We compared revision and mortality rates of 4668 patients undergoing primary total hip and knee replacement between 1989 and 2007 at a University Hospital in New Zealand. The mean age at the time of surgery was 69 years (16 to 100). A total of 1175 patients (25%) had died at follow-up at a mean of ten years post-operatively. The mean age of those who died within ten years of surgery was 74.4 years (29 to 97) at time of surgery. No change in comorbidity score or age of the patients receiving joint replacement was noted during the study period. No association of revision or death could be proven with higher comorbidity scoring, grade of surgeon, or patient gender.

We found that patients younger than 50 years at the time of surgery have a greater chance of requiring a revision than of dying, those around 58 years of age have a 50:50 chance of needing a revision, and in those older than 62 years the prosthesis will normally outlast the patient. Patients over 77 years old have a greater than 90% chance of dying than requiring a revision whereas those around 47 years are on average twice as likely to require a revision than die. This information can be used to rationalise the need for long-term surveillance and during the informed consent process.

Aims. The antidiabetic agent metformin inhibits fibrosis in various organs. This study aims to elucidate the effects of hyperglycaemia and metformin on knee joint capsule fibrosis in mice. Methods. Eight-week-old wild-type (WT) and type 2 diabetic (db/db) mice were divided into four groups without or with metformin treatment (WT met(-/+), Db met(-/+)). Mice received daily intraperitoneal administration of metformin and were killed at 12 and 14 weeks of age. Fibrosis morphology and its related genes and proteins were evaluated. Fibroblasts were extracted from the capsules of 14-week-old mice, and the expression of fibrosis-related genes in response to glucose and metformin was evaluated in vitro. Results. The expression of all fibrosis-related genes was higher in Db met(-) than in WT met(-) and was suppressed by metformin. Increased levels of fibrosis-related genes, posterior capsule thickness, and collagen density were observed in the capsules of db/db mice compared with those in WT mice; these effects were suppressed by metformin. Glucose addition increased fibrosis-related gene expression in both groups of mice in vitro. When glucose was added, metformin inhibited the expression of fibrosis-related genes other than cellular communication network factor 2 (Ccn2) in WT mouse cells. Conclusion. Hyperglycaemia promotes fibrosis in the mouse knee joint capsule, which is inhibited by metformin. These findings can help inform the development of novel strategies for treating knee joint capsule fibrosis. Cite this article: Bone Joint Res 2024;13(7):321–331

The objective of this study is to determine the knee joint forces when rising from a kneeling position. We have developed a new type of knee prosthesis which is capable of attaining Japanese style sitting. To run the simulations and experiments needed to assess the performance of this prosthesis, it is necessary to know what forces act on the knee during deep flexion. Because these data are lacking, we created a 2D mathematical model of the lower leg to help determine knee joint forces during deep flexion. Healthy subjects of ten males (age of 25±4years, height of 170.3±9.1cm, and weight of 67.0±22.2kg) and five females (25±3years, 161±7.1cm, 47.7±6.2kg) participated in the experiment. Ground reaction force and joints angles were measured using a force plate and a motion recording system respectively. The collected data were entered into our mathematical model, and the muscle forces and the knee joint forces were calculated. To verify our model, we first used it to run simulation of middle and high flexions of the knee joint. In vivo data for these actions are available in the literature, and the results from our simulation were in good agreement with these data. We then collected the data and run simulation when rising from a kneeling position under the conditions shown in Fig. 1. They were a) double leg rising (both legs are aligned) without using the arms, b) ditto but using the arms, c) single leg rising (legs are in the front and the rear respectively) without using the arms, and d) ditto but using the arms. We obtained the following results. The statistics of the maximum values on the single knee joint for each condition were; a) Fmax=5.1±0.4 [BW: (force on the knee joint)/(body weight)] at knee flexion angle of Q=140±8°, b) Fmax=3.2±0.9[BW] at Q=90±10°, c) Fmax-d=5.4±0.5[BW] at Qd=62±20° for the dominant leg and Fmax-s=3.0±0.5[BW] at Qs=138±6° for the supporting leg respectively, and d) Fmax-d=3.9±1.5[BW] at Qd=70±17° for the dominant, and Fmax-s=2.1±0.5 [BW] at Qs=130±11° for the supporting. We may conclude that the single leg rising should be recommended since the maximum knee joint force did not become large as long as the knee was at deep flexion. The values introduced in this study could be used to assess the strength of the knee prosthesis at deep flexion. To obtain more realistic values of the joint forces, it is necessary to determine the ratio of the forces exerted by the mono-articular and the bi-articular joint muscles

The knee joint has also a periarticular adipose tissue, which is known as Hoffa's fat pad (IPFP). IPFP has a dual function in the joint it reduces the concentration of Nitric Oxide, the release of glycosaminoglycans and the expression of MMP1 in the cartilage, but it also contains MSC and macrophages. Our hypothesis is that synovial fluid contains elements, not all of which are understood, which act as messengers and alter the “homeostasis” of the knee and the metabolism of all the cellular components of the joint, including the MSC of Hoffa's fat pad, thus making them another piece in the puzzle as far as OA of the knee is concerned. The IPFP of 37 patients with OA and 36 patients with ACL rupture were analyzed. Isolation, primary culture, and a functional and proteomic study of MSCs from IPFP were performed. Our results show that OA of the knee, in its more severe phases, also affects the MSC's of IPFP, which is a new actor in the OA degenerative process and which can contribute to the origin, onset and progression of the disease. A differential protein profile between OA and ACL patients were identified. Infrapatellar pad should be regarded as an adipose tissue with its own characteristics and it´s also able to produce and excrete important inflammatory mediators directly into the knee joint

Abstract. Introduction. Knee braces are limited to providing passive support. There is currently no brace available providing both continuous monitoring and active robot-assisted movements of the knee joint. This project aimed to develop a wearable intelligent motorised robotic knee brace to support and monitor rehabilitation for a range of knee conditions including post-surgical rehabilitation. This brace can be used at home providing ambulatory continuous passive movement obviating the need for hospital admissions. Methodology. A wearable sensing system monitoring knee range of motion was developed to provide remote feedback to clinicians and real-time guidance for patients. A prototype of an exoskeleton providing dynamic motion assistance was developed to help patients complete their exercise goals and strengthen their muscles. The accuracy and reliability of those functions were validated in human participants during exercises including knee flexion/extension (FE) in bed and in chair, sit-to-stand and stand-to-sit. Results. The knee FE measurement from the sensing system showed high accuracy (correlation coefficient of 0.99°) in human participants. The real-time FE data during exercises showed that the desired exoskeleton rotation fitted well with the participant's knee rotation. This indicated the exoskeleton could coordinate with the participant's knee motion by providing consistent motion assistance. The development of user interfaces to provide feedback is currently underway. Conclusion. A wearable robotic knee brace to monitor and support knee rehabilitation exercises was successfully developed. Further development of this device with the use of artificial intelligence has the potential to aid patient rehabilitation in a variety of knee conditions

This study aims to create a novel computational workflow for frontal plane laxity evaluation which combines a rigid body knee joint model with a non-linear implicit finite-element model wherein collateral ligaments are anisotropically modelled using subject-specific, experimentally calibrated Holzpfel-Gasser-Ogden (HGO) models. The framework was developed based on CT and MRI data of three cadaveric post-TKA knees. Bones were segmented from CT-scans and modelled as rigid bodies in a multibody dynamics simulation software (MSC Adams/view, MSC Software, USA). Medial collateral and lateral collateral ligaments were segmented based on MRI-scans and are modelled as finite elements using the HGO model in Abaqus (Simulia, USA). All specimens were submitted varus/valgus loading (0-10Nm) while being rigidly fixed on a testing bench to prevent knee flexion. In subsequent computer simulations of the experimental testing, rigid bodies kinematics and the associated soft-tissue force response were computed at each time step. Ligament properties were optimised using a gradient descent approach by minimising the error between the experimental and simulation-based kinematic response to the applied varus/valgus loads. For comparison, a second model was defined wherein collateral ligaments were modelled as nonlinear no-compression spring elements using the Blankevoort formulation. Models with subject-specific, experimentally calibrated HGO representations of the collateral ligaments demonstrated smaller root mean square errors in terms of kinematics (0.7900° +/− 0.4081°) than models integrating a Blankevoort representation (1.4704° +/− 0.8007°). A novel computational workflow integrating subject-specific, experimentally calibrated HGO predicted post-TKA frontal-plane knee joint laxity with clinically applicable accuracy. Generally, errors in terms of tibial rotation were higher and might be further reduced by increasing the interaction nodes between the rigid body model and the finite element software. Future work should investigate the accuracy of resulting models for simulating unseen activities of daily living

Objectives. The aim of this study was to investigate the biomechanical effect of the anterolateral ligament (ALL), anterior cruciate ligament (ACL), or both ALL and ACL on kinematics under dynamic loading conditions using dynamic simulation subject-specific knee models. Methods. Five subject-specific musculoskeletal models were validated with computationally predicted muscle activation, electromyography data, and previous experimental data to analyze effects of the ALL and ACL on knee kinematics under gait and squat loading conditions. Results. Anterior translation (AT) significantly increased with deficiency of the ACL, ALL, or both structures under gait cycle loading. Internal rotation (IR) significantly increased with deficiency of both the ACL and ALL under gait and squat loading conditions. However, the deficiency of ALL was not significant in the increase of AT, but it was significant in the increase of IR under the squat loading condition. Conclusion. The results of this study confirm that the ALL is an important lateral knee structure for knee joint stability. The ALL is a secondary stabilizer relative to the ACL under simulated gait and squat loading conditions. Cite this article: Bone Joint Res 2019;8:509–517

Abstract. Background. Little scientific evidence is available regarding the effect of knee joint line obliquity (JLO). Methods. 10 fresh-frozen human cadaveric knees were axially loaded to 1500 N in a materials testing machine with the joint line tilted 0, 4, 8, and 12 degrees varus and valgus, at 0, and 20 degrees of knee flexion. The mechanical compression axis was aligned to the centre of the tibial plateau. Contact pressures / areas were recorded by sensors inserted between the tibia and femur below the menisci. Changes in relative femoral and tibial position in the coronal plane were obtained by an optical tracking system. Results. medial and lateral JLO caused significant tibiofemoral subluxation and pressure distribution changes. Medial (varus) JLO caused the femur to sublux medially down the coronal slope of the tibial plateau, and vice versa for lateral (valgus) downslopes (P=0.01). Areas of peak pressure moved 12 mm and 8 mm across the medial and lateral condyles, onto the ‘downhill’ meniscus and the ‘uphill’ tibial spine. Changes in JLO had only small effects on maximum contact pressures. Conclusion. A change of JLO during load bearing caused significant mediolateral tibiofemoral subluxation. The femur slid down the slope of the tibial plateau to abut the tibial eminence and also to rest on the downhill meniscus. Clinical Relevance. These results provide important information for understanding the consequences of creating coronal JLO and for clinical practice in terms of osteotomy planning regarding the effect on JLO

Knee joint distraction (KJD) has been associated with clinical and structural improvement and synovial fluid (SF) marker changes. However, structural changes have not yet been shown satisfactorily in regular care, since radiographic acquisition was not fully standardized. AI-based modules have shown great potential to reduce reading time, increase inter-reader agreement and therefore function as a tool for treatment outcome assessment. The objective was to analyse structural changes after KJD in patients using this AI-based measurement method, and relate these changes to clinical outcome and SF markers. 20 knee OA patients (<65 years old) were included in this study. KJD treatment was performed using an external fixation device, providing 5 mm distraction for 6 weeks. SF was aspirated before, during and immediately after treatment. Weight-bearing antero-posterior knee radiographs and WOMAC questionnaires were collected before and ~one year after treatment. Radiographs were analysed with the Knee Osteoarthritis Labelling Assistant (KOALA, IB Lab GmbH, Vienna, Austria), and 10 pre-defined biomarker levels in SF were measured by immunoassay. Radiographic one-year changes were analysed and linear regression was used to calculate associations between changes in standardized joint space width (JSW) and WOMAC, and changes in JSW and SF markers. After treatment, radiographs showed an improvement in Kellgren-Lawrence grade in 7 of 16 patients that could be evaluated; 3 showed a worsening. Joint space narrowing scores and continuous JSW measures improved especially medially. A greater improvement in JSW was significantly associated with a greater improvement in WOMAC pain (β=0.64;p=0.020). A greater increase in MCP1 (β=0.67;p=0.033) and lower increase in TGFβ1 (β=-0.787;p=0.007) were associated with JSW improvement. Despite the small number of patients, also in regular care KJD treatment shows joint repair as measured automatically on radiographs, significantly associated with certain SF marker change and even with clinical outcome

The aim of this research was to determine biomechanical markers which differentiate medial knee osteoarthritis (OA) patients who do and do not show structural progression over a 2-year period. A cohort of 36 subjects was selected from a longitudinal study (Meireles et al 2017) using Kellgren-Lawrence (KL) scores at baseline and 2-year follow-up. The cohort consisted of 10 healthy controls (HC) (KL=0 at both time points), 15 medial knee OA non-progressors (NPKOA) (KL≥1 at baseline and no change over 2 years), and 11 medial knee OA progressors (PKOA) (KL≥1 at baseline and increase of ≥1 over 2 years). 3D integrated motion capture data from three walking trials were processed through a musculoskeletal modelling framework (Smith et al 2016) to estimate knee joint loading parameters (i.e., magnitude of mean contact pressure, and centre of pressure (COP)). Parameters at first and second peak were extracted and compared between groups using Kruskal-Wallis and Mann-Whitney tests. Higher magnitudes were observed in PKOA vs NPKOA, and PKOA vs HC groups at both time points. Additionally, a posterior (1st and 2nd peak), and lateral (2nd peak) shift in medial compartment COP was shown between PKOA and NPKOA, and PKOA and HC subjects. Interestingly, in the studied parameters, no differences were observed between NPKOA and HC groups. Significantly higher magnitude, and a more posterior and lateral COP was observed between PKOA and NPKOA patients. These differences, combined with an absence of difference between NPKOA and HC suggest structural OA progression is driven by a combination of altered loading magnitude and location. These results may serve as guidelines for targeted gait retraining rehabilitation to slow or stop knee OA progression whereby shifting COP anterior and medial and reducing magnitude by ~22% may shift patients from a PKOA to a NPKOA trajectory

The October 2023 Knee Roundup. 360. looks at: Cementless total knee arthroplasty is associated with more revisions within a year; Kinematically and mechanically aligned total knee arthroplasties: long-term follow-up; Aspirin thromboprophylaxis following primary total knee arthroplasty is associated with a lower rate of early periprosthetic joint infection compared with other agents; The impact of a revision arthroplasty network on patient outcomes; Re-revision knee arthroplasty in a tertiary centre: how does infection impact on outcomes?; Does the knee joint have its own microbiome?; Revision knee surgery provision in Scotland; Aspirin is a safe and effective thromboembolic prophylaxis after total knee arthroplasty: a systematic review and meta-analysis; Patellar resurfacing and kneeling ability after total knee arthroplasty: a systematic review

INTRODUCTION. Applying the proper amount of tension to knees collateral ligaments during surgery is a prerequisite to achieve optimal performance after TKA. It must be taken into account that lower values of ligament tension could lead to an instable joint while higher values could induce over-tensioning thus leading to problems at later follow-up: a “functional stability” must then be defined and achieved to guarantee the best results. In this study, an experimental cadaveric activity was performed to measure the minimum tension required to achieve functional stability in the knee joint. METHODS. Ten cadaveric knee specimens were investigated; each femur and tibia was fixed with polyurethane foam in specific designed 3D-printed fixtures and clamped to a loading frame. A constant displacement rate of 0.05 mm/s was applied to the femoral clamp in order to achieve joint stability and the relative force was measured by the machine: the lowest force guaranteeing joint stability was then determined to be the one corresponding to the slope change in the force/displacement curve, representing the activation of the elastic region of both collateral ligaments. The force span between the slack region and the found point was considered to be the tension required to reach the functional stability of the joint. This methodology was applied on intact knee, after ACL-resection and after further PCL-resection in order to simulate the knee behavior in CR and PS implants. The test was performed at 0, 30, 60 and 90° of flexion using a specifically designed device. Each configuration was analyzed three times for the sake of repeatability. RESULTS. Results demonstrated that an overall tension of 40–50N is sufficient to reach stability in native knee with intact cruciate ligaments. Similar values appear to be sufficient in an ACL-resected knee, while higher tension is required (up to 60N) for stability after ACL and PCL resection. Moreover, the tension required for stabilization was slightly higher at 60° of flexion compared to the one required at the other angles, reflecting thus the mid-flection instability behavior. DISCUSSION AND CONCLUSIONS. The results are in agreement to other experimental studies. 1,2. and show that the tensions necessary to stabilize a knee joint in different ligament conditions are way lower than the ones usually applied via tensioners nowadays. To reach functional stability, surgeons should consider such results intraoperatively to avoid laxity, mid-flexion instability or ligament over-tension

