, and medial proximal tibial angle/tibial plate angle (pre-/postoperative) were measured on standing hip-to-ankle radiographs. Knees were grouped according to the coronal plane alignment of the knee (CPAK) classification. Preoperative and postoperative range of motion and patient-related outcome measures (WOMAC, UCLA, SF-12, pain) were assessed. Results: There was no difference in outcome for mechanically aligned TKA between the different CPAK phenotypes, suggesting that mechanical alignment is an appropriate target for the different phenotypes analyzed in the study. Remaining valgus alignment was associated with decreased postoperative UCLA scores and decreased improvement in SF-12 scores (p = 0.011/p = 0.028). Within CPAK III, mechanical aligned TKA showed better postoperative UCLA Scores than TKA with valgus alignment (p = 0.015). The individual knee phenotype in patients with valgus osteoarthritis did not influence the outcome of mechanical aligned TKA operated with standardized soft-tissue release.

The epicondylar ratio can be reliably determined in both computed tomography and X-ray.

PURPOSE: One of the key factors to the successful revision of total knee arthroplasty (rTKA) is the reconstruction of the joint line, which can be determined using the epicondylar ratio (ER). The measurement is established in X-ray and MRI. However, it is not known whether computed tomography (CT) allows a more reliable determination. The objective was to assess the reliability of the ER in CT and to determine the correlation between the ER in CT and a.p. X-ray of the knee. METHODS: The ER was determined on X-ray and CT images of a consecutive series of 107 patients, who underwent rTKA. Measurements were made by two blinded observes, one measured twice. The inter- and intraobserver agreement, as well as the correlation between the two methods, were quantified with the Intraclass Correlation Coefficient. RESULTS: The average lateral ER was 0.32 (± 0.04) in X-ray and 0.32 (± 0.04) in CT. On the medial side, the average ER was 0.34 (± 0.04) in X-ray and 0.35 (± 0.04) in CT. The interobserver agreement for the same imaging modality was lateral 0.81 and medial 0.81 in X-ray as well as lateral 0.74 and medial 0.85 in CT. The correlation between the two methods was lateral 0.81 and medial 0.79. CONCLUSIONS: The ER can be reliably determined in X-ray and CT. Measurements of the two image modalities correlate. Prior to rTKA, the sole use of the X-ray is possible.

Editorial Commentary: Posterior Tibial Slope: The "Unknown Size" of the Knee Joint.

The posterior tibial slope (PTS) plays an immensely important role in almost every orthopaedic operation on the knee joint. The PTS is a decisive factor in the reconstruction of a torn anterior or posterior cruciate ligament, in high tibial osteotomy and, of course, in total knee arthroplasty. It is therefore all the more surprising that in current clinical practice relatively little emphasis is placed on the exact measurement of PTS. If the true value is not known, the influence of the same is pure coincidence. In the coronal plane, it is clinically valid practice to determine the hip-knee-ankle angle and thus to be able to determine the mechanical and anatomical axes at the tibia and femur. In the sagittal plane, however, an in-depth analysis is often dispensed with and only a short lateral knee radiograph is used. Different axes are described to determine the PTS. In addition, it is often overlooked that a determination of the PTS on lateral radiographs can only represent an average, since the medial and lateral tibial plateau shows considerable differences purely anatomically. In the future, we should place more emphasis on an analysis of the sagittal plane in the knee joint including PTS at least as profound as the analysis of the frontal plane. Here, radiographs of the entire lateral tibia must be requested to determine the true axis and thus the true PTS.

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.

Severity of valgus knee osteoarthritis has no effect on clinical outcomes after total knee arthroplasty.

INTRODUCTION: Advanced valgus osteoarthritis (OA) is one of the most challenging indications for total knee arthroplasty (TKA). There is no information in the literature about the optimal timing of surgery. The current study investigates the impact of the preoperative deformity and degree of arthritis on postoperative outcome after TKA. MATERIAL AND METHODS: The study evaluated 133 knees in 107 patients with valgus OA that failed nonoperative treatment with a minimum 2-year follow-up. Mechanical alignment, Kellgren and Lawrence (K/L) score, and minimal joint space width (minJSW) were measured on AP- and hip-to-ankle radiographs. All knees had advanced OA (i.e., K/L grades 3 or 4 and less than 50% minJSW). Pre- and postoperative WOMAC, VR-12, UCLA, VAS, ROM were recorded. RESULTS: There was no difference in clinical outcome (WOMAC, UCLA, VR-12, VAS or ROM) between patients with different degrees of valgus deformities (< 5.0 deg., 5.0-9.9 deg., 10.0-14.9 deg., ≥ 15.0 deg.). There was also no correlation between K/L score or minimal joint space width and any of the outcome parameters. CONCLUSIONS: The degree of valgus deformity and the grade of osteoarthritis do not predict the outcome of TKA in patients with valgus OA. Since the risk of complication and the need for implant constraint increases with increasing deformity and instability of the knee, surgery appears to be justified in patients with advanced OA that failed nonoperative treatment, regardless of the degree of deformity.

