ESR essentials: MRI of the knee-practice recommendations by ESSR.

Many studies and systematic reviews have been published about MRI of the knee and its structures, discussing detailed anatomy, imaging findings, and correlations between imaging and clinical findings. This paper includes evidence-based recommendations for a general radiologist regarding choice of imaging sequences and reporting basic MRI examinations of the knee. We recommend using clinicians' terminology when it is applicable to the imaging findings, for example, when reporting meniscal, ligament and tendon, or cartilage pathology. The intent is to standardise reporting language and to make reports less equivocal. The aim of the paper is to improve the usefulness of the MRI report by understanding the strengths and limitations of the MRI exam with regard to clinical correlation. We hope the implementation of these recommendations into radiological practice will increase diagnostic accuracy and consistency by avoiding pitfalls and reducing overcalling of pathology on MRI of the knee. CLINICAL RELEVANCE STATEMENT: The recommendations presented here are meant to aid general radiologists in planning and assessing studies to evaluate acute and chronic knee findings by advocating the use of unequivocal terminology and discussing the strengths and limitations of MRI examination of the knee. KEY POINTS: • On MRI, the knee should be examined and assessed in three orthogonal imaging planes. • The basic general protocol must yield T2-weighted fluid-sensitive and T1-weighted images. • The radiological assessment should include evaluation of ligamentous structures, cartilage, bony structures and bone marrow, soft tissues, bursae, alignment, and incidental findings.

Pediatric Anterior Cruciate Ligament Reconstruction.

The incidence of anterior cruciate ligament (ACL) injuries in children and adolescents has been growing recently. This problem is a challenge for the treating orthopedic surgeon, especially when the patient is in the prepubertal period with a high growth potential. Since reconstructive procedures require interventions close to active growth plates, they are associated with the risk of postoperative limb length discrepancies and limb deformities. Postponing ACL reconstruction until the end of growth is not a solution, as persistent knee instability increases the risk of secondary intra-articular damage. The key to success is not only knowledge of the anatomy and biomechanics of the pediatric knee but also the ability to predict the remaining growth potential and familiarity with a wide range of reconstructive surgical procedures available for patients at different ages.

Current strategies for enhancement of the bioactivity of artificial ligaments: A mini-review.

Background and objective: Anterior cruciate ligament (ACL) reconstruction calls for artificial ligaments with better bioactivity, however systematic reviews regarding bioactivity enhancement strategies, technologies, and perspectives of artificial ligaments have been rarely found. Methods: Research papers, reviews, and clinical reports related to artificial ligaments were searched and summarized the current status and research trends of artificial ligaments through a systematic analysis. Results: Having experienced ups and downs since the very first record of clinical application, artificial ligaments differing in material, and fabrication methods have been reported with different clinical performances. Various manufacturing technologies have developed and realized scaffold- and cell-based strategies. Despite encouraging in-vivo and in-vitro test results, the clinical results of such new designs need further clinical examinations. Conclusion: As the demand for ACL reconstruction dramatically increases, novel artificial ligaments with better osteoinductivity and mechanical performance are promising. The translational potential of this article: To develop novel artificial ligaments simultaneously possessing excellent osteoinductivity and satisfactory mechanical performance, it is important to grab a glance at recent research advances. This systematic analysis provides researchers and clinicians with comprehensive and comparable information on artificial ligaments, thus being of clinical translational significance.

Morphometry of Anterior Cruciate Ligament in Knee joint. A Cadaveric Study.