Knee joint distraction (KJD) is a joint-preserving treatment strategy for severe osteoarthritis (OA) that provides long-term clinical and structural improvement. Data from both human trials and animal models indicate clear cartilage regeneration from 6 months and onwards post-KJD. However, recent work showed that during distraction, the balance between catabolic and anabolic indicators is directed towards catabolism, as indicated by collagen type 2 markers, proteoglycan (PG) turnover and a catabolic transcription profile [unpublished data]. The focus of this study was to investigate the cartilage directly and 10 weeks after joint distraction in order to elucidate the shift from a catabolic to an anabolic cartilage state. Knee OA was induced bilaterally in 8 dogs according to the groove model. After 10 weeks of OA induction, all 8 animals received right knee joint distraction, employing the left knee as an OA control. After 8 weeks of distraction, 4 dogs were euthanized and after 10 weeks of follow-up the 4 other dogs. Macroscopic cartilage degeneration and synovial tissue inflammation was assessed using the OARSI canine scoring system. PG content was determined spectrometrically using Alcian Blue dye solution and the synthesis of newly formed PGs was determined using . 35. SO. 4. 2-. as a tracer, as was described before. Directly after KJD, macroscopic cartilage damage of the right tibial plateau was higher compared to the left OA control (OARSI score: 1.7±0.2 vs 0.6±0.3; p < 0.001). 10 weeks post-KJD this difference persisted (OARSI score: 1.4± 0.6 vs 0.6±0.3; p = 0.05). Directly after KJD, there was no difference in synovial inflammation between KJD and OA control (OARSI score: 1.4±0.5). At 10 weeks synovial inflammation increased significantly in the distracted knee (OARSI score: 2.1±0.3 vs 1.4±0.5; p < 0.05). Biochemical analysis of the tibia cartilage directly after KJD revealed a lower PG content (20.1±10.3 mg/g vs 23.7±11.7 mg/g). At 10 weeks post-KJD this difference in PG content was less (24.8±6.8 mg/g vs 25.4±7.8 mg/g). The PG synthesis rate directly after KJD appeared significantly lower vs. OA (1.4±0.6 nmol/h.g vs 5.9±4.4 nmol/h.g; p < 0.001)). However, 10 weeks post-KJD this difference was not detected (3.7±1.2 nmol/h.g vs 2.9±0.8 nmol/h.g), and the synthesis rate in the distracted knee was increased compared to directly after distraction (p < 0.01). Further in-depth investigation of the material is ongoing; these first results suggest that the shift from a catabolic to an anabolic state occurs within the first weeks after joint distraction, mostly reflected in the biochemical changes. As such, the post-distraction period seems to be essential in identifying key-players that support intrinsic cartilage repair

Aims. The aim of this study was to determine the prevalence and impact of tourniquet use in patients undergoing limb salvage surgery with endoprosthetic reconstruction for a tumour around the knee. Methods. We retrieved data from the Prophylactic Antibiotic Regimens in Tumor Surgery (PARITY) trial; specifically, differences in baseline characteristics, surgical details, and postoperative functional outcomes between patients who had undergone surgery under tourniquet and those who had not. A linear regression model was created to evaluate the impact of tourniquet use on postoperative Toronto Extremity Salvage Scores (TESSs) while controlling for confounding variables. A negative-binomial regression model was constructed to explore predictors of postoperative length of stay (LOS). Results. Of the 604 patients enrolled in the PARITY trial, 421 had tumours around the knee joint, of whom 225 (53%) underwent surgery under tourniquet. The tourniquet group was younger (p = 0.014), more likely to undergo surgery for a tumour of the tibia, and had shorter operating times by a mean of 50 minutes (95% confidence interval 30 to 72; p < 0.001). The adjusted linear regression model found that the use of a tourniquet, a shorter operating time, and a higher baseline TESS independently predicted better function at both three- and six-month follow-up. The negative-binomial regression model showed that tourniquet use, shorter operating time, younger age, and intraoperative tranexamic acid administration independently predicted a shorter LOS in hospital. Conclusion. The results of this study show that in patients undergoing resection of a tumour around the knee and endoprosthetic reconstruction, the use of an intraoperative tourniquet is associated with a shorter operating time, a reduced length of stay in hospital, and a better early functional outcome. Cite this article: Bone Joint J 2022;104-B(10):1168–1173

Aims. Orthopaedic surgery requires grafts with sufficient mechanical strength. For this purpose, decellularized tissue is an available option that lacks the complications of autologous tissue. However, it is not widely used in orthopaedic surgeries. This study investigated clinical trials of the use of decellularized tissue grafts in orthopaedic surgery. Methods. Using the ClinicalTrials.gov (CTG) and the International Clinical Trials Registry Platform (ICTRP) databases, we comprehensively surveyed clinical trials of decellularized tissue use in orthopaedic surgeries registered before 1 September 2022. We evaluated the clinical results, tissue processing methods, and commercial availability of the identified products using academic literature databases and manufacturers’ websites. Results. We initially identified 4,402 clinical trials, 27 of which were eligible for inclusion and analysis, including nine shoulder surgery trials, eight knee surgery trials, two ankle surgery trials, two hand surgery trials, and six peripheral nerve graft trials. Nine of the trials were completed. We identified only one product that will be commercially available for use in knee surgery with significant mechanical load resistance. Peracetic acid and gamma irradiation were frequently used for sterilization. Conclusion. Despite the demand for decellularized tissue, few decellularized tissue products are currently commercially available, particularly for the knee joint. To be viable in orthopaedic surgery, decellularized tissue must exhibit biocompatibility and mechanical strength, and these requirements are challenging for the clinical application of decellularized tissue. However, the variety of available decellularized products has recently increased. Therefore, decellularized grafts may become a promising option in orthopaedic surgery. Cite this article: Bone Joint Res 2023;12(3):179–188

It is known that the gait dynamics of elderly substantially differs from that of young people. However, it has not been well studied how this age-related gait dynamics affects the knee biomechanics, e.g., cartilage mechanical response. In this study, we investigated how aging affects knee biomechanics in a female population using subject-specific computational models.

Two female subjects (ages of 23 and 69) with no musculoskeletal disorders were recruited. Korea National Institute for Bioethics Policy Review Board approved the study. Participants walked at a self-selected speed (SWS), 110% of SWS, and 120% of SWS on 10 m flat ground. Three-dimensional marker trajectories and ground reaction forces (Motion Analysis, USA), and lower limbs’ muscle activities were measured (EMG, Noraxon USA). Knee cartilage and menisci geometries were obtained from subjects’ magnetic resonance images (3T, GE Health Care). An EMG-assisted musculoskeletal finite element modeling workflow was used to estimate knee cartilage tissue mechanics in walking trials. Knee cartilage and menisci were modeled using a transversely isotropic poroviscoelastic material model.

Walking speed in SWS, 110%, and 120% of SWS were 1.38 m/s, 1.51 m/s, and 1.65 m/s for the young, and 1.21 m/s, 1.34 m/s and 1.46 m/s for the elderly, respectively. The maximum tensile stress in the elderly tibial cartilage was ~25%, ~33%, and ~32% lower than the young at SWS, 110%, and 120% of SWS, respectively. These preliminary results suggest that the cartilage in the elderly may not have enough stimulation even at 20% increases in walking speed, which may be one reason for tissue degeneration. To enhance these findings, further study with more subjects and different genders will investigate how age-related gait dynamics affects knee biomechanics.

Acknowledgments: Australian NHMRC Ideas Grant (APP2001734), KITECH (JE220006)

Aim. This study evaluated target tissue concentrations of double dose cefuroxime administered intravenously as either one 15 min infusion of 3,000 mg (Group 1) or two single 15 min infusions of 1,500 mg administered 4 h apart (Group 2). Method. Sixteen pigs were randomised into two groups of eight. Cortical and cancellous bone, synovial fluid of the knee joint and subcutaneous adipose tissue concentrations were measured based on sampling via microdialysis. Plasma samples were collected as a reference. Comparison of the groups was based on time with concentrations above relevant minimal inhibitory concentrations (fT>MIC) of 4 μg/mL. Results. The mean time fT>MIC (4 μg/mL) across compartments was longer for Group 2 (280–394 min) than for Group 1 (207–253 min) (p<0.01). Cortical bone showed a tendency towards longer fT>MIC (4 μg/mL) in Group 2 (280 min) than in Group 1 (207 min) (p=0.053). Within 50 min after administration, the mean concentration of 4 μg/mL was reached in all compartments for both groups. The mean concentrations decreased below 4 μg/mL after approximately 4 h (Group 1) and 3 h (Group 2) from initiation of administration (time zero). Conclusions. During an 8 h interval, double-dose cefuroxime administered as 2 × 1,500 mg with a 4 h interval provides longer time above MIC breakpoint for Staphylococcus aureus (4 μg/mL) than a single bolus of 3,000 mg cefuroxime. To maintain sufficient tissue concentrations during longer surgeries, re-administration of cefuroxime (1,500 mg) should be considered 3 h after the first administration

Aims

Knee osteoarthritis (OA) involves a variety of tissues in the joint. Gene expression profiles in different tissues are of great importance in order to understand OA.

Aim. Little is known about microbiological spectrum and resistance patterns as well as the clinical outcome in patients who undergo a repeat first stage procedure as part of a 2-stage revision arthroplasty for the treatment of periprosthetic hip and knee joint infections. Methods. Between 2011 and 2019, a total of 327 2-stage revision arthroplasties were performed on 312 patients with PJI of the knee and hip at our institution. We performed a retrospective analysis of all patients, who underwent a repeat first stage procedure regarding re-revision rate, host factors, culture negative and positive stages, monomicrobial and polymicrobial infections as well as microbiological spectrum and antimicrobial resistance patterns. Results. Overall, 52/312 (16.7%) patients (27 knee/25 hip) underwent a repeat first stage procedure. There were 35/52 (67.3%) culture positive first, 17/52 (32.7%) culture positive repeat first and 12/52 (23.1%) culture positive second stage procedures. In 13/52 (25%) patients a re-revision surgery was necessary at a median follow-up of 46.8 months (range, 12.2 to 93.3 months). High re-revision rates (10/12 [83.3%]) were found in patients with culture positive second stage and low re-revision rates (3/40 [7.5%]; p<0.01) were found in patients with culture negative second stage. The microbiological spectrum changed in 9/11 (81.8%) patients between culture positive first and repeat first stage, in 3/4 (75%) patients between culture positive repeat first and second stage and in 5/6 (83.3%) between culture positive second stage and subsequent re-revision surgery. Moreover, the antimicrobial resistance pattern changed in 6/9 (66.7%) of persistent microorganisms. Conclusion. Microbiological results during first, repeat first and second stage procedures significantly impacted the re-revision rates and changes in microbiological spectrum and resistance patterns between stages are common. However, if eradication of the microorganism at second stage can be accomplished, low re-revision rates can be achieved, even in patients who require a repeat first stage procedure

Aims. This study aimed to evaluate the BioFire Joint Infection (JI) Panel in cases of hip and knee periprosthetic joint infection (PJI) where conventional microbiology is unclear, and to assess its role as a complementary intraoperative diagnostic tool. Methods. Five groups representing common microbiological scenarios in hip and knee revision arthroplasty were selected from our arthroplasty registry, prospectively maintained PJI databases, and biobank: 1) unexpected-negative cultures (UNCs), 2) unexpected-positive cultures (UPCs), 3) single-positive intraoperative cultures (SPCs), and 4) clearly septic and 5) aseptic cases. In total, 268 archived synovial fluid samples from 195 patients who underwent acute/chronic revision total hip or knee arthroplasty were included. Cases were classified according to the International Consensus Meeting 2018 criteria. JI panel evaluation of synovial fluid was performed, and the results were compared with cultures. Results. The JI panel detected microorganisms in 7/48 (14.5%) and 15/67 (22.4%) cases related to UNCs and SPCs, respectively, but not in cases of UPCs. The correlation between JI panel detection and infection classification criteria for early/late acute and chronic PJI was 46.6%, 73%, and 40%, respectively. Overall, the JI panel identified 12.6% additional microorganisms and three new species. The JI panel pathogen identification showed a sensitivity and specificity of 41.4% (95% confidence interval (CI) 33.7 to 49.5) and 91.1% (95% CI 84.7 to 94.9), respectively. In total, 19/195 (9.7%) could have been managed differently and more accurately upon JI panel evaluation. Conclusion. Despite its microbial limitation, JI panel demonstrated clinical usefulness by complementing the traditional methods based on multiple cultures, particularly in PJI with unclear microbiological results. Cite this article: Bone Joint Res 2024;13(7):353–361

The contact condition in the human knee joint must play important roles especially in dynamic loading situations where the loads transfer in the knee. In this study, the impact stress propagations through the inside of the knee joint were simulated using the three-dimensional finite element analysis (FEA). And the differences in the stress distribution were investigated between the intact knee and the total replacement condition. The finite element (FE) models of an intact human knee joint and a total replaced knee joint were constructed with high shape fidelity. The intact model included the cortical bone, cancellous bone, articular cartilage, bone marrow, and meniscus. And the total replacement knee FE model, which is consisted of the artificial femoral and tibial components were also prepared to compare the impact propagations with the intact model (Figure 1). Impact load were applied to the proximal femur of the FE models under the same conditions as those of the weight-drop experiments with the knee joint specimens. The FEA results showed that the impact stress propagated to the tibia through the knee joint for several milliseconds. The values and the time dependent change of the compressive strain on the cortical surface had good agreement with the experimental results. The compressive stress mainly propageted at the medial side, with 1.0 MPa at 1.2 milliseconds. Especially, the impact stress propagated not only in the cortical surface area which has hard material property but also in the soft cancellous bone region inside the knee joint. The mass density of the cancellous bone has similar to that of the cortical bone, and thus the role of the load bearing in the cancellous area must be much increasing under the impact condition. In the total replacement model, concentration of the impact compressive stress was observed with 2.8 MPa at the tibial region, while not under the normal intact conditions (Figure 2). Since the total replacement model is formed of different materials and the impact propagations were inhibited by the interfacial condition, such as sliding or debonding, it is considered that the contact condition between such materials have a great effect on the stress propagation

Aims. Knee joint distraction (KJD) is a relatively new, knee-joint preserving procedure with the goal of delaying total knee arthroplasty (TKA) in young and middle-aged patients. We present a randomised controlled trial comparing the two. Patients and Methods. The 60 patients ≤ 65 years with end-stage knee osteoarthritis were randomised to either KJD (n = 20) or TKA (n = 40). Outcomes were assessed at baseline, three, six, nine, and 12 months. In the KJD group, the joint space width (JSW) was radiologically assessed, representing a surrogate marker of cartilage thickness. Results. In total 56 patients completed their allocated treatment (TKA = 36, KJD = 20). All patient reported outcome measures improved significantly over one year (p < 0.02) in both groups. At one year, the TKA group showed a greater improvement in only one of the 16 patient-related outcome measures assessed (p = 0.034). Outcome Measures in Rheumatology-Osteoarthritis Research Society International clinical response was 83% after TKA and 80% after KJD. A total of 12 patients (60%) in the KJD group sustained pin track infections. In the KJD group both mean minimum (0.9 mm, standard deviation (. sd. ) 1.1) and mean JSW (1.2 mm, . sd. 1.1) increased significantly (p = 0.004 and p = 0.0003). Conclusion. In relatively young patients with end-stage knee osteoarthritis, KJD did not demonstrate inferiority of outcomes at one year when compared with TKA. However, there is a high incidence of pin track infection associated with KJD. Cite this article: Bone Joint J 2017;99-B:51–8

The Total Knee Replacement (TKR) has been used as the effective treatment for osteoarthritis of the knee. The load of the knee joint is generally applied at the heel strike as the impact loading. In the elderly who had muscle weakness or weakening eyesight, it can be anticipated that more excessive loads are often added to the knees when they stumble or trip over. And the varus / valgus alignments of the femur and tibia differs among patients. However, most finite element analyses considering the effect of the alignments have rarely been performed. In this study, the mounting angle of the tibia component in the TKR knee was changed, and the effect of the change on the load transfer was assess using finite element analyses. Based on the CT images, the three-dimensional finite element models of the natural knee joint and TKR knee joint were created [Fig. 1]. Each model was constructed from hexahedoral elements with the isotropic material. The numbers of nodes and elements were 10,666 and 8,677 respectively. Under normal alignment, 5 degrees of varus, and 5 degrees of valgus knee, the static analyses at an applied load of 1000N and impact analyses at an applied load of 50 kg were performed. LS-DYNA ver760 software was used for the analyses. The finite element analyses results showed that under the static loading, no stress shielding was observed in the tibial cancellous bone of the intact knee or TKR knee, and the maximum compressive stress was 1.5 MPa. While under the impact loading, the compressive stress generated inside of the cancellous bone was three times higher in the TKR knee joint than that in the intact knee, and the load transfer time was reduced. This result reveals that the cancellous bone have load bearing function especially in the impact condition. When the impact load was applied to the varus and valgus TKR knee, the stress shielding was observed in the tibial cancellous bone, especially in the varus condition. In a case where the tibia component was mounted by tilting it at −5 to 5 degrees depending on the varus/valgus of the knee, the stress shielding was alleviated; the distribution of load was almost the same as that of the TKR knee joint model under the normal alignment [Fig.2]. The effect of a slight difference in the alignment on the stress distribution is expected to be a contributor to determine artificial knee joint shape, loading condition, and other design factors in developing revision arthroplasty or custom-made implant

Total knee arthroplasty is one of the most common surgeries. About 92% of all implanted knee endorposthesis in 2020 were manufactured from uncoated CoCrMo articulating on ultra-high-molecular-weight polyethylene. All articluations generate wear particles and subsequent emission of metal ions due to the mechanical loading. These wear particles cause diverse negative reactions in the surrounding tissues and can lead to implant loosening. Coating technologies might offer the possibility to reduce this wear. Therefore, we investigated the applicability of tetrahedral amorphous carbon (ta-C) coating on CoCrMo alloy.

Polished specimens made of CoCrMo wrought alloy according to ISO 5832-12 were coated with ta-C coatings with different layer structure using pulsed laser deposition (PLD). This process allows the deposition of ta-C coatings with low internal stress using an additional relaxation laser. Surface quality and mechanical properties of the coating were characterised using optical surface measurements (NanoFocus μsurf expert, NanoFocus AG) and a nanoindentation tester NHT³ (Anton Paar GmbH). Scratch tests were performed on Micro Scratch Tester MST³ (Anton Paar TriTec SA) to define the coating adhesion. Pin-on-plate tribological tests, with a polyethylene ball sliding on the ta-C-coated plate under a defined load according to ISO 14243-1 were performed using a linear tribometer (Anton Paar GmbH) to evaluate the tribological and wear properties.

The ta-C coatings showed a mean roughness Ra of 5-20 nm and a hardness up to 60 GPa (n=3). The adhesion of the ta-C coatings (n=3) was comparable to the commercial coatings like TiN and TiNbN. The pin-on-plate tests showed an improvement of tribological properties in comparison with the polished uncoated CoCrMo specimens (n=3).

The ta-C coatings applied by DLP technology show increased hardness compared to the base material and sufficient adhesion. Further research will be needed to investigate the optimal coating strategy for implant coating.