[Revision TKA due to instability: diagnostics, treatment options and outcomes]. / K-TEP-Wechsel bei Instabilität: Diagnostik, Therapie und Ergebnisse.

BACKGROUND: Instability after primary TKA is a frequent reason for revision surgery. Other mechanisms of failure must be ruled out before an in-depth analysis of instability. DIAGNOSTICS: Diagnostic tools for instability consist of medical history, clinical examination, and imaging. The clinical examination must focus primarily on the extent of the instability, the location of the instability and the levels of instability. Varus and valgus stress radiographs in the mediolateral plane in extension and flexion, as well as anteroposterior stress images (drawer) are mandatory. In addition, the underlying cause (or a combination of causes) must be defined. Possible causes include malalignment, component malposition (rotation), bony and ligamentous insufficiencies and implant-associated instabilities. THERAPY: Once the mechanism of failure is understood in detail, various therapeutic options are available. Conservative therapy is only considered in patients where there is borderline instability, and the patient has adequate compensatory options in daily life. Some authors postulate the need for 3 months of conservative therapy in every case before possible surgery. Isolated inlay exchange is usually only a compromise and shows failure rates of up to 60%. Partial component exchange requires some preconditions and is technically demanding. RESULTS: If the indication is correct, the results are consistently comparable with those after full component revision. In the case of full component revision, attention must be paid to the degree of constraint to achieve stability but also to avoiding over-treatment (too highly constrained TKA with an probability of loosening). In general, the results after revision surgery are worse in cases of instability than in cases of exchange surgery due to aseptic loosening or patellar abnormalities but better than in cases of infection or arthrofibrosis.

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.

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.

The posterior-anterior-flexed view is essential for the evaluation of valgus osteoarthritis. A prospective study on 134 valgus knees.

BACKGROUND: Radiographic imaging is an important tool to assess osteoarthritis (OA). Lateral compartment osteoarthritis (valgus OA) usually starts with cartilage degeneration along the posterior aspect of the lateral femoral condyle. There is evidence that the posterior-anterior (PA)-flexed view is more sensitive when diagnosing early stages of valgus OA compared to the anterior-posterior (AP) view. The current paper analyzes the value of the PA-flexed view for patients scheduled for total knee arthroplasty (TKA). METHODS: Radiographs of 134 valgus knees were assessed prior to TKA. The minimal joint space width (minJSW) was measured on AP and PA-flexed views. The extent of mechanical deformity was measured on hip to ankle standing films. RESULTS: 49 (36.6%) AP views showed Kellgren and Lawrence (K/L)-grade 4 osteoarthritis in the lateral compartment, 82 (63.4%) showed grade 3 or less. The PA-flexed view resulted in an increased K/L-grading to grade 4 for 53 knees (62.4%) that were considered grade 3 or less on standard AP-radiographs. There was a significant differences between lateral minJSW on AP and PA-flexed view for patients with up to 10 degrees of mechanical valgus deformity (p < 0.001), as well as 11 to 15 degrees of mechanical deformity (p = 0.021). Only knees with severe deformity of more than 15 degrees did not show a difference in minJSW between PA-flexed view and AP view (p = 0.345). CONCLUSIONS: The PA-flexed view is superior to the standard AP view in quantifying the extent of valgus OA in patients with zero to fifteen degrees of valgus deformity. It is recommended for the initial assessment of patients with valgus osteoarthritis and better documents the extent of osteoarthritis prior to TKA.

Salvage of a monoblock metal-on-metal cup using a dual mobility liner: a two-year MRI follow-up study.