Objectives: The journey of Anterior Cruciate Ligament (ACL) reconstruction surgery has long way from open surgery to arthroscopy. Therefore, the anatomical features of the ACL and its two bundles description rewarded as good outcome of procedure. Material and methods: Fifty fresh knees were dissected. The insertion position, length and diameter of ACL and patellar tendon length were measured and determines the range of normality according to sex and side. Results: The average lengths of Antero- medial (AM) and postero- lateral (PL) bundle of the ACL were 35.35 mm and 26.11mm in male on right side, respectively while 34.21mm and 25.53 mm in female. Patellar tendon length was 45.24 mm in right side of male and 43.38 mm in female obtained. The average lengths of AM and PL bundle of the ACL were 35.47 mm and 26.04 mm in male on left side, respectively while 34.23 mm and 25.38 mm in female. Conclusion: The length of ligaments was higher in male than female. There was strong correlation between height and length of ligaments but no correlation with age.

Age-related changes in microRNAs expression in cruciate ligaments of wild-stock house mice.

Cruciate ligaments (CL) of the knee joint are injured following trauma or aging. MicroRNAs (miRs) are potential therapeutic targets in musculoskeletal disorders, but there is little known about the role of miRs and their expression ligaments during aging. This study aimed to (1) identify if mice with normal physical activity, wild-stock house mice are an appropriate model to study age-related changes in the knee joint and (2) investigate the expression of miRs in aging murine cruciate ligaments. Knee joints were collected from 6 and 24 months old C57BL/6 and wild-stock house mice (Mus musculus domesticus) for ligament and cartilage (OARSI) histological analysis. Expression of miR targets in CLs was determined in 6-, 12-, 24-, and 30-month-old wild-stock house mice, followed by the analysis of predicted mRNA target genes and Ingenuity Pathway Analysis. Higher CL and knee OARSI histological scores were found in 24-month-old wild-stock house mice compared with 6- and 24-month-old C57BL/6 and 6-month-old wild-stock house mice (p < 0.05). miR-29a and miR-34a were upregulated in 30-month-old wild-stock house mice in comparison with 6-, 12-, and 24-month-old wild-stock house mice (p < 0.05). Ingenuity Pathway Analysis on miR-29a and 34a targets was associated with inflammation through interleukins, TGFß and Notch genes, and p53 signaling. Collagen type I alpha 1 chain (COL1A1) correlated negatively with both miR-29a (r = -0.35) and miR-34a (r = -0.33). The findings of this study support wild-stock house mice as an appropriate aging model for the murine knee joint. This study also indicated that miR-29a and miR-34a may be potential regulators of COL1A1 gene expression in murine CLs.

Outcomes of Bi-unicompartmental Versus Total Knee Arthroplasty for the Treatment of Medial and Lateral Knee Osteoarthritis: A Systematic Review and Meta-analysis of Comparative Studies.

Purpose: The aim of this meta-analysis was to evaluate differences in functional outcomes between simultaneous bi-unicompartmental knee arthroplasty (Bi-UKA) and total knee arthroplasty (TKA) for the treatment of medial and lateral knee osteoarthritis. Material and Methods: According to the PRISMA statement, a comprehensive search was conducted to identify studies reporting comparative results of the Bi-UKA versus the TKA. Of 953 titles, 6 studies met the inclusion criteria. Results: A total of 286 patients were identified, of which 137 underwent Bi-UKA and 149 TKA. TKA reported a mean hip-knee-ankle (HKA) angle of 179.4 ± 2.4 compared to that in Bi-UKA measuring 177.2 ± 2.7 (p = 0.0001, 95% CI - 3.02 to - 1.38). No difference was found in the Western Ontario and McMaster Universities (WOMAC) pain (4 ± 1.6 and 4.2 ± 1.3 for Bi-UKA and TKA, respectively; p = 0.4996, 95% CI - 0.86 to 0.43). Bi-UKA was favorable in terms of WOMAC function (7.5 ± 1.9 and 9 ± 1.9 for Bi-UKA and TKA, respectively; p = 0.001, 95% CI - 2.29 to - 0.61) and WOMAC stiffness (1.6 ± 1 and 2.4 ± 0.7 for Bi-UKA and TKA, respectively; p = 0.0001, 95% CI - 1.18 to - 0.42). Bi-UKA showed a better Knee Society Score (KSS) in comparison to TKA (79.7 ± 7.8 and 75.4 ± 10.5 for Bi-UKA and TKA, respectively; p = 0.0021, 95% CI 1.58-7.02). The differences in postoperative outcomes scores between Bi-UKA and TKA were lower than their respective minimum clinically important differences. Conclusions: When Bi-UKA and TKA are compared for the treatment of medial and lateral knee osteoarthritis, Bi-UKA are favorable in terms of WOMAC and KSS even though these values are lower than the minimum clinically important differences; moreover, similar postoperative hip-knee-ankle angle can be expected 3 years after Bi-UKA and TKA.