Abstract

Purpose: Posters of study: To produce a virtual reality model of prosthetic knee joint motion, giving detail regarding contact area and contact pressures during the process of walking. Method: Using serial CT scans and data regarding the material properties of bone, cartilage, ligaments and other soft tissue structures a computational “virtual reality model” of the knee has been constructed. This computational model which is a 3D dynamic representation of a human knee joint, may be programmed to replicate the standard gait pattern of the human knee. This study details the development of this model and its validation against the accepted Stenmore Test Rig for modelling of knee joint movement and knee prosthetic wear. The validation results will be presented,. The model allows the calculation and representation of contact pressures and contact areas in the knee joint as it moves through the gait cycle. This study also shows the effect of uni-condular loading and varus mal-positioning which may occur at surgery and the effect this has on the contact area and contact pressures of a prosthetic knee in ambulation. The resultant gait pattern produced by uni-condular loading and exhibited by the virtual knee closely resembles that seen in In Vivo Kinematic Studies reported by other authors. In conclusion we present this as a valid computational dynamic model of knee prosthetic wear and kinematics which represents an enormous advantage over standard mechanical testing and presents possibilities for rapid analysis in new knee joint designs and the effect of abnormalities of gait and wear

Objectives. Malrotation of the femoral component can result in post-operative complications in total knee arthroplasty (TKA), including patellar maltracking. Therefore, we used computational simulation to investigate the influence of femoral malrotation on contact stresses on the polyethylene (PE) insert and on the patellar button as well as on the forces on the collateral ligaments. Materials and Methods. Validated finite element (FE) models, for internal and external malrotations from 0° to 10° with regard to the neutral position, were developed to evaluate the effect of malrotation on the femoral component in TKA. Femoral malrotation in TKA on the knee joint was simulated in walking stance-phase gait and squat loading conditions. Results. Contact stress on the medial side of the PE insert increased with internal femoral malrotation and decreased with external femoral malrotation in both stance-phase gait and squat loading conditions. There was an opposite trend in the lateral side of the PE insert case. Contact stress on the patellar button increased with internal femoral malrotation and decreased with external femoral malrotation in both stance-phase gait and squat loading conditions. In particular, contact stress on the patellar button increased by 98% with internal malrotation of 10° in the squat loading condition. The force on the medial collateral ligament (MCL) and the lateral collateral ligament (LCL) increased with internal and external femoral malrotations, respectively. Conclusions. These findings provide support for orthopaedic surgeons to determine a more accurate femoral component alignment in order to reduce post-operative PE problems. Cite this article: K-T. Kang, Y-G. Koh, J. Son, O-R. Kwon, C. Baek, S. H. Jung, K. K. Park. Measuring the effect of femoral malrotation on knee joint biomechanics for total knee arthroplasty using computational simulation. Bone Joint Res 2016;5:552–559. DOI: 10.1302/2046-3758.511.BJR-2016-0107.R1

Objectives. Static radiostereometric analysis (RSA) using implanted markers is considered the most accurate system for the evaluation of prosthesis migration. By using CT bone models instead of markers, combined with a dynamic RSA system, a non-invasive measurement of joint movement is enabled. This method is more accurate than current 3D skin marker-based tracking systems. The purpose of this study was to evaluate the accuracy of the CT model method for measuring knee joint kinematics in static and dynamic RSA using the marker method as the benchmark. Methods. Bone models were created from CT scans, and tantalum beads were implanted into the tibia and femur of eight human cadaver knees. Each specimen was secured in a fixture, static and dynamic stereoradiographs were recorded, and the bone models and marker models were fitted to the stereoradiographs. Results. Results showed a mean difference between the two methods in all six degrees of freedom for static RSA to be within -0.10 mm/° and 0.08 mm/° with a 95% limit of agreement (LoA) ranging from ± 0.49 to 1.26. Dynamic RSA had a slightly larger range in mean difference of -0.23 mm/° to 0.16 mm/° with LoA ranging from ± 0.75 to 1.50. Conclusions. In a laboratory-controlled setting, the CT model method combined with dynamic RSA may be an alternative to previous marker-based methods for kinematic analyses. Cite this article: K. Stentz-Olesen, E. T. Nielsen, S. De Raedt, P. B. Jørgensen, O. G. Sørensen, B. L. Kaptein, M. S. Andersen, M. Stilling. Validation of static and dynamic radiostereometric analysis of the knee joint using bone models from CT data. Bone Joint Res 2017;6:376–384. DOI: 10.1302/2046-3758.66.BJR-2016-0113.R3

Background

Periprosthetic joint infection (PJI) following total knee arthroplasty (TKA) is a severe complication in terms of disability, morbidity, and cost. We performed a study to investigate whether early PJI (within 90 days of primary TKA) is associated with increased mortality. Secondary aims were to compare mortality rates over time and between surgical treatment methods.

The objective of this study is to investigate the effect of the tensile force ratio between the two extensor muscles for the hip joint on the forces acting on the knee joint. We have created a mathematical model of lower limb and have performed some simulations to introduce the forces acting on the knee joint for various daily activities. With only one exception, our results for knee joint forces were in good or close agreement involving all range of knee flexion either with the in vivo data or other literature data. The exception was that, at high knee flexion angle (knee bend), the tangential components of knee joint force became pretty larger than those from the in vivo data, while the normal components did not differ much with each other though as shown in Fig. 1. We considered that the above mentioned discrepancy was attributed to the fact that in order to solve an indeterminate problem, we had assumed the hamstrings and the gluteus maximus work together with the same force with each other, thereby introducing the hamstrings force too great. Then we expected that the above discrepancy could be eliminated if we change the tensile force ratio between the hamstrings and the gluteus maximus basing upon a certain biomechanical criterion, for example the biological cross-sectional areas. Thus we modified our model so that we could introduce the knee joint forces as a function of the tensile force ratio. Simulation was performed for the various tensile ratio values and it was found that the knee joint force was sensitively affected by the tensile ratio and the above mentioned discrepancy between the simulation results and the in vivo data could be eliminated if the ratio value was appropriately chosen. Figure 2 shows the situation; Variations of Fn and Ft as a function of knee angle q for the various tensile force ratio r between the hamstrings and the gluteus maximus. Where, r=1.56 was determined from the biological cross-sectional areas of the hamstrings and the gluteus maximus and r=4.5 was determined so that the simulation results best fit to the in vivo data. It has been criticized that there exist large variations of knee joint forces obtained from model analyses. And the reasons for this have been attributed to for example such facts that the model is 2D and the parameter values are incorrect. Yet, another important issue may be to find out the way how to determine the value of the synergetic muscles' force ratio with reflecting a biological rationality

INTRODUCTION. In patients with neural disorders such as cerebral palsy, three-dimensional marker-based motion analysis has evolved to become a well standardized procedure with a large impact on the clinical decision-making process. On the other hand, in knee arthroplasty research, motion analysis has been little used as a standard tool for objective evaluation of knee joint function. Furthermore, in the available literature, applied methodologies are diverse, resulting in inconsistent findings [1]. Therefore we developed and evaluated a new motion analysis framework to enable standardized quantitative assessment of knee joint function. MATERIALS AND METHODS. The proposed framework integrates a custom-defined motion analysis protocol with associated reference database and a standardized post-processing step including statistical analysis. Kinematics are collected using a custom-made marker set defined by merging two existing protocols and combine them with a knee alignment device. Following a standing trial, a star-arc hip motion pattern and a set of knee flexion/extension cycles allowing functional, subject-specific calibration of the underlying kinematic model, marker trajectories are acquired for three trials of a set of twelve motor tasks: walking, walking with crossover turn, walking with sidestep turn, stair ascent, stair descent, stair descent with crossover turn, stair descent with sidestep turn, trunk rotations, chair rise, mild squat, deep squat and lunge. This specific set of motor tasks was selected to cover as much as possible common daily life activities. Furthermore, some of these induce greater motion at the knee joint, thus improving the measurement-to-error ratio. Kinetics are acquired by integrating two forceplates in the walkway. Bilateral muscle activity of 8 major muscles is monitored with a 16 channel wireless electromyography (EMG) system. Finally, custom-built software with an associated graphical user interface was created for automated and flexible analysis of gait lab data, including repeatability analysis, analysis of specific kinematic, kinetic and spatiotemporal parameters and statistical comparisons. RESULTS. Following ethical approval and informed consent, the proposed framework was successfully applied in a control group of 80 normal subjects within a wide age-range (age: 54.5Y±19.1; BMI: 25.5±4.0; 40M/40F; 60 Caucasian, 20 Asian) thus constructing the reference database for control. Moreover, the same framework was applied successfully in a randomly selected group of 10 patients with a bi-compartmental knee replacement (BKR) (age: 67.3Y±5.3; BMI: 29.7±3.1; time post-op: 1.65Y±0.4; 2M/8F Caucasian). Comparison between these patients and age-matched controls demonstrates that, for a large range of motor tasks, knee joint kinematics after BKR are as much consistent with the healthy controls (coefficient of multiple correlation (CMC) =0.49) as the consistency within a group of controls or BKR-subjects individually (CMC=0.52). Nevertheless, also significant differences (p<0.0167) were identified which are indicative for retention of pre-operative motion patterns and/or remaining compensations. CONCLUSION. The proposed framework allows in-vivo evaluation of knee joint performance in a standardized, objective and non-invasive way. It is applicable in both healthy subjects and knee replacement patients and is shown to be sufficiently sensitive to detect even relatively small differences between the two populations

Increased incidence of obesity and longer life expectancies will place increased demands on load bearing joints. In the present work, a method of pre-clinical evaluation to assess the condition of the joint and potentially inform on cases of joint deterioration, is described. Acoustic emission (AE) is a non-destructive test methodology that has been used extensively in engineering for condition monitoring of machinery and structures. It is a passive technique that uses piezoelectric sensors to detect energy released from internal structural defects as they deform and grow. The technique has been used with some success in the past to identify characteristic signals generated from the knee joint during activities such as standing and sitting, in candidate arthroplasty patients (1,2). In this study, 40 asymptomatic subjects had AE data generated from their knee joints analysed. Subject characteristics such as age, gender, and lifestyle were disclosed and evaluated against the AE data. Each subject was invited to take a seated position and a piezoelectric AE sensor (Pancom P15, 150kHz resonance, 19mm diameter) was attached to the subject's knee using a wax couplant and tape as close to the articulating surface and on a bony prominence to avoid signal attenuation in the soft tissue. Subjects were invited to sit and stand 3 times. AE data were collected and processed using an AMSY5 AE processor (Vallen, Germany). Tests were repeated on a separate occasion and selected subjects were invited to participate on a third occasion. The AE data of particular interest were the peak amplitudes and the frequency power spectrum of the waveform. Post-test inspection of subject characteristics allowed them to be separated into three broad categories: no previous history (group A), some instances of pain in the knee (group B), and those who have had previous minor surgery on the knee (group C). The corresponding AE results were grouped separately. It was found that groups A and B demonstrated similar signal amplitude characteristics while group C produced much higher, significantly different (p<0.05) amplitudes and amplitude distributions. Typical results are shown in figure 1. At present, broad trends could be identified and relationships emerged between the data and subject history (prior surgery, typical daily activity). Further work will continue with asymptomatic subjects and the work will be extended to pre-operative patients to identify whether certain trends are amplified in this population

Purpose of the study: Knowledge of the normal kinematics of the knee joint, and particularly the femoropatellar joint, is indispensable for evaluating prosthetic implants. Accurate measurements are however necessary, especially for patellar tracking. The purpose of this study was to propose a new experimental set up for analysis of the knee joint and to validate its pertinence in terms of accuracy and incertitude. Materials and Methods: Eight anatomic specimens of non-embalmed healthy knees were tested on the new setup with a fixed femur and a tibia left free to move. The flexion-extension movement was created by applying force to the quadriceps tendon and resistance to the distal end of the tibia. The femorotibial and femoropatellar kinematics were monitored with an infrared optoelectronic tracking system after acquisition of the bone geometry and the position of the markers on stereoradiographs coupled with a specific 3D reconstruction software. The landmarks used to interpret the kinematic measurements were calculated from the reconstructions of anatomic specimens. Incertitude linked to the determination of these landmarks was assessed as was its impact on the kinematic measurements. Results: Trials were run on eight knees to validate the experimental setup and study knee kinematics during flexion-extension movements. Method-related measurement incertitude was less than 0.2° in rotation (1 SD) and less than 0.9 mm in translation (1 SD) for the tibia and less than 0.2° in rotation (1 SD) and 0.6 mm in translation (1 SD) for the patella. Quantitative analysis was completed by an animation to visualise any anomalies under different angles. Discussion: This protocol which couples 3D imaging with a kinematic analysis enables real time tracking of the bone pieces during the experimental trials. This in vitro setup produces femoropatellar and tibial kinematics in agreement with data in the literature. Observations will enable better understanding of femoropatellar function and provide objective data on potential kinematic anomalies. Conclusion: This experimental evaluation combining bone geometry and kinematic monitoring specifically designed for the knee joint should enable objective evaluation of implants and a validation of personalised finite elements models of the knee

Aim

The number of periprosthetic joint infections (PJI) is increasing due to ageing population and increasing numbers of arthroplasty procedures and treatment is costly. Aim of the study was to analyze the direct healthcare costs of PJI in Europe for total hip arthroplasties (THA) and total knee arthroplasties (TKA).

Abstract

Our objective was to examine revision rates and patient reported outcome scores (PROMS) for cemented and uncemented primary total knee joint replacement (TKJR) at six months, one year and five years post-operatively. Patients and Methods: This matched cohort study involved secondary analyses of data collected as part of a large prospective observational study monitoring outcomes following knee replacement in Christchurch, New Zealand. Cemented and uncemented TKJR participants (n = 1526) were matched on age (± 5 years), sex and body mass index (BMI). From this larger sample, PROMS data, Oxford Knee Score and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), out to five years post-operatively were analysed for a matched subset of participants (n = 252).

The average age of participants was 67.9 years (SD 9.4, range 38-94). There were no differences between cemented and uncemented cohorts on the basis of age, sex, BMI or comorbidities, revision rates or PROMS outcomes. Cemented procedures had greater skin to skin times than uncemented procedures (p < 0.01). Unadjusted outcomes comparing risk for revision across the two participant cohorts did not significantly differ. Overall rates for revision were low (cemented 3.2% v uncemented 2.7%, p=0.70). Propensity adjusted associations between baseline characteristics (age, sex, BMI, comorbidity, baseline Oxford and baseline WOMAC scores) also revealed no differences in risk for revision at any post-operative timepoint.

In this large multi-surgeon matched cohort study there were no significant differences in functional outcomes or revision rates, when outcomes following modern cemented and uncemented TKJR were compared out to 5-year follow up. Based on our findings, uncemented TKJR is predictable irrespective of patient's age, BMI or gender

The aim of this work was to develop a novel, accessible and low-cost method, which is sufficient to measure changes in meniscal position in a whole-knee joint model performing dynamic motion in a knee simulator. An optical tracking method using motion markers, MATLAB (MATLAB, The MathWorks Inc.) and a miniature camera system (Raspberry Pi, UK) was developed. Method feasibility was assessed on porcine whole joint knee samples (n = 4) dissected and cemented to be used in the simulator (1). Markers were placed on three regions (medial, posterior, anterior) of the medial meniscus with corresponding reference markers on the tibial plateau, so the relative meniscal position could be calculated. The Leeds high kinematics gait profile scaled to the parameters of a pig (1, 2) was driven in displacement control at 0.5 Hz. Videos were recorded at cycle-3 and cycle-50. Conditions tested were the capsule retained (intact), capsule removed and a medial posterior root tear. Mean relative displacement values were taken at time-points relating to the peaks of the axial force and flexion-extension gait inputs, as well as the range between the maximum and minimum values. A one-way ANOVA followed by Tukey post hoc analysis were used to assess differences (p = 0.05). The method was able to measure relative meniscal displacement for all three meniscal regions. The medial region showed the greatest difference between the conditions. A significant increase (p < 0.05) for the root tear condition was found at 0.28s and 0.90s (axial load peaks) during cycle-3. Mean relative displacement for the root tear condition decreased by 0.29 mm between cycle-3 and cycle-50 at the 0.28s time-point. No statistically significant differences were found when ranges were compared at cycle-3 and cycle-50. The method was sensitive to measure a substantial difference in medial-lateral relative displacement between an intact and a torn state. Meniscus extrusion was detected for the root tear condition throughout test duration. Further work will progress onto human specimens and apply an intervention condition

Purpose

Intra-articular corticosteroid injection is widely used for symptomatic relief of knee osteoarthritis. However, if pain is not improved which consequences a total knee arthroplasty (TKA), there is a potential risk of post-operative periprosthetic joint infection (PJI). The aim of this study is to investigate whether the use of preoperative intra-articular corticosteroid injection increases the risk of PJI and to investigate a time frame in which the risk of subsequent infection is significantly increased.