PURPOSE: Revision of failed modular metal-on-metal total hip replacement (MoM-THA) can be technically difficult. A dual mobility liner can help to salvage a well-fixed acetabular component. The present paper reports the clinical and radiographic outcome of revision of failed Birmingham modular MoM-THA using a dual mobility liner. METHODS: The present study reports on ten patients (3 female and 7 male) with 11 revision THAs. Patients underwent revision an average of 51 months (range 40-73 months) after index procedure. Mean follow-up after the revision was 31 months (range 24-37 months) and all patients underwent an MRI with metal artifact reduction software (MARS) at least two years after revision to assess for local polyethylene wear and osteolysis. RESULTS: The Harris Hip score improved from 92.2 (range 63.0-100.0) to 100.0 (p = 0.072). One patient had a one-time dislocation within seven days of surgery. No patient required additional surgeries. Radiographs showed no signs of component loosening and osteolysis and MRI imaging revealed no evidence of polyethylene wear or osteolysis. CONCLUSION: A dual mobility liner in an existing Birmingham cup can provide excellent clinical and radiological short-term results without MRI evidence of increased polyethylene wear. Post-operative hip precautions should be enforced.

Predictive factors for metal ion levels in metal-on-metal total hip arthroplasty.

INTRODUCTION: Although metal-on-metal (MoM) total hip arthroplasty (THA) and hip resurfacings (HR) have similar bearing surfaces and comparable wear rates, metal ion levels and risk of failure are higher for MoM-THA. The mechanism behind the increased metal ion levels in large head MoM-THA is not completely understood. The current study aims to identify predictive factors for increased metal ion levels in unilateral and bilateral large head MoM-THA. MATERIALS AND METHODS: 99 Birmingham modular MoM-THA in 87 patients with metal ion levels at least 36 months after index procedure were analyzed. Mean follow-up time was 61.3 months (range 37-108) and the relationship of the following variables (gender, age, BMI, follow-up time, UCLA Activity Score, cup inclination, femoral head size, bilateral surgery) on metal ion levels were analyzed with multivariate regression models. RESULTS: Multivariate regression analysis revealed that bilateral MoM-THA surgery (p < 0.001) had a positive predictive effect on cobalt serum levels, while BMI had a negative (p = 0.018). Female gender (p = 0.012), activity (p = 0.001) and bilateral MoM-THA (p = 0.004) were positively correlated with chromium levels. Positive independent predictors for the cobalt-chromium ratio in the multivariate analysis were overall follow-up time (p = 0.004), bilateral MoM-THA (p < 0.001) and femoral head size (p = 0.007). CONCLUSIONS: The data of the current study suggest that bilateral MoM-THA, increased patient activity levels and female gender are associated with increased chromium levels. Patients with larger component size, longer follow-up time and bilateral MoM-THAs have an increased cobalt-chromium ratio. These patients might be at increased risk for adverse local soft tissue reactions secondary to corrosion. Continuous close monitoring is recommended and bearing-surface change should be discussed if local tissue reactions occur.

Lateral-compartment Osteophytes are not Associated With Lateral-compartment Cartilage Degeneration in Arthritic Varus Knees.

BACKGROUND: Progression of arthritis in the lateral compartment is one of the main failure modes of unicompartmental knee arthroplasty (UKA). The decision regarding whether to perform a medial UKA sometimes is made based on whether lateral-compartment osteophytes are visible on plain radiographs obtained before surgery, but it is not clear whether the presence of lateral-compartment osteophytes signifies that the cartilage in the lateral compartment is arthritic. QUESTIONS/PURPOSES: (1) Is the presence of lateral compartment osteophytes associated with biomechanical properties of lateral-compartment cartilage, and (2) are osteophytes in the lateral compartment associated with particular histologic features of cartilage in the lateral compartment? METHODS: Between May 2010 and January 2012, we performed 201 TKAs for varus osteoarthritis confirmed on standardized AP hip-to-ankle standing radiographs. All patients with a varus deformity were considered for this prospective study. During the enrollment period, 100 patients (101 knees) were not enrolled for this study because of declined consent or because they were unable to perform all required preoperative radiographic examinations. That left 84 patients (100 knees), of whom an additional 23 patients (27%) were excluded because either radiographic or biomechanical data were missing. For final analysis, 61 patients (71 knees) were available. There were 29 males (48%) and 32 females (52%) with a mean age of 65 years (range, 49-89 years). Their mean BMI was 26 kg/m2 (range, 17-47 kg/m2). Lateral-compartment osteophytes were graded by two observers on AP standing knee radiographs based on a template of the Osteoarthritis Research Society International (OARSI) radiographic atlas. During surgery, osteochondral plugs were harvested from the lateral tibial plateau and the distal lateral femur for biomechanical and histologic assessments. The intrinsic material coefficients aggregate modulus (Ha) and dynamic modulus (DM) were determined by applying a compressive load of 20 g for 1 hour. The histologic analysis was performed according to the qualitative osteoarthritis cartilage histopathology assessment system. The Mann-Whitney U test was performed to compare the distribution of variables. Power analysis was performed for the Mann-Whitney U test using an alpha of 0.05, a power of 80%, and a sample size of 71 resulting in a detectable effect size of 0.6. Owing to the limited sample size, only medium or large effects in changes of biomechanical properties can be excluded with adequate power. RESULTS: Ha and DM were not different with the numbers available when comparing knees with osteophyte Grades 0, 1, and 2 on the lateral tibia. For Grade 3 tibial osteophytes (n = 3), the lateral tibia cartilage showed low Ha (0.39 MPa; SD, 0.17 MPa) and low DM (2.85 MPa; SD, 2.12 MPa). On the lateral femur, no differences of Ha and DM were observed with the numbers available between Grades 0 to 3 osteophytes. No differences with the numbers available in the OARSI histologic grades on the lateral tibia plateau and the distal lateral femur were observed between the different osteophyte grades. CONCLUSIONS: Lateral-compartment osteophytes are not associated with biomechanically weaker cartilage or with more-advanced histologic signs of degeneration of lateral-compartment cartilage in knees with varus arthritis. Given the small sample size of 71, the study was underpowered to detect small-to-modest decreases in biomechanical properties. Future studies with larger sample sizes are needed to confirm the current findings. CLINICAL RELEVANCE: Factors other than the presence or absence of lateral-compartment osteophytes should be considered when evaluating patients with medial-compartment arthritis for medial UKA. Future studies are required to define the limitations of plain radiographs to rule out cartilage degeneration in the lateral compartment of varus knees.