Outcomes of Repair and Reconstruction of the Acute Posterolateral Corner Injuries of the Knee Combined with Cruciate Ligaments Injuries.

Background: This study aimed to report objective and subjective knee stability scores for patients who underwent acute repair of avulsed posterolateral corner (PLC) structures or acute reconstruction of midsubstance tears combined with delayed reconstruction of cruciate ligaments. Methods: A total of 48 sport and vehicle accident traumatic patients were enrolled in a three-year follow-up study. The patients were investigated by clinical exams, subjective and objective International Knee Documentation Committee (IKDC) score, Tegner score, Lysholm score, and stress imaging. All scores were compared between the reconstruction and repair groups. Results: Subjective IKDC scores were obtained at 83.3±9.6 and 88.3±4.39 for the reconstruction and repair groups, respectively. Only two patients in the reconstruction group had abnormal objective IKDC scores. Based on the Tegner score, 15 out of 18 patients in the repair group and 20 out of 24 patients in the reconstruction group regained their pre-injury functional level. Mean Lysholm scores for the reconstruction and repair groups were estimated at 83.4±8.2 and 88.2±4.1, respectively. Mean lateral joint opening differences between two knees in the reconstruction and repair groups were -0.2±0.1mm and 0.5±0.1mm, respectively. There were no statistically significant differences between groups outcomes. We had no failure of treatment at the final follow-up. Conclusion: Acute intervention within 3 weeks after PLC injuries combined with delayed cruciate ligaments reconstructions showed favorable outcomes. Both repair and reconstruction are effective when deciding based on the type of injury (i.e., avulsion and midsubstance tear).

Knee joint laxity is restored in a bi-cruciate retaining TKA-design.

PURPOSE: The goal is to evaluate the passive stability of a bicruciate retaining, cruciate retaining and bicruciate substituting TKA design in relation to the native knee stability in terms of the laxity envelope. A bicruciate retaining knee prosthesis was hypothesized to offer a closer to normal knee stability in vitro. METHODS: Fourteen cadaveric knee specimens have been tested under passive conditions with and without external loads, involving a varus/valgus and an external/internal rotational torque, distraction/compression force and an anteroposterior shear force. Subsequently, the native knee, bicruciate retaining, cruciate retaining and finally a bicruciate substituting total knee arthroplasty were tested. RESULTS: Through the range of motion, the width of the varus/valgus and internal/external laxity envelope for the native knee and the bicruciate retaining knee were almost equivalent, whereas the cruciate retaining and the bicruciate substituting knee displayed less laxity and more joint distraction. In all prosthetic knees, an equal anteroposterior laxity was seen for the lateral and medial side whereas in the native knee, a difference in laxity was seen between the stable medial side and the more mobile lateral side. CONCLUSION: Bicruciate retaining knee prostheses can restore normal laxity and thus have the potential to offer more normal knee function. Restoration of natural peri-articular soft-tissue tension is clinically important because of its obvious effects on joint stability and range of motion. Furthermore, the results of this study could help to establish the ideal ligament tension and laxity in more conventional implants by approaching the normal values for passive knee evaluation as presented here.

Anatomical feature of knee joint in Aachen minipig as a novel miniature pig line for experimental research in orthopaedics.