The interface condition between the prosthesis and the bone tissue must play important roles during dynamic loading transfer through the knee joint. In this study, the three- dimensional impact finite element (FE) simulations were performed to investigate the impact stress propagation. The FE models of a totally replaced knee joint were constructed with the high shape fidelity. The models included the cortical and cancellous bone, articular cartilage, bone marrow, and the artificial femoral and tibial components. The artificial components were set to the femoral and tibial contact area. The FE meshes had 7251 nodal points and 5547 hexahedral elements (Figure 1). The interfacial condition between the artificial component had two kind of contact situations, bonding situation and no-bonding ones. In the bonding situation, the interface between the artificial components and the cancellous bone had fully fixations. The no-bonding allowed the tie-breaking of each other although the interface had the high coefficient of friction. The three kind of the impact loading (1, 5, and 10kgW) were applied from the proximal femur to the distal side of tibia. In the FE simulations, the impact stress propagated to the tibia through the TKR joint components during several milliseconds. On the interfacial surface at the cancellous side of the proximal tibia, the difference in the stress distribution was observed according to the contact situation of the TKR component (Figure 2). The fully fixation (tied to each other) model showed the high compressive stress on the interface. On the other hand, in the no-bonding model, the compressive stress distributed discontinuously and the high compressive stress was observed only in the hole area and edge of the tibial component during the impact loading. In previous research, the cancellous bone had important roles for the load transmission inside the joint especially under the impact loading condition. However, this study indicated that the stress shielding was caused by the imperfect bonding at the interface. More consideration of the interface situation between the bone and component is required to keep stability for impact loading

The objective of this study is to introduce the forces acting on the knee joint while ascending from kneeling. Our research group has developed a new type of knee prosthesis which is capable of attaining complete deep knee flexion such as a Japanese style sitting, seiza. Yet we could not set up various kinds of simulation or experiment to assess the performance of our prosthesis because the data about joints' forces during the ascent from deep knee flexion are lacking. Considering this circumstance, we created a 2D mathematical model of lower limb and determined knee joint force during ascent from kneeling to apply them for the assessment of our prosthesis. Ten male and five female healthy subjects participated in the measurement experiment. Although the measurement of subjects' physical parameters was non-invasive and direct, some parameters had to be determined by referring to the literature. The data of ground reaction force and each joint's angle during the motion were collected using a force plate and video recording system respectively. Then the muscle forces and the joints' forces were calculated through our mathematical model. In order to verify the validity of our model approach, we first introduced the data during the activities with small/middle knee flexion such as level walking and rising from a chair; these kinds of data are available in the literature. Then we found our results were in good agreement with the literature data. Next, we introduced the data during the activities with deep knee flexion; double leg ascent [Fig.1 (a)] and single leg ascent [Fig.1 (b)] from kneeling without using the upper limbs. The statistics of the maximum values on the single knee joint for all the subjects were; during double leg ascent, Fmax = 4.6±0.6 (4.3-5.2) [BW: (force on the knee joint)/(body weight)] at knee flexion angle of b =140±8 (134-147)°, during double leg ascent, Fmax = 4.9±0.5 (4.0-5.6) [BW] at b = 62±33 (28-110)° for the dominant leg, and Fmax = 3.0±0.5 (22.2-3.8) [BW] at b = 138±6 (130-150)° for the supporting leg respectively. We found that the moment arm length, i.e., the location of muscle insertion significantly affected the results, while ascending speeds did not affect the results much. We may conclude that the single leg ascent should be recommended since Fmaxdid not become large while deep knee flexion. The values could be used for assessing the strength of our knee prosthesis from the risk analysis view point

When managing malignant bone tumours in the distal femur with limb salvage, resection and reconstruction with a distal femoral replacement (DFR) conventionally entails prosthetic replacement of the knee joint. In younger patients it is desirable to try to preserve the knee joint. We now use a new Joint-Sparing distal femoral prosthesis in those cases where it is possible to resect the tumour and preserve the femoral condyles. Purpose of study: To look at our early results with knee joint preserving DFR’s. Methods: Between June 2001 and March 2004 the prosthesis was implanted in 8 patients (5 males and 3 females) aged between 8 and 24 years at the time of surgery. The diagnosis was osteosarcoma in 6 cases and chondrosarcoma in 2 cases. All patients were followed regularly and knee range of movement was recorded as well as any complications that occurred. Patients were functionally evaluated using the MSTS Scoring System. Results: Six of the patients had a mean follow-up of 20 months (range 8–33) and in this group 4 had good knee flexion with a mean flexion of 122° (110–130), 1 patient had fair flexion of 60° and 1 patient had poor flexion of 20°. The mean fixed flexion deformity in the 3 patients who had such a deformity was 10° (5–15). There were no intraoperative complications but the patient with poor flexion required an arthrolysis and because of the poor result is under consideration for conversion to a conventional DFR. Two patients had follow-up periods of 3 months or less and are still in their early rehabilitation period. One patient in this group developed sepsis that resolved after an open washout. Conclusions: Our early results with this prosthesis, in the patients with adequate follow-up, have been good in the majority but the two cases of fair and poor knee flexion are disappointing. This particular problem may relate to design and technical factors, which will be discussed in detail

Introduction. The low-cost, no-harm conditions associated with vibroarthography, the study of listening to the vibrations and sound patterns of interaction at the human joints, has made this method a promising tool for diagnosing joint pathologies. This current study focuses on the knee joint and aims to synchronize computational models with vibroarthographic signals via a comprehensive graphical user interface (GUI) to find correlations between kinematics, vibration signals, and joint pathologies. This GUI is the first of its kind to synchronize computational models with vibroarthographic signals and gives researchers a new advantage of analyzing kinematics, vibration signals, and pathologies simultaneously in an easy-to-use software environment. Methods. The GUI (Figure 1) has the option to view live or previously captured fluoroscopic videos, the corresponding computational model, and/or the pre- or post-processed vibration signals. Having more than one signal axes available allows for comparison of different filtering techniques to the same signal, or comparison of signals coming from different sensor placements (ex: medial vs. lateral femoral condyle). Using computational models derived using fluoroscopic data synchronized with the vibration signals, the areas of contact between articulating surfaces can be mapped for the in vivo signal (figure 2). This new method gives the opportunity to find correlations between the different sensor signals and contact maps with the diagnosis and cartilage degeneration map, provided by a surgeon, during arthroscopy or TKA implantation (figure 3). Results. Using previously captured data and newly acquired data for subjects from research studies, several different knee pathologies have been analyzed. The signals were listened to audibly after being processed to add a qualitative side. Sounds coming from knees with pathologies revealed noticeable differences compared to the healthy subjects, and the quantitative analysis further supported our hypothesis (>96% accuracy classification patella arthritic subjects vs. healthy). Discussion. Ideally, transitioning towards real-time kinematic tracking with signal acquisition allows for diagnostic screening tools of the knee joint that will provide feedback of cartilage damage maps as well as potential meniscal or ligament injuries. The method used in this study is multi-faceted in that it allows the subject to perform various daily weight or non-weight bearing activities at his/her own speed which makes it easier to use than if the subject had to be in a very controlled environment

Changes in the knee joint after meniscectomy include ridge formation, narrowing of the joint space, and flattening of the femoral condyle. Investigations suggest that these changes are due to loss of the weight-bearing function of the meniscus. Meniscectomy is not wholly innocuous; it interferes, at least temporarily, with the mechanics of the joint. It seems likely that narrowing of the joint space will predispose to early degenerative changes, but a connection between these appearances and later osteoarthritis is not yet established and is too indefinite to justify clinical deductions

Aims

Periprosthetic joint infections (PJIs) are rare, but represent a great burden for the patient. In addition, the incidence of methicillin-resistant Staphylococcus aureus (MRSA) is increasing. The aim of this rat experiment was therefore to compare the antibiotics commonly used in the treatment of PJIs caused by MRSA.

Aims

Debridement, antibiotics, and implant retention (DAIR) remains one option for the treatment of acute periprosthetic joint infection (PJI) despite imperfect success rates. Intraosseous (IO) administration of vancomycin results in significantly increased local bone and tissue concentrations compared to systemic antibiotics alone. The purpose of this study was to evaluate if the addition of a single dose of IO regional antibiotics to our protocol at the time of DAIR would improve outcomes.

Aims

Tenosynovial giant cell tumour (TGCT) is a rare benign tumour of the musculoskeletal system. Surgical management is fraught with challenges due to high recurrence rates. The aim of this study was to describe surgical treatment and evaluate surgical outcomes of TGCT at an Australian tertiary referral centre for musculoskeletal tumours and to identify factors affecting recurrence rates.

Objectives. Sustained intra-articular delivery of pharmacological agents is an attractive modality but requires use of a safe carrier that would not induce cartilage damage or fibrosis. Collagen scaffolds are widely available and could be used intra-articularly, but no investigation has looked at the safety of collagen scaffolds within synovial joints. The aim of this study was to determine the safety of collagen scaffold implantation in a validated in vivo animal model of knee arthrofibrosis. Materials and Methods. A total of 96 rabbits were randomly and equally assigned to four different groups: arthrotomy alone; arthrotomy and collagen scaffold placement; contracture surgery; and contracture surgery and collagen scaffold placement. Animals were killed in equal numbers at 72 hours, two weeks, eight weeks, and 24 weeks. Joint contracture was measured, and cartilage and synovial samples underwent histological analysis. Results. Animals that underwent arthrotomy had equivalent joint contractures regardless of scaffold implantation (-13.9° versus -10.9°, equivalence limit 15°). Animals that underwent surgery to induce contracture did not demonstrate equivalent joint contractures with (41.8°) or without (53.9°) collagen scaffold implantation. Chondral damage occurred in similar rates with (11 of 48) and without (nine of 48) scaffold implantation. No significant difference in synovitis was noted between groups. Absorption of the collagen scaffold occurred within eight weeks in all animals. Conclusion. Our data suggest that intra-articular implantation of a collagen sponge does not induce synovitis or cartilage damage. Implantation in a native joint does not seem to induce contracture. Implantation of the collagen sponge in a rabbit knee model of contracture may decrease the severity of the contracture. Cite this article: J. A. Walker, T. J. Ewald, E. Lewallen, A. Van Wijnen, A. D. Hanssen, B. F. Morrey, M. E. Morrey, M. P. Abdel, J. Sanchez-Sotelo. Intra-articular implantation of collagen scaffold carriers is safe in both native and arthrofibrotic rabbit knee joints. Bone Joint Res 2016;6:162–171. DOI: 10.1302/2046-3758.63.BJR-2016-0193

Background: Prophylactic taping is commonly used to prevent ankle injuries during sports. However unnatural constraint of the ankle joint may increase the risk of injury to proximal joints such as the knee. Any association between the use of ankle tape and knee joint loading has not previously been investigated. Purpose: To determine changes in ankle and knee kinetics and kinematics associated with use of ankle taping during athletic activities. Thereby, both the prophylactic benefits and the potential of taping to be an isolated mechanism for a ligamentous injury of the knee will be examined. Methods: A kinematic and inverse dynamics model was used to determine ankle and knee joint motion and loading in 22 healthy male participants undertaking running and sidestepping tasks. Both tasks were randomized to planned and unplanned conditions, and undertaken with and without the use of ankle tape. Results: Taping reduced the range of motion at the ankle in all three planes (p< 0.05), as well as peak inversion (p=0.017) and average eversion moments (p=0.013). At the knee, internal rotation moments (p=0.049), internal rotation impulse (0.034), varus moment (p=0.015) and varus impulse (p=0.050) were reduced with the use of ankle tape. There was a trend toward increased valgus impulse for sidestepping trials undertaken with ankle tape (p=0.056). Conclusion: By limiting motion at the ankle, taping increased the mechanical stability of this joint. Ankle taping also provided protective benefits to the knee via reduced internal rotation moments and varus impulses, although the effects were task-specific. Medial collateral and anterior cruciate ligament injuries may, however, occur through increased valgus impulse during sidestepping undertaken with ankle tape

Periprosthetic joint infections (PJI) are challenging complications following arthroplasty. Staphylococci are a frequent cause of PJI and known biofilm producers.

Reoperations for PJI of the hip or knee between 2012 and 2015 performed at Sahlgrenska University Hospital were identified. Medical records were reviewed, and clinical parameters recorded for patients whose intraoperative bacterial isolates had been stored at the clinical laboratory. Staphylococcal strains isolated from reoperations due to first-time PJI were characterised by their ability to form biofilms using the microtiter plate test.

The study group included 49 patients (70 bacterial strains) from first-time PJI, whereof 24 (49%) patients had recurrent infection. Strong biofilm production was significantly associated with recurrent infection. Patients infected with strong biofilm producers had a five-fold increased risk for recurrent infection.

Strong biofilm production was significantly associated with increased antimicrobial resistance and PJI recurrence. This underscores the importance of determining biofilm production and susceptibility as part of routine diagnostics in PJI. Strong staphylococcal biofilm production may have implications on therapeutic choices and suggest more extensive surgery. Furthermore, despite the increased biofilm resistance to rifampicin, results from this study support its use in staphylococcal PJI.

In major lower limb amputation, preservation of the knee joint significantly improves outcome. In the severely compromised limb, to preserve the knee joint, high tibial transection may be necessary creating a less than optimal stump. This study reviews the outcome in below knee amputees with stumps 10cm or shorter. All 209 below knee (BK) amputees attending the New Zealand Artificial Limb Board’s Dunedin Centre were reviewed. The centre is the sole provider of prosthetic services in the southern region. Forty-four amputees (21% of total) had stumps of 10cm or less in length as measured by caliper rule. After a minimum twelve month follow-up these amputees were placed in two groups. Group 1: Short Stump (10cm to 8cm). Group 2: Ultra Short Stump (7.5cm to 5cm). Wood-Stanmore Grades were given for walking ability (Hanspal and Fisher 1991). Rehabilitation was further assessed using a modified Houghton Questionnaire (Houghton et al 1992). Mean stump length for all 209 BK amputees was 12.5 centimeters (range 5 to 25 centimeters). Group 1. Short Stump (ten to eight centimeters 0 – 37 amputees. Nineteen amputees – Good to Excellent (Wood – Stanmore Grade V and V1) i.e. walking indoors and outdoors without aids and with near normal gait. (10 trauma, four dysvascular, four tumour, one infection). Fourteen amputees-Satisfactory (Grade 1V) i.e. walking aid indoors and outdoors (13 dysvascular, one congenital). 4 amputees – Fair Only (Grade 111) i.e. mostly indoors with frame (four dysvascular). Group 2. Ultra Short Stump (7.5cm to 5cm) – seven amputees. Six amputees – Good to Excellent (Grade V or V1) – (all trauma). One amputee – Fair Only (Grade 111) – (dysvascular). Group one mostly had a posterior myocutaneous flap amputation with retention of the proximal fibula. In Group two, all had resection of the proximal fibula with varied flaps often with skin grafting. The patellar tendon was intact but two patients had lost the hamstring insertion with hyperextension of the knee, one requiring prosthesis with side steels and thigh corset. In group two the best results followed high resection of the common peroneal nerve and careful shaping of the tibial remnant. Cortical bone formed at the transection level allowing total contact prosthetic fitting with some end bearing. BK amputation is described as optimally 12.5 centimeters to 17.5 centimeters below the knee joint (10 to 12.5 centimeters in vascular disease). Saving the knee should always be considered and with combined surgical and prosthetic skill a stump as short as five centimeters may be fitted satisfactorily particularly in the young and following trauma

Summary Statement. Using a weight-bearing force control task, age-related changes in muscle action were observed in osteoarthritic subjects, however, greater activation of rectus femoris and medial hamstring muscles in the OA group compared to control indicates greater cocontraction and varied stabilisation strategies. Introduction. Osteoarthritis (OA) is the most debilitating condition among older adults. OA is thought to be mechanically driven by altering the stabilising integrity of the joint. The main contributor to knee joint stability is that of muscular contraction. In cases where the history of a traumatic knee joint injury is not a causal factor, a change in muscle function, resulting in reduced strength and force control in believed to induce OA development and progression. Since age is also a determining factor of OA, the purpose of this study was to investigate the muscle activation patterns of young healthy adults (YC), older healthy adults (OC), and adults with OA during a standing isometric force control task. Patients & Methods. A force matching protocol was used to evaluate muscle activation patterns of 41 YC (23.1±1.9 years of age) 18 OC (59.7±5.14 years), and 19 OA (63.5±8.1 years). Subjects stood with their leg of interest fixed to a force platform and modulated ground reaction forces while exposing equal body weight to each leg. Surface electromyography (EMG) of 8 muscles that cross the knee joint, kinetics and kinematics were recorded while subjects generated 30% of their maximal force in 12 different directions, corresponding to various combinations of medial-lateral-anterior-posterior ground reaction forces. Processed EMG was normalised to previously recorded maximum voluntary isometric contraction (MVIC) and ensemble averaged into group means for each loading direction. Muscle activation patterns were displayed in EMG polar plots and were quantified with symmetry analyses, mean activation levels (X. EMG. ), directions (Φ), and specificity indices (SI). Group differences were tested with independent T-tests at the p<0.05 level. Results. Muscle activation patterns were similar between groups (i.e. symmetry and Φ). However, X. EMG. of 7 muscles was significantly greater in both the OA and OC groups compared to YC. OA group also demonstrated significantly greater X. EMG. in the rectus femoris and tensor fascia lata as well as lower SI in semitendinosus hamstrings compared to OC. Discussion/Conclusion. Our results indicate that regardless of loading direction, both OC and OA groups have greater levels of muscle co-contraction than YC. This is suggested to be an adaptive response to age-related changes in muscle strength and force control. Since individuals with OA have reduced muscle strength and force control compared to age-matched controls, our results suggest that the OA group's greater, less specific activation of knee joint muscles relative to the OC is this “stiffening” response adapted by the OA group, however, to an extent that may expose the joint to detrimental loading conditions, contributing to the progression of OA. Further investigation regarding age-related neuromuscular changes and their influence on joint loading conditions and development of OA is warranted

Aims

To evaluate inducing osteoarthritis (OA) by surgical destabilization of the medial meniscus (DMM) in mice with and without a stereomicroscope.