Topical Tranexamic Acid is Equivalent to Targeted Preoperative Autologous Blood Donation in Total Hip Arthroplasty.

BACKGROUND: Topical tranexamic acid (TXA) was introduced to replace the previous targeted preoperative autologous blood donation (PABD) program. This study aims to analyze the efficacy of topical TXA compared with targeted PABD in anemic patients undergoing primary total hip arthroplasty (THA). METHODS: Two thousand two hundred fifty-one patients underwent primary THA between 2009 and 2013 using targeted autologous blood donation for 280 anemic patients (12%; Hb <12.5 g/dL). One thousand nine hundred seventy-one nonanemic patients (88%; ≥12.5 Hb/dL) received no blood management intervention. Starting in 2014, 505 consecutive patients were operated using 3 grams of topical TXA and abandoning PABD. Ninety-one patients (18%) were anemic and 414 (82%) nonanemic. RESULTS: The utilization of topical TXA in anemic patients resulted in higher hemoglobin levels on the first postoperative day (P = .014), but not on the second postoperative day (P = .198) compared with PABD. There was no difference in allogeneic transfusion rates between both groups: 12% vs 13% (P = .848). In the nonanemic group, TXA significantly increased hemoglobin levels on the first postoperative day (P = .001) as well as on the second postoperative day (P < .001), and resulted in a reduction in allogeneic transfusion rates from 8% to 1%. CONCLUSION: The present study suggests that topical TXA is equivalent to PABD in anemic patients and reduces transfusion rates and increases Hb-levels in nonanemic patients.

The Accuracy of Acetabular Component Position Using a Novel Method to Determine Anteversion.

BACKGROUND: This study compares the differences in acetabular component position, leg length discrepancy, and hip offset between the anterior and posterior approach. A novel method is applied to determine the acetabular anteversion using the C-arm tilt angle for the anterior approach. METHODS: Hundred consecutive anterior total hip arthroplasties were matched according to gender, body mass index, and age to a cohort of 100 primary total hip arthroplasties operated on through a posterior approach. Postoperative radiographs were analyzed to determine cup inclination, cup anteversion, leg length discrepancy, and hip offset. RESULTS: The mean inclination was 40.8° (range 33°-48°) and 45.1° (range 33°-55°) for the anterior and posterior approach, respectively. Using the new C-arm tilt plane technique, an average acetabular anteversion of 18.4° (range 11°-26°) was achieved with the anterior approach compared with 23.6° (range 8°-38°) with the posterior approach. Hundred percent cups in the anterior group and 81% in the posterior group fell within the safe zone (P < .001). There was no difference in the overall hip offset between the operated side and the contralateral side for the anterior (P = .074) and posterior (P = .919) group. There was no difference in leg length discrepancy between the 2 approaches (P = .259). CONCLUSION: Intraoperative fluoroscopy-assisted direct anterior approach was associated with improved acetabular component positioning. However, no benefit was shown with regards to restoration of hip offset or leg length.