BACKGROUND: The pig is a commonly used large animal model, since pigs share anatomical and physiological similarities with humans. In contrast to other experimental pig lines the Aachen minipig, as a robust novel minipig does not require housing with any barrier. To estimate transferability of results to human conditions, pig lines should be thoroughly characterized. PURPOSE: Therefore, we analyzed the anatomical pecularities of the knee joint of the novel "Aachen minipig" line raised for experimental conditions. METHODS: Eight knee joints of four adult Aachen minipigs were dissected measuring the dimensions of typical landmarks using a digital caliper. Hybrid pig and human knee joints served as controls. Cartilage of the Aachen minipig (trochlear groove, femoral condyles, menisci) were assessed histologically. RESULTS: The Aachen minipig shared its knee joint anatomy with the hybrid pig. In comparison to humans, peculiarities of the pig were demonstrated in the Aachen minipig: the lateral meniscus and the lateral tibial joint surface were significantly longer than the medial counterparts. The fibular head was covered by fibrocartilage and completely integrated into the lateral lower joint surface. The cartilage at the joint areas usually used for cartilage repair studies was in average 0.66±0.04mm thick. The porcine anterior cruciate ligament (ACL) attached with two bundles at the anterior tibial plateau separated from each other by the lateral anterior meniscotibial ligament. Aachen minipig articular and meniscal cartilage presented the typical histoarchitecture. CONCLUSIONS: The Aachen minipig reflects porcine anatomical peculiarities, which should be considered, especially for meniscus and ACL reconstruction.

Viscoelastic characteristics of the canine cranial cruciate ligament complex at slow strain rates.

Ligaments including the cruciate ligaments support and transfer loads between bones applied to the knee joint organ. The functions of these ligaments can get compromised due to changes to their viscoelastic material properties. Currently there are discrepancies in the literature on the viscoelastic characteristics of knee ligaments which are thought to be due to tissue variability and different testing protocols. The aim of this study was to characterise the viscoelastic properties of healthy cranial cruciate ligaments (CCLs), from the canine knee (stifle) joint, with a focus on the toe region of the stress-strain properties where any alterations in the extracellular matrix which would affect viscoelastic properties would be seen. Six paired CCLs, from skeletally mature and disease-free Staffordshire bull terrier stifle joints were retrieved as a femur-CCL-tibia complex and mechanically tested under uniaxial cyclic loading up to 10 N at three strain rates, namely 0.1%, 1% and 10%/min, to assess the viscoelastic property of strain rate dependency. The effect of strain history was also investigated by subjecting contralateral CCLs to an ascending (0.1%, 1% and 10%/min) or descending (10%, 1% and 0.1%/min) strain rate protocol. The differences between strain rates were not statistically significant. However, hysteresis and recovery of ligament lengths showed some dependency on strain rate. Only hysteresis was affected by the test protocol and lower strain rates resulted in higher hysteresis and lower recovery. These findings could be explained by the slow process of uncrimping of collagen fibres and the contribution of proteoglycans in the ligament extracellular matrix to intra-fibrillar gliding, which results in more tissue elongations and higher energy dissipation. This study further expands our understanding of canine CCL behaviour, providing data for material models of femur-CCL-tibia complexes, and demonstrating the challenges for engineering complex biomaterials such as knee joint ligaments.

Knee Forces During Landing in Men and Women.

Sex differences in biomechanics may provide one explanation for the greater incidence of knee injuries in women, but few studies have compared internal forces. In this study, a musculoskeletal model was used to compare male and female, bilateral and unilateral landings based on motion capture and force plate data. Participants were classified as landing medially or laterally loaded based upon the mediolateral load share at the knee (bilateral: p < 0.001, η2=0.452; unilateral: p < 0.001, η2 = 0.444). Knee kinematics and ground reaction forces were not different between the two groups (p > 0.05, η2 = 0.001 - 0.059), but there were differences in muscular recruitment. Landing strategy did not appear to be dependent on sex. However, for both medially and laterally loaded bilateral landings men had greater gluteal (p = 0.017, η2 = 0.085) and hamstrings forces (p < 0.001, η2 = 0.183), whereas women had greater quadriceps forces (p = 0.004, η2 = 0.116). This study demonstrates an association between muscular recruitment and medially loaded landings. Landing strategy seems to be a function of skill not sex; however, within a particular landing strategy there may be sex differences in muscular activation that contribute to the difference in injury rates.