Aims: Retrospective study comparing long term results after excision of osteochondral defects of the knee joint in different age groups. Methods: Fiftytwo patients with osteochondritis dissecans lesions were evaluated between 7 and 25 years after excision of a partially detached or loose fragment from the medial femoral condyles. Average follow-up was 17,2(range 7–25 years). Two groups with the same defect size and activity level during procedures were made, with 31 patients in þrst and 21 Ð in the second group. The only difference between the groups was the age; the age average in the þrst group was Ð 25,6 years (range 15 to 35 years), and Ð 45,2 years (range 35 to 55 years) in the second group. Patients were evaluated through ICRS, modiþed HSS and KOOS scales, and with x-rays. Results: Evaluation with the ICRS, modiþed HSS and KOOS rating scales for osteochondritis dissecans revealed Ð 9(17%) good results, 32(62%) Ð fair, and 11(21%) Ð failure results. Final ICRS and modiþed HSS evaluation showed statistically signiþcantly better results in the younger patients group at the 21 years (p< 0.04). At an average 17,2 year follow-up x-rays and KOOS evaluation form showed initial and second-degree (according to AhlbŠck) osteoarthritis signs in the knees. Conclusions: The long-term results of the excision of osteochondral defects of the knee joint are poor. We recommend autologous osteochondral grafting for the replacement of the osteochondritis dissecans defects in the knee joint

The introduction of unicondylar knee prostheses has allowed the preservation of the non-diseased compartment of the knee whilst replacing the diseased or damaged compartment. However, as is well known, there is concern that the body’s biological reaction to ultra-high molecular weight polyethylene (UHMWPE) wear particles leads to bone resorption and subsequent loosening and failure of the joint. Also, in some cases, delamination of the UHMWPE tibial bearing surface has been found to occur leading to failure of these conventional joints. Therefore new material combinations have been investigated within the laboratory. The unicondylar knee that was tested consisted of CoCrMo tibial and femoral components between which a mobile Pitch-based carbon fibre reinforced polyetheretherketone (CFR-PEEK OPTIMA®) meniscal bearing was mounted. The joints were supplied by INVIBIO Ltd. Tribological tests were performed on these knees using the Durham six station knee wear simulator and the Durham friction simulator II. In both cases the loading and motion were similar to the standard walking cycle. On the six station wear machine five stations applied both the loading and motion and were the active stations and one applied loading only as it was used as the loaded soak control station. Approximately every 500,000 cycles, the wear of the CFR-PEEK meniscal bearings was assessed gravimetrically (using a Mettler Toledo AX 205 balance, accurate to 0.01 mg) and the loaded soak control was used to take account of any change in weight due to lubricant absorption. The joints were tested to five million cycles (equivalent to approximately five years in vivo) with diluted new-born calf serum as the lubricant which gave a protein content of 17 gl-1. At periods throughout the wear test the surface topography was measured on the Zygo NewView 100 non-contacting profilometer. Friction tests were performed at the beginning and the end of the wear test. The average volumetric wear rate of the medial and lateral components was found to be 1.70 and 1.02 mm3/million cycles respectively (range 0.66 – 2.73 and 0.59 – 2.45 mm3/million cycles respectively). This is lower than the reported wear rate of metal-on-UHMWPE unicondylar knee joints (6.69 and 2.98 mm3/million cycles for the medial and lateral components respectively) [. 1. ]. The surface topographical analysis of the CFR-PEEK bearings showed a reduction in surface roughness and also a change to more negative skewness (i.e. more valleys than peaks) which may aid in lubrication. Before and after wear testing the joints were found to be operating in the boundary/mixed lubrication regime. The Pitch-based CFR-PEEK unicondylar knee joints performed well in these wear tests. They gave lower volumetric wear rates than metal-on-UHMWPE uni-condylar knee prostheses. The friction tests showed that at physiological viscosities, these joints operate in the boundary/mixed lubrication regime. These results show that this novel joint couple may potentially be an alternative solution for the reduction of wear and osteolysis. The authors wish to thank INVIBIO Ltd for funding this research

Aims

Accurate skeletal age and final adult height prediction methods in paediatric orthopaedics are crucial for determining optimal timing of growth-guiding interventions and minimizing complications in treatments of various conditions. This study aimed to evaluate the accuracy of final adult height predictions using the central peak height (CPH) method with long leg X-rays and four different multiplier tables.

Aims

Periprosthetic hip and knee infection remains one of the most severe complications following arthroplasty, with an incidence between 0.5% to 1%. This study compares the outcomes of revision surgery for periprosthetic joint infection (PJI) following hip and knee arthroplasty prior to and after implementation of a specialist PJI multidisciplinary team (MDT).

1. The technique of compression-arthrodesis of the knee joint is described. 2. Fifteen consecutive cases are reported in which clinical union was detected at the first inspection from twelve days to six weeks after operation. By this method the total period of disability is reduced to three months. 3. Three mechanical factors which might be responsible for this very early clinical union are examined: compression is believed to be the main factor, although fixation is also important. 4. A fallacy is exposed in the use of bone grafts for arthrodesis of the knee; the graft is less osteogenic than the substance of the bones which form the joint, and it provides inefficient internal fixation. 5. A theory is suggested that compression, even in the presence of slight movement, acts by producing a fixed "hinge" without shearing movement; at this point a bridgehead of flexible osteoid tissue is established in which ossification inevitably takes place despite slight bending movement. 6. A second theory is suggested that high compression forces stimulate early union by liberating bone salts at points of maximum pressure through the action of osteoclasts, and that the local excess of bone salts is redeposited under cellular activity within a range of a few millimetres where there is no pressure

Purpose of the study: Mycetoma designates an inflammatory pseudotumour caused by fungal or bacterial agents with a slow chronic course and characterised by the emission of species-specific grains through fistules. Like the foot, the knee is a weight-bearing zone which can lead to mycetoma of soft tissue and/or bone or articular tissue. The purpose of this work was to study the frequency of the different clinical forms and report medical and surgical outcomes of the localisation. Material and methods: This was a retrospective analysis of consecutive files collected over a 20-year period from July 1988 to 2008 including a total of 267 cases. Twentyfive patients (22 male 3 female) had an articular or peri-articular mycetoma of the knee joint. Mean age was 31.8 years (range 18–59). The right knee was involved in 17 cases and the left in eight. Duration of symptoms was 2.2 years (range 1–25 years). Antibacterial treatment with sulfamethoxazole and exclusively for actinomycetoma was given for 10 months at least and antifungal treatment with ketoconazole as adjuvant treatment with surgery for maduromycetomas. This orthopaedic surgery was radical (three above-knee amputations) or conservative (directed healing for 5, first-intention surgery for 5 with a flap for 3 and with a graft for the others). Results: The knee accounted for 9.23% of the localizations in our series, most common after the foot and ankle. Twenty cases were exclusively maduromycetomas with black grains; the five others were actinomycetomas: 3 red grain, 1 white grain and 1 yellow grain. The topographic forms were predominantly anterior localization: 15 cases (versus popliteal in two, the entire knee in four and unknown in four). According to the Bouffard classification, the lesions were: diffuse (n=20), polyfisutulised (n=20), sclerohypertrophic (n=1) versus two localized encapsulated forms. Local spread led to bone and joint involvement in six patients, mycosis arthritis in three complicated by a pathological fracture of the patella. At last follow-up, there have been three recurrences with limited flexion in four patients. Discussion: Articular or extra-articular mycetoma of the knee is an infectious dermato-orthopaedic disease dominated by fungal infection. Treatment is particularly difficult in advanced stage disease, medical and surgical management can be proposed with cancerological type resection

14.1% of men & 22.8% of women over 45 years show symptoms of osteoarthritis OA of the knee [. 1. ]. Knee OA is usually associated with lower limb malalignment [. 2. ]; 50 of varus results in 70% −90% increase in compressive loading of the medial tibio-femoral compartment [. 3. ] and OA worsening over 18 months [. 4. ]. High Tibial Osteotomy (HTO) enables preservation of bone stock and soft tissue structures and could be an attractive option to younger patients who wish to return to high level activity. However, results of HTOs are unpredictable, which could be due to patient selection or surgical techniques. The long-term aim of this work is to develop a predictive tool to aid the surgeon in the selection of optimal HTO geometry for improved and more consistent surgical outcomes. The first step in achieving our longterm goal was to determine whether stress predictions at the tibio-femoral articulation were sensitive to simulated high tibial osteotomy, using finite element (FE) method. CT and MRI data of a cadaveric knee were used to create geometrically accurate 3D models of the femur, tibia, fibula, menisci and cartilage and tendon of the knee joint, using the Mimics V12.11 commercially-available software (Materialise, Belgium). The Simulation module was used to register the bones and the soft tissues. The resulting STL files were exported to CATIA V5R18 pre-processor to generate surface meshes and create the corresponding 3D solid and FE models of the osseous and soft tissues from the STL cloud of points. The Young’s moduli for cortical bone, cancellous bone, cartilages, menisci and ligaments were taken from literature as 17 GPa, 500 MPa, 12 MPa, 60 Mpa and 1.72 MPa respectively [. 5. ,. 6. ,. 7. ]. The Poisson’s ratios for osseous and soft tissues were taken as 0.3 and 0.45, respectively [. 8. ]. The nodes between the bones and the corresponding cartilages were merged and surface contact was applied between the cartilages. The distal ends of the tibia and fibula were fixed and a load of 2.1 KN, corresponding to 3 x body weight, was applied perpendicularly to the proximal end of the femur. Results of finite element analyses show a reduction of 67 % in principal stresses in the knee joint following an open wedge HTO surgery simulating 100 varus correction. FE analysis results of this study show that HTO reduces stresses in specific regions of the knee, which are associated with OA progression [. 4. ]. Our future works include corroborating our results with controlled cadaveric experiments and implementing optimization techniques to predict optimum HTO geometries for patient-specific FE models

It has been proposed that higher knee adduction moments and associated malalignment in subjects with severe medial knee joint osteoarthritis (OA) is due to anatomical deformities as a result of OA [1, 2]. The emergence of patient-matched implants should allow for correction of any existing malalignment. Currently the plans for such surgeries are often based on three dimensional supine computed tomography (CT) scans or magnetic resonance imaging (MRI), which may not be representative of malalignment during functional loading. We investigated differences in frontal plane alignment in control subjects and subjects with severe knee joint OA who had undergone both supine imaging and gait analysis. Fifteen subjects with severe knee OA, affecting either the medial or lateral compartment, and 18 control subjects were selected from a database established as part of a larger study. All subjects had undergone gait analysis using the Vicon motion capture system. OA subjects had undergone routine CT scans and were scheduled for knee joint replacement surgery. Control subjects had no known musculoskeletal conditions and had undergone MRI imaging of hip, knee and ankle joints. Frontal plane knee joint angles were measured from supine imaging (supine) and from motion capture during standing (static) and during gait at the first peak ground reaction force (gait). OA subjects had a significantly higher BMI (p < 0.01) and different gender composition (13 males and 2 females vs 4 males and 5 females; p = 0.03) compared with controls. Multiple linear regression analysis indicated no significant confounding effect of these differences on frontal plane angles measured in supine, static or gait conditions. For both OA and healthy subjects, frontal plane knee angles were significantly higher during gait compared with supine (p = 0.03 and 0.02, respectively). There were also significant differences in knee alignment between OA and healthy subjects for supine and static (p < 0.05) but not for gait, although this was approaching significance (p = 0.052). Overall there seemed to be higher variation in alignment in the OA subjects (Fig. 1). The significantly higher frontal plane knee joint angles measured in both control and OA subjects during gait compared with supine imaging indicate that functional alignment should be taken into consideration when planning patient-specific surgeries. Higher variation in OA patients may be due to alterations in gait patterns due to pain or degree of wear in their osteoarthritic joints, and requires further investigation. In addition, methodological considerations should be taken when comparing alignment from measurements taken with imaging and motion capture to avoid systematic errors in the data. In conclusion, we believe that both supine and loadbearing imaging are insufficient to gain a full representation of functional alignment, and analysis of functional alignment should be routinely performed for optimal surgical planning

The use of 3D imaging methodologies in orthopaedics has allowed the introduction of new technologies, such as the design of patient-specific implants or surgical instrumentation. This has introduced the need for high accuracy, in addition to a correct diagnosis. Until recently, little was known about the accuracy of MR imaging to reconstruct 3D models of the skeletal anatomy. This study was conducted to quantify the accuracy of MRI-based segmentation of the knee joint. Nine knees of unfixed human cadavers were used to compare the accuracy of MR imaging to an optical scan. MR images of the specimens were obtained with a 1.5T clinical MRI scanner (GE Signa HDxt), using a slice thickness of 2 mm and a pixel size of 0.39 mm × 0.39 mm. Manual segmentation of the images was done using Mimics® (Materialise NV, Leuven, Belgium). The specimens were cleaned using an acetone treatment to remove soft-tissue but to keep the cartilage intact. The cleaned bones were optically scanned using a white-light optical scanner (ATOS II by GOM mbH, Braunschweig, Germany) having a resolution of 1.2 million pixels per measuring volume, yielding an accuracy of 0.02 mm. The optical scan of each bone reflects the actual dimensions of the bone and is considered as a ground truth measurement. First, a registration of the optical scan and the MRI-based 3D reconstruction was performed. Then, the optical scan was compared to the 3D model of the bone by calculating the distance of the vertices of the optical scan to the reconstructed 3D object. Comparison of the 3D reconstruction using MRI images and the optical scans resulted in an average absolute error of 0.67 mm (± 0.52 mm standard deviation) for segmentation of the cartilage surface, with an RMS value of circa twice the pixel size. Segmenting the bone surface resulted in an average absolute error of 0.42 mm (± 0.38 mm standard deviation) and an RMS error of 1.5 times the pixel size. This accuracy is higher than reported previously by White, who compared MRI and CT imaging by looking at the positioning of landmarks on 3D printed models of the segmented images using a calliper [White, 2008]. They reported an average accuracy of 2.15 mm (± 2.44 mm) on bone using MRI images. In comparison, Rathnayaka compared both CT- and MRI-based 3D models to measurements of the real bone using a mechanical contact scanner [Rathnayaka, 2012]. They listed an accuracy of 0.23 mm for MRI segmentation using five ovine limbs. This study is one of the first to report on the segmentation accuracy of MRI technology on knee cartilage, using human specimens and a clinical scanning protocol. The results found for both bone and cartilage segmentation demonstrate the feasibility of accurate 3D reconstructions of the knee using MRI technology

Query: The means for treating Osteochondrosis dissecans (OD) of the knee joint in adolescents remains today a matter of controversial discussion. Not only the different treatments, whether purely conservative or one of the various surgical procedures, are rated differently with respect to their benefit, but also the question of the right time to operate is not easy to answer. The objective of this prospective study was to examine the long-term results of a bioabsorbable fixation system in the treatment of OD and to determine possible relationships between the baseline conditions, such as stage of disease, patient’s age, severity or localization and the results in each case. Method: Between 1995 and 2005, 312 patients aged 7 to 19 years with Osteochondrosis dissecans were treated by means of arthroscopic operation on the knee joint. In 257, fixation using ethipins could be performed, the dissecate had to be removed in 31 patients. An MRT was performed preoperative in all patients, the knee joint function, activity level and patient’s quality of life were evaluated postoperative using the modified Cincinnati Score, the Tegner Activity Index and the Lysholm Score. Results: 255 of the 312 patients were available to follow-up over a longer period (Ø 7.9 years). The Lysholm Score for all patients 5 years after surgery was 87.6 points, after 10 years 76.5. Classified by baseline stage, it was found that the postoperative course was clearly better in those patients in whom fixation was required. Moreover, an early stage of OD and younger patient age were prognostically favorable factors. The MRT follow-up examination showed re-integrated vital cartilage areas without signs of fixation residuals in patients in whom fixation was performed. Conclusion: Surgical treatment of Osteochondrosis dissecans brings different results depending on the stage of the disease. Moreover the results depend on patients age, location of the defect, duration of symptoms. If fixation of the dissecate using bioabsorbable pins is successful, the long-term results achieved are good to excellent. Overall, the data obtained justify an early decision for a surgical procedure in the treatment of Osteochondrosis dissecans of the knee joint in children and adolescents

Aims: The extensor contracture of the knee joint happens in the case of external þxation of low femoral fractures nearly in 100% of cases. This complication appears due to the þxation of soft tissues (skin, fascia, muscles) to the bone with transosseous elements Ð K-wires and S-screws. Methods: We have performed the Òlay-to-layÒ deþnition of soft tissue displacement (skin-fascia-muscles) relative to femoral bone during knee joint ßexion 90/0/0 using 15 human cadavers. The femur was divided into 17 proportional segments. The co-ordinate system included 12 positions in each segment. Results: Our data revealed that the minimal soft tissue displacement was seen in 4th and 8th positions at each tested level (0–5mm). In the positions 3 and 9 the indices were worse (4–10mm). It was stated that most of all the muscles were displaced, the skin was less displaced, and the displacement of fascia was the least. In the projection of the found positions the vessels and nerves are absent. Using the ÒMethod of Uniþed Designation of External FixationÒ (see . www.aotrf.org. , the chapter ÒFor the orthopedic surgeonsÒ) the possible variant of arrangement of the distal support can be represented by the following way: VII,4,110;VII,8,110;VIII, 3Ð9 or VII,9-3;VII,8,110;VIII, 3Ð9.Conclusions: The data of the experimental test were used during the treatment of 9 patients. During the whole period of þxation in the device the range of motions in the knee joint was from 80/0/0 to 110/0/0. After the dismantling of the device the whole range of motions was achieved in 2–3 weeks. There were no cases of soft tissue inßammation in the zone of exit of transosseous elements of the distal support

We report a prospective study of gait and tibial component migration in 45 patients with osteoarthritis treated by total knee arthroplasty (TKA). Migration was measured over two years using roentgen stereophotogrammetry. We used the previously established threshold of 200 μm migration in the second postoperative year to distinguish two groups: a risk group of 15 patients and a stable group of 28 patients. We performed gait analysis before operation and at six months and at two years after TKA. On all three occasions we found significant differences between the two groups in the mean sagittal plane moments of the knee joint. The risk group walked with higher peak flexion moments than the stable group. The two groups were not discriminated by any clinical or radiological criteria or other gait characteristics. The relationship which we have found between gait with increased flexion moments and risk of tibial component loosening warrants further study as regards the aetiology of prosthetic loosening and possible methods of influencing its incidence