Role of Magnetic Resonance Imaging in Classifying Individuals Who Will Develop Accelerated Radiographic Knee Osteoarthritis.

We assessed whether adding magnetic resonance (MR)-based features to a base model of clinically accessible participant characteristics (i.e., serological, radiographic, demographic, symptoms, and physical function) improved classification of adults who developed accelerated radiographic knee osteoarthritis (AKOA) or not over the subsequent 4 years. We conducted a case-control study using radiographs from baseline and the first four annual visits of the osteoarthritis initiative to define groups. Eligible individuals had no radiographic KOA in either knee at baseline (Kellgren-Lawrence [KL] grade <2). We classified two groups matched on sex (i) AKOA: at least one knee developed advanced-stage KOA (KL = 3 or 4) within 48 months and (ii) did not develop AKOA within 48 months. The MR-based features were assessments of bone, effusion/synovitis, tendons, ligaments, cartilage, and menisci. All characteristics and MR-based features were from the baseline visit. Classification and regression tree analyses were performed to determine classification rules and identify statistically important variables. The CART models with and without MR features each explained approximately 40% of the variability. Adding MR-based features to the model yielded modest improvements in specificity (0.90 vs. 0.82) but lower sensitivity (0.62 vs. 0.70) than the base model. There was consistent evidence that serum glucose, effusion-synovitis volume, and cruciate ligament degeneration are statistically important variables in classifying individuals who will develop AKOA. We found common MR-based measures failed to dramatically improve classification. These findings also show a complex interplay among participant characteristics and a need to identify novel characteristics to improve classification. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2420-2428, 2019.

Hip and knee kinematics of the forward lunge one year after unicondylar and total knee arthroplasty.

Patients with unicondylar knee arthroplasty (UKA) report higher functionality compared to those with total knee arthroplasty (TKA). However, these patients should also be assessed during more demanding tasks in order to appreciate their true functionality. The forward lunge (FL) is a motor task commonly used in clinics to evaluate functional recovery after knee replacement surgery. Unfortunately, clear evidence comparing FL kinematics between patients with UKA and TKA is still missing. The purpose of this study was to compare hip and knee joint kinematics during the FL between patients with UKA, TKA and controls. Twenty subjects (8 TKA, 6 UKA, 6 controls) underwent 3D motion analysis during a FL. Differences in hip and knee kinematics between groups were identified using statistical parametric mapping. We concluded that patients with TKA demonstrated reduced knee and hip flexion angles during the loaded phase of the FL, which could have been an attempt to unload the knee joint. This is in contrast to patients with UKA, who showed similar knee and hip joint kinematics compared to controls throughout the entire FL. It seems that retaining the cruciate ligaments is beneficial for the execution of a complex motor task such as the FL.

Osteoarthritis of the Anterior Cruciate Ligament and Medial Tibial Plateau: A Cadaveric Study.

The objective of this study was to analyze morphometric anatomy and damages with aging in cadaveric knee specimens specific to the cruciate ligaments, the articular cartilage of the tibial plateau, and the menisci. Morphometric analyses to cadaveric anatomy of the knee were performed using Image-Pro® software on 3 age populations: <70 years old, 70 to 79 years old, and ≥80 years old. An average thickness of the cruciate ligaments was assessed with 5 circumferential measurements per specimen using nylon thread. Percent degeneration of the tibial plateau's articular cartilage and coverage by menisci was assessed with surface area measurements. The articular cartilage of the medial tibial plateau in ≥80 years old specimens showed a 1.7-fold increase in surface area degeneration (mm2) compared to 70 to 79 years old specimens ( P < 0.05). The medial meniscus also experienced degenerative changes with aging, which were expressed as decreases in tibial plateau coverage. The anterior cruciate ligament (ACL) experienced substantial degenerative thinning with aging. The 70 to 79 years old specimens had a 1.2-fold (10.5%) decrease in average ACL circumference (mm) compared to the <70 years old specimens ( P < 0.001). The ≥80 years old specimens had a 1.24-fold (19%) decrease in ACL circumference compared to the <70 years old specimens ( P < 0.001). ACL thinning during aging may be leading to substantial articular cartilage and menisci degeneration given the cruciate ligaments are a primary restraint that combats shearing forces at the knee joint.

High field magnetic resonance imaging is comparable with gross anatomy for description of the normal appearance of soft tissues in the equine stifle.

High field magnetic resonance imaging (MRI) is increasingly used for horses with suspected stifle disease, however there is limited available information on normal imaging anatomy and potential incidental findings. The aim of this prospective, anatomic study was to develop an optimized high field MRI protocol for evaluation of the equine stifle and provide detailed descriptions of the normal MRI appearance of the stifle soft tissues, using ultrasound and gross pathological examination as comparison tests. Nine cadaver limbs were acquired from clinically normal horses. Stifles were evaluated ultrasonographically and then by an extensive 1.5 T MRI protocol. Subsequently, all stifles were evaluated for gross pathologic change. Findings were compared between gross evaluation and MRI imaging and described. No soft tissue structure abnormalities were identified on any evaluation. Specific descriptive findings of the meniscotibial, meniscofemoral, collateral, patellar and cruciate ligaments, and the menisci were reported. The high field MRI protocol described in this study provided high spatial and contrast resolution of the soft tissue structures, and this in turn allowed visualization of detailed structural characteristics, such as striations and variations in signal intensity. Findings supported the use of high field MRI as a modality for the evaluation of the soft tissues of the equine stifle. As clinical availability of this modality increases in the future, authors anticipate that new stifle diseases will be detected that have not previously been identified with other imaging modalities.

Morphology of Intra-articular Structures and Histology of Menisci of Knee Joint.

INTRODUCTION: Menisci and cruciate ligaments are intra-articular structures of knee, and injury to these structures is common. Morphometric data gained in the study will help in analyzing the variations among humans and correlating it with the possibility, location, and type of injuries as well as better interpretation of structures during magnetic resonance imaging and arthroscopy which will further help in reconstructive surgeries of knee. MATERIALS AND METHODS: Width and thickness of the medial menisci (MM), lateral menisci (LM), and maximum length and width of anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) were taken on twenty knees. Histological examination of menisci was done. RESULTS: Width of MM was 0.601-0.700 cm at anterior horn (AH) in 45% of cases, 1.000-1.500 cm at posterior horn (PH) in 60% of cases, and 1.000-1.500 cm at body in 30% of cases. Thickness of MM at AH (45%) and PH (40%) was 0.401-0.500 cm and at body (35%) was 0.501-0.600 cm. Width of LM at AH (35%) was 0.801-0.900 cm, at PH (45%) was 0.901-1.000 cm, and at body (35%) was 1.000-1.500 cm. Thickness of LM at AH (45%) was 0.301-0.400 cm, at PH (50%) was 0.401-0.500 cm, and at body (40%) was 0.601-0.700 cm. Length of ACL in maximum percentage of specimens (55%) was 3.01-3.50 cm. Width of ACL in 25% specimens were 0.801-0.900 cm and in another 25% specimens were 1.001-1.500 cm. Length of PCL in maximum percentage of specimens ( 50 %) was 3.51-4.00 cm. Width of PCL in 80 % of specimens was 1.001-1.500 cm. Histological examination of menisci showed fibrocartilage (outer two-thirds) and hyaline cartilage (inner one-third). Orientation of fibers was circumferential with intermingled radial fibers. Fibroblasts, chondrocytes, and unclassified cells were arranged as single, paired, or in rows along the direction of fibers except in hyalinized part. Blood vessels were present toward the peripheral part. CONCLUSIONS: The maximum width of MM was at PH and for LM it was at the body. Maximum thickness was at the body for MM as well as LM. Width of PCL was more as compared to ACL.