Background. Infected total knee arthroplasties present in a variety of different clinical settings. With severe local compromise and draining sinus tract around the knee, after adequate debridement, the resultant patellectomy with need for free muscle transfer and split thickness skin graft for closure, usually results in loss of quadriceps function. This necessitates the need for drop lock brace. No good mechanisms are available for reconstruction of large anterior defects in total infected total knees where this occurs. Questions. Can proximal placement of the knee joint with longer tibial segments aid in closure in patients with large anterior skin defects, and can this placement aid in quadriceps reconstruction to alleviate the need for drop lock braces while ambulating?. Methodology. 10 patients with 2 year follow-up with stage III-C-3 McPherson infected total knees presented with large soft tissue defects over the anterior aspect of the knee with sinus tract and scarring from multiple surgeries. The patients underwent a one stage treatment of the infected total joint. 4 required a free muscle flap and split thickness skin graft. Patellectomy with some quadriceps resection was required in the debridement process. Distal femur and proximal tibial replacements were performed with proximal placement of the knee joint. The patients were analyzed for extension control in gait and soft tissue closure over the operational knee joint. The quadraceps mechanism was over attached to the proximal tibial component. Results. Of 10 with 2 year follow up, none recurred with infection. There was no erosion of the soft tissue over the knee joint commonly seen in free flaps directly over the joint in these type of resection –replacements. 50% of the patients had enough extensor use to walk with a cane or walker as opposed to needing a drop lock knee brace. Discussion. Proximal placement of the knee joints in patients with large anterior soft tissue defects may lessen need for free flaps and provide for extension to lock hinges. Conclusion. Proximal placement of the total knee in case of infected total knees with large anterior soft tissue defect, provides for more quadriceps function and soft tissue coverage and lessened the need for free flaps

We describe the natural history of a rabbit knee model of permanent post-traumatic joint contractures. Twenty-four skeletally mature female NZW rabbits had five-mm-squares of cortical bone removed from both femoral condyles. An extra-articular K-wire immobilized the knee joint in flexion. The K-wire was removed eight weeks later and the rabbits were divided into four groups depending on the remobilization time. The average extension loss for the experimental knees in the zero, eight, sixteen and thirty-two weeks remobilization groups was thirty-eight, thirty-two, twenty-one and twenty degrees, respectively. The motion loss stabilized in the later time intervals suggesting permanent contractures had developed. The contralateral unoperated knees average extension loss was nine degrees. The purpose of this study was to develop a rabbit knee model of post-traumatic contractures. A simulated intra-articular fracture plus eight weeks of immobilization leads to a permanent joint contracture even after thirty-two weeks of remobilization. This animal model of human post-traumatic joint contractures will allow further studies investigating mechanisms underlying the process. Twenty-four skeletally mature female NZW rabbits had 5 mm squares of cortical bone removed from both femoral condyles. An extra-articular Kirschner wire (K-wire) immobilized the knee in flexion. A second operation was performed eight weeks later to remove the K-wire. The rabbits were divided into four groups. Hind limbs were dissected, preserving the joint capsule. A device allowing six degrees-of-freedom coupled to a material testing system which applied a 0.2 Nm torque measured joint angles. Statistical analysis was performed using ANOVA with a posthoc Student-Newman-Keuls test. Data are presented as mean ± SD. The loss of extension for the experimental knees in the zero and eight weeks remobilization groups was significantly greater than the values of all contralateral unoperated knees. The loss of extension for the experimental knees in the sixteen and thirty-two weeks remobilization groups was also greater than the contralateral knees, although it was not statistically significant (p = 0.07). With this model, the severity of the contracture decreased with time of remobilization. However, the degree of contracture stabilized between sixteen and thirty-two weeks of remobilization, suggesting that the joints had developed a permanent contracture. This mimics the human scenario of permanent post-traumatic joint contractures. Funding: has not been received from a commercial party. This work was supported by The Alberta Heritage Foundation for Medical Research. Please contact author for tables and/or graphs

Measures of lower limb alignment and knee joint load during walking were evaluated before and six months after medial opening wedge high tibial osteotomy (HTO) in ninety-five patients with knee medial compartment osteoarthritis (OA). Full-length standing radiographs were used to calculate the mechanical axis angle, and a gait analysis was performed to calculate the external adduction moment about the knee. Results indicated significant decreases in mechanical axis angle and peak adduction moment. These findings provide an indication of the early success of HTO in reducing the extent of lower limb malalignment and knee joint load during walking. Medial opening wedge high tibial osteotomy (HTO) is intended to correct lower limb malalignment, resulting in decreased medial knee joint load and improved function. Due to the potential for the amount of alignment correction to change over time after surgery, frequent follow-up evaluations are encouraged. To evaluate the early changes in lower limb alignment and medial knee joint load experienced during walking after medial opening wedge HTO. Ninety-five patients (seventy-nine males, sixteen females; age range = 21–76 years; BMI range = 18.0–38.5) with knee joint OA affecting primarily the medial compartment underwent radiographic and gait analyses pre-surgically and six months following HTO. Full-length standing radiographs were obtained on both occasions and used to measure the static mechanical axis angle. Three-dimensional kinetic and kinematic data were also collected and combined to calculate the external knee joint adduction moment, an indirect measure of knee joint load. Paired t-tests indicated the mechanical axis angle (mean decrease = 8.32 degrees, 95% CI = 7.54,9.10) and peak external knee joint adduction moment (mean decrease = 1.61%BW*ht, 95% CI = 1.25,1.95) significantly decreased post-operatively (p< 0.001). These results indicate less varus angulation and reduced medial knee joint load following HTO. These preliminary findings suggest that medial opening wedge HTO is an effective surgical treatment for improving alignment and reducing knee joint load. Although these early results are promising, future research is required to determine the long-term success of this surgery in the treatment of knee OA. Funding:. CIHR, NSERC, Arthrex Inc

Query: The treatment of discrete but advanced cartilage damage to the knee joint, such as in osteonecrosis in patients older than 45 years, has not been satisfactorily resolved to date. The objective of this prospective study was to investigate the utility of a minimally-invasive unicondylar surface replacement system and to record the first clinically-obtained results. Method: We are reporting on the results of the first 19 operations of discrete knee joint defects performed in our clinic since October 2004 using the Arthrosurface System. The Arthrosurface System consists of specially-preformed convex implantate dowels and an adapted integrative fraise system for handling the femurcondylus. The knee joint function, the activity level and the patient’s quality of life were evaluated pre–and postoperative using the Knee Society Score, the Tegner Activity Index and the Lysholm Score. Results: In the operating room, the system was impressive in its utility. No implantate-related complications have occurred in the short follow-up time thus far. In the early postoperative phase, the patients achieved rapid increase in their activity level which paralleled the reduction in pain relief attained. Conclusion: The Arthrosurface. ®. System shows beneficial properties for treating localized but advanced cartilage damage to the knee joint of patients older than 45 years of age. In particular, it enables arthroscopically-supported minimally-invasive implantation. Intact structures are thus not damaged and the patient rehabilitation is rapid

Previous research suggests knee joint moments and muscle activity during walking are altered in patients with anterior cruciate ligament (ACL) deficiency and in patients with medial compartment knee osteoarthritis (OA). The objective of this study was to compare knee joint flexion and adduction moments and the extent of quadriceps-hamstring muscle co-contraction before and one year after combined simultaneous ACL reconstruction and high tibial osteotomy (HTO). Eighteen patients (three females, fifteen males; age = 40 ± 8 yrs.; BMI = 28.8 ± 5.77) with ACL deficiency and OA affecting primarily the medial compartment of the knee underwent ACL reconstruction (hamstring autograft) and medial opening wedge HTO procedures during a single operation. All patients completed pre-operative and one-year postoperative quantitative gait assessments. Three-dimensional kinetic and kinematic data were collected during self-paced walking and used to calculate the peak external flexion and adduction moments about the knee. Electromyographic (EMG) activity was collected from the hamstrings and quadriceps and used to calculate the co-contraction ratio. Peak moments and co-contraction ratios were compared pre and postoperatively using paired t-tests. The peak knee flexion moment decreased from 2.31 ± 1.14 to 1.33 ± 0.73 %BW*ht (p=0.001); mean decrease = 0.98 %BW*ht (95%CI: 0.49–1.47). The peak knee adduction moment decreased from 2.81 ± 0.62 to 1.69 ± 0.61 %BW*ht (p< 0.001); mean decrease = 1.12 %BW*ht (95% CI: 0.80–1.43). The quadriceps-hamstring co-contraction ratio decreased from 0.82 ± 0.14 to 0.72 ± 0.18 (p=0.056); mean decrease = 0.10 (95% CI: −0.003 – 0.21). The present findings suggest that combined simultaneous ACL reconstruction and HTO significantly decreases knee flexion and adduction moments during walking. Although the present findings suggest that the quadriceps-hamstring co-contraction ratio also decreases, future research with more patients is required to confidently evaluate potential changes in muscle activity. These findings are consistent with an overall reduction in dynamic knee joint load

Purpose: To define the role of ACI in treatment of cartilage defects in the knee joint. Method: 106 articular cartilage defects in 79 knees of 77 patients were treated by ACI as described by Brittberg et al, 1994. 43.5% of the lesions involved the patella, 35.2% the femoral condyles, 16.7% the trochlea, and 4.6% the tibial condyles. 20% of knees had more than one defect. Associated biomechanical procedures were carried out in 88.7%. Results: 70 lesions in 58 knees and 56 patients were assessed arthroscopically 9 months after implantation; 4 eligible patients were not assessed. The average ICRS repair score (maximum 12) was as follows: tibial condyle 11.5, (4 defects); patella 11.3, (32 defects); femoral condyle 11.0, (23 defects) and trochlea 10.7, (11 defects). Synovitis was markedly reduced in all knees with well healed defects. Contraindications to ACI in this series were:. Non-contained defects,. Bi-polar lesions,. Patients greater than 45 years,. Uncorrected biomechanics,. Regional pain syndrome type 1,. Limited joint movement,. Defective subchondral bone plate. Conclusion: ACI effectively repairs articular cartilage defects in the knee joint, provided that the contraindications are recognised. Unlike other series, the results for the patella, patellofemoral joint have matched those for the femoral condyle. This is attributed to the simultaneous biomechanical correction of the patellofemoral joint. Stabilisation of the articular surface results in resolution of synovitis

Pigmented villonodular synovitis is a monoarticular proliferative process most commonly involving the synovium of the knee joint. There is considerable debate with regards to diagnosis and effective treatment. We present our experience of managing PVNS of the knee joint over a 12 year period. Twenty-eight patients were reviewed. MRI was used to establish recurrence in symptomatic patients rather than routine screening and to identify posterior disease prior to surgery. Eight patients had localised disease and were all treated with open synovectomy and excision of the lesion, with no evidence of recurrence. Twenty patients had diffuse disease, eight treated arthroscopically and twelve with open total synovectomy. Nineteen patients (95%) had recurrence on MRI, however, only five (25%) had evidence of clinical recurrence. There were no significant complications following arthroscopic synovectomy. Open synovectomy, in contrast, was associated with three wound infections and two thrombo-embolisms. Three patients had Complex regional pain syndrome. We believe diffuse disease should be treated with arthroscopic synovectomy which is associated with minimal morbidity and can be repeated to maintain disease control. Radiotherapy is helpful in very aggressive cases. TKR was used when there was associated articular erosion

Introduction and Aims: To study the natural history of the bone bruising of the knee and to identify the effect of weight-bearing and associated internal derangement on clinical improvement and radiological progress of the bone bruising of the knee. Method: Patients with an acute knee injury were prospectively subjected to clinical and MRI examination within 48 hours of injury. Patients with osteoarthritis, bleeding disorder and previous injury or surgery to the injured knee were excluded. Internal derangement of the knee joint was identified. Patients with bone bruising (study group) were randomised into weight-bearing and non weight-bearing groups and followed-up for clinical and MRI examination at six weeks, three months, six months and 12 months. At follow-up, bone bruising on MRI was classified as Progressive, Static, Resolving or Resolved. Patients without bone bruising (control group) were similarly followed up for clinical examination. Lyshom score was used for clinical assessment. Results: 28 patients were available for the follow-up. Average age was 24. There were eight patients in control group and 10 patients each in weight-bearing and non weight-bearing group. Eleven patients had associated internal derangement of the knee joint. Clinical improvement was better in the control group compared to the study group. Patients with isolated bone bruising were doing better than those with associated internal derangement. On radiological examination there was tendency for the bone bruise to progress in the first six weeks but majority started resolving by three months time. All isolated BB were resolved by six months, but there was delayed resolution of BB associated with ID. Weight-bearing status did not influence clinical or radiological course of bone bruising. Conclusion: Weight bearing does not alter the course of the bone bruising. Internal derangement associated with bone bruising delayed radiological resolution and clinical improvement of the patient

In terms of function, range of movement is an important measure of outcome. The purpose of this study was to determine whether or not stripping the capsule of the distal femur at the time of primary total knee arthroplasty had a significant effect on the range of knee movement achieved at the end of the operation. An improvement of 5 degrees or more was considered significant. One hundred and twenty-five patients (47 males; 78 females) presenting for primary total knee arthroplasty were recruited. All operations were performed by the senior author using the LCS rotating platform system without patellar resurfacing. Preoperatively, the tip of the greater trochanter, the lateral femoral epicondyle and the anterior border of the lateral malleolus were marked. Using a digital camera, images of the limb proposed for surgery were taken with the knee in extension, forced extension, flexion and forced flexion. Camera set up was standardised for all photographs. Using a random numbers program, patients were randomised either to have release of the posterior knee joint capsule or not. The surgeon was informed at the time of the operation. At the end of the procedure the digital images were repeated. Total arc of knee movement preoperatively ranged from 41° to 161° (average, 115°). Postoperatively, this varied from 95° to 157° (average, 124°). Average arc of knee movement was 125° for the no release group and 123° for the released group. Of the 78 patients where the increase in total arc of knee motion was significant, 41 had been released and 37 had not. No statistically significant difference was noted. In conclusion, we report that releasing the posterior capsule of the knee joint routinely during primary total knee arthroplasty conveys no significant advantage in terms of the range of knee motion achieved immediately following surgery. Consequently, it is unlikely to increase the long-term range of movement

We describe a new method of reconstruction of the extensor apparatus after extensive resection of malignant tumours around the knee joint with a polyester ligament. Twenty- two patients after a mean follow up of eighteen months (six to thirty-six months) were treated. Six patients had excellent knee function with a lag of extension less than five degrees, four of less than twenty, three had less than forty degrees and six patients could not lift their limb extended against gravity, although no patient required any kind of walking aid. The mean Enneking Score was 81.5 the mean TESS Score was eighty-three. Limb salvage surgery in primary malignant bone tumours is widely accepted as the surgical treatment of choice around the knee joint. Extraarticular resection for oncological radicality usually results in additional resection of at least part of the extensor mechanism. Since January 2000 we used a Polyester Band (LARS®) for either augmentation of a transposed muscle or as a complete soft tissue bridging after tumour resection in twenty-two patients (fourteen men, eight women) with a mean age of thirty-two (8–75). The HMRS tumour endoprosthesis was used for the reconstruction of the knee joint. The location of the tumour was in the distal femur in ten cases and the proximal tibia in eleven. One synovial sarcoma arose at the lateral meniscus. The mean follow up was eighteen months (6–36) after implantation of the Lars® ligament. Patient’s functional outcome and satisfaction was eighty-three (65–92) at the TESS Score and 81,5 (43–92) at the Enneking Score, respectively. Six patients had excellent knee function with an extension deficit of less than five degrees. In four cases the extension deficit was less than twenty, in three cases it was less than forty. In six patients the active extension lag was more than forty degrees. However, their remaining quadriceps strength was sufficient for stabilisation of the knee joint during gait without any aids. At last follow up all implants were in situ without any signs of loosening. No patient had to be amputated because of septic complication

Introduction: Reports on nerve injury after arthroscopic ACL reconstruction using hamstring tendon autograft had mainly focused on injury to the infrapatellar branch of the saphenous nerve (IPBSN), with few reports on injury of the sartorial branch of the saphenous nerve (SBSN). Aim of the work: was to define the level of anatomical termination of the saphenous nerve in relation to knee joint level and the relation of its sartorial branch to the surrounding tendons so that it could be avoided during hamstring tendon harvesting. Materials and Methods: This anatomical study included cadaveric dissection of the medial aspect of the knee joint of 25 preserved knees. The saphenous nerve was dissected proximal to the knee joint and followed distally till it was divided into its two terminal branches. Results: In 68 %, the saphenous nerve gave its two terminal branches at a mean distance of 8 cm above the knee joint line. In 32 %, the level of termination of the saphenous nerve was below the knee joint line by a mean distance of 3 cm. In 92 % the saphenous nerve or the SBSN was passing posterior to the sartorius tendon by a mean distance of 19.8 mm. In 68 % the saphenous nerve or the SBSN continued distally anterior to the gracilis tendon, while in 16 % the SBSN continued distally posterior to the gracilis tendon. In 20 % the distance between the saphenous nerve or the SBSN and gracilis tendon was 5 mm or less. In 12 % the saphenous nerve or the SBSN was lying directly anterior to the gracilis and in 4 %, the SBSN was lying directly behind the gracilis tendon at the knee joint line. In all the knees the saphenous nerve or the SBSN was passing distally anterior to the semitendinosus tendon at a mean distance of 23.1 mm. Conclusion: The saphenous nerve or its terminal branch the SBSN, is at a close anatomical relation with the gracilis tendon. This might predispose the nerve to be damaged during passage of the tendon stripper over the tendon. Clinical correlation: The saphenous nerve or its terminal branch the SBSN, are at a risk of injury during arthroscopic ACL reconstruction using hamstring tendon autograft. The nerve Injury of the saphenous nerve or its terminal branch (SBSN) might be an intrinsic problem associated with the technique itself

Ouery: Matrix-coupled autologous chondrocyte transplantation (MACT) has become increasingly widespread in the therapy of cartilage defects. The objective of this controlled prospective study was to examine the mid-term results of MACT compared to those of Microfracturing (MF) for the treatment of cartilage defects in the knee joint and to determine possible advantages or disadvantages of the two methods. Method: In order to compare the two treatment methods, 40 patients with discrete cartilage defects were treated with MACT and 40 with MF between 4/01 – 4/03. As inclusion criterion, the patients had a chondral defect of at least 1.5 cm and as exclusion criterion, there could be no additional cartilage damage in the other areas of the knee. MRI examinations were performed preoperative (T2 gew. TSE-Sequence, fetts. FLASH-3D) and could be repeated after 6 and 12 months. Knee joint function, the activity level and the patient’s quality of life were evaluated in both groups pre- and postoperative using the modified Cincinnati Score and the Tegner Activity Index. Results: There was significant improvement in the scores used for the study in both the MF group and the MACT group. Comparison of the two groups revealed significantly greater clinical improvement in the MACT patients than in the MF patients (3.8 point increase MACT versus 2.6 point increase MF in the Cincinnati Score). Taking the size extent of the treated cartilage damage into account, there was, however, no relevant difference in defects less than 2,5 qcm. Conclusion: The study could demonstrate that both methods are successful in treating localized cartilage damage in the knee joint. Comparison of the two forms of therapy showed a greater extent of improvement in the MACT group. However, classification by the size of the defect revealed that this effect was relevant only in larger defects, so that the size of the defect should be a decisive criterion for the selection of therapy