Knee MLI Injuries: Common Problems and Solutions.

The multiple ligament injured knee presents a challenge with regard to management and treatment. Immediate management of the acute injury requires special attention and thorough examination because knee dislocations have been associated with significant complications. Treatment options range from closed reduction and immobilization to surgical repair and/or reconstruction of the injured ligaments. This article focuses on complications that may result from surgical treatments of the multiple ligament injured knee and ways of prevention. These complications include vascular and neurologic complications, venous thromboembolic events, arthrofibrosis, compartment syndrome, wound problems, heterotopic ossification, fractures and avascular necrosis, tunnels positioning complications, and malalignment.

The use of synthetic ligaments in the design of an enhanced stability total knee joint replacement.

Current total knee replacement designs work to address clinically desired knee stability and range of motion through a balance of retained anatomy and added implant geometry. However, simplified implant geometries such as bearing surfaces, posts, and cams are often used to replace complex ligamentous constraints that are sacrificed during most total knee replacement procedures. This article evaluates a novel total knee replacement design that incorporates synthetic ligaments to enhance the stability of the total knee replacement system. It was hypothesized that by incorporating artificial cruciate ligaments into a total knee replacement design at specific locations and lengths, the stability of the total knee replacement could be significantly altered while maintaining active ranges of motion. The ligament attachment mechanisms used in the design were evaluated using a tensile test, and determined to have a safety factor of three with respect to expected ligamentous loading in vivo. Following initial computational modeling of possible ligament orientations, a physical prototype was constructed to verify the function of the design by performing anterior/posterior drawer tests under physiologic load. Synthetic ligament configurations were found to increase total knee replacement stability up to 94% compared to the no-ligament case, while maintaining total knee replacement flexion range of motion between 0° and 120°, indicating that a total knee replacement that incorporates synthetic ligaments with calibrated location and lengths should be able to significantly enhance and control the kinematic performance of a total knee replacement system.

In Vivo Kinematic Comparison of a Bicruciate Stabilized Total Knee Arthroplasty and the Normal Knee Using Fluoroscopy.

BACKGROUND: The bicruciate stabilized (BCS) total knee arthroplasty (TKA) features asymmetrical bearing geometry and dual substitution for the anterior cruciate ligament and posterior cruciate ligament (PCL). Previous TKA designs have not fully replicated normal knee motion, and they are characterized by lower magnitudes of overall rollback and axial rotation than the normal knee. METHODS: In vivo kinematics were derived for 10 normal knees and 40-second generation BCS TKAs all implanted by a single surgeon. Mobile fluoroscopy and three-dimensional-to-two-dimensional registration was used to analyze anterior-posterior motion of the femoral condyles and femorotibial axial rotation during weight-bearing flexion. Statistical analysis was conducted at the 95% confidence level. RESULTS: From 0° to 30° of knee flexion, the BCS subjects exhibited similar patterns of femoral rollback and axial rotation compared to normal knee subjects. From 30° to 60° of knee flexion, BCS subjects experienced negligible anterior-posterior motions and axial rotation while normal knees continued to rollback and externally rotate. Between 60° and 90° the BCS resumed posterior motion and, after 90°, axial rotation increased in a normal-like fashion. CONCLUSION: Similarities in early flexion kinematics suggest that the anterior cam-post is supporting normal-like anterior-posterior motion in the BCS subjects. Likewise, lateral femoral rollback and external rotation of the femur in later flexion provides evidence for appropriate substitution of the PCL via the posterior cam-post. Being discrete in nature, the dual cam-post mechanism does not lend itself to adequate substitution of the cruciate ligaments in mid-flexion during which anterior cruciate ligament tension is decreasing and PCL tension is increasing in the normal knee.

Influência do posicionamento radiográfico no cálculo interobservador do ângulo do platô tibial em cães / Influence of radiographic positioning in the interobserver measuring of the tibial plateau angle in dogs

O objetivo deste trabalho foi demonstrar que o posicionamento radiográfico inadequado do membro pélvico de cães (imagens obliquadas) afeta a mensuração do ângulo do platô tibial (APT), levando à maior variação entre observadores. Foram realizadas duas projeções radiográficas nos membros pélvicos direito e esquerdo, uma em perfil verdadeiro e a outra com o membro obliquado em 21 cães provenientes do atendimento clínico cirúrgico do Hospital Veterinário da Universidade de Cuiabá, em Cuiabá-MT. Os critérios de inclusão foram cães livres de histórico ou afecção ortopédica nos membros pélvicos, pesando entre 15 e 40 quilos, sem predileção por raça ou sexo, entre dois e sete anos de idade. Foram obtidas 42 imagens radiográficas em perfil verdadeiro e 42 imagens radiográficas obliquadas. Três observadores com experiência em cálculo do APT fizeram as mensurações. Nos cálculos das imagens em perfil verdadeiro, o observador 1 obteve uma média de 23,35º ± 2,82; o observador 2, média de 23,88º ± 4,83; e o observador 3, média de 24,54º ± 4,01, não sendo encontrada diferença significativa entre o cálculo dos três avaliadores, P=0,944 (P > 0,05), nas imagens em perfil verdadeiro. Nos cálculos das imagens obliquadas, o observador 1 obteve uma média de 21,69º ± 4,22; o observador 2, média de 19,42º ± 5,92; e o observador 3, média de 22,64º ± 5,23, e foi encontrada diferença significativa entre o cálculo dos três observadores, P=0,016 (P < 0,05). Com esses dados, pôde-se demonstrar que a imagem radiográfica obliquada compromete o valor final do cálculo do ângulo do platô tibial em cães, levando à variação numérica estatisticamente significativa entre observadores. Conclui-se, assim, que um posicionamento correto do membro pélvico, em perfil verdadeiro, deve ser sempre utilizado para a obtenção de imagens, com o objetivo de mensurar o valor do APT.(AU)

This work aimed at demonstrating that an inadequate radiographic position of pelvic limbs of dogs, from a strict lateral radiographic view, resulted in oblique images, affecting the measurement of the tibial plateau angle (TPA). There were two radiographic projections of the right and the left pelvic limb, one in strict lateral radiographic view and another with inclined hind limb in 21 dogs from the clinical surgical assistance at Hospital Veterinário of Universidade de Cuiabá in Cuiabá-MT. Inclusion criteria were dogs free from pelvic hind limbs orthopedic affection records, weighing between 15 and 40 kilos, without a preference for breed or gender and ageing between two and seven years old. A total of 42 radiographic images in strict lateral radiographic view and 42 inclined limb radiographic views were obtained. Three observers with TPA calculation experience made measurements. In the calculus for the strict lateral radiographic view the first observer has reached an average of 23,35º ± 2,82, the second observer 23,88º ± 4,83 and the third observer 24,54º ± 4,01. No significant statistic differences among the calculus of the three evaluators p=0,944 (P>0,05) was found. In the calculus of the inclined limbs radiographic views the first observer reached an average of 21,69º ± 4,22, the second observer 19,42º ± 5,92 and the third observer 22,64º ±. 5,23. Significant statistic difference in the calculus of the three observers, p=0,016, that is to say, P<0,05 was found. The data indicated that the inclined limb radiographic image compromises the final value of the calculation of tibial plateau angle in dogs. Thus, correct positioning of the pelvic limb, in a strict lateral radiographic view, must be always used for obtaining images aiming at measuring the value of TPA.(AU)