Total meniscectomy has been shown to induce osteoarthritic changes in the underlying articular cartilage(AC) and bone in the natural knee (Fairbank 1948; McDermott 2006). This indicates the meniscus plays an important protective role, providing joint congruity and distributing contact forces, hence reducing contact stress. However, no friction and wear studies have been performed on meniscectomy. The aim of this study was to study the tribological response of the medial compartmental natural knee with and without the intact meniscus, under physiological dynamic loading and motion. The effect of normal and reduced loading was investigated. Eighteen month old bovine medial compartmental knees were used. A pendulum friction simulator (Simulation Solutions, UK) was used to apply a dynamic axial loads with peak loads of 1000N (normal) and 260N (reduced). Flexion-extension of amplitude 23degrees was applied and the experiments ran for 3600 cycles at 1Hz. Lubricant was 25% bovine serum in saline. A 9.4 Tesla MRI (Bruker) scanner and Analyze software (Mayo Clinic, US) were used to calculate wear volumes. A surface profilometer (Talysurf, Taylor-Hobson, UK) was used to measure the surface roughness of the specimen before and after the test. Coefficient of friction was found to increase with increased loading, with and without meniscus. With meniscus intact, no wear was found on AC and contact stresses were 4.9MPa and 2.8MPa, for normal and reduced loading respectively. On removal of meniscus, friction was higher at both loading conditions and surface fibrillation found on some of the AC surfaces. Contact stresses rose to 17.2MPa and 8.6MPa for normal and reduced loading. This study has shown for the first time, the direct elevation of the coefficient of friction, immediate surface fibrillation and biomechanical wear of AC upon removal of the meniscus. On removal of meniscus, peak stresses rose and surface damage occurred on AC surfaces. The removal of the meniscus means forces act across smaller areas and contact stresses are increased. Wear is increased due to the subsequent increase in direct solid-solid contact and loss of fluid support due to the unique biphasic nature of AC. This further supports retaining meniscus whenever possible in knee joint surgery

1. In tuberculous disease of the hip, premature epiphysial fusion at the knee joint is due to rupture of the epiphysial cartilaginous plates consequent upon resorption of cancellous support and suppression of osteogenesis. 2. In the tibia, premature fusion is usually preceded by near-central "bulging" of the metaphysial and tibial marrow through the epiphysial plate. In the femur, epiphysial changes preceding fusion are of a fragmentary type. 3. Injury, in quiescent disease, plays little or no part in the causation of premature epiphysial fusion. 4. The factors which are responsible for these changes—local toxaemia and prolonged immobilisation—must exist for not less than two years. 5. In cases which are treated conservatively for long periods the incidence of premature fusion, with serious shortening of the limb, is so high that the wisdom of such treatment must be reconsidered

Aims: Prospective randomized single blind investigation was made to evaluate inßuence of two surgical approaches to the knee (antero-medial approach and subvastus approach) for total knee arthroplasty. Materials: Between 1995– 2002 215 consecutive total knee arthroplasties in 204 patients (192 women, 12 men) were made. There are following prosthesis implanted: PFC Ð 74, GSB Ð 45, PFC ∑ Ð 73, Link Ð 5, AGC Ð 18. All patients were evaluated. Patientsñ mean age was 65,7 years old. TKR with antero-medial approach was performed in 98 cases (45 per cent), whereas TKR with subvastus approach was performed in 117 cases (55 per cent). Methods: Functional status according to HSS scale at the 14 days and 6 months after procedure was regard as end results for both protocols. Results: In group with antero-medial approach there were: 26,4% excellent results, 69,8% good results and 3,8% fair results respectively. In group with subvastus approach there were: 24,3% excellent results, 70,2% good results, 3,3% fair and 2,2% poor results respectively. There are no statistical differences between early functional results of these two surgical approaches for total knee replacement. Conclusions: We assumed that subvastus approach is as good as anteromedial one in knee joint exposure but less harmful for extensor apparatus and joint proprioception

Introduction. Patellofemoral pain and instability can be quantified by using the tibial tuberosity to trochlea groove (TT-TG) distance with more than or equal to 20mm considered pathological requiring surgical correction. Aim of this study is to determine if knee joint rotation angle is predictive of a pathological TT-TG. Methods. One hundred limbs were imaged from the pelvis to the foot using Computer Tomography (CT) scans in 50 patients with patellofemoral pain and instability. The TT-TG distance, femoral version, tibial torsion and knee joint rotation angle ((KJRA) were measured. Limbs were separated into pathological and non-pathological TT-TG. Significant differences in the measured angles between the pathological and non-pathological groups were estimated using the t test. The inter- and intraobserver variability of the measurement was performed. Logistic regression analysis was used to find the best combination of rotational angle predictors for a pathological TT-TG. Results. The intraclass correlation coefficients for inter- and intraobserver variability of the measured parameters was higher than 0.94 for all measurements. A statistically significant difference (P=0.024) was found between the KJRA between the pathological (mean=10.6, SD=7.79 degrees) and the non-pathological group (mean=6.99, SD=5.06 degrees). Logistic regression analysis showed that both femoral version (P=0.03, OR = 0.95) and KJRA (P=0.004, OR=1.15) were, in combination, significant predictors of an abnormal TT-TG. Tibial torsion was not a significant predictor. Conclusion. The KJRA can be used as an alternative measurement when the TT-TG distance cannot be measured as in cases of severe trochlea dysplasia and may act as a surrogate for pathological TT-TG

Objectives. The lack of effective treatment for cartilage defects has prompted investigations using tissue engineering techniques for their regeneration and repair. The success of tissue-engineered repair of cartilage may depend on the rapid and efficient adhesion of transplanted cells to a scaffold. Our aim in this study was to repair full-thickness defects in articular cartilage in the weight-bearing area of a porcine model, and to investigate whether the CD44 monoclonal antibody biotin-avidin (CBA) binding technique could provide satisfactory tissue-engineered cartilage. Methods. Cartilage defects were created in the load-bearing region of the lateral femoral condyle of mini-type pigs. The defects were repaired with traditional tissue-engineered cartilage, tissue-engineered cartilage constructed with the biotin-avidin (BA) technique, tissue-engineered cartilage constructed with the CBA technique and with autologous cartilage. The biomechanical properties, Western blot assay, histological findings and immunohistochemical staining were explored. Results. The CBA group showed similar results to the autologous group in biomechanical properties, Moran’s criteria, histological tests and Wakitani histological scoring. Conclusions. These results suggest that tissue-engineered cartilage constructed using the CBA technique could be used effectively to repair cartilage defects in the weight-bearing area of joints. Cite this article: H. Lin, J. Zhou, L. Cao, H. R. Wang, J. Dong, Z. R. Chen. Tissue-engineered cartilage constructed by a biotin-conjugated anti-CD44 avidin binding technique for the repairing of cartilage defects in the weight-bearing area of knee joints in pigs. Bone Joint Res 2017;6:–295. DOI: 10.1302/2046-3758.65.BJR-2016-0277

Introduction: Mobile bearing total knee arthroplasty (TKA) has been developed to theoretically provide a better, more physiological function of the knee and produce less polyethylene (PE) wear. The theoretical superiority of mobile bearing TKA’s over fixed bearing devices has not yet been proven in clinical studies. The objective of the present study was to analyze in vivo the knee joint kinematics in the sagittal plane in a patient population that had received either a fixed or a mobile TKA in a prospective, randomized, patient- and observer-blinded, clinical study. Methods: 31 patients were evaluated by means of fluoroscopy during unloaded flexion and extension against gravity, as well as during step-up and step-down with full weight bearing. In these 31 patients, 22 fixed bearing TKAs, 16 mobile-bearing TKAs and 19 natural knee joints were included. All patients had been operated in a prospective, randomized, patient- and observer-blinded, clinical study, and had received either fixed or a mobile bearing, cruciate retaining Genesis II TKA for primary osteoarthritis. Fluoroscopic radiographs were evaluated by measuring the „patella tendon angle” as a measure of antero-posterior translation as well as the “kinematic index” as a measure of reproducibility. Results: During unloaded movement, fluoroscopic analysis did not show a significant difference between both types of prosthesis designs and the natural knee. In the weight-bearing movement, both types of TKA designs did not show the typically arched but a more linear patellar tendon angle curve, with a greater angle in extension and in flexion than the natural knees. This means that the femur glides anteriorly under load near extension and does not show the natural roll-back in flexion. In the mobile-bearing group, inter-individual deviations from the mean during weight-bearing movements were significantly less than in the fixed-bearing group. Conclusions: In the present study, no functional advantage of mobile bearing TKA over fixed bearing devices could be found. Both TKA designs showed the typical kinematics of an anterior instability. Long-term follow-ups are necessary to elucidate the possible influence of lower PE wear on the incidence of aseptic loosenings

Osteoarthritis (OA) is the fastest growing global health problem, with a total joint replacement being the only effective treatment for patients with end stage OA. Many groups are examining the use of bone marrow or adipose derived mesenchymal stem cells (MSCs) to repair cartilage, or modulate inflammation to promote healing, however, little efficacy in promoting cartilage repair, or reducing patient symptoms over temporary treatments such as micro-fracture has been observed. There is a growing body of literature demonstrating that MSCs derived from the synovial lining of the joint are superior in terms of chondrogenic differentiation and while improvements in clinical outcome measures have been observed with synovial MSCs, results from clinical studies are still highly variable.

Based on our results, we believe this variability in clinical studies with MSCs results in part from the isolation, expansion and re-injection of distinct MSCs subtypes in normal vs. OA tissues, each with differing regenerating potential. However, it remains unknown if this heterogeneity is natural (e.g. multiple MSC subtypes present) or if MSCs are influenced by factors in vivo (disease state/stage). Therefore, in this study, we undertook an ‘omics’ screening approach on MSCs from normal and OA knee synovial tissue. Specifically, we characterized their global proteome and genomic expression patterns to determine if multiple MSC from normal and OA joints are distinct at the protein/gene expression level and/if so, what proteins/genes are differentially expressed between MSCs derived from normal and OA synovial tissue.

Synovium tissue was collected from OA patients undergoing joint replacement and normal cadaveric knees. The in vitro adipogenic, chondrogenic and osteogenic differentiation potential of the MSCs was analyzed via qPCR and histology. Fully characterized MSC populations where then analyzed through an unbiased shotgun proteomics, and microarray analysis.

Synovial MSCs isolated from both OA and normal knees demonstrated similar multipotent differentiation capacity. Likewise, both OA and normal MSCs display the typical MSCs cell surface marker profile in vitro (CD90+, CD44+, CD73+, CD105+).

Using shotgun proteomics, 7720 unique peptides corresponding to 2183 proteins were identified and quantified between normal and OA MSCs. Of these 2183 proteins, 994 were equally expressed in normal and OA, MSCs, 324 were upregulated in OA MSCs (with 50 proteins exclusively expressed in OA MSCs), 630 proteins were upregulated in normal MSCs (with 16 proteins exclusively expressed in normal MSCs). Microarray analysis of normal and OA MSCs demonstrated a similar result in where, 967 genes were differentially expressed between normal and OA MSCs, with 423 genes upregulated in OA, and 544 genes upregulated in normal MSCs.

In this project, we have demonstrated that although normal and OA synovial derived MSCs demonstrate similar multipotent differentiation potential and cell surface markers expression, these cells demonstrated significant differences at the molecular level (protein and gene expression). Further research is required to determine if these differences influence functional differences in vitro and/or in vivo and what drives this dramatic change in the regulatory pathways within normal vs. OA synovial MSCs.

Abstract

Aims

The aim of this study was to compare robotic arm-assisted bi-unicompartmental knee arthroplasty (bi-UKA) with conventional mechanically aligned total knee arthroplasty (TKA) in order to determine the changes in the anatomy of the knee and alignment of the lower limb following surgery.

Aims

The aim of this consensus was to develop a definition of post-operative fibrosis of the knee.

Aims: In some severe lower limb injuries, the level of bone trauma enables preservation of knee joint only if the soft tissues can be reconstructed over the exposed bone. The options for soft-tissue reconstruction of an amputation stump are to use a ßap from the amputated distal part, a local ßap possibly after tissue expansion or a free ßap. Methods: To preserve an adequate length of stump we reconstructed 10 stumps with latissimus dorsi free ßaps: above the knee in one and below the knee in nine. The reconstructions were done during the acute post-traumaic phase in þve and for late problems with the stump in four patients. In one patient the reconstruction was done nine weeks after a below-knee amputation for ischaemic necrosis after septicaemia. Results: All ßaps survived, but the venous anastomosis had to be revised in three patients in the early post-operative period. All patients regained adequate ambulation for their daily activities. The ßap was secondarily debulked in three patients. Conclusions: Every effort should be made to preserve an adequate stump length, particularly in young patients with crushing injuries of the extremities and when there is severe or recurrent late stump ulceration. A latissimus dorsi musculocunaeous soft-tissue reconstruction is reliable and durable option for stump defects

Deterioration in knee joint proprioception has been postulated to occur following injury, resulting in further instability due to disruption of receptors and feedback mechanisms. Surgical reconstruction techniques may also influence post-operative proprioceptive ability (PA). We hypothesised that anterior cruciate ligament (ACL) reconstruction techniques which disrupt the knee capsule would result in a decrease in PA. Following ethical approval, a total of 48 subjects (mean age: 28.1 ± 10.5, 34 male, 14 female) undergoing ACL reconstruction surgery were included in the study. Fifteen subjects underwent “open” capsule ACL surgery and patellar tendon graft, whereas 33 subjects had “closed” capsule surgery with a hamstring tendon graft. Knee proprioception was measured on a custom-designed test apparatus incorporating electromagnetic position sensors (Polhemus Fastrack) located on femoral and tibial landmarks to accurately track knee angle during flexion-extension (no load). Leg flexion-extension under partial weight-bearing (5kg) was also evaluated. Pre-operative PA was assessed bilaterally, and then again on operated joints at three, six and twelve months post-op. Proprioceptive ability was measured as the cumulative absolute error in knee angle (°) between five repeat measurements and a target angle. We observed no significant difference in PA between injured and contralateral knees prior to ACL reconstruction. Post-operatively, no significant difference in PA was observed between “open” versus “closed” ACL techniques, irrespective of loading conditions. While trends indicated that PA during knee extension (no load) and leg flexion (partial weight-bearing) improved over the 12 months compared to pre-operative values in closed ACL surgery, these were not significantly different to open ACL results. The proportion of subjects whose PA improved in at least two out of the three post-op evaluations was also similar (approx 50%) across all groups, irrespective of joint loading. The only difference was PA during leg flexion under partial weight bearing, where 27% of open ACL surgery patients showed improvement in two or more follow-up tests, as opposed to 58% of closed ACL surgery patients. We present a method to determine pre- and postoperative PA during knee flexion/extension under no load as well as under partial weight-bearing. We saw no significant difference in PA of the knee under no-load versus load. We also saw no significant difference in postoperative PA following open capsule, patellar tendon graft versus closed capsule, hamstring tendon graft ACL reconstruction technique after 1 year follow-up

Objects: We have studied knee morphology using 3DCT considering the bone cutting surface in Total Knee Arthroplasty (TKA in Japan. Subjects were 50 knees in 49 with knee disorders, consisting of 20 knees in 20 men and 30 knees in 29 women. The age range was 16–77 year old (the mean age 52.2). Method: The image of a patient’s knee joint was taken by three-dimensional perspective imaging device (SIEMENS, ARCADIS) before surgery, and it was structured with the three-dimensional computer software K.G.T, INTAGE Realia Professional to measure the knee joint configuration. In the measured site with assumption of the bone cutting surface of the femur side in TKA, the valgus angle of femur was °to the bone axis and the maximum transverse diameter and the maximum anteroposterior diameter of the external condyle were measured at the femur side 8 mm proximal to the external condyle, and the tibial side was vertical to the bone axis and the maximum anteroposterior diameter of the internal and external condyles were measured at the tibial side 2 mm distal to the interior joint surface. The ratio of the anteroposterior diameter and the transverse diameter was computed by these measurements. Result: The average measurements of the femur were 70.82mm of the transverse diameter, 51.2mm of the anteroposterior diameter, and 0.73 of the ratio of the anteroposterior diameter and the transverse diameter. The average measurements of the tibia were 72.5mm of the transverse diameter, 54.4mm of the anteroposterior diameter of the interior condyle, 46.7mm of the anteroposterior diameter of the exterior condyle, and 0.75 and 0.64 of the ratio of the anteroposterior diameter and the transverse diameter of the interior and exterior condyles, respectively. The measurements of the femur were bigger in any sites of men than women, and the transverse diameter was bigger, the anteroposterior diameter tended to be smaller. The transverse diameter did not clearly correlate with the ratio of the anteroposterior diameter and the transverse diameter at the tibial side, and different correlations were shown between men and women respectively. Discussion: At the femur side, a Japanese knee was flatter than a Westerner’s knee just like the previous reports in Japan. The knee is bigger, the knee tends to become flatter, and men are more likely to have the tendency than women. At the tibia side, there were differences for correlation of the flat level between men and women, and it suggested the potential sex difference. Conclusion: The measurement with 3DCT is easy-to-use, and the variation is small compared to an actual measurement value. We want to put it to use for implant design in references to these measurements for the future

Many patients with proximal tibial, distal femur aggressive benign or malignant bone tumors had been treated with wide resection and reconstruction of the knee joint with a tumor prosthesis or an allograft. Reconstruction of the extensor apparatus, infection, non-union, fracture, high cost and mechanical failure is still a problem. If the patient’s own knee can be preserved while allowing a safe tumor excision, better functional results can be obtained for a long time. We describe a series of 9 patients with juxta-articular giant cell tumor around the knee treated by extended intra-lesional curettage and chemical cauterization . Articular surface was preserved and subchondral bone was reconstructed with autogenous bone graft. Full function of the limb was preserved in all except one patient with a mean follow up of 3 years

In total knee replacement (TKR), neutral mechanical alignment (NMA) is targeted in prosthetic component implantation. A novel implantation approach, referred to as kinematic alignment (KA), has been recently proposed (Eckhoff et al. 2005). This is based on the pre-arthritic lower limb alignment which is reconstructed using suitable image-based techniques, and is claimed to allow better soft-tissue balance (Eckhoff et al. 2005) and restoration of physiological joint function. Patient-specific instrumentation (PSI) introduced in TKR to execute personalized prosthesis component implantation are used for KA. The aim of this study was to report knee kinematics and electromyography (EMG) for a number lower limb muscles from two TKR patient groups, i.e. operated according to NMA via conventional instrumentation, or according to KA via PSI. 20 patients affected by primary gonarthrosis were implanted with a cruciate-retaining fixed-bearing prosthesis with patella resurfacing (Triathlon® by Stryker®, Kalamazoo, MI-USA). 17 of these patients, i.e. 11 operated targeting NMA (group A) via convention instrumentation and 6 targeting KA (group B) via PSI (ShapeMatch® by Stryker®, Kalamazoo, MI-USA), were assessed clinically using the International Knee Society Scoring (IKSS) System and biomechanically at 6-month follow-up. Knee kinematics during stair-climbing, chair-rising and extension-against-gravity was analysed by means of 3D video-fluoroscopy (CAT® Medical System, Monterotondo, Italy) synchronized with 4-channel EMG analysis (EMG Mate, Cometa®, Milan, Italy) of the main knee ad/abductor and flexor/extensor muscles. Knee joint motion was calculated in terms of flex/extension (FE), ad/abduction (AA), and internal/external rotation (IE), together with axial rotation of condyle contact point line (CLR). Postoperative knee and functional IKSS scores in group A were 78±20 and 80±23, worse than in group B, respectively 91±12 and 90±15. Knee motion patterns were much more consistent over patients in group B than A. In both groups, normal ranges were found for FE, IE and AA, the latter being generally smaller than 3°. Average IE ranges in the three motor tasks were respectively 8.2°±3.2°, 10.1°±3.9° and 7.9°±4.0° in group A, and 6.6°±4.0°, 10.5°±2.5° and 11.0°±3.9° in group B. Relevant CLRs were 8.2°±3.2°, 10.2°±3.7° and 8.8°±5.3° in group A, and 7.3°±3.5°, 12.6°±2.6° and 12.5°±4.2° in group B. EMG analysis revealed prolonged activation of the medial/lateral vasti muscles in group A. Such muscle co-contraction was not generally observed in all patients in group B, this perhaps proving more stability in the knee replaced following the KA approach. These results reveal that KA results in better function than NMA in TKR. Though small differences were observed between groups, the higher data consistency and the less prolonged muscle activations detected using KA support indirectly the claim of a more natural knee soft tissue balance. References

Introduction and Objectives: Arthrodesis of the knee is the method that most readily controls septic processes and results in a non-painful, stable knee joint. However, the disadvantages of this technique are shortening of the limb and a loss of joint function. Materials and Methods: We present here our unit’s experience in the use of the Orthofíx ® transport system on the anterior surface to stabilise this type of arthrodesis. We used radiological techniques to evaluate the alignment and coaptation of the surfaces to be arthodesed. We also assessed functional capacity, postoperative patient satisfaction, rate of repeat arthrodesis, consolidation time, and complications associated with this method. Results: According to our results, femorotibial arthrodesis with the bone transport system provides all the advantages of monolateral external fixation while allowing compression of the point of arthrodesis, achieving perfect coaptation, and providing extraordinary rigidity to the mounting. Discussion and Conclusions: As with all other procedures, femorotibial arthrodesis has its complications. The complication directly related to knee arthrodesis is femorotibial non-union, which is correlated with a loss of bone stock, incomplete coaptation, poor alignment of the limb, persistent infection, and inadequate immobilisation. We believe this procedure produces a functional limb with significant relief of pain in most patients

Introduction An approximation of normal knee kinematics after knee replacement may improve knee function and implant fixation and reduce wear of the prosthesis. This study describes the knee joint kinematics after unicondylar knee arthroplasty (UKA) in general, and compares the Miller-Glante (MG, fixed bearing) and Oxford (mobile bearing) implants in particular. Methods Twenty-two knees in 17 patients (11 males, six females, mean age of 69.7 yrars) were randomized into MG (11 knees) or Oxford (11 knees). No clinical complications or signs of loosening were observed. At the one year follow-up, RSA (Radiosterometry) x-rays were taken by using two x-ray tubes positioned at knee level and exposing the knee simultaneously from the side. Four pairs of weight bearing x-ray were obtained at zero degrees, 30°, 60°, 90° of knee flexion, with zero as reference position. Tibial rotation, rollback, translation of tibia-femur contact point, and the bearing movement were analyzed using UmRSA software. Results With the MG implant, the tibia internally rotated 3.0°, 3.0°, and 4.2° respectively at 30°, 60°, and 90° of flexion, while with the Oxford implant, the tibia internally rotated 4.3°, 7.6°, and 9.5° respectively at 30°, 60°, and 90°. No significant difference was found between the two groups (P> 0.05, Repeated-measures ANOVA). The medial femoral condyle moved backward (1.8 and 1.5 mm respectively in MG and Oxford) from zero degrees to 30° of flexion. At 60°, it moved anteriorly in both knees, in MG to 0.9 mm anteriorly and in Oxford to 0.6 mm posteriorly to the reference position. At 90° the condyle moved 4.2 mm (MG) and 0.7 mm (Oxford) anteriorly to the reference position. No significant difference between the groups (P> 0.05). The femur-tibia contact point in MG moved anteriorly 2.8, 5.1, and 3.9 mm, respectively at 30°, 60°, and 90° of flexion, whereas the contact point in Oxford moved posteriorly 2.6, 1.8, 2.4 mm respectively at 30°, 60°, and 90°. A significant difference was found between the groups (P=0.003). The bearing in the Oxford implant moved backward of 2.2, 2.0, and 0.9 mm respectively at 30°, 60°, and 90° of knee flexion. Conclusions The in-vivo weight bearing 3D knee kinematics after UKA with fixed or mobile bearing was described. In MG the medial femoral condyle moved forward with knee flexion, whereas in Oxford it moved backward together with the bearing, which is closer to normal knee kinematics

Objective: The purpose of this study was to investigate whether radiographic scores correlate with histomorphological grading and expression of the hyaluronan receptor splice variant CD44v5 in osteoarthritic synovia, cartilage and synovial fluid. Methods: Synovia and cartilage specimens of 19 patients with osteoarthritis of the knee were histomorphologically evaluated with the Mankin’s score, and expression of CD44v5 was analyzed by immunohistochemistry. For radiographical scoring, weight-bearing radiographs of the knee joint were evaluated according to Kellgren and Ahlback. Levels of soluble CD44v5 in synovial fluids were determined by ELISA. Results: The mean radiological scores according to Kellgren and Ahlback were 3.79 and 3.21, respectively. Histomorphological evaluation of specimens revealed a mean grade of 5.53. There was no correlation between radiographical and histomorphological data. Expression of CD44v5 in synovia and cartilage samples was detected in about 50% of the patients and was restricted to latestage osteoarthritis. The immunohistochemical data obtained from synovia correlated significantly with radiological disease progression (p< 0.05). A highly significant correlation was evident between expression of CD44v5 in synovia and cartilage (p< 0.01). Synovial fluid levels of the soluble receptor form showed no correlation. Conclusion: Overall, this study emphasizes a combination of several independent parameters including radiography, histomorphology, and immunohistochemistry for accurate assessment of osteoarthritic disease progression. In this regard, CD44v5 may be a useful additional marker for late-stage osteoarthritis

Introduction: Megaprosthetic failures around the knee and especially those who are infection-related are difficult to manage. Although most of these cases are effectively managed with a two-stage prosthetic revision, selected cases eventually require sacrifice of the knee joint. The authors present their experience with knee-arthrodesis using a vascularized fibula and allograft reinforcement. Materials and Methods: Between 1998 and 2002, eight patients with failed knee prosthesis were referred for resection-arthrodesis; all patients had at least two previous revision attempts using a spacer or a new implant. Knee-arthrodesis included resection of the distal femur and proximal tibia and reconstruction with a free micro-vascularized fibular graft and allograft reinforcement. Fibular grafts were harvested with a large musculocutaneous flap to facilitate soft-tissue coverage and monitor flap viability. Following surgery, patients were kept non-weight-bearing for 3 months. Radiographs were performed 6 and 12 weeks postoperatively to establish fibular graft incorporation. If healing had progressed satisfactorily, weight-bearing was gradually allowed. Results: At the most recent follow-up’ all eight patients had a stable and painless reconstruction, associated with radiological evidence of solid fibular graft union. The latter was typically observed between 6 to 12 weeks from surgery. Complications included one emergent surgery for anastamotic rupture in one patient and surgical debridement with skin grafting of musculocutaneous flap necrosis in another patient. Conclusions: Knee-arthrodesis using microvascularized fibula and allograft reinforcement is a safe and reliable salvage procedure in end-stage failures of megaprosthetic knee implants

Purpose: Simultaneous high tibial osteotomy (HTO) and anterior cruciate ligament (ACL) reconstruction has been proposed as a treatment for patients with combined medial compartment knee osteoarthritis (OA) and ACL deficiency. Although goals of surgery are to correct malalignment, decrease knee joint load and enable continued participation in sports, few prospective studies evaluating these outcomes exist. Therefore, the objective of this study was to evaluate two-year changes in frontal plane alignment, dynamic knee joint load and self-reported function during sport after simultaneous HTO and ACL reconstruction. Method: Thirty patients with varus alignment, medial compartment knee OA and ACL deficiency have undergone medial opening wedge HTO and hamstring tendon ACL reconstruction during a single operation. Full-length, standing AP radiographs (mechanical axis angle), dynamic knee joint loads (the peak external adduction moment about the knee during self-paced walking) and the Knee Injury and Osteoarthritis Outcome Scale (KOOS) were completed before and 24 months after surgery. Results: Based on the 14 patients currently at 24.9 ± 1.67 months postop (12 males; age = 38.5 ± 7.5 yrs.; BMI = 29.5 ± 5.6, median Kellgren and Lawrence grade = 2), mechanical axis angle decreased significantly (p< 0.005) from −6.2 ± 3.63° to 0.29±1.94°. Despite a small (0.06 ± 0.10m/s), but significant (p< 0.05), increase in self-paced walking speed after surgery, the peak knee adduction moment decreased significantly (p < 0.001) from 2.96 ± 0.61 %BW*ht to 1.58 ± 0.48 %BW*ht [mean decrease = 1.38 %BW*ht (95% CI: 0.87 – 1.89)]. Each domain of the KOOS also improved significantly (p< 0.05), with the mean sports and recreation domain increasing (p=0.001) from 26.92 ± 24.29 to 66.54 ± 28.09 [mean increase = 39.62 (95% CI: 20.09 – 51.14)]. Data from 30 patients will be available at time of presentation. Conclusion: Two-year outcomes after simultaneous medial opening wedge HTO and ACL reconstruction suggest this treatment results in substantial improvements in alignment, knee joint load and self-reported functioning during sport

Computer Assisted Surgery (CAS) and Patient Specific Instrumentation (PSI) have been reported to increase accuracy and predictability of tumour resections. The technically demanding joint-preserving surgery that retains the native joint with the better function may benefit from the new techniques. This cadaver study is to investigate the surgical accuracy of CAS and PSI in joint-preserving surgery of knee joint. CT scans of four cadavers were performed and imported into an engineering software (MIMICS, Materialise) for the 3D surgical planning of simulated, multiplanar joint-preserving resections for distal femur or proximal tibia metaphyseal bone sarcoma. The planned resections were transferred to the navigation system (OrthoMap 3D, Stryker) for navigation planning and used for the design and fabrication of the PSI. Each of the four techniques (freehand, CAS, PSI and CAS + PSI) was used in four joint-preserving resections. Location accuracy (the maximum deviation of distance between the planned and the achieved resections) and bone resection time were measured. The results were compared by using t-test (statistically significant if P< 0.05). Both the CAS+PSI and PSI techniques could reproduce the planned resections with a mean location accuracy of < 2 mm, compared to 3.6 mm for CAS assistance and 9.2 mm for the freehand technique. There was no statistical difference in location accuracy between the CAS+PSI and the PSI techniques (p=0.92) but a significant difference between the CAS technique and the CAS+PSI (p=0.042) or PSI technique (p=0.034) and the freehand technique with the other assisted techniques. The PSI technique took the lowest mean time of 4.78 ±0.97min for bone resections. This was significantly different from the CAS+PSI technique (mean 12.78 min; p < 0.001) and the CAS technique (mean 16.97 min; p = < 0.001). CAS and PSI assisted techniques help reproduce the planned multiplanar resections. The PSI technique could achieve the most accurate bone resections (within 2mm error) with the least time for bone resections. Combining CAS with PSI might not improve surgical accuracy and might increase bone resection time. However, PSI placement on the bone surface depends only on the subjective feeling of surgeons and may not apply if the extraosseous tumor component is large. Combining CAS with PSI could address the limitations

The peak external knee adduction moment during walking gait has been proposed to be a clinically useful measure of dynamic knee joint load in patients with knee osteoarthritis. However, there is limited information about the reliability of this measure, or its ability to detect change. The test-retest reliability and sensitivity to change of peak knee adduction moments were evaluated in thirty patients with varus gonarthrosis. Indices of relative and absolute reliability were excellent (intra-class correlation coefficient = 0.85, standard error of measurement = 0.36 % BW*Ht), and the sensitivity to change following high tibial osteotomy was high (standardized response mean = 1.2). To estimate the test-retest reliability, measurement error and sensitivity to change of the peak knee adduction moment during gait. Thirty patients (44”11 yrs, 1.7”0.09 m, 87”20 kg, twenty males, ten females) with varus gonarthrosis underwent gait analyses on two pre-operative test occasions within one week, and on a third test occasion six months after medial opening wedge high tibial osteotomy. Three-dimensional kinematic and kinetic gait data were collected during self-paced walking and used to calculate the peak knee adduction moment. An intraclass correlation coefficient of 0.85 (95%CI: 0.71, 0.93) indicated excellent relative reliability, and a standard error of measurement of 0.36 %BW*Ht (95%CI: 0.29, 0.49) indicated low measurement error. The peak knee adduction moment after surgery (1.66”0.72 %BW*Ht) was significantly (p< 0.001) lower than before surgery (2.58”0.72 %BW*Ht). A standardized response mean of 1.2 (95%CI: 0.77, 1.6) indicated the size of this change was large. Based on 95% confidence levels, these results suggest the error in an individual’s peak knee adduction moment at one point in time is 0.70 % BW*Ht, the minimal detectable change in an individual’s peak adduction moment is 1.0 %BW*Ht, and it is sensitive to change following treatment. The peak knee adduction moment during gait has appropriate reliability for use in studies evaluating the effect of treatments intended to decrease the load on the knee. When considering measurement error, the knee adduction moment is also appropriate for clinical use in evaluating change in individual patients. Funding: CIHR, Arthrex Inc

Aim The aim of this study was to identify the presentation, management and outcomes this rare disease using the large series of patients treated at our unit. Material and Methods We reviewed the medical records and x-rays of all the patients who were referred – treated for PVNS around the knee joint between 1990 and 2002. Results 42 patients totally were treated or had second opinion for PVNS disease. 37 have been analysed in detail. Their mean age was 33 years old and 11 patients were below 17 years of age. There was a predilection for females with 22 (59.5%) out of 37 patients. There was average 3.3 years period of time with swelling/knee symptoms before diagnosis . The MRI scan was the cornerstone for the patient’s assessment. It has proved useful in recurrent disease and posterior ”Bakers cyst” disease. 2 of the patients had been managed with arthroscopic synovectomy alone, 10 patients have undergone simultaneous arthroscopic synovectomy combined with open excision of any “Bakers cyst” disease. 10 had “open synovectomy”. 3 patients have had radiotherapy .3 patients have had TKR Complications included 3 superficial wound infections, 1 DVT, 1 PE, 1 stress fracture after radical bone curettage, common temporary/refractory stiffness (needing physio/ MUAs). Recurrence was high and managed with repeat arthroscopic synovectomy. Conclusion PVNS is a rare disorder with typical mono-articular involvement affecting most commonly the knee joint. MRI and biopsy is the gold standard for the establishment of diagnosis and often needs a combined approach with arthroscopic and open posterior cyst excision. Radiotherapy is helpful in aggressive cases. TKR is suggested when there is associated articular erosion. The patient should be warned about the long course of treatment and often multiple procedures because of high recurrence rates

Although cartilage repair has been around since the time of open Pridie drilling, clinical outcomes for newer techniques such as arthroscopic debridement, microfracture (MFX), osteochondral autograft transfers (OATS), osteochondral allograft transplantation and Autologous Chondrocyte Implantation (ACI) are still finding their place in treating injured knees.

Early mechanical symptoms are best managed by a gentle arthroscopic debridement of loose articular flaps. This allows the surgeon to assess the defect size, location in the tibio-femoral or patellofemoral joint, status of the cartilage overall and patients response to the intervention. If the symptom improvement is not satisfactory to the patient, after assessing background factors that will influence the results of a cartilage repair procedure, (alignment of the patellofemoral joint or axial alignment, ligament stability and status of the meniscus), the surgeon can choose the best procedure for that individual based on the expected outcomes of the various cartilage repair techniques while addressing the background factors. As all the techniques have failures and informed discussion with the patient prior to performing the procedure is critical in avoiding disappointment for the patient and the surgeon.

The repair technique used should incorporate considerations of the defect size, location, and the patient age, activity level, expectations and ability to comply with the longer rehabilitation needed for biological procedures as compared to prosthetic implants.